Cold coddles colds

Chilly winter weather alone may not cause colds, but the cold weather may numb the body’s ability to fight off cold viruses, a new study suggests.

Rhinovirus, also known as the common cold virus, has long been known to grow better in the nasal passages than in the lungs, but the reason wasn’t entirely clear. Now, Ellen Foxman of Yale University and colleagues find that the virus-fighting signals given off by infected host cells don’t raise as much of an alarm at 33° Celsius, the temperature in the nose, as they do at the core body temperature of 37° C.

Using a version of rhinovirus adapted to grow in mouse cells, Foxman and colleagues discovered that infected mouse airway cells produced less interferon — one of the body’s antiviral defense molecules —  when grown at nose temperature than they do when grown at the lungs’ core body temperature. A molecule called the RIG-I-like receptor, which normally helps spread the word about the infection and activate the body’s defense system, also doesn’t work as well at cooler temperatures, the researchers report January 5 in the Proceedings of the National Academy of Sciences.

These findings could mean that inhaling cold air represses the ability of cells lining the nasal passages to fight off cold viruses.