Shorter telomeres associated with decreased upper respiratory infection resistance

Friday, February 22, 2013. The February 20, 2013 issue of the Journal of the American Medical Association (JAMA) reports an association between decreased telomere length and greater susceptibility to the common cold. Telomeres are DNA complexes at the end of the chromosomes which shorten with repeated cell division, leading to cell senescence and impaired function. Reduced telomere length has also been associated with whole system aging-related conditions, including cardiovascular and infectious diseases.

"Our work suggests the possibility that telomere length is a relatively consistent marker across the life span and that it can start predicting disease susceptibility in young adulthood," stated lead researcher Sheldon Cohen, who is the Robert E. Doherty Professor of Psychology at Carnegie Mellon University's Dietrich College of Humanities and Social Sciences. "We knew that people in their late 50s and older with shorter telomeres are at a greater risk for illness and mortality. We also knew that factors other than aging, such as chronic stress and poor health behaviors, are associated with shorter telomeres in older people. Consequently, we expected that younger people would vary in their telomere length as well and wanted to see what this would mean for their health."

The current study included 152 men and women between the ages of 18 to 55 years. Blood samples were analyzed for telomere length of four types of leukocytes (white blood cells), and participants were quarantined for six days. Nasal drops containing a rhinovirus were administered after the first 24 hours of quarantine, and the subjects were monitored for the remaining period.

Sixty-nine percent of the participants were determined to have been infected with the virus and clinical illness developed in 22 percent. Beginning at an approximate age of 22, shorter telomere length of any of the white blood cell types examined was associated with a greater risk of infection, with the risk increasing with greater age. "The increased importance of telomere length with age is likely because the younger participants had fewer very short telomeres, or that their young immune systems were able to compensate for the loss of effective cells," Dr Cohen commented.

A variety of white blood cell known as CD8CD28- was found to be the type of leukocyte in which decreased telomere length was associated with a significant increase in the risk of clinical illness. For those whose CD8CD28- cells had the shortest telomeres, the rate of clinical illness was twice that of subjects whose telomere length was longest. "These cells are important in eliminating infected cells and those with shorter telomeres in the CD8CD28- cell population may be at greater risk for infection because they have fewer functional cells available to respond to the virus," Dr Cohen said. "The superior ability of CD8CD28- T-cytolytic cells to predict infection gives us an idea of which cells to focus on in future work on how telomere length influences the immune system's response to infection and other immune-related challenges."

"This is preliminary research and further work with other viruses and with natural infections will help clarify its implications," he added.