Inexpensive vaccines and rapid diagnostic kits tailor-made for the global eradication of rinderpest, and technology transfer to Africa and Asia.

Rinderpest is an acute and highly contagious viral disease of ruminants, often resulting in greater than 90% mortality. We previously reported the development of first- and second-generation recombinant vaccinia virus vaccines which provide complete protection against rinderpest virus (RPV) and peste-des-petits ruminants virus (PPRV). These vaccines are safe even for immunodeficient mice and macaques with acquired immunodeficiency syndrome. We developed a third-generation recombinant vaccinia virus vaccine (v2RVFH) that expresses the fusion and haemagglutinin genes of RPV under strong synthetic vaccinia virus promoters. Cattle vaccinated intramuscularly with as little as 10(3) plaque-forming units (PFU) of v2RVFH were completely protected from rinderpest. Vaccinated animals did not develop pock lesions or transmit v2RVFH to contact animals. Cattle vaccinated with a standard dose of 10(8) PFU of v2RVFH developed long-term, sterilizing immunity against rinderpest. Thus, v2RVFH is safe, efficacious, heat stable, inexpensive, easily administered, and allows serological differentiation between vaccinated and infected animals. To aid in diagnosis and differentiation of vaccinated from infected animals, we developed indirect ELISAs (iELISAs) that use baculovirus-expressed RPV or PPRV nucleoprotein as coating antigens. A single larva contains enough viral antigen to test more than 10,000 serum samples, in duplicate. African scientists trained at the ILMB successfully transferred the iELISA kit technology to more than 30 countries in Africa, providing a model for technology transfer among developing countries. Vaccination with v2RVFH, in conjunction with the iELISA kits, greatly enhances the prospects for global eradication of rinderpest, as developing nations achieve independence in control efforts.

Vaccinia virus vectors with an inactivated gamma interferon receptor homolog gene (B8R) are attenuated In vivo without a concomitant reduction in immunogenicity.

The vaccinia virus (VV) B8R gene encodes a secreted protein with homology to the gamma interferon (IFN-gamma) receptor. In vitro, the B8R protein binds to and neutralizes the antiviral activity of several species of IFN-gamma, including human and rat IFN-gamma; it does not, however, bind significantly to murine IFN-gamma. Here we report on the construction and characterization of recombinant VVs (rVVs) lacking the B8R gene. While the deletion of this gene had no effect on virus replication in vitro, rVVs lacking the B8R gene were attenuated for mice. There was a significant decrease in weight loss and mortality in normal mice, and nude mice survived significantly longer than did controls inoculated with parental virus. This is a surprising result considering the minimal binding of the B8R protein to murine IFN-gamma and its failure to block the antiviral activity of this cytokine in vitro. Such reduction in virulence could not be determined in rats, since they are considerably more resistant to VV infection than are mice. Finally, deletion of the B8R gene had no detectable effects on humoral immune responses. Mice and rats vaccinated with the rVVs showed identical humoral responses to both homologous and heterologous genes expressed by VV. This study demonstrates that the deletion of the VV B8R gene leads to enhanced safety without a concomitant reduction in immunogenicity.

Enhanced safety and efficacy of live attenuated SIV vaccines by prevaccination with recombinant vaccines.

The only vaccines shown to be protective against intravenous challenge with virulent virus in the simian immunodeficiency virus (SIV)/macaque model are attenuated live SIVs. However, these vaccines have several disadvantages: 1) they persist indefinitely in vaccinated macaques; 2) they are pathogenic to neonatal macaques; and 3) they are lethal in some adult macaques. To enhance the safety and efficacy of these vaccines, we immunized macaques first with recombinant vaccines and then inoculated the animals with SIV(delta(nef)). In the first experiment, preimmunized macaques advanced to disease slower than controls after challenge with virulent SIV; five animals survived for 3 years without disease and only the vaccine virus (SIV(delta(nef)) could be isolated at this time. In the second experiment, preimmunized animals had lower virus loads and no disease compared to controls.