Cloning, characterisation and expression of Aeromonas hydrophila major adhesin

Aeromonas hydrophila, an important pathogen in fish, is believed to cause diseases by adhesive and enterotoxic mechanisms. The adhesion is a prerequisite for successful invasion. In this study, the gene of a 43 kDa major adhesin (designated as AHA1) was cloned and expressed. Nucleotide sequence analysis of AHA1 revealed an open reading frame encoding a polypeptide of 373 amino acids with a 20-amino-acid putative signal peptide (molecular weight 40,737 Da). The amino acid sequences of Aha1p showed a very high homology with the other two outer membrane proteins of A. hydrophila. Using the T-5 expression system, this major adhesin Aha1p was expressed in Escherichia coli. The purified recombinant adhesin could competitively inhibit A. hydrophila from invading fish epithelial cells in vitro. Western-blot analysis showed that this major adhesin is a very conserved antigen among various strains of Aeromonas. When used to immunise blue gourami, the recombinant adhesin could confer significant protection to fish against experimental A. hydrophila challenge. (C) 2004 Elsevier Ltd. All rights reserved.