Characterizing the nasal microbiome using a nasal allergen challenge model.

BACKGROUND

The role of the nasal microbiome in allergic rhinitis (AR), particularly following direct allergen exposure using a controlled model, is incompletely understood. Understanding microbiome dynamics after allergen challenge could provide insights into AR pathophysiology.

OBJECTIVE

We sought to evaluate nasal microbiome changes following nasal allergen challenge (NAC) with ragweed pollen extract in participants with ragweed-induced AR compared with control participants without allergy.

METHODS

An out-of-season NAC was completed by 19 participants with ragweed allergy and 12 control participants without allergy. Middle meatus and adjacent nasal cavity secretions were collected at baseline and 6, 24, and 48 hours after challenge. Microbial composition was characterized using 16S ribosomal RNA sequencing. Alpha diversity was assessed using the Shannon and Chao1 indices, and beta diversity was assessed using Bray-Curtis dissimilarity with principal coordinate analysis. Ragweed pollen-specific IgE (sIgE), total IgE, and Staphylococcus aureus nasal carriage were also evaluated.

RESULTS

Nasal microbial community composition differed according to biological sex (beta diversity P = .001) and S aureus carriage (P = .015). However, allergic status and NAC exposure had no significant effect on alpha or beta diversity over time. Genus-level differences between participants with AR and control participants emerged at 24 and 48 hours after challenge (P = .028 and P = .0062), with greater relative abundance of Streptococcus and Veillonella observed in control participants. Stratification by sIgE demonstrated significant differences in microbial community structure (P = .001), with higher sIgE levels associated with increased relative abundance of Streptococcus, Rothia, Staphylococcus, Neisseria, and Delftia. Higher total IgE levels were also associated with distinct microbial community profiles.

CONCLUSIONS

The nasal microbiome remained stable following acute allergen exposure despite clinical responses, whereas host factors including IgE levels, sex, and S aureus carriage were associated with differences in microbial community composition.