The ability of HIV to reduce its replication and to also go into latency during chronic infection is likely one of the important mechanisms establishing its persistence in the face of the antiviral immune response that is always induced. Moreover, this aspect of HIV may be the main reason HAART does not cure infections. Accordingly, latently infected cells in patients must be eliminated to eventually effect a cure. However, studies in primary CD4 lymphocytes of the molecular mechanisms involved in regulation of HIV latency have been hindered by the scarcity of these cells in vivo. We have developed a culture system that appears to recapitulate what occurs in vivo to generate latently infected CD4 lymphocytes. In this system, normal activated CD4 lymphocytes are rescued from apoptosis that normally occurs in vitro, and these cells can be maintained viably in a resting memory state for many months. Our preliminary studies show that acutely infected, activated normal human CD4 lymphocytes that are rescued and maintained in this culture system result in 5 to 10% of the cells having latent HIV. Therefore, the purpose of this grant is to fully characterize this system to show whether it truly generates latently infected cells as found in vivo. Aim 1 will optimize the conditions for generating HIV-latently infected normal CD4 lymphocytes using this system. Aim 2 will examine whether they are truly latently infected, and determine some of their characteristics. To our knowledge we have developed the only in vitro culture system to rescue activated normal lymphocytes and to maintain memory cells long term, and this system should facilitate studies of chronic HIV infection in normal CD4 lymphocytes and the eventual delineation of molecular mechanisms of HIV latency and reactivation. [unreadable] [unreadable] [unreadable]