CD19 Chimeric Antigen Receptor-Exosome Targets CD19 Positive B-lineage Acute Lymphocytic Leukemia and Induces Cytotoxicity.

CAR-T cell therapy is not without some clinical adverse effects, namely cytokine storms, due to a massive release of cytokines when CAR-T cells multiply in the body. Our goal was to develop exosomes expressing CD19 CAR to treat CD19-positive B-cell malignancies, instead of using whole CD19 CAR-T cells, thereby reducing the clinical risk of uncontrolled cytokine storms. Exosomes are extracellular nanovesicles (30-150 nm), composed of lipids, proteins, and nucleic acids, that carry the fingerprint of their parent cells. Exosomes are a preferred delivery system in nano-immunotherapy. Here, HEK293T parent cells were transduced with CD19 CAR plasmids and cellular CD19 CAR expression was confirmed. Exosomes (Exo-CD19 CAR) were isolated from the conditioned medium of non-transduced (WT) and CD19 CAR plasmid transduced HEK293T cells. Consequently, CD19 B-lineage leukemia cell lines were co-cultured with Exo-CD19 CAR and cell death was measured. Our data show that Exo-CD19 CAR treatment induced cytotoxicity and elevated pro-apoptotic genes in CD19-positive leukemia B-cells without inducing cell death in CD19-negative cells. Overall, the novel CD19 CAR exosomes target the CD19 surface antigens of leukemic B-cells and can induce contact-dependent cytotoxicity.