The coagulation system helps control infection caused by the ciliate parasite Philasterides dicentrarchi in the turbot Scophthalmus maximus (L.)

Abstract

Many studies have shown that coagulation systems play an important role in the defence against pathogens in invertebrates and vertebrates. In vertebrates, particularly in mammals, it has been established that the coagulation system participates in the entrapment of pathogens and activation of the early immune response. However, functional studies investigating the importance of the fish coagulation system in host defence against pathogens are scarce. In the present study, injection of turbot (Scopthalamus maximus) with the pathogenic ciliate Philasterides dicentrarchi led to the formation of macroscopic intraperitoneal clots in the fish. The clots contained abundant, immobilized ciliates, many of which were lysed. We demonstrated that the plasma clots immobilize and kill the ciliates in vitro. To test the importance of plasma clotting in ciliate killing, we inhibited the process by adding a tetrapeptide known to inhibit fibrinogen/thrombin clotting in mammals. Plasma tended to kill P. dicentrarchi slightly faster when clotting was inhibited by the tetrapeptide, although the total mortality of ciliates was similar. We also found that kaolin, a particulate activator of the intrinsic pathway in mammals, accelerates plasma clotting in turbot. In addition, PMA-stimulated neutrophils, living ciliates and several ciliate components such as cilia, proteases and DNA also displayed procoagulant activity in vitro. Injection of fish with the ciliates generated the massive release of neutrophils to the peritoneal cavity, with formation of large aggregates in those fish with live ciliates in the peritoneum. We observed, by SEM, numerous fibrin-like fibres in the peritoneal exudate, many of which were associated with peritoneal leukocytes and ciliates. Expression of the CD18/CD11b gene, an integrin associated with cell adhesion and the induction of fibrin formation, was upregulated in the peritoneal leukocytes. In conclusion, the findings of the present study show that P. dicentrarchi induces the formation of plasma clots and that the fish coagulation system may play an important role in immobilizing and killing this parasite.

Interactions between the Parasite Philasterides dicentrarchi and the Immune System of the Turbot Scophthalmus maximus. A Transcriptomic Analysis

“…This chemokine also induces chemotaxis of neutrophils and, to a lesser extent, lymphocytes and macrophages in turbot [ 24 , 67 ]. These results support those demonstrating intense migration of neutrophils to the turbot peritoneal cavity during P. dicentrarchi infection [ 21 ]. Several interleukins and their receptors, as well as several members of the TNF family and their receptors, were also strongly UR in turbot peritoneal cells, particularly the proinflammatory cytokines IL1b and TNFa.…”

“…The present study shows that intraperitoneal injection of turbot with P. dicentrarchi induced an acute inflammatory response and enhanced the expression of genes involved in inflammatory pathways, inflammatory cytokines or genes coding for enzymes involved in the synthesis of prostaglandins and leukotrienes. Recruitment of inflammatory cells, which is part of the inflammatory response [ 51 ], was not evaluated in the present study but has been demonstrated in previous studies [ 21 ]. Recognition of the pathogen by pattern recognition receptors is an important event in the inflammatory process.…”

“…In this respect, the complement system plays a key role in the fish defence against this pathogen, as it displays potent antiparasitic activity, especially when activated by the classical pathway [ 11 , 20 ]. In addition to complement, the fish coagulation system also plays an important role in immobilizing and killing the parasite [ 21 ].…”

Protein Deimination and Extracellular Vesicle Profiles in Antarctic Seabirds

“…Fibrinogen is a glycoprotein, synthesised in liver and forms part of the acute phase response as part of the coagulation cascade [85]. Fibrinogen has diverse functions, including roles in the immune defence and has for example been associated with host defences against pathogens, as well as in acute phase and stress responses and in toxicity [86,87]. In humans, various fibrinogen disorders are known, related to coagulopathies, ischemic stroke, cancer, liver disease or post-translational modifications [88].…”

Evidence for the role of extrusomes in evading attack by the host immune system in a scuticociliate parasite

“…In addition, it must evade attack by the fish immune system, especially by lysis induced by soluble factors in the serum, such as complement. Activation of complement via the classical route (in conjunction with antibodies), together with activation of the coagulation system, causes destruction of the parasite [15–17]. Two types of extrusomes have been characterized in P. dicentrarchi : one fusiform, compatible with trichocysts, and the other spherical, compatible with mucocysts, and which release a thin layer of mucus on the cell surface [18,19].…”