Agrima Bhatt, Rajasthan University
What is Cholera?
Cholera is a diarrheal sickness caused by the toxigenic bacterium Vibrio cholerae infecting the intestine. Each year, an estimated 2.9 million cases and 95,000 deaths occur in the population worldwide. The World Health Organization estimates that 1.3 million to 4 million people are infected with cholera each year, with 21,000 to 143,000 deaths.
Drinking water polluted with sewage is the most common way for Vibrio cholerae germs to spread. Cholera causes severe symptoms such as watery diarrhoea, vomiting, and leg cramps in about one out of every ten people who contract it. With the rapid loss of bodily fluids associated with the disease, there might be dehydration and shock in people who are suffering from this disease, and without treatment, death can happen in an extremely short duration period.
Prevention of Cholera with Science
Currently, around the world, scientists have developed a total of 4 vaccines against cholera. Three of these vaccines have been approved by the World Health Organization (WHO). Dukoral®, ShanChol®, and Euvichol-Plus®/Euvichol®, three other oral inactivated or non-live cholera vaccines, have been certified for UN supply by WHO. The FDA has approved Vaxchora® which is a single-dose live oral cholera vaccine. It is meant for adults aged between 18 and 64, who are travelling to such areas where toxigenic Vibrio cholerae O1 is known to be active. However, till now, no cholera vaccine has shown to be 100% effective and immunization is not a substitute for regular cholera prevention and control measures, such as food and water precautions.
A novel cholera vaccine made from Genetically Modified Rice
Researchers based at the University of Tokyo and Chiba University used ground grains of genetically modified rice to create a novel vaccine to provide protection and fight against fatal cholera. There are four current needle-free cholera vaccines available, all of which are administered as drops under the tongue and are manufactured from whole dead or live-attenuated cholera cells whereas the MucoRice-CTB vaccine remains stable at room temperature and remains to be the first cold chain-free oral cholera vaccine.
This novel cholera vaccine is made from genetically modified Japanese short-grain rice plants which are capable of producing a harmless form of CTB that the immune system can identify. Because CTB is structurally identical to a toxin produced by certain types of disease-causing E. coli bacteria, cholera vaccines frequently confer cross-protection against travellers’ diarrhoea.
Working of the Novel Cholera Vaccine
MucoRice-CTB enters the body through the mucosal membranes of the intestine, simulating how germs are encountered and responded to in nature. IgG and IgA antibodies, which detect germs and target them for elimination, are produced when the mucosal immune system is stimulated. Vaccines injected under the skin or into a muscle tend to generate IgG antibodies rather than IgA antibodies.
After eight to 16 weeks, volunteers who responded to MucoRice-CTB had the greatest blood levels of antigen-specific IgG and IgA. Participants who received the two doses of MucoRice-CTB vaccine had higher CTB-specific blood IgG and IgA antibody concentrations without experiencing any major side effects, suggesting that MucoRice-CTB could be a safe and effective diarrhoeal illness vaccine.
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References:
- Yoshikazu, Y., Nojima, M., Hosono, O., et al. (2021). Oral MucoRice-CTB Vaccine for Safety and Microbiota-Dependent Immunogenicity in Humans: A Phase 1 Randomised Trial. The Lancet Microbe, https://doi.org/10.1016/S2666-5247(20)30196-8.
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