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, WT1 and WT1 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.

Extremely strong infiltration of WT1-specific CTLs into mouse tumor by the combination vaccine with WT1-specific CTL and helper peptides.

In immunotherapy by cancer antigen-derived peptide vaccine, vaccination of cytotoxic T lymphocyte (CTL) peptide alone is common, while it remains unclear whether the addition of helper peptide vaccine to the CTL peptide vaccine is of great advantage for the enhancement of tumor immunity. In the present study, combination vaccine of Wilms' tumor gene 1(WT1) protein-derived CTL and helper peptides induced the strong infiltration of WT1-specific CD8 T cells into mouse tumor at frequencies of 8.8%, resulting in the formation of multiple microscopic necrotic lesions in the tumor, whereas the frequencies of WT1-specific CD8 T cell infiltration into the tumor in the vaccination of the CTL peptide alone were only 0.