Antigens ofEdwardsiella ictalurirecognised by serum antibodies from naturally infected channel catfish

Immunogenicity of whole cell lysates ofEdwardsiella ictaluriand bacterial fractions enriched for outer membrane proteins (OMP), flagella and lipopolysaccharide (LPS) was examined using pooled convalescent sera from channel catfish (Ictalurus punctatus) that had survived a natural infection withE. ictaluri. Bacterial components were separated by gel electrophoresis; proteins were stained with Coomassie brilliant blue and LPS were stained with silver. Thirty-eight proteins were identified in whole-cell preparations (apparent molecular masses of 108 kDa to 14 kDa). Thirteen proteins were identified in OMP preparations (apparent molecular masses of 84 kDa to 16 kDa). Two flagellar proteins (apparent molecular masses of 45 kDa and 37 kDa) were identified. Low and medium molecular mass LPS were seen on purified LPS preparations. Immunogenicity was evaluated by indirect staining following transfer of bacterial antigens to nitrocellulose paper. Lipopolysaccharide and the 39 kDa OMP were strongly recognised by antibodies in pooled sera from channel catfish naturally infected withE. ictaluri. One flagellar protein (37 kDa), nine OMP, and five unidentified proteins seen on whole cell preparations stained less strongly.