Back to the Future: Studying Cholera Pathogenesis Using Infant Rabbits

Abstract

ABSTRACTCholera is a severe diarrheal disease, caused byVibrio cholerae, for which there has been no reproducible, nonsurgical animal model. Here, we report that orogastric inoculation ofV. choleraeinto 3-day-old rabbits pretreated with cimetidine led to lethal, watery diarrhea in virtually all rabbits. The appearance and chemical composition of the rabbit diarrheal fluid were comparable to those of the “rice-water stool” produced by cholera patients. As in humans,V. choleraemutants that do not produce cholera toxin (CT) and toxin-coregulated pilus (TCP) did not induce cholera-like disease in rabbits. CT induced extensive exocytosis of mucin from intestinal goblet cells, and wild-typeV. choleraewas predominantly found in close association with mucin. Large aggregates of mucin-embeddedV. choleraewere observed, both attached to the epithelium and floating within the diarrheal fluid. These findings suggest that CT-dependent mucin secretion significantly influencesV. cholerae’s association with the host intestine and its exit from the intestinal tract. Our model should facilitate identification and analyses of factors that may governV. choleraeinfection, survival, and transmission, such as mucin. In addition, our results using nontoxigenicV. choleraesuggest that infant rabbits will be useful for study of the reactogenicity of live attenuated-V. choleraevaccines.IMPORTANCECholera remains a significant threat to populations in developing nations. Currently, there is no reproducible, nonsurgical animal model of cholera, the secretory diarrheal disease caused byVibrio cholerae. We found that oral infection of infant rabbits withV. choleraeled to lethal, watery diarrhea in most rabbits. Using this disease model, we discovered a new role for cholera toxin (CT) during infection. This toxin not only caused secretory diarrhea but also profoundly influenced howV. choleraeassociates with the intestine and how the pathogen exits from the host. Rabbits inoculated withV. choleraethat does not produce CT developed mild diarrhea, suggesting that this model may prove useful for generating improved live attenuated-V. choleraevaccine candidates. Overall, our findings suggest that the infant rabbit model will enable pursuit of several new avenues for research on cholera pathogenesis, as well as serve as a vehicle for testing new therapeutics.