Monday, March 26, 2012

Genetics predict severity of the flu

The influenza virus comes in many forms, and is constantly changing. As a consequence, the world experiences new outbreaks of the flu each year. Our immune system builds up protection against the virus after infection, but because it changes its appearance so rapidly, we become susceptible again. It has been proven difficult to find a vaccine that remains effective in protecting against influenza infection, but our own body may actually hold clues for effective flu protection. Scientists from the Wellcome Trust Sanger Institute have found how the activity of a specific gene correlates to severity of influenza infection. We may use this mechanism in future therapies.

By performing genetic screening on patients hospitalized with the flu, the scientists discovered a relationship between a gene called IFITM3 and severity of their disease. It appears that a mutant version of the gene renders the corresponding IFITM3 protein unable to function properly. The scientists found that patients with a mutant version are more likely to die from the flu. A simple correlation does however not tell us how this works, but the scientists had already done some lab work.

Mice also possess IFITM3, and when the scientists created a genetically modified mouse that lacks the gene, they were able to show that it makes a mild influenza infection go bad once the virus manages to infect the animal. Therefore, it appears that the protein produced by the IFITM3 gene acts as a defence mechanism once the virus is inside. It can make the difference between effectively holding back the threat, or succumbing to disease. Previous studies have already shown IFITM3 can deny viruses entry into a cell, thereby limiting its spread, providing a biological mechanism for the observations.

According to the scientists, it is the first time a genetic component has been linked to successfully fighting off influenza. It reveals why some people only experience mild symptoms, while the infection is fatal to others. The findings are important, because it may tell us something about who is at risk when a new flu epidemic rears its head. By learning more about how IFITM3 works, we may also be able to develop new anti-flu therapies. If we can artificially increase IFITM3 protein level or produce drugs with similar features, flu deaths could be decreased dramatically. Creating such a therapy from scratch will take years, however. Perhaps we should expect more from treatments already in development, such as the use of anti-cholesterol drugs which appear to be useful for reducing flu deaths, or a new class of drugs that aids the immune system.
A typical influenza virus:H5N1. Named after the proteins on the viral surface: H5 and N1.

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