AIP56: A Novel Bacterial Apoptogenic ToxinAuthor(s): Manuel T. Silva | Nuno M. S. dos Santos | Ana do Vale
Journal: Toxins ISSN 2072-6651
Volume: 2; Issue: 4; Start page: 905; Date: 2010;
Keywords: Photobacterium damselae subsp. piscicida | AIP56 | AB toxin | apoptosis | secondary necrosis
Photobacterium damselae subsp. piscicida (Phdp) is a Gram-negative pathogen agent of an important fish septicemia. The key virulence factor of Phdp is the plasmid-encoded exotoxin AIP56, which is secreted by exponentially growing pathogenic strains. AIP56 has 520 amino acids including an N-terminal cleavable signal peptide of 23 amino acid residues, two cysteine residues and a zinc-binding region signature HEXXH that is typical of most zinc metallopeptidases. AIP56 induces in vitro and in vivo selective apoptosis of fish macrophages and neutrophils through a caspase-3 dependent mechanism that also involves caspase-8 and -9. In vivo, the AIP56-induced phagocyte apoptosis progresses to secondary necrosis with release of cytotoxic phagocyte molecules including neutrophil elastase. Fish injected with recombinant AIP56 die with a pathology similar to that seen in the natural infection.