W160 - Immunopeptidome Overlap Between HLA-DR Alleles in Heterozygous Dendritic Cells Pulsed with the Same Antigen

Gonzalo Lázaro, Immunology Unit, Department of Cell Biology, Physiology, and Immunology, Institut de Biotecnologia i Biomedicina (IBB) – Universitat Autonoma de Barcelona; Andrea Aran, Immunology Unit, Department of Cell Biology, Physiology, and Immunology, Institut de Biotecnologia i Biomedicina (IBB) – Universitat Autonoma de Barcelona; maitane Faus-cid, Immunology Unit, Department of Cell Biology, Physiology, and Immunology, Institut de Biotecnologia i Biomedicina (IBB) – Universitat Autonoma de Barcelona; Laia Garrigós, International Breast Cancer Center (IBCC), Pangaea Oncology, Quironsalud Group, Barcelona, Spain. – Quironsalud Group; Juan Cedano, Institut de Biotecnologia i Biomedicina. Departament de Bioquímica i Biologia Molecular – Universitat Autonoma de Barcelona; Javier Cortés, International Breast Cancer Center (IBCC). – Quironsalud Group

Abstract Text: The anti-tumor immune response is crucial for the elimination of tumor cells. Typically, the presence of Tumor-Infiltrating Lymphocytes (TILs) often correlates with favorable patient prognoses. But, among anti-tumor T cells, CD4+ T lymphocytes play a pivotal role in the initial phases, acting as orchestrators of the immune response in two possible ways: as effector or regulatory cells. Previosly, we compared the CDR3-TCR motifs expressed by in vitro expanded and then sorted CD4-TILs and CD8-TILs. The results suggested a more homogeneity among breast cancer samples in the CD4-TILs compared to CD8-TILs, suggesting this could be attributed to a less diverse immunopeptidome presented by MHC-II. Therefore, immunopeptidomic data from dendritic cells (DCs) pulsed with MCF-7 cell line extract were obtained from HLA heterozygous donors. Our objective was to analyze peptide overlap, comparing the proteins presented by different MHC class II molecules (HLA-DR alleles). Key findings include: (i) significant peptide and protein overlap among different HLA-DR alleles in both pulsed and non-pulsed samples; (ii) identification of only 4.5% of MCF-7 cell line proteome in pulsed DC samples; (iii) influence of certain alleles, such as DRB1*13:02, by the donor-paired allele and increased exclusive proteins in others, like DRB1*03:01 or DRB1*04:04. This study suggests that the presentation of cancer-related proteins may be influenced by the behavior of HLA-DR alleles. Consequently, understanding differences in peptide-loaded HLA-DR alleles is crucial. Such insights could inform the design of therapies utilizing DCs pulsed with peptides, enhancing the intervention of CD4+ TILs across diverse patient populations.