HIV-1-Specific CAR-T Cells Fail to Recognize and Eliminate the Follicular Dendritic Cell (FDC) HIV Reservoir In Vitro .

The major obstacle to a cure for HIV infection is persistence of replication competent viral reservoirs during antiretroviral therapy. HIV-specific chimeric antigen receptor (CAR) T cells have been developed to target latently infected CD4+ T cells that express virus either spontaneously or after intentional latency reversal. Whether HIV-specific CAR-T cells can recognize and eliminate the follicular dendritic cell (FDC) reservoir of HIV bound immune complexes (ICs) is unknown. We created HIV-specific CAR-T cells using human PBMC and a CAR construct that enables expression of CD4 (domains 1 and 2) and the carbohydrate recognition domain of mannose binding lectin (MBL) to target native HIV Env (CD4-MBL CAR). We assessed CAR-T cell cytoxicity using a carboxyfluorescein succinimidyl ester (CFSE) release assay, and evaluated CAR-T cell activation through IFN-γ production, and CD107a membrane accumulation by flow cytometry. CD4-MBL CAR-T cells displayed potent lytic and functional responses to Env-expressing cell lines and HIV-infected CD4+ T cells but were ineffective at targeting FDC bearing HIV-IC. CD4-MBL CAR-T cells were unresponsive to cell-free HIV or concentrated, immobilized HIV-IC in cell-free experiments. Blocking intercellular adhesion molecule-1 (ICAM-1) inhibited the cytolytic response of CD4-MBL CAR-T cells to Env-expressing cell lines, and HIV-infected CD4+ T cells, suggesting that factors such as adhesion molecules, are necessary for stabilization of the CAR-Env interaction to elicit a cytotoxic response. Thus, CD4-MBL CAR-T cells are unable to eliminate the FDC-associated HIV reservoir, and alternative strategies to eradicate this reservoir must be sought.Efforts to cure HIV infection have focused primarily on elimination of latently infected CD4+ T cells. Few studies have addressed the unique reservoir of infectious HIV that exists on follicular dendritic cells (FDC), persists in vivo during antiretroviral therapy, and likely contributes to viral rebound upon cessation of antiretroviral therapy. We assessed the efficacy of a novel HIV-specific chimeric antigen receptor (CAR) T cell to target both HIV infected CD4+ T cells and the FDC reservoir in vitro. Although CAR-T cells eliminated CD4+ T cells that express HIV, they did not respond to or eliminate FDC bound to HIV. These findings reveal a fundamental limitation to CAR-T cell therapy to eradicate HIV.