The Colder the Better for the Common Cold
Have you ever wondered why wintery weather brings on the sniffles? A new study published in Proceedings of the National Academy of Sciences has found that the common cold prefers cold noses, which may partly explain why colds commonly occur when it’s, well, cold.
Rhinovirus, the pesky source of colds and asthma exacerbations, thrives at the cooler temperature of 33-350C found in the nose, whereas virus replication is reduced at a core body heat of 370C. Dr Akiko Iwasaki and colleagues at Yale University have now shown that this is down to reduced immune function in cells at cooler temperatures.
The researchers challenged mouse airway epithelial cells with a specifically adapted rhinovirus at 330C and 370C. They then compared gene expression levels in these cells, and found that the transcription of important proteins involved in the immune response was reduced at the lower temperature. Epithelial cells in the colder condition had dramatically lower expression levels of interferon (IFN) and IFN-stimulated genes, which code for important proteins involved in anti-viral functions and modulation of the immune system.
Since rhinovirus strains are happier in cells lining the colder nasal cavity, this may explain why this virus does not infect warmer areas of our airways such as the lungs, where viruses such as influenza can cause more severe illness.
Dr Iwasaki warned that while ” the lower the temperature…the lower the innate immune response to viruses”, this is not necessarily the answer to why we tend to get colds when it’s chilly, since multiple other factors make it “much more complicated”. Nevertheless, as January sets in, maintaining a toasty nose may help to keep those sniffles at bay…
Foxman, E.F., Storer, J.A., Fitzgerald, M.E., Wasik, B.R., Hou, L., Zhao, H., Turner, P., Pyle, A.M. and Iwasaki, A (2015) Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells. PNAS doi: 10.1073/pnas.1411030112
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