Objectives To investigate the contribution of colon and blood CD4+ T-cell subsets expressing the chemokine receptor CCR6 to HIV persistence during ART. Design Matched sigmoid biopsies and blood samples (n=13) as well as leukapheresis (n=20) were collected from chronically HIV-infected individuals receiving ART. Subsets of CD4+ T-cells with distinct differentiation/polarization profiles were identified using surface markers as follows: memory (TM, CD45RA-), central memory (TCM; CD45RA−CCR7+), effector (TEM/TM; CD45RA−CCR7−), Th17 (CCR6+CCR4+), Th1Th17 (CCR6+CXCR3+), Th1 (CCR6−CXCR3+), and Th2 (CCR6−CCR4+). Methods We used polychromatic flow cytometry for cell sorting, nested real-time PCR for HIV-DNA quantification, ELISA and flow cytometry for HIV-p24 quantification. HIV reactivation was induced by TCR-triggering in the presence/absence of all-trans retinoic acid. Results Compared to blood, the frequency of CCR6+ TM was higher in the colon. In both colon and blood compartments, CCR6+ TM were significantly enriched in HIV-DNA when compared to their CCR6− counterparts (n=13). In blood, integrated HIV-DNA levels were significantly enriched in CCR6+ versus CCR6− TCM of 4/5 individuals and CCR6+ versus CCR6− TEM of 3/5 individuals. Among blood TCM, Th17 and Th1Th17 contributed the most to the pool of cells harboring integrated HIV-DNA despite their reduced frequency compared to Th2 which were infected the least. HIV reactivation was induced by TCR triggering and/or retinoic acid exposure at higher levels in CCR6+ versus CCR6− TM, TCM, and TEM. Conclusions CCR6 is a marker for colon and blood CD4+ T-cells enriched for replication-competent HIV-DNA. Novel eradication strategies should target HIV persistence in CCR6+CD4+ T-cells from various anatomic sites.

Macrophages are heterogeneous immune cells with distinct origins, phenotypes, functions, and tissue localization. Their susceptibility to HIV-1 is subject to variations from permissiveness to resistance, owing in part to regulatory microRNAs. Here, we used RNA sequencing (RNA-seq) to examine the expression of >400 microRNAs in productively infected and bystander cells of HIV-1-exposed macrophage cultures. Two microRNAs upregulated in bystander macrophages, miR-221 and miR-222, were identified as negative regulators of CD4 expression and CD4-mediated HIV-1 entry. Both microRNAs were enhanced by tumor necrosis factor alpha (TNF-α), an inhibitor of CD4 expression. MiR-221/miR-222 inhibitors recovered HIV-1 entry in TNF-α-treated macrophages by enhancing CD4 expression and increased HIV-1 replication and spread in macrophages by countering TNF-α-enhanced miR-221/miR-222 expression in bystander cells. In line with these findings, HIV-1-resistant intestinal myeloid cells express higher levels of miR-221 than peripheral blood monocytes. Thus, miR-221/miR-222 act as effectors of the antiviral host response activated during macrophage infection that restrict HIV-1 entry.

Objective: To explore the contribution of blood and colon myeloid cells to HIV persistence during antiretroviral therapy (ART). Design: Leukapheresis were collected from HIV-infected individuals with undetectable plasma viral load during ART (HIV+ART; n=15) and viremics untreated (HIV+; n=6). Rectal sigmoid biopsies were collected from n=8 HIV+ART. Methods: Myeloid cells (total monocytes (Mo), CD16 + /CD16-Mo, CD1c + dendritic cells (DC)) and CD4 + T-cells were isolated by MACS and/or FACS from peripheral blood. Matched myeloid and CCR6 + CD4 + T-cells were isolated from blood and rectal biopsies by FACS. Levels of early (RU5 primers), late (Gag primers), and/or integrated HIV-DNA (Alu/HIV primers) were quantified by nested real-time PCR. Replication-competent HIV was amplified by co-culturing cells from HIV+ individuals with CD3/CD28-activated CD4 + T-cells from uninfected donors.

Among CD4+ T cells, T helper 17 (Th17) cells are particularly susceptible to HIV-1 infection and are depleted from mucosal sites, which causes damage to the gut barrier, resulting in a microbial translocation-induced systemic inflammation, a hallmark of disease progression. Furthermore, a proportion of latently infected Th17 cells persist long term in the gastrointestinal lymphatic tract where a low-level HIV-1 transcription is observed. This residual viremia contributes to chronic immune activation. Thus, Th17 cells are key players in HIV pathogenesis and viral persistence. It is, however, unclear why these cells are highly susceptible to HIV-1 infection. Th17 cell differentiation depends on the expression of the master transcriptional regulator RORC2, a retinoic acid-related nuclear hormone receptor that regulates specific transcriptional programs by binding to promoter/enhancer DNA. Here, we report that RORC2 is a key host cofactor for HIV replication in Th17 cells. We found that specific inhibitors that bind to the RORC2 ligand-binding domain reduced HIV replication in CD4+ T cells. The depletion of RORC2 inhibited HIV-1 infection, whereas its overexpression enhanced it. RORC2 was also found to promote HIV-1 gene expression by binding to the nuclear receptor responsive element in the HIV-1 long terminal repeats (LTR). In treated HIV-1 patients, RORC2+ CD4 T cells contained more proviral DNA than RORC2− cells. Pharmacological inhibition of RORC2 potently reduced HIV-1 outgrowth in CD4+ T cells from antiretroviral-treated patients. Altogether, these results provide an explanation as to why Th17 cells are highly susceptible to HIV-1 infection and suggest that RORC2 may be a cell-specific target for HIV-1 therapy.