Evidence for Widespread Epithelial Damage and Coincident Production of Monocyte Chemotactic Protein 1 in a Murine Model of Intestinal Ricin Intoxication

Abstract

The development of small-animal models is necessary to understand host responses and immunity to emerging infectious diseases and potential bioterrorism agents. In this report we have characterized a murine model of intestinal ricin intoxication. Ricin administered intragastrically (i.g.) to BALB/c mice at doses ranging from 1 to 10 mg/kg of body weight induced dose-dependent morphological changes in the proximal small intestine (i.e., duodenum), including widespread villus atrophy and epithelial damage. Coincident with epithelial damage was a localized increase in monocyte chemotactic protein 1, a chemokine known to be associated with inflammation of the intestinal mucosa. Immunity to intestinal ricin intoxication was achieved by immunizing mice i.g. with ricin toxoid and correlated with elevated levels of antitoxin mucosal immunoglobulin A (IgA) and serum IgG antibodies. We expect that this model will serve as a valuable tool in identifying the inflammatory pathways and protective immune responses that are elicited in the intestinal mucosa following ricin exposure and will prove useful in the evaluation of antitoxin vaccines and therapeutics.The development and testing of effective vaccines and therapeutics against potential bioterrorism agents pose major challenges to the biomedical scientific community (2). Foremost is the fact that human exposure to these so-called select agents is rare and often is poorly documented in the clinic. Consequently, an understanding of the molecular basis of both pathophysiology of and protective immunity to this diverse collection of viruses, microbial pathogens, and toxins must rely on the use of well-established animal models. This is especially true in the case of ricin toxin, a potent ribosome-inactivating protein from the castor bean (Ricinus communis) that has already proven to be an effective murder weapon and bioterrorism agent (25).While ricin (ϳ64 kDa) is one of the simplest members of the A-B family of toxins, it is also one of the most promiscuous (32, 37). The toxin's single A subunit (RTA) is an N-glycosidase that selectively depurinates a conserved adenine residue within 28S rRNA and in this respect is indistinguishable from shiga toxin (11). The toxin's B subunit (RTB) is a bivalent lectin that mediates toxin attachment to terminal galactose residues on glycoproteins and glycolipids (4). The ubiquitous nature of ricin's receptors, combined with its universally conserved enzymatic substrate, enables ricin to intoxicate virtually all known cell types. Not surprisingly, ricin can be lethal to humans following injection, inhalation, or ingestion (3,6,26).Although a recent expert panel workshop sponsored by the National Institutes of Health deemed the adulteration of food and water supplies to be the most likely mechanism by which ricin would be disseminated as a bioterrorism agent, very little is known about the effects of ricin on the gastrointestinal mucosa (1). Ingestion of whole castor beans results in severe abdominal pain, vomiting, diarrhea, and (depending o...

RiVax, a recombinant ricin subunit vaccine, protects mice against ricin delivered by gavage or aerosol

“…Other studies investigating the toxic effects of ricin given orally have since been conducted [24][25][26], but these relied on the published LD 50 of 30 mg/kg in animals that had not been fasted or were fasted for very short intervals before dosing. In one study [ 24 ], they harvested tissues for examination after only five hours after ricin was administered, so they would not have known if the lowest dose used (1 mg/kg) was lethal or sublethal.…”

“…In our experience, naïve mice fasted both before and after the administration of ricin die within 48 h after receiving a dose of 0.1 mg/kg. In a recent study [ 26 ], mice were fasted for one hour both prior to and following the oral administration of 1 to 10 mg/kg doses of ricin. Extensive dose-dependent epithelial damage was reported in the proximal small intestine at doses of ricin exceeding 2.5 mg/kg, and our results are consistent with this observation.…”

“…These include ricin toxoid [ 4,26 ] and dgRTA (Leonard Smith, USAMRIID, personal communication). Both i.m.…”

SOCS3 Regulates BAFF in Human Enterocytes under Ribosomal Stress

“…Stress responses by ribosome-inactivating (ribosomal stress) agents that cause mucosal insults are etiological factors of epithelial inflammatory diseases and have been investigated in various experimental models (28)(29)(30). Specific ribosome-directed xenobiotics, such as anisomycin (ANS), UV radiation, ricin, and a variety of sesquiterpenoid trichothecene fungal metabolites, can damage the functionality of 28S rRNA during gene translation, which leads to ribosomal stress that stimulates intracellular sentinel-signaling pathways.…”

Acquisition of Chemoresistance and Other Malignancy-related Features of Colorectal Cancer Cells Are Incremented by Ribosome-inactivating Stress

“…We are exposed to various types of ribosome-related insults from the environment, dietary factors, and therapeutics (14 -16). Among these, mucoactive ribosome-inactivating stress (RIS) as a potent etiological factor of epithelial inflammatory diseases has been investigated in various experimental models (17,18). Specific ribosome-directed inactivating xenobiotics such as deoxynivalenol (DON) and anisomycin (ANS) damage the functionality of 28S ribosomal RNA during gene translation (19 -23).…”