Hos et al. showed that transfection of tumor cells lacking MHC-II with full-length human MHC-II transactivator (CIITA) cDNA induced stable expression of cell surface MHC-II and appropriate subcellular localization and function of processing machinery (CD74 and H2-DM) for MHC-II peptide presentation. MS analysis of peptides eluted from purified MHC-II molecules identified shared cancer oncoviral, and neo-epitope peptides, which when synthesized and presented by DCs, were recognized similarly to endogenous peptides by CD4+ T cells in vitro. Vaccination with adjuvanted synthetic peptides induced CD4+ T cell responses in tumor-bearing mice.
Contributed by Paula Hochman
ABSTRACT: We report an approach to identify tumor-specific CD4(+) T cell neo-epitopes of both mouse and human cancer cells by analysis of major histocompatibility complex (MHC) class II-eluted natural peptides. MHC class II-presented peptide sequences are identified by introducing the MHC class II transactivator (CIITA) in tumor cells that were originally MHC class II negative. CIITA expression facilitates cell-surface expression of MHC class II molecules and the appropriate peptide-loading machinery. Peptide elution of purified MHC class II molecules and subsequent mass spectrometry reveals oncoviral- and neo-epitopes as well as shared epitopes. Immunological relevance of these epitopes is shown by natural presentation by dendritic cells and immunogenicity. Synthetic peptide vaccination induced functional CD4(+) T cell responses, which helped tumor control in vivo. Thus, this CIITA transfection approach aids to identify relevant T helper epitopes presented by any MHC class II allele that would be otherwise very difficult to predict and reveals important targets for cancer immunotherapy.
Author Info: (1) Leiden University Medical Center, Department Immunology, Leiden, the Netherlands. (2) Leiden University Medical Center, Department Immunology, Leiden, the Netherlands. (3) Leid
Author Info: (1) Leiden University Medical Center, Department Immunology, Leiden, the Netherlands. (2) Leiden University Medical Center, Department Immunology, Leiden, the Netherlands. (3) Leiden University Medical Center, Department Immunology, Leiden, the Netherlands. (4) Leiden University Medical Center, Department Immunology, Leiden, the Netherlands. (5) Leiden University Medical Center, Department Pathology, Leiden, the Netherlands. (6) Leiden University Medical Center, Department Pathology, Leiden, the Netherlands. (7) Leiden University Medical Center, Center for Proteomics & Metabolomics, Leiden, the Netherlands. (8) Leiden University Medical Center, Center for Proteomics & Metabolomics, Leiden, the Netherlands. (9) Leiden University Medical Center, Department Immunology, Leiden, the Netherlands. (10) Leiden University Medical Center, Department Pathology, Leiden, the Netherlands. (11) Leiden University Medical Center, Center for Proteomics & Metabolomics, Leiden, the Netherlands. (12) Leiden University Medical Center, Department Immunology, Leiden, the Netherlands. Electronic address: F.A.Ossendorp@lumc.nl.
