CD28 and HIV infectious disease: To test this hypothesis, we activated CD4 T cells by anti-CD3/CD28 stimulation, followed by HIV infection in the presence of DMSO or ATM inhibitor (ATMi, 10 μM KU60019) for 3, 5, and 7 days, and then measured the telomere length, and hTERT, pAKT, and pATM expressions.