Microbial translocation contributes to persistent inflammation in both treated and untreated HIV infection. Although translocation is due in part to a disintegration of the intestinal epithelial barrier, there is a bias towards the translocation of Proteobacteria. In murine models, epithelial-derived microvesicles (MVs) have been shown to influence bacterial gene expression and growth. We hypothesize that intestinal epithelial MVs biologically differ after HIV infection, which may contribute to biased translocation.
We isolated fecal MVs from 12 healthy and 12 SIV-infected rhesus macaques (RM, Macaca mulatta) and co-cultured these MVs with isolates of translocated bacterial species. Viable bacteria that had translocated were isolated from mesenteric lymph nodes, livers, and spleens obtained from end-stage, SIV-infected RM, cultured under aerobic and anaerobic conditions, and identified by MALDI-TOF or 16S rDNA sequencing. Bacterial growth was kinetically assayed by spectrophotometer. MV miRNA profiles were assessed by human miRNA Array cards and qRT-PCR. AMPs alpha defensin 1, beta defensin (bDEF) 1, bDEF2, bDEF4, Lysozyme C, PLA2G2a, and Reg3g were assayed by ELISA.
Utilizing a non-human primate model of AIDS, we observed that MV miRNA profiles differ significantly after SIV infection. Ninety-three of 100 differentially expressed miRNAs displayed upregulated expression, with miR-425 and -484 showing significant upregulation in MVs derived from SIV-infected RM. Among AMPs, bDEF1 showed a significant downregulation among MVs from SIV-infected RMs. Several bacterial species showed dose-dependent growth sensitivity upon MV co-culture. Notably, Lactobacillus salivarius showed significantly accelerated growth when co-cultured with MVs derived from SIV-infected animals while Klebsiella pneumoniae displayed stunted growth.
Fecal MVs can differentially influence the growth of bacterial isolates known to translocate in SIV infection. This effect may be attributable to a shift in MV miRNA content and/or to a shift in AMP content. The identification of the precise mechanisms by which fecal MVs differentially regulate the behavior of translocating bacteria will inform the development of therapeutics aimed at impeding microbial translocation.