Effect of interleukin-22 on immunogenicity of DNA vaccine encoding TSA gene of Leishmania major in BALB/c mice

Background and Previous Research shows the use of plasmids containing genes TSA to be useful as vaccines for Leishmania major. Recently, the role of interleukin-22 (IL-22) in tissue repair has been demonstrated. In this research, the effect of IL-22 on encoding TSA gene of Leishmania major in BALB/c mice was assessed. pcDNA3 plasmid containing the gene encoding TSA protein (pcTSA) of Leishmania major, along with the cytokine IL-22 was used. 60 BALB/c mice were divided to 4 groups of 15. Control groups received pcDNA3 and PBS and a group was vaccinated intramuscularly with the TSA gene containing plasmid. Fourth group received plasmid containing the gene for the TSA and IL-22 protein. IL-4 and interferon gamma (IFN-γ) levels (MTT test) were used to evaluate the cellular immunity and IgG2a, IgG1 and Total IgG levels [enzyme-linked immunosorbent assay (ELISA) method] to evaluate the humoral immunity. Measuring the diameter of the lesions and the age and weight of the mice was performed. The simultaneous use of plasmid containing the gene encoding protein TSA and IL-22 significantly increased the mean level of IFN-γ and reduced the mean level of IL-4 compared to the other groups. While the mortality rate at 27th week after intervention was 100 % in the control group, the surveillance rates of pcTSA and pcTSA + IL-22 groups were 80%. pcTSA + IL-22 group had the highest weight in 30th week. pcTSA + IL-22 group had significantly smaller lesions compared to control and pcTSA groups. Results show the efficacy of pcTSA + IL-22 in improving the vaccination of cutaneous leishmaniasis.