Development of a novel immunoproteasome digestion assay for synthetic long peptide vaccine design.

Hiroshi Wada,Satoshi Fukaya,Toshihiro Osada,Atsushi Shimizu,Eiji Sasaki,Yuki Tanaka,Stephen J Turner

doi:10.1371/journal.pone.0199249

Abstract

Recently, many autologous tumor antigens have been examined for their potential use in cancer immunotherapy. However, the success of cancer vaccines in clinical trials has been limited, partly because of the limitations of using single, short peptides in most attempts. With this in mind, we aimed to develop multivalent synthetic long peptide (SLP) vaccines containing multiple cytotoxic T-lymphocyte (CTL) epitopes. However, to confirm whether a multivalent vaccine can induce an individual epitope-specific CTL, the only viable screening strategies currently available are interferon-gamma (IFN-μ enzyme-linked immunospot (ELISPOT) assays using human peripheral blood mononuclear cells, or expensive human leukocyte antigen (HLA)-expressing mice. In this report, we evaluated the use of our developed murine-20S immunoproteasome (i20S) digestion assay, and found that it could predict the results of IFN-μ ELISPOT assays. Importantly, the murine-i20S digestion assay not only predicted CTL induction, but also antitumor activity in an HLA-expressing mouse model. We conclude that the murine-i20S digestion assay is an extremely useful tool for the development of “all functional” multivalent SLP vaccines.

Highlights

Cancer immunotherapy represents a major breakthrough in cancer treatment with the emergence of immune-checkpoint inhibitors such as anti- programmed death 1 (PD-1) and anticytotoxic T lymphocyte antigen 4 (CTLA4) [1, 2]
We evaluated whether the murine-20S immunoproteasome (i20S) digestion assay can predict CTL induction, and human leukocyte antigen (HLA)-dependent antitumor effects in a mouse model
20%, 50%, 40%, and 20% of mice in the SART293-101, W-S3-S2, S3b-S2-W, and S2-S3b-W treatment groups, respectively, were tumorfree on day 26. These results demonstrate that the murine-i20S digestion assay can predict the induction of CTLs, and their antitumor efficacy

Summary

Introduction

Cancer immunotherapy represents a major breakthrough in cancer treatment with the emergence of immune-checkpoint inhibitors such as anti- programmed death 1 (PD-1) and anticytotoxic T lymphocyte antigen 4 (CTLA4) [1, 2]. Cancer vaccines have been expected to elicit antitumor responses through the activation of the immune system, and become a novel therapeutic technique. Over the last 20 years, many human tumor-associated antigens (TAAs) have been identified, and clinical studies of epitope peptides derived from the sequence of TAAs have been carried out in patients with metastatic cancer. These peptide-based cancer vaccines activate cytotoxic T-lymphocytes (CTLs) which recognize the identical antigenic peptides presented on the surface of cancer.

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