[Immune response evaluation against autoclaved leishmania major ncapsulated in liposome with different Tm in murine model]

ABSTRACT

Leishmaniasis is a parasitic disease which is caused by different species of Leishmania. Protozoa of the Leishmania species cause leishmaniasis. The protective immunity against leishmaniasis is the cell-mediated immunity [CMI]. Autoclaved Leishmania major [ALM] has been used as vaccine in clinical trial; however, its efficacy has been low. 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 evaluate the immune response of ALM entrapped in liposome with different phase transition temperature [Tm] in BALB/c mice. Liposomes containing ALM were prepared as dehydration-rehydration vesicles [DRV] and composed of dipalmitoylphosphatidylcholine [DPPC, Tm 41°C] and cholesterol or phosphatidylcholine [PC, Tm -10°C] and cholesterol in a molar ratio of 72 DRV-DPPC-Chol- ALM [180 microg], DRV-PC-Chol-ALM [180 microg], ALM alone [180 microg], PBS, and a control empty liposome were injected separately subcutaneously [SC] in female BALB/c mice [10 per group], 3 times in three weeks interval. The mice were tested for DTH with freeze-thawed L. major promastigotes [1.5 × 10[7]] 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 after 24, 48 and 72 hours. Blood samples were collected before second and third vaccination and also before DTH test to titrate the anti-Leishmania antibodies [IgG total, IgG1 and IgG2a] by ELISA method. The sizes of liposome were between 0.5-3 microm. Percent encapsulation of ALM in DRV-DPPC- Chol-ALM and DRV-PC-Chol-ALM was 46 and 43 respectively. The results of DTH showed that footpad swelling in DRV-DPPC-Chol-ALM and DRV-PC-Chol-ALM is significantly more than control groups. The results of ELISA showed that the titer of IgG total in PBS, control empty liposomes and ALM alone is low and it is significantly less than DRV-DPPC- Chol-ALM and DRV-PC-Chol-ALM. There were no differences in the titer of IgG1 in the different groups; however, the titer of IgG2a was significantly higher in DRV-DPPC-Chol- ALM compared to DRV-PC-Chol-ALM and control groups. The results indicated that liposome prepared by higher Tm phospholipid seems to be a suitable immunoadjuvant for ALM in to improve the CMI