CD38 expression on CD8 T lymphocytes as a marker of residual virus replication in chronically HIV-infected patients receiving antiretroviral therapy.

The level of CD8+ CD38+ T lymphocytes in blood correlates with disease progression in HIV-infected individuals, independently of the CD4 count. Effective antiretroviral therapy reduces this lymphocyte subset in parallel with plasma viremia, although CD38 expression on CD8+ cells does not normalize completely in most subjects, and might reflect residual HIV replication. The expression of CD38 on CD8+ cells (as number of CD38 molecules per CD8+ cell) was measured quantitatively by flow cytometry in 200 individuals, of whom 170 were HIV positive and 30 were HIV-uninfected controls. Forty-six HIV-infected subjects were on antiretroviral therapy and had undetectable viral load. The remaining 124 HIV-positive persons were not on therapy and had detectable plasma viremia. The mean level of CD38 on CD8+ cells was higher in HIV-positive, untreated patients than in subjects on antiviral therapy and controls (5023, 2029, and 1978 molecules per CD8+ cell, respectively, p < 0.01). In HIV-positive, untreated subjects, the higher CD38 expression mainly occurred on CD45RO+ CD8+ cells. The level of CD38 strongly correlated with plasma HIV-RNA (r = 0.63, p < 0.001). The levels of CD38 on CD8+ cells declined steadily in HIV-positive subjects after beginning antiretroviral therapy. A few individuals presented viral blips whereas being on antiviral treatment, levels of CD38 on CD8+ cells increased transiently in parallel with episodes of viral replication. Levels of CD38 on CD8+ cells are increased in chronic HIV infection, and strongly correlate with plasma viremia. The slow decline of CD38 expression on CD8+ cells over time in subjects with undetectable plasma viremia while being on antiretroviral therapy suggests that CD38 expression on CD8+ cells could be used as a marker of residual virus replication.