Molecular Allergy Diagnostics Refine Characterization of Children Sensitized to Dog Dander

Abstract

To analyze patterns of immunoglobulin E (IgE) reactivity to dog allergen components in sensitized children and investigate the association between those patterns and clinical symptoms by nasal provocation tests (NPT).Children 10 to 18 years (n = 60) with known sensitization to dog identified by a skin prick test wheal >3 mm or serum-specific IgE >10 kU/L were included.NPTs were performed with a commercial dog extract by using a standardized protocol. The extract was analyzed by radioallergosorbent test inhibition and contained all 6 dog allergens (Can f 1, 2, 3, 4, 5, and 6) used in subsequent analyses. The allergens were present in a wide range of concentrations. Serum-specific IgE levels to dog extract and each of the allergenic components were measured.All but 2 children had allergic rhinitis or conjunctivitis, and 41 out of 60 (68%) reported symptoms with dog exposure. The mean serum-specific IgE level was 11.5 kU/L (interquartile range: 3.15–43.0 kU/L). Sensitization to Can f 1 was most common, followed in frequency by Can f 5, 4, 6, 2, and 3. There was a wide range of IgE levels to the components, with the highest levels to Can f 1, 2, and 5. History of dog-related rhinitis was most common among those sensitized to Can f 3 (94% vs 59% of those not sensitized, P = .012) and Can f 6 (86% vs 63%, P = .007). Similar associations were found for histories of dog-induced asthma. Most patients were sensitized to several components, with great overlap in their sensitization to the proteins belonging to different groups (lipocalins: Can f 1, 2, 4, and 6; serum albumin: Can f 3; and prostatic kallikrein: Can f 5). No single protein group was associated with history of dog-induced airway symptoms, but sensitization to more proteins increased the odds ratio (OR) of dog-induced asthma or rhinitis. Those sensitized to all proteins from all 3 groups were at higher risk of dog-induced rhinitis (OR: 8.36; 95% confidence interval: 1.0–69.5). Forty-two percent (25 out of 60) of patients had positive NPT results, 14 out of 60 (23%) had inconclusive NPTs, and 21 out of 60 (35%) had negative challenges. Those with positive NPT results were significantly more likely to report dog-induced rhinitis and asthma as compared with those with negative NPT results. After adjusting for the effects of different protein groups, only sensitization to the lipocalins (Can f 1, 2, 4, and 6) was associated with positive NPT results. Those sensitized to all 3 groups had the highest OR for a positive NPT result, but as with reported symptoms above, sensitization to increasing numbers of proteins was associated with increasing risk for a positive NPT result.Sensitization to lipocalins and to an increasing number of allergenic dog proteins is associated with dog-induced airway symptoms (dog allergy).“I am not allergic to my dog, but other dogs bother me.” My dog is “hypoallergenic.” How many times have we heard comments like these from patients? Every study that has tried to identify allergenic differences between breeds of dogs has failed to find that elusive hypoallergenic dog. In fact, there is great homology of Can f 1 (the major dog allergen) among breeds. Furthermore, all breeds have comparable amounts of airborne Can f 1 in the homes of dog owners. So, what is going on here? The answer might lie in component-resolved diagnostics (CRD). Commercially available CRDs have already helped our understanding of some food allergies by enhancing our ability to make accurate diagnoses of allergy in sensitized patients. Options for follow-up studies to this one are obvious. Do different breeds of dog produce varying amounts of individual or total lipocalins? Are some patients more highly sensitized to particular proteins or more types of proteins, placing them at differential risk of allergy to certain breeds? Or, are some less highly sensitized, making them more tolerant of different breeds? When those questions are answered and when CRDs for dog allergens are commercially available, we still might not identify a consistently less-allergenic dog. But, we might be able to identify the breeds most likely to be tolerated by a child sensitized to dog.