Cross-protection against mucosal simian immunodeficiency virus (SIVsm) challenge in human immunodeficiency virus type 2-vaccinated cynomolgus monkeys

In this study we compared the efficacy of live attenuated human immunodefic iency virus type 2 (HIV-2) vaccine alone versus boosting with live non-path ogenic HIV-2 following priming with ALVAC HIV-2 (recombinant canarypox viru s expressing HIV-2 env, gag and pol). Six monkeys were first inoculated int ravenously with live HIV-2(SBL-6669) and 7 to 10 months later were challeng ed intrarectally with 10 MID50 of cell-free simian immunodeficiency virus ( SIV) strain SIVsm. One monkey was completely protected against SIV infectio n and all five monkeys that became SIV-infected showed a lower virus replic ation and an initial lower virus load as compared with a parallel group of six control animals. In another experiment five monkeys were immunized eith er three times with ALVAC HIV-2 alone or twice with ALVAC HIV-2 and once wi th purified native HIV-2 gp125. The monkeys were then challenged with HIV-2 given intravenously and finally with pathogenic SIVsm given intrarectally. After challenge with SIVsm, three of five monkeys were completely protecte d against SIVsm infection whereas the remaining two macaques became SIV-inf ected but with limited virus replication. In conclusion, vaccination with a n ALVAC HIV-2 vaccine followed by exposure to live HIV-2 could induce cross -protection against mucosal infection with SIVsm and seemed to be more effi cient than immunization with a live HIV-2 vaccine only.