Biological Marker Predicts Susceptibility to Common Cold

A biological marker in the immune system beginning at about age 22 predicts our ability to fight off the common cold.

A team led by Carnegie Mellon University's (CMU; Pittsburgh. PA, USA) Prof. Sheldon Cohen, found that the length of telomeres—protective cap-like protein complexes at the ends of chromosomes—predicts resistance to upper respiratory infections in young and midlife adults. Telomere length is a biomarker of aging that shortens as a person gets older. As a cell's telomeres shorten, it loses its ability to function normally and eventually dies. Having shorter telomeres is associated with early onset of age-related diseases such as cardiovascular disease and cancer, and with mortality in older adults. It has not been clear until now whether telomere length plays a role in the health of young to midlife adults.

Prof. Cohen and his team measured the telomere length of white blood cells from 152 healthy volunteers aged 18–55. These individuals were then exposed to a rhinovirus, which causes a common cold, and quarantined for five days to see if they actually developed an infection.

The results showed that participants with shorter telomeres were more likely to become infected by the cold virus. In addition, although there was no relationship between telomere length and infection among the youngest participants (ages 18–21), beginning at about age 22, telomere length started to predict whether individuals would develop an infection. As participant age increased, telomere length became an even stronger predictor. Additionally, telomere length of a specific type of white blood cell—a CD8CD28- T-cytolytic cell was a superior predictor of infection and cold symptoms than other white blood cell types. The telomeres found that CD8CD28- cells shorten more quickly than those found in other cell types, and previous work has found shorter telomere length in these cells to be associated with decreases in markers of immune competence.

Prof. Cohen explained, "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."

"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 [cold] virus," Prof 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."

Prof. Cohen emphasized that the team's work was preliminary and that further work with other virus and natural infections is necessary.

The study was published in the February 14, 2013, Journal of the American Medical Association (JAMA).

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