Immune response evaluation against leishmaniasis using liposomes containing rLmSTI1 in murine model

ABSTRACT

Leishmaniasis is a parasitic disease spread by the bite of infected sand flies. Protozoa of the Leishmania species cause leishmaniasis. The protective immunity against leishmaniasis is the cell-mediated immunity [CMI]. LmSTI1 is a candidate for the development of vaccine against cutaneous leishmaniasis [CL]. Liposomes are microscopic vesicles consisting of phospholipid bilayers which enclose aqueous compartments and are used as an immunoadjuvant. The aim of this study was to formulate liposome preparations containing recombinant rLmSTI1 to induce Th1 response in BALB/c mice against infection with L. major. Liposomes containing rLmSTI1 were prepared as dehydration-rehydration vesicles [DRV] and composed of distearoylphosphatidylcholine [DSPC] and cholesterol [CHOL] in a molar ratio of 21 [DSPC/CHOL-rLmSTI1]. The average size of liposome formulations was 1.1micro m checked by light microscope and particle size analyzer. DSPC/CHOL-rLmSTI1 [2micro g]; soluble rLmSTI1 [2micro g]; PBS, and a control empty liposome were injected separately subcutaneously [SC] in female BALB/c mice [10 per group], 3 times in three week intervals. The mice were challenged with L. major promastigotes [1.5 X 10[6]] SC to the left footpad and PBS to the right footpad for control at 3 weeks after the last booster. The footpad swellings were measured weekly for 12 weeks. Blood samples were collected on the day before and 12 weeks after challenge to titrate the anti-Leishmania antibodies [IgG total, IgG1 and IgG2a] by ELISA method. The parasite burden in spleen was determined at 15weeks after challenge. The results showed that in the group that received DSPC/CHOL-rLmSTI1, footpad thickness was significantly less; IgG2a titer was higher with very few parasites in the spleen compared to the other groups. The results indicated that encapsulation of rLmSTI1 in liposome seems to be a suitable tool to improve the CMI and rate of protection in murine model of leishmaniasis