Most HIV-1 replication occurs in secondary lymphoid tissues in T cells within B cell follicles. Mechanisms underlying the accumulation of HIV-1-producing cells at these sites are not understood. Antiapoptotic proteins such as Bcl-2 could promote follicular CD4+ T cell survival, contributing to sustained virus production. Tonsils obtained from subjects without known HIV infection were disaggregated and analyzed for Bcl-2 expression in follicular (CXCR5+) and extrafollicular (CXCR5-) CD3+CD4+ cells by flow cytometry. Additional tonsil cells were cultured with phytohemagglutinin (PHA) and interleukin-2 (IL-2) for 2 days, infected with either CCR5(R5) or CXCR4-tropic (X4) GFP reporter viruses, and analyzed for Bcl-2 expression. In freshly disaggregated CD3+CD4+ tonsil cells, mean florescence intensity (MFI) for Bcl-2 was higher in CXCR5+ (median, 292) compared to CXCR5- cells (median, 194; p=0.001). Following in vitro stimulation with PHA and IL-2, Bcl-2 MFI was higher in both CXCR5+ cells (median, 757; p=0.03) and CXCR5- cells (median, 884; p=0.002) in uninfected cultures compared to freshly isolated tonsil cells. Bcl-2 MFI was higher in GFP+CD3+CD8- R5-producing cells (median, 554) than in X4-producing cells (median, 393; p=0.02). Bcl-2 MFI was higher in R5-producing CXCR5+ cells (median, 840) compared to all other subsets including R5-producing CXCR5- cells (median, 524; p=0.04), X4-producing CXCR5+ cells (median, 401; p=0.02), and X4-producing CXCR5- cells (median, 332; p=0.008). Bcl-2 expression is elevated in R5 HIV-1-producing CXCR5+ T cells in vitro, which may contribute to propagation of R5 virus in B cell follicles in vivo.
ASJC Scopus subject areas
- Infectious Diseases