Efficient macrophage isolation of human immunodeficiency virus from peripheral blood leukocytes from healthy seropositive individuals: implications for cell tropism.

We investigated the efficiency of HIV isolation from the PBL of 23 healthy, HIV-seropositive individuals with high (600-700/mm3) CD4+ T cell counts. Cocultivations of patients' PBL with allogeneic T lymphocyte blasts or monocytes were performed. T lymphocyte blasts allowed recovery of 4/23 (17%) HIV isolates, whereas monocytes allowed recovery of 12/23 (52%) isolates. Monocyte cultures sustained release of viral antigen for up to 70 days. Nine of the viral isolations could be accomplished only with this monocyte coculture technique. To determine the in vivo source of the macrophage-tropic HIV isolates we separated PBL from 5 of these 9 patients into T lymphocyte and monocyte fractions by cell sorting; then, we analyzed the fractions by PCR to amplify HIV proviral DNA. In 4 out of 5 patients studied HIV-1 proviral DNA was detected only in T lymphocytes but not in monocytes, although the virus was isolated exclusively by monocyte coculture technique. In the remaining patient, HIV DNA was found to be present in both T cells and monocytes. Thus, HIV can be more efficiently isolated in healthy seropositive individuals by coculture of their PBL with normal monocytes rather than T cell blasts. Of note, the most common in vivo source of viral isolates which preferentially infect monocytes in vitro ("macrophage-tropic strains") is the circulating CD4+ T lymphocyte.