BACH2 effector-to-memory switch promotes HIV persistence and CAR-T efficacy

PURPOSE OF REVIEW: HIV integration into BACH2 is significantly enriched in people living with HIV (PLWH), but not in vitro . Specifically, HIV integration sites are enriched in the same orientation and upstream of BACH2 translation. HIV drives high levels of BACH2 expression through HIV-to- BACH2 splicing. BACH2, a transcription repressor that competes with AP-1 binding, is an effector-to-memory switch that restrains effector function, drives T cell stemness, and promotes long-lived memory. RECENT FINDINGS: Retroviral infection mouse model containing retroviral splice sites recapitulated the orientation- and site-dependent enrichment of integration into BACH2 , revealing in-vivo selection pressure favoring BACH2 expression. Two back-to-back BACH2 studies revealed that BACH2 promotes HIV persistence. High BACH2 activity in the gut tissue resident memory CD4 + T cells (T RM ) drives long-lived persistence of HIV-infected cells in the gut, while high BACH2 activity in the gut HIV-specific CD8 + T RM restrains effector function. Higher BACH2 activity in tissues than blood drives distinct mechanisms of HIV persistence in the gut versus blood. Finally, three back-to-back BACH2 studies revealed how druggable finetuning of BACH2 promotes chimeric antigen receptor (CAR)-T cell persistence and efficacy. SUMMARY: BACH2 promotes the persistence of both HIV and CAR-T cells by driving T cell stemness and long-lived memory.