Increased Frequency of CD49b/LAG-3⁺ Type 1 Regulatory T Cells in HIV-Infected Individuals

In HIV-1 infection elevated serum levels of interferon-α (IFN-α) and interleukin-10 (IL-10) are associated with immune hyperactivation and disease progression. Recently, coexpression of CD49b and LAG-3 was shown to identify Type 1 regulatory T (Tr1) cells, which secrete large amounts of the immunosuppressive cytokine IL-10. We analyzed the frequency of CD49b/LAG-3⁺ Tr1 cells in the peripheral blood of HIV-infected individuals at different stages of the disease. We found increased levels of CD49b/LAG-3⁺ Tr1 cells as well as IL-10 in HIV patients. With disease progression, Tr1 cells negatively correlate with frequency of plasmacytoid dendritic cells (pDCs), the main producers of IFN-α. However, elevated IL-10 levels could not be ascribed to the CD49b/LAG-3⁺Tr1 cell population. Moreover, we showed in vitro that IFN-α leads to an upregulation of IL-10 as well as CD49b/LAG-3⁺ Tr1 cell counts in healthy controls, recapitulating effects observed in vivo during HIV infection. Our results suggest that overexpression of IFN-α during HIV infection drives the generation of CD49b/LAG-3⁺ Tr1 cells and the immunosuppressive cytokine IL-10. Furthermore, it remains unclear whether elevated IL-10 levels are beneficial or detrimental in regard to disease progression.