The long-term objective of this proposal is to increase the safety and efficacy of live recombinant vaccines, for use on control of human diseases. The immediate objective of this proposal is to enhance the safety and efficacy of vaccinia virus (VV) recombinant vaccines for humans and other animals. The principals that we address in this proposal using VV as a model would have application for other live recombinant vaccines. We propose improving the safety and enhancing the immunogenicity by co- expressing cytokines and immunogenic antigens in a modified VV vector that has had specific immune-modulating genes inactivated or deleted. The efficacy of these alterations in the VV vector will be tested using a vesicular stomatitis (VSV) model. This will enable us to evaluate our vaccines for both systemic and localized disease conditions, using mice and cattle, respectively, as hosts. We have demonstrated the adjuvant effects of interferon-gamma (IFN-gamma) in cattle and mice immunized with a mixture of the cytokine and the glycoprotein of vesicular stomatitis virus. Accordingly, we co-expressed cytokine genes with other immunogenic foreign genes in VV in an effort to increase efficacy of these vaccines. Although dramatic attenuation of VV was demonstrated, no immune enhancement to VV or co-expressed foreign proteins was detected. Our hypothesis is that safety and immunogenicity of recombinant VV (rVV) vaccines can be improved by co-expressing the lymphokine, interferon-gamma (IFN-gamma) with an immunogenic protein, and inactivating one or more VV immune-modulating genes. Such a vaccine will combine the effectiveness of live attenuated vaccines with the safety of subunit vaccines and will have several distinct advantages: 1) Antigens expressed by rVV are effective in inducing both cytotoxic T-lymphocyte (CTL) and humoral immune responses; 2) IFN-gamma attenuates VV virulence; 3) IFN-gamma will favor a Type 1 immune response, an important component of the immune response to virus infection to antigens; and 4) the inactivation of immune-modulating genes will increase the safety of rVVs.
