DESCRIPTION: The mucosal surfaces of the gastrointestinal tract play a fundamental role in the pathogenesis of HIV-1 infection. However, the mucosal events in HIV-1 disease have received little investigative attention. Therefore, to investigate how primary human intestinal epithelial cells, macrophages and lymphocytes interact with HIV-1 and whether receptor-mediated events results in selective transmission of macrophage-tropic, CCR5 (2b/3)-dependent, NSI virus strains, we propose the following hypotheses: 1) Productive HIV-1 infection of lamina propria mononuclear cells is initiated by a non-CD4-dependent, non-chemokine receptor-mediated epithelial transfer process that efficiently delivers both SI and SNI virus to subepithelial intestinal mononuclear cells; 2) Because of the predominance of activated macrophages bearing exclusively CCR5(2b/3) receptor compared with the lower frequency of activated CD4+_ lymphocytes, macrophage-tropic NSI viruses are preferentially transmitted; and 3) Active production of chemokines (RANTES, MIP-1a, MIP-1B, SDF-1, and others) in the local mucosal microenvironment substantially influences virus replication and propagation, leading to down-modulation of local HIV-1 production and partial virological containment. Therefore, using our newly developed technique for the isolation and purification of mucosal cells, we will address the above hypotheses with the following specific aims: 1. Determine whether primary gastrointestinal epithelial cells are permissive to HIV-1 entry, support viral replication and/or transfer infectious HIV-1 to primary resident mucosal macrophages and lymphocytes, and define the mechanisms(s) by which intestinal epithelial cells transfer virus to lamina propria cells. 2. Determine whether primary lamina propria macrophages from normal intestine constitutively produce CC chemokines (RANTES, MIP-la or MIP-lb), whether HIV-1 infection of the cells upregulates CC chemokine production, and whether constitutively produced CC chemokines can in turn down-modulate HIV-1 infection of the macrophages. 3. Determine the relative efficiency with which primary intestinal epithelial cells, lamina propria macrophages and lamina lymphocytes alone, and together as a reconstituted model of intestinal mucosa, select for HIV-1 subpopulations derived from genetically defined mixtures of SI and NSI virus and from clinical specimens obtained from acute HIV-1 seroconvertors and their sexual partners.