bradyzoite stages induce suicidal- and rapid vital-NETosis.
Ershun Zhou, Liliana M R Silva, Iván Conejeros, Zahady D Velásquez, Manuela Hirz, Ulrich Gärtner, Philippe Jacquiet, Anja Taubert, Carlos Hermosilla
Author Information
Ershun Zhou: Institute of Parasitology, Justus Liebig University Giessen, Giessen, Germany. ORCID
Liliana M R Silva: Institute of Parasitology, Justus Liebig University Giessen, Giessen, Germany.
Iván Conejeros: Institute of Parasitology, Justus Liebig University Giessen, Giessen, Germany.
Zahady D Velásquez: Institute of Parasitology, Justus Liebig University Giessen, Giessen, Germany.
Manuela Hirz: Institute of Veterinary Pathology, Justus Liebig University Giessen, Giessen, Germany.
Ulrich Gärtner: Institute of Cell Biology and Anatomy, Justus Liebig University Giessen, Germany.
Philippe Jacquiet: Département Élevage et Produits-Santé Publique Vétérinaire, Laboratoire de Parasitologie et Maladies Parasitaires, École Nationale Vétérinaire de Toulouse (ENVT), Université de Toulouse, Toulouse, France.
Anja Taubert: Institute of Parasitology, Justus Liebig University Giessen, Giessen, Germany.
Carlos Hermosilla: Institute of Parasitology, Justus Liebig University Giessen, Giessen, Germany.
Besnoitia besnoiti is an obligate intracellular apicomplexan protozoan parasite, which causes bovine besnoitiosis. Recently increased emergence within Europe was responsible for significant economic losses in the cattle industry due to the significant reduction of productivity. However, still limited knowledge exists on interactions between B. besnoiti and host innate immune system. Here, B. besnoiti bradyzoites were successfully isolated from tissue cysts located in skin biopsies of a naturally infected animal, and we aimed to investigate for the first time reactions of polymorphonuclear neutrophils (PMN) exposed to these vital bradyzoites. Freshly isolated bovine PMN were confronted to B. besnoiti bradyzoites. Scanning electron microscopy (s.e.m.)- and immunofluorescence microscopy-analyses demonstrated fine extracellular networks released by exposed bovine PMN resembling suicidal NETosis. Classical NETosis components were confirmed via co-localization of extracellular DNA decorated with histone 3 (H3) and neutrophil elastase (NE). Live cell imaging by 3D holotomographic microscopy (Nanolive®) unveiled rapid vital NETosis against this parasite. A significant increase of autophagosomes visualized by specific-LC3B antibodies and confocal microscopy was observed in B. besnoiti-stimulated bovine PMN when compared to non-stimulated group. As such, a significant positive correlation (r = 0.37; P = 0.042) was found between B. besnoiti-triggered suicidal NETosis and autophagy. These findings suggest that vital- as well as suicidal-NETosis might play a role in early innate host defence mechanisms against released B. besnoiti bradyzoites from tissue cysts, and possibly hampering further parasitic replication. Our data generate first hints on autophagy being associated with B. besnoiti bradyzoite-induced suicidal NETosis and highlighting for first time occurrence of parasite-mediated vital NETosis.
