Does allergic asthma resist severe COVID-19? It is complicated

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The impact of asthma in patients who develop COVID-19 has been a puzzle since the start of the pandemic. People with asthma and their doctors fear that if they catch the coronavirus, the asthma will leave them vulnerable to serious illness.

Then some research showed that most asthmatics weren’t at a higher risk of severe COVID-19 than the general population – and one good-size population study even suggested they had a lower risk of hospitalization. .

Now, a new study uncovers biological factors that may explain why. Researchers have found that a signaling molecule that worsens allergic asthma actually helps prevent the virus responsible for infecting respiratory cells with COVID-19 in the laboratory.

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

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

Laboratory vs. Real world

But two leading experts in asthma and immunology aren’t convinced. Lab results often don’t translate to the real world, they say.

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

Dr. Mitchell Grayson (left); Dr James Baker

If IL-13 did indeed offer potent protection against coronavirus, you’d expect to see fewer infections in people with allergic asthma and fewer illnesses – which isn’t true, says Dr James Baker , director of the Mary H. Weiser Food Allergy Center at the University of Michigan.

“We haven’t seen people with allergic asthma get fewer COVID-19 infections or have better outcomes,” says Baker, who blogged about the pandemic. Most studies show that their risk of serious infections, he adds, is about the same as that of the general population.

Don’t worry about dupilumab

Additionally, the case for IL-13 does not hold when considering that biologic drugs, such as dupilumab (Dupixent), inhibit IL-13. “There is no suggestion that people taking dupilumab have either an increased risk of being infected or a higher viral load.” [loads]or that they do worse if they get infected,” Grayson says.

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

The two allergists say that if you’re talking about dupilumab, you should absolutely keep taking it, without fear that it will increase your risk of COVID-19.

The case for the IL-13 effect

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

Dr. Camille Ehre

Using a powerful electron microscope, they observed that the virus preferentially infects hair cells, a type of cell found in the respiratory tract. When damaged by infection, the hair cells form virus-filled sacs, which then break off. After breaking away, the infected cells “are then free to travel deep into the lungs while being loaded with virus,” says Ehre.

“Within hours of infection, the damage can be so extensive that virus-packed cells break off from cell surfaces and become ticking time bombs to infect another person or another region of the lungs,” she said. told Allergic Living. “Such dramatic cellular events may explain the high transmissibility and high virulence of the novel coronavirus.” The team’s study was published in the Proceedings of the National Academy of Sciences (PNAS).

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

In lab tests, they also found that IL-13 reduced infection in hair cells and there was less shedding. Additionally, the researchers observed that IL-13 increased the production of an important mucus protein that traps and deactivates viruses.

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

Other factors at play

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

While IL-13 can reduce the shedding of infected respiratory cells in a lab culture, to see the same effects in humans, you might need much higher levels of IL-13 than we would. really, says Grayson.

Other factors that can influence how sick people get from COVID-19 include their age, body mass index (BMI) and whether they have other conditions, such as diabetes, which has been linked to a higher risk of serious illness from COVID-19.

Additionally, people with allergic asthma often take inhaled corticosteroids, which Baker says are also used as a COVID-19 treatment. In these patients, he says the steroids might be what’s preventing hospitalization, not their IL-13.

In summary for people with allergic asthma? Don’t be complacent, experts say.

People with allergic asthma should complete their COVID-19 vaccinations if they haven’t already, Baker says. Also, take your medications as prescribed to ensure your asthma is controlled and lung function is as good as possible.

“We’re getting closer to a million people in the United States dying from COVID,” Baker says. “We can’t just assume that some type of inflammatory cytokine will prevent infection.”

Related reading:
COVID-19 vaccines: How to distinguish an allergic reaction from a side effect
Study finds COVID-19 safe for most people with PEG allergy
Supplemental inhaler strategy reduces asthma attacks in black and Hispanic adults

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