The anti-tumor effect of oral cancer vaccine using Bifidobacterium as a platform for displaying Wilms’ tumor 1 protein.

Abstract

72 Background: The gut microbiota plays an important role in shaping systemic immune responses. We have developed a WT1 oral cancer vaccine using a recombinant Bifidobacterium Longum ( B. Longum) as a platform for displaying murine WT1 protein ( B. Longum-mWT1). The Wilms’ tumor 1 (WT1) gene, which encodes a zinc finger transcription factor, is reportedly overexpressing in various tumors and one of the most promising tumor-associated antigens for cancer immunotherapy. In order to examine anti-tumor effects of this oral vaccine, we administered it orally into mice inoculated with WT1+-expressing brain tumor which doesn’t respond to existing treatment. Methods: The synthesized murine-WT1 gene (117-439 amino acid residues) was fused to galacto-N-biose/lacto-N-biose I binding protein (GLBP) coding gene. GLBP is a membrane protein on the wild-type B. Longum cell wall, which is used as an anchor to display antigen. The resulting plasmid carrying GLBP-WT1 was introduced into B. Longum by electroporation. We inoculated mouse glioma cell lines (Gl261) subcutaneously into the C57BL/6J. C57BL/6J mice received oral administration of B. Longum-mWT1 every day or subcutaneous administration of WT1126 peptide with montanide adjuvant on days 1, 8, 15, 22, 29, and 36. Results: The tumor volume of the mice treated with B. Longum-mWT1 (n = 5) was significantly smaller than that of the mice given WT1 peptide vaccine (n = 5) ( P < 0.05). The frequency of CD8+/WT1-tetramer+ CTLs was higher in B. Longum-mWT1 and WT1 peptide vaccine groups than in PBS group, and the high frequency was maintained in B. Longum-mWT1 group. In the mouse with B. Longum-mWT1, the frequency CD8+/WT1-tetramer+ CTLs in mesenteric lymph node and spleen was higher than that in Peyer’s patch. The number of invasive CD8+ T cells in brain tumor was higher in the B. Longum-mWT1 group than in the PBS group. B. Longum-mWT1 induced significantly higher in vitro cytotoxicity against Gl261 cells than WT1 peptide. Conclusions: We confirmed that B. Longum-mWT1 can induce strong cellular immunity and the maintenance of this effect. These results suggest that it is a novel oral anti-cancer agent for treating glioblastoma, for which no effective treatment has been developed.