The HLA ligandome landscape of chronic myeloid leukemia delineates novel T-cell epitopes for immunotherapy.

Antileukemia immunity plays an important role in disease control and maintenance of tyrosine kinase inhibitor (TKI)-free remission in chronic myeloid leukemia (CML). Thus, antigen-specific immunotherapy holds promise for strengthening immune control in CML but requires the identification of CML-associated targets. In this study, we used a mass spectrometry-based approach to identify naturally presented HLA class I- and class II-restricted peptides in primary CML samples. Comparative HLA ligandome profiling using a comprehensive dataset of different hematological benign specimens and samples from CML patients in deep molecular remission delineated a panel of novel frequently presented CML-exclusive peptides. These nonmutated target antigens are of particular relevance because our extensive data-mining approach suggests the absence of naturally presented BCR-ABL- and ABL-BCR-derived HLA-restricted peptides and the lack of frequent tumor-exclusive presentation of known cancer/testis and leukemia-associated antigens. Functional characterization revealed spontaneous T-cell responses against the newly identified CML-associated peptides in CML patient samples and their ability to induce multifunctional and cytotoxic antigen-specific T cells de novo in samples from healthy volunteers and CML patients. Thus, these antigens are prime candidates for T-cell-based immunotherapeutic approaches that may prolong TKI-free survival and even mediate cure of CML patients.

The immunopeptidomic landscape of ovarian carcinomas.

Immunotherapies, particularly checkpoint inhibitors, have set off a revolution in cancer therapy by releasing the power of the immune system. However, only little is known about the antigens that are essentially presented on cancer cells, capable of exposing them to immune cells. Large-scale HLA ligandome analysis has enabled us to exhaustively characterize the immunopeptidomic landscape of epithelial ovarian cancers (EOCs). Additional comparative profiling with the immunopeptidome of a variety of benign sources has unveiled a multitude of ovarian cancer antigens (MUC16, MSLN, LGALS1, IDO1, KLK10) to be presented by HLA class I and class II molecules exclusively on ovarian cancer cells. Most strikingly, ligands derived from mucin 16 and mesothelin, a molecular axis of prognostic importance in EOC, are prominent in a majority of patients. Differential gene-expression analysis has allowed us to confirm the relevance of these targets for EOC and further provided important insights into the relationship between gene transcript levels and HLA ligand presentation.

Human CD8(+) T Cells Target Multiple Epitopes in Respiratory Syncytial Virus Polymerase.

Respiratory syncytial virus (RSV) infection is a serious health problem in young children, immunocompromised patients, and the elderly. The development of novel prevention strategies, such as a vaccine to RSV, is a high priority. One strategy is to design a peptide-based vaccine that activates appropriate CD8(+) T-cell responses. However, this approach is limited by the low number of RSV peptide epitopes defined to date that activate CD8(+) T cells. We aimed to identify peptide epitopes that are presented by common human leukocyte antigen types (HLA-A*01, -A*02, and -B*07). We identify one novel HLA-A*02-restricted and two novel HLA-A*01-restricted peptide epitopes from RSV polymerase. Peptide-HLA multimer staining of specific T cells from healthy donor peripheral blood mononuclear cell, the memory phenotype of such peptide-specific T cells ex vivo, and functional IFNγ responses in short-term stimulation assays suggest that these peptides are recognized during RSV infection. Such peptides are candidates for inclusion into a peptide-based RSV vaccine designed to stimulate defined CD8(+) T-cell responses.

Identification of a Novel Immunodominant HLA-B*07: 02-restricted Adenoviral Peptide Epitope and Its Potential in Adoptive Transfer Immunotherapy.

Adenovirus infections of immunocompromised patients, particularly following allogeneic hematopoietic stem cell transplantation, are associated with morbidity and mortality. Immunotherapy by adoptive transfer of hexon-specific and penton-specific T cells has been successfully applied, but many approaches are impeded by the low number of HLA class I-restricted adenoviral peptide epitopes described to date. We use a novel method to identify naturally presented adenoviral peptide epitopes from infected human cells, ectopically expressing defined HLA, using peptide elution and liquid chromatography-mass spectrometry analysis. We show that the previously described HLA-A*01:01-restricted peptide epitope LTDLGQNLLY from hexon protein is naturally presented, and demonstrate the functionality of LTDLGQNLLY-specific T cells. We further identify a novel immunodominant HLA-B*07:02-restricted peptide epitope VPATGRTLVL from protein 13.6 K, and demonstrate the high proliferative, cytotoxic, and IFN-γ-producing capacity of peptide-specific T cells. Lastly, LTDLGQNLLY-specific T cells can be detected ex vivo following adoptive transfer therapy, and LTDLGQNLLY-specific and VPATGRTLVL-specific T cells have memory phenotypes ex vivo. Given their proliferative and cytotoxic capacity, such epitope-specific T cells are promising candidates for adoptive T-cell transfer therapy of adenovirus infection.