Over 70% of the U.S. population suffers from herpes (Herpes simplex labialis – HSL) caused by the herpes simplex virus type 1 (HSV-1), which is characterized by cold sores on or around the mouth. Once infected, the virus is never removed by the immune system and lies dormant in the body’s nerve cells until reactivated. Even though the majority of people are infected with HSV-1, the frequency of cold sore outbreaks varies tremendously and it is not known what causes reactivation.

According to a study published in the Dec.1, 2011 issue of the Journal of Infectious Diseases, researchers from the University of Utah and the University of Massachusetts have now identified the first gene linked to frequent herpes-related cold sores.

Dr John D. Kriesel, research associate professor of infectious diseases at the University of Utah School of Medicine and leading author of the study says:

“Researchers believe that three factors contribute to HSV-1 reactivation – the virus itself, exposure to environmental factors, and genetic susceptibility. The goal of our investigation was to define genes linked to cold sore frequency.”

In an earlier study, Kriesel and his team mapped the human genome from DNA collected from 43 large families and identified a region of chromosome 21 containing six genes with an important association to HSL disease. In this study, Kriesel and his team carried out an intensive examination of this chromosome region by using single nucleotide polymorphism (SNP) genotyping. SNP genotyping is a test that detects genetic make-up variations between individuals.

Kriesel explains:

“Using SNP genotyping, we were able to identify 45 DNA sequence variations among 618 study participants, 355 of whom were known to be infected with HSV-1. We then used two methods called linkage analysis and transmission disequilibrium testing to determine if there was a genetic association between particular DNA sequence variations and the likelihood of having frequent cold sore outbreaks.”

They discovered a link between an obscure gene called C21orf91 and susceptibility to HSL. They also observed that C21orf91 has five major variations. Two variations appear to protect against HSV-1 reactivation and two seemed to increase the chance of having frequent cold sore outbreaks.

Kriesel concludes:

“There is no cure for HSV-1 and, at this time, there is no way for us to predict or prevent cold sore outbreaks. The C21orf91 gene seems to play a role in cold sore susceptibility, and if this data is confirmed among a larger, unrelated population, this discovery could have important implications for the development of drugs that affect cold sore frequency.”

Written by Petra Rattue