Science

A warm nose helps fight colds better

As you know, the arrival of winter always rhymes with the cold season.

Factors favoring these common respiratory infections include more indoor gatherings and viruses that survive better in the drier air between four walls. But as to whether low temperatures really weaken our immune systems (and if so, how), there is less certainty.

The study, published Tuesday in the Journal of Allergy and Clinical Immunology, details a new way our bodies attack intruders. And this method works best in warm weather.

These discoveries could lead to the development of new treatments for the common cold and other viruses, Mansoor Amidji, a professor at Northeastern University and co-author of the paper, told AFP.

The starting point is a previous study he did in 2018, which showed that cells in the nose secrete extracellular vesicles (EVs), a cloud of tiny particles that attack bacteria when inhaled.

“The best analogy is a hornet’s nest,” explains Mansour Amidji. Like hornets defending nests when attacked, EVs fly in flocks to attach themselves to invaders and kill them.

The researchers then asked themselves two questions: Are EVs secreted in the presence of a virus? And if so, does temperature affect their response?

For their tests, scientists used the nasal mucosa of volunteers (who underwent surgery to remove polyps) and a substance that reproduces a viral infection.

Result: electric vehicles resist viruses well.

– “First plausible explanation” –

To answer the second question, the nasal mucosa were divided into two groups, with cells cultured in the laboratory at either 37°C or 32°C.

These temperatures were chosen based on tests showing that the temperature inside the nose drops by about 5°C when the outside air temperature drops from 23°C to 4°C.

Under conditions of normal body temperature, electric vehicles were able to fight viruses well by providing them with “baits” that they clung to, instead of the cell receptors they would normally target.

But at lower temperatures, the production of EVs was less abundant, and they were less effective against the tested viruses: two rhinoviruses and a coronavirus (not covid), common in winter.

“There has never been a very compelling reason why there is a clear increase in viral infectivity during the cold months,” said Benjamin Blayer, study co-author and surgeon at Harvard Medical School. “This is the first quantitatively and biologically plausible explanation that has been developed.”

This work could lead to the development of treatments that stimulate the natural production of electric vehicles to better fight the common cold, or even the flu and Covid-19, according to Mansour Amidji. “This is an area of ​​research that interests us extremely, and we will certainly continue on this path.”

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