Nasal fungi differ in people with allergies and asthma

By Dr. Chinta SidharthanReviewed by Danielle Ellis, B.Sc.Dec 19 2024

Research reveals distinct differences in nasal fungi composition, structure, and function in individuals with allergies and asthma

A recent study published in Frontiers in Microbiology investigated the fungal communities in the nasal cavities of individuals with allergic rhinitis, asthma, or both and compared them to those of healthy controls.

The research team used advanced sequencing techniques to explore how fungal diversity, metabolic pathways, and fungal interactions differ across groups. The findings aimed to shed light on the role of the nasal mycobiome in airway diseases.

Background

Allergic rhinitis and asthma are prevalent chronic airway diseases causing significant health burdens. Allergic rhinitis involves nasal inflammation marked by symptoms such as sneezing and congestion, while asthma leads to airway obstruction and inflammation. Furthermore, these conditions frequently co-occur, suggesting shared underlying mechanisms.

The nasal cavity is a major reservoir for microbes and is known to host bacterial communities that influence respiratory health and disease. Recent studies have highlighted the airway bacteriome’s role in allergic rhinitis and asthma, including its contribution to inflammation and pathogen spread. However, the role of fungi in these diseases remains underexplored.

Fungal communities, or microbiomes, are increasingly being recognized as contributors to human health, with links to asthma onset and severity. Yet, few studies have examined nasal fungal communities in individuals with allergic rhinitis or asthma, leaving gaps in understanding fungal composition, interactions, and functions in these diseases.

About the study

The present study recruited 339 participants, including individuals with allergic rhinitis, asthma, or both, and healthy controls from northern Portugal. The researchers confirmed the diagnoses of asthma and allergic rhinitis through clinical criteria, skin tests, or specific immunoglobulin E assays. Subsequently, nasal swabs were collected from all participants, and fungal deoxyribonucleic acid (DNA) was extracted for sequencing.

The study used internal transcriber spacers (ITS1–ITS2) and high-throughput sequencing on an Illumina platform to identify and analyze the fungal communities. Additional bioinformatics tools processed and filtered the sequencing data to identify amplicon sequence variants.

Taxonomic classification was conducted using the UNITE (Unified system for the DNA-based fungal species linked to the classification) database, and community diversity was assessed through indices such as Shannon and Chao1 richness. Beta diversity, which represents community differences, was examined through principal coordinates analysis.

Additionally, the software PICRUSt2 (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) was used to predict the functional potential, for which the researchers inferred metabolic pathways based on fungal gene profiles. Statistical analyses were also employed to identify pathways that differed significantly between groups.

The study assessed fungal interactions through network analyses and also explored co-occurrence patterns across disease groups and controls. To ensure robustness, the researchers included controls for contamination and employed rigorous statistical methods, such as linear models and permutation tests, to compare the groups.

Results

The researchers found that the nasal fungal communities of individuals with allergic rhinitis, asthma, or both differed significantly from those of healthy controls. Two dominant fungal phyla, Ascomycota and Basidiomycota, were identified, along with 14 abundant genera.

Seven to 10 genera, including Alternaria, Cladosporium, and Wallemia, varied significantly between respiratory disease groups and controls. Notably, Malassezia was more abundant in healthy individuals, while genera such as Rhodotorula and Penicillium were enriched in the nasal mycobiome of the diseased groups.

Furthermore, the alpha-diversity analyses showed higher fungal richness and evenness in allergic rhinitis and asthma groups compared to the healthy controls. Beta diversity analyses also revealed significant structural differences in fungal communities between disease and control groups, although the differences between disease groups were minimal.

Additionally, the functional analyses identified 30 metabolic pathways that differed between the groups. Pathways related to 5-aminoimidazole ribonucleotide biosynthesis, a process linked to fungal growth and pathogenesis, were notably enriched in individuals with allergic rhinitis and asthma.

Fungal interaction networks also varied, with diseased groups showing more complex and interconnected networks compared to the sparse interactions in healthy individuals. These differences suggested that airway diseases disrupt fungal community dynamics, potentially exacerbating inflammation and disease severity.

Conclusions

Overall, the study highlighted significant differences in the nasal fungal communities of individuals with allergic rhinitis, asthma, or both compared to healthy controls. Diseased groups observed enhanced fungal diversity, altered metabolic pathways, and disrupted fungal interactions.

These findings highlighted the potential role of the nasal mycobiome in respiratory health and disease, providing a foundation for future research into its diagnostic and therapeutic implications in chronic airway conditions.