Poncette et al. found that NY-ESO-1-specific TCRs isolated from ABabDR4 mice – which express human HLA-DR-4-restricted TCRs, but lack tolerance-inducing human antigens – had higher functional avidity and recognition of NY-ESO-1-positive cell lines than NY-ESO-1-specific TCRs derived in vitro from human CD4+ T cells. In a mouse model of adoptive transfer in which HLA-DR-4 was expressed on host stromal cells but not NY-ESO-1+ tumor cells, the combination of CD4+ T cells with ABabDR4-derived NY-ESO-1 TCRs and NY-ESO-1-specific CD8+ T cells induced superior tumor regression, though it was short-term due to antigen loss.
Adoptive transfer of T cell receptor-engineered (TCR-engineered) T cells is a promising approach in cancer therapy but needs improvement for more effective treatment of solid tumors. While most clinical approaches have focused on CD8+ T cells, the importance of CD4+ T cells in mediating tumor regression has become apparent. Regarding shared (self) tumor antigens, it is unclear whether the human CD4+ T cell repertoire has been shaped by tolerance mechanisms and lacks highly functional TCRs suitable for therapy. Here, TCRs against the tumor-associated antigen NY-ESO-1 were isolated either from human CD4+ T cells or from mice that express a diverse human TCR repertoire with HLA-DRA/DRB1*0401 restriction and are NY-ESO-1 negative. NY-ESO-1-reactive TCRs from the mice showed superior recognition of tumor cells and higher functional activity compared with TCRs from humans. We identified a candidate TCR, TCR-3598_2, which was expressed in CD4+ T cells and caused tumor regression in combination with NY-ESO-1-redirected CD8+ T cells in a mouse model of adoptive T cell therapy. These data suggest that MHC II-restricted TCRs against NY-ESO-1 from a nontolerant nonhuman host are of optimal affinity and that the combined use of MHC I- and II-restricted TCRs against NY-ESO-1 can make adoptive T cell therapy more effective.