SPECIFIC AND NONSPECIFIC IMMUNITY AND PROTECTION OF MACAQUES AGAINST SIV INFECTION

The simian immunodeficiency virus is a retrovirus closely related to the human immunodeficiency viruses; it induces an AIDS-like disease in macaques, and provides therefore an obvious animal model for anti-lentiviral drug and vaccine strategy assessments. In our experiment, we immunized rhesus macaques with a purified and formalin-inactivated whole SIV(mac251) antigen preparation. Most of these monkeys were still protected for more than 4 months following a heterologous SIV(sm) intravenous challenge. Both virus stocks, for vaccine preparation and challenge, were provided by culture supernatants of infected T cells of human origin. Four of the protected macaques were then reimmunized with the same antigen preparation and rechallenged intravenously with a homologous rhesus cell grown SIV(mac251). Unexpectedly, all animals developed clinical and biological evidence of infection by day 15 after the second challenge.