Activation-gated, T cell-restricted silencing of Dapk1 enhances Bacille Calmette-Guérin-elicited protective CD4+ memory.

Durable CD4+ T cell memory is essential against mycobacterial infection, yet activation-induced cell death (AICD) limits the survival of activated clones after BCG vaccination. The upstream, cell-intrinsic brakes that govern this bottleneck remain incompletely defined. Combining transcriptomics, loss-of-function tests, and in vivo engineering, we identify Dapk1 as a pro-apoptotic regulator that is downregulated in memory CD4+ T cells and promotes activation-induced death in T cell models. We develop an activation-gated AAV platform in which an NFAT-IL-2 promoter drives Cre to flip a FLEXed U6-shRNA cassette, and package them into a single AIO vector. This design confines Dapk1 silencing to antigen-experienced T cells, preferentially within the CD4+CD44hi compartment. In BCG-vaccinated mice, transient activation-linked Dapk1 inhibition expands CD4+ TCM cells, enhances IL-2 and Th1-skewed recall responses, lowers pulmonary, and splenic bacterial burdens after M.tb challenge. These findings highlight a strategy to selectively modulate intrinsic death pathways during immune priming for strengthening vaccine-elicited T cell memory.