Identification of HIV-1-specific regulatory T-cells using HLA class II tetramers

Abstract

Regulatory T cells (Tregs) are potent immune modulators, but their precise role in HIV pathogenesis remains incompletely understood. Most studies to date have focused on frequencies or phenotypes of 'bulk' Treg populations. However, although antigen-specific Tregs have been reported in other diseases, HIV-1 epitope-specific Tregs have not been described to date. We here report the first identification of functional HIV-1-Gag-specific regulatory T cells using human leukocyte antigen class II tetramer staining in HIV-1-infected individuals.

Figure 1

a) Representative example of CD4⁺ regulatory T-cell (Treg) staining by flow cytometry with gating strategy before flow-based sorting and Treg expansion. Tregs are defined as CD25⁺CD127^low CD4⁺ T cells. b) Mean expansion fold change of the expanded regulatory T-cells lines that were stained with HIV-1-p24-gag-specific HLA class II tetramer. c) Representative histogram plots showing T-cell proliferation by CFSE dilution of CD8⁺ T cells after 4 days of culture following stimulation with anti-CD3/CD2/CD28 coated beads, cocultured with (lower histogram) or without expanded Tregs (upper histogram) at a ratio of 1:1 Treg per PBMC. d) Example of PE-conjugated-HLA class II tetramer staining on expanded Tregs isolated from an individual with untreated chronic progressive HIV-1 infection before and after PE-enrichment over a magnetic column. The cells were incubated alone (upper dot plot), in presence of an HLA-DR0401 restricted HLA-class II tetramer loaded with a control CLIP peptide (middle dot plots) or the p24-Gag peptide DRFYKTLRAEQASQ (lower dot plots). Percentages refer to tetramer positive cells per total CD4⁺ T-cells. Equal numbers of input cells were used for all staining and enrichment procedures.