Engineering AFP and GPC3 to create highly immunogenic gene vaccines to prevent carcinogen-induced murine autochthonous hepatocellular carcinoma (VAC12P.1015)

In this study, we investigated whether alpha-fetoprotein (AFP) and glypican 3 (GPC3) could be engineered to create effective vaccines to potently activate CD8 T cells to prevent clinically relevant carcinogen-induced autochthonous hepatocellular carcinoma (HCC) in mice. We found that the approach of epitope-optimization created a highly immunogenic AFP and GPC3 and that immunization with lentivector expressing the epitope-optimized AFP and GPC3, but not wild-type AFP and GPC3, potently activated CD8 T cells. Critically, the activated CD8 T cells not only cross-recognized native AFP peptides, but also recognized and killed tumor cells expressing native AFP and GPC3 protein. Immunization with lentivector expressing optimized AFP, but not native AFP, completely protected mice from tumor challenge and reduced the incidence of carcinogen-induced autochthonous HCC. In addition, prime-boost immunization with the optimized AFP significantly increased the frequency of AFP-specific memory CD8 T cells in the liver that were highly effective against emerging HCC tumor cells, further enhancing the tumor prevention of carcinogen-induced autochthonous HCC. Our data demonstrate that epitope-optimization is required to potently activate AFP- and GPC3- specific CD8 T cells, generating effective antitumor effect to prevent carcinogen-induced HCC in mice. Our study provides a roadmap to develop effective human HCC vaccines that may result in an improved antitumor effect.