ABSTRACTTreatment of human immunodeficiency virus (HIV) infection with antiretroviral therapy (ART) has significantly improved prognosis. Unfortunately, interruption of ART almost invariably results in viral rebound, attributed to a pool of long-lived, latently infected cells. Based on their longevity and proliferative potential, CD4+T memory stem cells (TSCM) have been proposed as an important site of HIV persistence. In a previous study, we found that in simian immunodeficiency virus (SIV)-infected rhesus macaques (RM), CD4+TSCMare preserved in number but show (i) a decrease in the frequency of CCR5+cells, (ii) an expansion of the fraction of proliferating Ki-67+cells, and (iii) high levels of SIV DNA. To understand the impact of ART on both CD4+TSCMhomeostasis and virus persistence, we conducted a longitudinal analysis of these cells in the blood and lymph nodes of 25 SIV-infected RM. We found that ART induced a significant restoration of CD4+CCR5+TSCMboth in blood and in lymph nodes and a reduction in the fraction of proliferating CD4+Ki-67+TSCMin blood (but not lymph nodes). Importantly, we found that the level of SIV DNA in CD4+transitional memory (TTM) and effector memory (TEM) T cells declined ∼100-fold after ART in both blood and lymph nodes, while the level of SIV DNA in CD4+TSCMand central memory T cells (TCM-) did not significantly change. These data suggest that ART is effective at partially restoring CD4+TSCMhomeostasis, and the observed stable level of virus in TSCMsupports the hypothesis that these cells are a critical contributor to SIV persistence.IMPORTANCEUnderstanding the roles of various CD4+T cell memory subsets in immune homeostasis and HIV/SIV persistence during antiretroviral therapy (ART) is critical to effectively treat and cure HIV infection. T memory stem cells (TSCM) are a unique memory T cell subset with enhanced self-renewal capacity and the ability to differentiate into other memory T cell subsets, such as central and transitional memory T cells (TCMand TTM, respectively). CD4+TSCMare disrupted but not depleted during pathogenic SIV infection. We find that ART is partially effective at restoring CD4+TSCMhomeostasis and that SIV DNA harbored within this subset contracts more slowly than virus harbored in shorter-lived subsets, such as TTMand effector memory (TEM). Because of their ability to persist long-term in an individual, understanding the dynamics of virally infected CD4+TSCMduring suppressive ART is important for future therapeutic interventions aimed at modulating immune activation and purging the HIV reservoir.
Ex Vivo Phenotype and Frequency of Influenza Virus-Specific CD4 Memory T Cells
