CART-19 Responses in Human CD19 Transgenic Mice [inflammationv2 platform]

The clinical success of chimeric antigen receptor (CAR) T-cell therapy for CD19+ B-cell malignancies may come at the expense of acute and chronic morbidities. Some patients suffer from significant, acute toxicities and those with persistent CAR T-cells require immunoglobulin therapy due to CAR-induced B-cell aplasia. Life-threatening effects include cytokine release syndrome, the exact etiology of which is unclear. To elucidate the underlying mechanisms of CAR-induced toxicities, we developed a mouse model in which human CD19 (hCD19)-specific mouse CAR T-cells were adoptively transferred into mice whose normal B-cells express a hCD19 transgene at hemizygous levels. In contrast to homozygous mice, hemizygous mice have higher B cell frequencies, providing a greater target antigen load to drive CAR-T cell activation. Hemizygous mice given a lethal dose of hCD19 transgene-expressing lymphoma cells and treated with CAR-T cells had undetectable levels of tumor. However, recipients experienced acute B-cell aplasia, morbidities and mortality in an antigen- and dose-dependent manner. IL-6, INF-g, and inflammatory pathway transcripts were enriched in affected tissues. As in patients, antibody-mediated neutralization of IL-6 blunted toxicity. This new model will prove useful in testing strategies designed to improve CD19-specific CAR T-cell therapy by reducing acute toxicities and reversing B-cell aplasia. mRNA was extracted from colons and spleens from human CD19 transgenic mice 2 and 5 days after adoptive transfer of 3E+06 human CD19-specific CAR T-cells (or control hEGFRT-cells). mRNA for 268 unique genes were quantitated on the nanoString mouse inflammation codeset. 48 samples/codeset= 40 unique samples (8 groups x 5 biological replicates/group) + 8 technical replicates (1 for each of 8 samples).