Genetic analysis of a new subgroup of human and simian T-lymphotropic retroviruses: HTLV-IV, LAV-2, SBL-6669, and STLV-IIIAGM.

A new primate retrovirus, STLV-IIIAGM, has been recently isolated from healthy African green monkeys and is apparently nonpathogenic in its natural host. However, spontaneous infection as well as inoculation of STLV-IIIAGM into macaques induces a disease with clinical features that resemble human AIDS. Independent isolates of human retroviruses, serologically closely related to STLV-IIIAGM, have been obtained from healthy individuals (HTLV-IV) and patients with immunodeficiency (LAV-2FG and SBL 6669) from West Africa. The latter have also been referred to as HIV-2 because, like HTLV-III/HIV-1, they may be associated with immune deficiency, or as West African human retroviruses because of their prevalence and probable origin from that region. We have molecularly cloned the STLV-IIIAGM genome and have generated probes from the gag-pol and envelope genes to analyze the genetic relatedness of these simian and human retroviruses. Our results indicate that all these retroviruses are genetically closely related to each other, HTLV-IV and STLV-IIIAGM differing only by a few restriction enzyme sites while LAV-2FG and SBL 6669 exhibit greater polymorphism from HTLV-IV/STLV-IIIAGM. These data mirror the variable degree of relatedness among members of the first subgroup of human retroviruses, HTLV-III/HIV.