Identification of two distinct populations of WT1-specific cytotoxic T lymphocytes in co-vaccination of WT1 killer and helper peptides

Wilms' tumor 1 -targeting cancer vaccine: Recent advancements and future perspectives

This mini-review explores recent advancements in cancer vaccines that target Wilms' tumor (WT1). Phase I/II trials of WT1 peptide vaccines have demonstrated their safety and efficacy against various cancers. Early trials employing HLA class I peptides evolved through their combination with HLA class II peptides, resulting in improved clinical outcomes. Additionally, WT1-targeted dendritic cell vaccines have exhibited favorable results. Studies focusing on hematological malignancies have revealed promising outcomes, including long-term remission and extended survival times. The combination of vaccines with immune checkpoint inhibitors has shown synergistic effects. Current preclinical developments are focused on enhancing the effectiveness of WT1 vaccines, underscoring the necessity for future large-scale Phase III trials to further elucidate their efficacy.

Decade-long WT1-specific CTLs induced by WT1 peptide vaccination

INTRODUCTION

The peptide-based cancer vaccine targeting Wilms' tumor 1 (WT1) is a promising immunotherapeutic strategy for hematological malignancies. It remains unclear how long and to what extent the WT1-specific CD8 + cytotoxic T cell (CTL) persist after WT1 peptide vaccination.

METHODS

The WT1 peptide vaccine was administered with written consent to a patient with CML in the chronic phase who did not respond well to imatinib, and the patient was followed for 12 years after vaccination. Immune monitoring was performed by specific amplification of WT1-specific CTLs using a mixed lymphocyte peptide culture. T-cell receptors (TCRs) of amplified WT1-specific CTLs were analyzed using next-generation sequencing. This study was approved by the Institutional Review Board of our institution.

RESULT

WT1-specific CTLs, which were initially detected during WT1 peptide vaccination, persisted at a frequency of less than 5 cells per 1,000,000 CD8 + T cells for more than 10 years. TCR repertoire analysis confirmed the diversity of WT1-specific CTLs 11 years after vaccination. CTLs exhibited WT1 peptide-specific cytotoxicity in vitro.

CONCLUSION

The WT1 peptide vaccine induced an immune response that persists for more than 10 years, even after cessation of vaccination in the CML patient.

WT1 Trio Peptide-Based Cancer Vaccine for Rare Cancers Expressing Shared Target WT1

No standard treatment has been established for most rare cancers. Here, we report a clinical trial of a biweekly WT1 tri-peptide-based vaccine for recurrent or advanced rare cancers. Due to the insufficient number of patients available for a traditional clinical trial, the trial was designed for rare cancers expressing shared target molecule WT1. The recruitment criteria included WT1-expressing tumors as well as HLA-A*24:02 or 02:01. The primary endpoints were immunoglobulin G (IgG) antibody (Ab) production against the WT1-235 cytotoxic T lymphocyte (CTL) epitope and delayed-type hypersensitivity (DTH) skin reactions to targeted WT1 CTL epitopes. The secondary endpoints were safety and clinical efficacy. Forty-five patients received WT1 Trio, and 25 (55.6%) completed the 3-month protocol treatment. WT1-235 IgG Ab was positive in 88.0% of patients treated with WT1 Trio at 3 months, significantly higher than 62.5% of the weekly WT1-235 CTL peptide vaccine. The DTH positivity rate in WT1 Trio was 62.9%, which was not significantly different from 60.7% in the WT1-235 CTL peptide vaccine. The WT1 Trio safety was confirmed without severe treatment-related adverse events, except grade 3 myasthenia gravis-like symptoms observed in a patient with thymic cancer. Fifteen (33.3%) patients achieved stable disease after 3 months of treatment. In conclusion, the biweekly WT1 Trio vaccine containing the WT1-332 helper T lymphocyte peptide induced more robust immune responses targeting WT1 than the weekly WT1-235 CTL peptide vaccine. Therefore, WT1-targeted immunotherapy may be a potential therapeutic strategy for rare cancers.

Identification of mouse helper epitopes for WT1-specific CD4+ T cells

Helper T lymphocytes (HTLs) play a central role in cancer immunity because they can not only help the induction and proliferation of cytotoxic T lymphocytes (CTLs) but also their differentiation into cytotoxic CD4⁺ T cells and directly kill the target cells.This study describes the identification of three novel mouse Th epitope peptides, WT1_35-52, WT1_86-102 and WT1_294-312, derived from WT1 protein, which is the most potent tumor-associated antigen. Compared to immunization with WT1 CTL peptide alone, immunization with the addition of these WT1-specific Th peptides strongly induced WT1-specific CTLs, continued to maintain them, and efficiently rejected the challenge of WT1-expressing tumor cells. Importantly, the majority of WT1-specific CTLs induced by the co-immunization with WT1 CTL and the WT1-specific Th peptides were CD44⁺CD62L^- effector memory CD8⁺ T cells, which played a central role in tumor rejection. Establishment of mouse models suitable for the analysis of the detailed mechanism of these functions of HTLs is very important. These results clearly showed that WT1-specific HTLs perform an essential function in WT1-specific tumor immunity. Therefore, the WT1-specific Th peptides identified here should make a major contribution to elucidation of the mutual roles of WT1-specific CTLs and HTLs in cancer immunity in in vivo mouse models.

Distinct difference in tumor-infiltrating immune cells between Wilms' tumor gene 1 peptide vaccine and anti-programmed cell death-1 antibody therapies

Background

Wilms’ tumor gene 1 (WT1) peptide vaccine and anti-programmed cell death-1 (anti-PD-1) antibody are expected as immunotherapies to improve the clinical outcome of glioblastoma. The aims of this study were to clarify how each immunotherapy affects tumor-infiltrating immune cells (TIIs) and to determine whether the combination of these two therapies could synergistically work.

Methods

Mice were transplanted with WT1 and programmed cell death-ligand 1 doubly expressing glioblastoma cells into brain followed by treatment with WT1 peptide vaccine, anti-PD-1 antibody, or the combination of the two, and survival of each therapy was compared. CD45⁺ cells were positively selected as TIIs from the brains with tumors, and TIIs were compared between WT1 peptide vaccine and anti-PD-1 antibody therapies.

Results

Most mice seemed to be cured by the combination therapy with WT1 peptide vaccine and anti-PD-1 antibody, which was much better survival than each monotherapy. A large number of CD4⁺ T cells, CD8⁺ T cells, and NK cells including WT1-specific CD8⁺ and CD4⁺ T cells infiltrated into the glioblastoma in WT1 peptide vaccine-treated mice. On the other hand, the number of TIIs did not increase, but instead PD-1 molecule expression was decreased on the majority of the tumor-infiltrating CD8⁺ T cells in the anti-PD-1 antibody-treated mice.

Conclusion

Our results clearly demonstrated that WT1 peptide vaccine and anti-PD-1 antibody therapies worked in the different steps of cancer-immunity cycle and that the combination of the two therapies could work synergistically against glioblastoma.