Evaluation of a Novel Multi-Epitope Peptide Vaccine Candidate from LACK, LeIF, GP63, SMT Antigens of Leishmania major in BALB/c Mice

Leishmaniasis is one of the major health problems in most countries of the world. Millions of people around the world are at risk for the disease. Given the prevalence of this parasite in Iran and developing countries and the emergence of resistance in some cases to existing drugs, developing an effective vaccine against leishmaniasis is necessary. This research aims to design a multi-epitope vaccine derived from LACK, LeIF, GP63, and SMT antigens of Leishmania major based on the combination of bioinformatics methods. The synthesized construct with 16.86 KDa was cloned and sub-cloned in pEGFP- N1 and pLEXSY-neo2, respectively. They were then transfected in promastigotes of L. tarentolae. After confirmation of expression, immunization was carried out in 8 groups of BALB/c mice (9 mice per group) three times at two-week intervals. Cellular immune responses were assessed before and after the challenge by L. major. Furthermore, at 3rd week post-infection, the survival rate, mean lesion size, and parasite burden were assessed. All vaccinated mice demonstrated partial immunity to higher IFN-γ levels than the control groups (P<0.05). Immunized mice with cytosolic complex (G1) indicated the highest levels of IFN-ɤ and ratio of IFN ɤ/ IL-4, the lowest levels of IL-4 and IL-10 compared to control and the other groups (P≤0.05), and produced a partial Th1 immune response. Mean lesion size and parasite burden of G1 and G5 reduced significantly compared to the other and control groups post-challenge (P<0.05). The outputs of our result could be a hopeful sign in the achievement of practical approaches as multi-epitope vaccines against Leishmania major.