Flowcytometry strategies for ROS expression.

Potent inflammatory responses from host-parasite interactions in lymphatic filariasis are driven by macrophage polarization, which critically determines parasite survival or clearance. Evidence suggests that filarial parasite promote alternative macrophage polarization, facilitating immune evasion and persistent infection. However, the precise molecular mechanisms underlying filaria-induced alternative macrophage activation remain to be fully elucidated. Recently, serine protease inhibitors (serpins) have been implicated in alternative immune activation. Building on this insight, we explored and identified putative filarial serpins to be highly expressed in the infective L3 larval stage using in-silico analysis approach. Among all, Wb123, a serpin of Wuchereria bancrofti, the most predominantly found filarial worm, was cloned and purified to establish its role in alternative activation. We observed elevated markers of alternative activation; namely CD163, arginase-1, IL-6 and pSTAT3 expression, following rWb123 treatment. Furthermore, our results also indicated that rWb123 interacts with urokinase plasminogen activator receptor (uPAR) to activate the alternative activation pathway. Interestingly, rWb123 treatment attenuated the classical macrophage activation induced by lipopolysaccharide (LPS) and interferon-gamma (IFN-γ) as evident from muted CD86, nitric oxide (NO) and reactive oxygen species (ROS) expression. Notably, use of monoclonal antibody (MAbG8) to rWb123 or blocking uPAR impedes the rWb123-induced alternative activation and rescues the proinflammatory response to LPS-IFN-γ. These data confirmed that, uPAR dependent alternative activation by Wb123 enables filarial parasites to evade a strong pro-inflammatory immune response. Thus, targeting filarial serpins or uPAR could be potential therapeutics to re-establish immune response and eliminate filarial parasite from host.