Modulating CD226 and PD-(L)1 pathways improves CMV-specific CD8＋T cell responses in the absence of IL-2.

Glioblastoma (GBM) frequently expresses cytomegalovirus (CMV) antigens, making CMV-specific CD8＋T cells attractive candidates for adoptive immunotherapy due to their longevity and inherent tumor reactivity. However, these T cells encounter significant immunosuppressive challenges within the GBM microenvironment, including cytokine scarcity and checkpointmediated inhibition, which limit their proliferation and function. Here, we assessed strategies to overcome these limitations by modulating immune checkpoint pathways. Antigen stimulation combined with IL-2 robustly expanded high-avidity (tetramer-high) CMV-specific T cells with significant enrichment of CD62L＋ central memory (TCM) cells. In contrast, antigen stimulation alone modestly expanded tetramer-high cells with limited TCM enrichment. PD-L1 blockade in the absence of IL-2 favored expansion of tetramer-high CMV-specific CD8＋T cells, preserved CD62L expression, and enhanced CD226 expression. Furthermore, combining anti-PD-L1 blockade with an anti-CD226 agonist markedly enhanced proliferation, IFN-γ production, and TCM enrichment in both tetramer-high and tetramer-low populations, reaching levels comparable to IL-2-supported conditions. Together, these findings highlight that simultaneous modulation of PD-L1 and CD226 pathways can restore CMV-specific T cell function, offering a promising strategy to boost TCR-T efficacy in cytokine-deprived environments.