Background
Cell culture conditions during manufacturing can impact the clinical efficacy of chimeric antigen receptor (CAR) T cell products. Production
Conclusions
Our data indicate that CD4+ cell help during cell culture maintains robust CD8+ CAR T cell function, with implications for clinical cell manufacturing.
Methods
We generated CAR T cells either as separate CD4+ and CD8+ cells, or as combined cultures mixed in defined CD4:CD8 ratios at culture initiation. We assessed CAR T cell expansion, phenotype, function, gene expression, and in vivo activity of CAR T cells and compared these between separately expanded or mixed CAR T cell cultures.
Results
We found that the coculture of CD8+ CAR T cells with CD4+ cells markedly improves CD8+ cell expansion, and further discovered that CD8+ cells cultured in isolation exhibit a hypofunctional phenotype and transcriptional signature compared with those in mixed cultures with CD4+ cells. Cocultured CAR T cells also confer superior antitumor activity in vivo compared with separately expanded cells. The positive impact of CD4+ cells on CD8+ cells was mediated through both cytokines and direct cell contact, including CD40L-CD40 and CD70-CD27 interactions. Conclusions: Our data indicate that CD4+ cell help during cell culture maintains robust CD8+ CAR T cell function, with implications for clinical cell manufacturing.