GITRL as a genetic adjuvant enhances enterovirus 71 VP1 DNA vaccine immunogenicity

VP1 protein is the immunodominant capsid protein of enterovirus 71 (EV71) which is responsible for large outbreaks of hand, foot and mouth disease. It has been reported that glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) and its ligand (GITRL) are involved in modulating both innate and adaptive immune responses. In this study, a DNA vaccine vector encoding EV71 VP1 gene and mGITRL gene (pIRES/VP1/mGITRL) was constructed. And female Balb/c mice were immunized intramuscularly with the DNA vaccine. Compared with the groups immunized with pIRES, pIRES/VP1, pIRES/mGITRL and PBS, the inoculation of pIRES/VP1/mGITRL induced a higher levels of EV71 VP1-specific antibody and specific antibody-forming cells. However, significantly higher levels of CD4+Th1, Th2 and CD8+IFN-γ+T cells were found in the pIRES/VP1/mGITRL group compared with control groups. Our results demonstrate that a novel DNA vaccine, expressing VP1 and mGITRL, could effectively elicit both humoral and cell-mediated immune responses against EV71 VP1 in mice. Thus, the mGITRL may be used as molecular adjuvant for EV71 DNA vaccine.