Project description:Acute myeloid leukemia cell lines were treated with the hypomethylating agent decitabine and interferon gamma to investigate if these treatments induce HLA II gene expression. Cells carrying either control or CIITA-targeting sgRNAs were used to test the dependence of the HLA II induction on CIITA.
Project description:Acute myeloid leukemia cell lines were treated with the hypomethylating agent decitabine and interferon gamma to investigate if these treatments induce HLA II gene expression. Cells carrying either control or CIITA-targeting sgRNAs were used to tet
Project description:CD4+ T cell responses are crucial for inducing and maintaining effective anti-cancer immunity, and the identification of HLA-II cancer-specific epitopes is key to the development of potent cancer immunotherapies. In many tumor types, and especially in glioblastoma (GBM), HLA-II complexes are hardly ever naturally expressed. Hence, little is known about immunogenic HLA-II epitopes in GBM. With stable expression of CIITA coupled to a detailed and sensitive mass spectrometry based immunopeptidomics analysis, we here uncovered a remarkable breadth of the HLA-ligandome in HROG02, HROG17 and RA GBM cell lines. The effect of CIITA expression on the induction of the HLA-II presentation machinery was striking in each of the three cell lines, and it was significantly higher compared to IFNɣ treatment. In total, we identified 16,123 unique HLA-I peptides and 32,690 unique HLA-II peptides. In order to genuinely define the identified peptides as true HLA ligands, we carefully characterized their association with the different HLA allotypes. In addition, we identified 138 and 279 HLA-I and HLA-II ligands, respectively, most of which are novel in GBM, derived from known GBM-associated tumor-antigens that have been used as source proteins for a variety of GBM vaccines. Our data further indicate that CIITA-expressing GBM cells acquired an antigen presenting cell-like phenotype as we found that they directly present external proteins as HLA-II ligands. Not only that CIITA-expressing GBM cells are attractive models for antigen discovery endeavors, but such engineered cells have great therapeutic potential through massive presentation of a diverse antigenic repertoire.
Project description:Persistent therapy-resistant leukemia progenitor cells (LPC) are a main cause of disease relapse and recurrence in acute myeloid leukemia (AML). Specific LPC-targeting therapies may thus improve treatment outcome of AML patients. We demonstrated that LPCs present human leukocyte antigen (HLA)-restricted cancer antigens that induce T cell responses allowing for immune surveillance of AML. Using a mass spectrometry-based immunopeptidomics approach, we characterized the antigenic landscape of patient LPCs and identified AML/LPC-associated HLA-presented antigens including mutation-derived and cryptic neoepitopes as prime targets for development of T cell-based immunotherapeutic approaches. We observed frequent spontaneous memory T cells targeting these AML/LPC-associated antigens in AML patients and showed that antigen-specific T cell recognition and HLA class II immunopeptidome diversity impacts clinical outcome. Our results pave the way for implementation of AML/LPC-associated antigens for T cell-based immunotherapeutic approaches to specifically target and eliminate residual LPCs in AML patients.
Project description:Persistent therapy-resistant leukemic progenitor cells (LPC) are a main cause of disease relapse and recurrence in acute myeloid leukemia (AML). Specific LPC-targeting therapies may thus improve treatment outcome of AML patients. We demonstrate that LPCs present human leukocyte antigen (HLA)-restricted cancer antigens that induce T cell responses allowing for immune surveillance of AML. Using a mass spectrometry-based immunopeptidomics approach we characterized the antigenic landscape of patient LPCs and identify AML/LPC-associated HLA-presented antigens as well as mutation-derived and cryptic neoepitopes as prime targets for development of T cell-based immunotherapeutic approaches. We observed frequent spontaneous memory T cells targeting these AML/LPC-associated antigens in AML patients and showed that antigen-specific T cell recognition and HLA class II immunopeptidome diversity impacts clinical outcome. Our results pave the way for implementation of AML/LPC-associated antigens for T cell-based immunotherapeutic approaches to specifically target and eliminate residual LPCs in AML patients.
Project description:Identification of physiologically relevant peptide vaccine targets calls for the direct analysis of the entirety of naturally presented human leukocyte antigen (HLA) ligands, termed the HLA ligandome. In this study, we implemented this direct approach using immunoprecipitation and mass spectrometry to define acute myeloid leukemia (AML)-associated peptide vaccine targets. Mapping the HLA class I ligandomes of 15 AML patients and 35 healthy controls, more than 25 000 different naturally presented HLA ligands were identified. Target prioritization based on AML exclusivity and high presentation frequency in the AML cohort identified a panel of 132 LiTAAs (ligandome-derived tumor-associated antigens), and 341 corresponding HLA ligands (LiTAPs (ligandome-derived tumor-associated peptides)) represented subset independently in >20% of AML patients. Functional characterization of LiTAPs by interferon-γ ELISPOT (Enzyme-Linked ImmunoSpot) and intracellular cytokine staining confirmed AML-specific CD8+ T-cell recognition. Of note, our platform identified HLA ligands representing several established AML-associated antigens (e.g. NPM1, MAGED1, PRTN3, MPO, WT1), but found 80% of them to be also represented in healthy control samples. Mapping of HLA class II ligandomes provided additional CD4+ T-cell epitopes and potentially synergistic embedded HLA ligands, allowing for complementation of a multipeptide vaccine for the immunotherapy of AML.