Liposomes containing the imiquimod adjuvant as a vaccine in the cutaneous leishmaniasis model

Abstract

Objective(s): Attempts to produce vaccines for leishmaniasis need adjuvants to trigger the kind of immune reaction required for protection. In this study, we examined the properties of the TLR7 agonist imiquimod, a vaccine adjuvant, making use of a live model of infection where the immune reactions could be identified prior to and following the challenge of infection. Materials and Methods: The liposomes of EPC containing the imiquimod adjuvant were prepared and characterized for protein concentration, surface charge, and particle size. Vaccination was done using the soluble Leishmania antigen (SLA) as a first-generation vaccine model in the liposomal state to vaccinate BALB/c mice against the challenge of leishmania major. BALB/c mice were vaccinated subcutaneously, three times at a two-week interval. Parasite burden, footpad swelling, IgG isotype, as well as the level of IL-4 and IFN-γ were assessed as the protection criteria.Results: The group of mice vaccinated by Lip+Imiquimod+SLA demonstrated a lower amount of footpad swelling and parasite burden than the buffer group. In addition, the highest level of IFN-γ and the lowest level of IL-4 production was noticed in the splenocytes of the mice vaccinated with the formulation of Lip+Imiquimod+SLA. Conclusion: These results imply that imiquimod added to the formulation of liposomes is able to modulate the immune reaction of the BALB/c mice vaccinated preferably to a Th1 reaction rather than a Th2 reaction which can also lead to partial protection against the challenge of Leishmania.