A reverse-sandwich ELISA for IgG antibody to a pollen allergen

We have developed a reverse-type sandwich ELISA for measurement of IgG (+IgA) antibody to a major allergen of Sugi (Japanese cedar) pollens. In this assay, microplate wells were coated with the allergen proteins that had been dispersed in the presence of 0.5 mol/L NaCl and 20 micrograms/ml of bovine serum albumin, followed by addition of test serum, and then the biotinylated allergen. Beta-galactosidase-conjugated streptavidin was used for detection of the captured allergen, 4-methylumbelliferyl-beta-D-galactoside was used as the enzyme substrate, and fluorescence intensity of the product, 4-methylumbelliferone, was measured by a fluorometric reader. This assay was found to detect a total activity of IgG, IgA, and IgE antibodies present in the serum of the patients with pollinosis. IgG (+IgA) antibody was determined after absorption of the serum with anti-IgE Sepharose gel. Sera from individuals who were unexposed to the pollens demonstrated no nonspecific reactions in this assay. This method may be useful as a simple technique for monitoring the efficacy of immunotherapy that is expected to elicit IgG blocking antibody and also for large-scale seroepidemiologic studies on the prevalence of non-IgE antibodies in a general population.