Exhaled Breath Particles Reveal Virus-Specific Antibodies in the Lower Airways

Respiratory viruses such as influenza virus, SARS-CoV-2, and respiratory syncytial virus (RSV) require immune protection across the airway mucosa. Antibodies in the respiratory tract lining are important for that protection. However, lower airway immunity has been difficult to assess because sampling small airways has required invasive procedures such as bronchoscopy. New findings demonstrate that virus-specific antibodies can be measured in exhaled breath particles.

Karolinska Institutet (Stockholm, Sweden) researchers and collaborators used a non-invasive method called PExA, or Particles in Exhaled Air, to assess antibodies from the small airways. Participants breathed into a specially designed instrument that collected tiny exhaled particles originating from the respiratory tract lining fluid. The collected particles were then analyzed for antibodies directed against specific respiratory viruses.

The study included 28 participants from the COMMUNITY cohort at Danderyd Hospital. Of these participants, 18 had recently experienced a respiratory tract infection. Researchers analyzed paired samples from blood, nasal secretions, and exhaled breath to compare antibody patterns across compartments.

In exhaled breath samples, the team detected IgA and IgG antibodies against SARS-CoV-2, influenza virus, and RSV. Virus-specific IgG levels in lower airway samples largely mirrored levels observed in blood. IgA showed a different pattern, consistent with a greater contribution from local mucosal antibody responses.

The study, “Non-invasive quantification of lower airway antigen-specific antibodies using exhaled breath particles,” was published online in eBioMedicine on November 2, 2026. It was conducted in collaboration between Karolinska Institutet, Danderyd Hospital, Uppsala University, and SciLifeLab. The researchers stated that the method could help study lower airway immune responses after respiratory infections or vaccinations and support evaluation of preventive treatments, while emphasizing that larger validation studies are needed.

“Antibodies in the nasal mucosa are important for protection against respiratory infections, but immune responses further down the lungs are also crucial, particularly for preventing severe disease such as pneumonia. This method opens up new possibilities for understanding how immunity differs between the upper and lower airways,” said Charlotte Thålin, Adjunct Professor at the Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, and co-last author of the study.

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