Frequency of cells positive for HIV-1 sequences assessed by in situ polymerase chain reaction

HIV-1 infection of humans causes immunosuppression. The determination of precise levels of HIV-1 infection of cells in vivo may assist in the understanding of the pathogenetic processes involved in clinical infection with this virus. Studies using polymerase chain reaction have demonstrated higher levels of HIV-1 provirus in unfractionated peripheral blood mononuclear cells of infected subjects than many previous studies.

We developed a new, highly sensitive, polymerase chain reaction method that amplifies selected genetic regions within intact single cells. We used this technique before and after immunomagnetic bead separation to determine the proportion of unfractionated peripheral blood mononuclear cells and CD4+ lymphocytes carrying the HIV-1 provirus in infected subjects in different stages of disease.

None of the peripheral blood mononuclear cells from 11 HIV-1-seronegative subjects were positive for HIV-1 provirus by the in situ polymerase chain reaction method. In 56 subjects infected with HIV-1, the percentage of peripheral blood mononuclear cells with HIV-1 ranged from 0.1 to 13.5%. CD4+ lymphocytes infected with HIV-1 ranged from 0.2 to 69% in the 42 HIV-1-infected subjects evaluated. The percentages of HIV-1-infected CD4+ lymphocytes increased significantly with an advancing stage of disease. The proportion of peripheral blood mononuclear cells infected with HIV-1 appeared to be at least 10 times higher than previously described.

These data suggest that in certain infected patients, high levels of infected lymphocytes may harbor the HIV-1 provirus.