There is limited knowledge on the identity of primary CD4+ T cell subsets selectively targeted by HIV-1 in vivo. In this study, we established a link between HIV permissiveness, phenotype/homing potential, and lineage commitment in primary CD4+ T cells. CCR4+CCR6+, CCR4+CCR6−, CXCR3+CCR6+, and CXCR3+CCR6− T cells expressed cytokines and transcription factors specific for Th17, Th2, Th1Th17, and Th1 lineages, respectively. CCR4+CCR6+ and CXCR3+CCR6+ T cells expressed the HIV coreceptors CCR5 and CXCR4 and were permissive to R5 and X4 HIV replication. CCR4+CCR6− T cells expressed CXCR4 but not CCR5 and were permissive to X4 HIV only. CXCR3+CCR6− T cells expressed CCR5 and CXCR4 but were relatively resistant to R5 and X4 HIV in vitro. Total CCR6+ T cells compared with CCR6− T cells harbored higher levels of integrated HIV DNA in treatment-naive HIV-infected subjects. The frequency of total CCR6+ T cells and those of CCR4+CCR6+ and CXCR3+CCR6+ T cells were diminished in chronically infected HIV-positive subjects, despite viral-suppressive therapy. A high-throughput analysis of cytokine profiles identified CXCR3+CCR6+ T cells as a major source of TNF-α and CCL20 and demonstrated a decreased TNF-α/IL-10 ratio in CXCR3+CCR6− T cells. Finally, CCR4+CCR6+ and CXCR3+CCR6+ T cells exhibited gut- and lymph node-homing potential. Thus, we identified CCR4+CCR6+ and CXCR3+CCR6+ T cells as highly permissive to HIV replication, with potential to infiltrate and recruit more CCR6+ T cells into anatomic sites of viral replication. It is necessary that new therapeutic strategies against HIV interfere with viral replication/persistence in discrete CCR6+ T cell subsets.

Background: Human peripheral blood monocytes (Mo) consist of subsets distinguished by expression of CD16 (FCγRIII) and chemokine receptors. Classical CD16 -Mo express CCR2 and migrate in response to CCL2, while a minor CD16 + Mo subset expresses CD16 and CX3CR1 and migrates into tissues expressing CX3CL1. CD16 + Mo produce pro-inflammatory cytokines and are expanded in certain inflammatory conditions including sepsis and HIV infection.

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.

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