Prophylactic potential of autoclaved Leishmania donovani with BCG against experimental visceral leishmaniasis

Abstract

The prophylactic efficacy of autoclaved Leishmania donovani (ALD) and autoclaved L. major (ALM) – a heterologous vaccine developed against cutaneous leishmaniasis (used as a reference vaccine), along with BCG – was evaluated against L. donovani in hamsters (Mesocricetus auratus). Animals were immunized with triple doses (21 days apart) of either ALD or ALM (1·0 mg) with or without BCG (0·1 mg) and challenged 21 days later with 1×10⁶L. donovani amastigotes intracardially. Animals immunized with ALM+BCG and ALD+BCG yielded 94·3% and 86·1% parasite inhibition respectively in comparison to the BCG only and unvaccinated controls. Fifty and 33·3% of the vaccinated animals (ALM+BCG and ALD+BCG respectively) were completely devoid of parasites when tested on day 45 post-challenge (p.c.) and survived till the experiment was terminated. The mean survival of ALM+BCG and ALD+BCG groups (animals harbouring parasites) was longest (168 and 139 days respectively). No significant increase in anti-leishmanial antibody level (ELISA) was noticed in ALD+BCG and ALM+BCG groups whereas it increased progressively in the rest of the experimental groups. The lymphoproliferative responses to PHA and Con A, of the 2 vaccinated groups were comparable to that of normal controls on day 45 p.c. The study suggests that ALD along with BCG can offer substantial protection against visceral leishmaniasis in hamsters.