T lymphocytes engineered to express a CD16-chimeric antigen receptor redirect T-cell immune responses against immunoglobulin G-opsonized target cells.

Background aims. Chimeric antigen receptors (CARs) designed for adoptive immunotherapy need to achieve two functions:antigen recognition and triggering of the lytic machinery of reprogrammed effector cells. CytotoxicT cells have beenengineered with Fc?RIII (CD16) chimeric molecules to be redirected against malignant cells by monoclonal antibodies (mAbs).These cells have been proven to mediate granule-dependent cellular cytotoxicity, but it is not clear whether they can alsokill malignant cells by a granule-independent mechanism of cell cytotoxicity. Methods. We engineered a CD16A-CAR equippedwith the extracellular CD16A, the hinge spacer and the transmembrane region of CD8, and the ?-chain of theT-cell receptor/CD3 complex in tandem with the CD28 co-stimulatory signal transducer module. The CD16A-CAR was expressed andfunctionally tested in the MD45 cell line, a murineT-cell hybridoma with a defective granular exocytosis pathway but capableof killing target cells by a Fas ligand-mediated lysis. Results. Our results indicate that in vitro cross-linking of CD16A-CARon MD45 cells by the Fc fragment of mAb opsonized tumor cells induced interleukin-2 release and granule-independentcellular cytotoxicity. Conclusions. We conclude that strategies aimed to implement the therapeutic functions of mAbs usedin the clinic with T-dependent immune responses driven by engineered T cells expressing Fc?R-CAR can boost the antitumorefficacy of mAbs used in the clinic.