Title: Leishmania antigens for use in the therapy and diagnosis of leishmaniasis
United States Patent: 6,638,517
Issued: October 28, 2003
Inventors: Reed; Steven G. (Bellevue, WA); Campos-Neto; Antonio (Bainbridge Island, WA); Webb; John R. (Manotick, CA); Dillon; Davin C. (Issaquah, WA); Skeiky; Yasir A. W. (Bellevue, WA); Bhatia; Ajay (Seattle, WA); Coler; Rhea N. (Seattle, WA); Probst; Peter (Seattle, WA); Brannon; Mark (Seattle, WA)
Assignee: Corixa Corporation (Seattle, WA)
Appl. No.: 874923
Filed: June 4, 2001
Compositions and methods for preventing, treating and detecting leishmaniasis and stimulating immune responses in patients are disclosed. The compounds provided include polypeptides that contain at least an immunogenic portion of one or more Leishmania antigens, or a variant thereof. Vaccines and pharmaceutical compositions comprising such polypeptides, or polynucleotides encoding such polypeptides, are also provided and may be used, for example, for the prevention and therapy of leishmaniasis, as well as for the detection of Leishmania infection.
SUMMARY OF THE INVENTION
Briefly stated, the present invention provides compositions and methods for preventing, treating and detecting leishmaniasis, as well as for stimulating immune responses in patients. In one aspect, polypeptides are provided which comprise at least an immunogenic portion of a Leishmania antigen, or a variant of such an antigen that differs only in conservative substitutions and/or modifications. In specific embodiments of the invention, the Leishmania antigen comprises an amino acid sequence selected from the group consisting of SEQ ID NO: 2, 4, 20, 22, 24, 26, 36-38, 41, 50-53, 82, 104, 106, 108, 110, 112 and 118-122,. DNA sequences encoding the above polypeptides, recombinant expression vectors comprising these DNA sequences and host cells transformed or transfected with such expression vectors are also provided.
In further aspects, the present invention provides fusion proteins comprising Leishmania antigens, together with polynucleotides encoding such fusion proteins. In certain specific embodiments, such fusion proteins comprise an amino acid sequence selected from the group consisting of SEQ ID NOs:95, 96, and 97 and encoded by a polynucleotide sequence selected from the group consisting of SEQ ID NOs:94, 98, 99, 100, and 101.
In related aspects, the present invention provides pharmaceutical compositions which comprise one or more of the polypeptides and/or fusion proteins described herein, or a polynucleotide encoding such polypeptides and fusion proteins, and a physiologically acceptable carrier. Vaccines which comprise one or more such polypeptides, fusion proteins or polynucleotides, together with an immunostimulant are also provided. In specific embodiments of these aspects, the Leishmania antigen has an amino acid sequence selected from the group consisting of SEQ ID NO: 2, 4, 20, 22, 24, 26, 36-38, 41, 50-53, 82, 104, 106, 108, 110, 112 and 118-122.
In still further related embodiments, the pharmaceutical compositions and vaccines comprise at least two different polypeptides, each polypeptide comprising an immunogenic portion of a Leishmania antigen having an amino acid sequence selected from the group consisting of sequences recited in SEQ ID NO: 2, 4, 6, 8, 10, 20, 22, 24, 26, 36-38, 41, 50-53, 82, 104, 106, 108, 110, 112 and 118-122, and variants thereof that differ only in conservative substitutions and/or modifications. In other embodiments, the inventive pharmaceutical compositions comprise one or more of the inventive polypeptides in combination with a known Leishmania antigen.
In yet other related embodiments, the pharmaceutical compositions and vaccines comprise soluble Leishmania antigens.
In another aspect, the present invention provides methods for inducing protective immunity against leishmaniasis in a patient, comprising administering to a patient a pharmaceutical composition or vaccine as described above.
In further aspects, methods and diagnostic kits are provided for detecting Leishmania infection in a patient. The methods comprise: (a) contacting dermal cells of a patient with a pharmaceutical composition as described above; and (b) detecting an immune response on the patient's skin, therefrom detecting Leishmania infection in the patient. The diagnostic kits comprise: (a) a pharmaceutical composition as described above; and (b) an apparatus sufficient to contact the pharmaceutical composition with the dermal cells of a patient.
In further aspects, the present invention provides methods for stimulating a cellular and/or humoral immune response in a patient, comprising administering to a patient a pharmaceutical composition or vaccine as described above.
In a related aspect, methods are provided for treating a patient afflicted with a disease responsive to IL-12 stimulation, comprising administering to a patient a pharmaceutical composition or vaccine as described above.
These and other aspects of the present invention will become apparent upon reference to the following detailed description and attached drawings. All references disclosed herein are hereby incorporated by reference in their entirety as if each was incorporated individually.
DETAILED DESCRIPTION OF THE INVENTION
As noted above, the present invention is generally directed to compositions and methods for preventing, treating and detecting leishmaniasis, as well as for stimulating immune responses in patients. The compositions of the subject invention include polypeptides that comprise at least an immunogenic portion of a Leishmania antigen, or a variant of such an antigen. In one preferred embodiment, compositions of the present invention include multiple polypeptides selected so as to provide enhanced protection against a variety of Leishmania species.
Polypeptides within the scope of the present invention include, but are not limited to, polypeptides comprising immunogenic portions of Leishmania antigens comprising the sequences recited in SEQ ID NO:2 (referred to herein as M15), SEQ ID NO:4 (referred to herein as Ldp23), SEQ ID NO:6 (referred to herein as Lbhsp83), SEQ ID NO:8 (referred to herein as Lt-210), SEQ ID NO:10 (referred to herein as LbeIF4A), SEQ ID NO: 20 (referred to herein as Lmspla), SEQ ID NO: 22 (referred to herein as Lmsp9a), SEQ ID NOs: 24 and 26 (referred to herein as MAPS-1A), and SEQ ID NO: 36-38, 41, 50-53, 82, 104, 106, 108, 110, 112 and 118-122. As used herein, the term "polypeptide" encompasses amino acid chains of any length, including full length proteins (i.e., antigens), wherein the amino acid residues are linked by covalent bonds. Thus, a polypeptide comprising an immunogenic portion of one of the above antigens may consist entirely of the immunogenic portion, or may contain additional sequences. The additional sequences may be derived from the native Leishmania antigen or may be heterologous, and such sequences may (but need not) be immunogenic. An antigen "having" a particular sequence is an antigen that contains, within its full length sequence, the recited sequence. The native antigen may, or may not, contain additional amino acid sequence.
An immunogenic portion of a Leishmania antigen is a portion that is capable of eliciting an immune response (i.e., cellular and/or humoral) in a presently or previously Leishmania-infected patient (such as a human or a dog) and/or in cultures of lymph node cells or peripheral blood mononuclear cells (PBMC) isolated from presently or previously Leishmania-infected individuals. The cells in which a response is elicited may comprise a mixture of cell types or may contain isolated component cells (including, but not limited to, T-cells, NK cells, macrophages, monocytes and/or B cells). In particular, immunogenic portions are capable of inducing T-cell proliferation and/or a dominantly Th1-type cytokine response (e.g., IL-2, IFN-.gamma., and/or TNF-.alpha. production by T-cells and/or NK cells; and/or IL-12 production by monocytes, macrophages and/or B cells). Immunogenic portions of the antigens described herein may generally be identified using techniques known to those of ordinary skill in the art, including the representative methods provided herein.
The compositions and methods of the present invention also encompass variants of the above polypeptides. A polypeptide "variant," as used herein, is a polypeptide that differs from a native protein in one or more substitutions, deletions, additions and/or insertions, such that the immunogenicity of the polypeptide is not substantially diminished. In other words, the ability of a variant to react with antigen-specific antisera may be enhanced or unchanged, relative to the native protein, or may be diminished by less than 50%, and preferably less than 20%, relative to the native protein. Such variants may generally be identified by modifying one of the above polypeptide sequences and evaluating the reactivity of the modified polypeptide with antigen-specific antibodies or antisera as described herein. Preferred variants include those in which one or more portions, such as an N-terminal leader sequence or transmembrane domain, have been removed. Other preferred variants include variants in which a small portion (e.g., 1-30 amino acids, preferably 5-15 amino acids) has been removed from the N- and/or C-terminal of the mature protein.
Polypeptide variants encompassed by the present invention include those exhibiting at least about 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more identity (determined as described below) to the polypeptides disclosed herein.
Preferably, a variant contains conservative substitutions. A "conservative substitution" is one in which an amino acid is substituted for another amino acid that has similar properties, such that one skilled in the art of peptide chemistry would expect the secondary structure and hydropathic nature of the polypeptide to be substantially unchanged. Amino acid substitutions may generally be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity and/or the amphipathic nature of the residues. For example, negatively charged amino acids include aspartic acid and glutamic acid; positively charged amino acids include lysine and arginine; and amino acids with uncharged polar head groups having similar hydrophilicity values include leucine, isoleucine and valine; glycine and alanine; asparagine and glutamine; and serine, threonine, phenylalanine and tyrosine. Other groups of amino acids that may represent conservative changes include: (1) ala, pro, gly, glu, asp, gln, asn, ser, thr; (2) cys, ser, tyr, thr; (3) val, ile, leu, met, ala, phe; (4) lys, arg, his; and (5) phe, tyr, trp, his. A variant may also, or alternatively, contain nonconservative changes. In a preferred embodiment, variant polypeptides differ from a native sequence by substitution, deletion or addition of five amino acids or fewer. Variants may also (or alternatively) be modified by, for example, the deletion or addition of amino acids that have minimal influence on the immunogenicity, secondary structure and hydropathic nature of the polypeptide.
Polynucleotides may comprise a native sequence (i.e., an endogenous sequence that encodes a protein or a portion thereof) or may comprise a variant, or a biological or antigenic functional equivalent of such a sequence. Polynucleotide variants may contain one or more substitutions, additions, deletions and/or insertions, as further described below, preferably such that the immunogenicity of the encoded polypeptide is not diminished, relative to a native tumor protein. The effect on the immunogenicity of the encoded polypeptide may generally be assessed as described herein. The term "variants" also encompasses homologous genes of xenogenic origin.
When comparing polynucleotide or polypeptide sequences, two sequences are said to be "identical" if the sequence of nucleotides or amino acids in the two sequences is the same when aligned for maximum correspondence, as described below. Comparisons between two sequences are typically performed by comparing the sequences over a comparison window to identify and compare local regions of sequence similarity. A "comparison window" as used herein, refers to a segment of at least about 20 contiguous positions, usually 30 to about 75, 40 to about 50, in which a sequence may be compared to a reference sequence of the same number of contiguous positions after the two sequences are optimally aligned.
Optimal alignment of sequences for comparison may be conducted using the Megalign program in the Lasergene suite of bioinformatics software (DNASTAR, Inc., Madison, Wis.), using default parameters. This program embodies several alignment schemes described in the following references: Dayhoff, M. O. (1978) A model of evolutionary change in proteins--Matrices for detecting distant relationships. In Dayhoff, M. O. (ed.) Atlas of Protein Sequence and Structure, National Biomedical Research Foundation, Washington D.C. Vol. 5, Suppl. 3, pp. 345-358; Hein J. (1990) Unified Approach to Alignment and Phylogenes pp. 626-645 Methods in Enzymology vol. 183, Academic Press, Inc., San Diego, Calif.; Higgins, D. G. and Sharp, P. M. (1989) CABIOS 5:151-153; Myers, E. W. and Muller W. (1988) CABIOS 4:11-17; Robinson, E. D. (1971) Comb. Theor 11:105; Santou, N. Nes, M. (1987) Mol. Biol. Evol. 4:406-425; Sneath, P. H. A. and Sokal, R. R. (1973) Numerical Taxonomy--the Principles and Practice of Numerical Taxonomy, Freeman Press, San Francisco, Calif.; Wilbur, W. J. and Lipman, D. J. (1983) Proc. Natl. Acad., Sci. USA 80:726-730.
Alternatively, optimal alignment of sequences for comparison may be conducted by the local identity algorithm of Smith and Waterman (1981) Add. APL. Math 2:482, by the identity alignment algorithm of Needleman and Wunsch (1970) J. Mol. Biol. 48:443, by the search for similarity methods of Pearson and Lipman (1988) Proc. Natl. Acad. Sci. USA 85: 2444, by computerized implementations of these algorithms (GAP, BESTFIT, BLAST, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group (GCG), 575 Science Dr., Madison, Wis.), or by inspection.
One preferred example of algorithms that are suitable for determining percent sequence identity and sequence similarity are the BLAST and BLAST 2.0 algorithms, which are described in Altschul et al. (1977) Nucl. Acids Res. 25:3389-3402 and Altschul et al. (1990) J. Mol. Biol. 215:403-410, respectively. BLAST and BLAST 2.0 can be used, for example with the parameters described herein, to determine percent sequence identity for the polynucleotides and polypeptides of the invention. Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information. In one illustrative example, cumulative scores can be calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always >0) and N (penalty score for mismatching residues; always <0). For amino acid sequences, a scoring matrix can be used to calculate the cumulative score. Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. The BLAST algorithm parameters W, T and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a wordlength (W) of 11, and expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff and Henikoff (1989) Proc. Natl. Acad. Sci. USA 89:10915) alignments, (B) of 50, expectation (E) of 10, M=5, N=-4 and a comparison of both strands.
Preferably, the "percentage of sequence identity" is determined by comparing two optimally aligned sequences over a window of comparison of at least 20 positions, wherein the portion of the polynucleotide or polypeptide sequence in the comparison window may comprise additions or deletions (i.e., gaps) of 20 percent or less, usually 5 to 15 percent, or 10 to 12 percent, as compared to the reference sequences (which does not comprise additions or deletions) for optimal alignment of the two sequences. The percentage is calculated by determining the number of positions at which the identical nucleic acid bases or amino acid residue occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the reference sequence (i.e., the window size) and multiplying the results by 100 to yield the percentage of sequence identity.
Therefore, the present invention encompasses polynucleotide and polypeptide sequences having substantial identity to the sequences disclosed herein, for example those comprising at least 50% sequence identity, preferably at least 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% or higher, sequence identity compared to a polynucleotide or polypeptide sequence of this invention using the methods described herein, (e.g., BLAST analysis using standard parameters, as described below). One skilled in this art will recognize that these values can be appropriately adjusted to determine corresponding identity of proteins encoded by two nucleotide sequences by taking into account codon degeneracy, amino acid similarity, reading frame positioning and the like.
In additional embodiments, the present invention provides isolated polynucleotides and polypeptides comprising various lengths of contiguous stretches of sequence identical to or complementary to one or more of the sequences disclosed herein. For example, polynucleotides are provided by this invention that comprise at least about 15, 20, 30, 40, 50, 75, 100, 150, 200, 300, 400, 500 or 1000 or more contiguous nucleotides of one or more of the sequences disclosed herein as well as all intermediate lengths there between. It will be readily understood that "intermediate lengths", in this context, means any length between the quoted values, such as 16, 17, 18, 19, etc.; 21, 22, 23, etc.; 30, 31, 32, etc.; 50, 51, 52, 53, etc.; 100, 101, 102, 103, etc.; 150, 151, 152, 153, etc.; including all integers through 200-500; 500-1,000, and the like.
The polynucleotides of the present invention, or fragments thereof, regardless of the length of the coding sequence itself, may be combined with other DNA sequences, such as promoters, polyadenylation signals, additional restriction enzyme sites, multiple cloning sites, other coding segments, and the like, such that their overall length may vary considerably. It is therefore contemplated that a nucleic acid fragment of almost any length may be employed, with the total length preferably being limited by the ease of preparation and use in the intended recombinant DNA protocol. For example, illustrative DNA segments with total lengths of about 10,000, about 5000, about 3000, about 2,000, about 1,000, about 500, about 200, about 100, about 50 base pairs in length, and the like, (including all intermediate lengths) are contemplated to be useful in many implementations of this invention.
In other embodiments, the present invention is directed to polynucleotides that are capable of hybridizing under moderately stringent conditions to a polynucleotide sequence provided herein, or a fragment thereof, or a complementary sequence thereof. Hybridization techniques are well known in the art of molecular biology. For purposes of illustration, suitable moderately stringent conditions for testing the hybridization of a polynucleotide of this invention with other polynucleotides include prewashing in a solution of 5x SSC, 0.5% SDS, 1.0 mM EDTA (pH 8.0); hybridizing at 50oC-65oC., 5x SSC, overnight; followed by washing twice at 65oC. for 20 minutes with each of 2x, 0.5x and 0.2x SSC containing 0.1% SDS.
Moreover, it will be appreciated by those of ordinary skill in the art that, as a result of the degeneracy of the genetic code, there are many nucleotide sequences that encode a polypeptide as described herein. Some of these polynucleotides bear minimal homology to the nucleotide sequence of any native gene. Nonetheless, polynucleotides that vary due to differences in codon usage are specifically contemplated by the present invention. Further, alleles of the genes comprising the polynucleotide sequences provided herein are within the scope of the present invention. Alleles are endogenous genes that are altered as a result of one or more mutations, such as deletions, additions and/or substitutions of nucleotides. The resulting mRNA and protein may, but need not, have an altered structure or function. Alleles may be identified using standard techniques (such as hybridization, amplification and/or database sequence comparison).
"Polypeptides" as described herein also include combination polypeptides, also referred to as fusion proteins. A "combination polypeptide" is a polypeptide comprising at least one of the above immunogenic portions and one or more additional immunogenic Leishmania sequences, which are joined via a peptide linkage into a single amino acid chain. The sequences may be joined directly (i.e., with no intervening amino acids) or may be joined by way of a linker sequence (e.g., Gly-Cys-Gly) that does not significantly diminish the immunogenic properties of the component polypeptides.
Fusion proteins may generally be prepared using standard techniques, including chemical conjugation. Preferably, a fusion protein is expressed as a recombinant protein, allowing the production of increased levels, relative to a non-fused protein, in an expression system. Briefly, DNA sequences encoding the polypeptide components may be assembled separately, and ligated into an appropriate expression vector. The 3' end of the DNA sequence encoding one polypeptide component is ligated, with or without a peptide linker, to the 5' end of a DNA sequence encoding the second polypeptide component so that the reading frames of the sequences are in frame. This permits translation into a single fusion protein that retains the biological activity of both component polypeptides.
A peptide linker sequence may be employed to separate the first and the second polypeptide components by a distance sufficient to ensure that each polypeptide folds into its secondary and tertiary structures. Such a peptide linker sequence is incorporated into the fusion protein using standard techniques well known in the art. Suitable peptide linker sequences may be chosen based on the following factors: (1) their ability to adopt a flexible extended conformation; (2) their inability to adopt a secondary structure that could interact with functional epitopes on the first and second polypeptides; and (3) the lack of hydrophobic or charged residues that might react with the polypeptide functional epitopes. Preferred peptide linker sequences contain Gly, Asn and Ser residues. Other near neutral amino acids, such as Thr and Ala may also be used in the linker sequence. Amino acid sequences which may be usefully employed as linkers include those disclosed in Maratea et al., Gene 40:39-46, 1985; Murphy et al., Proc. Natl. Acad Sci. USA 83:8258-8262, 1986; U.S. Pat. Nos. 4,935,233 and 4,751,180. The linker sequence may generally be from 1 to about 50 amino acids in length. Linker sequences are not required when the first and second polypeptides have non-essential N-terminal amino acid regions that can be used to separate the functional domains and prevent steric interference.
The ligated DNA sequences are operably linked to suitable transcriptional or translational regulatory elements. The regulatory elements responsible for expression of DNA are located only 5' to the DNA sequence encoding the first polypeptides. Similarly, stop codons required to end translation and transcription termination signals are only present 3' to the DNA sequence encoding the second polypeptide. The preparation of fusion proteins of Leishmania antigens is described in detail below in Example 19.
In general, Leishmania antigens having immunogenic properties, and DNA sequences encoding such antigens, may be prepared using any of a variety of procedures from one or more Leishmania species including, but not limited to, L. donovani, L. chagasi, L. infantum, L. major, L. amazonensis, L. braziliensis, L. panamensis, L. mexicana, L. tropica, and L. guyanensis. Such species are available, for example, from the American Type Culture Collection (ATCC), Rockville, Md. For example, peptides isolated from MHC class II molecules of macrophages infected with a Leishmania species may be used to rescue the corresponding Leishmania donor antigens. MHC class II molecules are expressed mainly by cells of the immune system, including macrophages. These molecules present peptides, which are usually 13-17 amino acids long, derived from foreign antigens that are degraded in cellular vesicles. The bound peptide antigens are then recognized by CD4 T-cells. Accordingly, foreign peptides isolated from MHC class II molecules of, for example, Leishmania-infected murine macrophages may be used to identify immunogenic Leishmania proteins.
Briefly, peptides derived from Leishmania antigens may be isolated by comparing the reverse phase HPLC profile of peptides extracted from infected macrophages with the profile of peptides extracted from uninfected cells. Peptides giving rise to distinct HPLC peaks unique to infected macrophages may then be sequenced using, for example, Edman chemistry as described in Edman and Berg, Eur J Biochem, 80:116-132 (1967). A DNA fragment corresponding to a portion of a Leishmania gene encoding the peptide may then be amplified from a Leishmania cDNA library using an oligonucleotide sense primer derived from the peptide sequence and an oligo dT antisense primer. The resulting DNA fragment may then be used as a probe to screen a Leishmania library for a full length cDNA or genomic clone that encodes the Leishmania antigen. Such screens may generally be performed using techniques well known to those of ordinary skill in the art, such as those described in Sambrook et al., Molecular Cloning: 4 Laboratory Manual, Cold Spring Harbor Laboratories, Cold Spring Harbor, N.Y. (1989).
This approach may be used to identify a 23 kD Leishmania donovani antigen (referred to herein as Ldp23). The sequence of a polynucleotide encoding Ldp23 is provided in SEQ ID NO:3 and the amino acid sequence of Ldp23 is provided in SEQ ID NO: A Using the methods described herein, Ldp23 has been shown to induce a Th1 immune response in T-cells prepared from Leishmania-infected mice.
Alternatively, a Leishmania cDNA or genomic expression library may be screened with serum from a Leishmania-infected individual, using techniques well known to those of ordinary skill in the art. Polynucleotides encoding reactive antigens may then be used to express the recombinant antigen for purification. The immunogenic properties of the purified Leishmania antigens may then be evaluated using, for example the representative methods described herein.
For example, sera from Leishmania-infected mice may be used to screen a cDNA library prepared from Leishmania amastigotes. Reactive clones may then be expressed and recombinant proteins assayed for the ability to stimulate T-cells or NK cells derived from Leishmania-immune individuals (i.e., individuals having evidence of infection, as documented by positive serological reactivity with Leishmania-specific antibodies and/or a Leishmania-specific DTH response, without clinical symptoms of leishmaniasis). This procedure may be used to obtain a recombinant polynucleotide encoding the Leishmania antigen designated M15. The sequence of such a polynucleotide is provided in SEQ ID NO:1, and the amino acid sequence of the encoded protein is provided in SEQ ID NO:2.
A similar approach may be used to isolate a genomic polynucleotide encoding an immunogenic Leishmania braziliensis antigen, referred to herein as Lbhsp83. More specifically, a genomic clone encoding Lbhsp83 may be isolated by screening a L. braziliensis expression library with sera from a Leishmania-infected individual. The DNA encoding Lbhsp83 is homologous to the gene encoding the eukaryotic 83 kD heat shock protein. The sequence of a polynucleotide encoding nearly all of Lbhsp83 is presented in SEQ ID NO:5, and the encoded amino acid sequence is provided in SEQ ID NO:6. Using the methods described below, Lbhsp83 has been found to stimulate proliferation, and a mixed Th1 and Th2 cytokine profile, in PBMC isolated from L. braziliensis-infected patients. Accordingly, Lbhsp83 is an immunogenic Leishmania antigen. Regions of Lbhsp83 that are not conserved with the mammalian gene have been found to be particularly potent for T-cell stimulation and antibody binding. Such regions may be identified, for example, by visual inspection of the sequence comparison.
This approach may also be used to isolate a polynucleotide encoding a 210 kD immunogenic L. tropica antigen, referred to herein as Lt-210. The preparation and characterization of Lt-210, and immunogenic portions thereof (such as Lt-1 and immunogenic repeat and non-repeat sequences), is described in detail in U.S. patent application Ser. No. 08/511,872, filed Aug. 4, 1995. The sequence of a polynucleotide encoding Lt-1 is provided in SEQ ID NO:7 and the encoded amino acid sequence is presented in SEQ ID NO:8.
The above approach may further be used to isolate a polynucleotide encoding a L. braziliensis antigen referred to herein as LbeIF4A. Briefly, such a clone may be isolated by screening a L. braziliensis expression library with sera obtained from a patient afflicted with mucosal leishmaniasis, and analyzing the reactive antigens for the ability to stimulate proliferative responses and preferential Th1 cytokine production in PBMC isolated from Leishmania-infected patients, as described below. The preparation and characterization of LbeIF4A is described in detail in U.S. patent application Ser. Nos. 08/454,036 and 08/488,386, which are continuations-in-part of U.S. patent application Ser. No. 08/232,534, filed Apr. 22, 1994. The sequence of a polynucleotide encoding LbeIF4A is provided in SEQ ID NO:9 and the encoded amino acid sequence is presented in SEQ ID NO:10. Homologs of LbeIF4A, such as that found in L. major, may also be isolated using this approach, and are within the scope of the present invention.
Compositions of the present invention may also, or alternatively, contain soluble Leishmania antigens. As used herein, "soluble Leishmania antigens" refers to a mixture of at least 8 different Leishmania antigens that may be isolated from the supernatant of Leishmania promastigotes of any species grown for 8-12 hours in protein-free medium. Briefly, the organisms are grown to late log phase in complex medium with serum until they reach a density of 2-3x107 viable organisms per mL of medium. The organisms are thoroughly washed to remove medium components and resuspended at 2-3x107 viable organisms per mL of defined serum-free medium consisting of equal parts RPMI 1640 and medium 199, both from Gibco BRL, Gaithersburg, Md. After 8-12 hours, the supernatant containing soluble Leishmania antigens is removed, concentrated 10 fold and dialyzed against phosphate-buffered saline for 24 hours. The presence of at least eight different antigens within the mixture of Leishmania antigens may be confirmed using SDS-PAGE (i.e., through the observation of at least 8 different bands). The immunogenic properties of the soluble Leishmania antigens may be confirmed by evaluating the ability of the preparation to elicit an immune response in cultures of lymph node cells and/or peripheral blood mononuclear cells (PBMC) isolated from presently or previously Leishmania-infected individuals. Such an evaluation may be performed as described below.
Individual antigens present within the mixture of soluble Leishmania antigens may be isolated by immunizing mice or rabbits with Leishmania culture supernatant, containing soluble antigens, and employing the resultant sera to screen a Leishmania cDNA expression library as described in detail below. This procedure may be used to isolate recombinant polynucleotides encoding the L. major antigens referred to herein as Lmsp1a, Lmsp9a and MAPS-1A. DNA sequences encoding Lmsp1a, Lmsp9a and MAPS-1A are provided in SEQ ID NO: 19, 21 and 23, respectively, with the corresponding predicted amino acid sequences being presented in SEQ ID NO: 20, 22 and 24, respectively. Similarly, sera from mice or rabbits immunized with L. major culture supernatant may be used to screen an L. major genomic DNA library. As detailed below, this procedure may be used to isolate polynucleotides encoding the L. major antigens referred to herein as LmgSP1, LmgSP3, LmgSP5, LmgSP8, LmgSP9, LmgSP13, LmgSP19, and polynucleotides encoding the L. chagasi antigens LcgSP1, LcgSP3, LcgSP4, LcgSP8, and LcgSP10. The DNA sequences encoding these antigens are provided in SEQ ID NO:29-35 and 44-48, respectively, with the corresponding amino acid sequences being provided in SEQ ID NO: 36-42 and 49-53. The L. major antigens referred to herein as 1G6-34, 1E6-44, 4A5-63, 1B11-39, 2A10-37, 4G2-83, 4H6-41 and 8G3-100 may be isolated by means of CD4+ T cell expression cloning as described below. DNA sequences encoding these antigens are provided in SEQ ID NO: 72-79, respectively, with the corresponding predicted amino acid sequences being provided in SEQ ID NO: 80-87. The immunogenic properties of the isolated Leishmania antigens may be evaluated using, for example, the representative methods described herein.
Regardless of the method of preparation, the antigens described herein are immunogenic. In other words, the antigens (and immunogenic portions thereof) are capable of eliciting an immune response in cultures of lymph node cells and/or peripheral blood mononuclear cells (PBMC) isolated from presently or previously Leishmania- infected individuals. More specifically, the antigens, and immunogenic portions thereof, have the ability to induce T-cell proliferation and/or to elicit a dominantly Th1-type cytokine response (e.g., IL-2, IFN-.gamma., and/or TNF-.alpha. production by T-cells and/or NK cells; and/or IL-12 production by monocytes, macrophages and/or B cells) in cells isolated from presently or previously Leishmania-infected individuals. A Leishmania-infected individual may be afflicted with a form of leishmaniasis (such as subclinical, cutaneous, mucosal or active visceral) or may be asymptomatic. Such individuals may be identified using methods known to those of ordinary skill in the art. Individuals with leishmaniasis may be identified based on clinical findings associated with at least one of the following: isolation of parasite from lesions, a positive skin test with Leishmania lysate or a positive serological test. Asymptomatic individuals are infected individuals who have no signs or symptoms of the disease. Such individuals can be identified based on a positive serological test and/or skin test with Leishmania lysate.
The term "PBMC," which refers to a preparation of nucleated cells consisting primarily of lymphocytes and monocytes that are present in peripheral blood, encompasses both mixtures of cells and preparations of one or more purified cell types. PBMC may be isolated by methods known to those in the art. For example, PBMC may be isolated by density centrifugation through, for example, Ficoll.TM. (Winthrop Laboratories, New York). Lymph node cultures may generally be prepared by immunizing BALB/c mice (e.g., in the rear foot pad) with Leishmania promastigotes emulsified in complete Freund's adjuvant. The draining lymph nodes may be excised following immunization and T-cells may be purified in an anti-mouse Ig column to remove the B cells, followed by a passage through a Sephadex G10 column to remove the macrophages. Similarly, lymph node cells may be isolated from a human following biopsy or surgical removal of a lymph node.
The ability of a polypeptide (e.g., a Leishmania antigen or a portion or other variant thereof) to induce a response in PBMC or lymph node cell cultures may be evaluated by contacting the cells with the polypeptide and measuring a suitable response. In general, the amount of polypeptide that is sufficient for the evaluation of about 2x105 cells ranges from about 10 ng to about 100 .mu.g, and preferably is about 1-10 .mu.g. The incubation of polypeptide with cells is typically performed at 37oC. for about 1-3 days. Following incubation with polypeptide, the cells are assayed for an appropriate response. If the response is a proliferative response, any of a variety of techniques well known to those of ordinary skill in the art may be employed. For example, the cells may be exposed to a pulse of radioactive thymidine and the incorporation of label into cellular DNA measured. In general, a polypeptide that results in at least a three fold increase in proliferation above background (i.e., the proliferation observed for cells cultured without polypeptide) is considered to be able to induce proliferation.
Alternatively, the response to be measured may be the secretion of one or more cytokines (such as interferon-.gamma. (IFN-.gamma.), interleukin-4 (IL-4), interleukin-12 (p70 and/or p40), interleukin-2 (IL-2) and/or tumor necrosis factor-.alpha. (TNF-.alpha.) or the change in the level of mRNA encoding one or more specific cytokines. In particular, the secretion of interferon-.gamma., interleukin-2, tumor necrosis factor-.alpha. and/or interleukin-12 is indicative of a Th1 response, which is responsible for the protective effect against Leishmania. Assays for any of the above cytokines may generally be performed using methods known to those of ordinary skill in the art, such as an enzyme-linked immunosorbent assay (ELISA). Suitable antibodies for use in such assays may be obtained from a variety of sources such as Chemicon, Temucula, Calif. and PharMingen, San Diego, Calif., and may generally be used according to the manufacturer's instructions. The level of mRNA encoding one or more specific cytokines may be evaluated by, for example, amplification by polymerase chain reaction (PCR). In general, a polypeptide that is able to induce, in a preparation of about 1-3x105 cells, the production of 30 pg/mL of IL-12, IL-4, IFN-.gamma., TNF-.alpha. or IL-12 p40, or 10 pg/mL of IL-12 p70, is considered able to stimulate production of a cytokine.
Immunogenic portions of the antigens described herein may be prepared and identified using well known techniques, such as those summarized in Paul, Fundamental Immunology, 3rd ed., 243-247 (Raven Press, 1993) and references cited therein. Such techniques include screening polypeptides derived from the native antigen for immunogenic properties using, for example, the representative techniques described herein. An immunogenic portion of a polypeptide is a portion that, within such representative assays, generates an immune response (e.g., proliferation and/or cytokine production) that is substantially similar to that generated by the full length antigen. In other words, an immunogenic portion of an antigen may generate at least about 25%, and preferably at least about 50%, of the response generated by the full length antigen in the model ,assays described herein.
Portions and other variants of immunogenic Leishmania antigens may be generated by synthetic or recombinant means. Synthetic polypeptides having fewer than about 100 amino acids, and generally fewer than about 50 amino acids, may be generated using techniques well known to those of ordinary skill in the art. For example, such polypeptides may be synthesized using any of the commercially available solid-phase techniques, such as the Merrifield solid-phase synthesis method, where amino acids are sequentially added to a growing amino acid chain. See Merrifield, J. Am. Chem. Soc. 85:2149-2146, 1963. Equipment for automated synthesis of polypeptides is commercially available from suppliers such as Perkin Elmer/Applied BioSystemsDivision, Foster City, Calif., and may be operated according to the manufacturer's instructions.
Recombinant polypeptides containing portions and/or variants of a native antigen may be readily prepared from a DNA sequence encoding the antigen. For example, supernatants from suitable host/vector systems which secrete recombinant protein into culture media may be first concentrated using a commercially available filter. Following concentration, the concentrate may be applied to a suitable purification matrix such as an affinity matrix or an ion exchange resin. Finally, one or more reverse phase HPLC steps can be employed to further purify a recombinant protein.
In general, any of a variety of expression vectors known to those of ordinary skill in the art may be employed to express recombinant polypeptides of this invention. Expression may be achieved in any appropriate host cell that has been transformed or transfected with an expression vector containing a polynucleotide that encodes a recombinant polypeptide. Suitable host cells include prokaryotes, yeast and higher eukaryotic cells. Preferably, the host cells employed are E. coli, yeast or a mammalian cell line such as COS or CHO. The DNA sequences expressed in this manner may encode naturally occurring antigens, portions of naturally occurring antigens, or other variants thereof. For example, variants of a native antigen may generally be prepared using standard mutagenesis techniques, such as oligonucleotide-directed site-specific mutagenesis, and sections of the DNA sequence may be removed to permit preparation of truncated polypeptides.
In another aspect, the present invention provides epitope repeat sequences, or antigenic epitopes, of a Leishmania antigen, together with polypeptides comprising at least two such contiguous antigenic epitopes. As used herein an "epitope" is a portion of an antigen that reacts with sera from Leishmania-infected individuals (i.e. an epitope is specifically bound by one or more antibodies present in such sera). As discussed above, epitopes of the antigens described in the present application may be generally identified using techniques well known to those of skill in the art.
In one embodiment, antigenic epitopes of the present invention comprise an amino acid sequence provided in SEQ ID NO:43, 56, 57 or 58. As discussed in more detail below, antigenic epitopes provided herein may be employed in the diagnosis and treatment of Leishmania infection, either alone or in combination with other Leishmania antigens or antigenic epitopes. Antigenic epitopes and polypeptides comprising such epitopes may be prepared by synthetic means, as described generally above and in detail in Example 15.
In certain aspects of the present invention, described in detail below, the polypeptides, antigenic epitopes, fusion proteins and/or soluble Leishmania antigens of the present invention may be incorporated into pharmaceutical compositions or vaccines. For clarity, the term "polypeptide" will be used when describing specific embodiments of the inventive therapeutic compositions and diagnostic methods. However, it will be clear to one of skill in the art that the antigenic epitopes and fusion proteins of the present invention may also be employed in such compositions and methods.
Pharmaceutical compositions comprise one or more polypeptides, each of which may contain one or more of the above sequences (or variants thereof), and a physiologically acceptable carrier. Vaccines, also referred to as immunogenic compositions, comprise one or more of the above polypeptides and an immunostimulant, such as an adjuvant (e.g., LbeIF4A, interleukin-12 or other cytokines) or a liposome (into which the polypeptide is incorporated). Many adjuvants contain a substance designed to protect the antigen from rapid catabolism, such as aluminum hydroxide or mineral oil, and a stimulator of immune responses, such as lipid A, Bortadella pertussis or Mycobacterium tuberculosis derived proteins. Certain adjuvants are commercially available as, for example, Freund's Incomplete Adjuvant and Complete Adjuvant (Difco Laboratories, Detroit, Mich.); Merck Adjuvant 65 (Merck and Company, Inc., Rahway, N.J.); AS-2 (SmithKline Beecham, Philadelphia, Pa.); aluminum salts such as aluminum hydroxide gel (alum) or aluminum phosphate; salts of calcium, iron or zinc; an insoluble suspension of acylated tyrosine; acylated sugars; cationically or anionically derivatized polysaccharides; polyphosphazenes; biodegradable microspheres; monophosphoryl lipid A and quil A. Cytokines, such as GM-CSF, interleukin-2, -7, -12, and other like growth factors, may also be used as adjuvants.
Within certain embodiments of the invention, the adjuvant composition is preferably one that induces an immune response predominantly of the Th1 type. By virtue of its ability to induce an exclusive Th1 immune response, the use of LbeIF4A, and variants thereof, as an adjuvant in the vaccines of the present invention is particularly preferred. Certain other preferred adjuvants for eliciting a predominantly Th1 -type response include, for example, a combination of monophosphoryl lipid A, preferably 3-de-O-acylated monophosphoryl lipid A, together with an aluminum salt. MPL.RTM. adjuvants are available from Corixa Corporation (Seattle, WA; see, for example, U.S. Pat. Nos. 4,436,727; 4,877,611; 4,866,034 and 4,912,094). CpG-containing oligonucleotides (in which the CpG dinucleotide is unmethylated) also induce a predominantly Th1 response. Such oligonucleotides are well known and are described, for example, in WO 96/02555, WO 99/33488 and U.S. Pat. Nos. 6,008,200 and 5,856,462. Immunostimulatory DNA sequences are also described, for example, by Sato et al., Science 273:352, 1996. Another preferred adjuvant comprises a saponin, such as Quil A, or derivatives thereof, including QS21 and QS7 (Aquila Biopharmaceuticals Inc., Framingham, Mass.); Escin; Digitonin; or Gypsophila or Chenopodium quinoa saponins. Other preferred formulations include more than one saponin in the adjuvant combinations of the present invention, for example combinations of at least two of the following group comprising QS21, QS7, Quil A, .beta.-escin, or digitonin.
Alternatively the saponin formulations may be combined with vaccine vehicles composed of chitosan or other polycationic polymers, polylactide and polylactide-co-glycolide particles, poly-N-acetyl glucosamine-based polymer matrix, particles composed of polysaccharides or chemically modified polysaccharides, liposomes and lipid-based particles, particles composed of glycerol monoesters, etc. The saponins may also be formulated in the presence of cholesterol to form particulate structures such as liposomes or ISCOMs. Furthermore, the saponins may be formulated together with a polyoxyethylene ether or ester, in either a non-particulate solution or suspension, or in a particulate structure such as a paucilamelar liposome or ISCOM. The saponins may also be formulated with excipients such as CarbopolR to increase viscosity, or may be formulated in a dry powder form with a powder excipient such as lactose.
In one preferred embodiment, the adjuvant system includes the combination of a monophosphoryl lipid A and a saponin derivative, such as the combination of QS21 and 3D-MPL.RTM. adjuvant, as described in WO 94/00153, or a less reactogenic composition where the QS21 is quenched with cholesterol, as described in WO 96/33739. Other preferred formulations comprise an oil-in-water emulsion and tocopherol. Another particularly preferred adjuvant formulation employing QS21, 3D-MPL.RTM. adjuvant and tocopherol in an oil-in-water emulsion is described in WO 95/17210.
Another enhanced adjuvant system involves the combination of a CpG-containing oligonucleotide and a saponin derivative particularly the combination of CpG and QS21 is disclosed in WO 00/09159. Preferably the formulation additionally comprises an oil in water emulsion and tocopherol.
Additional illustrative adjuvants for use in the compositions of the invention include Montanide ISA 720 (Seppic, France), SAF (Chiron, Calif., United States), ISCOMS (CSL), MF-59 (Chiron), the SBAS series of adjuvants (e.g., SBAS-2 or SBAS-4, available from SmithKline Beecham, Rixensart, Belgium), Enhanzyn.TM. (Corixa, Hamilton, Mont.), RC-529 (Corixa, Hamilton, Mont.) and other aminoalkyl glucosaminide 4-phosphates (AGPs), such as those described in U.S. Pat. No. 6,113,918 and pending U.S. patent application Ser. No. 09/074,720, the disclosures of which are incorporated herein by reference in their entireties, and polyoxyethylene ether adjuvants such as those described in WO 99/52549A1.
Other preferred adjuvants include adjuvant molecules of the general formula (i):
HO(CH2 CH2 O)n --A--R,
wherein, n is 1-50, A is a bond or --C(O)--, R is C1-50 alkyl or Phenyl C1-50 alkyl.
One embodiment of the present invention consists of a vaccine formulation comprising a polyoxyethylene ether of general formula (I), wherein n is between 1 and 50, preferably 4-24, most preferably 9; the R component is C1-50, preferably C4 -C20 alkyl and most preferably C12 alkyl, and A is a bond. The concentration of the polyoxyethylene ethers should be in the range 0.1-20%, preferably from 0.1-10%, and most preferably in the range 0.1-1%. Preferred polyoxyethylene ethers are selected from the following group: polyoxyethylene-9-lauryl ether, polyoxyethylene-9-steoryl ether, polyoxyethylene-8-steoryl ether, polyoxyethylene-4-lauryl ether, polyoxyethylene-35-lauryl ether, and polyoxyethylene-23-lauryl ether. Polyoxyethylene ethers such as polyoxyethylene lauryl ether are described in the Merck index (12th edition: entry 7717). These adjuvant molecules are described in WO 99/52549. The polyoxyethylene ether according to the general formula (I) above may, if desired, be combined with another adjuvant. For example, a preferred adjuvant combination is preferably with CpG as described in the pending UK patent application GB 9820956.2.
Vaccines may additionally contain a delivery vehicle, such as a biodegradable microsphere (disclosed, for example, in U.S. Pat. Nos. 4,897,268 and 5,075,109). Pharmaceutical compositions and vaccines within the scope of the present invention may also contain other Leishmania antigens, either incorporated into a combination polypeptide or present within one or more separate polypeptides.
Alternatively, a pharmaceutical or immunogenic composition may contain an immunostimulant, such as an adjuvant (e.g., LbeIF4A, interleukin-12 or other cytokines, or DNA coding for such enhancers), and DNA encoding one or more of the polypeptides or fusion proteins described above, such that the polypeptide is generated in situ. In such compositions, the DNA may be present within any of a variety of delivery systems known to those of ordinary skill in the art, including nucleic acid expression systems, bacteria and viral expression systems. Appropriate nucleic acid expression systems contain the necessary DNA sequences for expression in the patient (such as a suitable promoter and terminating signal). Bacterial delivery systems involve the administration of a bacterium (such as Bacillus-Calmette-Guerrin) that expresses an immunogenic portion of the polypeptide on its cell surface. In a preferred embodiment, the DNA may be introduced using a viral expression system (e.g., vaccinia or other pox virus, retrovirus, or adenovirus), which may involve the use of a non-pathogenic (defective), replication competent virus. Techniques for incorporating DNA into such expression systems are well known to those of ordinary skill in the art. The DNA may also be "naked," as described, for example, in Ulmer et al., Science 259:1745-1749 (1993) and reviewed by Cohen, Science 259:1691-1692 (1993). The uptake of naked DNA may be increased by coating the DNA onto biodegradable beads, which are efficiently transported into the cells.
While any suitable carrier known to those of ordinary skill in the art may be employed in the pharmaceutical compositions of this invention, the type of carrier will vary depending on the mode of administration. For parenteral administration, such as subcutaneous injection, the carrier preferably comprises water, saline, alcohol, a fat, a wax or a buffer. For oral administration, any of the above carriers or a solid carrier, such as mannitol, lactose, starch, magnesium stearate, sodium saccharine, talcum, cellulose, glucose, sucrose, and magnesium carbonate, may be employed. Biodegradable microspheres (e.g., polylactic galactide) may also be employed as carriers for the pharmaceutical compositions of this invention. Suitable biodegradable microspheres are disclosed, for example, in U.S. Pat. Nos. 4,897,268 and 5,075,109.
In one preferred embodiment, compositions of the present invention include multiple polypeptides selected so as to provide enhanced protection against a variety of Leishmania species. Such polypeptides may be selected based on the species of origin of the native antigen or based on a high degree of conservation of amino acid sequence among different species of Leishmania. A combination of individual polypeptides may be particularly effective as a prophylactic and/or therapeutic vaccine because (1) stimulation of proliferation and/or cytokine production by a combination of individual polypeptides may be additive, (2) stimulation of proliferation and/or cytokine production by a combination of individual polypeptides may be synergistic, (3) a combination of individual polypeptides may stimulate cytokine profiles in such a way as to be complementary to each other and/or (4) individual polypeptides may be complementary to one another when certain of them are expressed more abundantly on the individual species or strain of Leishmania responsible for infection. A preferred combination contains polypeptides that comprise immunogenic portions of M15, Ldp23, Lbhsp83, Lt-1 and LbeIF4A. Alternatively, or in addition, the combination may include one or more polypeptides comprising immunogenic portions of other Leishmania antigens disclosed herein, and/or soluble Leishmania antigens.
In another preferred embodiment, compositions of the present invention include single polypeptides selected so as to provide enhanced protection against a variety of Leishmania species. A single individual polypeptide may be particularly effective as a prophylactic and/or therapeutic vaccine for those reasons stated above for combinations of individual polypeptides.
In another embodiment, compositions of the present invention include individual polypeptides and combinations of the above described polypeptides employed with a variety of adjuvants, such as IL-12 (protein or DNA) to confer a protective response against a variety of Leishmania species.
In yet another embodiment, compositions of the present invention include DNA constructs of the various Leishmania species employed alone or in combination with variety of adjuvants, such as IL-12 (protein or DNA) to confer a protective response against a variety of Leishmania species.
The above pharmaceutical compositions and vaccines may be used, for example, to induce protective immunity against Leishmania in a patient, such as a human or a dog, to prevent leishmaniasis. Appropriate doses and methods of administration for this purposes are described in detail below.
The pharmaceutical and immunogenic compositions described herein may also be used to stimulate an immune response, which may be cellular and/or humoral, in a patient. For Leishmania-infected patients, the immune responses that may be generated include a preferential Th1 immune response (i.e., a response characterized by the production of the cytokines interleukin-1, interleukin-2, interleukin-12 and/or interferon-.gamma., as well as tumor necrosis factor-.alpha.). For uninfected patients, the immune response may be the production of interleukin-12 and/or interleukin-2, or the stimulation of gamma delta T-cells. In either category of patient, the response stimulated may include IL-12 production. Such responses may also be elicited in biological samples of PBMC or components thereof derived from Leishmania-infected or uninfected individuals. As noted above, assays for any of the above cytokines may generally be performed using methods known to those of ordinary skill in the art, such as an enzyme-linked immunosorbent assay (ELISA).
Suitable pharmaceutical compositions and vaccines for use in this aspect of the present invention are those that contain at least one polypeptide comprising an immunogenic portion of a Leishmania antigen disclosed herein (or a variant thereof). Preferably, the polypeptides employed in the pharmaceutical compositions and vaccines are complementary, as described above. Soluble Leishmania antigens, with or without additional polypeptides, may also be employed.
The pharmaceutical compositions and vaccines described herein may also be used to treat a patient afflicted with a disease responsive to IL-12 stimulation. The patient may be any warm-blooded animal, such as a human or a dog. Such diseases include infections (which may be, for example, bacterial, viral or protozoan) or diseases such as cancer. In one embodiment, the disease is leishmaniasis, and the patient may display clinical symptoms or may be asymptomatic. In general, the responsiveness of a particular disease to IL-12 stimulation may be determined by evaluating the effect of treatment with a pharmaceutical composition or vaccine of the present invention on clinical correlates of immunity. For example, if treatment results in a heightened Th1 response or the conversion of a Th2 to a Th1 profile, with accompanying clinical improvement in the treated patient, the disease is responsive to IL-12 stimulation. Polypeptide administration may be as described below, or may extend for a longer period of time, depending on the indication. Preferably, the polypeptides employed in the pharmaceutical compositions and vaccines are complementary, as described above. A particularly preferred combination contains polypeptides that comprise immunogenic portions of M15, Ldp23, Lbhsp83, Lt-1and LbeIF4A, Lmspla, Lmsp9a, and MAPS-1A. Soluble Leishmania antigens, with or without additional polypeptides, may also be employed.
Routes and frequency of administration, as well as dosage, for the above aspects of the present invention will vary from individual to individual and may parallel those currently being used in immunization against other infections, including protozoan, viral and bacterial infections. In general, the pharmaceutical compositions and vaccines may be administered by injection (e.g., intracutaneous, intramuscular, intravenous or subcutaneous), intranasally (e.g., by aspiration) or orally. Between 1 and 12 doses may be administered over a 1 year period. For therapeutic vaccination (i.e., treatment of an infected individual), 12 doses are preferably administered, at one month intervals. For prophylactic use, 3 doses are preferably administered, at 3 month intervals. In either case, booster vaccinations may be given periodically thereafter. Alternate protocols may be appropriate for individual patients. A suitable dose is an amount of polypeptide or DNA that, when administered as described above, is capable of raising an immune response in an immunized patient sufficient to protect the patient from leishmaniasis for at least 1-2 years. In general, the amount of polypeptide present in a dose (or produced in situ by the DNA in a dose) ranges from about 100 ng to about 1 mg per kg of host, typically from about 10 .mu.g to about 100 .mu.g. Suitable dose sizes will vary with the size of the patient, but will typically range from about 0.1 mL to about 5 mL.
In another aspect, this invention provides methods for using one or more of the polypeptides described above to diagnose Leishmania infection in a patient using a skin test. As used herein, a "skin test" is any assay performed directly on a patient in which a delayed-type hypersensitivity (DTH) reaction (such as induration and accompanying redness) is measured following intradermal injection of one or more polypeptides as described above. Such injection may be achieved using any suitable device sufficient to contact the polypeptide or polypeptides with dermal cells of the patient, such as a tuberculin syringe or 1 mL syringe. Preferably, the reaction is measured at least 48 hours after injection, more preferably 72 hours after injection.
The DTH reaction is a cell-mediated immune response, which is greater in patients that have been exposed previously to a test antigen (i.e., an immunogenic portion of a polypeptide employed, or a variant thereof). The response may measured visually, using a ruler. In general, induration that is greater than about 0.5 cm in diameter, preferably greater than about 1.0 cm in diameter, is a positive response, indicative of Leishmania infection, which may or may not be manifested as an active disease.
The polypeptides of this invention are preferably formulated, for use in a skin test, as pharmaceutical compositions containing at least one polypeptide and a physiologically acceptable carrier, as described above. Such compositions typically contain one or more of the above polypeptides in an amount ranging from about 1 .mu.g to 100 .mu.g, preferably from about 10 .mu.g to 50 .mu.g in a volume of 0.1 mL. Preferably, the carrier employed in such pharmaceutical compositions is a saline solution with appropriate preservatives, such as phenol and/or Tween 80.TM..
The inventive polypeptides may also be employed in combination with one or more known Leishmania antigens in the diagnosis of leishmaniasis, using, for example, the skin test described above. Preferably, individual polypeptides are chosen in such a way as to be complementary to each other. Examples of known Leishmania antigens which may be usefully employed in conjunction with the inventive polypeptides include K39 (Burns et al., Proc. Natl. Acad. Sci. USA, 1993 90:775-779).
Claim 1 of 3 Claims
What is claimed is:
1. A method for inducing protective immunity against leishmaniasis in a patient comprising administering an immunogenic composition comprising a fusion protein and an immunostimulant, wherein the fusion protein comprises the amino acid sequence of SEQ ID NO:24.