The Role of Extracellular Protease Produced by Vibrio anguillarum

Abstract

The role of protease in the pathogenicity of Vibrio anguillarum in experimental infections in Japanese eel (Anguilla japonica) and ayu (Plecoglossus altivelis), and its protective immunogenicity were investigated.
It was confirmed antigenically that the pathogen produced the same protease in the experimentally infected fish as in vitro, though proteolytic activity was not detected. Pre-treatments with a sublethal dose of the protease by intramuscular injection in eels or by immersion in ayu enhanced the susceptibility of the fish to V. anguillarum. When an eel serum was treated in vitro with 10-50μg/ml of protease, the bactericidal activity of the serum was completely reduced.
The protective immunogenicity of protease was demonstrated when the antigen was given to eels and ayu by injections. However, efficacy of the protease vaccine was overridden by its toxicity when ayu were vaccinated and challenged by immersion method.