Cationic Immune Stimulating Complexes Containing Soluble Leishmania Antigens: Preparation, Characterization and in Vivo Immune Response Evaluation.

BACKGROUND Cationic immune stimulating complexes (PLUSCOMs) are particulate antigen delivery systems. PLUSCOMs consist of cationic immunostimulatory complexes (ISCOMs) derivatives and are able to elicit in vivo T cell responses against an antigen. OBJECTIVE To evaluate the effects of PLUSCOMs containing Leishmania major antigens (SLA) on the type of immune response generated in the murine model of leishmaniasis. METHODS PLUSCOMs consisting of 1, 2-dioleoyl-3-trimethylammonium-propane (DOTAP) were used as antigen delivery system/immunoadjuvants for soluble SLA. BALB/c mice were immunized subcutaneously, three times in 2-week intervals. Footpads swellings at the site of challenge and parasite loads were assessed as a measure of protection. The immune responses were also evaluated by determination of IgG subclasses and the level of IFN-γ and IL-4 in cultured splenocytes. RESULTS There was no significant difference (p<0.05) between the sizes of lesions in mice immunized with different formulations. Also, there was no significant difference in the number of parasites in the footpad or spleen of all groups compared with the control group. The highest level of IFN-γ secretion was observed in the splenocytes of mice immunized with PLUSCOM/SLA (p<0.001) and lower amounts of IL-4 was observed in PLUSCOM group (p<0.001) as compared to negative control. CONCLUSION Our results indicated that SLA in different formulations generated an immune response with mixed Th1/Th2 response that was not protective enough despite the activation of CD4+ T cells with secreting IFN-γ in groups which received PLUSCOM with antigen.