Coimmunization with IFN-gamma or IL-2, but not IL-13 or IL-4 cDNA can enhance Th1-type DNA vaccine-induced immune responses in vivo.

As we explore the potential improvements to the current DNA vaccine strategies, it may be desirable to investigate methods to improve the level of resulting immune responses. One strategy is the use of cytokine cDNA as molecular adjuvants for DNA-based vaccines. Codelivery of these molecular adjuvants consisting of expression plasmid encoding for cytokines with DNA vaccine constructs is an effective method to modulate the magnitude and direction (humoral or cellular) of the immune responses. We have previously reported on the immunomodulatory effects of codelivering cDNA for interleukin-2 (IL-2) and IL-4 as molecular adjuvants for DNA-based vaccines. In this report, we extend these finding and compare the immunomodulatory effects of IL-2 and IL-4 with those of cDNA for prototypical Thl-type cytokine interferon-y (IFN-gamma) and Th2-type cytokine IL-13. We observed that distinct antigen-specific immune modulation can be achieved by the coinjection of IFN-gamma or IL-13 genes with DNA immunogen cassettes. We observed that IFN-gamma is a strong driver of Thl immune responses. Furthermore, in contrast to previous reports on their similarities in biologic activities, IL-13 and IL-4 cDNA coimmunizations modulated vaccine-induced immune responses differently in this model. Overall, these results further support the potential utility of this strategy as an important tool for the development of vaccines and immune therapies.