An immunogenic WT1-derived peptide that induces T cell response in the context of HLA-A*02:01 and HLA-A*24:02 molecules.

ABSTRACT

The Wilms' tumor oncogene protein (WT1) is a highly validated tumor antigen for immunotherapy. WT1-targeted immunotherapy has been extensively explored in multiple human trials in various cancers. However, clinical investigations using WT1 epitopes have generally focused on two peptides, HLA-restricted to HLA-A*0201 or HLA-A*2402. The goal of this study was to identify new epitopes derived from WT1, to expand the potential use of WT1 as a target of immunotherapy. Using computer-based MHC-binding algorithms and in vitro validation of the T cell responses specific for the identified peptides, we found that a recently identified HLA-A*2402-binding epitope (239-247), NQMNLGATL (NQM), was also a strong CD8+ T cell epitope for HLA-A*0201 molecule. A peptide second position Q240L substitution (NLM) or Q240Y substitution (NYM), further enhanced the T cell responses in both HLA-A*0201 positive and HLA-A*2402 positive healthy donors. Importantly, T cells stimulated with the new analog peptides displayed heteroclitic cross-reactivity with the native NQM sequence and were able to kill HLA-matched WT1-positive tumor cell lines and primary leukemia blasts. In addition, longer native and heteroclitic HLA-DR.B1-binding peptides, comprising the nine amino acid NQM or NLM sequences, could induce T cell response that recognized the CD8+ epitope NQM, suggesting the processing and the presentation by HLA-A*0201 molecules of the CD8+ T cell epitope embedded within it. Our studies suggest that the analog peptides NLM and NYM could be potential candidates for future immunotherapy targeting WT1 positive cancers in the context of HLA-A*0201 and A*2402 positive populations.