First evidence for a Vibrio strain pathogenic to Mytilus edulis altering hemocyte immune capacities

Abstract

Bacterial isolates were obtained from mortality events affecting Mytilus edulis and reported by professionals in 2010-2013 or from mussel microflora. Experimental infections allowed the selection of two isolates affiliated to Vibrio splendidus/Vibrio hemicentroti type strains: a virulent 10/068 1T1 (76.6% and 90% mortalities in 24 h and 96 h) and an innocuous 12/056 M24T1 (0% and 23.3% in 24 h and 96 h). These two strains were GFP-tagged and validated for their growth characteristics and virulence as genuine models for exposure. Then, host cellular immune responses to the microbial invaders were assessed. In the presence of the virulent strain, hemocyte motility was instantaneously enhanced but markedly slowed down after 2 h exposure. By contrast, hemocyte velocity increased in the presence of the innocuous 12/056 M24T1. At the same time interval, 10/068 1T1 invaded hemocytes and was more rapidly internalized than the innocuous strain. Extracellular products (ECPs) prepared from 10/068 1T1 cultures significantly inhibited phagocytic activity while 12/056 M24T1 ECPs had no effect. Furthermore, the pathogenic strain and its ECPs inhibited oxidative burst unlike 12/056 M24T1 strain/ECPs which enhanced ROS production. Taken together, our results suggest that the mussel pathogen 10/068 1T1 may escape immune response by altering hemocytes functions.

Antiviral Activity of Myticin C Peptide from Mussel: an Ancient Defense against Herpesviruses

“…This could be the case with myticins in mussels. Interestingly, M. galloprovincialis, with the exception of some infrequent pathologies, does not appear to be susceptible to diseases (37), in contrast to other bivalves, such as oysters and clams (38)(39)(40). In this paper, we have shown that they are resistant to one of the most dangerous bivalve pathogens worldwide, OsHV-1, which does not appear to be a threat for the species.…”

Mortality investigation of Mytilus edulis and Mytilus galloprovincialis in France: An experimental survey under laboratory conditions

“…A pathogenic strain of Vibrio splendidus was isolated from moribund mussels sampled in 2014 (Polsenaere et al 2017, Oden el al. 2016 as in some previous mortality events in (Ben Cheikh et al 2015. Meanwhile, their roles on mortality outbreak in French cultured mussel populations are still unknown.…”

“…to induce significant mortality in M. edulis following experimental infection under laboratory conditions (Ben Cheikh, et al, 2015). Similar experimental infection was conducted using 23…”

Experimental infection of Mytilus edulis by two Vibrio splendidus‐related strains: Determination of pathogenicity level of strains and influence of the origin and annual cycle of mussels on their sensitivity

“…By achieving the objective of testing bacterial concentrations consistent with those found in sea water or in mussel tissues (~10 4 CFU animal −1 ; Eiler et al, 2007;Garnier et al, 2007;Pfeffer et al, 2003), as well as high concentrations (~10 7 CFU animal −1 ), different results were observed. Most of the experimental infections performed on mussels (Ben Cheikh, Travers, & Foll, 2017;Ben Cheikh et al, 2016;Parisi et al, 2008;Tanguy et al, 2013) or oysters (Garnier et al, 2007;Gay, Berthe, & Roux, 2004;Travers et al, 2017) were made by injections with high bacterial strain concentrations around 10 7 /10 8 CFU animal −1 which is quite far from those found in the field. On this point, Travers et al (2017) mentioned that defining a strain as virulent through high concentration injections was a debatable issue.…”