Researchers at Karolinska Institutet and Danderyd Hospital have identified antibodies against influenza, covid-19 and RSV in exhaled breath, according to News55. The finding, published in the journal eBioMedicine, points to a possible alternative to the more invasive procedures currently used to sample the deeper airways.
The work centres on a method called PExA — Particles in Exhaled Air — in which a person breathes into a device that captures tiny particles carried up from the smallest airways in the lungs. Participants were drawn from the COMMUNITY study at Danderyd Hospital.
Why it matters
How effectively a virus is stopped in the respiratory tract depends in part on antibodies present in the mucous membranes. In the nose, these antibodies can be measured with simple swabs. Further down in the lungs, however, sampling has generally required bronchoscopy, a procedure in which an instrument is passed into the airways.
The new results suggest that step may not always be necessary. If the approach holds up in larger studies, it could give researchers a far easier way to observe local immune activity in the lungs — and to do so repeatedly in the same person.
What the study found
Of the 28 participants, 18 had recently experienced a respiratory infection. The researchers collected samples from blood, the nose and exhaled air.
In the air coming from the small airways, they detected antibodies of the IgA and IgG types. Levels of IgG in the lungs largely tracked the levels found in the blood. IgA, by contrast, appears to be produced to a significant degree locally in the respiratory tract.
For participants, the sampling itself was undemanding. "They only need to breathe into an instrument," said Katherina Aguilera, a doctoral student and the study's first author, according to News55. That simplicity is what makes repeated sampling feasible, allowing the immune response to be followed over time.
Charlotte Thålin, an adjunct professor at Karolinska Institutet and a joint last author of the study, highlighted the prospect of examining immunity in different parts of the respiratory system. According to News55, the method could reveal how that immunity shifts after an infection or a vaccination, and could assist in assessing new vaccines and antibody treatments aimed at the mucous membranes.
Limits and next steps
The technique is not yet part of clinical care. It is a first study involving a small number of people, and the researchers want to test it in larger groups before drawing firmer conclusions.
Until then, the public health advice for the season stands. Sweden's Public Health Agency recommends that people aged 65 and older get vaccinated against influenza, and that those aged 75 and older also receive a covid-19 vaccination, News55 reports.
The immediate question is whether the PExA readings can be reproduced at scale and shown to reflect what bronchoscopy finds. Watch for follow-up studies with larger cohorts.
