アユのビブリオ病に対するＶｉｂｒｉｏ ａｎｇｕｉｌｌａｒｕｍの抽出リポ多糖経口ワクチンの効果

Abstract

Previous papers on oral bacterin against vibriosis in cultured ayu plecoglossus altivelis showed that fish were effectively immunized with heated bacterin and that the agglutinin secreted in the body surface mucus of the immunized fish prevented pathogenic bacterium Vibrio anguillarum form adhering to the skin of ayu. These findings suggested that a heat stable antigen on the surface of the bacterium would play an important role in the protection against vibriosis. In this study it was investigated whether that lipopolysaccharide, a heat stable antigen in the cell wall, of V. anguillarium would be an effective immunogen or not. The lipopolysaccharide fraction extracted by WESTPHAL's method from the formalin killed bacterin was used as the extracted vaccine. Efficacy of the extracted vaccine was estimated by comparing mortality in the fish immunized with the extracted vaccine to that in the fish immunized with the formalin killed bacterin after challenge. Challenge test was executed by exposing fish to the bacteria discharged from the fish injected with the virulent strain. Administration of the extracted vaccine at a level of 25mg/fish kg/day for 9 days resulted in sufficient protection similar to that of the formalin killed bacterin at a level of 0.1g wet cells/fish kg/day for 9 days. Chemical analysis showed that the extracted vaccine contained a large percentage of lipopolysaccharide and nucleic acid but only a small percentage of protein and liped. From these results it is presumed that lipopolysaccharide is the protective antigen of the bacterin.