[Construction of specific artificial antigen-presenting cells for in vitro activation of CD19 chimeric antigen receptor T cells].

OBJECTIVE: To construct CD19-specific artificial antigen-presenting cells (aAPCs) for in vitro activation and expansion of CD19 chimeric antigen receptor (CAR)-modified T cells (CD19-CAR-T) and investigate their cytotoxic effect.

METHODS: CD19-specific aAPCs (NIH3T3-CD19/86, NIH3T3-CD19/86/137L) expressing costimulatory molecules CD86 and/or CD137L were prepared on the basis of NIH3T3 backbone cells by lentivirus-mediated gene transfer. Irradiated CD19-specific aAPCs were co-cultured with CD19-CAR-T cells to activate and amplify CD19-CAR-T cells. The growth curve of CD19-CAR-T cells was determined by trypan blue exclusion assay, and CD19CAR expression and phenotype on CD19-CAR-T cells were detected by flow cytometry. The in vitro cytotoxicity of CD19-CAR-T cells against the target cells was evaluated by bioluminescence-based cytotoxicity assay.

RESULTS: Flow cytometry showed that NIH3T3-CD19/86 and NIH3T3-CD19/86/137L expressed high levels of CD19, CD86 and/or CD137L. Both NIH3T3-CD19/86 and NIH3T3-CD19/86/137L cells could amplify CD19-CAR-T cells efficiently, but NIH3T3-CD19/86/137L cells had better amplification effect. After 14 days of co-culture with NIH3T3-CD19/86/137L cells, the number of CD19-CAR-T cells was significantly greater than that of NIH3T3-CD19/86 cells (P<0.05), and the proportion of CD19-CAR-T cells in the total T cells increased significantly (P<0.05). CD19-CAR-T cells amplified by CD19-specific aAPCs produced target-specific cytotoxicity and were able to specifically kill CD19-positive target cells. About 20% central memory T cells were present in the final products expanded by NIH3T3-CD19/86/137L.

CONCLUSION: We successfully prepared CD19-specific aAPCs that can specifically amplify functional CD19-CART cells in vitro, which facilitates the acquisition of clinical-scale high-quality CD19-CART cells.