Nucleic acid and amino acid sequences relating to Staphylococcus
epidermidis for diagnostics and therapeutics
United States Patent: 7,566,776
Issued: July 28, 2009
Lynn (Framingham, MA), Bush; David (Somerville, MA)
Assignee: Wyeth (Madison,
Appl. No.: 11/882,810
Filed: August 6, 2007
The invention provides isolated
polypeptide and nucleic acid sequences derived from Staphylococcus
epidermidis that are useful in diagnosis and therapy of pathological
conditions; antibodies against the polypeptides; and methods for the
production of the polypeptides. The invention also provides methods for
the detection, prevention and treatment of pathological conditions
resulting from bacterial infection.
Description of the
The sequences of the present
invention include the specific nucleic acid and amino acid sequences set
forth in the Sequence Listing that forms a part of the present
specification, and which are designated SEQ ID NO: 1-SEQ ID NO: 5674. Use of
the terms "SEQ ID NO: 1-SEQ ID NO: 2837," "SEQ ID NO: 2838-SEQ ID NO: 5674,"
and "the sequences depicted in Table 2 (see Original Patent)", etc., is
intended, for convenience, to refer to each individual SEQ ID NO
individually, and is not intended to refer to the genus of these sequences.
In other words, it is a shorthand for listing all of these sequences
individually. The invention encompasses each sequence individually, as well
as any combination thereof.
S. epidermidis Genomic Sequence
This invention provides nucleotide sequences of the genome of S. epidermidis
which thus comprises a DNA sequence library of S. epidermidis genomic DNA.
The detailed description that follows provides nucleotide sequences of S.
epidermidis, and also describes how the sequences were obtained and how ORFs
and protein-coding sequences were identified. Also described are methods of
using the disclosed S. epidermidis sequences in methods including diagnostic
and therapeutic applications. Furthermore, the library can be used as a
database for identification and comparison of medically important sequences
in this and other strains of S. epidermidis.
To determine the genomic sequence of S. epidermidis DNA from strain 18972 of
S. epidermidis was isolated after Zymolyase digestion, sodium dodecyl
sulfate lysis, potassium acetate precipitation, phenol:chloroform extraction
and ethanol precipitation (Soll, D. R., T. Srikantha and S. R. Lockhart:
Characterizing Developmentally Regulated Genes in S. epidermidis. In
Microbial Genome Methods. K. W. Adolph, editor. CRC Press. New York. p
17-37.). DNA was sheared hydrodynamically using an HPLC (Oefner, et. al.,
1996) to an insert size of 2000-3000 bp. After size fractionation by gel
electrophoresis the fragments were blunt-ended, ligated to adapter
oligonucleotides and cloned into the pGTC (Thomann) vector to construct a
"shotgun" subclone library
DNA sequencing was achieved using established ABI sequencing methods on
ABI377 automated DNA sequencers. The cloning and sequencing procedures are
described in more detail in the Exemplification.
Individual sequence reads were assembled using PHRAP (P. Green, Abstracts of
DOE Human Genome Program Contractor-Grantee Workshop V, January 1996, p.
157). The average contig length was about 3-4 kb.
All subsequent steps were based on sequencing by ABI377 automated DNA
sequencing methods. The cloning and sequencing procedures are described in
more detail in the Exemplification.
A variety of approaches are used to order the contigs so as to obtain a
continuous sequence representing the entire S. epidermidis genome. Synthetic
oligonucleotides are designed that are complementary to sequences at the end
of each contig. These oligonucleotides may be hybridized to libraries of S.
epidermidis genomic DNA in, for example, lambda phage vectors or plasmid
vectors to identify clones that contain sequences corresponding to the
junctional regions between individual contigs. Such clones are then used to
isolate template DNA and the same oligonucleotides are used as primers in
polymerase chain reaction (PCR) to amplify junctional fragments, the
nucleotide sequence of which is then determined.
The S. epidermidis sequences were analyzed for the presence of open reading
frames (ORFs) comprising at least 180 nucleotides. As a result of the
analysis of ORFs based on stop-to-stop codon reads, it should be understood
that these ORFs may not correspond to the ORF of a naturally-occurring S.
epidermidis polypeptide. These ORFs may contain start codons which indicate
the initiation of protein synthesis of a naturally-occurring S. epidermidis
polypeptide. Such start codons within the ORFs provided herein were
identified by those of ordinary skill in the relevant art, and the resulting
ORF and the encoded S. epidermidis polypeptide is within the scope of this
invention. For example, within the ORFs a codon such as AUG or GUG (encoding
methionine or valine) which is part of the initiation signal for protein
synthesis were identified and the portion of an ORF to corresponding to a
naturally-occurring S. epidermidis polypeptide was recognized. The predicted
coding regions were defined by evaluating the coding potential of such
sequences with the program GENEMARK.TM. (Borodovsky and McIninch, 1993,
Each predicted ORF amino acid sequence was compared with all sequences found
in current GENBANK, SWISS-PROT, and PIR databases using the BLAST algorithm.
BLAST identifies local alignments occurring by chance between the ORF
sequence and the sequence in the databank (Altschal et al., 1990, L Mol.
Biol. 215:403-410). Homologous ORFs (probabilities less than 10.sup.-5 by
chance) and ORF's that are probably non-homologous (probabilities greater
than 10.sup.-5 by chance) but have good codon usage were identified. Both
homologous, sequences and non-homologous sequences with good codon usage,
are likely to encode proteins and are encompassed by the invention.
S. epidermidis Nucleic Acids
The present invention provides a library of S. epidermidis-derived nucleic
acid sequences. The libraries provide probes, primers, and markers which are
used as markers in epidemiological studies. The present invention also
provides a library of S. epidermidis-derived nucleic acid sequences which
comprise or encode targets for therapeutic drugs.
The nucleic acids of this invention may be obtained directly from the DNA of
the above referenced S. epidermidis strain by using the polymerase chain
reaction (PCR). See "PCR, A Practical Approach" (McPherson, Quirke, and
Taylor, eds., IRL Press, Oxford, UK, 1991) for details about the PCR. High
fidelity PCR is used to ensure a faithful DNA copy prior to expression. In
addition, the authenticity of amplified products is verified by conventional
sequencing methods. Clones carrying the desired sequences described in this
invention may also be obtained by screening the libraries by means of the
PCR or by hybridization of synthetic oligonucleotide probes to filter lifts
of the library colonies or plaques as known in the art (see, e.g., Sambrook
et al., Molecular Cloning, A Laboratoly Manual 2nd edition, 1989, Cold
Spring Harbor Press, NY).
It is also possible to obtain nucleic acids encoding S. epidermidis
polypeptides from a cDNA library in accordance with protocols herein
described. A cDNA encoding a S. epidermidis polypeptide can be obtained by
isolating total mRNA from an appropriate strain. Double stranded cDNAs can
then be prepared from the total mRNA. Subsequently, the cDNAs can be
inserted into a suitable plasmid or viral (e.g., bacteriophage) vector using
any one of a number of known techniques. Genes encoding S. epidermidis
polypeptides can also be cloned using established polymerase chain reaction
techniques in accordance with the nucleotide sequence information provided
by the invention. The nucleic acids of the invention can be DNA or RNA.
Preferred nucleic acids of the invention are contained in the Sequence
The nucleic acids of the invention can also be chemically synthesized using
standard techniques. Various methods of chemically synthesizing
polydeoxynucleotides are known, including solid-phase synthesis which, like
peptide synthesis, has been fully automated in commercially available DNA
synthesizers (See e.g., Itakura et al. U.S. Pat. No. 4,598,049; Caruthers et
al. U.S. Pat. No. 4,458,066; and Itakura U.S. Pat. Nos. 4,401,796 and
4,373,071, incorporated by reference herein).
In another example, DNA can be chemically synthesized using, e.g., the
phosphoramidite solid support method of Matteucci et al., 1981, J. Am. Chem.
Soc. 103:3185, the method of Yoo et al., 1989, J. Biol. Chem. 764:17078, or
other well known methods. This can be done by sequentially linking a series
of oligonucleotide cassettes comprising pairs of synthetic oligonucleotides,
as described below.
Nucleic acids isolated or synthesized in accordance with features of the
present invention are useful, by way of example, without limitation, as
probes, primers, capture ligands, antisense genes and for developing
expression systems for the synthesis of proteins and peptides corresponding
to such sequences. As probes, primers, capture ligands and antisense agents,
the nucleic acid normally consists of all or part (approximately twenty or
more nucleotides for specificity as well as the ability to form stable
hybridization products) of the nucleic acids of the invention contained in
the Sequence Listing. These uses are described in further detail below.
A nucleic acid isolated or synthesized in accordance with the sequence of
the invention contained in the Sequence Listing can be used as a probe to
specifically detect S. epidermidis. With the sequence information set forth
in the present application, sequences of twenty or more nucleotides are
identified which provide the desired inclusivity and exclusivity with
respect to S. epidermidis, and extraneous nucleic acids likely to be
encountered during hybridization conditions. More preferably, the sequence
will comprise at least twenty to thirty nucleotides to convey stability to
the hybridization product formed between the probe and the intended target
Sequences larger than 1000 nucleotides in length are difficult to synthesize
but can be generated by recombinant DNA techniques. Individuals skilled in
the art will readily recognize that the nucleic acids, for use as probes,
can be provided with a label to facilitate detection of a hybridization
Nucleic acid isolated and synthesized in accordance with the sequence of the
invention contained in the Sequence Listing can also be useful as probes to
detect homologous regions (especially homologous genes) of other
Staphylococcus species using appropriate stringency hybridization conditions
as described herein.
For use as a capture ligand, the nucleic acid selected in the manner
described above with respect to probes, can be readily associated with a
support. The manner in which nucleic acid is associated with supports is
well known. Nucleic acid having twenty or more nucleotides in a sequence of
the invention contained in the Sequence Listing have utility to separate S.
epidermidis nucleic acid from one strain from the nucleic acid of other
another strain as well as from other organisms. Nucleic acid having twenty
or more nucleotides in a sequence of the invention contained in the Sequence
Listing can also have utility to separate other Staphylococcus species from
each other and from other organisms. Preferably, the sequence will comprise
at least twenty nucleotides to convey stability to the hybridization product
formed between the probe and the intended target molecules. Sequences larger
than 1000 nucleotides in length are difficult to synthesize but can be
generated by recombinant DNA techniques.
Nucleic acid isolated or synthesized in accordance with the sequences
described herein have utility as primers for the amplification of S.
epidermidis nucleic acid. These nucleic acids may also have utility as
primers for the amplification of nucleic acids in other Staphylococcus
species. With respect to polymerase chain reaction (PCR) techniques, nucleic
acid sequences of .gtoreq.10-15 nucleotides of the invention contained in
the Sequence Listing have utility in conjunction with suitable enzymes and
reagents to create copies of S. epidermidis nucleic acid. More preferably,
the sequence will comprise twenty or more nucleotides to convey stability to
the hybridization product formed between the primer and the intended target
molecules. Binding conditions of primers greater than 100 nucleotides are
more difficult to control to obtain specificity. High fidelity PCR can be
used to ensure a faithful DNA copy prior to expression. In addition,
amplified products can be checked by conventional sequencing methods.
The copies can be used in diagnostic assays to detect specific sequences,
including genes from S. epidermidis and/or other Staphylococcus species. The
copies can also be incorporated into cloning and expression vectors to
generate polypeptides corresponding to the nucleic acid synthesized by PCR,
as is described in greater detail herein.
The nucleic acids of the present invention find use as templates for the
recombinant production of S. epidermidis-derived peptides or polypeptides
Nucleic acid or nucleic acid-hybridizing derivatives isolated or synthesized
in accordance with the sequences described herein have utility as antisense
agents to prevent the expression of S. epidermidis genes. These sequences
also have utility as antisense agents to prevent expression of genes of
other Staphylococcus species.
In one embodiment, nucleic acid or derivatives corresponding to S.
epidermidis nucleic acids is loaded into a suitable carrier such as a
liposome or bacteriophage for introduction into bacterial cells. For
example, a nucleic acid having twenty or more nucleotides is capable of
binding to bacteria nucleic acid or bacteria messenger RNA. Preferably, the
antisense nucleic acid is comprised of 20 or more nucleotides to provide
necessary stability of a hybridization product of non-naturally occurring
nucleic acid and bacterial nucleic acid and/or bacterial messenger RNA.
Nucleic acid having a sequence greater than 1000 nucleotides in length is
difficult to synthesize but can be generated by recombinant DNA techniques.
Methods for loading antisense nucleic acid in liposomes is known in the art
as exemplified by U.S. Pat. No. 4,241,046 issued Dec. 23, 1980 to
Papahadjopoulos et al.
The present invention encompasses isolated polypeptides and nucleic acids
derived from S. epidermidis that are useful as reagents for diagnosis of
bacterial infection, components of effective anti-bacterial vaccines, and/or
as targets for anti-bacterial drugs, including anti-S. epidermidis drugs.
Expression of S. epidermidis Nucleic Acids
Table 2 (see Original Patent), which is appended herewith and which forms
part of the present specification, provides a list of open reading frames (ORFs)
in both strands and a putative identification of the particular function of
a polypeptide which is encoded by each ORF, based on the homology match
(determined by the BLAST algorithm) of the predicted polypeptide with known
proteins encoded by ORFs in other organisms. An ORF is a region of nucleic
acid which encodes a polypeptide. This region may represent a portion of a
coding sequence or a total sequence and was determined from stop to stop
codons. The first column contains a designation for the contig from which
each ORF was identified (numbered arbitrarily). Each contig represents a
continuous stretch of the genomic sequence of the organism. The second
column lists the ORF designation. The third and fourth columns list the SEQ
ID numbers for the nucleic acid and amino acid sequences corresponding to
each ORF, respectively. The fifth and sixth columns list the length of the
nucleic acid and the length of the amino acid, respectively. The nucleotide
sequence corresponding to each ORF designation begins at the first
nucleotide immediately following a stop codon and ends at the nucleotide
immediately preceding the next downstream stop codon in the same reading
frame. It will be recognized by one skilled in the art that the natural
translation initiation sites will correspond to ATG, GTG, or TTG codons
located within the ORFs. The natural initiation sites depend not only on the
sequence of a start codon but also on the context of the DNA sequence
adjacent to the start codon. Usually, a recognizable ribosome binding site
is found within 20 nucleotides upstream from the initiation codon. In some
cases where genes are translationally coupled and coordinately expressed
together in "operons", ribosome binding sites are not present, but the
initiation codon of a downstream gene may occur very close to, or overlap,
the stop codon of the an upstream gene in the same operon. The correct start
codons can be generally identified without undue experimentation because
only a few codons need be tested. It is recognized that the translational
machinery in bacteria initiates all polypeptide chains with the amino acid
methionine, regardless of the sequence of the start codon. In some cases,
polypeptides are post-translationally modified, resulting in an N-terminal
amino acid other than methionine in vivo. The seventh and eighth columns
provide metrics for assessing the likelihood of the homology match
(determined by the BLASTP2 algorithm), as is known in the art, to the genes
indicated in the eleventh column when the designated ORF was compared
against a non-redundant comprehensive protein database. Specifically, the
seventh column represents the "Blast Score" for the match (a higher score is
a better match), and the eighth column represents the "P-value" for the
match (the probability that such a match can have occurred by chance; the
lower the value, the more likely the match is valid). If a BLASTP2 score of
less than 46 was obtained, no value is reported in the table the "P-value".
Column nine, Subject Taxonomy," provides the name of the organism that was
identified as having the closest homology match. The tenth column, "Subject
Name," provides where available, either a public database accession number
or our own sequence name. The eleventh column provides, where available, the
Swissprot accession number (SP), the locus name (LN), the Organism (OR),
Source of variant (SR), E. C. number (EC), the gene name (GN), the product
name (PN), the Function Description (FN), Left End (LE), Right End (RE),
Coding Direction (DI), and the description (DE) or notes (NT) for each ORF.
Information that is not preceded by a code designation in the eleventh
column represents a description of the ORF. This information allows one of
ordinary skill in the art to determine a potential use for each identified
coding sequence and, as a result, allows use of the polypeptides of the
present invention for commercial and industrial purposes.
Using the information provided in SEQ ID NO: 1-SEQ ID NO: 2837 and in Table
2 together with routine cloning and sequencing methods, one of ordinary
skill in the art will be able to clone and sequence all the nucleic acid
fragments of interest including open reading frames (ORFs) encoding a large
variety proteins of S. epidermidis.
Nucleic acid isolated or synthesized in accordance with the sequences
described herein have utility to generate polypeptides. The nucleic acid of
the invention exemplified in SEQ ID NO: 1-SEQ ID NO: 2837 and in Table 2 or
fragments of said nucleic acid encoding active portions of S. epidermidis
polypeptides can be cloned into suitable vectors or used to isolate nucleic
acid. The isolated nucleic acid is combined with suitable DNA linkers and
cloned into a suitable vector.
The function of a specific gene or operon can be ascertained by expression
in a bacterial strain under conditions where the activity of the gene
product(s) specified by the gene or operon in question can be specifically
measured. Alternatively, a gene product may be produced in large quantities
in an expressing strain for use as an antigen, an industrial reagent, for
structural studies, etc. This expression can be accomplished in a mutant
strain which lacks the activity of the gene to be tested, or in a strain
that does not produce the same gene product(s). This includes, but is not
limited to, Eucaryotic species such as the yeast Saccharomyces cerevisiae,
Methanobacterium strains or other Archaea, and Eubacteria such as E. coli,
B. Subtilis, S. Aureus, S. Pneumonia or Pseudomonas; putida. In some cases
the expression host will utilize the natural S. epidermidis promoter whereas
in others, it will be necessary to drive the gene with a promoter sequence
derived from the expressing organism (e.g., an E. coli beta-galactosidase
promoter for expression in E. coli).
To express a gene product using the natural S. epidermidis promoter, a
procedure such as the following can be used. A restriction fragment
containing the gene of interest, together with its associated natural
promoter element and regulatory sequences (identified using the DNA sequence
data) is cloned into an appropriate recombinant plasmid containing an origin
of replication that functions in the host organism and an appropriate
selectable marker. This can be accomplished by a number of procedures known
to those skilled in the art. It is most preferably done by cutting the
plasmid and the fragment to be cloned with the same restriction enzyme to
produce compatible ends that can be ligated to join the two pieces together.
The recombinant plasmid is introduced into the host organism by, for
example, electroporation and cells containing the recombinant, plasmid are
identified by selection for the marker on the plasmid. Expression of the
desired gene product is detected using an assay specific for that gene
In the case of a gene that requires a different promoter, the body of the
gene (coding sequence) is specifically excised and cloned into an
appropriate expression plasmid. This subcloning can be done by several
methods, but is most easily accomplished by PCR amplification of a specific
fragment and ligation into an expression plasmid after treating the PCR
product with a restriction enzyme or exonuclease to create suitable ends for
A suitable host cell for expression of a gene can be any procaryotic or
eucaryotic cell. Suitable methods for transforming host cells can be found
in Sambrook et al. (Molecular Cloning: A Laboratory Manual, 2nd Edition,
Cold Spring Harbor Laboratory press (1989)), and other laboratory textbooks.
For example, a host cell transfected with a nucleic acid vector directing
expression of a nucleotide sequence encoding a S. epidermidis polypeptide
can be cultured under appropriate conditions to allow expression of the
polypeptide to occur. Suitable media for cell culture are well known in the
art. Polypeptides of the invention can be isolated from cell culture medium,
host cells, or both using techniques known in the art for purifying proteins
including ion-exchange chromatography, gel filtration chromatography,
ultrafiltration, electrophoresis, and immunoaffinity purification with
antibodies specific for such polypeptides. Additionally, in many situations,
polypeptides can be produced by chemical cleavage of a native protein (e.g.,
tryptic digestion) and the cleavage products can then be purified by
In the case of membrane bound proteins, these can be isolated from a host
cell by contacting a membrane-associated protein fraction with a detergent
forming a solubilized complex, where the membrane-associated protein is no
longer entirely embedded in the membrane fraction and is solubilized at
least to an extent which allows it to be chromatographically isolated from
the membrane fraction. Chromatographic techniques which can be used in the
final purification step are known in the art and include hydrophobic
interaction, lectin affinity, ion exchange, dye affinity and immunoaffinity.
One strategy to maximize recombinant S. epidermidis peptide expression in E.
coli is to express the protein in a host bacteria with an impaired capacity
to proteolytically cleave the recombinant protein (Gottesman, S., Gene
Expression Technology: Methods in Enzymology 185, Academic Press, San Diego,
Calif. (1990) 119-128). Another strategy would be to alter the nucleic acid
encoding a S. epidermidis peptide to be inserted into an expression vector
so that the individual codons for each amino acid would be those
preferentially utilized in highly expressed E. coli proteins (Wada et al.,
(1992) Nuc. Acids Res. 20:2111-2118). Such alteration of nucleic acids of
the invention can be carried out by standard DNA synthesis techniques.
The nucleic acids of the invention can also be chemically synthesized using
standard techniques. Various methods of chemically synthesizing
polydeoxynucleotides are known, including solid-phase synthesis which, like
peptide synthesis, has been fully automated in commercially available DNA
synthesizers (See, e.g., Italura et al. U.S. Pat. No. 4,598,049; Caruthers
et al. U.S. Pat. No. 4,458,066; and Itakura U.S. Pat. Nos. 4,401,796 and
4,373,071, incorporated by reference herein).
The present invention provides a library of S. epidermidis-derived nucleic
acid sequences. The libraries provide probes, primers, and markers which can
be used as markers in epidemiological studies. The present invention also
provides a library of S. epidermidis-derived nucleic acid sequences which
comprise or encode targets for therapeutic drugs.
Nucleic acids comprising any of the sequences disclosed herein or
sub-sequences thereof can be prepared by standard methods using the nucleic
acid sequence information provided in SEQ ID NO: 1-SEQ ID NO: 2837. For
example, DNA can be chemically synthesized using, e.g., the phosphoramidite
solid support method of Matteucci et al., 1981, J. Am. Chem. Soc. 103:3185,
the method of Yoo et al., 1989, J. Biol. Chem. 764:17078, or other well
known methods. This can be done by sequentially linking a series of
oligonucleotide cassettes comprising pairs of synthetic oligonucleotides, as
Of course, due to the degeneracy of the genetic code, many different
nucleotide sequences can encode polypeptides having the amino acid sequences
defined by SEQ ID NO: 2838-SEQ ID NO: 5674 or sub-sequences thereof. The
codons can be selected for optimal expression in prokaryotic or eukaryotic
systems. Such degenerate variants are also encompassed by this invention.
Insertion of nucleic acids (typically DNAs) encoding the polypeptides of the
invention into a vector is easily accomplished when the termini of both the
DNAs and the vector comprise compatible restriction sites. If this cannot be
done, it may be necessary to modify the termini of the DNAs and/or vector by
digesting back single-stranded DNA overhangs generated by restriction
endonuclease cleavage to produce blunt ends, or to achieve the same result
by filling in the single-stranded termini with an appropriate DNA
Alternatively, any site desired may be produced, e.g., by ligating
nucleotide sequences (linkers) onto the termini. Such linkers may comprise
specific oligonucleotide sequences that define desired restriction sites.
Restriction sites can also be generated by the use of the polymerase chain
reaction (PCR). See, e.g., Saiki et al., 1988, Science 239:48. The cleaved
vector and the DNA fragments may also be modified if required by
The nucleic acids of the invention may be isolated directly from cells.
Alternatively, the polymerase chain reaction (PCR) method can be used to
produce the nucleic acids of the invention, using either chemically
synthesized strands or genomic material as templates. Primers used for PCR
can be synthesized using the sequence information provided herein and can
further be designed to introduce appropriate new restriction sites, if
desirable, to facilitate incorporation into a given vector for recombinant
The nucleic acids of the present invention may be flanked by natural S.
epidermidis regulatory sequences, or may be associated with heterologous
sequences, including promoters, enhancers, response elements, signal
sequences, polyadenylation sequences, introns, 5'- and 3'-noncoding regions,
and the like. The nucleic acids may also be modified by many means known in
the art. Non-limiting examples of such modifications include methylation,
"caps", substitution of one or more of the naturally occurring nucleotides
with an analog, internucleotide modifications such as, for example, those
with uncharged linkages (e.g., methyl phosphonates, phosphotriesters,
phosphoroamidates, carbamates, etc.) and with charged linkages (e.g.,
phosphorothioates, phosphorodithioates, etc.). Nucleic acids may contain one
or more additional covalently linked moieties, such as, for example,
proteins (e.g., nucleases, toxins, antibodies, signal peptides,
poly-L-lysine, etc.), intercalators (e.g., acridine, psoralen, etc.),
chelators (e.g., metals, radioactive metals, iron, oxidative metals, etc.),
and alkylators. PNAs are also included. The nucleic acid may be derivatized
by formation of a methyl or ethyl phosphotriester or an alkyl
phosphoramidate linkage. Furthermore, the nucleic acid sequences of the
present invention may also be modified with a label capable of providing a
detectable signal, either directly or indirectly. Exemplary labels include
radioisotopes, fluorescent molecules, biotin, and the like.
The invention also provides nucleic acid vectors comprising the disclosed S.
epidermidis-derived sequences or derivatives or fragments thereof. A large
number of vectors, including plasmid and bacterial vectors, have been
described for replication and/or expression in a variety of eukaryotic and
prokaryotic hosts, and may be used for cloning or protein expression.
The encoded S. epidermidis polypeptides may be expressed by using many known
vectors, such as pUC plasmids, pET plasmids (Novagen, Inc., Madison, Wis.),
or pRSET or pREP (Invitrogen, San Diego, Calif.), and many appropriate host
cells, using methods disclosed or cited herein or otherwise known to those
skilled in the relevant art. The particular choice of vector/host is not
critical to the practice of the invention.
Recombinant cloning vectors will often include one or more replication
systems for cloning or expression, one or more markers for selection in the
host, e.g. antibiotic resistance, and one or more expression cassettes. The
inserted S. epidermidis coding sequences may be synthesized by standard
methods, isolated from natural sources, or prepared as hybrids, etc.
Ligation of the S. epidermidis coding sequences to transcriptional
regulatory elements and/or to other amino acid coding sequences may be
achieved by known methods. Suitable host cells may be transformed/transfected/infected
as appropriate by any suitable method including electroporation, CaCl.sub.2
mediated DNA uptake, bacterial infection, microinjection, microprojectile,
or other established methods.
Appropriate host cells include bacteria, archebacteria, fungi, especially
yeast, and plant and animal cells, especially mammalian cells. Of particular
interest are S. epidermidis, E. coli, B. Subtilis, Saccharomyces cerevisiae,
Saccharomyces carlsbergensis, Schizosaccharomyces pombi, SF9 cells, C129
cells, 293 cells, Neurospora, and CHO cells, COS cells, HeLa cells, and
immortalized mammalian myeloid and lymphoid cell lines. Preferred
replication systems include M13, ColE1, SV40, baculovirus, lambda,
adenovirus, and the like. A large number of transcription initiation and
termination regulatory regions have been isolated and shown to be effective
in the transcription and translation of heterologous proteins in the various
hosts. Examples of these regions, methods of isolation, manner of
manipulation, etc. are known in the art. Under appropriate expression
conditions, host cells can be used as a source of recombinantly produced S.
epidermidis-derived peptides and polypeptides.
Advantageously, vectors may also include a transcription regulatory element
(i.e., a promoter) operably linked to the S. epidermidis portion. The
promoter may optionally contain operator portions and/or ribosome binding
sites. Non-limiting examples of bacterial promoters compatible with E. coli
include: b-lactamase (penicillinase) promoter; lactose promoter; tryptophan
(trp) promoter; araBAD (arabinose) operon promoter; lambda-derived P.sub.1
promoter and N gene ribosome binding site; and the hybrid tac promoter
derived from sequences of the trp and lac UV5 promoters. Non-limiting
examples of yeast promoters include 3-phosphoglycerate kinase promoter,
glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter, galactokinase
(GAL1) promoter, galactoepimerase promoter, and alcohol dehydrogenase (ADH)
promoter. Suitable promoters for mammalian cells include without limitation
viral promoters such as that from Simian Virus 40 (SV40), Rous sarcoma virus
(RSV), adenovirus (ADV), and bovine papilloma virus (BPV). Mammalian cells
may also require terminator sequences, polyA addition sequences and enhancer
sequences to increase expression. Sequences which cause amplification of the
gene may also be desirable. Furthermore, sequences that facilitate secretion
of the recombinant product from cells, including, but not limited to,
bacteria, yeast, and animal cells, such as secretory signal sequences and/or
prohormone pro region sequences, may also be included. These sequences are
well described in the art.
Nucleic acids encoding wild-type or variant S. epidermidis-derived
polypeptides may also be introduced into cells by recombination events. For
example, such a sequence can be introduced into a cell, and thereby effect
homologous recombination at the site of an endogenous gene or a sequence
with substantial identity to the gene. Other recombination-based methods
such as nonhomologous recombinations or deletion of endogenous genes by
homologous recombination may also be used.
The nucleic acids of the present invention find use as templates for the
recombinant production of S. epidermidis-derived peptides or polypeptides.
Identification and Use of S. epidermidis Nucleic Acid Sequences
The disclosed S. epidermidis polypeptide and nucleic acid sequences, or
other sequences that are contained within ORFs, including complete
protein-coding sequences, of which any of the disclosed S. epidermidis-specific
sequences forms a part, are useful as target components for diagnosis and/or
treatment of S. epidermidis-caused infection
It will be understood that the sequence of an entire protein-coding sequence
of which each disclosed nucleic acid sequence forms a part can be isolated
and identified based on each disclosed sequence. This can be achieved, for
example, by using an isolated nucleic acid encoding the disclosed sequence,
or fragments thereof, to prime a sequencing reaction with genomic S.
epidermidis DNA as template; this is followed by sequencing the amplified
product. The isolated nucleic acid encoding the disclosed sequence, or
fragments thereof, can also be hybridized to S. epidermidis genomic
libraries to identify clones containing additional complete segments of the
protein-coding sequence of which the shorter sequence forms a part. Then,
the entire protein-coding sequence, or fragments thereof, or nucleic acids
encoding all or part of the sequence, or sequence-conservative or
function-conservative variants thereof, may be employed in practicing the
Preferred sequences are those that are useful in diagnostic and/or
therapeutic applications. Diagnostic applications include without limitation
nucleic-acid-based and antibody-based methods for detecting bacterial
infection. Therapeutic applications include without limitation vaccines,
passive immunotherapy, and drug treatments directed against gene products
that are both unique to bacteria and essential for growth and/or replication
Identification of Nucleic Acids Encoding Vaccine Components and Targets for
Agents Effective Against S. epidermidis
The disclosed S. epidermidis genome sequence includes segments that direct
the synthesis of ribonucleic acids and polypeptides, as well as origins of
replication, promoters, other types of regulatory sequences, and intergenic
nucleic acids. The invention encompasses nucleic acids encoding immunogenic
components of vaccines and targets for agents effective against S.
epidermidis. Identification of said immunogenic components involved in the
determination of the function of the disclosed sequences, which can be
achieved using a variety of approaches. Non-limiting examples of these
approaches are described briefly below.
Homology to Known Sequences:
Computer-assisted comparison of the disclosed S. epidermidis sequences with
previously reported sequences present in publicly available databases is
useful for identifying functional S. epidermidis nucleic acid and
polypeptide sequences. It will be understood that protein-coding sequences,
for example, may be compared as a whole, and that a high degree of sequence
homology between two proteins (such as, for example, >80-90%) at the amino
acid level indicates that the two proteins also possess some degree of
functional homology, such as, for example, among enzymes involved in
metabolism, DNA synthesis, or cell wall synthesis, and proteins involved in
transport, cell division, etc. In addition, many structural features of
particular protein classes have been identified and correlate with specific
consensus sequences, such as, for example, binding domains for nucleotides,
DNA, metal ions, and other small molecules; sites for covalent modifications
such as phosphorylation, acylation, and the like; sites of protein:protein
interactions, etc. These consensus sequences may be quite short and thus may
represent only a fraction of the entire protein-coding sequence;
Identification of such a feature in a S. epidermidis sequence is therefore
useful in determining the function of the encoded protein and identifying
useful targets of antibacterial drugs.
Of particular relevance to the present invention are structural features
that are common to secretory, transmembrane, and surface proteins, including
secretion signal peptides and hydrophobic transmembrane domains. S.
epidermidis proteins identified as containing putative signal sequences
and/or transmembrane domains are useful as immunogenic components of
Targets for therapeutic drugs according to the invention include, but are
not limited to, polypeptides, of the invention, whether unique to S.
epidermidis or not, that are essential for growth and/or viability of S.
epidermidis under at least one growth condition. Polypeptides essential for
growth and/or viability can be determined by examining the effect of
deleting and/or disrupting the genes, i.e., by so-called gene "knockout".
Alternatively, genetic footprinting can be used (Smith et al., 1995, Proc.
Natl. Acad. Sci. USA 92:5479-6433; Published International Application WO
94/26933; U.S. Pat. No. 5,612,180). Still other methods for assessing
essentiality includes the ability to isolate conditional lethal mutations in
the specific gene (e.g., temperature sensitive mutations). Other useful
targets for therapeutic drugs, which include polypeptides that are not
essential for growth or viability per se but lead to loss of viability of
the cell, can be used to target therapeutic agents to cells.
Because of the evolutionary relationship between different S. epidermidis
strains, it is believed that the presently disclosed S. epidermidis
sequences are useful for identifying, and/or discriminating between,
previously known and new S. epidermidis strains. It is believed that other
S. epidermidis strains will exhibit at least 70% sequence homology with the
presently disclosed sequence. Systematic and routine analyses of DNA
sequences derived from samples containing S. epidermidis strains, and
comparison with the present sequence allows for the identification of
sequences that can be used to discriminate between strains, as well as those
that are common to all S. epidermidis strains. In one embodiment, the
invention provides nucleic acids, including probes, and peptide and
polypeptide sequences that discriminate between different strains of S.
epidermidis. Strain-specific components can also be identified functionally
by their ability to elicit or react with antibodies that selectively
recognize one or more S. epidermidis strains.
In another embodiment, the invention provides nucleic acids, including
probes, and peptide and polypeptide sequences that are common to all S.
epidermidis strains but are not found in other bacterial species.
S. epidermidis Polypeptides
This invention encompasses isolated S. epidermidis polypeptides encoded by
the disclosed S. epidermidis genomic sequences, including the polypeptides
of the invention contained in the Sequence Listing. Polypeptides of the
invention are preferably at least 5 amino acid residues in length. Using the
DNA sequence information provided herein, the amino acid sequences of the
polypeptides encompassed by the invention can be deduced using methods
well-known in the art. It will be understood that the sequence of an entire
nucleic acid encoding a S. epidermidis polypeptide can be isolated and
identified based on an ORF that encodes only a fragment of the cognate
protein-coding region. This can be achieved, for example, by using the
isolated nucleic acid encoding the ORF, or fragments thereof, to prime a
polymerase chain reaction with genomic S. epidermidis DNA as template; this
is followed by sequencing the amplified product.
The polypeptides of the present invention, including function-conservative
variants of the disclosed ORFs, may be isolated from wild-type or mutant S.
epidermidis cells, or from heterologous organisms or cells (including, but
not limited to, bacteria, fungi, insect, plant, and mammalian cells)
including S. epidermidis into which a S. epidermidis-derived protein-coding
sequence has been introduced and expressed. Furthermore, the polypeptides
may be part of recombinant fusion proteins.
S. epidermidis polypeptides of the invention can be chemically synthesized
using commercially automated procedures such as those referenced herein,
including, without limitation, exclusive solid phase synthesis, partial
solid phase methods, fragment condensation or classical solution synthesis.
The polypeptides are preferably prepared by solid phase peptide synthesis as
described by Merrifield, 1963, J. Am. Chem. Soc. 85:2149. The synthesis is
carried out with amino acids that are protected at the alpha-amino terminus.
Trifunctional amino acids with labile side-chains are also protected with
suitable groups to prevent undesired chemical reactions from occurring
during the assembly of the polypeptides. The alpha-amino protecting group is
selectively removed to allow subsequent reaction to take place at the
amino-terminus. The conditions for the removal of the alpha-amino protecting
group do not remove the side-chain protecting groups.
Methods for polypeptide purification are well-known in the art, including,
without limitation, preparative disc-gel electrophoresis, isoelectric
focusing, HPLC, reversed-phase HPLC, gel filtration, ion exchange and
partition chromatography, and countercurrent distribution. For some
purposes, it is preferable to produce the polypeptide in a recombinant
system in which the S. epidermidis protein contains an additional sequence
tag that facilitates purification, such as, but not limited to, a
polyhistidine sequence. The polypeptide can then be purified from a crude
lysate of the host cell by chromatography on an appropriate solid-phase
matrix. Alternatively, antibodies produced against a S. epidermidis protein
or against peptides derived therefrom can be used as purification reagents.
Other purification methods are possible.
The present invention also encompasses derivatives and homologues of S.
epidermidis-encoded polypeptides. For some purposes, nucleic acid sequences
encoding the peptides may be altered by substitutions, additions, or
deletions that provide for functionally equivalent molecules, i.e.,
function-conservative variants. For example, one or more amino acid residues
within the sequence can be substituted by another amino acid of similar
properties, such as, for example, positively charged amino acids (arginine,
lysine, and histidine); negatively charged amino acids (aspartate and
glutamate); polar neutral amino'acids; and non-polar amino acids.
The isolated polypeptides may be modified by, for example, phosphorylation,
sulfation, acylation, or other protein modifications. They may also be
modified with a label capable of providing a detectable signal, either
directly or indirectly, including, but not limited to, radioisotopes and
To identify S. epidermidis-derived polypeptides for use in the present
invention, essentially the complete genomic sequence of a Staphyolococczs
epidermidis isolate was analyzed. While, in very rare instances, a nucleic
acid sequencing error may be revealed, resolving a rare sequencing error is
well within the art, and such an occurrence will not prevent one skilled in
the art from practicing the invention.
Also encompassed are any S. epidermidis polypeptide sequences that are
contained within the open reading frames (ORFs), including complete
protein-coding sequences, of which any of SEQ ID NO: 2838-SEQ ID NO: 5674
forms a part. Table 2, which is appended herewith and which forms part of
the present specification, provides a putative identification of the
particular function of a polypeptide which is encoded by each ORF, based on
the homology match (determined by the BLAST algorithm) of the predicted
polypeptide with known proteins encoded by ORFs in other organisms. As a
result, one skilled in the art can use the polypeptides of the present
invention for commercial and industrial purposes consistent with the type of
putative identification of the polypeptide.
The present invention provides a library of S. epidermidis-derived
polypeptide sequences, and a corresponding library of nucleic acid sequences
encoding the polypeptides, wherein the polypeptides themselves, or
polypeptides contained within ORFs of which they form a part, comprise
sequences that are contemplated for use as components of vaccines.
Non-limiting examples of such sequences are listed by SEQ ID NO in Table 2,
which is appended herewith and which forms part of the present
The present invention also provides a library of S. epidermidis-derived
polypeptide sequences, and a corresponding library of nucleic acid sequences
encoding the polypeptides, wherein the polypeptides themselves, or
polypeptides contained within ORFs of which they form a part, comprise
sequences lacking homology to any known prokaryotic or eukaryotic sequences.
Such libraries provide probes, primers, and markers which can be used to
diagnose S. epidermidis infection, including use as markers in
epidemiological studies. Non-limiting examples of such sequences are listed
by SEQ ID NO in Table 2, which is appended The present invention also
provides a library of S. epidermidis-derived polypeptide sequences, and a
corresponding library of nucleic acid sequences encoding the polypeptides,
wherein the polypeptides themselves, or polypeptides contained within ORFs
of which they form a part, comprise targets for therapeutic drugs.
Determination of Staphylococcus Protein Antigens for Antibody and Vaccine
The selection of Staphylococcus protein antigens for vaccine development can
be derived from the nucleic acids encoding S. epidermidis polypeptides.
First, the ORF's can be analyzed for homology to other known exported or
membrane proteins and analyzed using the discriminant analysis described by
Klein; et al. (Klein, P., Kanehsia, M., and DeLisi, C. (1985) Biochimica et
Biophysica Acta 815, 468-476) for predicting exported and membrane proteins.
Homology searches can be performed using the BLAST algorithm contained in
the Wisconsin Sequence Analysis Package (Genetics Computer Group, University
Research Park, 575 Science Drive, Madison, Wis. 53711) to compare each
predicted ORF amino acid sequence with all sequences found in the current
GenBank, SWISS-PROT and PIR databases. BLAST searches for local alignments
between the ORF and the databank sequences and reports a probability score
which indicates the probability of finding this sequence by chance in the
database. ORF's with significant homology (e.g. probabilities lower than
1.times.10.sup.-6 that the homology is only due to random chance) to
membrane or exported proteins represent protein antigens for vaccine
development. Possible functions can be provided to S. epidermidis genes
based on sequence homology to genes cloned in other organisms.
Discriminant analysis (Klein, et al. supra) can be used to examine the ORF
amino acid sequences. This algorithm uses the intrinsic information
contained in the ORF amino acid sequence and compares it to information
derived from the properties of known membrane and exported proteins. This
comparison predicts which proteins will be exported, membrane associated or
cytoplasmic. ORF amino acid sequences identified as exported or membrane
associated by this algorithm are likely protein antigens for vaccine
Production of Fragments and Analogs of S. epidermidis Nucleic Acids and
Based on the discovery of the S. epidermidis gene products of the invention
provided in the Sequence Listing, one skilled in the art can alter the
disclosed structure of S. epidermidis genes, e.g., by producing fragments or
analogs, and test the newly produced structures for activity. Examples of
techniques known to those skilled in the relevant art which allow the
production and testing of fragments and analogs are discussed below. These,
or analogous methods can be used to make and screen libraries of
polypeptides, e.g., libraries of random peptides or libraries of fragments
or analogs of cellular proteins for the ability to bind S. epidermidis
polypeptides. Such screens are useful for the identification of inhibitors
of S. epidermidis.
Generation of Fragments
Fragments of a protein can be produced in several ways, e.g., recombinantly,
by proteolytic digestion, or by chemical synthesis. Internal or terminal
fragments of a polypeptide can be generated by removing one or more
nucleotides from one end (for a terminal fragment) or both ends (for an
internal fragment) of a nucleic acid which encodes the polypeptide.
Expression of the mutagenized DNA produces polypeptide fragments. Digestion
with "end-nibbling" endonucleases can thus generate DNAs which encode an
array of fragments. DNAs which encode fragments of a protein can also be
generated by random shearing, restriction digestion or a combination of the
Fragments can also be chemically synthesized using techniques known in the
art such as conventional Merrifield solid phase f-Moc or t-Boc chemistry.
For example, peptides of the present invention may be arbitrarily divided
into fragments of desired length with no overlap of the fragments, or
divided into overlapping fragments of a desired length.
Alteration of Nucleic Acids and Polypeptides: Random Methods
Amino acid sequence variants of a protein can be prepared by random
mutagenesis of DNA which encodes a protein or a particular domain or region
of a protein. Useful methods include PCR mutagenesis and saturation
mutagenesis. A library of random amino acid sequence variants can also be
generated by the synthesis of a set of degenerate oligonucleotide sequences.
(Methods for screening proteins in a library of variants are elsewhere
In PCR mutagenesis, reduced Taq polymerase fidelity is used to introduce
random mutations into a cloned fragment of DNA (Leung et al., 1989,
Technique 1:11-15). The DNA region to be mutagenized is amplified using the
polymerase chain reaction (PCR) under conditions that reduce the fidelity of
DNA synthesis by Taq DNA polymerase, e.g., by using a dGTP/dATP ratio of
five and adding Mn.sup.2+ to the PCR reaction. The pool of amplified DNA
fragments are inserted into appropriate cloning vectors to provide random
Saturation mutagenesis allows for the rapid introduction of a large number
of single base substitutions into cloned DNA fragments (Mayers et al., 1985,
Science 229:242). This technique includes generation of mutations, e.g., by
chemical treatment or irradiation of single-stranded DNA in vitro, and
synthesis of a complimentary DNA strand. The mutation frequency can be
modulated by modulating the severity of the treatment, and essentially all
possible base substitutions can be obtained. Because this procedure does not
involve a genetic selection for mutant fragments both neutral substitutions,
as well as those that alter function, are obtained. The distribution of
point mutations is not biased toward conserved sequence elements.
A library of homologs can also be generated from a set of degenerate
oligonucleotide sequences. Chemical synthesis of a degenerate sequences can
be carried out in an automatic DNA synthesizer, and the synthetic genes then
ligated into an appropriate expression vector. The synthesis of degenerate
oligonucleotides is known in the art (see for example, Narang, S A (1983)
Tetrahedron 39:3; Itakura et al. (1981) Recombinant DNA, Proc 3rd Cleveland
Sympos. Macromolecules, ed. AG Walton, Amsterdam: Elsevier pp 273-289;
Itakura et al. (1984) Annu. Rev. Biochem. 53:323; Itakura et al. (1984)
Science 198:1056; Ike et al. (1983) Nucleic Acid Res. 11:477. Such
techniques have been employed in the directed evolution of other proteins
(see, for example, Scott et al. (1990) Science 249:386-390; Roberts et al.
(1992) PNAS 89:2429-2433; Devlin et al. (1990) Science 249:404-406; Cwirla
et al. (1990) PNAS 87: 6378-6382; as well as U.S. Pat. Nos. 5,223,409,
5,198,346, and 5,096,815).
Alteration of Nucleic Acids and Polypeptides: Methods for Directed
Non-random or directed, mutagenesis techniques can be used to provide
specific sequences or mutations in specific regions. These techniques can be
used to create variants which include, e.g., deletions, insertions, or
substitutions, of residues of the known amino acid sequence of a protein.
The sites for mutation can be modified individually or in series, e.g., by
(1) substituting first with conserved amino acids and then with more radical
choices depending upon results achieved, (2) deleting the target residue, or
(3) inserting residues of the same or a different class adjacent to the
located site, or combinations of options 1-3.
Alanine Scanning Mutagenesis
Alanine scanning mutagenesis is a useful method for identification of
certain residues or regions of the desired protein that are preferred
locations or domains for mutagenesis, Cunningham and Wells (Science
244:1081-1085, 1989). In alanine scanning, a residue or group of target
residues are identified (e.g., charged residues such as Arg, Asp, H is, Lys,
and Glu) and replaced by a neutral or negatively charged amino acid (most
preferably alanine or polyalanine). Replacement of an amino acid can affect
the interaction of the amino acids with the surrounding aqueous environment
in or outside the cell. Those domains demonstrating functional sensitivity
to the substitutions are then refined by introducing further or other
variants at or for the sites of substitution. Thus, while the site for
introducing an amino acid sequence variation is predetermined, the nature of
the mutation per se need not be predetermined. For example, to optimize the
performance of a mutation at a given site, alanine scanning or random
mutagenesis may be conducted at the target codon or region and the expressed
desired protein subunit variants are screened for the optimal combination of
Oligonucleotide-mediated mutagenesis is a useful method for preparing
substitution, deletion, and insertion variants of DNA, see, e.g., Adelman et
al., (DNA 2:183, 1983). Briefly, the desired DNA is altered by hybridizing
an oligonucleotide encoding a mutation to a DNA template, where the template
is the single-stranded form of a plasmid or bacteriophage containing the
unaltered or native DNA sequence of the desired protein. After
hybridization, a DNA polymerase is used to synthesize an entire second
complementary strand of the template that will thus incorporate the
oligonucleotide primer, and will code for the selected alteration in the
desired protein DNA. Generally, oligonucleotides of at least 25 nucleotides
in length are used. An optimal oligonucleotide will have 12 to 15
nucleotides that are completely complementary to the template on either side
of the nucleotide(s) coding for the mutation. This ensures that the
oligonucleotide will hybridize properly to the single-stranded DNA template
molecule. The oligonucleotides are readily synthesized using techniques
known in the art such as that described by Crea et al; (Proc. Natl. Acad.
Sci. USA, 75: 5765-).
Another method for preparing variants, cassette mutagenesis, is based on the
technique described by Wells et al. (Gene, 34:315). The starting
material is a plasmid (or other vector) which includes the protein subunit
DNA to be mutated. The codon(s) in the protein subunit DNA to be mutated are
identified. There must be a unique restriction endonuclease site on each
side of the identified mutation site(s). If no such restriction sites exist,
they may be generated using the above-described oligonucleotide-mediated
mutagenesis method to introduce them at appropriate locations in the desired
protein subunit DNA. After the restriction sites have been introduced into
the plasmid, the plasmid is cut at these sites to linearize it. A
double-stranded oligonucleotide encoding the sequence of the DNA between the
restriction sites but containing the desired mutation(s) is synthesized
using standard procedures. The two strands are synthesized separately and
then hybridized together using standard techniques. This double-stranded
oligonucleotide is referred to as the cassette. This cassette is designed to
have 3' and 5' ends that are comparable with the ends of the linearized
plasmid, such that it can be directly ligated to the plasmid. This plasmid
now contains the mutated desired protein subunit DNA sequence.
Combinatorial mutagenesis can also be used to generate mutants (Ladner et
al., WO 88/06630). In this method, the amino acid sequences for a group of
homologs or other related proteins are aligned, preferably to promote the
highest homology possible. All of the amino acids which appear at a given
position of the aligned sequences can be selected to create a degenerate set
of combinatorial sequences. The variegated library of variants is generated
by combinatorial mutagenesis at the nucleic acid level, and is encoded by a
variegated gene library. For example, a mixture of synthetic
oligonucleotides can be enzymatically ligated into gene sequences such that
the degenerate set of potential sequences are expressible as individual
peptides, or alternatively, as a set of larger fusion proteins containing
the set of degenerate sequences.
Other Modifications of S. epidermidis Nucleic Acids and Polypeptides
It is possible to modify the structure of a S. epidermidis polypeptide for
such purposes as increasing solubility, enhancing stability (e.g., shelf
life ex vivo and resistance to proteolytic degradation in vivo). A modified
S. epidermidis protein or peptide can be produced in which the amino acid
sequence has been altered, such as by amino acid substitution, deletion, or
addition as described herein.
An S. epidermidis peptide can also be modified by substitution of cysteine
residues preferably with alanine, serine, threonine, leucine or glutamic
acid residues to minimize dimerization via disulfide linkages. In addition,
amino acid side chains of fragments of the protein of the invention can be
chemically modified. Another modification is cyclization of the peptide.
In order to enhance stability and/or reactivity, a S. epidermidis
polypeptide can be modified to incorporate one or more polymorphisms in the
amino acid sequence of the protein resulting from any natural allelic
variation. Additionally, D-amino acids, non-natural amino acids, or
non-amino acid analogs can be substituted or added to pro duce a modified
protein within the scope of this invention. Furthermore, an S. epidermidis
polypeptide can be modified using polyethylene glycol (PEG) according to the
method of A. Sehon and co-workers (Wie et al., supra) to produce a protein
conjugated with PEG. In addition, PEG can be added during chemical synthesis
of the protein. Other modifications of S. epidermidis proteins include
reduction/alkylation (Tarr, Methods of Protein Microcharacterization, J. E.
Silver ed., Humana Press, Clifton N.J. 155-194 (1986)); acylation (Tarr,
supra); chemical coupling to an appropriate carrier (Mishell and Shiigi, eds,
Selected Methods in Cellular Immunology, WH Freeman, San Francisco, Calif.
(1980), U.S. Pat. No. 4,939,239; or mild formalin treatment (Marsh, (1971)
Int. Arch. of Allergy and Appl. Immunol., 41: 199-215).
To facilitate purification and potentially increase solubility of a S.
epidermidis protein or peptide, it is possible to add an amino acid fusion
moiety to the peptide backbone. For example, hexa-histidine can be added to
the protein for purification by immobilized metal ion affinity
chromatography (Hochuli, E. et al., (1988) Bio/Technology, 6: 1321-1325). In
addition, to facilitate isolation of peptides free of irrelevant sequences,
specific endoprotease cleavage sites can be introduced between the sequences
of the fusion moiety and the peptide.
To potentially aid proper antigen processing of epitopes within an S.
epidermidis polypeptide, canonical protease sensitive sites can be
engineered between regions, each comprising at least one epitope via
recombinant or synthetic methods. For example, charged amino acid pairs,
such as KK or RR, can be introduced between regions within a protein or
fragment during recombinant construction thereof. The resulting peptide can
be rendered sensitive to cleavage by cathepsin and/or other trypsin-like
enzymes which would generate portions of the protein containing one or more
epitopes. In addition, such charged amino acid residues can result in an
increase in the solubility of the peptide.
Primary Methods for Screening Polypeptides and Analogs
Various techniques are known in the art for screening generated mutant gene
products. Techniques for screening large gene libraries often include
cloning the gene library into replicable expression vectors, transforming
appropriate cells with the resulting library of vectors, and expressing the
genes under conditions in which detection of a desired activity, e.g., in
this case, binding to S. epidermidis polypeptide or an interacting protein,
facilitates relatively easy isolation of the vector encoding the gene whose
product was detected. Each of the techniques described below is amenable to
high through-put analysis for screening large numbers of sequences created,
e.g., by random mutagenesis techniques.
Two Hybrid Systems
Two hybrid assays such as the system described below (as with the other
screening methods described herein), can be used to identify polypeptides,
e.g., fragments or analogs of a naturally-occurring S. epidermidis
polypeptide, e.g., of cellular proteins, or of randomly generated
polypeptides which bind to an S. epidermidis protein. (The S. epidermidis
domain is used as the bait protein and the library of variants are expressed
as prey fusion proteins.) In an analogous fashion, a two hybrid assay (as
with the other screening methods described herein), can be used to find
polypeptides which bind a S. epidermidis polypeptide.
In one approach to screening assays, the Staphylococcus peptides are
displayed on the surface of a cell or viral particle, and the ability of
particular cells or viral particles to bind an appropriate receptor protein
via the displayed product is detected in a "panning assay". For example, the
gene library can be cloned into the gene for a surface membrane protein of a
bacterial cell, and the resulting fusion protein detected by panning (Ladner
et al., WO 88/06630; Fuchs et al. (1991) Bio/Technology 9:1370-1371; and
Goward et al. (1992) TIBS 18:136-140). In a similar fashion, a detectably
labeled ligand can be used to score for potentially functional peptide
homologs. Fluorescently labeled ligands, e.g., receptors, can be used to
detect homologs which retain ligand-binding activity. The use of
fluorescently labeled ligands, allows cells to be visually-inspected and
separated under a fluorescence microscope, or, where the morphology of the
cell permits, to be separated by a fluorescence-activated cell sorter.
A gene library can be expressed as a fusion protein on the surface of a
viral particle. For instance, in the filamentous phage system, foreign
peptide sequences can be expressed on the surface of infectious phage,
thereby conferring two significant benefits. First, since these phage can be
applied to affinity matrices at concentrations well over 10.sup.13 phage per
milliliter, a large number of phage can be screened at one time. Second,
since each infectious phage displays a gene product on its surface, if a
particular phage is recovered from an affinity matrix in low yield, the
phage can be amplified by another round of infection. The group of almost
identical E. coli filamentous phages, M13, fd., and f1, are most often used
in phage display libraries. Either of the phage gIII or gVIII coat proteins
can be used to generate fusion proteins without disrupting the ultimate
packaging of the viral particle. Foreign epitopes can be expressed at the
NH.sub.2-terminal end of pIII and phage bearing such epitopes recovered from
a large excess of phage lacking this epitope (Ladner et al. PCT publication
WO 90/02909; Garrard et al., PCT publication WO 92/09690; Marks et al.
(1992) J. Biol. Chem. 267:16007-16010; Griffiths et al. (1993) EMBO J
12:725-734; Clackson et al. (1991) Nature 352:624-628; and Barbas et al.
(1992) PNAS 89:4457-4461).
A common approach uses the maltose receptor of E. coli (the outer membrane
protein, LamB) as a peptide fusion partner (Charbit et al. (1986) EMBO 5,
3029-3037). Oligonucleotides have been inserted into plasmids encoding the
LamB gene to produce peptides fused into one of the extracellular loops of
the protein. These peptides are available for binding to ligands, e.g., to
antibodies, and can elicit an immune response when the cells are
administered to animals. Other cell surface proteins, e.g., OmpA (Schorr et
al. (1991) Vaccines 91, pp. 387-392), PhoE (Agterberg, et al. (1990) Gene
88, 37-45), and PAL (Fuchs et al. (1991) Bio/Tech 9, 1369-1372), as well as
large bacterial surface structures have served as vehicles for peptide
display. Peptides can be fused to pilin, a protein which polymerizes to form
the pilus-a conduit for interbacterial exchange of genetic information (Thiry
et al. (1989) Appl. Environ. Microbiol. 55, 984-993). Because of its role in
interacting with other cells, the pilus provides a useful support for the
presentation of peptides to the extracellular environment. Another large
surface structure used for peptide display is the bacterial motive organ,
the flagellum. Fusion of peptides to the subunit protein flagellin offers a
dense array of many peptide copies on the host cells (Kuwajima et al. (1988)
Bio/Tech. 6, 1080-1083). Surface proteins of other bacterial species have
also served as peptide fusion partners. Examples include the Staphylococcus
protein A and the outer membrane IgA protease of Neisseria (Hansson et al.
(1992) J. Bacteriol. 174, 4239-4245 and Klauser et al. (1990) EMBO J. 9,
In the filamentous phage systems and the LamB system described above, the
physical link between the peptide and its encoding DNA occurs by the
containment of the DNA within a particle (cell or phage) that carries the
peptide on its surface. Capturing the peptide captures the particle and the
DNA within. An alternative scheme uses the DNA-binding protein Lacd to form
a link between peptide and DNA (Cull et al. (1992) PNAS USA 89:1865-1869).
This system uses a plasmid containing the Lacd gene with an oligonucleotide
cloning site at its 3'-end. Under the controlled induction by arabinose, a
LacI-peptide fusion protein is produced. This fusion retains the natural
ability of LacI to bind to a short DNA sequence known as LacO operator (LacO).
By installing two copies of LacO on the expression plasmid, the LacI-peptide
fusion binds tightly to the plasmid that encoded it. Because the plasmids in
each cell contain only a single oligonucleotide sequence and each cell
expresses only a single peptide sequence, the peptides become specifically
and stablely associated with the DNA sequence that directed its synthesis.
The cells of the library are gently lysed and the peptide-DNA complexes are
exposed to a matrix of immobilized receptor to recover the complexes
containing active peptides. The associated plasmid DNA is then reintroduced
into cells for amplification and DNA sequencing to determine the identity of
the peptide ligands. As a demonstration of the practical utility of the
method, a large random library of dodecapeptides was made and selected on a
monoclonal antibody raised against the opioid peptide dynorphin B. A cohort
of peptides was recovered, all related by a consensus sequence corresponding
to a six-residue portion of dynorphin B. (Cull et al. (1992) Proc. Natl.
Acad. Sci. U.S.A. 89-1869)
This scheme, sometimes referred to as peptides-on-plasmids, differs in two
important ways from the phage display methods. First, the peptides are
attached to the C-terminus of the fusion protein, resulting in the display
of the library members as peptides having free carboxy termini. Both of the
filamentous phage coat proteins, pIII and pVIII, are anchored to the phage
through their C-termini, and the guest peptides are placed into the
outward-extending N-terminal domains. In some designs, the phage-displayed
peptides are presented right at the amino terminus of the fusion protein. (Cwirla,
et al. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 6378-6382) A second
difference is the set of biological biases affecting the population of
peptides actually present in the libraries. The LacI fusion molecules are
confined to the cytoplasm of the host cells. The phage coat fusions are
exposed briefly to the cytoplasm during translation but are rapidly secreted
through the inner membrane into the periplasmic compartment, remaining
anchored in the membrane by their C-terminal hydrophobic domains, with the
N-termini, containing the peptides, protruding into the periplasm while
awaiting assembly into phage particles. The peptides in the Lacd and phage
libraries may differ significantly as a result of their exposure to
different proteolytic activities. The phage coat proteins require transport
across the inner membrane and signal peptidase processing as a prelude to
incorporation into phage. Certain peptides exert a deleterious effect on
these processes and are underrepresented in the libraries (Gallop et al.,
(1994) J. Med. Chem. 37(9):1233-1251). These particular biases are not a
factor in the LacI display system.
The number of small peptides available in recombinant random libraries is
enormous. Libraries of 10.sup.7-10.sup.9 independent clones are routinely
prepared. Libraries as large as 10.sup.11 recombinants have been created,
but this size approaches the practical limit for clone libraries. This
limitation in library size occurs at the step of transforming the DNA
containing randomized segments into the host bacterial cells. To circumvent
this limitation, an in vitro system based on the display of nascent peptides
in polysome complexes has recently been developed. This display library
method has the potential of producing libraries 3-6 orders of magnitude
larger than the currently available phage/phagemid or plasmid libraries.
Furthermore, the construction of the libraries, expression of the peptides,
and screening, is done in an entirely cell-free format.
In one application of this method (Gallop et al. (1994) J. Med. Chem.
37(9):1233-1251), a molecular DNA library encoding 10.sup.12 decapeptides
was constructed and the library expressed in an E. coli S30 in vitro coupled
transcription/translation system. Conditions were chosen to stall the
ribosomes on the mRNA, causing the accumulation of a substantial proportion
of the RNA in polysomes and yielding complexes containing nascent peptides
still linked to their encoding RNA. The polysomes are sufficiently robust to
be affinity purified on immobilized receptors in much the same way as the
more conventional recombinant peptide display libraries are screened. RNA
from the bound complexes is recovered, converted to cDNA, and amplified by
PCR to produce a template for the next round of synthesis and screening. The
polysome display method can be coupled to the phage display system.
Following several rounds of screening, cDNA from the enriched pool of
polysomes was cloned into a phagemid vector. This vector serves as both a
peptide expression vector, displaying peptides fused to the coat proteins,
and as a DNA sequencing vector for peptide identification. By expressing the
polysome-derived peptides on phage, one can either continue the affinity
selection procedure in this format or assay the peptides on individual
clones for binding activity in a phage ELISA, or for binding specificity in
a completion phage ELISA (Barret, et al. (1992) Anal. Biochem 204, 357-364).
To identify the sequences of the active peptides one sequences the DNA
produced by the phagemid host.
Secondary Screening of Polypeptides and Analogs
The high through-put assays described above can be followed by secondary
screens in order to identify further biological activities which will, e.g.,
allow one skilled in the art to differentiate agonists from antagonists. The
type of a secondary screen used will depend on the desired activity that
needs to be tested. For example, an assay can be developed in which the
ability to inhibit an interaction between a protein of interest and its
respective ligand can be used to identify antagonists from a group of
peptide fragments isolated though one of the primary screens described
Therefore, methods for generating fragments and analogs and testing them for
activity are known in the art. Once the core sequence of interest is
identified, it is routine for one skilled in the art to obtain analogs and
Peptide Mimetics of S. epidermidis Polypeptides
The invention also provides for reduction of the protein binding domains of
the subject S. epidermidis polypeptides to generate mimetics, e.g. peptide
or non-peptide agents. The peptide mimetics are able to disrupt binding of a
polypeptide to its counter ligand, e.g., in the case of a S. epidermidis
polypeptide binding to a naturally occurring ligand. The critical residues
of a subject S. epidermidis polypeptide which are involved in molecular
recognition of a polypeptide can be determined and used to generate S.
epidermidis-derived peptidomimetics which competitively or noncompetitively
inhibit binding of the S. epidermidis polypeptide with an interacting
polypeptide (see, for example, European patent applications EP-412,762A and
For example, scanning mutagenesis can be used to map the amino acid residues
of a particular S. epidermidis polypeptide involved in binding an
interacting polypeptide, peptidomimetic compounds (e.g. diazepine or
isoquinoline derivatives) can be generated which mimic those residues in
binding to an interacting polypeptide, and which therefore can inhibit
binding of a S. epidermidis polypeptide to an interacting polypeptide and
thereby interfere with the function of S. epidermidis polypeptide. For
instance, non-hydrolyzable peptide analogs of such residues can be generated
using benzodiazepine (e.g., see Freidinger et al. in Peptides: Chemistry and
Biology, G. R. Marshall ed., ESCOM Publisher: Leiden, Netherlands, 1988),
azepine (e.g., see Huffman et al. in Peptides: Chemistry and Biology, G. R.
Marshall ed., ESCOM Publisher: Leiden, Netherlands, 1988), substituted gama
lactam rings (Garvey et al. in Peptides: Chemistry and Biology, G. R.
Marshall ed., ESCOM Publisher: Leiden, Netherlands, 1988), keto-methylene
pseudopeptides (Ewenson et al. (1986) J Med Chem 29:295; and Ewenson et al.
in Peptides: Structure and Function (Proceedings of the 9th American Peptide
Symposium) Pierce Chemical Co. Rockland, Ill., 1985), b-turn dipeptide cores
(Nagai et al. (1985) Tetrahedron Lett 26:647; and Sato et al. (1986) J Chem
Soc Perkin Trans 1:1231), and b-aminoalcohols (Gordon et al. (1985) Biochem
Biophys Res Commun 126:419; and et al. (1986) Biochem Biophys Res Commun
Vaccine Formulations for S. epidermidis Nucleic Acids and Polypeptides
This invention also features vaccine compositions for protection against
infection by S. epidermidis or for treatment of S. epidermidis infection, a
gram-positive spiral bacterium. In one embodiment, the vaccine compositions
contain one or more immunogenic components such as a surface protein from S.
epidermidis, or portion thereof, and a pharmaceutically acceptable carrier.
Nucleic acids within the scope of the invention are exemplified by the
nucleic acids of the invention contained in the Sequence Listing which
encode S. epidermidis surface proteins. Any nucleic acid encoding an
immunogenic S. epidermidis protein, or portion thereof, which is capable of
expression in a cell, can be used in the present invention. These vaccines
have therapeutic and prophylactic utilities.
One aspect of the invention provides a vaccine composition for protection
against infection by S. epidermidis which contains at least one immunogenic
fragment of an S. epidermidis protein and a pharmaceutically acceptable
carrier. Preferred fragments include peptides of at least about 10 amino
acid residues in length, preferably about 10-20 amino acid residues in
length, and more preferably about 12-16 amino acid residues in length.
Immunogenic components of the invention can be obtained, for example, by
screening polypeptides recombinantly produced from the corresponding
fragment of the nucleic acid encoding the full-length S. epidermidis
protein. In addition, fragments can be chemically synthesized using
techniques known in the art such as conventional Merrifield solid phase f-Moc
or t-Bbc chemistry.
In one embodiment, immunogenic components are identified by the ability of
the peptide to stimulate T cells. Peptides which stimulate T cells, as
determined by, for example, T cell proliferation or cytokine secretion are
defined herein as comprising at least one T cell epitope. T cell epitopes
are believed to be involved in initiation and perpetuation of the immune
response to the protein allergen which is responsible for the clinical
symptoms of allergy. These T cell epitopes are thought to trigger early
events at the level of the T helper cell by binding to an appropriate HLA
molecule on the surface of an antigen presenting cell, thereby stimulating
the T cell subpopulation with the relevant T cell receptor for the epitope.
These events lead to T cell proliferation, lymphokine secretion, local
inflammatory reactions, recruitment of additional immune cells to the site
of antigen/T cell interaction, and activation of the B cell cascade, leading
to the production of antibodies. A T cell epitope is the basic element, or
smallest unit of recognition by a T cell receptor, where the epitope
comprises amino acids essential to receptor recognition (e.g., approximately
6 or 7 amino acid residues). Amino acid sequences which mimic those of the T
cell epitopes are within the scope of this invention.
Screening immunogenic components can be accomplished using one or more of
several different assays. For example, in vitro, peptide T cell stimulatory
activity is assayed by contacting a peptide known or suspected of being
immunogenic with an antigen presenting cell which presents appropriate MHC
molecules in a T cell culture. Presentation of an immunogenic S. epidermidis
peptide in association with appropriate MHC molecules to T cells in
conjunction with the necessary co-stimulation has the effect of transmitting
a signal to the T cell that induces the production of increased levels of
cytokines, particularly of interleukin-2 and interleukin-4. The culture
supernatant can be obtained and assayed for interleukin-2 or other known
cytokines. For example, any one of several conventional assays for
interleukin-2 can be employed, such as the assay described in Proc. Natl.
Acad Sci USA, 86: 1333 (1989) the pertinent portions of which are
incorporated herein by reference. A kit for an assay for the production of
interferon is also available from Genzyme Corporation (Cambridge, Mass.).
Alternatively, a common assay for T cell proliferation entails measuring
tritiated thymidine incorporation. The proliferation of T cells can be
measured in vitro by determining the amount of .sup.3H-labeled thymidine
incorporated into the replicating DNA of cultured cells. Therefore, the rate
of DNA synthesis and, in turn, the rate of cell division can be quantified.
Vaccine compositions of the invention containing immunogenic components
(e.g., S. epidermidis polypeptide or fragment thereof or nucleic acid
encoding an S. epidermidis polypeptide or fragment thereof) preferably
include a pharmaceutically acceptable carrier. The term "pharmaceutically
acceptable carrier" refers to a carrier that does not cause an allergic
reaction or other untoward effect in patients to whom it is administered.
Suitable pharmaceutically acceptable carriers include, for example, one or
more of water, saline, phosphate buffered saline, dextrose, glycerol,
ethanol and the like, as well as combinations thereof. Pharmaceutically
acceptable carriers may further comprise minor amounts of auxiliary
substances such as wetting or emulsifying agents, preservatives or buffers,
which enhance the shelf life or effectiveness of the antibody. For vaccines
of the invention containing S. epidermidis polypeptides, the polypeptide is
co-administered with a suitable adjuvant.
It will be apparent to those of skill in the art that the therapeutically
effective amount of DNA or protein of this invention will depend, inter alia,
upon the administration schedule, the unit dose of antibody administered,
whether the protein or DNA is administered in combination with other
therapeutic agents, the immune status and health of the patient, and the
therapeutic activity of the particular protein or DNA.
Vaccine compositions are conventionally administered parenterally, e.g., by
injection, either subcutaneously or intramuscularly. Methods for
intramuscular immunization are described by Wolff et al. (1990) Science 247:
1465-1468 and by Sedegah et al. (1994) Immunology 91: 9866-9870. Other modes
of administration include oral and pulmonary formulations, suppositories,
and transdermal applications. Oral immunization is preferred over parenteral
methods for inducing protection against infection by S. epidermidis. Cain
et. al. (1993) Vaccine 11: 637-642. Oral formulations include such normally
employed excipients as, for example, pharmaceutical grades of mannitol,
lactose, starch, magnesium stearate, sodium saccharine, cellulose, magnesium
carbonate, and the like.
The vaccine compositions of the invention can include an adjuvant,
including, but not limited to aluminum hydroxide; N-acetyl-muramyl-L-threonyl-D-isoglutamine
(thr-MDP); N-acetyl-nor-muramyl-L-alanyl-D-isoglutamine (CGP 11637, referred
to as nor-MDP);
palmitoyl-sn-glycero-3-hydroxyphos-phoryloxy)-ethylamine (CGP 19835A,
referred to a MTP-PE); RIBI, which contains three components from bacteria;
monophosphoryl lipid A; trehalose dimycoloate; cell wall skeleto'n (MPL+TDM+CWS)
in a 2% squalene/Tween 80 emulsion; and cholera toxin. Others which may be
used are non-toxic derivatives of cholera toxin, including its B subunit,
and/or conjugates or genetically engineered fusions of the S. epidermidis
polypeptide with cholera toxin or its B subunit, prochcleragenoid, fungal
polysaccharides, including schizophyllan, muramyl dipeptide, muramyl
dipeptide derivatives, phorbol esters, labile toxin of E. coli, non-S.
epidermidis bacterial lysates, block polymers or saponins.
Other suitable delivery methods include biodegradable microcapsules or
immuno-stimulating complexes (ISCOMs), cochleates, or liposomes, genetically
engineered attenuated live vectors such as viruses or bacteria, and
recombinant (chimeric) virus-like particles, e.g., bluetongue. The amount of
adjuvant employed will depend on the type of adjuvant used. For example,
when the mucosal adjuvant is cholera toxin, it is suitably used in an amount
of 5 mg to 50 mg, for example 10 mg to 35 mg. When used in the form of
microcapsules, the amount used will depend on the amount employed in the
matrix of the microcapsule to achieve the desired dosage. The determination
of this amount is within the skill of a person of ordinary skill in the art.
Carrier systems in humans may include enteric release capsules protecting
the antigen from the acidic environment of the stomach, and including S.
epidermidis polypeptide in an insoluble form as fusion proteins. Suitable
carriers for the vaccines of the invention are enteric coated capsules and
polylactide-glycolide microspheres. Suitable diluents are 0.2 N NaHCO.sub.3
Vaccines of the invention can be administered as a primary prophylactic
agent in adults or in children, as a secondary prevention, after successful
eradication of S. epidermidis in an infected host, or as a therapeutic agent
in the aim to induce an immune response in a susceptible host to prevent
infection by S. epidermidis. The vaccines of the invention are administered
in amounts readily determined by persons of ordinary skill in the art. Thus,
for adults a suitable dosage will be in the range of 10 mg to 10 g,
preferably 10 mg to 100 mg. A suitable dosage for adults will also be in the
range of 5 mg to 500 mg. Similar dosage ranges will be applicable for
children. Those skilled in the art will recognize that the optimal dose may
be more or less depending upon the patient's body weight, disease, the route
of administration, and other factors. Those skilled in the art will also
recognize that appropriate dosage levels can be obtained based on results
with known oral vaccines such as, for example, a vaccine based on an E. coli
lysate (6 mg dose daily up to total of 540 mg) and with an enterotoxigenic
E. coli purified antigen (4 doses of 1 mg) (Schulman et al., J. Urol.
150:917-921 (1993); Boedecker et al., American Gastroenterological Assoc.
999:A-222 (1993)). The number of doses will depend upon the disease, the
formulation, and efficacy data from clinical trials. Without intending any
limitation as to the course of treatment, the treatment can be administered
over 3 to 8 doses for a primary immunization schedule over I month (Boedeker,
American Gastroenterological Assoc. 888:A-222 (1993)).
In a preferred embodiment, a vaccine composition of the invention can be
based on a killed whole E. coli preparation with an immunogenic fragment of
a S. epidermidis protein of the invention expressed on its surface or it can
be based on an E. coli lysate, wherein the killed E. coli acts as a carrier
or an adjuvant.
It will be apparent to those skilled in the art that some of the vaccine
compositions of the invention are useful only for preventing S. epidermidis
infection, some are useful only for treating S. epidermidis infection, and
some are useful for both preventing and treating S. epidermidis infection.
In a preferred embodiment, the vaccine composition of the invention provides
protection against S. epidermidis infection by stimulating humoral and/or
cell-mediated immunity against S. epidermidis. It should be understood that
amelioration of any of the symptoms of S. epidermidis infection is a
desirable clinical goal, including a lessening of the dosage of medication
used to treat S. epidermidis-caused disease, or an increase in the
production of antibodies in the serum or mucous of patients.
Antibodies Reactive With S. epidermidis Polypeptides
The invention also includes antibodies specifically reactive with the
subject S. epidermidis polypeptide. Anti-protein/anti-peptide antisera or
monoclonal antibodies can be made by standard protocols (See, for example,
Antibodies: A Laboratory Manual ed. by Harlow and Lane (Cold Spring Harbor
Press: 1988)). A mammal such as a mouse, a hamster or rabbit can be
immunized with an immunogenic form of the peptide. Techniques for conferring
immunogenicity on a protein or peptide include conjugation to carriers or
other techniques well known in the art. An immunogenic portion of the
subject S. epidermidis polypeptide can be administered in the presence of
adjuvant. The progress of immunization can be monitored by detection of
antibody titers in plasma or serum. Standard ELISA or other immunoassays can
be used with the immunogen as antigen to assess the levels of antibodies.
In a preferred embodiment, the subject antibodies are immunospecific for
antigenic determinants of the S. epidermidis polypeptides of the invention,
e.g. antigenic determinants of a polypeptide of the invention contained in
the Sequence Listing, or a closely related human or non-human mammalian
homolog (e.g., 90% homologous, more preferably at least 95% homologous). In
yet a further preferred embodiment of the invention, the anti-S. epidermidis
antibodies do not substantially cross react (i.e., react specifically) with
a protein which is for example, less than 80% percent homologous to a
sequence of the invention contained in the Sequence Listing. By "not
substantially cross react", it is meant that the antibody has a binding
affinity for a non-homologous protein which is less than 10 percent, more
preferably less than 5 percent, and even more preferably less than 1
percent, of the binding affinity for a protein of the invention contained in
the Sequence Listing. In a most preferred embodiment, there is no
cross-reactivity between bacterial and mammalian antigens.
The term antibody as used herein is intended to include fragments thereof
which are also specifically reactive with S. epidermidis polypeptides.
Antibodies can be fragmented using conventional techniques and the fragments
screened for utility in the same manner as described above for whole
antibodies. For example, F(ab').sub.2 fragments can be generated by treating
antibody with pepsin. The resulting F(ab').sub.2 fragment can be treated to
reduce disulfide bridges to produce Fab' fragments. The antibody of the
invention is further intended to include bispecific and chimeric molecules
having an anti-S. epidermidis portion.
Both monoclonal and polyclonal antibodies (Ab) directed against S.
epidermidis polypeptides or S. epidermidis polypeptide variants, and
antibody fragments such as Fab' and F(ab').sub.2, can be used to block the
action of S. epidermidis polypeptide and allow the study of the role of a
particular S. epidermidis polypeptide of the invention in aberrant or
unwanted intracellular signaling, as well as the normal cellular function of
the S. epidermidis and by microinjection of anti-S. epidermidis polypeptide
antibodies of the present invention.
Antibodies which specifically bind S. epidermidis epitopes can also be used
in immunohistochemical staining of tissue samples in order to evaluate the
abundance and pattern of expression of S. epidermidis antigens. Anti-S.
epidermidis polypeptide antibodies can be used diagnostically in immuno-precipitation
and immuno-blotting to detect and evaluate S. epidermidis levels in tissue
or bodily fluid as part of a clinical testing procedure: Likewise, the
ability to monitor S. epidermidis polypeptide levels in an individual can
allow determination of the efficacy of a given treatment regimen for an
individual afflicted with such a disorder. The level of a S. epidermidis
polypeptide can be measured in cells found in bodily fluid, such as in urine
samples or can be measured in tissue, such as produced by gastric biopsy.
Diagnostic assays using anti-S. epidermidis antibodies can include, for
example, immunoassays designed to aid in early diagnosis of S. epidermidis
infections. The present invention can also be used as a method of detecting
antibodies contained in samples from individuals infected by this bacterium
using specific S. epidermidis antigens.
Another application of anti-S. epidermidis polypeptide antibodies of the
invention is in the immunological screening of cDNA libraries constructed in
expression vectors such as .lamda.gt11, .lamda.gt18-23, .lamda.ZAP, and
.lamda.ORF8. Messenger libraries of this type, having coding sequences
inserted in the correct reading frame and orientation, can produce fusion
proteins. For instance, .lamda.gt11 will produce fusion proteins whose amino
termini consist of .beta.-galactosidase amino acid sequences and whose
carboxy termini consist of a foreign polypeptide. Antigenic epitopes of a
subject S. epidermidis polypeptide can then be detected with antibodies, as,
for example, reacting nitrocellulose filters lifted from infected plates
with anti-S. epidermidis polypeptide antibodies: Phage, scored by this
assay, can then be isolated from the infected plate. Thus, the presence of
S. epidermidis gene homologs can be detected and cloned from other species,
and alternate isoforms (including splicing variants) can be detected and
Kits Containing Nucleic Acids, Polypeptides or Antibodies of the Invention
The nucleic acid, polypeptides and antibodies of the invention can be
combined with other reagents and articles to form kits. Kits for diagnostic
purposes typically comprise the nucleic acid, polypeptides or antibodies in
vials or other suitable vessels. Kits typically comprise other reagents for
performing hybridization reactions, polymerase chain reactions (PCR), or for
reconstitution of lyophilized components, such as aqueous media, salts,
buffers, and the like. Kits may also comprise reagents for sample processing
such as detergents, chaotropic salts and the like. Kits may also comprise
immobilization means such as particles, supports, wells, dipsticks and the
like. Kits may also comprise labeling means such as dyes, developing
reagents, radioisotopes, fluorescent agents, luminescent or chemiluminescent
agents, enzymes, intercalating agents and the like. With the nucleic acid
and amino acid sequence information provided herein, individuals skilled in
art can readily assemble kits to serve their particular purpose. Kits
further can include instructions for use.
Drug Screening Assays Using S. epidermidis Polypeptides
By making available purified and recombinant S. epidermidis polypeptides,
the present invention provides assays which can be used to screen for drugs
which are either agonists or antagonists of the normal cellular function, in
this case, of the subject S. epidermidis polypeptides, or of their role in
intracellular signaling. Such inhibitors or potentiators may be useful as
new therapeutic agents to combat S. epidermidis infections in humans. A
variety of assay formats will suffice and, in light of the present
inventions, will be comprehended by the person skilled in the art.
In many drug screening programs which test libraries of compounds and
natural extracts, high throughput assays are desirable in order to maximize
the number of compounds surveyed in a given period of time. Assays which are
performed in cell-free systems, such as may be derived with purified or
semi-purified proteins, are often preferred as "primary" screens in that
they can be generated to permit rapid development and relatively easy
detection of an alteration in a molecular target which is mediated by a test
compound. Moreover, the effects of cellular toxicity and/or bioavailability
of the test compound can be generally ignored in the in vitro system, the
assay instead being focused primarily on the effect of the drug on the
molecular target as may be manifest in an alteration of binding affinity
with other proteins or change in enzymatic properties of the molecular
target. Accordingly, in an exemplary screening assay of the present
invention, the compound of interest is contacted with an isolated and
purified S. epidermidis polypeptide.
Screening assays can be constructed in vitro with a purified S. epidermidis
polypeptide or fragment thereof, such as a S. epidermidis polypeptide having
enzymatic activity, such that the activity of the polypeptide produces a
detectable reaction product. The efficacy of the compound can be assessed by
generating dose response curves from data obtained using various
concentrations of the test compound. Moreover, a control assay can also be
performed to provide a baseline for comparison. Suitable products include
those with distinctive absorption, fluorescence, or chemi-luminescence
properties, for example, because detection may be easily automated. A
variety of synthetic or naturally occurring compounds can be tested in the
assay to identify those which inhibit or potentiate the activity of the S.
epidermidis polypeptide. Some of these active compounds may directly, or
with chemical alterations to promote membrane permeability or solubility,
also inhibit or potentiate the same activity (e.g., enzymatic activity) in
whole, live S. epidermidis cells.
Overexpression assays are based on the premise that overproduction of a
protein would lead to a higher level of resistance to compounds that
selectively interfere with the function of that protein. Overexpression
assays may be used to identify compounds that interfere with the function of
virtually any type of protein, including without limitation enzymes,
receptors, DNA- or RNA-binding proteins, or any proteins that are directly
or indirectly involved in regulating cell growth.
Typically, two bacterial strains are constructed. One contains a single copy
of the gene of interest, and a second contains several copies of the same
gene. Identification of useful inhibitory compounds of this type of assay is
based on a comparison of the activity of a test compound in inhibiting
growth and/or viability of the two strains. The method involves constructing
a nucleic acid vector that directs high level expression of a particular
target nucleic acid. The vectors are then transformed into host cells in
single or multiple copies to produce strains that express low to moderate
and high levels of protein encoding by the target sequence (strain A and B,
respectively). Nucleic acid comprising sequences encoding the target gene
can, of course, be directly integrated into the host cell.
Large numbers of compounds (or crude substances which may contain active
compounds) are screened for their effect on the growth of the two strains.
Agents which interfere with an unrelated target equally inhibit the growth
of both strains. Agents which interfere with the function of the target at
high concentration should inhibit the growth of both strains. It should be
possible, however, to titrate out the inhibitory effect of the compound in
the overexpressing strain. That is, if the compound is affecting the
particular target that is being tested, it should be possible to inhibit the
growth of strain A at a concentration of the compound that allows strain B
Alternatively, a bacterial strain is constructed that contains the gene of
interest under the control of an inducible promoter. Identification of
useful inhibitory agents using this type of assay is based on a comparison
of the activity of a test compound in inhibiting growth and/or viability of
this strain under both inducing and non-inducing conditions. The method
involves constructing a nucleic acid vector that directs high-level
expression of a particular target nucleic acid. The vector is then
transformed into host cells that are grown under both non-inducing and
inducing conditions (conditions A and B, respectively).
Large numbers of compounds (or crude substances which may contain active
compounds) are screened for their effect on growth under these two
conditions. Agents that interfere with the function of the target should
inhibit growth under both conditions. It should be possible, however, to
titrate out the inhibitory effect of the compound in the overexpressing
strain. That is, if the compound is affecting the particular target that is
being tested, it should be possible to inhibit growth under condition A at a
concentration that allows the strain to grow under condition B.
Many of the targets according to the invention have functions that have not
yet been identified. Ligand-binding assays are useful to identify inhibitor
compounds that interfere with the function of a particular target, even when
that function is unknown. These assays are designed to detect binding of
test compounds to particular targets. The detection may involve direct
measurement of binding. Alternatively, indirect indications of binding may
involve stabilization of protein structure or disruption of a biological
function. Non-limiting examples of useful ligand-binding assays are detailed
A useful method for the detection and isolation of binding proteins is the
Biomolecular Interaction Assay (BIAcore) system developed by Pharmacia
Biosensor and described in the manufacturer's protocol (LKB Pharmacia,
Sweden). The BIAcore system uses an affinity purified anti-GST antibody to
immobilize OST-fusion proteins onto a sensor chip. The sensor utilizes
surface plasmon resonance which is an optical phenomenon that detects
changes in refractive indices. In accordance with the practice of the
invention, a protein of interest is coated onto a chip and test compounds
are passed over the chip. Binding is detected by a change in the refractive
index (surface plasmon resonance).
A different type of ligand-binding assay involves scintillation proximity
assays (SPA, described in U.S. Pat. No. 4,568,649).
Another type of ligand binding assay, also undergoing development, is based
on the fact that proteins containing mitochondrial targeting signals are
imported into isolated mitochondria in vitro (Hurt et al., 1985, Embo J.
4:2061-2068; Eilers and Schatz, Nature, 1986, 322:228-231). In a
mitochondrial import assay, expression vectors are constructed in which
nucleic acids encoding particular target proteins are inserted downstream of
sequences encoding mitochondrial import signals. The chimeric proteins are
synthesized and tested for their ability to be imported into isolated
mitochondria in the absence and presence of test compounds. A test compound
that binds to the target protein should inhibit its uptake into isolated
mitochondria in vitro.
Another ligand-binding assay is the yeast two-hybrid system (Fields and
Song, 1989, Nature 340:245-246). The yeast two-hybrid system takes advantage
of the properties of the GAL4 protein of the yeast Saccharomyces cerevisiae.
The GAL4 protein is a transcriptional activator required for the expression
of genes encoding enzymes of galactose utilization. This protein consists of
two separable and functionally essential domains: an N-terminal domain which
binds to specific DNA sequences (UAS.sub.G); and a C-terminal domain
containing acidic regions, which is necessary to activate transcription. The
native GAL4 protein, containing both domains, is a potent activator of
transcription when yeast are grown on galactose media. The N-terminal domain
binds DNA in a sequence-specific manner but is unable to activate
transcription. The C-terminal domain contains the activating regions but
cannot activate transcription because it fails to be localized to UAS.sub.G.
In the two-hybrid system, a system of two hybrid proteins containing parts
of GAL4: (1) a GAL4 DNA-binding domain fused to a protein `X` and (2) a GAL4
activation region fused to a protein `Y`. If X and Y can form a
protein-protein complex and reconstitute proximity of the GAL4 domains,
transcription of a gene regulated by UAS.sub.G occurs. Creation of two
hybrid proteins, each containing one of the interacting proteins X and Y,
allows the activation region of UAS.sub.G to be brought to its normal site
The binding assay described in Fodor et al., 1991, Science 251:767-773,
which involves testing the binding affinity of test compounds for a
plurality of defined polymers synthesized on a solid substrate, may also be
Compounds which bind to the polypeptides of the invention are potentially
useful as antibacterial agents for use in therapeutic compositions.
Pharmaceutical formulations suitable for antibacterial therapy comprise the
antibacterial agent in conjunction with one or more biologically acceptable
carriers. Suitable biologically acceptable carriers include, but are not
limited to, phosphate-buffered saline, saline, deionized water, or the like.
Preferred biologically acceptable carriers are physiologically or
pharmaceutically acceptable carriers.
The antibacterial compositions include an antibacterial effective amount of
active agent. Antibacterial effective amounts are those quantities of the
antibacterial agents of the present invention that afford prophylactic
protection against bacterial infections or which result in amelioration or
cure of an existing bacterial infection. This antibacterial effective amount
will depend upon the agent, the location and nature of the infection, and
the particular host. The amount can be determined by experimentation known
in the art, such as by establishing a matrix of dosages and frequencies and
comparing a group of experimental units or subjects to each point in the
The antibacterial active agents or compositions can be formed into dosage
unit forms, such as for example, creams, ointments, lotions, powders,
liquids, tablets, capsules, suppositories, sprays, aerosols or the like. If
the antibacterial composition is formulated into a dosage unit form, the
dosage unit form may contain an antibacterial effective amount of active
agent. Alternatively, the dosage unit form may include less than such an
amount if multiple dosage unit forms or multiple dosages are to be used to
administer a total dosage of the active agent. Dosage unit forms can
include, in addition, one or more excipient(s), diluent(s), disintegrant(s),
lubricant(s)., plasticizer(s), colorant(s), dosage vehicle(s), absorption
enhancer(s), stabilizer(s), bactericide(s), or the like.
For general information concerning formulations, see, e.g., Gilman et al.
(eds.), 1990, Goodman and Gilman's: The Pharmacological Basis of
Therapeutics, 8th ed., Pergamon Press; and Remington's Pharmaceutical
Sciences, 17th ed., 1990, Mack Publishing Co., Easton, Pa.; Avis et al.
(eds.), 1993, Pharmaceutical Dosage Forms: Parenteral Medications, Dekker,
New York; Lieberman et al (eds.), 1990, Pharmaceutical Dosage Forms.
Disperse Systems, Dekker, New York.
The antibacterial agents and compositions of the present invention are
useful for preventing or treating S. epidermidis infections. Infection
prevention methods incorporate a prophylactically effective amount of an
antibacterial agent or composition. A prophylactically effective amount is
an amount effective to prevent S. epidermidis infection and will depend upon
the specific bacterial strain, the agent, and the host. These amounts can be
determined experimentally by methods known in the art and as described
S. epidermidis infection treatment methods incorporate a therapeutically
effective amount of an antibacterial agent or composition. A therapeutically
effective amount is an amount sufficient to ameliorate or eliminate the
infection. The prophylactically and/or therapeutically effective amounts can
be administered in one administration or over repeated administrations.
Therapeutic administration can be followed by prophylactic administration,
once the initial bacterial infection has been resolved.
The antibacterial agents and compositions can be administered topically or
systemically. Topical application is typically achieved by administration of
creams, ointments, lotions, or sprays as described above. Systemic
administration includes both oral and parental routes. Parental routes
include, without limitation, subcutaneous, intramuscular, intraperitoneal,
intravenous, transdermal, inhalation and intranasal administration.
Claim 1 of 10 Claims
1. An isolated nucleic acid molecule
encoding the S. epidermidis polypeptide of SEQ ID NO: 5277.
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