Title:  DNA vaccines against tick-borne flaviviruses

United States Patent:  6,258,788

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

Filed:  November 20, 1998

Particle mediated immunization of tick-borne flavivirus genes confers homologous and heterologous protection against tick borne encephalitis.

SUMMARY OF THE INVENTION

In this report, we describe two plasmid-based TBE candidate vaccines, which express the premembrane (prM) and envelope (E) genes of RSSE or CEE viruses under control of a cytomegalovirus early promoter. We chose the prM and E genes for expression because of earlier reports with other flaviviruses which indicated that coexpressed prM and E form subviral particles that are able to elicit neutralizing and protective immune responses in animals (Konishi, E. and P. W. Mason, 1993, J. Virol. 67: 1672; Konishi, E. et al., 1992, Virology 190:454; Pincus, S. et al., 1992, Virology 187: 290). Coexpression of prM and E of CEE virus also produces subviral particles, and although these particles were not tested for immunogenicity, they were found to retain biological properties of complete virus such as membrane fusion and hemagglutination (Schalich, J. et al., 1996, J. Virol. 70:4549).

To deliver our DNA vaccines, we chose to use the PowderJect-XR.TM. gene gun device described in WO 95/19799, Jul. 17, 1995. 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. U.S.A. 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). In this application we describe the elicitation of cross-protective immunity to RSSE and CEE viruses by DNA vaccines.

Therefore, the present invention relates to a method for eliciting in an individual an immune response against an alphavirus which causes tick-borne encephalitis comprising delivering to the individual a DNA vaccine comprising a vector including a viral antigen such that when the antigen is introduced into a cell from the individual, the DNA is expressed, the viral antigen is produced in the cell and an immune response against the antigen is mounted.

In one aspect of the invention, the DNA vaccine is delivered by coating a small carrier particle with the DNA vaccine and delivering the DNA-coated particle into an animal's epidermal tissue via particle bombardment. This method may be adapted for delivery to either epidermal or mucosal tissue, or delivery into peripheral blood cells, and thus may be used to induce humoral, cell-mediated, and secretory immune reponses in the vaccinated individual.

The DNA vaccine according to the present invention is inherently safe, is not painful to administer, and should not result in adverse side effects to the vaccinated individual. In addition, the invention does not require growth or use of tick-borne flavivirus, which may be spread by aerosol transmission and are typically fatal.

Claim 1 of 11 Claims

What is claimed is:

1. A method for inducing a protective immune response to a tick-borne flavivirus protein in a mammal, comprising

(i) preparing a nucleic acid encoding an antigenic determinant of a tick-borne flavivirus prM/E protein operatively linked to a CMV promoter operative in cells of a mammal, which nucleic acid is suitable for stably producing the antigenic determinant in a mammal;

(ii) coating the nucleic acid in (i) onto carrier particles;

(iii) accelerating the coated carrier particles into epidermal cells of the mammal in vivo; and

(iv) inducing a protective immune response in said mammal upon exposure to a tick-borne flavivirus.

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