An in vitro system to model the establishment and reactivation of HIV-1 latency

HIV-1 establishes latency primarily by infecting activated CD4 T cells that later return to quiescence as memory cells. Latency allows HIV-1 to evade immune responses and to persist during antiretroviral therapy, which represents an important problem in clinical practice. The lack of a valid cellular model to study HIV-1 latency has hindered advances in the understanding of its biology. In this study, we attempted to model HIV-1 latency using human primary CD4 T cells infected in vitro with HIV-1 after activation with Ag-loaded dendritic cells and then brought back to quiescence through a resting phase in the presence of IL-7. During the resting phase, expression of cellular activation markers disappeared and cell proliferation and viral replication ceased, but resumed following restimulation of rested cells with Ag or mAbs directed to CD3/CD28. In addition, higher cell death rates were observed in HIV-1-infected than uninfected cultures during secondary but not primary stimulation. Thus, this system may allow us to study the biology of HIV-1 latency, as well as the mechanisms of CD4 T cell death following HIV-1 reactivation. The Journal of Immunology, 2008, 181: 7713–7720. A lthough highly active antiretroviral therapy (HAART)2suppresses viral replication to undetectable levels,HIV-1 continuously replicates throughout the course of the infection (1). However, HIV-1 also establishes a status of nonproductive infection known as viral latency. Harper et al. (2) reported that cells harboring the provirus in clinical samples were found at frequency considerably higher than cells express