Patients with non-cystic fibrosis bronchiectasis across the world have high rates of sensitization to airborne allergens, namely house dust mite and the fungus Aspergillus fumigatus, a new study shows.
As allergens (compounds that can trigger allergic reactions) are linked to more severe disease and poorer lung function, the study’s findings support the need for diagnostic screening for common allergens and proper treatment to prevent bronchiectasis from worsening.
The study, “Distinct “Immunoallertypes” of Disease and High Frequencies of Sensitization in Non-Cystic Fibrosis Bronchiectasis,” was published in the American Journal of Respiratory and Critical Care Medicine.
Atopy, a genetic tendency to develop allergic reactions and sensitivity to airborne allergens, such as house dust mite and fungi, are known to increase the risk for chronic respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). However, whether this is also true for non-cystic fibrosis bronchiectasis remains unclear.
To better understand the correlation between a patient’s immune system reactivity against allergens and bronchiectasis’ clinical outcomes, researchers evaluated patients from geographically distinct locations.
The team recruited 238 bronchiectasis patients from the Cohort of Asian and Matched European Bronchiectasis (CAMEB) study, including patients from Singapore, Malaysia, and Scotland. Patients were matched for age, gender, and disease severity.
The study also included 149 patients from Singapore who had allergic rhinitis (hayfever) for comparison.
Results showed that patients with bronchiectasis had a high allergen rate against fungi and the common house dust mite when compared to patients with allergic rhinitis — 57.6% vs 26.9%.
Also, patients who were sensitive to three or more allergens were found to have more severe disease and poorer lung function. Still, no association between frequency of disease flares (exacerbations) and allergen sensitization was found.
“We have found that bronchiectasis is often associated with allergic reactions to fungi and to the house dust mite. There are already existing treatments for these allergies; for example, steroids are commonly used to treat fungal allergy,” Sanjay H. Chotirmall, MD, PhD, assistant professor at Nanyang Technological University in Singapore and the study’s senior author, said in a press release.
“Our finding is important for improving the quality of life of those with bronchiectasis, as currently there are no licensed treatments for it,” Chotirmall said.
Researchers then assessed whether geographical location influenced the findings. They compared patients from Singapore and Malaysia to age- and sex-matched patients from Scotland.
The analysis revealed that the sensitivity to house dust mite and to major allergens of the fungus Aspergillus fumigatus was higher among Asian patients compared to Scottish patients. In contrast, patients from Scotland showed greater sensitivity to minor allergens from the same fungus. Major and minor allergens refer to whether the allergy they cause is more or less common.
Overall, the findings suggest that according to the geographical region, patients may need tailored anti-allergy treatments.
“It is clear that we need to understand our local diseases better, as our research findings clearly illustrate that Asian patients with bronchiectasis are different to those seen in other countries. By understanding such differences, we can tailor our treatment appropriately,” Chotirmall said.
In general, patients who had sensitized bronchiectasis triggered by fungus allergens were found to have enhanced activation of pro-inflammatory molecules, such as IL-1alpha, IL-1beta, and TNF-alfa. Also, this pro-inflammatory profile was linked to more severe disease and poorer outcomes.
In contrast, house dust mite-induced airway sensitivity was found to be associated with higher levels of immune-related signaling molecules and activation of eosinophils (the type of immune cells commonly associated with allergic reactions).
“These findings may change the way we treat patients with bronchiectasis,” said John A. Abisheganaden, associate professor at the Tan Tock Seng Hospital in Singapore and an author of the study. “The high prevalence of allergen sensitization found will help us focus on environmental factors and therapeutic interventions in the appropriate patients.”
“Our work reveals, for the first time, high frequencies and distinct patterns of sensitization in bronchiectasis,” researchers stated.
Pamela McShane, MD, specialist in bronchiectasis at the University of Chicago, added: “The data adds additional dimensions to the traditionally accepted paradigm of acquisition of the disease by revealing allergic mechanisms as a pathway by which patients develop bronchiectasis.”
According to the team, patients allergic to house dust mite should, for example, use allergen-proof bed covers and vacuum regularly to decrease their exposure to the allergen.
“Although therapies employed in other allergic respiratory diseases may now be considered in patients with bronchiectasis complicated by allergic sensitization, we must address the significant and inherent heterogeneity in this disease,” the researchers concluded.