HIV-1 Infects and Alters Immune Function of a Monocyte Subset Expressing Low CD14 Surface Phenotype

Monocytes represent a leukocyte subset that express high levels of CD14 on their surface (CD14-high). These cells play a critical role in the pathogenesis of HIV-1 infection. In the present study, we have identified a monocyte subset expressing an extremely low level of CD14 (CD14-low), and examined their susceptibility to HIV-1 infection. Phenotypic analysis by flow cytometry of these cells revealed a low level of CD4, but the absence of CD3, CD14, CD19, and CD83 surface markers. Both CD14-low and CD14-high cell populations expressed CD13 and CD33 markers on their surface, suggesting these cells to be of myeloid origin. Morphologically, CD14-low cells were indistinguishable from CD14-high cells. CD14-low cells were susceptible to infection with a monocytotropic strain of HIV-1 (HIV_ADA)- However, like CD14-high monocytes, CD14-low cells could not be productively infected with a T cell tropic strain of HIV-1 (H9/HTLV_IIIB). Similar to CD14-high monocytes, CD14-low cells were capable of inducing antigen-stimulated CD4⁺ T-cell proliferation. HIV-1 infection substantially reduced their ability to induce antigen-stimulated T-cell proliferation. These data indicate that CD14-low cells belong to the monocyte lineage and may play an important role in the immunopathogenesis of HIV-1 infection.