Enhanced HER-2/neu-specific antitumor immunity by cotransduction of mouse dendritic cells with two genes encoding HER-2/neu and alpha tumor necrosis factor

The present study uses an in vivo murine tumor model expressing the human HER-2/neu antigen to evaluate the potential vaccine using dendritic cells (DCs) infected with adenovirus AdVHER-2. We first investigated whether infected DCs (DCHER-2) engineered to express HER-2/neu could induce HER-2/neu-specific immune responses. Our data showed that (i) AdVHER2-infected DCHER-2 expressed HER-2/neu by Western blot and flow cytometric analysis, and (ii) vaccination of mice with DCHER-2 induced HER-2/neu-specific cytotoxic T-lymphocyte (CTL) responses, but protected only 25% of vaccinated mice from challenge of 3×105 MCA26/HER-2 tumor cells. Further, to enhance the efficacy of DCHER-2 vaccine, we coinfected DCs with both AdVHER-2 and AdVTNF-α. The infected DCs (DCHER-2/TNF-α) displayed the expression of both HER-2/neu and TNF-α by flow cytometric and ELISA analysis. We next investigated whether DCHER-2/TNF-α could induce stronger HER-2/neu-specific immune responses. We found that DCHER-2/TNF-α displayed up-regulation of immunologically important CD40, CD86, and ICAM-I molecules compared with DCHER-2, indicating that the former ones are more mature forms of DCs. Vaccination of DCHER-2/TNF-α induced stronger allogeneic T-cell proliferation and 36% enhanced HER-2/neu-specific T-cell responses in vitro than DCHER-2 cells. More importantly, it stimulated the significant anti–HER-2/neu immunity in vivo, which protected 8/8 mice from challenge of 3×105 MCA26/HER-2 tumor cells. Therefore, DCs genetically engineered to express both the tumor antigen and cytokines such as TNF-α as an immunoadjuvant are likely to represent a new direction in DC vaccine of cancer.