A novel high-affinity scFv antibody targeting the histone 3.3 K27M25-35 neoepitope in the context of HLA-A*02:01 recognized peptide-pulsed APCs, but not H3.3K27M-mutated cell lines derived from patients with diffuse intrinsic pontine glioma (DIPG). Wang and Pandey et al. found that even though H3.3 is undergoing proteasomal degradation, and non-mutated H3.3-derived peptides are presented on the cell surface, the H3.3K27M25-35 neoepitope in not endogenously processed and presented in HLA-A*02:01+ DIPG cell lines. Immunopeptidomics identified a novel potential HLA-A*03:01-restricted H3.3K27M26-36 neoepitope that is processed and presented.
Contributed by Ute Burkhardt
ABSTRACT: Diffuse midline glioma (DMG) is a childhood brain tumor with an extremely poor prognosis. Chimeric antigen receptor (CAR) T cell therapy has recently demonstrated some success in DMG, but there may a need to target multiple tumor-specific targets to avoid antigen escape. We developed a second-generation CAR targeting an HLA-A∗02:01 restricted histone 3K27M epitope in DMG, the target of previous peptide vaccination and T cell receptor-mimics. These CAR T cells demonstrated specific, titratable, binding to cells pulsed with the H3.3K27M peptide. However, we were unable to observe scFv binding, CAR T cell activation, or cytotoxic function against H3.3K27M+ patient-derived models. Despite using sensitive immunopeptidomics, we could not detect the H3.3K27M26-35-HLA-A∗02:01 peptide on these patient-derived models. Interestingly, other non-mutated peptides from DMG were detected bound to HLA-A∗02:01 and other class I molecules, including a novel HLA-A3-restricted peptide encompassing the K27M mutation and overlapping with the H3 K27M26-35-HLA-A∗02:01 peptide. These results suggest that targeting the H3 K27M26-35 mutation in context of HLA-A∗02:01 may not be a feasible immunotherapy strategy because of its lack of presentation. These findings should inform future investigations and clinical trials in DMG.
Author Info: (1) The Walter and Eliza Hall Institute of Medical Research, Immunology Division, Parkville, VIC 3052, Australia. Murdoch Children's Research Institute, Parkville, VIC 3052, Austra
Author Info: (1) The Walter and Eliza Hall Institute of Medical Research, Immunology Division, Parkville, VIC 3052, Australia. Murdoch Children's Research Institute, Parkville, VIC 3052, Australia. The University of Melbourne, Department of Medical Biology, Parkville, VIC 3052, Australia. (2) Department of Biochemistry and Molecular Biology and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia. (3) The Walter and Eliza Hall Institute of Medical Research, Immunology Division, Parkville, VIC 3052, Australia. (4) The Walter and Eliza Hall Institute of Medical Research, Immunology Division, Parkville, VIC 3052, Australia. The University of Melbourne, Department of Medical Biology, Parkville, VIC 3052, Australia. (5) Department of Biochemistry and Molecular Biology and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia. (6) Myrio Therapeutics, 6-16 Joseph St, Blackburn North, Melbourne, VIC 3130, Australia. (7) Department of Biochemistry and Molecular Biology and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia. (8) The Walter and Eliza Hall Institute of Medical Research, Immunology Division, Parkville, VIC 3052, Australia. (9) Department of Biochemistry and Molecular Biology and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia. (10) The Walter and Eliza Hall Institute of Medical Research, Immunology Division, Parkville, VIC 3052, Australia. The University of Melbourne, Department of Medical Biology, Parkville, VIC 3052, Australia. La Trobe University, La Trobe Institute for Molecular Science, Bundoora, VIC, Australia.
