The colocalization potential of HIV-specific CD8 ⁺ and CD4 ⁺ T-cells is mediated by integrin β7 but not CCR6 and regulated by retinoic acid

CD4 ⁺ T-cells from gut-associated lymphoid tissues (GALT) are major targets for HIV-1 infection. Recruitment of excess effector CD8 ⁺ T-cells in the proximity of target cells is critical for the control of viral replication. Here, we investigated the colocalization potential of HIV-specific CD8 ⁺ and CD4 ⁺ T-cells into the GALT and explored the role of retinoic acid (RA) in regulating this process in a cohort of HIV-infected subjects with slow disease progression. The expression of the gut-homing molecules integrin β7, CCR6, and CXCR3 was identified as a "signature" for HIV-specific but not CMV-specific CD4 ⁺ T-cells thus providing a new explanation for their enhanced permissiveness to infection in vivo. HIV-specific CD8 ⁺ T-cells also expressed high levels of integrin β7 and CXCR3; however CCR6 was detected at superior levels on HIV-specific CD4 ⁺ versus CD8 ⁺ T-cells. All trans RA (ATRA) upregulated the expression of integrin β7 but not CCR6 on HIV-specific T-cells. Together, these results suggest that HIV-specific CD8 ⁺ T-cells may colocalize in excess with CD4 ⁺ T-cells into the GALT via integrin β7 and CXCR3, but not via CCR6. Considering our previous findings that CCR6 ⁺CD4 ⁺ T-cells are major cellular targets for HIV-DNA integration in vivo, a limited ability of CD8 ⁺ T-cells to migrate in the vicinity of CCR6 ⁺CD4 ⁺ T-cells may facilitate HIV replication and dissemination at mucosal sites.