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Related Experiment Video

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Applying an Inducible Expression System to Study Interference of Bacterial Virulence Factors with Intracellular Signaling

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Published on: June 25, 2015

AIP56: a novel bacterial apoptogenic toxin.

Manuel T Silva¹, Nuno M S Dos Santos, Ana do Vale

¹IBMC-Instituto de Biologia Molecular e Celular, Rua do Campo Alegre, 823. 4150-180 Porto, Portugal. mtsilva@ibmc.up.pt

|November 10, 2011

Summary

Photobacterium damselae subsp. piscicida (Phdp) exotoxin AIP56 triggers fish immune cell apoptosis, leading to septicemia. This virulence factor causes disease pathology similar to natural infections in fish.

Keywords:

AB toxin AIP56 Photobacterium damselae subsp. piscicida apoptosis secondary necrosis

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Area of Science:

* Microbiology and Immunology
* Fish Pathology
* Bacterial Pathogenesis

Background:

* Photobacterium damselae subsp. piscicida (Phdp) is a Gram-negative bacterium causing significant fish septicemia.
* The plasmid-encoded exotoxin AIP56 is a primary virulence factor of Phdp, secreted during active bacterial growth.

Purpose of the Study:

* To investigate the role and mechanism of the exotoxin AIP56 in fish septicemia.
* To elucidate the effects of AIP56 on fish immune cells and its contribution to disease pathogenesis.

Main Methods:

* Analysis of AIP56 protein structure, including signal peptide and zinc-binding region.
* In vitro and in vivo studies assessing AIP56's impact on fish macrophages and neutrophils.
* Examination of apoptosis pathways (caspase-3, -8, -9) and secondary necrosis markers.

Main Results:

* AIP56 selectively induces apoptosis in fish macrophages and neutrophils via a caspase-dependent pathway.
* In vivo, AIP56-induced apoptosis leads to secondary necrosis and release of cytotoxic molecules like neutrophil elastase.
* Experimental infection with recombinant AIP56 mimics the pathology of natural Phdp septicemia.

Conclusions:

* AIP56 is a critical virulence factor responsible for the immunopathology of Phdp infections in fish.
* Targeting AIP56 or its downstream effects could offer strategies for controlling fish septicemia.