Researchers recently reported the discovery of the strongest genetic effect associated with the natural clearance of hepatitis C virus infection. Figuring out why 30 to 40 percent of those who contract hepatitis C somehow defeat the infection and get rid of the virus with no treatment could help others to do so or maybe even prevent infections. The majority of people who contract hepatitis C will live with the virus for the rest of their lives and some will develop serious liver disease including cancer.
Previous research has found that people infected with hepatitis C who carried a variation in a single chemical of DNA, the C/C variation SNP (single-nucleotide polymorphism) near their IL28B gene, are more likely to respond to hepatitis C treatment, which can rid some patients of the virus. This variation is thought to help the immune response to hepatitis C viral infection.
So researchers investigated if the C/C variation also played a role in some peoples' ability to get rid of the virus without the help of medication. To do this, they assembled information from six different studies that had over many years collected DNA and hepatitis C infection information from people all over the world. The team then analyzed DNA at the IL28B gene from a total of 1008 patients: 620 persistently infected and 388 who had been infected but who had spontaneously cleared the virus. DNA analysis revealed that of the 388 patients who no longer carried the virus, 264 have the C/C variation.
The researchers also noticed that the C/C variant does not appear equally in all populations. DNA was analyzed from more than 2300 people worldwide in order to further examine distribution of the C/C variant in different populations. Of the 428 samples from Africa, only 148 carried the C/C genotype. Of the European samples 520 out of 761 carried the C/C variant. Of the DNA samples from Asia, 738 of 824 samples carried C/C.
References:
1. David Thomas, et al. Genetic variation in IL28B and spontaneous clearance of hepatitis C virus. Nature 461, 798-801. doi:10.1038/nature08463.
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