A substantial number of
antigens of Leishmania donovani have been described in the past. However, identifying candidate
antigens is not enough. Appropriate
antigen delivery to induce the right type of immune response against
leishmaniasis (i.e. induction of a strong
antigen-specific Th1 type of immune response) is another crucial component of an effective
vaccine. Therefore, 'cocktail'
vaccines are proposed based on the assumption that such cocktails will show enhanced efficacy. Studies have been carried out on LD31 and LD51
polypeptides from L. donovani promastigotes, which have proven to be potential
vaccine candidates. This study was designed to check the protective efficacy of various cocktails of low molecular weight
antigens alone and along with
saponin as adjuvant. Mice were sacrificed on different post-challenge days for evaluation of parasite load and other immunological parameters. Protective efficacy of different
vaccine formulations was revealed by significant decline in parasite burden and increased DTH Delayed Type Hypersenstivity responses. The antibody response was of
IgG type with elevated
IgG2a and decreased production of
IgG1, whereas
cytokine levels pointed towards the generation of protective Th1 type of immune response. Among all
vaccine formulations, cocktail of 31+51+
saponin was found to be highly immunogenic and imparted maximum protection.