Abstract:
Visceral leishmaniasis (VL), caused by the intracellular parasite Leishmania donovani, L. chagasi and L. infantum is
characterized by defective cell-mediated immunity (CMI) and is usually fatal if not treated properly. An estimated 350 million
people worldwide are at risk of acquiring infection with Leishmania parasites with approximately 500,000 cases of VL being
reported each year. In the absence of an efficient and cost-effective antileishmanial drug, development of an appropriate
long-lasting vaccine against VL is the need of the day. In VL, the development of a CMI, capable of mounting Th1-type of immune responses, play an important role as it correlate with recovery from and resistance to disease. Resolution of
infection results in lifelong immunity against the disease which indicates towards the feasibility of a vaccine against the
disease. Most of the vaccination studies in Leishmaniasis have been focused on promastigote- an infective stage of parasite
with less exploration of pathogenic amastigote form, due to the cumbersome process of its purified isolation. In the present study, we have isolated and purified splenic amastigotes of L. donovani, following the traditional protocol with slight
modification. These were fractionated into five membranous and soluble subfractions each i.e MAF1-5 and SAF1-5 and were subjected for evaluation of their ability to induce cellular responses. Out of five sub-fractions from each of membrane and
soluble, only four viz. MAF2, MAF3, SAF2 and SAF3 were observed to stimulate remarkable lymphoproliferative, IFN-c, IL-12
responses and Nitric Oxide production, in Leishmania-infected cured/exposed patients and hamsters. Results suggest the
presence of Th-1 type immunostimulatory molecules in these sub-fractions which may further be exploited for developing a
successful subunit vaccine from the less explored pathogenic stage against VL.
