Immunomodulatory effect of antigenic fractions of a recent clinical isolate of L. donovani on monocytic cell lines

Nitric oxide (NO) and cytokines are important mediators of the immune response to Leishmania. We have recently reported that following SDS-PAGE separation and transfer of whole L. donovani antigen (strain 2001, a recent clinical isolate from Bihar) into 11 fractions (named F1 to F11; MW range 139-24.2 Kd), only the high molecular weight (MW) fractions (F1 to F4; MW range 134-64.2 Kd) had immunostimulatory activity when tested in leishmania exposed immune individuals. The F1 to F11 fractions were able to induce significant proliferation of peripheral blood mononuclear cells (PBMCs) of leishmania exposed immune individuals and production of variable amounts of IFN-γ IL-12p40 and IL-10. The present study was undertaken to evaluate the effect of L. donovani promastigotes whole antigen extract (WE) and F1 to F11 fractions on NO induction and production of cytokines IL-12p40, IL-10 and TNF-α by mouse and human macrophage cell lines, respectively. NO production was determined by using Griess reagent and cytokines were measured by ELISA. Antigenic fractions and WE stimulated impressive production of NO and cytokines IL-12, IL-10 and TNF-α; F1 to F4 fractions induced higher levels of NO and monocyte derived cytokines IL-10, TNF-α, IL-12 than fractions F5 to F11, although the difference did not reach statistical significance. The high molecular weight antigenic fractions need to be evaluated in greater depth for their possible role as immunomodulatory agents.