Molecular basis of toxicity of Clostridium perfringens epsilon toxin

Abstract

Clostridium perfringensε‐toxin is produced by toxinotypes B and D strains. The toxin is the aetiological agent of dysentery in newborn lambs but is also associated with enteritis and enterotoxaemia in goats, calves and foals. It is considered to be a potential biowarfare or bioterrorism agent by the US Government Centers for Disease Control and Prevention. The relatively inactive 32.9 kDa prototoxin is converted to active mature toxin by proteolytic cleavage, either by digestive proteases of the host, such as trypsin and chymotrypsin, or by C. perfringensλ‐protease. In vivo, the toxin appears to target the brain and kidneys, but relatively few cell lines are susceptible to the toxin, and most work has been carried out using Madin–Darby canine kidney (MDCK) cells. The binding of ε‐toxin to MDCK cells and rat synaptosomal membranes is associated with the formation of a stable, high molecular weight complex. The crystal structure of ε‐toxin reveals similarity to aerolysin from Aeromonas hydrophila, parasporin‐2 from Bacillus thuringiensis and a lectin from Laetiporus sulphureus. Like these toxins, ε‐toxin appears to form heptameric pores in target cell membranes. The exquisite specificity of the toxin for specific cell types suggests that it binds to a receptor found only on these cells.

Hemolysis in human erythrocytes by Clostridium perfringens epsilon toxin requires activation of P2 receptors

“…Previous studies suggested that in MDCK cells exposed to ETX, a large membrane complex formed on the cell surface [38], leading to pore formation, efflux of K + , influx of Na + , Ca 2+ , and Cl − ions, and finally rapid cell death [3,11]. In ETX-treated RBCs, we observed an increase of intracellular Ca 2+ , which could be mostly inhibited by an antagonist of P2 receptors (S6 Fig).…”

“…C. perfringens epsilon toxin (ETX) is mainly produced by C. perfringens types B and D [2]. The toxin is the aetiological agent of dysentery in newborn lambs but is also associated with enteritis and enterotoxaemia in goats, calves and foals [3]. ETX is the third most lethal of all clostridial toxins, ranking behind only the Clostridium botulinum and Clostridium tetani neurotoxins [4].…”

“…ETX is the third most lethal of all clostridial toxins, ranking behind only the Clostridium botulinum and Clostridium tetani neurotoxins [4]. The fact that the 50% lethal dose (LD 50 ) of ETX in mice is 50 ng·kg −1 [5] underpins the potential to use this toxin as a bioterrorist weapon; therefore, ETX is regarded as a potential bioterrorism agent by the US Government Centers for Disease Control and Prevention [3]. …”

“…Active ETX binds to the intestinal epithelium to induce epithelial permeability in the absence of overt histologic damage [7] and enters the bloodstream. In vivo , the toxin appears to target the brain and kidneys, but a relatively restricted number of cell lines are susceptible to the toxin, with most work having been carried out in Madin Darby canine kidney (MDCK) cells [3]. Over the past few decades, a number of cell lines have been tested to identify a suitable in vitro model for the study of ETX [3].…”

“…In vivo , the toxin appears to target the brain and kidneys, but a relatively restricted number of cell lines are susceptible to the toxin, with most work having been carried out in Madin Darby canine kidney (MDCK) cells [3]. Over the past few decades, a number of cell lines have been tested to identify a suitable in vitro model for the study of ETX [3]. The Caucasian renal leiomyoblastoma (G-402) cell line [8], human kidney cell line ACHN [9], and murine renal cortical collecting duct principal cell line mpkCCDcl4 [10] were identified to be toxin-sensitive, albeit to a lesser extent than the MDCK cell line [3].…”