Polysensitization to allergens, lipocalins linked to asthma in dog-sensitized children

Researchers have found an association between polysensitization to furry animal allergens and lipocalins among children with asthma sensitized to dogs, according to a study published in Clinical and Translational Allergy.

Also, children with troublesome asthma have higher IgE levels in response to dog lipocalins compared with other children sensitized to dogs, Ulrika Käck, MD, researcher in the department of clinical science and education at Karolinska Institutet in Stockholm, and colleagues wrote in the study.

The study involved 59 patients aged 10 to 18 years with confirmed sensitization to dog dander recruited from pediatric outpatient clinics in the Stockholm area. Patients and their parents were interviewed. Also, the Pediatric Asthma Control Test (ACT) was administered to patients aged 10 to 11 years, and those aged 12 years and older completed the ACT.

Further, doctors measured each patient’s fractional exhaled nitric oxide level, performed nasal provocation testing (NPT) and analyzed blood samples.

The study population included nine patients without asthma (mean age, 13.2 years; 78% male) and 50 patients with asthma (mean age, 13.1 years; 62% male). Thirty of the patients with asthma reported being triggered by dog exposure. This included six with troublesome asthma, defined as a FeNO score greater than 35 ppb, methacholine PD20 levels less than 2 mol and ACT scores less than 20.

Also, 48 of the 50 patients with asthma reported allergic rhinitis as well, with 35 of these rhinitis cases triggered by dog exposure. The nine children who did not have asthma did have allergic rhinitis, including five whose rhinitis was triggered by dog.

Upon NPT, 46% of the children with asthma and 11% of the children without asthma reacted to dog dander extract. The researchers additionally found an association between asthma diagnosis, reduced scores on the ACT and pronounced bronchial hyperreactivity.

The children with allergy experienced more polysensitization to furry animal allergen molecules and lipocalins compared with the children who only had rhinitis. Children who did not have asthma had a median number of positive IgE results to furry animal allergen molecules of 3. The children with asthma had a median of 5.5, and those with troublesome asthma had a median of 9.

Similarly, the children who did not have asthma had a median number of positive IgE results to lipocalin of 2, while those with asthma had a median of 4 and those with troublesome asthma had a median of 6. The researchers reported an odds ratio for asthma with sensitization to any lipocalin of 7.2 (95% CI, 1.44-35.9).

The researchers also noted considerable overlap in sensitization to the cross-reacting lipocalins Can f 6 from dogs, Fel d 4 from cats and Equ c 1 from horses, with 54% of those with asthma and 11% of those without sensitized to Can f 6 (P = .03).

Compared with the rest of the population, the six children with troublesome asthma had higher IgE levels to dog dander (57 kU_A/L vs. 11 kU_A/L; P = .017) and dog lipocalins Can f 2 (44 kU_A/L vs. 4.1 kU_A/L; P = .015), Can f 4 (5.8 kU_A/L vs. 0.9 kU_A/L; P = .018) and Can f 6 (1.3 kU_A/L vs. 0.7 kU_A/L; P = .03).

Additionally, 83% of the children with troublesome asthma had a positive NPT with dog dander extract compared with 36% of the rest of the population (P = .036).

Among the 50 children with asthma, 17 had an ACT score less than 20. These children also had higher IgE levels to Can f 2 and Can f 4 compared with those who scored 20 or higher on their ACT.

With a median FeNO level of 33.5 ppb (interquartile range, 20-70) for the study population, 28 patients had levels greater than 35 ppb. These children had higher IgE levels toward dog dander and toward Can f 1 and Can f 4 compared with those with FeNO levels less than 35 ppb.

There were positive bronchial methacholine challenges (PD < 8 µmol methacholine) among 37 of the 54 children whose dog dander sensitizations were investigated, with 25 showing pronounced bronchial hyperreactivity (PD20 < 2 µmol methacholine).

Noting these findings, the researchers recommended that the asthma management of children with multiple lipocalin sensitizations should involve thorough monitoring in addition to advice about avoiding dogs. Children with allergic rhinitis to dog should be treated and evaluated for asthma as well, the researchers continued.

Detailed assessments that include molecular allergy diagnostics could help doctors evaluate the impact that allergic sensitization could have on asthma morbidity and improve their advice about pet exposure and immunotherapy, the researchers further said, as these allergens could be considered markers for asthma among these children.