Does allergic asthma ward off severe COVID-19? It’s complicated
Does allergic asthma ward off severe COVID-19?  It’s complicated

Does allergic asthma ward off severe COVID-19? It’s complicated

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The impact of asthma in patients developing COVID-19 has been a major scraper since the beginning of the pandemic. People with asthma and their doctors have worried that if they were infected with coronavirus, asthma could make them susceptible to serious illness.

Then some studies showed that most asthmatics have no greater risk of severe COVID-19 than the general population – and a good size population survey even suggested that they had a lower risk of hospitalization.

Now a new study reveals biological factors that may explain why. Researchers have found that a signaling molecule that exacerbates allergic asthma actually helps block the virus that causes COVID-19 from infecting airway cells in the laboratory.

Researchers showed that this cytokine, interleukin-13 (IL-13), also prevents a type of infected respiratory cell from being secreted from the airways and spreading viruses deeper into the lungs. IL-13 cytokines are known to trigger inflammation and are present in higher levels in patients with allergic asthma, which is triggered by allergens such as mold, pollen and pet dander.

“We showed that IL-13, an inflammatory marker involved in allergic asthma, reduced both the number of viruses inside a cell and the number of cells that loosen,” says senior study author Camille Ehre, PhD, an assistant professor at the University of North Carolina School of Medicine in Chapel Hill.

Lab vs. Real world

But two leading asthma and immunology experts are not convinced. Laboratory findings are often not translated into the real world, they say.

“A petri dish is vastly different from the human body,” says Dr. Mitchell Grayson, who studies viruses and is head of allergy and immunology at Nationwide Children’s Hospital in Columbus, Ohio.

Dr. Mitchell Grayson (left); Dr. James Baker

If IL-13 actually offered strong protection against coronavirus, you would expect to see fewer infections among people with allergic asthma and fewer getting sick – none of these are true, says Dr. James Baker, director of the Mary H. Weiser Food Allergy Center at the University of Michigan.

“We have not seen people with allergic asthma get fewer COVID-19 infections or have better results,” says Baker, author a blog about the pandemic. Most studies show that their risk of serious infections, he adds, is about the same as the general population.

You do not have to worry about Dupilumab

Furthermore, the case for IL-13 does not hold when one considers that biological drugs, such as dupilumab (Dupixent), inhibit IL-13. “There is no evidence that people taking dupilumab have either an increased risk of becoming infected or a higher viral [loads]or that they feel worse if they are infected, ‚ÄĚsays Grayson.

In fact one examination of researchers at the Mount Sinai School of Medicine found that patients taking dupilumab for eczema were more likely to have milder COVID-19 symptoms. And one follow-up study of these researchers found that patients on dupilumab had lower antibody levels after COVID-19 infection, indicating that they had a milder course of the disease.

Both allergy sufferers say that if you talk about dupilumab, you should definitely continue to take it, without worrying that it will increase your COVID-19 risks.

The case for the effect of IL-13

In the study, Ehre, who is also a researcher at the UNC’s Marsico Lung Institute, and her colleagues examined epithelial cell cultures from the respiratory tract infected with SARS-CoV-2, the virus that causes COVID-19.

Dr. Camille Ehre

Using a powerful electron microscope, they observed that the virus preferred to infect ciliated cells, a type of cell found in the airways. When damaged by the infection, ciliated cells form virus-filled sacs, which then fall off. After detachment, the infected cells are “then free to travel deep into the lungs while filled with viruses,” Ehre says.

“Within hours of infection, the damage can be so great that cells packed with viruses detach from the cell surfaces and turn into ticking bombs to infect either another person or another region of the lungs,” she told Allergic Living. “Such dramatic cellular events may explain the high transmissibility and high virulence of the new coronavirus.” The team’s study was published in Proceedings of the National Academy of Sciences (PNAS).

Following application of IL-13 to the infected cell cultures, Ehres’ team found reduced expression of the ACE2 protein, which has previously been shown to be a “gateway” receptor that allows SARS-CoV-2 virus to enter the lungs.

In the laboratory tests, they also found that IL-13 reduced infection in ciliated cells and there was less secretion. In addition, the researchers observed that IL-13 increased the production of an important mucus protein that traps and inactivates viruses.

These results only apply to allergic asthma, not other lung diseases or non-allergic asthma, Ehre says. Triggers of non-allergic asthma include respiratory infections, cigarette smoke, smog, exercise or stress.

Other factors at stake

Grayson and Baker warn that how a virus behaves in the human body can be affected by many, many factors.

While IL-13 can reduce the secretion of infected airway cells in a laboratory culture, to see the same effects in humans, you may need much higher levels of IL-13 than anyone actually has, Grayson says.

Other factors that can affect how sick people become of COVID-19 include their age, body mass index (BMI), and whether they have other disorders, such as diabetes, which have been linked to a higher risk of severe COVID-19 disease.

In addition, people with allergic asthma often take inhaled corticosteroids, which Baker notes are also used as COVID-19 treatment. In these patients, he says, the steroids may be what prevents hospitalization, not their IL-13.

Bottom line for people with allergic asthma? Do not be complacent, experts say.

People with allergic asthma should complete their COVID-19 vaccinations if they have not already done so, Baker says. Also take your medication as prescribed to make sure that your asthma is under control and that lung function is as good as it can be.

“We are approaching one million people in the United States who are dying of COVID,” Baker says. “We can not just assume that some form of inflammatory cytokine will prevent the infection.”

Related reading:
COVID-19 vaccines: How to tell an allergic reaction to a side effect
Study finds COVID-19 shots safe for most people with PEG allergy
Additional inhaler strategy reduces asthma attacks for black, Hispanic adults


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