Abstract Body

Background: HIV/SIV infection of GI tract-resident CD4+ memory T-cells during acute infection leads to rapid loss of these cells with subsequent damage to the epithelial layer and microbial translocation. Immune activation, in part, caused by microbial products leads to progression to AIDS. Although microbial translocation has been demonstrated in SIV infected non-human primates, the identity of translocating bacteria has not been determined. In this study we examine the community makeup of bacteria both within the GI tract and distal tissues of healthy, experimentally SIV-infected, and SIV-infected and probiotic-treated Asian macaques. Methodology: Bacterial DNA was isolated from colon, mesenteric lymph nodes (MLN) and liver taken from sacrificed Asian macaques. The identity of bacteria populating these was determined by 454 pyro-sequencing of 16s ribosomal DNA or quantitative PCR directed against particular phyla of 16s DNA. DNA and RNA were isolated from the stool of SIV-infected Asian macaques both before and during treatment with a HAART or HAART with probiotic (VSL#3). RNA was reverse transcribed using 16s specific primers and levels of particular phyla of 16S rRNA or DNA were used to determine stool associated microbial structure using 454 pyro-sequencing or qPCR. Results: Analysis of bacterial DNA found in the tissues of infected animals revealed a preference for members of the phylum Proteobacteria. No bacterial dysbiosis was observed in the colon itself during infection, suggesting that the increased prevalence of Proteobacteria in the tissues was due to preferential translocation of these particular bacterial species. Indeed, 454 analysis revealed a further preference for specific members of this phylum (with motile species frequently observed). Analysis of stool during infection and treatment of animals revealed changes in the metabolic activity of bacteria within the GI tract. The biggest change being observed after the administration of anti-retroviral medication with increased metabolic activity of Proteobacteria. Probiotic treatment seemed to decrease the metabolic activity of these proteobacteria. Conclusions: Proteobacteria preferentially translocate from the GI tract during SIV infection of Asian macaques. Translocating species involved motile flagellated species, some of which can cause disease. suggesting these potentially pathogenic species cause systemic immune activation. Interestingly, metabolic activity of proteobacteria is highest during acute infection (when translocation begins) and increases drastically during HAART treatment. Probiotic administration may potentially counteract this and ameliorate systemic immune activation which could improve the prognosis of ARV-treated, HIVinfected individuals.