HIV type 1 persistence in CD4-/CD8- double negative T cells from patients on antiretroviral therapy

The establishment of reservoirs of latently infected cells is thought to contribute to the persistence of HIV-1 infection in the host. Studies so far have mainly focused on the long-lived reservoir of HIV-infected resting CD4(+) T cells. A discrete population of HIV-infected CD4(-)/CD8(-) double negative (DN) T cells has recently been shown to exist and may also play a role in HIV-1 persistence. DN T cells are CD3 positive, either TCR alpha beta or TCR gamma delta positive, but lack both CD4 and CD8 surface markers. We developed a novel, magnetic bead column-based cell fractionation procedure for isolating > 99% pure DN T cells. CD4(+), CD8(+), and DN T cells were purified from 23 samples of a cohort of 18 HIV-1-infected patients. Each cell fraction was analyzed for levels of total and integrated HIV-1 DNA. A correlation was observed between the presence of HIV-1 DNA in the DN T cell fraction and plasma viral load (VL). Using a micrococulture technique, we saw an initial release of virus from DN T cells of a patient with high VL. Analysis of env and nef sequence data suggested that the HIV-1 present in CD4(+) and DN T cells originated from a common infecting strain. Different from the published literature, we have demonstrated the presence of HIV-1 DNA in DN T cells only in patients who are experiencing HAART failure. While these cells may have a limited role in viral persistence in high VL patients, our results suggest DN T cells are unlikely to be a major reservoir in patients on HAART with clinically undetectable plasma viral RNA.