Researchers have linked the presence of antibodies against the Aspergillus fumigatus (A fum) fungus with the development of bronchiectasis in people with COPD.

The study, “Sensitization to Aspergillus fumigatus as a risk factor for bronchiectasis in COPD,” was published in the International Journal of Chronic Obstructive Pulmonary Disease. 

Chronic obstructive pulmonary disease, or COPD, is a term that refers to a group of lung conditions whose hallmarks include respiratory symptoms and airflow limitations.

Some COPD patients also have bronchiectasis, a condition stemming from thickened airway walls. Scientists called the presence of both diseases COPD-bronchiectasis overlap syndrome.

Bronchiectasis increases the risk of death among COPD patients. Despite this, scientists don’t know what triggers their bronchiectasis.

The team hypothesized that there is link between the presence of A fum in COPD patients and the development of bronchiectasis. They also theorized that it might be connected with a deficiency of vitamin D. The study involved 350 people — 300 with COPD and 50 controls who were former smokers.

Significantly more COPD patients had bronchiectasis — 33 percent — than the controls — 10 percent.

Researchers measured the levels of all participants’ seven antibodies against A fum. They found significantly higher levels in 18 percent of COPD patients, versus in 4 percent of controls.

Levels of two antibodies in particular — anti-A fum IgG and anti-rAsp f1 IgE — were considerably higher in COPD patients than in controls.

Scientists refer to people with A fum antibodies as A fum-sensitized.

Additional analysis showed that significantly more A fum-sensitized COPD patients had bronchiectasis — 46 percent — than non-sensitized patients — 30 percent. COPD patients with ani-rAsp f1 and anti-rAsp f3 were even more likely to have bronchiectasis, the team said.

Although the proportion of men in the sensitized group was higher than in the non-sensitized group, there were no differences in the groups’ age, body mass index, smoking history, or use of corticosteroid inhalers.

Sputum culture analysis also showed that more A fum-sensitized patients had Pseudomonas aeruginosa and Serratia marcescens bacteria than non-sensitized patients, but not other bacteria commonly associated with COPD.

Researchers found no association between A fum sensitization and vitamin D deficiency.

The team said “the results show a high prevalence of A fum sensitization in COPD patients, and highlight a potential role of rAsp f1 and rAsp f3 in COPD-related bronchiectasis.”

They also underscored the importance of follow-up studies. “The search for underlying mechanisms in the development of bronchiectasis in COPD is relevant, since the presence of bronchiectasis in COPD influences management and prognosis of the disease,” they wrote.