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.