A novel ligand for chicken Toll-like receptor 5 from Eimeria maxima: dihydrolipoyl dehydrogenase drives M2-like polarization and Treg-like responses.
Source: PubMed, NCBI / U.S. National Library of Medicine
Avian coccidiosis is a major parasitic disease that poses a significant threat to the poultry industry. Elucidating the regulatory mechanisms of key molecules involved in the interplay between Eimeria and the host immune system is of great importance for the development of novel control strategies. Toll-like receptor 5 (TLR5) is a critical pattern recognition receptor in host innate immunity; however, research on its ligands has primarily focused on bacterial-derived molecules, and Eimeria-derived ligands along with their regulatory mechanisms remain largely uncharacterized. Using immunoprecipitation coupled with proteomics analysis, we identified a novel chicken TLR5 (chTLR5) ligand, E. maxima dihydrolipoyl dehydrogenase (EmDLD). In an in vitro macrophage model, recombinant EmDLD (rEmDLD) polarized chicken primary bone marrow-derived macrophages toward an M2-like phenotype. This polarization was characterized by the upregulation of TGFB1 and CD206, alongside the downregulation of TNFA, IL1B, and IL6, without affecting the production of nitric oxide (NO) or reactive oxygen species (ROS). Unexpectedly, in the chicken macrophage cell line HD11, rEmDLD activated the canonical NF-κB and MAPK signaling pathways. Furthermore, rEmDLD promoted maturation of primary bone marrow-derived dendritic cells in vitro, which enhanced T-cell proliferation and increased the proportion of CD4CD25regulatory T cell‑like cells (Treg‑like cells). In vivo experiments demonstrated
Abstract
Avian coccidiosis is a major parasitic disease that poses a significant threat to the poultry industry. Elucidating the regulatory mechanisms of key molecules involved in the interplay between Eimeria and the host immune system is of great importance for the development of novel control strategies. Toll-like receptor 5 (TLR5) is a critical pattern recognition receptor in host innate immunity; however, research on its ligands has primarily focused on bacterial-derived molecules, and Eimeria-derived ligands along with their regulatory mechanisms remain largely uncharacterized. Using immunoprecipitation coupled with proteomics analysis, we identified a novel chicken TLR5 (chTLR5) ligand, E. maxima dihydrolipoyl dehydrogenase (EmDLD). In an in vitro macrophage model, recombinant EmDLD (rEmDLD) polarized chicken primary bone marrow-derived macrophages toward an M2-like phenotype. This polarization was characterized by the upregulation of TGFB1 and CD206, alongside the downregulation of TNFA, IL1B, and IL6, without affecting the production of nitric oxide (NO) or reactive oxygen species (ROS). Unexpectedly, in the chicken macrophage cell line HD11, rEmDLD activated the canonical NF-κB and MAPK signaling pathways. Furthermore, rEmDLD promoted maturation of primary bone marrow-derived dendritic cells in vitro, which enhanced T-cell proliferation and increased the proportion of CD4CD25regulatory T cell‑like cells (Treg‑like cells). In vivo experiments demonstrated that immunization with rEmDLD induced the production of specific IgY antibodies in chickens. It moderately alleviated body weight loss following E. maxima infection and reduced oocyst shedding in the jejunum. Our results identify EmDLD as a novel ligand of chTLR5 that induces M2-like macrophage polarization and the generation of Treg-like cells. This study reveals for the first time that Eimeria may modulate host immune responses toward an immunoregulatory state through the EmDLD-TLR5 axis, offering important insights into the mechanisms of immune evasion by Eimeria and the development of novel anti-coccidial intervention strategies.