In-vitro Expansion and Transduction of Primary Natural Killer Cells Using Feeder Cells Co-expressing Co-stimulatory Receptors and Membrane-bound IL-21

Natural Killer (NK) cells are an important population of the immune system and NK cell based therapy shown great potential in the treatment of cancers. However, to apply NK cells clinically, producing a large number of cells with high cytotoxicity remains a challenge. Current strategies focus on employing different irradiated feeder cells to stimulate NK expansion, maturation, and cytotoxicity. Current strategies focus on employing different irradiated feeder cells to stimulate NK expansion, maturation, and cytotoxicity. While co-stimulatory signals play critical roles in promoting NK cell proliferation and activating their functions, the exploitation of these signals for expanding NK cells has not been fully explored. Therefore, we generated different feeder cells expressing the co-stimulatory molecule CD80 with 4-1BBL or membrane-bound IL-21 to identify the optimal engineered feeder cells for expanding NK cells from umbilical cord blood. We then evaluated the transduction efficacy of a chimeric antigen receptor (CAR) construct into expanded NK cells using various lentiviral vectors. Our results showed that CD80 in combination with membrane-bound IL-21 provides optimal expansion of NK cells from cord blood. These expanded NK cells display strong cytotoxicity to the target cells upon transduction with baboon endogenous virus (BaEV) envelope glycoprotein pseudotyped vector expressing a specific CAR..