The genetic relatedness of SIVcpz and HIV-1 supports the hypothesis of cross-species transmission and suggests that the three main groups of HIV-1 (M, O, and N), all found in Cameroon, are a result of separate introductions into humans. The Cameroon population is genetically diverse, with more than 250 ethnic groups living in isolated villages. Because cross-species transmissions may occur in distinct pockets of genetic diversity in Cameroon, recently introduced SIV/HIV-1 strains could be evolving separately in small and remote communities before spreading and further evolving in urban centers where the human genetic environment consists of a composite from various groups and locales. Furthermore, because the divergence of the subtypes may have originally occurred or may be occurring in a few ethnic groups where human genetic diversity is limited by cultural and geographic factors, the divergence of SIV/HIV-1 strains within each ethnic group may also be limited, resulting in relatively restricted immunologic and biologic characteristics. Studies are urgently needed at this point in time to understand the evolution of SIV/HIV in distinct local communities because new roads are linking these communities and thus increasing interaction. In addition, infection with multiple HIV groups or subtypes, or with recombinant viruses, has been documented in urban areas of Cameroon, yet little is known of the evolution of these viruses. Because information about viruses which have evolved little from their SIV ancestors is lacking, as is information about viruses from multiple and recombinant HIV infections, we propose the following work: AIM l: To identify the distribution of HIV-1 variants circulating in different human ethnic groups, risk groups, and geographic locales in Cameroon and to study whether specific strains of HIV-1 exist exclusively or preferentially within any of these study populations. AIM 2: To study the antigenic and biologic characteristics of the HIV-1 strains found in AIM 1 and determine how their characteristics correlate with the different ethnic groups, risk groups, and geographic locales in which they are found. AIM 3: To monitor the viral evolution and disease progression in patients infected with multiple HIV-1 groups/subtypes, recombinants and "pure subtypes": AIM 4: To compare the rates and nature of mutations of viruses (as a measure of viral evolution) from persons infected with inter-subtype recombinants and "pure subtypes" and to correlate these changes with the host's humoral immune response. AIM 5: To identify the distribution of SIVcpz-like infections among non-human primate pets in the different geographic locales of Cameroon.