Structural basis for CD8+ T cell recognition of the charge-reversed neoantigen UTP20D2661H.

Adoptive T cell therapy (ACT) eliminates tumors by infusing tumor reactive T cells. Neoantigens from somatic mutations are ideal targets due to their absence in normal tissues. How charge-reversing mutations drive neoantigen immunogenicity remains unclear. Here, we determined the wild-type and mutant UTP20-HLA-A2 structures and found them nearly identical except at the mutation site (Asp to His). The TCR-pHLA structure revealed selective recognition through specific interactions between CDR loops and the mutation site. Rosetta calculations showed that His provides favorable interactions absent in the wild-type. TCR engagement also induced a flip of the P6 side chain, reshaping the interface. These findings provide a structural basis for charge-reversed mutation-driven T cell responses and inform neoantigen-based ACT development.