A new cholera vaccine has had positive results in tests performed on rabbits—offering protection against the disease within a day, according to the study published in Science Translational Medicine. The researchers believe this vaccine could someday help curb fast-spreading cholera, which is responsible for 21,000 – 143,000 worldwide deaths each year.
The vaccine was developed at Howard Hughes Medical Institute (HHMI) after researchers there traced the genetic origins of the Vibrio cholerae strain that caused the 2010 outbreak in Haiti. They realized that the bacteria had changed in the decades since existing cholera vaccines were designed.
The team decided to create a new version of the vaccine with a toothless V. cholerae as a protective shield. They began with the DNA sequence of the current version of the virulent V. cholerae and tweaked the genome to clear out anything that might make it dangerous. For example, if the bacteria were to somehow acquire the DNA sequence for making toxins, a CRISPR-based gene editing safeguard would chew up the DNA. They also altered the bacteria so they wouldn’t be able to swap genes easily to pick up toxic capabilities.
The new vaccine, called HaitiV, was tested in rabbits, which respond similarly to humans when infected with V. cholerae. The engineered bacteria colonized rabbit intestines with none of the ill effects of the regular V. cholerae bacteria. When vaccinated rabbits were infected with the pathogenic version of the bacteria 24 hours later, they did not get sick.
While the mechanism for this rapid protection is still not clear, the researchers suspect the vaccine protects in a way similar to a probiotic, perhaps competing for nutrients or interfering with toxin production in regular V. cholerae.
The researchers are working on starting clinical trials in people and making improvements to the vaccine, such as making it stable in environments where cholera is present.
Image: Some species of Vibrio bacteria (blue) can cause cholera in humans. A version of Vibrio choleraedesigned to be harmless may one day protect people against the dangerous form of the bacteria. Image courtesy of: Tina Carvalho, University of Hawaii at Manoa/CC BY 2.0.