Genetic Key to Conquering Cholera

Cholera is an acute diarrheal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. It is a very scary disease. Now treatments with oral rehydration therapy is available, but it is still devastating, and in extreme cases, cholera can kill in hours.

Rearchers have already discovered that there is a hereditary component that determines whether a person is susceptibility to cholera or not. According to a paper published on 4 July 2013 in the journal Science Translational Medicine. Researchers gathered genetic data from 42 families (126 individuals) of Bangladesh. They were able to find number of areas in the genome, of which some are responsible for certain immune system function, while others are related to fluid loss – that appear to be related to cholera resistance. Later tests showed genetic difference between people who had contracted the disease and those who had been exposed, but did not become ill.

A team of researchers of Harvard is now uncovering evidence of genetic changes that might also help protect some people from contracting the deadly disease.

Elinor Karlsson, the first author of the research says that, the vaccine that is available for the disease wears off after a few years, whereas people who are exposed to the disease develop a long-lasting immunity, and nobody is quite sure why that is. This research is another way of tackling that problem, and it's a way no one has come at it before.

For their study they gathered genetic data on 42 family groups – called "trios" – that included a mother, father and child. Using that data, researchers identified more than 300 areas of the genome that appeared to be under pressure due to natural selection, suggesting that genes in those regions might be adapting to deal with the threat of cholera. Which is about two percent of the genome.

To precise their finding, they turned to a process called "gene set enrichment" testing to determine whether any particular groups of genes showed up in those regions more often than others.

They found set of genes that are related to a gene called IKBKG, which plays a key role in immunity. But they also found that it was not the gene itself, but a whole group of genes that regulate IKBKG. They also found set of genes for potassium channels, which are the channels in the walls of our cells that regulate fluid loss.

Armed with that data, researchers then performed a comparative study – examining the specific genetic regions in more than 100 patients who were sick with cholera and others who had been exposed to the disease, but had not become sick. The results, showed differences between the two groups.

Researchers hope to conduct wider studies of the genetic differences between people who are susceptible and those who appear to be immune in the hope of identifying precisely which genes are involved, and the pathways involved in resistance.