Immunoglobulin G1 subclass responses can be used to detect specific allergy to the house dust mites Dermatophagoides farinae and Dermatophagoides pteronyssinus in atopic dogs

Abstract

Background: In dogs with atopic dermatitis, intradermal testing (IDT) or allergen specific IgE serological testing are routinely employed to identify causative allergens. These allergens can then be used for allergen-specific immunotherapy and allergy management. The clinical relevance of this testing is affected by the source of allergen, and other biomarkers that are more related to specific allergens still need to be identified. The aim of this study was to investigate levels of specific IgE, total IgG, and IgG1 and IgG2 subclasses against the local house dust mites (HDM) Dermatophagoides farinae (DF) and D. pteronyssinus (DP) as biomarkers by using in-house ELISAs in healthy (n = 33) and atopic dogs (AD) (n = 44) that were either positive or negative by IDT to HDM.

Results: Being over 3 years of age was a risk factor for AD (Odds Ratio (OD) = 4.10, 95% Confidence interval (CI) 1.57-10.75, p = 0.0049), but there was no relation to IDT outcomes (OR = 0.9091, 95% CI 0.22-3.74, p = 1.00). High levels of all antibody isotypes (IgE, IgG, IgG1 and IgG2) against HDM were found in aged healthy dogs (> 3 years old). In AD, HDM-IgE and IgG1 levels were higher in dogs that were IDT positive to HDM than in IDT negative animals. Levels of IgE and IgG1 could be used to distinguish the specific allergens, whereas total IgG and IgG2 levels were not different between IDT-positive and IDT-negative AD. By the receiver operating characteristic curve at a false-positive rate = 0.10, both IgE and IgG1 showed better sensitivity than IgG and IgG2. Similar to IgE, serum IgG1 concentration was also relevant to IDT outcomes.

Conclusions: Our in-house ELISAs coated with local HDM were useful for evaluating antibody levels, and we propose use of the HDM-specific IgG1 subclass as a biomarker to detect HDM specific allergens in AD, potentially together with an IgE based platform.

Keywords: Antibody; Biomarker; Canine atopic dermatitis; House dust mites; Immunoglobulin G1 subclass.

Fig. 1

Analysis of protein components in crude extracts of DP and DF (Cropped gel). Protein bands of Der f 15, Der f 18 and Der f/ Der p 1 are located at 97–109 (a), 60 (b) and 25 (c) kDa respectively

Fig. 2

Median and interquartile range of DF- and DP-specific IgE, IgG antibodies and IgG subclasses levels. Aged healthy dogs (> 3 years) had high levels of all antibody types to both species of HDM. In cases of CAD (+IDT or -IDT to DF/DP) high IgE and IgG1 levels were in accordance with IDT results. Dotted line; cut-off levels for each ELISA

Fig. 3

The pattern of specific IgG1 and IgG2 in total IgG against DF and DP in healthy and AD dogs. A low IgG1/total IgG ratio and high value for the IgG2/total IgG ratio were observed in the young healthy dogs (< 3 years) and in AD with negative IDT to DF/DP, whereas the patterns were switched in the aged healthy dogs (> 3 years). AD that were positive in IDT to DF/DP showed a high ratio of both IgG1/total IgG and IgG2/total IgG

Fig. 4

Receiver operating characteristic curve (ROC) for prediction of DF and DP allergy based on the antibody levels measured by enzyme-linked immunosorbent assay. By IgE and IgG1 subclass, the curve analysis shows prediction accuracy with an area under the curve (AUC) (P <  0.05)