BLOOD MONOCYTES FROM MOST HUMAN-IMMUNODEFICIENCY-VIRUS TYPE 1-INFECTED PATIENTS DO NOT CARRY PROVIRAL DNA

In blood, the CD4(+) T cells of patients with human immunodeficiency virus type 1 (HIV-1) harbor HIV-1; however, whether the CD4(+) blood monocytes carry the virus is controversial. Tissue macrophages are known to be infected. To determine if blood monocytes from HIV-1-seropositive patients contain HIV-1, we separated monocytes and T-cell subsets by using monoclonal antibodies bound to magnetic beads and by monocyte adherence to glass. Monocytes were cultured with macrophage colony-stimulating factor, granulocyte-macrophage colony stimulating factor, and interleukin-3. After 14 days in culture, cells were analyzed for the presence of HIV-1 antigen and multinucleated giant cells (MGCs). Freshly isolated cell subsets were analyzed for HIV-1 proviral DNA by PCR with modified env (SK68i and SK69i2) and gag (SK145i and SK150) primers. We found that (i) monocytes cultured without depletion of CD4(+) T cells (11 of 11 patients) were HIV-1 antigen positive and showed dramatically increased spontaneous formation of MGCs, (ii) monocytes cultured after depletion of CD4(+) T cells (three experiments) were HIV-1 antigen negative and showed markedly decreased MGC formation, and (iii) in specimens from 14 patients subsequently analyzed by PCR, purified CD4(+) T cells were positive for HIV-1 proviral DNA in all patients. In 11 of 14 patients (79%), the monocyte fractions were HIV-1 proviral DNA negative, while in the remaining 3 patients, the monocytes were positive for HIV-1 proviral DNA. In conclusion, the major reservoir for HIV-1 infection in human Peripheral blood is the CD4(+) T cell (14 of 14 cases). Fresh blood monocytes from HIV-1 seropositive patients were HIV-1 proviral DNA negative in 11 of 14 cases (79%). Blood monocyte-derived macrophages from HIV-1-seropositive patients may acquire HIV-1 infection in vitro from contaminating infected CD4(+) T cells. The pathogenic and clinical significance of HIV-1-infected monocytes (found in 21% of patients) remains to be determined.