Induction of protection against leishmaniasis in susceptible BALB/c mice using simple DOTAP cationic nanoliposomes containing soluble Leishmania antigen (SLA)

•DOTAP nanoliposomes containing 1mg/ml of SLA induce an efficient protection against leishmaniasis.•DOTAP nanoliposomes containing 1mg/ml of SLA reduce lesion size and elicit TH1 immune response.•Other concentrations of SLA in DOTAP nanoliposomes do not show effective responses.•Free SLA has minimal effect in eliciting TH1 response. A suitable adjuvant and delivery system are needed to develop an effective vaccine against leishmaniasis. To induce a Th1 type of response and protection in BALB/c mice against Leishmania major infection, 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) nanoliposomes bearing an intrinsic adjuvanticity, were used as an antigen delivery system and immunoadjuvant for soluble Leishmania antigens (SLA). DOTAP liposomes containing different concentrations of SLA were prepared by using lipid film method followed by sonication. The prepared vesicles showed a diameter of about 100nm, a positive zeta potential and approximately 70% encapsulation efficiency of SLA. BALB/c mice were immunized subcutaneously (SC), three times in a 3-week interval with different concentrations of liposomal SLA (12.5, 25, and 50μg of SLA/50μl/mice), free SLA and as well as free liposome. The group of mice received 50μg of SLA in DOTAP-nanoliposomes showed a significantly (p