UC San Diego

Highly active antiretroviral therapy (HAART) in individuals infected with HIV-1 often lowers plasma viremia to below detection limits. However, cessation of therapy in such individuals results in rebound of virus replication, indicating that HIV-infected cells persist. Resting, memory CD4 T cells in the blood and lymph nodes comprise the major reservoir for persistent HIV infection. To devise new efficient strategies targeted toward the eradication of the latently infected HIV reservoir, a better understanding of the molecular and cellular basis for viral latency is needed. Dr. Spina's research group has developed a unique in vitro T cell model to study HIV latency. In my thesis project, I have used and modified this cell model to investigate: 1) the cellular proliferation and activation requirements for the development of latently infected CD4 cells, and 2) the transcriptional activity of the HIV provirus in a nonproductive, persistent infection. Results from the first research phase demonstrated that HIV infection immediately prior to T cell stimulation resulted in production of the greatest number of latently infected cells. Infected cells that did not divide, or divided only a few times, following stimulation went on to form the latently infected cell pool. The vast majority of acutely infected, activated CD4 cells were not able to survive multiple rounds of cell division in combination with the cytopathic effects of HIV. Rather, the subset of CD4 cells that exhibited minimal activation, in the presence of fully-activated and productively infected T cells, survived with latent HIV infection. In the second phase of research, a sensitive qRT-PCR assay was used to examine the transcriptional activity of the HIV provirus in resting, infected CD4 cells. Multiple different species of HIV mRNA were found, with unspliced gag transcripts being the most abundant followed by singly-spliced env, total multiply-spliced, nef, and tat species. Detection of viral RNA transcription in latently infected T cells from our in vitro model has raised the possibility that HIV latency is not maintained by a simple passive mechanism, but may involve active interactions between viral products and cell processes that influence viral latency and reactivation