Enhanced antilymphoma efficacy of CD19-redirected influenza MP1-specific CTLs by cotransfer of T cells modified to present influenza MP1

To enhance the in vivo antitumor activity of adoptively transferred, CD19-specific chimeric antigen receptor (CAR)-redirected cytototic T lymphocytes (CTLs), we studied the effect of restimulating CAR⁺ CTLs through their endogenous virus-specific T-cell antigen receptor (TcR) by the cotransfer of angineered T-cell antigen-presenting cells (T-APCs). Using influenza A matrix protein 1 (MP1) as a model antigen, we show that ex vivo-expanded CD4 ⁺ and CD8⁺ T-APCs expressing a hygromycin phosphotransferase-MP1 fusion protein (HyMP1) process and present MP1 to autologous human leukocyte antigen (HLA)-restricted, MP1-specific CD4 ⁺ and CD8⁺ CTL precursors. The MP1-specific CTLs are amenable to subsequent genetic modification to express a CD19-specific CAR, designated CD19R, and acquire HLA-unresfricted reactivity toward CD19 ⁺ leukemia and lymphoma tumor targets while maintaining HLA-restricted MP1 specificity. The restimulation of MP1 × CD19 dual-specific CTLs in vivo by the adoptive transfer of irradiated HyMP1 ⁺ T-APCs resulted in the enhanced antilymphoma potency of bispecific effector cells, as measured by elimination of the biophotonic signal of established firefly luciferase-expressing Burkitt tymphoma xenografts in nonobese diabetic/severe combined immunodeficiency (KOD/scid) animals compared with control groups restimulated by Hy⁺MP1^neg T-APCs. Engineered T-APCs are a novel and versatile antigen-delivery system for generating antigen-specific T cells in vitro and enhancing the in vivo effector functioning of CAR-redirected antitumor effector cells.