The need is pressing to develop an effective and safe vaccine against the human immunodeficiency virus (HIV) with the primary objective of arresting the spread of the AIDS epidemic. Studies in non-human primates, with simian immunodeficiency virus (SIV) and chimeric virus (SHIV) have demonstrated that live attenuated viruses are highly effective; however, such vaccines maintain a low level of pathogenicity. We have been investigating live-attenuated feline immunodeficiency virus (FIV) vaccines for inducing protective immunity in cats (Preliminary Results). One such vaccine was made by constructing a FIV proviral clone with a large deletion in the viral infectivity factor (vif) gene. In a novel approach to immunization with live attenuated viral vaccines; cats were inoculated by the intramuscular route with plasmid DNA containing the FIV-delta vif proviral genome. In two independent experiments, this vaccine protocol was effective in preventing infection with challenge virus given by the parenteral route. The current grant proposal aims to extend this approach to anti-AIDS vaccine development in non-human primates. Accordingly, we plan to use SIV infection of rhesus macaques to evaluate a live-attenuated viral vaccine by inoculating these animals with plasmid DNA containing an SIV-delta vif provirus. Because the majority of HIV infections are the result of transmission via mucosal membranes, macaques inoculated with this DNA vaccine will be challenged with virulent virus administered via vaginal mucosa. In addition, by building on recent knowledge of immunomodulators in viral immunity, we will test key cytokines and chemokines as potential adjuvants by engineering the SIV-delta vif provirus to express these immunomodulators. The DNA forms of such proviral vectors, expressing cytokines or chemokines, will also be inoculated into macaques for evaluation in challenge experiments. Because this project will also conduct extensive investigations of anti-viral immune responses in DNA vaccinated animals, it may be possible to identify correlates of immunity that protect individuals from mucosal transmission of virus. Knowledge gained in this project on the SIV/macaque model will set the stage for evaluation of a DNA vaccine for preventing HIV-1 infection and AIDS in humans.