Abstract
Human immunodeficiency virus (HIV) disease is associated with loss of CD4
+
T cells, chronic immune activation, and progressive immune dysfunction. HIV-specific responses, particularly those of CD4
+
T cells, become impaired early after infection, before the loss of responses directed against other antigens; the basis for this diminution has not been elucidated fully. The potential role of CD25
+
CD4
+
regulatory T cells (T reg cells), previously shown to inhibit immune responses directed against numerous pathogens, as suppressors of HIV-specific T cell responses was investigated. In the majority of healthy HIV-infected individuals, CD25
+
CD4
+
T cells significantly suppressed cellular proliferation and cytokine production by CD4
+
and CD8
+
T cells in response to HIV antigens/peptides in vitro; these effects were cell contact dependent and IL-10 and TGF-β independent. Individuals with strong HIV-specific CD25
+
T reg cell function in vitro had significantly lower levels of plasma viremia and higher CD4
+
: CD8
+
T cell ratios than did those individuals in whom this activity could not be detected. These in vitro data suggest that CD25
+
CD4
+
T reg cells may contribute to the diminution of HIV-specific T cell immune responses in vivo in the early stages of HIV disease.
