G1 antigen: a cell-surface immunoprotective 96 kDa glycoprotein from the virulent fish pathogen Enterococcus seriolicida, its purification and characterization

Strains of the fish pathogen Enterococcus seriolicida were identified as ag glutinating and non-agglutinating, according to their reaction with anti-se rum raised against type strain YT-3 (ATCC49156). The non-agglutinating stra ins are highly pathogenic in contrast to agglutinating strains. A 96 kDa im munoprotective glycoprotein G1 antigen from non-agglutinating Ent. seriolic ida strain SS91-014 (N) was purified and characterized. The purification pr ocedure entailed extraction of antigen by glass bead agitation, 80% (NH4)(2 )SO4 precipitation, gel filtration and electroelution. An immunofluorescenc e microscopy study using monoclonal antibody M3A5 raised against G1 antigen revealed that G1 antigen is present only on the cell surface of non-agglut inating strains. Therefore, the G1 antigen of virulent Ent. seriolicida cou ld be a potential candidate for protective vaccine against enterococcosis i n fish.