We previously demonstrated that HIV envelope glycoprotein (Env), delivered in the form of a vaccine and expressed by dendritic cells or 293T cells, could suppress Ag-stimulated CD4+ T cell proliferation. The mechanism remains to be identified but is dependent on CD4 and independent of coreceptor binding. Recently, CD4+ regulatory T (Treg) cells were found to inhibit protective anti-HIV CD4+ and CD8+ T cell responses. However, the role of Tregs in HIV remains highly controversial. HIV Env is a potent immune inhibitory molecule that interacts with host CD4 + cells, including Treg cells. Using an in vitro model, we investigated whether Treg cells are involved in Env-induced suppression of CD4+ T cell proliferation, and whether Env directly affects the functional activity of Treg cells. Our data shows that exposure of human CD4+ T cells to Env neither induced a higher frequency nor a more activated phenotype of Treg cells. Depletion of CD25+ Treg cells from PBMC did not overcome the Env-induced suppression of CD4+ T cell proliferation, demonstrating that CD25+FoxP3+ Treg cells are not involved in Envinduced suppression of CD4+ T cell proliferation. In addition, we extend our observation that similar to Env expressed on cells, Env present on virions also suppresses CD4+ T cell proliferation.
ASJC Scopus subject areas
- Immunology and Allergy