Cholera is a water–transmitted disease caused by the Vibrio cholerae bacteria that can cause death due to dehydration and diarrhea. It is most prevalent in the water sources found in Africa, Southeast Asia, and Haiti, and causes around 20000-140000 deaths every year. The best way to prevent this is through immunization by injection or oral vaccines.
Although oral cholera vaccines exist, their need for refrigeration poses logistical issues in distribution, especially in remote areas. However, this issue may soon have an answer, courtesy of a research team from Japan.
According to a study published in The Lancet Microbe, researchers from the University of Tokyo and Chiba University have created a genetically modified strain of Japanese short-grain rice that can produce the nontoxic portion of the cholera toxin B (CTB). The rice, named MucoRice-CTB, may then be ground, mixed with water, and ingested. The rice ensures that the toxin survives the acidic environment of the stomach to be naturally absorbed by the intestines. There, the CTB can stimulate IgG and IGA antibody formation to prepare the immune system against future infections.
The Phase-1 trial
To test the MucoRice-CTB, the researchers conducted a clinical trial with 60 volunteers. 30 received the oral vaccine in varying concentrations of 1g, 3g, or 6g, and 30 others received a placebo. The volunteers then underwent multiple tests to monitor the vaccine’s safety and efficacy, and any adverse reactions they had.
Regarding safety, the vaccine group only reported 5 grade-3 and above adverse events as compared to the placebo group’s 10. The vaccine was also highly effective, with only 11 non-responders. This, apparently, had to do with gut micro biodiversity, so the researchers checked the volunteer’s fecal samples.
“In simplified terms, high responders had more diversified microflora, and in the low-responder group, diversity was much narrower. It’s all speculation right now, but maybe higher microflora diversity creates a better situation for strong immune response against oral vaccine,”Lead scientist Professor Hiroshi Kiyono (D.D.S., Ph.D., Institute of Medical Science at the University of Tokyo, faculty member at Chiba University in Japan and the University of California, San Diego).
Because the trial only included Japanese males, the researchers now look forward to conducting further phase 1 trials with volunteers of different ethnic backgrounds.
Source: University of Tokyo
Researchers from Japan have successfully completed Phase 1 trials for a cholera vaccine made of rice