The humoral immune response of Atlantic salmon and rabbit against carbohydrate cell wall antigens ofRenibacterium salmoninarum

The humoral immune response of Atlantic salmon and rabbit against carbohydrate cell wall antigens ofRenibacterium salmoninarumwas studied after immunisation with whole bacterial cells (WC) and trypsinised cells (TC). Trypsination was shown to remove all proteins from theR. salmoninarumcells, and TC thus represents the carbohydrate skeleton of the bacterial cells. A galactose-rich polysaccharide (GPS) and peptidoglycan (PG) are the quantitatively most important carbohydrate constituents of theRenibacteriumcell wall. Antibodies to GPS were readily detectable in sera from rabbits immunised with TC, but not in sera from Atlantic salmon immunised with TC or WC. On the other hand, sera from Atlantic salmon immunised with TC showed relatively high titres of antibodies to PG, whereas sera from rabbits immunised with TC hardly contained antibodies to PG. The TC preparate contained mannose and glucose in its cell wall in addition to the monosaccharide constituents from GPS and PG. This indicates the presence of additional polysaccharide(s) and/or glycolipid(s) that may also be immunogenic which is also suggested by the immunological data presented.