How people who suffer from cold sores lack key protein that keeps virus under control

Cold sores are caused by HSV1 virus - which almost everybody carries



But most people produce a vital protein which keeps the illness at bay



Scientists at Edinburgh University found around a quarter of people produce less of the protein - and so suffer more cold sores



Scientists discovered that a special protein helps fight back cold sores - and that people who lack the protein are much more vulnerable

Scientists have put their finger on why some people are plagued by unsightly cold sores.



They’ve shown that people who get cold sore after cold sore don’t make enough of a protein that keeps the virus under control.



The insight could lead to new treatments for the potentially fatal complications of the extremely common bug.



It has long been known that by adulthood, most people are infected with the cold sore-causing herpes simplex virus type 1 bug.



However, while up to 90 per cent of adults have HSV-1 lurking in their system, only around a quarter of them will experience frequent outbreaks.



Now, Edinburgh University scientists have discovered why.



They began by looking at how cold sores – fluid-filled crusty blisters that occur around the mouth - occur.



The HSV-1 bug is usually caught in childhood and often through a kiss from a family member or friend with a cold sore.



It passes through the skin and travels up a nerve, where it lies inactive until stress, sunlight, illness or another trigger, awakens it and leads to cold sores forming.



By analysing thousands of genes, the researchers found one that makes a protein called Interferon-lambda that helps keep the virus from being reactivated.



They then compared the DNA of people who regularly got cold sores with that of people who had the virus but were rarely troubled by it.



In those who often got cold sores, the gene for Interferon-lambda tended to be flawed, meaning they made less of the protein.



This left their immune system unable to keep the bug under control and meant they were plagued by cold sores.



Overall, around a quarter of Britons have the genetic flaw that makes them prone to cold sores, the journal PLoS Pathogens reports.

Cold sores are caused by the HSV1 virus (pictured), which almost everyone carries. But most of the time our bodies can fight the illness off.

Researcher Professor Juergen Haas said the finding shows the importance of studying the person that is infected, as well as the infection itself.



'Most people carry the cold sore strain of the herpes simplex virus but until now we never knew why only some of them develop cold sores.



'Knowing that susceptibility to the virus involved relates to people’s genes reinforces the need to research, not only the evolution of the viruses themselves, but the susceptibility of the hosts to infection.'



The professor’s discovery could lead to Interferon-lamba being used as a treatment for HSV-1.



The risk of side-effects means it is not likely to be used on cold sores, which despite looking unsightly usually clear up without treatment.



However, it could be used to improve treatment of rare but potentially fatal side-effects of the virus, including infections and swelling of the brain.



Professor Haas said: 'HSV-1 belongs to a family of viruses that persists in the body for life. Once you are infected, usually as a child, it persists in the nerve cells. You cannot really get rid of it.