Chitosan Nanoparticles Loaded with Whole and Soluble Leishmania Antigens, and Evaluation of Their Immunogenecity in a Mouse Model of Leishmaniasis

Background: Although there have been numerous attempts to develop vaccines for Leishmaniasis, no vaccine can be found against Leishmania in routine use for an effective global vaccination. It seems that one of the reasons for the low efficacy of such vaccines is the lack of a suitable adjuvant. Objective: To evaluate the effects of chitosan nanoparticles containing whole Leishmania lysate antigen (WLL) and soluble leishmania antigens (SLA), a first generation Leishmania vaccine, on the type of immune response generated in BALB/c in a murine model of leishmaniasis. Methods: The optimum coating ratio between the polymer and antigens was determined according to their physico-chemical properties such as particle size and zeta potential. Chitosan nanoparticles were loaded with antigens via ionic gelation method. BALB/c mice were immunized subcutaneously three times with various nanoparticulate and free antigens with 2-week intervals. Results: There was no significant (P > 0.05) difference concerning the footpad thickness of mice immunized with nanoparticulate formulations containing either SLA or WLL during the experiment period; these formulations induced a strong mixed Th1/Th2 type immune response characterized by the production of IFN-γ and IL-4, and high levels of IgG2a IgG1 anti-Leishmania antibody. Conclusion: Nanoparticulate formulations (CHT: SLA and CHT: WLL) are not suitable candidates for preferential induction of a pure Th1-type immune response and immunization against Leishmania infection. However, it might be a good strategy in other infectious diseases where a mixed Th1/Th2 immune response is required.