Prolonged clinical latency and survival of macaques given a whole inactivated simian immunodeficiency virus vaccine

Simian immunodeficiency virus (SIV) infection of macaques is a useful and relevant model for evaluating candidate human immunodeficiency virus (HIV) vaccines. One important feature of this model is that SIV vaccines can be evaluated for their ability to prevent infection as well as to prevent or delay the onset of AIDS. In the present study, a group of macaques was vaccinated with whole inactivated SIV and challenged with peripheral blood mononuclear cells from an SIV-infected macaque. This challenge represented a rigorous and realistic test of the immunization protocol. All macaques became infected after challenge; however, immunized animals survived significantly longer (P <.03) than naive controls. These data suggest that similar vaccines administered to humans at risk for HIV-1 infection might delay or prevent AIDS even if the vaccine failed to prevent infection.