Objective: CD14+CD16+ monocytes are an important cellular target for HIV-1 entry and expand in the peripheral blood of HIV-infected individuals. Because CD14+CD16+ monocytes are a heterogeneous population and consist of CD14highCD16+ and CD14lowCD16+ subsets, we evaluated the effects of HIV infection on distinct subsets of CD16+ monocytes.
Methods: Untreated HIV-infected patients were recruited to investigate the relationship between the proportions of monocyte subsets with plasma viral loads and CD4+ T-cell counts. Patients receiving highly active antiretroviral therapy (HAART) were followed up in a cross-sectional and a longitudinal study.
Results: Compared with CD14lowCD16+, CD14highCD16+ monocytes showed higher levels of CD64 and HLA-DR antigens, which imply that these 2 distinct subsets have different immunoregulatory phenotypes. In HAART-naive patients, elevated proportions of CD14highCD16+ monocytes were correlated with increased viral loads and decreased CD4+ T-cell counts, whereas CD14lowCD16+ monocytes did not show such correlation with disease progression. Of importance, HAART recovered the proportion of CD14highCD16+ monocytes, whereas CD14lowCD16+ monocytes did not decrease during 1 year of antiviral therapy.
Conclusions: Taken together, our observations elucidate distinct immune responses of monocyte subsets during HIV infection and antiviral therapy and provide new insight into the roles of innate immunity in HIV-related pathogenesis.