Curtailing cholera

A team led by Hiroshi Kiyono from the University of Tokyo, Japan, has developed a rice-based oral vaccine (MucoRice-CTB) that effectively induces neutralizing antibodies against the acute, and often fatal, disease cholera¹.

MucoRice-CTB contains a component of cholera toxin (CT) produced by Vibrio cholerae, the bacterium responsible for cholera. The researchers previously showed that MucoRice-CTB protects against CT-induced diarrhea in mice and also induces CT-neutralizing antibodies in monkeys. They have now shown that intestinal secretion of specific CT-neutralizing IgA antibodies (or secretory IgA: SIgA) following oral immunization with MucoRice-CTB is critical for protection against CT-induced diarrhea in mice. Immunized mice were protected up to six months after primary immunization and a further four months by a single booster immunization.

MucoRice-CTB also protected mice against enterotoxigenic Escherichia coli (ETEC), another major cause of human diarrheal disease, because CT-neutralizing antibodies also recognize the heat-labile toxin of ETEC. MucoRice-CTB remained effective even after storage for three years at room temperature, suggesting that it could be distributed cheaply without refrigeration. Moreover, oral administration of the vaccine eliminates the need for needles and syringes.

The findings confirmed the potential of MucoRice-CTB as a new-generation oral vaccine. Clinical trials are now needed to show whether it is effective in preventing cholera and ETEC-induced gastroenteritis in humans.