This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We examined rhesus macaques of Chinese origin (Ch Rh) infected with SIVmac to examine the ability of the intestine to serve as a reservoir in progressors and LTNP. Although most Ch Rh infected with SIVmac develop AIDS, we have shown that approximately 30% control infection and become LTNP, even though virus can consistently be isolated from tissues. By using this SIV macaque model, we quantified and compared viral RNA and DNA in the small and large intestine of LTNP. We found that in chronically infected LTNP, colon had consistently higher levels of viral replication than jejunum. Colon also had significantly higher percentages of viral target cells (memory CD4+CCR5+ T cells) than jejunum. These target cells in colon were positively correlated with those in the jejunum. Moreover, colon had significantly higher percentages of proliferating memory CD4+ T cells than the jejunum, but markers of cell activation were similar in both compartments. The data indicate the large intestine is a major reservoir for SIV in LTNP, which may be the result of persistent, latently-infected cells, and higher turnover of na[unreadable]ve and central memory CD4+ T cells in this major immunologic compartment.