HLA-DR integrates with HIV-1 at chronic disease stage, may raise infectivity

The incorporation of human lymphocyte antigen class II (HLA-DR) into the envelope of HIV-1 varies with the stage of the infection, according to a report in the Journal of Virology. HLA-DR becomes part of the HIV-1 membrane as the virus buds from the host cell membrane, the authors explain. There it remains functional, serving as an adhesion molecule and likely enhancing the infectivity of the virus.

Dr Stephen Lawn and Dr Salvatore Butera from the Centers for Disease Control and Prevention in Atlanta, Ga, determined the levels of HLA-DR incorporation by HIV-1 in patients with early infection, chronic infection, and in those with treated and untreated active tuberculosis. None of the 22 patients studied were receiving antiretroviral treatment.

All patients with chronic HIV-1 infection, regardless of CD4 cell count, had detectable virus-associated HLA-DR, the authors report. In contrast, HLA-DR was not detectable in the HIV-1 from patients with early infection. This latter finding suggests that inactive, HLA-DR – negative cells can harbour HIV-1 infection, a result consistent with other studies. The percentage of HLA-DR – positive HIV-1 was 3.1 times greater among patients with untreated active pulmonary tuberculosis than among patients with chronic infection, the researchers note. Once tuberculosis treatment resulted in conversion of sputum samples to negative, HLA-DR – positive HIV-1 percentages fell to the usual level seen in chronically infected patients.

This “reversible increase in incorporation of HLA-DR by HIV-1 in vivo … may represent an important mechanism whereby tuberculosis and potentially other opportunistic infections enhance HIV-1 pathogenesis,” the authors conclude.