Charge-Altering Releasable Transporters Enable Specific Phenotypic Manipulation of Resting Primary Natural Killer Cells

ABSTRACT Natural killer (NK) cells are capable of rapid and robust cytotoxicity, making them excellent tools for immunotherapy. However, their recalcitrance to standard transfection techniques has limited both mechanistic studies and clinical applications. Current approaches for NK cell manipulation rely on viral transduction or methods requiring NK cell activation, which can alter NK cell function. Here, we report that non-viral Charge-Altering Releasable Transporters (CARTs) efficiently transfect primary human NK cells with mRNA without relying on NK cell activation. Compared to electroporation, CARTs transfect NK cells two orders of magnitude more efficiently, better preserve cell viability, and cause minimal reconfiguration of NK cell phenotype and function. Finally, we use CARTs to generate highly cytotoxic primary human chimeric antigen receptor NK cells, indicating potential therapeutic utility of this technique. To our knowledge, CARTs represent the first efficacious transfection technique for resting primary NK cells that preserves NK cell phenotype, and can drive new biological discoveries and clinical applications of this understudied lymphocyte subset.