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

Background: The existence of antibodies against cross‐reactive carbohydrate determinants (CCDs) has been studied extensively in humans, and more recently, in dogs and cats. These antibodies can reduce the specificity of in vitro serum allergen tests. Objectives: To investigate the prevalence of anti‐CCD immunoglobulin (Ig)E in both allergic and nonallergic horses as well as evaluate its 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 CHO enzyme‐linked immunosorbent assay (ELISA). An allergen specific Fc‐ε receptor ELISA 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 = 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 <0.03), weeds (p = 0.02) and stinging insects (p = 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. [ABSTRACT FROM AUTHOR]