Blood monocytes from patients with active pulmonary tuberculosis and age-matched healthy purified protein derivative-reactive donors were infected with human immunodeficiency virus type 1 (HIV-1)JR-FL in vitro to assess their susceptibility to productive infection by HIV-1. HIV-1 p24 levels (enzyme-linked immunosorbent assay) in supernatants of infected cells from patients with tuberculosis, albeit variable, were significantly higher at days 10-20 of culture; the maximum levels of p24 antigen were greater in supernatants of HIV-1-infected monocytes from patients than maximum levels for controls (p < 0.05). The maximum increment in p24 levels for patients also exceeded that for controls (p < 0.05). Entry of HIV-1 and/or initiation of reverse transcription, measured by polymerase chain reaction using HIV-1 R/U5 primer pairs, was variable and low in infected monocytes from both patients and controls, and did not correlate with HIV-1 p24 levels. The frequency of infected cells as assessed by endpoint dilution viral cultures was similar for both groups. Therefore, blood monocytes from patients with active tuberculosis can develop a highly productive infection with HIV-1 that does not appear to be due to enhanced HIV entry or higher frequency of infected cells. The enhanced susceptibility may result directly from activation of monocytes by exposure to Mycobacterium tuberculosis and its products in situ.

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