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C. difficile Vaccine Proves Safe and 100 Percent Effective in Animal Models

An experimental vaccine protected 100 percent of animal models against the highly infectious and virulent bacterium, Clostridium difficile (image), which causes an intestinal disease that kills approximately 30,000 Americans annually. The research was published ahead of print on July 14, 2014 in Infection and Immunity. In the study, the vaccine protected the mice and non-human primates against the purified toxins produced by C. difficile, as well as from an orogastric spore infection, a laboratory model that mimics the human disease, after only two immunizations. "Animals that received two immunizations did not get sick or show signs of C. difficile-associated disease," says corresponding author Michele Kutzler, Ph.D., of Drexel University College of Medicine, Philadelphia. "While our research was conducted in animal models, the results are very translatable to the clinic," says Dr. Kutzler. "In some cases, patients who acquire C. difficile can develop serious complications including severe diarrhea, toxic megacolon, bowel perforation, multi-organ failure, and death. Once fully developed, our DNA vaccine could prevent the deadly effects of C. difficile infection when administered to hospital patients at risk of acquiring C. difficile." The protection following just two immunizations is especially important because the time window in humans between colonization with C. difficile and the onset of disease symptoms can be a mere 10-14 days, says Dr. Kutzler. The vaccine protects against the bacterial toxins by mustering anti-toxin neutralizing antibodies, says Dr. Kutzler. The cost of fighting the half million C. difficile infections that occur annually in the U.S. is estimated to be nearly $10 billion, most of which could be saved by a successful preventive vaccine, says Dr. Kutzler. Morbidity and mortality have risen over the last decade, likely due to increased prevalence of relapsing disease, and hypervirulent strains, she adds. Treating the disease is especially difficult, as the bacterial spores persist in the hospital environment, where most infections occur. There is no standard, effective treatment for recurrent disease, but a small number of experimental fecal transplants for C. difficile have had a very high success rate, with no adverse reactions. "Since our vaccine was safe, effective after only two immunizations, and performed exceptionally well, we feel that this success warrants further studies using human patients," says Dr. Kutzler. [Press release] [Infection and Immunity abstract]