RÉSUMÉ
Vaccinia virus (VV) recombinants that contain the genes encoding the Venezuelan equine encephalitis virus (VEEV) structural gene region (C-E3-E2-6 K-E1) solidly protect mice against peripheral challenge with virulent VEEV, but provide only partial protection against airborne challenge. To improve upon these results we focussed on the principal antigens involved in protection. VV recombinants encoding the structural genes E3-E2-6 K-E1, E3-E2-6 K or 6 K-E1 were prepared and evaluated for their ability to protect Balb/c mice after a single dorsal scarification with 10(8) PFU against peripheral or airborne challenge with virulent VEEV. The antibody response was also examined. Our experiments provide new evidence that truncates of the VEEV structural region (E3-E2-6 K-E1, E3-E2-6 K), cloned and expressed in VV, protect against challenge with virulent virus. They also confirm the important role of E2 in protection. However, we were unable to improve upon previously reported levels of protection against airborne challenge. A substantial level of circulating antibodies and the presence of local IgA (not always induced by mucosal immunization) (Greenway et al., 1992) appear essential for protection against the airborne virus. Current VV-VEEV recombinants seem unable to elicit this level of immune response and further improvements are therefore required to increase the immunogenicity of VV-VEEV vaccines.
Sujet(s)
Virus de l'encéphalite équine du Venezuela/génétique , Encéphalomyélite équine du Vénézuéla/prévention et contrôle , Vecteurs génétiques , Virus de la vaccine/génétique , Protéines virales structurales/génétique , Animaux , Anticorps antiviraux/sang , Lignée cellulaire , Virus de l'encéphalite équine du Venezuela/immunologie , Virus de l'encéphalite équine du Venezuela/pathogénicité , Encéphalomyélite équine du Vénézuéla/immunologie , Equus caballus , Immunité muqueuse , Immunoglobuline G/sang , Souris , Souris de lignée BALB C , Vaccination , Vaccins synthétiques/administration et posologie , Vaccins synthétiques/immunologie , Protéines virales structurales/immunologie , Vaccins antiviraux/immunologie , VirulenceRÉSUMÉ
Plasmids expressing the V antigen of Yersinia pestis or the E2 glycoprotein of Venezuelan Equine Encephalitis (VEE) virus were used to vaccinate mice by intra-dermal or intra-muscular injection, or by particle-mediated bombardment using the Helios gene gun. After two immunizations, groups of mice which had received 4 microg doses of plasmid DNA using the gene gun had IgG levels which were higher than in other groups manually immunised with 12-fold more plasmid DNA. The immunoglobulin isotype profile was predominantly IgG1 following inoculation with either plasmid. Our results indicate that gene gun mediated vaccination can be used to increase the magnitude of the immune response to both bacterial and viral antigens expressed by plasmid DNA.