Patients whose allergies cause sniffling have different fungi living in their noses, scientists discover

Nearly a quarter of Portuguese adults suffer from allergies causing a runny nose. This respiratory disease, formerly called allergic rhinitis and frequently associated with asthma, is a common problem worldwide, and the upper respiratory tract is a key target for research into the underlying disease processes.

Now, a global team of researchers has discovered that patients with allergy-induced sniffles and asthma have different fungal colonies or mycobiomes in the nose, suggesting potential avenues for future treatments.

“We showed that allergic rhinitis samples had significantly higher fungal diversity and a different fungal community structure compared to those from healthy controls,” said Dr. Luís Delgado of the University of Porto, Portugal, l ‘one of the authors of the article in Frontiers of microbiology. “This may suggest that allergic rhinitis increases the diversity and changes the composition of the upper respiratory microbiome.”

A miniature mycological world

Allergic rhinitis causes sneezing, itching, inflammation of the nasal mucous membranes, and a stuffy, runny nose. It is often comorbid with asthma, which also involves inflammation and blocked airways. Allergic rhinitis and asthma may even be different aspects of the same inflammatory airway disease, making it essential to identify the links between them and the underlying causes.

To study the nasal mycobiome, researchers recruited 214 participants from children and young adults attending an immunology and asthma clinic in Porto. 155 patients had both allergic rhinitis and asthma, while 47 were only diagnosed with allergic rhinitis and 12 with asthma. 125 healthy controls were also enrolled.

The scientists took samples from the participants’ noses using nasal swabs and sequenced the fungal DNA found, focusing on two specific regions to identify different fungal species and develop insight into each participant’s mycobiome. After quality checks, they had 306 samples to work with.

They then used network analysis to understand the relationships between different genera of fungi and to characterize the different fungal communities present in healthy and diseased participants. They also studied the function of different fungi, looking at the metabolic pathways they affect, to try to understand the implications of any variation in the mycobiome between patient groups.

Coughing and sneezing

The most common fungal families in all samples were Ascomycota and Basidiomycota. In these two families, 14 genera dominated the mycobiomes.

“Among these dominant genera, we detected common fungi that have been recognized in humans as allergenic or opportunistic pathogenic fungi,” Delgado said. “This suggests that the nasal cavity is a major reservoir of fungi that may be involved in allergic rhinitis and asthma.”

There was a very clear and statistically significant difference between patients with respiratory diseases and healthy controls, but no significant difference between different groups of patients with respiratory diseases. Patients with respiratory diseases had more diverse and richer mycobiomes.

Mushrooms sampled from patients with both allergic rhinitis and asthma also showed more evidence of links to each other than fungi found in the noses of healthy participants and those who had only allergic rhinitis. This could indicate that fungi are affecting the immune environment of the nose.

The scientists also found that three metabolic pathways associated with the production of a building block of DNA and RNA – 5-aminoimidazole ribonucleotide or AIR – were overabundant in the mycobiome of patients with allergic rhinitis and asthma. AIR is linked to the production of purines, necessary for energy metabolism and DNA synthesis.

If further studies confirm this link and identify the exact problem, AIR could be a future therapeutic target for treatment or diagnosis.

“However, we were unable to control for all patient-specific variables, such as disease severity and associated treatment levels, and patients were sampled at one time,” Delgado cautioned, explaining that the The study’s cross-sectional design provides an overview, but does not. This does not show how the mycobiome changes over time. Longitudinal studies could provide greater insight into whether fungi cause disease processes and, if so, which fungi are responsible.

“Addressing some of these clinical variables would be an interesting follow-up to our study, if we could get the appropriate funding,” Delgado said. “If we can’t go any further at this point, key data and hypotheses are published here so others can replicate them and finally connect the lab to the clinic.”