Human MHC Class I-restricted high avidity CD4⁺ T cells generated by co-transfer of TCR and CD8 mediate efficient tumor rejection in vivo

In this study, we generated human MHC Class I-restricted CD4⁺ T cells specific for Epstein-Barr virus (EBV) and cytomegalovirus (CMV), two herpesviridae associated with lymphoma, nasopharyngeal carcinoma and medulloblastoma, respectively. Retroviral transfer of virus-specific, HLA-A2-restricted TCR-coding genes generated CD4⁺ T cells that recognized HLA-A2/peptide multimers and produced cytokines when stimulated with MHC Class II-deficient cells presenting the relevant viral peptides in the context of HLA-A2. Peptide titration revealed that CD4⁺ T cells had a 10-fold lower avidity than CD8⁺ T cells expressing the same TCR. The impaired avidity of CD4⁺ T cells was corrected by simultaneously transferring TCR- and CD8-coding genes. The CD8 co-receptor did not alter the cytokine signature of CD4⁺ T cells, which remained distinct from that of CD8⁺ T cells. Using the xenogeneic NOD/SCID mouse model, we demonstrated that human CD4⁺ T cells expressing a specific TCR and CD8 can confer efficient protection against the growth of tumors expressing the EBV or CMV antigens recognized by the TCR. In summary, we describe a robust approach for generating therapeutic CD4⁺ T cells capable of providing MHC Class I-restricted immunity against MHC Class II-negative tumors in vivo.