Prevalence of serum immunoglobulin E against cross-reactive carbohydrate determinants in allergic and nonallergic horses, and its impact on polysensitisation in serum allergen tests.

Abstract

BACKGROUND: The existence of antibodies against cross-reactive carbohydrate determinants (CCDs) has been studied extensively in humans, and more recently, in dogs&#x2009;and cats. These antibodies can reduce the specificity of in vitro serum allergen tests. OBJECTIVES: To investigate&#xa0;the prevalence of anti-CCD&#xa0;immunoglobulin (Ig)E in both allergic and nonallergic horses as well as evaluate&#xa0;its&#xa0;potential impact on serum allergen testing. ANIMALS: Twenty-one allergic and 21 nonallergic horses. METHODS AND MATERIALS: Sera were analysed for anti-CCD IgE utilising a commercial&#x2009;CHO&#x2009;enzyme-linked immunosorbent assay (ELISA). An allergen specific&#x2009;Fc-&#x3b5;&#x2009;receptor ELISA&#x2009;then was performed to evaluate polysensitisation, both with and without the addition of a proprietary anti-CCD blocking solution. RESULTS: Antibodies against CCD were detected in 30 of 42 horses. There was no statistically significant difference (p&#xa0;=&#xa0;0.18) between the allergic and healthy groups in regard to anti-CCD prevalence. Horses with anti-CCD IgE exhibited more polysensitisation on serum allergen tests than horses without anti-CCD IgE in all allergen groups except mites. Polysensitisation was statistically significant at the 95% confidence interval for grasses (p&#x2009;<0.03), weeds (p&#xa0;=&#xa0;0.02) and stinging insects (p&#xa0;=&#xa0;0.0005). This was found to be true across both study groups. Inhibition with an anti-CCD blocking solution resulted in a 43% average reduction in polysensitisation. CONCLUSION AND CLINICAL IMPORTANCE: The prevalence of anti-CCD IgE of horses in this study coincides with the prevalence detected in pollen-sensitised people. Horses with anti-CCD IgE exhibited more positive reactions on serum allergen tests. By minimising potential artifactual polysensitisation, inclusion of an anti-CCD blocker may facilitate identification of allergen-specific IgE.