February 20, 2013
Biological Markers In Chromosomes Predict The Common Cold
[Watch Video: Biological Marker Predicts Susceptibility To Common Cold]
Lawrence LeBlond for redOrbit.com - Your Universe Online
While predicting future events has been met with much skepticism, many scientists make it their life work to predict what will happen in the future. Such predictions include what regional weather will be like, how much warmer the planet will be, and even when the Sun will die.
But predictive science is not limited to just forecasting the weather or projecting climate shifts. Now, researchers may be able to predict which people will become infected by viruses based on certain biological markers found in their chromosomes.
Scientists from Carnegie Mellon University (CMU) have recently discovered that our susceptibility to infections and our future health may be foretold by chromosome tips, known as telomeres. These chromosome tips are special DNA sequences that prevent DNA in chromosomes from unraveling. Telomeres get shorter and shorter each time a cell divides, and eventually die once cells can no longer divide.
The researchers, led by Carnegie Mellon´s Sheldon Cohen, found that these biological markers in the immune system can predict our ability to fight off infections such as the common cold. This predictive process, however, doesn´t begin until we reach the age of about 22 years old, the authors note.
Publishing the study findings in today´s issue of JAMA, Cohen and his colleagues found that people who have the shortest telomeres caught more colds and were less likely to stave off infection than those who had the longest telomeres. They said that telomeres affect people at all stages of life, but as we age, these biomarkers lose their ability to function and eventually get shorter and die.
The team found that having shorter telomeres is associated with early onset of age-related diseases such as cancer and cardiovascular disease, and with mortality in older adults. Prior to this study, it was not known if the length of these biomarkers played a role in the health of young to midlife adults.
Cohen, the Robert E. Doherty Professor of Psychology in CMU's Dietrich College of Humanities and Social Sciences, suggests that “telomere length is a relatively consistent marker across the life span and that it can start predicting disease susceptibility in young adulthood.”
"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,” Cohen said in a statement.
For their study, Cohen and his team measured the length of telomeres found on the chromosomes of 152 healthy volunteers between the ages of 18 and 55. The authors exposed each of these individuals to rhinovirus, which causes the common cold, and quarantined them for five days to see if they developed an infection.
They discovered that the participants who had shorter telomeres were more likely to become infected by the cold virus. They also discovered that there was no relationship between telomere length and infection in the youngest participants (18-21) in the study. But at about the age of 22, telomere length started to predict whether individuals would develop an infection or not.
They found that as a participant´s age increased, telomere length became an even stronger predictor. Of all telomere biomarkers studied, one particular white blood cell type–a CD8CD28-T cytolytic cell–was far superior in predicting infection and cold symptoms than other cell types. The study authors found that the CD8CD28-cells shortened more quickly than the others, and previous research found that telomere lengths in these cells are associated with decreases of immune competence.
"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," 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."
Cohen said this is one of the first studies to look at telomeres in younger adults.
“There is growing evidence that this is an aging biomarker that may have implications for health and well-being over our life course,” Cohen told Nicole Ostrow of Bloomberg.
In all, nearly 70 percent of the study´s participants showed signs of infection with rhinovirus, based on a blood test. However, only 22 percent of those people went on to actually develop a verified infection along with cold symptoms.
If the findings can be duplicated in future research, it is likely to mean that telomere length may also help predict who needs extra protection from vaccines and medications to reduce the risk of disease, according to Elissa Epel, a study author and associate professor in the Department of Psychology at UCSF.
However, it is still unclear whether or not knowing telomere length is helpful, she said.
Epel, a founding member of Telomere Health Inc., a company that provides telomere length data to doctors and others, said: “There is a lot of hype around telomere length, because it appears to be a stronger risk factor for early disease and mortality than traditional risk factors“¦ It also tends to predict the range of diseases of aging, not just cardiovascular disease. But essentially it is just like cholesterol in that it is a risk factor that is partly inherited, partly determined by lifestyle and is malleable.”
Aaron Glatt, a spokesman for the Infectious Diseases Society of America (IDSA), told USA Today´s Liz Szabo that Cohen´s study won´t change how patients are diagnosed or treated. "It has zero practical ramifications.”
But James Crowe, a professor at Vanderbilt University Medical Center in Nashville who wasn't involved in the new study, said that many people, including doctors, are interested in finding out "why some people get infected with colds and some don't. Two seemingly healthy people might be side by side, and one gets infected and one doesn't."
This study is "provocative because it comes out of left field," Crowe told USA Today. However, he agrees that the study is too preliminary to be convincing, noting it was too small of a study to “make such a profound discovery.”
"It's not a validated study, but it's unusual and interesting, and it needs to be followed up. That's how science works. We get many ideas, and many of them don't pan out," he added.