Ascaridia galli Excretory-Secretory Proteins Suppress Intestinal Epithelial Proliferation and Trigger TLR4-Mediated Inflammation.

Ascaridia galli is the most prevalent nematode parasite in the intestinal tract of chickens. However, the direct impact of A. galli excretory-secretory proteins (ESPs) on intestinal epithelial cells (IECs) function and the underlying mechanisms remain elusive. To address this, A. galli ESPs were isolated for investigation of their tissue localization and effects on IECs. Immunohistochemical analysis localized ESPs to the parasite's cuticle and internal tissues. LC-MS/MS identification revealed 26 putative ESPs that bind to chicken IECs, including actin, heat shock proteins, elongation factor-1α, and fructose-bisphosphate aldolase. Functionally, ESPs exposure suppressed IECs proliferation through disruption of cellular metabolism, signal transduction, and cell cycle progression. Furthermore, ESPs induced a pro-inflammatory response, characterized by increased secretion of TNF-α, IL-6, and nitric oxide. Mechanistically, this response was accompanied by increased TLR4 expression and suppression of IL-10. This study suggests a dual mechanism whereby A. galli ESPs subvert intestinal barrier function by simultaneously impairing epithelial repair and driving maladaptive inflammation, providing profound insights into the pathogenesis of avian ascariasis.