Role of scuticociliate proteinases in infection success in turbot, Psetta maxima (L.)

Abstract

Scuticociliatosis caused by Philasterides dicentrarchi is one of the most severe diseases of farmed turbot, Psetta maxima (L.). Immunized fish showed elevated levels of specific antibodies (Ab), which caused the destruction of parasites through the activation of complement by the alternative and classical pathways. By using affinity chromatography on bacitracin-sepharose columns, we demonstrated the existence of high levels of parasite proteinases in the serum and, to a lesser extent, in the ascitic fluid of experimentally infected fish, and the absence of such proteinases in the serum of uninfected fish. Serum from uninfected fish displayed haemolytic activity against sheep red blood cells. However, incubation of this serum with parasite proteinases led to a decrease in serum haemolytic activity, suggesting that proteinases are able to destroy fish complement. Proteinases isolated from serum or ascitic fluid of infected fish were also able to degrade turbot Ab. Preincubation of turbot serum containing specific Ab for P. dicentrarchi with the proteinases led to a significant decrease in the killing activity of the serum. The results confirm that P. dicentrarchi proteinases in serum from infected fish may provide a mechanism for circumventing normal host immunity by inactivating the Ab and complement factors required for complement activation.

Antigenic characterization of Enteromyxum leei (Myxozoa: Myxosporea)

“…Proteolytic enzymes generated by parasites are often involved in such processes, as studied for the myxozoans Kudoa sp. (Martone et al 1999, Funk et al 2008, Myxobolus cerebralis (Kelley et al 2004, Dörfler & El-Matbouli 2007 and Sphaerospora dicentrarchi (Muñoz et al 2000a), as well as for other piscine parasites (Zuo & Woo 1998, Paramá et al 2004, Piazzón et al 2011. There is no current knowledge about the mechanisms that Enteromyxum leei employs to disrupt cell junctions between enterocytes, to penetrate and invade the intestinal epithelium and to migrate along the digestive tract.…”

Molecular cloning and expression analysis of peptidase genes in the fish-pathogenic scuticociliate Miamiensis avidus

“…It has been reported that peptidases secreted by Philasterides dicentrarchi can degrade type-I collagen, modulate host cellular immune responses, and induce apoptosis of leucocytes [8-11]. Moreover, P. dicentrarchi peptidases could affect host humoral immune responses by degrading the host immunoglobulins and reducing host complement activity in fish serum and ascitic fluid [12]. …”

Use of Cell Cultures to Study the Interactions of Ciliates with Fish

“…However complement that was activated through the classical pathway was a potent killer of M. avidus [159,160]. These results suggested that the humoral responses were more important than cellular immune responses in defense against M. avidus [161,159].…”

“…The avirulent Tet-NI 1 had no cysteine protease activity, whereas the virulent Tet-NI 6 had high levels of activity. Cultures of M. avidus have been used as source of proteinases and a way of evaluating the killing activity of sera from fish that had or had not been injected with the ciliate [158,161]. Through activation of the classical complement pathway, serum from vaccinated turbot killed M. avidus in culture [160,161].…”

“…Cultures of M. avidus have been used as source of proteinases and a way of evaluating the killing activity of sera from fish that had or had not been injected with the ciliate [158,161]. Through activation of the classical complement pathway, serum from vaccinated turbot killed M. avidus in culture [160,161]. However, proteinases from P. dicentrarchi were able to degrade the antibodies and factors necessary for complement activation and to decrease killing of the ciliates.…”