Pollen exposure weakens innate defense against respiratory viruses

Allergy. 2020 Mar;75(3):576-587. doi: 10.1111/all.14047. Epub 2019 Nov 7.


Background: Hundreds of plant species release their pollen into the air every year during early spring. During that period, pollen allergic as well as non-allergic patients frequently present to doctors with severe respiratory tract infections. Our objective was therefore to assess whether pollen may interfere with antiviral immunity.

Methods: We combined data from real-life human exposure cohorts, a mouse model and human cell culture to test our hypothesis.

Results: Pollen significantly diminished interferon-λ and pro-inflammatory chemokine responses of airway epithelia to rhinovirus and viral mimics and decreased nuclear translocation of interferon regulatory factors. In mice infected with respiratory syncytial virus, co-exposure to pollen caused attenuated antiviral gene expression and increased pulmonary viral titers. In non-allergic human volunteers, nasal symptoms were positively correlated with airborne birch pollen abundance, and nasal birch pollen challenge led to downregulation of type I and -III interferons in nasal mucosa. In a large patient cohort, numbers of rhinoviruspositive cases were correlated with airborne birch pollen concentrations.

Conclusion: The ability of pollen to suppress innate antiviral immunity, independent of allergy, suggests that high-risk population groups should avoid extensive outdoor activities when pollen and respiratory virus seasons coincide.

Keywords: antiviral response; lambda-interferones; nasal symptoms; nonallergenic pollen compounds; respiratory syncytial virus; rhinovirus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Humans
  • Immunity, Innate*
  • Interferons
  • Mice
  • Nasal Mucosa
  • Pollen / adverse effects*
  • Respiratory Syncytial Viruses*
  • Rhinovirus*


  • Interferons