Human CD4+ CD25+ regulatory T cells control T-cell responses to human immunodeficiency virus and cytomegalovirus antigens

Abstract

Regulatory T (T(R)) cells maintain tolerance to self-antigens and control immune responses to alloantigens after organ transplantation. Here, we show that CD4(+) CD25(+) human T(R) cells suppress virus-specific T-cell responses. Depletion of T(R) cells from peripheral blood mononuclear cells enhances T-cell responses to cytomegalovirus and human immunodeficiency virus antigens. We propose that chronic viral infections lead to induction of suppressive T(R) cells that inhibit the antiviral immune response.

Figures

FIG. 1.

TR cells suppress superantigen-induced cytokine production. IFN-γ expression in T cells in PBMC was compared with that of T cells in PBMC depleted of CD25+ cells (a). The cultures were stimulated for 18 h with SEB. Brefeldin A was added for the last 5 h to promote cytokine accumulation. Means ± standard errors of the mean are shown (n = 3). (b) CD25+ T cells were added back into PBMC depleted of CD25+ cells at increasing ratios. The CD25+ T cells were stained with CFSE before being added back and were gated out of the analysis. (c) CD25+ T cells and sorted CD25+ CD4+ T cells (>99% pure) were added back into PBMC depleted of CD25+ cells. Means ± standard errors of the mean are shown (n = 2).

FIG. 2.

Suppressive CD25+ T cells can be induced from PBMC depleted of CD25+ T cells after activation with SEB. PBMC were depleted of CD25+ cells (a), labeled with CFSE, and cultured in the presence of SEB for 7 days (b). At day 7 (c), the CD25+ and CD25− cell fractions were added into fresh PBMC cultures from the same donor. The cocultures were stimulated for 18 h with SEB. Brefeldin A was added for the last 5 h to promote cytokine accumulation. The CFSE-stained cells added into the fresh PBMC at day 7 were gated out of the analysis. Representative data are shown.

FIG. 3.

The frequency of TR cells in HIV patients is unaltered. PBMC from HIV patients (n = 10) and healthy subjects (n = 10) were stained with fluorochrome-labeled monoclonal antibodies and analyzed for the frequencies of CD4+ CD25+ T cells and CD8+ CD38+ T cells. Means ± standard errors of the mean are shown.

FIG. 4.

TR cells suppress antiviral immune responses. PBMC from a healthy CMV-infected individual were stained with a CMV pp65 tetramer and with cell surface markers (a). The frequency of tetramer-positive CD8+ T cells was compared with the frequency of IFN-γ-expressing T cells in PBMC, PBMC cultures depleted of CD25+ cells, and PBMC cultures depleted of CD25+ cells to which the depleted cells were added back in a 1:3 ratio. PBMC from an HIV-infected subject were stimulated with HIV antigens (b). The frequencies of IFN-γ- and TNF-α-expressing T cells in PMBC cultures and PBMC cultures depleted of CD25+ cells were compared. Representative data are shown.

FIG. 5.

Depletion of TR cells enhances the antiviral immune response to HIV. PBMC from HIV-infected subjects (n = 6) were stimulated with HIV and CMV antigens. The frequencies of IFN-γ- and TNF-α-expressing T cells in PMBC cultures and PBMC cultures depleted of CD25+ cells were compared. The cells were gated on the CD3+ CD8− and CD3+ CD8+ T cells. The shaded area in each graph represents the level of detection. Note: the scale on the y axis differs in the panels.