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.

There is intense interest in developing curative interventions for HIV. How such a cure will be quantified and defined is not known. We applied a series of measurements of HIV persistence to the study of an HIV-infected adult who has exhibited evidence of cure after allogeneic hematopoietic stem cell transplant from a homozygous CCR5Δ32 donor. Samples from blood, spinal fluid, lymph node, and gut were analyzed in multiple laboratories using different approaches. No HIV DNA or RNA was detected in peripheral blood mononuclear cells (PBMC), spinal fluid, lymph node, or terminal ileum, and no replication-competent virus could be cultured from PBMCs. However, HIV RNA was detected in plasma (2 laboratories) and HIV DNA was detected in the rectum (1 laboratory) at levels considerably lower than those expected in ART-suppressed patients. It was not possible to obtain sequence data from plasma or gut, while an X4 sequence from PBMC did not match the pre-transplant sequence. HIV antibody levels were readily detectable but declined over time; T cell responses were largely absent. The occasional, low-level PCR signals raise the possibility that some HIV nucleic acid might persist, although they could also be false positives. Since HIV levels in well-treated individuals are near the limits of detection of current assays, more sensitive assays need to be developed and validated. The absence of recrudescent HIV replication and waning HIV-specific immune responses five years after withdrawal of treatment provide proof of a clinical cure.

Even with optimal antiretroviral therapy, human immunodeficiency virus (HIV) persists in plasma, blood cells, and tissues. To develop new therapies, it is essential to know what cell types harbor residual HIV. We measured levels of HIV DNA, RNA, and RNA/DNA ratios in sorted subsets of CD4+ T cells (CCR7+, transitional memory, and effector memory) and non-CD4+ T leukocytes from blood, ileum, and rectum of 8 ART-suppressed HIV-positive subjects. Levels of HIV DNA/million cells in CCR7+ and effector memory cells were higher in the ileum than blood. When normalized by cell frequencies, most HIV DNA and RNA in the blood were found in CCR7+ cells, whereas in both gut sites, most HIV DNA and RNA were found in effector memory cells. HIV DNA and RNA were observed in non-CD4+ T leukocytes at low levels, particularly in gut tissues. Compared to the blood, the ileum had higher levels of HIV DNA and RNA in both CD4+ T cells and non-CD4+ T leukocytes, whereas the rectum had higher HIV DNA levels in both cell types but lower RNA levels in CD4+ T cells. Future studies should determine whether different mechanisms allow HIV to persist in these distinct reservoirs, and the degree to which different therapies can affect each reservoir.