[Adjuvant effect of plasmid vector-expressed OX40L on candidate DNA vaccine against type B heptatitis]

To improve the immune response to HBsAg DNA vaccine and clear HBV, we investigated co-stimulatory molecule OX40L as adjuvant effect on the humoral and cellular immune responses to HBV DNA vaccine by immunizing mice with HBV DNA vaccine plus OX40L.

We immunized the C57BL/6 mice with pcDS2 alone, or with OX40L and candidate DNA vaccine against HBV (pcDS2) together by intramuscular injection. The immunization was performed on week 0, 2, 4. The concentration of the anti-HBs (IgG) and isotypes (IgG1, IgG2a), the stimulated index of T lymphocyte proliferation, and the expression of IL-4 and IFN-gamma in CD4+ T cell and IFN-gamma in CD8+ T cell, specific in vivo cytotoxic T lymphocyte (CTL) activity were detected at week 6.

The concentration of the anti-HBs IgG induced by pcDS2 plus OX40L groups was much higher than that induce by pcDS2 alone, and the levels of IgG isotype of IgG2a were generally higher than IgG1 in all groups of mice immunized with different plasmids. Compared to mice immunized with pcDS2 alone, the pcDS2 plus OX40L group increased the stimulated index (SI) of T cell proliferation and elicited a higher level of IFN-gamma and IL-4 in CD4+ T cells and a higher level of IFN-gamma in CD8+ T cells. In all groups, OX40L plus pcDS2 induced significantly robust in vivo CTL response.

The co-immunization of OX40L and HBV DNA vaccine can enhance the humoral and cellular immune responses, especially CTL activity.