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Admon A. The biogenesis of the immunopeptidome. Semin Immunol 2023; 67:101766. [PMID: 37141766 DOI: 10.1016/j.smim.2023.101766] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 04/26/2023] [Accepted: 04/26/2023] [Indexed: 05/06/2023]
Abstract
The immunopeptidome is the repertoire of peptides bound and presented by the MHC class I, class II, and non-classical molecules. The peptides are produced by the degradation of most cellular proteins, and in some cases, peptides are produced from extracellular proteins taken up by the cells. This review attempts to first describe some of its known and well-accepted concepts, and next, raise some questions about a few of the established dogmas in this field: The production of novel peptides by splicing is questioned, suggesting here that spliced peptides are extremely rare, if existent at all. The degree of the contribution to the immunopeptidome by degradation of cellular protein by the proteasome is doubted, therefore this review attempts to explain why it is likely that this contribution to the immunopeptidome is possibly overstated. The contribution of defective ribosome products (DRiPs) and non-canonical peptides to the immunopeptidome is noted and methods are suggested to quantify them. In addition, the common misconception that the MHC class II peptidome is mostly derived from extracellular proteins is noted, and corrected. It is stressed that the confirmation of sequence assignments of non-canonical and spliced peptides should rely on targeted mass spectrometry using spiking-in of heavy isotope-labeled peptides. Finally, the new methodologies and modern instrumentation currently available for high throughput kinetics and quantitative immunopeptidomics are described. These advanced methods open up new possibilities for utilizing the big data generated and taking a fresh look at the established dogmas and reevaluating them critically.
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Affiliation(s)
- Arie Admon
- Faculty of Biology, Technion-Israel Institute of Technology, Israel.
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2
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Marijt KA, Griffioen L, Blijleven L, van der Burg SH, van Hall T. Cross-presentation of a TAP-independent signal peptide induces CD8 T immunity to escaped cancers but necessitates anchor replacement. Cancer Immunol Immunother 2021; 71:289-300. [PMID: 34142235 PMCID: PMC8783882 DOI: 10.1007/s00262-021-02984-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 06/08/2021] [Indexed: 12/22/2022]
Abstract
Cancer cells frequently display defects in their antigen-processing pathway and thereby evade CD8 T cell immunity. We described a novel category of cancer antigens, named TEIPP, that emerge on cancers with functional loss of the peptide pump TAP. TEIPPs are non-mutated neoantigens despite their ‘self’ origin by virtue of their absence on normal tissues. Here, we describe the development of a synthetic long peptide (SLP) vaccine for the most immunogenic TEIPP antigen identified thus far, derived from the TAP-independent LRPAP1 signal sequence. LRPAP121–30-specific CD8 T cells were present in blood of all tested healthy donors as well as patients with non-small cell lung adenocarcinoma. SLPs with natural flanking, however, failed to be cross-presented by monocyte-derived dendritic cells. Since the C-terminus of LRPAP121–30 is an unconventional and weakly binding serine (S), we investigated if replacement of this anchor would result in efficient cross-presentation. Exchange into a valine (V) resulted in higher HLA-A2 binding affinity and enhanced T cell stimulation. Importantly, CD8 T cells isolated using the V-variant were able to bind tetramers with the natural S-variant and respond to TAP-deficient cancer cells. A functional screen with an array of N-terminal and C-terminal extended SLPs pointed at the 24-mer V-SLP, elongated at the N-terminus, as most optimal vaccine candidate. This SLP was efficiently cross-presented and consistently induced a strong polyclonal LRPAP121–30-specific CD8 T cells from the endogenous T cell repertoire. Thus, we designed a TEIPP SLP vaccine from the LRPAP1 signal sequence ready for validation in clinical trials.
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Affiliation(s)
- Koen A Marijt
- Department of Medical Oncology, C7-P, Oncode Institute, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - Lisa Griffioen
- Department of Medical Oncology, C7-P, Oncode Institute, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - Laura Blijleven
- Department of Medical Oncology, C7-P, Oncode Institute, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - Sjoerd H van der Burg
- Department of Medical Oncology, C7-P, Oncode Institute, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - Thorbald van Hall
- Department of Medical Oncology, C7-P, Oncode Institute, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands.
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3
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Szakacs G, Abele R. An inventory of lysosomal ABC transporters. FEBS Lett 2020; 594:3965-3985. [DOI: 10.1002/1873-3468.13967] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 09/23/2020] [Accepted: 10/15/2020] [Indexed: 12/13/2022]
Affiliation(s)
- Gergely Szakacs
- Institute of Enzymology Research Centre of Natural Sciences Eötvös Loránd Research Network Budapest Hungary
- Institute of Cancer Research Medical University of Vienna Vienna Austria
| | - Rupert Abele
- Institute of Biochemistry Goethe‐University Frankfurt am Main Frankfurt am Main Germany
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4
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Marijt KA, van Hall T. To TAP or not to TAP: alternative peptides for immunotherapy of cancer. Curr Opin Immunol 2020; 64:15-19. [PMID: 31952027 DOI: 10.1016/j.coi.2019.12.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 12/11/2019] [Indexed: 12/27/2022]
Abstract
Intracellular processing of antigens is crucial for the generation of T cell immunity towards cancers, since cleaved protein products are the molecular targets of these adaptive lymphocytes. The majority of antigenic peptides requires the TAP transporter to gain access to the peptide loading complex in the ER lumen where they bind MHC class I (MHC-I). This pivotal role of TAP in antigen processing makes the system vulnerable for modifications in cancer cells and indeed human cancers frequently silence this gene epigenetically. Interestingly, TAP-independent processing pathways then become apparent and partly restore MHC class I presentation with alternative peptides. In this review we discuss recent insights on how TAP-independent processing of immunogenic peptides occurs, and how these antigens can be exploited for cancer immunotherapy.
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Affiliation(s)
- Koen A Marijt
- Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands
| | - Thorbald van Hall
- Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands.
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5
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Del Val M, Antón LC, Ramos M, Muñoz-Abad V, Campos-Sánchez E. Endogenous TAP-independent MHC-I antigen presentation: not just the ER lumen. Curr Opin Immunol 2020; 64:9-14. [PMID: 31935516 DOI: 10.1016/j.coi.2019.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 12/11/2019] [Indexed: 11/30/2022]
Abstract
Altered and infected cells are eliminated by CD8+ cytotoxic T lymphocytes. This requires production of antigenic peptides mostly in the cytosol, transport to the endoplasmic reticulum (ER) by the transporter associated with antigen processing (TAP), and cell surface presentation by major histocompatibility complex class I (MHC-I). Strikingly, antigen presentation occurs without TAP, although it is inefficient and associated to human pathology. TAP-independent peptides derive both from membrane and secreted proteins, as well as cytosolic ones. The efficiency of TAP-independent presentation may be impacted by the availability of receptive MHC-I, and in turn by the functional presence in the ER of the peptide-loading complex, itself anchored on TAP. Without TAP, surface expression of human leukocyte antigen (HLA)-B allotypes varies widely, with those presenting a broader peptide repertoire among the most TAP-independent. Much remains to be learned on the alternative cellular pathways for antigen presentation in the absence of TAP.
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Affiliation(s)
- Margarita Del Val
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolás Cabrera 1, 28049 Madrid, Spain.
| | - Luis C Antón
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Manuel Ramos
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Víctor Muñoz-Abad
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Elena Campos-Sánchez
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolás Cabrera 1, 28049 Madrid, Spain
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6
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Vigneron N, Ferrari V, Van den Eynde BJ, Cresswell P, Leonhardt RM. Cytosolic Processing Governs TAP-Independent Presentation of a Critical Melanoma Antigen. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2018; 201:1875-1888. [PMID: 30135181 PMCID: PMC6457910 DOI: 10.4049/jimmunol.1701479] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 07/26/2018] [Indexed: 12/30/2022]
Abstract
Cancer immunotherapy has been flourishing in recent years with remarkable clinical success. But as more patients are treated, a shadow is emerging that has haunted other cancer therapies: tumors develop resistance. Resistance is often caused by defects in the MHC class I Ag presentation pathway critical for CD8 T cell-mediated tumor clearance. TAP and tapasin, both key players in the pathway, are frequently downregulated in human cancers, correlating with poor patient survival. Reduced dependence on these factors may promote vaccine efficiency by limiting immune evasion. In this study, we demonstrate that PMEL209-217, a promising phase 3 trial-tested antimelanoma vaccine candidate, is robustly presented by various TAP- and/or tapasin-deficient cell lines. This striking characteristic may underlie its potency as a vaccine. Surprisingly, cytosolic proteasomes generate the peptide even for TAP-independent presentation, whereas tripeptidyl peptidase 2 (TPP2) efficiently degrades the epitope. Consequently, inhibiting TPP2 substantially boosts PMEL209-217 presentation, suggesting a possible strategy to improve the therapeutic efficacy of the vaccine.
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Affiliation(s)
- Nathalie Vigneron
- Ludwig Institute for Cancer Research, Brussels B-1200, Belgium
- de Duve Institute, University of Louvain, Brussels B-1200, Belgium
- Walloon Excellence in Life Sciences and Biotechnology, Brussels B-1200, Belgium
| | - Violette Ferrari
- Ludwig Institute for Cancer Research, Brussels B-1200, Belgium
- de Duve Institute, University of Louvain, Brussels B-1200, Belgium
- Walloon Excellence in Life Sciences and Biotechnology, Brussels B-1200, Belgium
| | - Benoît J Van den Eynde
- Ludwig Institute for Cancer Research, Brussels B-1200, Belgium;
- de Duve Institute, University of Louvain, Brussels B-1200, Belgium
- Walloon Excellence in Life Sciences and Biotechnology, Brussels B-1200, Belgium
| | - Peter Cresswell
- Department of Immunobiology, Yale University, New Haven, CT 06519; and
- Department of Cell Biology, Yale University, New Haven, CT 06519
| | - Ralf M Leonhardt
- Department of Immunobiology, Yale University, New Haven, CT 06519; and
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7
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Marijt KA, Doorduijn EM, van Hall T. TEIPP antigens for T-cell based immunotherapy of immune-edited HLA class I low cancers. Mol Immunol 2018; 113:43-49. [PMID: 29627136 DOI: 10.1016/j.molimm.2018.03.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 01/11/2018] [Accepted: 03/29/2018] [Indexed: 12/30/2022]
Abstract
T-cell based immunotherapies through checkpoint blockade or adoptive transfer are effective treatments for a wide range of cancers like melanomas and lung carcinomas that harbor a high mutational load. The HLA class I and class II (HLA-I and HLA-II) presented neoantigens arise from genetic mutations in the cancerous cells and are ideal non-self targets for the T cell-based treatments. Although some cancer patients responded with complete regression, many others are irresponsive to checkpoint blockade treatments, or relapse after initial success. One of the mechanisms by which tumors evade T cell recognition is by acquiring deficiencies in the HLA-I antigen-processing pathway, leading to downregulation of HLA-I molecules at the cell surface and thereby creating an 'invisible' tumor phenotype. Interestingly, an alternative antigen repertoire arises on these HLA-Ilow cancer cells. We refer to this alternative antigen repertoire as TEIPP: T cell epitopes associated with impaired peptide processing. TEIPP antigens are curious non-mutated peptides from housekeeping proteins that are not presented in homeostasis. In this review, for the first time we recapitulate all our published work on TEIPP antigens, including our recent understanding of the CD8 T cell repertoire. We are convinced that TEIPP-directed T cells will be valuable resources to target immune-edited tumors that have acquired resistance to checkpoint blockade therapy.
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Affiliation(s)
- Koen A Marijt
- Department of Medical Oncology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Elien M Doorduijn
- Department of Medical Oncology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Thorbald van Hall
- Department of Medical Oncology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.
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8
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Hafstrand I, Doorduijn EM, Sun R, Talyzina A, Sluijter M, Pellegrino S, Sandalova T, Duru AD, van Hall T, Achour A. The Immunogenicity of a Proline-Substituted Altered Peptide Ligand toward the Cancer-Associated TEIPP Neoepitope Trh4 Is Unrelated to Complex Stability. THE JOURNAL OF IMMUNOLOGY 2018; 200:2860-2868. [PMID: 29507106 DOI: 10.4049/jimmunol.1700228] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 02/07/2018] [Indexed: 01/05/2023]
Abstract
Human cancers frequently display defects in Ag processing and presentation allowing for immune evasion, and they therefore constitute a significant challenge for T cell-based immunotherapy. We have previously demonstrated that the antigenicity of tumor-associated Ags can be significantly enhanced through unconventional residue modifications as a novel tool for MHC class I (MHC-I)-based immunotherapy approaches. We have also previously identified a novel category of cancer neo-epitopes, that is, T cell epitopes associated with impaired peptide processing (TEIPP), that are selectively presented by MHC-I on cells lacking the peptide transporter TAP. In this study, we demonstrate that substitution of the nonanchoring position 3 into a proline residue of the first identified TEIPP peptide, the murine Trh4, results in significantly enhanced recognition by antitumor CTLs toward the wild-type epitope. Although higher immunogenicity has in most cases been associated with increased MHC/peptide complex stability, our results demonstrate that the overall stability of H-2Db in complex with the highly immunogenic altered peptide ligand Trh4-p3P is significantly reduced compared with wild-type H-2Db/Trh4. Comparison of the crystal structures of the H-2Db/Trh4-p3P and H-2Db/Trh4 complexes revealed that the conformation of the nonconventional methionine anchor residue p5M is altered, deleting its capacity to form adequate sulfur-π interactions with H-2Db residues, thus reducing the overall longevity of the complex. Collectively, our results indicate that vaccination with Thr4-p3P significantly enhances T cell recognition of targets presenting the wild-type TEIPP epitope and that higher immunogenicity is not necessarily directly related to MHC/peptide complex stability, opening for the possibility to design novel peptide vaccines with reduced MHC/peptide complex stability.
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Affiliation(s)
- Ida Hafstrand
- Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, 17165 Stockholm, Sweden.,Department of Infectious Diseases, Karolinska University Hospital, Solna, 17176 Stockholm, Sweden
| | - Elien M Doorduijn
- Medical Oncology, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands
| | - Renhua Sun
- Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, 17165 Stockholm, Sweden.,Department of Infectious Diseases, Karolinska University Hospital, Solna, 17176 Stockholm, Sweden
| | - Anna Talyzina
- Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, 17165 Stockholm, Sweden.,Department of Infectious Diseases, Karolinska University Hospital, Solna, 17176 Stockholm, Sweden
| | - Marjolein Sluijter
- Medical Oncology, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands
| | - Sara Pellegrino
- Department of Pharmaceutical Science, General and Organic Chemistry Section, University of Milan, 20133 Milan, Italy
| | - Tatyana Sandalova
- Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, 17165 Stockholm, Sweden.,Department of Infectious Diseases, Karolinska University Hospital, Solna, 17176 Stockholm, Sweden
| | - Adil Doganay Duru
- Cell Therapy Institute, Nova Southeastern University, Fort Lauderdale, FL 33314; and.,College of Allopathic Medicine, Nova Southeastern University, Fort Lauderdale, FL 33328
| | - Thorbald van Hall
- Medical Oncology, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands;
| | - Adnane Achour
- Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, 17165 Stockholm, Sweden; .,Department of Infectious Diseases, Karolinska University Hospital, Solna, 17176 Stockholm, Sweden
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9
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van der Burg SH, Arens R, Ossendorp F, van Hall T, Melief CJM. Vaccines for established cancer: overcoming the challenges posed by immune evasion. Nat Rev Cancer 2016; 16:219-33. [PMID: 26965076 DOI: 10.1038/nrc.2016.16] [Citation(s) in RCA: 494] [Impact Index Per Article: 61.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Therapeutic vaccines preferentially stimulate T cells against tumour-specific epitopes that are created by DNA mutations or oncogenic viruses. In the setting of premalignant disease, carcinoma in situ or minimal residual disease, therapeutic vaccination can be clinically successful as monotherapy; however, in established cancers, therapeutic vaccines will require co-treatments to overcome immune evasion and to become fully effective. In this Review, we discuss the progress that has been made in overcoming immune evasion controlled by tumour cell-intrinsic factors and the tumour microenvironment. We summarize how therapeutic benefit can be maximized in patients with established cancers by improving vaccine design and by using vaccines to increase the effects of standard chemotherapies, to establish and/or maintain tumour-specific T cells that are re-energized by checkpoint blockade and other therapies, and to sustain the antitumour response of adoptively transferred T cells.
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Affiliation(s)
| | - Ramon Arens
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - Ferry Ossendorp
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | | | - Cornelis J M Melief
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
- ISA Pharmaceuticals, J. H. Oortweg 19, 2333 CH, Leiden, The Netherlands
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10
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Hafstrand I, Doorduijn EM, Duru AD, Buratto J, Oliveira CC, Sandalova T, van Hall T, Achour A. The MHC Class I Cancer-Associated Neoepitope Trh4 Linked with Impaired Peptide Processing Induces a Unique Noncanonical TCR Conformer. THE JOURNAL OF IMMUNOLOGY 2016; 196:2327-34. [PMID: 26800871 DOI: 10.4049/jimmunol.1502249] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 12/18/2015] [Indexed: 11/19/2022]
Abstract
MHC class I downregulation represents a significant challenge for successful T cell-based immunotherapy. T cell epitopes associated with impaired peptide processing (TEIPP) constitute a novel category of immunogenic Ags that are selectively presented on transporter associated with Ag processing-deficient cells. The TEIPP neoepitopes are CD8 T cell targets, derived from nonmutated self-proteins that might be exploited to prevent immune escape. In this study, the crystal structure of H-2D(b) in complex with the first identified TEIPP Ag (MCLRMTAVM) derived from the Trh4 protein has been determined to 2.25 Å resolution. In contrast to prototypic H-2D(b) peptides, Trh4 takes a noncanonical peptide-binding pattern with extensive sulfur-π interactions that contribute to the overall complex stability. Importantly, the noncanonical methionine at peptide position 5 acts as a main anchor, altering only the conformation of the H-2D(b) residues Y156 and H155 and thereby forming a unique MHC/peptide conformer that is essential for recognition by TEIPP-specific T cells. Substitution of peptide residues p2C and p5M to the conservative α-aminobutyric acid and norleucine, respectively, significantly reduced complex stability, without altering peptide conformation or T cell recognition. In contrast, substitution of p5M to a conventional asparagine abolished recognition by the H-2D(b)/Trh4-specific T cell clone LnB5. We anticipate that the H-2D(b)/Trh4 complex represents the first example, to our knowledge, of a broader repertoire of alternative MHC class I binders.
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Affiliation(s)
- Ida Hafstrand
- Science for Life Laboratory, Department of Medicine, Solna, Karolinska Institutet, SE-10450 Stockholm, Sweden; and
| | - Elien M Doorduijn
- Clinical Oncology, Leiden University Medical Center, Leiden 2333 ZA, the Netherlands
| | - Adil Doganay Duru
- Science for Life Laboratory, Department of Medicine, Solna, Karolinska Institutet, SE-10450 Stockholm, Sweden; and
| | - Jeremie Buratto
- Science for Life Laboratory, Department of Medicine, Solna, Karolinska Institutet, SE-10450 Stockholm, Sweden; and
| | | | - Tatyana Sandalova
- Science for Life Laboratory, Department of Medicine, Solna, Karolinska Institutet, SE-10450 Stockholm, Sweden; and
| | - Thorbald van Hall
- Clinical Oncology, Leiden University Medical Center, Leiden 2333 ZA, the Netherlands
| | - Adnane Achour
- Science for Life Laboratory, Department of Medicine, Solna, Karolinska Institutet, SE-10450 Stockholm, Sweden; and
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11
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Oliveira CC, van Hall T. Alternative Antigen Processing for MHC Class I: Multiple Roads Lead to Rome. Front Immunol 2015; 6:298. [PMID: 26097483 PMCID: PMC4457021 DOI: 10.3389/fimmu.2015.00298] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/22/2015] [Indexed: 12/31/2022] Open
Abstract
The well described conventional antigen-processing pathway is accountable for most peptides that end up in MHC class I molecules at the cell surface. These peptides experienced liberation by the proteasome and transport by the peptide transporter TAP. However, there are multiple roads that lead to Rome, illustrated by the increasing number of alternative processing pathways that have been reported during last years. Interestingly, TAP-deficient individuals do not succumb to viral infections, suggesting that CD8 T cell immunity is sufficiently supported by alternative TAP-independent processing pathways. To date, a diversity of viral and endogenous TAP-independent peptides have been identified in the grooves of different MHC class I alleles. Some of these peptides are not displayed by normal TAP-positive cells and we therefore called them TEIPP, for “T-cell epitopes associated with impaired peptide processing.” TEIPPs are hidden self-antigens, are derived from normal housekeeping proteins, and are processed via unconventional processing pathways. Per definition, TEIPPs are presented via TAP-independent pathways, but recent data suggest that part of this repertoire still depend on proteasome and metalloprotease activity. An exception is the C-terminal peptide of the endoplasmic reticulum (ER)-membrane-spanning ceramide synthase Trh4 that is surprisingly liberated by the signal peptide peptidase (SPP), the proteolytic enzyme involved in cleaving leader sequences. The intramembrane cleaving SPP is thereby an important contributor of TAP-independent peptides. Its family members, like the Alzheimer’s related presenilins, might contribute as well, according to our preliminary data. Finally, alternative peptide routing is an emerging field and includes processes like the unfolded protein response, the ER-associated degradation, and autophagy-associated vesicular pathways. These data convince us that there is a world to be discovered in the field of unconventional antigen processing.
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Affiliation(s)
- Cláudia C Oliveira
- Department of Clinical Oncology, Leiden University Medical Center , Leiden , Netherlands
| | - Thorbald van Hall
- Department of Clinical Oncology, Leiden University Medical Center , Leiden , Netherlands
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