To induce and activate
tumor-associated
antigen-specific cytotoxic T lymphocytes (CTLs) for
cancer immunity, it is important not only to select potent CTL
epitopes but also to combine them with appropriate immunopotentiating agents. Here we investigated whether
tumor immunity induced by WT1
peptide vaccination could be enhanced by IFN-β. For the experimental group, C57BL/6 mice were twice pre-treated with WT1
peptide vaccine, implanted with WT1-expressing C1498 cells, and treated four times with WT1
peptide vaccine at one-week intervals. During the vaccination period, IFN-β was injected three times a week. Mice in control groups were treated with WT1
peptide alone, IFN-β alone, or PBS alone. The mice in the experimental group rejected
tumor cells and survived significantly longer than mice in the control groups. The overall survival on day 75 was 40% for the mice treated with WT1 peptide+IFN-β, while it was 7, 7, and 0% for those treated with WT1
peptide alone, IFN-β alone or PBS alone, respectively. Induction of WT1-specific CTLs and enhancement of NK activity were detected in splenocytes from mice in the experimental group. Furthermore, administration of IFN-β enhanced expression of
MHC class I molecules on the implanted
tumor cells. In conclusion, our results showed that co-administration of WT1 peptide+IFN-β enhanced
tumor immunity mainly through the induction of WT1-specific CTLs, enhancement of NK activity, and promotion of MHC class I expression on the
tumor cells. WT1
peptide vaccination combined with IFN-β administration can thus be expected to enhance the clinical efficacy of WT1
immunotherapy.