Why some people have a cold more often

Detrimental environmental effects make it difficult to ward off viruses in the respiratory tract

Why are some people more prone to colds than others? © Vladans / istock
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While one constantly sniffs and coughs, the other almost never falls ill: researchers have now discovered a possible explanation for this phenomenon. Their experiments show that cells in different areas of the respiratory system do not just treat each other differently with cold viruses. They are also quickly overwhelmed when added at the same time a second threat. For this reason, for example, smokers are more susceptible to colds than non-smokers.

Runny nose, sneezing, throat scratching: The common cold has probably caught everyone once before. Responsible for this annoying suffering may be a variety of viruses - especially representatives of the so-called rhinoviruses. If the pathogens infect our respiratory system, they sometimes trigger unpleasant and in extreme cases even severe disease symptoms. In many cases, our immune system will kill the pathogens before we even notice anything about the infection.

But why do the common cold viruses put some people out of action on a regular basis, while others almost never get sick? Scientists led by Valia Mihaylova at Yale University, New Haven, have now investigated how such different disease histories can be explained.

Attack on the respiratory tract

For their study, they examined epithelial cells from the nasal passage and lungs of healthy people. These cells are the body's first line of defense against potentially dangerous airway intruders. How would they react if they came into contact with rhinoviruses? It revealed that although both cell types were exposed to identical conditions in the experiment, they did not show the same behavior.

For example, the researchers observed a much stronger antiviral response in the cells from the nose - this is also the place where the pathogens typically begin their airway conquest. However, further investigations have shown that nasal and lung cells obviously set different priorities in the case of a rhinovirus infection. Although the antiviral response was increased in the nose, the cells in the lungs effectively prevented oxidative stress. This form of cell stress can be triggered by viruses, but also by cigarette smoke or pollen. display

Either-or decision

But why do not both cell types equally rely on both the antiviral and antioxidant strategies? Apparently, because they have to choose one of them. As the scientists observed, the defense response to oxidative stress largely eliminates antiviral defense mechanisms.

To further investigate this relationship, the team doused the nasal cells with cigarette smoke - causing oxidative stress - and immediately infected them with rhinoviruses. The result: Compared to the first experiment, the cells coped significantly worse with the virus attack. "Although they survived the cigarette smoke, they were not able to effectively fight the pathogen, " says Mihaylova's colleague Ellen Foxman.

Greater susceptibility

These results underscore how sensitive the balance between the different defense mechanisms of our bodies is - and that cells have different emphases in defense depending on their place of origin. Certain environmental impacts may shift the customized defense response in one direction or the other, but this involves costs.

"The respiratory system protects us from pathogens and other harmful substances and they do it well as long as they are dealing with just one stressor. On the other hand, with two stressors at the same time, they have to compromise, "says Foxman. "Although they can adapt to a different type of stress, they pay for it with a greater susceptibility to other harmful influences - such as rhinoviruses."

Smokers are more sensitive

It seems that there is a connection between certain environmental influences and the individual's risk of catching a cold. According to the researchers, this could also explain why smokers are often more sensitive to rhinovirus infections and more susceptible to colds and co-ops than nonsmokers. (Cell Reports, 2018; doi: 10.1016 / j.celrep.2018.08.033)

(Yale University, 12.09.2018 - DAL)