SIV infection of macaques: a model for AIDS vaccine development

The SIV macaque model is an excellent surrogate for SIV infection of humans. Genital mucosal transmission of SIV presents the opportunity for testing the effectiveness of spermicides, pharmacologic agents and vaccines in preventing the heterosexual transmission of HIV. Because the incubation period is usually shorter and the disease tempo more rapid than seen with HIV infection, the endpoint for therapeutic, prophylaxis and vaccine trials can be reached sooner in the monkey model. Initial vaccine experiments using inactivated whole SIV mac did not protect rhesus macaques against IV or genital mucosal challenge with a moderately high dose of homologous live virus but did appear to delay disease in the IV challenge group. Similarly, a modified live SIVmac immunogen also failed to protect rhesus monkeys against IV challenge with live virus but did delay disease. It appears, therefore, that a strong immediate immune response to SIVmac, whether naturally or artificially induced can reduce the level of viremia and delay the onset of clinical SAIDS. We believe that these inactivated whole virus and modified live virus approaches are worth pursuing further and they may guide us towards an eventual effective vaccine for AIDS.