Cross‐reactive carbohydrate determinants in atopic and healthy dogs and their influence on allergy test specificity

Abstract

BackgroundThe selection of allergens for immunotherapy in atopic dogs is often based on serum allergy testing. Cross‐reactive carbohydrate determinants (CCDs) are common structures in plant and insect allergens that reportedly induce polysensitisation, reduce agreement between intradermal and serum tests and complicate allergen selection.MethodsThirty‐four dogs with diagnosed atopic dermatitis and 10 healthy dogs were included in the study. An intradermal test was conducted in atopic dogs, and serum samples from allergic and healthy dogs were analysed for allergen‐specific immunoglobulin E (IgE) before and after inhibition of detectable anti‐CCD‐IgE antibodies.ResultsAnti‐CCD‐IgE antibodies were not found in any of the healthy dogs and no polysensitisation to plant and insect allergens was detected. The agreement between intradermal and serum allergy test results in the atopic dogs with anti‐CCD‐IgE antibodies improved from slight to fair after blocking the anti‐CCD‐IgE antibodies. In addition, blocking clearly reduced polysensitisation to plant allergens but not to acarid allergens.LimitationsOnly a limited number of healthy dogs were tested in this study. A gold standard for determining the clinical relevance of IgE sensitisation does not exist.ConclusionInhibition of anti‐CCD‐IgE antibodies seems to be of importance to improve serum test specificity for allergen‐specific IgE in atopic dogs in relation to intradermal allergy testing.

Blocking cross‐reactive carbohydrate determinant‐specific IgE improves serum allergy testing reliability in atopic dogs

“…However, interestingly, non-atopic dogs did not present with anti-CCD IgE. 5 This contrasts with work by Piccione and colleagues, which reported that 13 per cent of non-atopic dogs had such antibodies, although titres were much lower than observed in atopic dogs. 9 Given the findings of this and previous studies, it is clear that we must now apply a new lens when looking back over the literature examining the prevalence of allergen-specific IgE in atopic and non-atopic animals -that of whether testing was performed before or after anti-CCD IgE antibody blocking.…”

“…However, despite the possible methodological explanations for the discrepancies between serum and intradermal test results, the view that CCD-specific IgE causes false positive reactions in ELISA-based serum allergy testing has prevailed, and diagnostic laboratories are increasingly using anti-CCD IgE blockers before processing ELISA samples. 4 In a study summarised on p 410 of this issue of Vet Record, 5 Kasper and colleagues explored the concept further by comparing the results of intradermal and serum testing in a group of 34 dogs with atopic dermatitis. As reported in previous studies, [6][7][8] the correlation between the intradermal and serum test results was relatively poor.…”

“…However, a significant improvement in correlation was observed when anti-CCD IgE blockers were used. 5…”

“…Usefully for clinicians, Kasper and colleagues' study 5 used widely available laboratory tests and skin test reagents, so the findings can be directly applied to clinical practice. However, although the skin test reagents and the commercial allergen-specific ELISA used in the study were produced by the same company, this does not mean that the same antigens were used in each test.…”

“…However, the presence of anti-CCD IgE unfortunately does not explain all of the differences between intradermal and serum test results, as Kasper and colleagues report that anti-CCD IgE blocking did not reduce polysensitisation to acarid allergens. 5 In non-allergic people, nematode infection has been found to induce sensitisation to house dust mites. In this situation, different house dust mite allergens are bound by IgE, and this 'non-functional IgE' specific to house dust mites is unable to cause mast cell degranulation.…”