Immunogenicity and protective efficacy of Gag/Pol/Env vaccines derived from temporal isolates of SIVmne against cognate virus challenge

Background  We used the SIVmne model to examine the relative immunogenicity and protective efficacy of vaccines derived from temporal isolates of lentivirus infection. SIVmne170 is a molecular clone isolated from a pig-tailed macaque 170 weeks after inoculation with SIVmneCL8. Methods  We immunized pig-tailed macaques with Gag/Pol/Env vaccines derived from CL8 or 170 and examined their protective efficacy against CL8, 170, or chimeras 8/170 and 170/8, containing the 5′ or 3′ half of the respective parental genomes. Results  As expected, CL8 vaccines protected animals against the CL8, but not the 170 virus. Surprisingly, 170 vaccines not only failed to protect against the 170 virus, but also the less pathogenic CL8. Chimeric virus challenges revealed that the envelope antigen of CL8 represents an important target for protective immunity. Conclusions  These results underscore the potential importance of targeting transmitted viruses through judicious choice of immunogens from early isolates for vaccine development.