It is well known, the arrival of winter always rhymes with cold season.
Among the factors favoring these common respiratory infections: more frequent gatherings indoors and viruses surviving better in the drier air between four walls. But as to whether low temperatures actually weaken our immune system (and if so how), there is less certainty.
A 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 Amiji, a professor at Northeastern University and co-author of this work, told AFP.
The starting point is a previous study he conducted in 2018, which found that cells in the nose release extracellular vesicles (EVs) — a cloud of tiny particles that attack bacteria upon inhalation.
“The best analogy is that of the hornet’s nest,” explains Mansoor Amiji. Like hornets defending a nest when attacked, VEs fly in swarms to attach to invaders and kill them.
The researchers then asked themselves two questions: are EVs also secreted in the presence of a virus? And if so, is their response affected by temperature?
For their tests, the scientists used the nasal mucosa of volunteers (who were undergoing an operation to remove polyps), and a substance reproducing a viral infection.
Result: EVs are well produced against viruses.
To answer the second question, the nasal mucous membranes were divided into two groups, with the 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 about 5°C when the outside air drops from 23°C to 4°C.
Under normal body temperature conditions, the EVs managed to fight the viruses well, by presenting them with “decoys” to which they clung, instead of the receptors of the cells that they would normally have targeted.
But with a reduced temperature, the production of EV was less abundant, and they proved to be less effective against the viruses tested: two rhinoviruses and a coronavirus (non-COVID), common during the winter.
“There has never been a very compelling reason why there is a clear increase in viral infectivity during the colder months,” Benjamin Bleier, study co-author and Harvard surgeon, said in a statement. Medical School. “This is the first quantitatively and biologically plausible explanation that has been developed.”
This work could lead to the development of treatments to stimulate the natural production of EV, so that we can better fight colds – or even the flu and COVID-19, according to Mansoor Amiji. “This is an area of research that interests us enormously, and we will undoubtedly continue on this path.”