a protective effect against asthma?

People with asthma would be protected against severe forms of Covid-19. This paradox was explained by scientists in a recent publication in the journal PNAS. Indeed, it appears that asthmatics form a double barrier against infection by SARS-CoV-2. It would be combined by the overproduction of mucus and protection by anti-inflammatory molecules that are overrepresented in asthmatics. On this World Asthma Day, Health on the net explains these results.

Asthma and Covid-19, false friends?

Covid-19, a respiratory attack

For more than 2 years, the pandemic COVID-19 has prompted doctors and scientists to dissect this pathology from its mechanisms to its symptoms. Although it takes various forms, we currently know that Covid-19 is generally manifested by:

  • Fever ;
  • Muscle aches such as body aches;
  • headache;
  • Fatigue;
  • Damage to the respiratory tract that can lead to respiratory distress.

Asthma, a chronic respiratory disease

This one world dayasthma is an opportunity to make the general public aware of this pathology that affects more than 4 million people in France. Asthma is a chronic respiratory disease caused by permanent inflammation of the airways. It is manifested by episodes of difficulty breathing (shortness of breath).

Asthma is multifactorial. Indeed, in the case of allergic asthma, it is activated in the presence of an allergen such as pollen or mold. The presence of the allergen triggers a cascade of chemical phenomena. For example, it activates the production of cytokines and mucus in the lungs of patients.

Know ! The cytokines are chemical messengers of different nature. In the case of allergic asthma, it is interleukins 13 (IL-13), anti-inflammatory cytokines, which are overexpressed. They cause an overproduction of slime by lung cells.

On paper, everything suggested that people with asthma would be patients at risk for a severe form of Covid-19. But, it’s nothing. Epidemiological studies have not shown an association between asthma and a greater risk of a severe form of Covid-19. Except patients with severe asthma (5% of the asthmatic population). On the contrary, researchers have shown that especially people with asthmaallergic asthmawould be protected against SARS-CoV-2 infection.

Asthma against Covid-19: a physical barrier formed by mucus

In a recently published study, the researchers wanted to explain the paradox of a possible protection against severe forms of Covid-19 by asthma. To do this, they imitated allergic asthma on lung cells, by putting them in the presence of IL-13. Then they infected them with SARS-CoV-2.

The results of the study highlight that allergic asthma offers two types of protection against Covid-19. indeed, the excessive mucus production forms a physical barrier by asthmatic lung cells that limits SARS-CoV-2 infection. Cells not treated with IL-13 also produced mucus during SARS-CoV-2 infection, but were quickly overwhelmed by virus multiplication.

A chemical barrier thanks to anti-inflammatory cytokines

To go further, the researchers then treated the lung cells with IL-13 but blocked the mucus production. They noted that the treated cells had a lower viral load than the cells not treated with IL-13. This can be explained in two ways.

On the one hand, IL-13 reduces the production of receptors that allow SARS-CoV-2 to enter lung cells. Thereby, the virus has much more difficult access to the cells† On the other hand, infected cells lacking IL-13 produce SARS-CoV-2 virions that facilitate the contamination of neighboring cells. The mechanisms elucidated in this study thus allow a significant reduction in virus ingress in the lung cells, of his replication And his scatter to other cells.

Alexia F., Doctor of Neuroscience


– SARS-CoV-2 infection of respiratory tract cells causes intense viral and cell secretion, two distribution mechanisms affected by IL-13. pnas.org. Retrieved May 3, 2022.
– Why are people with allergic asthma less susceptible to severe COVID? sciencedaily.com. Accessed May 3, 2022

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