# Reversal of filarial serpin Wb123-urokinase plasminogen activator receptor mediated alternative macrophage activation by monoclonal antibody

## TL;DR

This study shows how a protein from a parasitic worm causes immune cells to avoid strong inflammation, helping the worm survive, and suggests targeting this protein could help treat the infection.

## Contribution

The study identifies Wb123 as a key filarial serpin that induces alternative macrophage activation via uPAR and demonstrates its reversal using a monoclonal antibody.

## Key findings

- rWb123 induces alternative macrophage activation marked by CD163, arginase-1, IL-6, and pSTAT3 upregulation.
- rWb123 interacts with uPAR to drive alternative activation and suppresses classical activation markers like CD86 and NO.
- Blocking Wb123 with a monoclonal antibody or uPAR rescues proinflammatory responses to LPS-IFN-γ.

## Abstract

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.

Filarial nematodes are thread-like parasitic worms that causes major tropical diseases such as lymphatic filariasis and onchocerciasis. Macrophages of filariae infected individuals exhibit an alternatively activated phenotype. While previous studies have demonstrated that infective L3 larva infection and Brugia malayi antigen extracts can induce the alternative macrophage activation, the molecular mechanisms governing this process remains incompletely understood. In this study, we investigated the role of filarial serpin in modulating macrophage activation. We showed that recombinant Wb123 incubation induces the alternative macrophage activation through urokinase plasminogen activator receptor (uPAR) pathway. We also showed that pre-polarization of macrophages toward classical activation did not prevent subsequent Wb123-driven alternative activation. Additionally, neutralization of Wb123 with a monoclonal antibody reversed the alternative activation phenotype. Thus, these findings offer new insights into the immunomodulatory strategies employed by filarial nematodes and highlights the role of filarial serpins. They also open promising avenues for the development of therapeutic interventions targeting uPAR and serpins.