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Title:  DNA vaccines against poxviruses

United States Patent:  6,562,376

Issued:  May 13, 2003

Inventors:  Hooper; Jay W. (New Market, MD); Schmaljohn; Alan L. (Frederick, MD); Schmaljohn; Connie S. (Frederick, MD)

Assignee:  The United States of America as represented by the Secretary of the Army (Washington, DC)

Appl. No.:  800632

Filed:  March 7, 2001

Abstract

In this application is described a poxvirus naked DNA vaccine which protects animals against poxvirus challenge comprising IMV and EEV nucleic acids from poxvirus. Methods of use of the vaccine and its advantages are described.

DETAILED DESCRIPTION OF THE INVENTION

In this application is described a composition and method for the vaccination of individuals against poxvirus. The method comprises delivery of a DNA encoding a poxvirus antigen to cells of an individual such that the antigen is expressed in the cell and an immune response is induced in the individual.

DNA vaccination involves administering antigen-encoding polynucleotides in vivo to induce the production of a correctly folded antigen(s) within the target cells. The introduction of the DNA vaccine will cause to be expressed within those cells the structural protein determinants associated with the pathogen protein or proteins. The processed structural proteins will be displayed on the cellular surface of the transfected cells in conjunction with the Major Histocompatibility Complex (MHC) antigens of the normal cell. Even when cell-mediated immunity is not the primary means of preventing infection, it is likely important for resolving established infections. Furthermore, the structural proteins released by the expressing transfected cells can also be picked up by antigen-presenting cells to trigger systemic humoral antibody responses.

In one embodiment, the present invention relates to a DNA or cDNA segment which encodes an IMV or an EEV antigen from a poxvirus. Genome sequences of different strains of VACV have been published and are publicly available. The VACV (Copenhagen strain) sequence (accession number M35027) can be used to deduce primer sequences for the genes of interest as described below for deducing the sequence of the VACV Connaught strain. The VACV Connaught strain L1R (SEQ ID NO:1) and A33R (SEQ ID NO:2) sequence have been deposited as Genebank #Af226617 and Genebank #Af226618, respectively. L1R and A33R homologs from other poxviruses can be used as immunogens to induce a immune response in an individual against poxviruses since the homologs in other poxviruses have high identity with the VACV proteins. Homologs include genes sharing a common evolutionaly origin, structure/function, and the products of which, encode proteins with amino acid sequence identity of at least 20%, preferably at least 30%, more preferably at least 50%, and most preferably means at least 80%. A homolog can be identified by methods known in the art such as comparison of the nucleic acid or amino acid sequences to each other using computer programs, such as BLAST, or by hybridization under stringencies which are designed to detect a predetermined amount of mismatch between the sequences. Other strains of vaccinia are expected to contain sequences at least 90% identical which will likely produce antigens capable of eliciting protective/neutralizing antibodies. Such strains include IHD, Brighton, WR, Lister, Copenhagen, Ankara. In addition, homologs of these vaccinia antigens having at least 90% identity exist in other poxviruses, such as Orthopoxvirus, such as camelpox virus, cowpox virus, ectromelia virus, monkeypox virus, raccoon poxvirus, skunk poxvirus, Tatera poxvirus, Uasin Gishu virus, variola virus, Volepox virus, Parapoxvirus such as Ausdyk virus, Bovin papular stomatitis virus, orf virus, pseudocowpox virus, red deer poxvirus, seal parapoxvirus, Capripoxvirus such as sheep-pox virus, goatpox virus lumpyskin disease virus, Suipoxvirus such as swinepox virus, Leporipoxvirus such as myxoma virus fibroma virus, hare fibroma virus, squirrel fibroma virus, western squirrel fibroma, Avipoxvirus of many species, Yatapoxvirus such as Tantpox virus, Yabapoxvirus, Molluscipoxvirus such as molluscum contagiosum virus, macropod poxvirus, crocodilian poxvirus, among others. Because of the high identity between poxviruses, it is expected that vaccines of the present invention would provide cross protection between different poxviruses.

Nucleic acids encoding IMV antigens include L1R, A27L, A3L, A10L, A12L, A13L, A14L, A17L, D8L, H3L, L4R, G7L, and 15L (Takahashi et al., 1994, Virology 202, 811-852). Nucleic acids encoding EEV antigens include A33R (Roper et al., 1996, J. Virol. 70, 3753-3762), A34R (Duncan and Smith, 1992, J. Virol. 66, 1610-1621), A36R (Parkinson and Smith, 1994, Virology 204, 376-390), A56R (Payne and Norrby, 1976, J. Gen. Virol. 32, 63-72; Shida, H., 1986, Virology 150, 451-462), B5R (Engelstad et al., 1992, Virology 188, 801-810; Isaacs et al., 1992, J. Virol. 66, 7217-7224), and F13L (Hirt et al., 1986, J. Virol. 58, 757-764). DNA or nucleic acid sequences to which the invention also relates include fragments of the IMV or EEV genes from poxviruses containing protective epitopes or antigenic determinants. Such epitopes may be conformational. The vaccine of the present invention can comprise three or more vaccinia virus nucleic acids (or nucleic acids from other poxviruses coding for homologous antigens) where at least one nucleic acid encodes an antigen found on the IMV and at least one nucleic acid encodes an antigen found on the EEV. For example, two IMV genes are L1 and A27L, and two EEV genes are A33R and B5R. The vaccine may consist of one of the following combinations: L1R+A33R; L1R+A33R+B5R; L1R+A33R+A27L; A27L+A33R+B5R; L1R+A27L+B5R; L1R+A33R+A27L, etc. or any other combination of IMV gene and EEV gene (or a homolog of the IMV and EEV genes in other poxviruses).

The sequence of nucleic acids encoding antigens found in the IMV or the EEV may be generated in any manner, including for example, chemical synthesis or DNA replication or reverse transcription or transcription, which are based on the information provided by the sequence bases in the region(s) from which the polynucleotide is derived. In addition, combinations of regions corresponding to that of the designated sequence may be modified in ways known in the art to be consistent with an intended use. The sequences of the present invention can be used in diagnostic assays such as hybridization assays and polymerase chain reaction (PCR) assays for the detection of poxvirus.

L1R and A33R sequences were derived from the VACV (Connaught strain) by PCR and cloned into pWRG7077 to yield naked DNA expression plasmids pWRG/L1R, respectively. It is understood in the art that certain changes to the nucleotide sequence employed in a genetic construct have little or no bearing on the proteins encoded by the construct, for example due to the degeneracy of the genetic code. Such changes result either from silent point mutations or point mutations that encode different amino acids that do not appreciably alter the behavior of the encoded protein. It is also understood that portions of the coding region can be eliminated without affecting the ability of the construct to achieve the desired effect, namely induction of a protective immune response against poxvirus. It is further understood in the art that certain advantageous steps can be taken to increase the antigenicity of an encoded protein by modifying its amino acid composition. Such changes in amino acid composition can be introduced by modifying the genetic sequence encoding the protein. It is contemplated that all such modifications and variations of the L1R and A33R genes of poxvirus are equivalents within the scope of the present invention.

The DNA encoding the desired antigen can be introduced into the cell in any suitable form including, a linearized plasmid, a circular plasmid, a plasmid capable of replication, an episome, RNA, etc. Preferably, the gene is contained in a plasmid. In a particularly preferred embodiment, the plasmid is an expression vector. Individual expression vectors capable of expressing the genetic material can be produced using standard recombinant techniques. Please see e.g., Maniatis et al., 1985 Molecular Cloning: A Laboratory Manual or DNA Cloning, Vol. I and II (D. N. Glover, ed., 1985) for general cloning methods.

Therefore, in another embodiment, the present invention relates to a recombinant DNA molecule that includes a vector and a DNA sequence as described above. The vector can take the form of a plasmid such as pCRII (Invitrogen) or pJW4303 (Konishi, E. et al., 1992, Virology 188:714), or any expression vector such as viral vectors e.g. adenovirus or Venezuelan equine encephalitis virus and others known in the art. Preferably, a promoter sequence operable in the target cell is operably linked to the DNA sequence. Several such promoters are known for mammalian systems which may be joined 5', or upstream, of the coding sequence for the encoded protein to be expressed. A suitable promoter is the human cytomegalovirus immediate early promoter. A downstream transcriptional terminator, or polyadenylation sequence, such as the polyA addition sequence of the bovine growth hormone gene, may also be added 3' to the protein coding sequence.

A suitable construct for use in the method of the present invention is pWRG7077 (4326 bp) (PowderJect Vaccines, Inc., Madison, Wis.), FIG. 1. pWRG7077 includes a human cytomegalovirus (hCMV) immediate early promoter (IE) and a bovine growth hormone polyA addition site. Between the promoter and the polyA addition site is Intron A, a sequence that naturally occurs in conjunction with the hCMV IE promoter that has been demonstrated to increase transcription when present on an expression plasmid. Downstream from Intron A, and between Intron A and the polyA addition sequence, are unique cloning sites into which the poxvirus DNA can be cloned. Also provided on pWRG7077 is a gene that confers bacterial host-cell resistance to kanamycin. Any of the fragments that encode L1R and A33R can be cloned into one of the cloning sites in pWRG7077, using methods known to the art.

In a further embodiment, the present invention relates to host cells stably transformed or transfected with the above-described recombinant DNA construct. The host cell can be prokaryotic such as Bacillus or E. coli, or eukaryotic such a Saccharomyces or Pichia, or vertebrate cells, mammalian cells or insect cells. The vector containing the poxvirus sequence is expressed in the bacteria and the expressed product used for diagnostic procedures or as a vaccine. Please see e.g., Maniatis et al., 1985 Molecular Cloning: A Laboratory Manual or DNA Cloning, Vol. I and II (D. N. Glover, ed., 1985) for general cloning methods. The DNA sequence can be present in the vector to a DNA encoding an agent for aid in purification of poxvirus proteins or peptides. The transformed or transfected host cells can be used as a source of DNA sequences described above. When the recombinant molecule takes the form of an expression system, the transformed or transfected cells can be used as a source of the protein or peptide encoded by the DNA. The DNA can be used as circular or linear, or linearized plasmid as long as the poxvirus sequences are operably linked to a promoter which can be expressed in the transfected cell.

In this application we describe the elicitation of protective immunity to poxviruses by DNA vaccines. The DNA can be delivered by injection into the tissue of the recipient, oral or pulmonary delivery and inoculation by particle bombardment (i.e., gene gun). Any of these methods can be used to deliver DNA as long as the DNA is expressed and the desired antigen is made in the cell. Two methods are exemplified in this application, both shown to be successful in eliciting a protective immune response in the vaccinee.

To deliver DNA vaccines by particle bombardment, we chose to use the PowderJect-XR.TM. gene gun device described in WO 95/19799, Jul. 27, 1995. Other instruments are available and known to people in the art. This instrument, which delivers DNA-coated gold beads directly into epidermal cells by high-velocity particle bombardment, was shown to more efficiently induce both humoral and cell-mediated immune responses, with smaller quantities of DNA, than inoculation of the same DNAs by other parenteral routes (Eisenbraun, M. et al., 1993, DNA Cell. Biol. 12: 791; Fynan, E. F. et al., 1993, Proc. Natl. Acad. Sci. USA 90: 11478; Haynes, J. R. et al., 1994, AIDS Res. Hum. Retroviruses 10: Suppl. 2:S43; Pertmer, T. M. et al., 1995, Vaccine 13: 1427). Epidermal inoculation of the DNA candidate vaccines also offers the advantages of gene expression in an immunologically active tissue that is generally exfoliated within 15 to 30 days, and which is an important natural focus of viral replication after tick-bite (Bos, J. D., 1997, Clin. Exp. Immunol. 107 Suppl. 1:3; Labuda, M. et al., 1996, Virology 219:357; Rambukkana, A. et al., 1995, Lab. Invest. 73:521; Stingl, G., 1993, Recent Results Cancer Res. 128:45).

Candidate vaccines include particles having nucleic acids encoding IMV antigens and particles having nucleic acids encoding EEV antigens. The IMV and EEV antigens can be derived from other other Orthopoxviruses including variola virus, monkeypox virus, cowpox virus, Parapoxviruses such as orf virus, paravaccinia virus, and unclassified poxviruses such as Tanapoxvirus, Yabapoxvirus and Molluscum contagiosum.

In addition, the present invention relates to a vaccine comprising one or more DNAs from different poxviruses. Such a vaccine is referred to as a multivalent vaccine. The vaccine is designed to protect against pathologies resulting from exposure to one or several poxviruses. The DNA segments from different viruses can be on different particles or on the same particle, whichever results in the desired immune response. The vaccine can also be combined with reagents which increase the antigenicity of the vaccine, or reduce its side effects.

The technique of accelerated particles gene delivery or particle bombardment is based on the coating of DNA to be delivered into cells onto extremely small carrier particles, which are designed to be small in relation to the cells sought to be transformed by the process. The DNA sequence containing the desired gene can be simply dried onto a small inert particle. The particle may be made of any inert material such as an inert metal (gold, silver, platinum, tungsten, etc.) or inert plastic (polystyrene, polypropylene, polycarbonate, etc.). Preferably, the particle is made of gold, platinum or tungsten. Most preferably, the particle is made of gold. Suitably, the particle is spherical and has a diameter of 0.5 to 5 microns, preferably 1 to 3 microns. DNA molecules in such a form may have a relatively short period of stability and may tend to degrade rather rapidly due to chemical reactions with the metallic or oxide substrate of the particle itself. Thus, if the carrier particles are first coated with an encapsulating agent, the DNA strands have greatly improved stability and do not degrade significantly even over a time period of several weeks. A suitable encapsulating agent is polylysine (molecular weight 200,000) which can be applied to the carrier particles before the DNA molecules are applied. Other encapsulating agents, polymeric or otherwise, may also be useful as similar encapsulating agents, including spermidine. The polylysine is applied to the particles by rinsing the gold particles in a solution of 0.02% polylysine and then air drying or heat drying the particles thus coated. Once the metallic particles coated with polylysine were properly dried, DNA strands are then loaded onto the particles.

The DNA is loaded onto the particles at a rate of between 0.5 and 30 micrograms of DNA per milligram of gold bead spheres. A preferable ratio of DNA to gold is 0.5-5.0 ug of DNA per milligram of gold.

A sample procedure begins with gamma irradiated (preferably about 30 kGy) tefzel tubing. The gold is weighed out into a microfuge tube, spermidine (free base) at about 0.05 M is added and mixed, and then the DNA is added. A 10% CaCl solution is incubated along with the DNA for about 10 minutes to provide a fine calcium precipitate. The precipitate carries the DNA with it onto the beads. The tubes are microfuged and the pellet resuspended and washed in 100% ethanol and the final product resuspeded in 100% ethanol at 0.0025 mg/ml PVP. The gold with the DNA is then applied onto the tubing and dried.

The general approach of accelerated particle gene transfection technology is described in U.S. Pat. No. 4,945,050 to Sanford. An instrument based on an improved variant of that approach is available commercially from PowderJect Vaccines, Inc., Madison Wis., and is described in WO 95/19799. All documents cited herein supra and infra are hereby incorporated in their entirety by reference thereto. Briefly, the DNA-coated particles are deposited onto the interior surface of plastic tubing which is cut to a suitable length to form sample cartridges. A sample cartridge is placed in the path of a compressed gas (e.g., helium at a pressure sufficient to dislodge the particles from the cartridge e.g., 350-400 psi). The particles are entrained in the gas stream and are delivered with sufficient force toward the target tissue to enter the cells of the tissue. Further details are available in the published apparatus application.

The coated carrier particles are physically accelerated toward the cells to be transformed such that the carrier particles lodge in the interior of the target cells. This technique can be used either with cells in vitro or in vivo. At some frequency, the DNA which has been previously coated onto the carrier particles is expressed in the target cells. This gene expression technique has been demonstrated to work in prokaryotes and eukaryotes, from bacteria and yeasts to higher plants and animals. Thus, the accelerated particle method provides a convenient methodology for delivering genes into the cells of a wide variety of tissue types, and offers the capability of delivering those genes to cells in situ and in vivo without any adverse impact or effect on the treated individual. Therefore, the accelerated particle method is also preferred in that it allows a DNA vaccine capable of eliciting an immune response to be directed both to a particular tissue, and to a particular cell layer in a tissue, by varying the delivery site and the force with which the particles are accelerated, respectively. This technique is thus particularly suited for delivery of genes for antigenic proteins into the epidermis.

A DNA vaccine can be delivered in a non-invasive manner to a variety of susceptible tissue types in order to achieve the desired antigenic response in the individual. Most advantageously, the genetic vaccine can be introduced into the epidermis. Such delivery, it has been found, will produce a systemic humoral immune response.

To obtain additional effectiveness from this technique, it may also be desirable that the genes be delivered to a mucosal tissue surface, in order to ensure that mucosal, humoral and cellular immune responses are produced in the vaccinated individual. There are a variety of suitable delivery sites available including any number of sites on the epidermis, peripheral blood cells, i.e. lymphocytes, which could be treated in vitro and placed back into the individual, and a variety of oral, upper respiratory, and genital mucosal surfaces.

Gene gun-based DNA immunization achieves direct, intracellular delivery of DNA, elicits higher levels of protective immunity, and requires approximately three orders of magnitude less DNA than methods employing standard inoculation.

Moreover, gene gun delivery allows for precise control over the level and form of antigen production in a given epidermal site because intracellular DNA delivery can be controlled by systematically varying the number of particles delivered and the amount of DNA per particle. This precise control over the level and form of antigen production may allow for control over the nature of the resultant immune response.

The term transfected is used herein to refer to cells which have incorporated the delivered foreign DNA vaccine, whichever delivery technique is used.

It is herein disclosed that when inducing cellular, humoral, and protective immune repsonses after DNA vaccination the preferred target cells are epidermal cells, rather than cells of deeper skin layers such as the dermis. Epidermal cells are preferred recipients of DNA vaccines because they are the most accessible cells of the body and may, therefore, be immunized non-invasively. Secondly, in addition to eliciting a humoral immune response, DNA immunized epidermal cells also elicit a cytotoxic immune response that is stronger than that generated in sub-epidermal cells. Delivery to epidermis also has the advantages of being less invasive and delivering to cells which are ultimately sloughed by the body.

Although it can be desirable to induce an immune response by delivering genetic material to a target animal, merely demonstrating an immune response is not necessarily sufficient to confer protective advantage on the animal. What is important is to achieve a protective immune response that manifests itself in a clinical difference. That is, a method is effective only if it reduces the severity of the disease symptoms. It is preferred that the immunization method be at least 20% effective in preventing death in an immunized population after challenge with poxvirus. More preferably, the vaccination method is 50% or more effective, and most preferably 70-100% effective, in preventing death in an immunized population. The vaccination method is shown herein to be 100% effective in the mouse model for poxvirus. In contrast, unimmunized animals are uniformly killed by challenge with poxvirus. Our results indicate that vaccination with and IMV (L1R) and EEV (A33R) encoding nucleic acid on different particles provides the best protection against a lethal poxvirus infection.

Generally, the DNA vaccine administered may be in an amount of about 1-5 ug of DNA per dose and will depend on the subject to be treated, capacity of the subject's immune system to develop the desired immune response, and the degree of protection desired. Precise amounts of the vaccine to be administered may depend on the judgement of the practitioner and may be peculiar to each subject and antigen.

The vaccine for eliciting an immune response against one or more viruses, may be given in a single dose schedule, or preferably a multiple dose schedule in which a primary course of vaccination may be with 1-10 separate doses, followed by other doses given at subsequent time intervals required to maintain and or reinforce the immune response, for example, at 1-4 months for a second dose, and if needed, a subsequent dose(s) after several months. Examples of suitable immunization schedules include: (i) 0, 1 months and 6 months, (ii) 0, 7 days and 1 month, (iii) 0 and 1 month, (iv) 0 and 6 months, or other schedules sufficient to elicit the desired immune responses expected to confer protective immunity, or reduce disease symptoms, or reduce severity of disease.

In another embodiment, the present invention provides reagents useful for carrying out the present process. Such reagents comprise a DNA fragment containing at least one IMV or EEV antigen such as L1R or A33R from poxvirus, and a small, inert, dense particle. The DNA fragment, and dense particle are those described above.

Preferably, the DNA is frozen or lyophilized, and the small, inert, dense particle is in dry powder. If a coating solution is used, the dry ingredients for the coating solution may be premixed and premeasured and contained in a container such as a vial or sealed envelope.

The present invention also provides kits which are useful for carrying out the present invention. The present kits comprise a first container means containing the above-described frozen or lyophilized DNA. The kit also comprises a second container means which contains the coating solution or the premixed, premeasured dry components of the coating solution. The kit also comprises a third container means which contains the small, inert, dense particles in dry powder form or suspended in 100% ethanol. These container means can be made of glass, plastic or foil and can be a vial, bottle, pouch, tube, bag, etc. The kit may also contain written information, such as procedures for carrying out the present invention or analytical information, such as the amount of reagent (e.g. moles or mass of DNA) contained in the first container means. The written information may be on any of the first, second, and/or third container means, and/or a separate sheet included, along with the first, second, and third container means, in a fourth container means. The fourth container means may be, e.g. a box or a bag, and may contain the first, second, and third container means.

Claim 1 of 29 Claims

What is claimed is:

1. A DNA vaccine against poxviruses comprising at least three of the poxvirus nucleic acids selected from the group consisting of: a nucleic acid encoding L1R, a nucleic acid encoding A33R, a nucleic acid encoding A27L, a nucleic acid encoding B5R, a nucleic acid encoding a homolog of L1R, a nucleic acid encoding a homolog of A33R, a nucleic acid encoding a homolog of A27L, and a nucleic acid encoding a homolog of B5R.
 



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