The immunoregulatory functions of exosome derived from mesenchymal stem cells that are genetically modified by adeno-associated virus

Objectives: To verify the effects and mechanisms of natural MSC-exosome in treating acute GVHD in mice, explore and establish a method for targeted modification of MSC-exosome, and verify the functions of the modified MSC-exosome. Methods: In different doses of MSC-exosome groups and MSC group, weight loss in acute GVHD mice was observed; then the proliferation levels of activated T cells were measured through T cell activation experiment in vitro and OVA antigen-specific T cell activation experiment in vivo. AAV2YF3 mutants carrying PD-L1 and PD-L1-ITGB1 were obtained after the construction of recombinant expression vectors and were then applied to infect human MSC to modify their exosome. The immunoregulatory functions of the modified MSC-exosome were measured with the abovementioned methods. Results: ①Mouse MSC-exosome (300 μg×3 times) and MSC (1×10(6)×3 times) effectively alleviated the weight loss in acute GVHD mice. ②Compared with IL-2, 10, 25 and 50 μg human MSC-exosome inhibited the proliferation of a