The feasibility of vaccination against primate lentiviruses was first demonstrated in macaques vaccinated with inactivated virus. This potent protection was subsequently shown to be due to cellular rather than viral components within the vaccine. This type of xenogenic protection is induced by immunization with MHC class 1 or class 2 molecules and this is conferred by the passive transfer of serum from vaccinated animals. Allogeneic immunization with simian lymphocyte also induces protection against SIV grown in simian cells. These studies have indicated an alternative complimentary approach to immunization against HIV in man and emphasis the crucial importance of host components on the version surface. Vaccination with recombinant proteins of the virus is relatively ineffective in the macaques model. Complete protection against detectable infection has rarely been observed but initial virus load has been reduced. Live attenuated SIV induces the most potent protection yet observed in the macaque model. Animals infected with attenuated viruses resist infection by high doses of unattenuated virus and there is cross protection against antigenically distinct strains of virus. Furthermore, the animals resist infection following inoculation with viable SIV infected spleen cells. Live attenuated retroviruses are unlikely to be used in a human population as a vaccine against AIDS. Nevertheless, in the SIV macaque systems these viruses provide a unique resource with which to study mechanisms of protection against lentivirus infection.

Animal *Disease Models, Animal HIV Infections/PREVENTION & CONTROL Immunotherapy, Adoptive SIV/IMMUNOLOGY ABSTRACT

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