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BackgroundWe evaluated the effect of different doses of pegylated interferon (PEG-IFN)-α2a/ribavirin (RBV) on several T-cell activation markers in HIV–HCV-coinfected patients and their relationship with changes in plasma HCV RNA.MethodsFrozen peripheral blood mononuclear cells (PBMCs) from 22 patients receiving two different PEG-IFN-α2a schedules were analysed by six-colour flow cytometry. Cell-surface expression of CD38 was quantified. HIV and HCV viral loads, as well as absolute CD4+and CD8+T-cell counts, were recorded during the follow up (72 weeks).ResultsPEG-IFN-α2a/RBV treatment decreased the absolute numbers of CD8+and CD4+T-cells. The decrease in CD8+T-cells was more pronounced, resulting in increased percentages of CD4+T-cells. Percentages of naive/memory CD4+T-cell subsets remained unchanged, although the percentage of CD38+CD45RO+cells significantly increased. By contrast, the CD8+T-cell compartment significantly reduced the percentage of CD45RO+cells and HLA-DR+cells, whereas the percentage of CD38 expressing cells was increased because of a significant increase in cell-surface CD38 expression. Changes in CD8+T-cells were similar for both PEG-IFN-α2a/RBV doses, but high doses induced more severe perturbations in CD4+T-cells. All changes returned to baseline levels after treatment cessation and, except for the loss of naive CD4+T-cells, were not associated with virological response.ConclusionsTransient lymphopaenia induced by PEG-IFN-α2a/RBV differentially affects T-cell subsets. Activated HLA-DR+and CD45RO+cells were selectively reduced in peripheral blood, whereas CD38 expression was up-regulated mainly in memory cells. Increasing PEG-IFN-α2a/RBV doses mainly affect CD4+T-cells but failed to modify clinical outcome.