Role of IL-21 in host pathogenesis in experimental visceral leishmaniasis.

Visceral leishmaniasis (VL) is a major global health problem but still remains one of the neglected tropical diseases. Currently available chemotherapeutics are associated with severe toxicity and increased drug resistance. There is a need to explore for novel therapeutic strategies that could modulate host immune responses or work in synergy with chemotherapy of VL. Therefore, understanding the host immunological changes that play a vital role in disease pathology is a prerequisite for designing any interventions. We have investigated the role of IL-21 during the course of Leishmania donovani infection and after drug treatment. BALB/c mice were used to investigate the mRNA levels of IL-21 during active Leishmania donovani infection and after treatment using real time polymerase chain reaction (RT-PCR). Mice were divided in four groups i.e. Control (Group A), Infected (Group B), Uninfected treated (Group C) and Infected treated (Group D). Animals of Group C and D were treated with Amphotericin B. IL-21 mRNA levels in the spleen were estimated on days 1, 3, 7, 14, 17, 21, 28, 35, 45 and 60 post infection and also during course of treatment. We found that IL-21 mRNA levels was significantly up-regulated in the infected group with a fourfold increase at D60 p.i. (p < 0.001) and it was decreased significantly after the treatment. Our results suggest that IL-21 mRNA is associated with pathogenesis of Leishmania donovani infection and that therapeutics designed to suppress IL-21 could provide promising antileishmanial activity.