Codelivery of DNA vaccination encoding LeIF gene and IL-12 increases protection against Leishmania major infection in BALB/c mice.

Previous studies have shown that Leishmania elongation initiation factor (LeIF) antigen causes a partial immunity against leishmaniasis. The antigen develops type I immunity by overexpression of inflammatory cytokines such as interleukin-12 (IL-12), IFN-γ and TNF-α. Therefore, We evaluated immune responses induced by the LeIF gene against Leishmania major infection. Immunization with LeIF gene alone or with IL-12 induced Th1 response and produced higher IFN-γ and lower IL-4 levels by splenocytes than control groups (P < 0·05) and also ratios of IFN-γ/IL-4 were 11·68 to 18·53 times more in immunized groups than control groups after challenge. In addition, analysis of humoral immune response revealed that immunized mice had more IgG2a levels than both control groups (P < 0·05). On the other hand, lesion size was less for immunized animals than control groups from 4th week after challenge (P < 0·05). The percentage reduction in lesion size was 29·30% for LeIF and 51·98% for LeIF + IL-12 than PBS at 12th week post-infection. Spleen parasite burden decreased in all immunized groups in comparison with control groups (P < 0·05). The results indicated that LeIF gene induced partial immunity against L. major infection in BALB/c mice. However, LeIF plus IL-12 group showed more potent immunity with smaller lesions than other groups.