Development of new generation
vaccines requires adjuvants to elicit the type and intensity of immune response needed for protection.
Liposomes have been shown to be an effective adjuvant formulation. In this study, the role of
liposome bilayer composition with different phase transition temperature (T(c)) to induce a T helper 1 (Th1) type of immune response and protection against
leishmaniasis in BALB/c mice was assessed.
Liposome formulations with different bilayer compositions consisting of egg
phosphatidylcholine (
EPC, T(c)<0 degrees C),
dipalmitoylphosphatidylcholine (DPPC, T(c) 41 degrees C), or
distearoylphosphatidylcholine (DSPC, T(c) 54 degrees C) were prepared. All
liposomes were contained rgp63 as a recombinant
antigen and used to immunize mice subcutaneously 3 times in 3-week intervals. Evaluation of lesion development and splenic parasite burden after challenge with L. major, evaluation of Th1
cytokine (IFN-gamma) and Th2
cytokine (IL-4), and titration of
IgG isotypes were carried out to assess the type of generated immune response and extent of protection. The results indicated the generated immune response in mice was influenced by the bilayer composition of
liposomes, so that mice immunized with
liposomes consisting of
EPC induced a Th2 type of immune response while
liposome consisting of DPPC or DSPC induced Th1 type of immune response. It seems that
liposomes prepared with higher Tm
phospholipids are suitable formulation to induce Th1 type of immune response and protection, and so might be used for further investigations to develop an effective
vaccine against
leishmaniasis.