The effects of IL-6 and TNF-α as molecular adjuvants on immune responses to FMDV and maturation of dendritic cells by DNA vaccination

Various approaches have been developed to improve efficacy of DNA vaccination, such as the use of plasmid expressing cytokine as a molecular adjuvant. In this study, we investigated whether co-inoculation of a construct expressing either IL-6 or TNF-α as the molecular adjuvant with FMDV DNA vaccine, pcD-VP1, can increase immune responses. Compared to the group immunized with pcD-VP1 alone, the co-inoculation with either molecular adjuvant induced a higher ratio of IgG2a/IgG1, higher levels of expression of IFN-γ in CD4+ and CD8+ T cells, IL-4 in CD4+ T cells, and in vivo antigen-specific cytotoxic response. Both adjuvants induced maturation of dendritic cells, suggesting a correlation between the initiating innate response and subsequent activating adaptive immune responses. Together, the results demonstrate that IL-6 and TNF-α used as molecular adjuvants can enhance the antigen-specific cell-mediated responses elicited by VP1 DNA vaccine.