Cooler temperatures inside the nose may dull the body’s ability to fight the common cold, a new study finds. This might explain why colds are more common in winter.
The common cold virus is called the rhinovirus. (Rhino comes from the Greek word for “nose.”) Scientists long have known that the rhinovirus replicates — makes copies of itself — better in the relative cool of the nose than in the warmer lungs. Why that’s true had not been entirely clear.
The nose’s temperature is to blame, Ellen Foxman of Yale University in New Haven, Conn., and her colleagues conclude. They studied a version of the rhinovirus that had been adapted to growing in mouse cells that line the airways. Those cells, they now report, did a poorer job defending against the cold virus at the nose’s temperature of 33° Celsius (or 91.4° Fahrenheit) than at the animal’s normal core body temperature of 37 °C (98.6 °F).
The infected mouse cells produced fewer of the molecules, such as interferon, that the body releases to fight a viral infection, the experts found. Details appeared in January 5 issue of the Proceedings of the National Academy of Sciences.
interferon A protein released by cells when exposed to a virus. It defends the body against infection by inhibiting the ability of a virus to reproduce.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
replicate (in biology) To copy something. When viruses make new copies of themselves — essentially reproducing — this process is called replication.
simulate To deceive in some way by imitating the form or function of something. A simulated dietary fat, for instance, may deceive the mouth that it has tasted a real fat because it has the same feel on the tongue — without having any calories. A simulated sense of touch may fool the brain into thinking a finger has touched something even though a hand may no longer exists and has been replaced by a synthetic limb. (in computing) To try and imitate the conditions, functions or appearance of something. Computer programs that do this are referred to as simulations.
virus Tiny infectious agents consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.
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Learn more about the common cold from the National Institutes of Health: http://www.nlm.nih.gov/medlineplus/ency/article/000678.htm
Original journal source: E. F. Foxman et al. Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells. Proceedings of the National Academy of Sciences. January 5, 2014. doi: 10.1073/pnas.1411030112.