Bacillus anthracis oedema toxin as a cause of tissue necrosis and cell type-specific cytotoxicity

Abstract

SummaryOedema factor (OF) and protective antigen (PA) are secreted by Bacillus anthracis , and their binary combination yields oedema toxin (OT). Following PAmediated delivery to the cytosol, OF functions as an adenylate cyclase generating high levels of cAMP. To assess OT as a possible cause of tissue damage and cell death, a novel approach was developed, which utilized a developing zebrafish embryo model to study toxin activity. Zebrafish embryos incubated with OT exhibited marked necrosis of the liver, cranium and gastrointestinal tract, as well as reduced swim bladder inflation. The OT-treated embryos survived after all stages of development but succumbed to the toxin within 7 days. Additional analysis of specific cell lines, including macrophage and non-macrophage, showed OT-induced cell death is cell type-specific. There was no discernible correlation between levels of OF-generated cAMP and cell death. Depending on the type of cell analysed, cell death could be detected in low levels of cAMP, and, conversely, cell survival was observed in one cell line in which high levels of cAMP were found following treatment with OT. Collectively, these data suggest OT is cytotoxic in a celldependent manner and may contribute to disease through direct cell killing leading to tissue necrosis.

Identification of Clostridium difficile toxin B cardiotoxicity using a zebrafish embryo model of intoxication

“…[24][25][26]. Previous studies have shown that PA can target multiple tissues within the zebrafish (27,28). As shown in Fig.…”

Sepsis and Pathophysiology of Anthrax in a Nonhuman Primate Model

“…Like patients, our primates receive antibiotics, and PA antigen was low to undetectable after 24 hours, yet animals challenged with 0.5 to 1.6 ϫ 10 9 CFU/kg still succumbed in 3 to 4 days. Edema toxin will induce necrosis in a zebra fish model, 67 and high doses of edema toxin induce multiple organ failure secondary to vascular permeability changes in mice. 68 In the baboons, necrosis was not observed in the lungs but was present in the adrenals and in kidneys secondary to microthrombosis (not shown).…”

The Major Neutralizing Antibody Responses to Recombinant Anthrax Lethal and Edema Factors Are Directed to Non-Cross-Reactive Epitopes

“…rEF and rLF proteins were produced as amino-terminal His 6 -tagged proteins as previously described (31,36). Cultures of BL-21/pET15b (containing LF and EF cDNA from B. anthracis) were grown in Luria broth containing ampicillin (50 g/ml) to an optical density at 600 nm (OD 600 ) of 0.6 to 0.8, and protein expression was induced by addition of 1 mM isopropyl ␤-D-thiogalactoside (IPTG) overnight at 16°C.…”