Scientists discover key to creating potential cholera vaccine

BOSTON, Mass. — Contaminated drinking water can be a problem in any region of the world, but it’s especially dangerous in impoverished nations. One of the biggest threats that comes from it is cholera, an illness causing infection in the intestines. Now, a team from Massachusetts General Hospital (MGH) says they’ve discovered a potential key to stopping this illness that kills thousands each year.

Cholera is caused by bacteria called Vibrio cholerae which is mostly commonly ingested by people drinking water contaminated with feces. The bacteria settles in the intestines and starts to secrete a toxin inside the body. This causes intestinal cells to produce a large amount of fluid that leads to death by dehydration and shock.

The Centers for Disease Control and Prevention say around three million cases of cholera are reported each year and 95,000 people die from the illness worldwide. Symptoms are mild in most cases, but one in 10 will suffer a severe case including diarrhea, vomiting, and leg cramps. Without treatment, these patients can die within hours of infection.

Cutting off cholera’s ability to swim

Researchers say one problem with fighting cholera is that typical immune responses to toxins don’t protect against the illness. Lead investigator Edward Ryan, director of Global Infectious Diseases at MGH, finds there are antibodies which can bind to Vibrio cholerae’s sugar coating and protect patients from getting sick.

Ryan notes that current vaccines for cholera don’t do a great job of protecting young children, who are some of the most common cholera patients. These treatments also provide a relatively short period of protection from the infection. The study finds the bacteria’s sugary coating — called O-specific polysaccharide (OSP) — is particularly prevalent in the germ’s tail. This tail gives V. cholerae it’s ability to swim through a patient’s system.

“V. cholerae are very mobile, and swimming is critical to their ability to cause disease,” Ryan explains. “Interestingly, the tail-like flagellum in V. cholerae that propels swimming is coated with the OSP sugar.”

Researchers demonstrated how certain antibodies can grab on to this OSP coating and stop V. cholerae’s ability to swim through the body causing disease.

“Our results support a unique mechanism of protection against a human pathogen. We are not aware of previous work demonstrating a comparable direct anti-motility effect of human antibodies,” Ryan adds.

The study appears in the journal mBio.

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