Painful and embarrassing, cold sores are unpleasant at best. Cold sores are caused by the herpes simplex virus 1 (HSV1), a non-lethal and mostly harmless virus. Approximately 90% of adults carry the virus, most infected as children through a kiss from a relative or family friend with a sore. However, only a small percentage of those with the virus suffer frequent outbreaks.

Photo by REX/CDC/Phanie (678829l)
Electron micrograph of the Herpes simplex virus.
Microscopic images

Once the virus is contracted, it hangs around in the nerve cells for life, dormant until activated by sunlight, stress, illness, trauma to the area, or other factors. Just because there are no symptoms doesn’t mean the virus is gone, it just means the immune system is keeping it under control.

Now scientists are beginning to understand why some people can carry the virus and rarely or never get a cold sore, while others seem to get them all the time. The key is a protein produced by the immune system called interferon-lambda. The name refers to the fact that it works by interfering with the ability of the virus to replicate.

Scientists compared the DNA of people who suffer from frequent cold sores with individuals with the virus who rarely or never experience outbreaks. What they found was that the gene responsible for producing interferon-lambda is flawed in those who are more vulnerable. This flawed gene meant that those individuals are unable to make sufficient amounts of the protein to keep HSV1 under control.

HSV1 is classified as neurotropic, meaning that it specifically infects nerve cells. In doing so, it uses the blood-brain barrier to avoid most elements of the immune system. This is how it is able to lay dormant in the body forever.

As annoying as they are, cold sores are relatively harmless and easily treated, so it’s not expected that this discovery will be used to treat them. However, scientists do hope that new, more effective treatments may be developed for serious complications, including infection and encephalitis.

Just as important as the potential applications of interferon-lambda for treating HSV1 complications, this discovery highlights the importance of studying not only the pathogens that cause illness, but what genetic factors make some people vulnerable to infection while others fight them off with ease.

For now at least, the only way to manage HSV1 infection is to avoid triggers and treat outbreaks as they occur.