HIV-1 infection disrupts the intestinal immune system, leading to microbial translocation and systemic immune activation. We investigated the impact of HIV-1 infection on the intestinal microbiome and its association with mucosal T cell and dendritic cell (DC) frequency and activation, as well as with levels of systemic T cell activation, inflammation and microbial translocation. Bacterial 16S ribosomal DNA sequencing was performed on colon biopsies and fecal samples from subjects with chronic, untreated HIV-1 infection and uninfected control subjects. Colon biopsies of HIV-1 infected subjects had increased abundances of Proteobacteria and decreased abundances of Firmicutes compared to uninfected donors. Furthermore at the genus level, a significant increase in Prevotella and decrease in Bacteroides was observed in HIV-1 infected subjects, indicating a disruption in the Bacteroidetes bacterial community structure. This HIV-1-associated increase in Prevotella abundance was associated with increased numbers of activated colonic T cells and myeloid DCs. Principal coordinates analysis demonstrated an HIV-1-related change in the microbiome that was associated with increased mucosal cellular immune activation, microbial translocation and blood T cell activation. These observations suggest that an important relationship exists between altered mucosal bacterial communities and intestinal inflammation during chronic HIV-1 infection.

Deoxyribonucleic acid (DNA) of the human immunodeficiency virus (HIV) provides the most sensitive measurement of residual infection in patients on effective combination antiretroviral therapy (cART). Droplet digital PCR (ddPCR) has recently been shown to provide highly accurate quantification of DNA copy number, but its application to quantification of HIV DNA, or other equally rare targets, has not been reported. This paper demonstrates and analyzes the application of ddPCR to measure the frequency of total HIV DNA (pol copies per million cells), and episomal 2-LTR (long terminal repeat) circles in cells isolated from infected patients. Analysis of over 300 clinical samples, including over 150 clinical samples assayed in triplicate by ddPCR and by real-time PCR (qPCR), demonstrates a significant increase in precision, with an average 5-fold decrease in the coefficient of variation of pol copy numbers and a >20-fold accuracy improvement for 2-LTR circles. Additional benefits of the ddPCR assay over qPCR include absolute quantification without reliance on an external standard and relative insensitivity to mismatches in primer and probe sequences. These features make digital PCR an attractive alternative for measurement of HIV DNA in clinical specimens. The improved sensitivity and precision of measurement of these rare events should facilitate measurements to characterize the latent HIV reservoir and interventions to eradicate it.

Background The gut is a major reservoir for HIV in patients receiving antiretroviral therapy (ART). We hypothesized that distinct immune environments within the gut may support varying levels of HIV. Methods In 8 HIV-1+ adults on ART with CD4>200 and plasma VL<40, levels of HIV and T-cell activation were measured in blood and endoscopic biopsies from the duodenum, ileum, right colon, and rectum. Results HIV DNA and RNA per CD4+T-cell were higher in all four gut sites compared to blood. HIV DNA increased from the duodenum to the rectum, while the median HIV RNA peaked in the ileum. HIV DNA correlated positively with T-cell activation in the PBMC but negatively with T-cell activation in the gut. Multiply-spliced RNA was infrequently detected in gut, and unspliced RNA/DNA ratios were lower in the colon and rectum relative to PBMC, reflecting paradoxically low HIV transcription given the higher T-cell activation in the gut. Conclusions HIV DNA and RNA are both concentrated in the gut, but the inverse relationship between HIV DNA and T-cell activation in the gut and the paradoxically low levels of HIV expression in the large bowel suggest that different processes drive HIV persistence in the blood and gut.