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

Abstract

Clostridium difficile toxin B (TcdB) has been studied extensively by using cell-free systems and tissue culture, but, like many bacterial toxins, the in vivo targets of TcdB are unknown and have been difficult to elucidate with traditional animal models. In the current study, the transparent Danio rerio (zebrafish) embryo was used as a model for imaging of in vivo TcdB localization and organ-specific damage in real time. At 24 h after treatment, TcdB was found to localize at the pericardial region, and zebrafish exhibited the first signs of cardiovascular damage, including a 90% reduction in systemic blood flow and a 20% reduction in heart rate. Within 72 h of exposure to TcdB, the ventricle chamber of the heart became deformed and was unable to contract or pump blood, and the fish exhibited extensive pericardial edema. In line with the observed defects in ventricle contraction, TcdB was found to directly disrupt coordinated contractility and rhythmicity in primary cardiomyocytes. Furthermore, using a caspase-3 inhibitor, we were able to block TcdB-related cardiovascular damage and prevent zebrafish death. These findings present an insight into the in vivo targets of TcdB, as well as demonstrate the strength of the zebrafish embryo as a tractable model for identification of in vivo targets of bacterial toxins and evaluation of novel candidate therapeutics.bacterial toxin ͉ Clostridium difficile-associated disease ͉ large clostridial toxins

The roles of toxin A and toxin B inClostridium difficileinfection

“…This finding drew into question the long-standing hypothesis that TcdA was actually more important in the pathogenesis of disease, but was in agreement with other recent work highlighting the importance of TcdB. 1,2,7 Our work also confirmed that systemically administered antibodies were detectable not only in the blood, as expected, but were also detectable in the intestinal lumen.…”

Toxin-Mediated Paracellular Transport of Antitoxin Antibodies Facilitates Protection against Clostridium difficile Infection

“…Furthermore, since toxins can induce their own transport to the basolateral/ systemic side ( Fig. 6 and reference 30), perhaps allowing them to enter the circulation and reach other organs (39,40), circulating neutralizing antibodies should prevent systemic effects, if any, of C. difficile toxins. Whether these advantages will translate to systemically administered antibodies, such as actoxumab-bezlotoxumab, versus orally delivered neutralizing antibodies remains to be confirmed.…”

An Optimized, Synthetic DNA Vaccine Encoding the Toxin A and Toxin B Receptor Binding Domains of Clostridium difficile Induces Protective Antibody ResponsesIn Vivo

“…However, systemic toxin is not indicative of a normal infection scenario, since the majority of clinical manifestations of CDAD are selflimiting within the intestine (51). In life-threatening cases, however, systemic complications have been documented (52)(53)(54)(55)(56), and entry of the toxin into circulation is thought to be a possible cause (57). Therefore, challenging immunized mice with intraperitoneal toxin represents a stringent method for assaying the nAb response.…”