THE SYNERGISM OF THE COMBINED GLYCYRRHIZIC ACID AND ALUM LIPOSOME ON IMMUNE RESPONSES AGAINST THE KILLED FORM OF SALMONELLA TYPHIMURIUM

The killed preparation of microorganisms in combination with alum does not generally produce strong cellular immune responses. Glycyrrhizic acid is a triterpenoid saponin with immunomodulating properties. The present study was conducted to investigate the synergism of glycyrrhizic acid (GL) and alum liposome on immune responses against the killed form of Salmonella Typhimurium (HKST).

In this experimental study, male Balb/c mice in 5 groups of 15 were immunized with HKST vaccine alone or in combination with alum, GL or alum-GL combination twice with two weeks’ interval. Fourteen days after the last vaccination, the immune responses against Salmonella Typhimurium and the protective potential of the vaccines were evaluated. Survival rate was monitored by Kaplan-Meier analysis. Other findings were analyzed using one-way analysis of variance and Tukey's post hoc test. A level of P<0.05 was considered significant.

Delayed type hypersensitivity reaction, lymphocyte proliferation, IgG2a antibody titer and the rate of improvement of survival against challenge with live were significantly increased in the group receiving combined adjuvant and HKST compared to other groups. In the group receiving combined adjuvant, the level of IFN-γ significantly increased and IL-4 significantly decreased more profound than other groups.

Alum-GL combination as an adjuvant synergistically increased cellular and humoral immunity after immunization with the HKST vaccine.