Tu190 - T-cell Mediated Immune Responses Induced by anti-cd19 Chimeric Antigen Receptor (ARI-0001) in Patients with CD19 Positive B-cell Malignancies

Ariadna Bartoló-Ibars – PhD, Immunology, Hospital Clínic de Barcelona; Azucena González-Navarro – Immunology – Hospital Clínic de Barcelona; Alexandra Johansson – Tetramer Core – Benaroya Research Institute; Timothy Kountz – Tetramer Core – Benaroya Research Institute; Nela Klein-González – August Pi i Sunyer Biomedical Research Institute; berta Casanovas-Albertí – August Pi i Sunyer Biomedical Research Institute; Valentín Ortiz-Maldonado – Hematology – Hospital Clínic de Barcelona; Marta Español-Rego – Immunology – Hospital Clínic de Barcelona; Maria Castellà – Immunology – Hospital Clínic de Barcelona; Daniel Benítez – Immunology – Hospital Clínic de Barcelona; Raquel Cabezón – Immunology – Hospital Clínic de Barcelona; Jordi Esteve – Hematology – Hospital Clínic de Barcelona; Jordi Yagüe – Immunology – Hospital Clínic de Barcelona; Mariona Pascal – Immunology – Hospital Clínic de Barcelona; Álvaro Urbano-Ispizua – Immunology – Hospital Clínic de Barcelona; Susana Rives – Hematology – Hospital Sant Joan de Déu de Barcelona; Julio Delgado – Hematology – Hospital Clínic de Barcelona; William W. Kwok – Tetramer Core – Benaroya Research Institute

Abstract Text:

Background: ARI-0001 cells express a second-generation CAR that combines the anti-CD19 single-chain variable fragment (scFv) originated from A3B1, a murine monoclonal antibody, conjugated with the transmembrane and co-stimulatory domains. Although the efficacy and safety of ARI-0001 cells has been demonstrated, the relevance of the cellular immune responses induced by ARI-0001 cells has not been fully investigated.

Methods: Regarding cellular immune response, PBMCs from treated patients were stimulated with 35 HLA-II predicted peptides derived from CAR19 and CD4+ T cells were sorted through activation induced markers CD154 and CD69. After 30-35 days of expansion, CD4+ T-cell lines were screened with peptide pools and then individual peptides. Finally, it was blocked HLA-DQ, DP and DR during the individual peptide stimulation to explore which HLA present the peptide which triggers the T-cell activation.

Results: In total 43 cell lines were obtained from 5 different patients who developed human anti-murine antibodies. Eight out of 43 cell lines were reactive against CAR19 peptides after 30-35 days of expansion. In relation to CAR19 peptides, immunogenic peptides for these eight cell lines were located at scFv (VL, linker and VH) and were presented by HLA-DR.

Conclusions: These data suggest that ARI-0001 cells induce cellular immune responses. The most immunogenic domain of CAR19 is the extracellular part from murine monoclonal antibody. Even though scFv peptides induce CD4+ T cell activation, the detected immunogenic sequences do not include CDR regions. Finally, immunogenicity induced by ARI-0001 cells could be clinically important, specially before considering a second infusion.