Visualization of Anthrax Toxin Intoxication in Mice

Authors

• SZ Li
• X Hu
• L Ye
• YM Ahn
• S Messing
• D Esposito
• NJ Martinez

Abstract

Morbidity and mortality of B. anthracis is attributed to secretion of anthrax lethal toxin (LT) and anthrax edema toxin (ET). LT and ET consist of a common protein, protective antigen (PA) and, respectively, lethal factor (LF) or edema factor (EF). Intoxication by LT or ET is initiated by binding of PA to widely expressed receptors, followed by cleavage of PA by furin and furin-like proteases. Cleavage of PA allows for cytoplasmic entry of LT and ET to exert their cytotoxicity.
We have previously reengineered PA to require single or dual cleavage by the tumor-associated proteases uPA and MMPs for cellular intoxication, thereby achieving high tumor selectivity when combined with LF. The mutant toxins display low systemic toxicity and high antitumor activity towards human and mouse tumors xenografted or syngrafted to mice, as well as towards naturally occurring oral squamous carcinomas and oral melanomas in feline and canine veterinary patients. We recently generated an assay that allows for single-cell resolution imaging of anthrax toxin intoxication of animals. This was achieved by using an LF-Cre fusion protein in combination with a Cre-reporter transgenic (mT/mG) mouse. When PA and LF-Cre are co-administered to mT/mG mice, intoxicated cells display membrane-localized green fluorescence, while non-intoxicated cells display membrane-localized red fluorescence. Cellular intoxication is visualized by confocal microscopy of intact tissues or flow cytometry of single cell suspensions.
We use the imaging assay to catalogue on- and off-targets for a variety of engineered toxin variants currently in preclinical development. Data from these studies will be presented.

Scientific Focus Area: Cancer Biology

This page was last updated on Monday, September 25, 2023