Ginsenoside Re as an adjuvant to enhance the immune response to the inactivated rabies virus vaccine in mice.

The inactivated rabies virus vaccine (RV) is a relatively expensive vaccine, prone to failure in some cases. Ginsenoside Re (Re) is a saponin isolated from Panax ginseng, and has an adjuvant property. Here the adjuvant effect of Re to improve the immune response to the RV is evaluated in mice. ICR mice were immunized with saline, 2.50mg/kg Re, 20μl RV, 100μl RV, or 20μl of RV adjuvanted with Re (1.25, 2.50 or 5.00mg/kg). Different time points after boosting, we measured serum antibodies in blood samples and separated splenocytes to detect lymphocyte proliferation and the production of IL-4, IL-10, IL-12, and IFN-γ in vitro. We also compared immunizations containing 20μl RV and 20μl RV adjuvanted with Re (5.00mg/kg) for the expression of CD4(+) and CD8(+) T-cell subsets at different time points. Results indicated that co-administration of Re significantly enhanced serum antibody titers, increased the CD4(+):CD8(+) ratio, and enhanced both proliferation responses and IL-4, IL-10, IL-12 and IFN-γ secretions. Both Th1 and Th2 immune responses were activated. The supplementation of the Re (5.00mg/kg) to 20μl of RV significantly amplified serum antibody responses and Th1/Th2 responses inducing similar protection as did 100μl of RV. This suggests that Re could be used to reduce the dose, and therefore the cost, of the RV to achieve the same effective protection. Re merits further studies for use with vaccines of mixed Th1/Th2 immune responses.