We are investigating the immunologic and virologic consequences of infection with simian immunodeficiency viruses engineered to incorporate elements of human immunodeficiency viruses, when introduced into nonhuman primates. We have previously reported the development of both nonpathogenic and pathogenic virus trains. In 1997 we reported our investigations into both T-cell mediated and humoral immunity elicited by infection with these chimerical viruses (SHIVs). We found that SHIV infection in rhesus monkeys elicits HIV-1 Envelope-specific CD4+ T helper cells, and we identified recognized epitopes and the restricting MHC alleles. we also analyzed immunoglobulin Vh gene usage during primary infection of rhesus monkeys with SHIVs and found no consistent Vh-specific alterations in the immunoglobulin repertoire, which suggests that the HIV-1 Envelope expressed by these SHIVs does not contain a putative B cell superantigen.