Abstract
Central memory (T(CM)) cells are a subpopulation of CD4 T cells that sustain overall CD4 T cell counts in HIV infection. The mechanisms underlying their eventual demise, which leads to loss of CD4 T cell counts, are not known. To understand their proneness to death despite their increased movement to proliferation, we examined cell division together with possible cell accumulation in different phases of the cell cycle. Purified circulating T(CM) cells from untreated people living with HIV (PLWH) (n = 9) and healthy controls (n = 10) were stimulated in vitro using anti-CD3/CD28 agonistic antibodies plus IL-2 and cultured for 4 days. Cell viability, DNA content, proliferation, and cyclin A and cyclin B expression were measured. We found that PLWH T(CM) cells more frequently had a DNA content lower than G0/G1, compared with controls (p = .043). These cells accumulated with each division. The proportion of cells with sub-G0/G1 DNA content that were cycling (expressing cyclin A) was greater in the PLWH group (p = .003). The percentage of T(CM) cells expressing cyclin A+ among those in G0/G1 and was also greater in the PLWH group (p = .043), suggesting arrest before G2/M. While T(CM) cells from PLWH can proliferate, during this process some of them accumulate defects in DNA content that are incompatible with viability, suggesting that they could be intrinsically prone to cell cycle-dependent death. This provides a possible mechanism underlying the increased T(CM) cell turnover in HIV infection.