Measurement of β(1→3)-glucans in occupational and home environments with an inhibition enzyme immunoassay

Abstract

β(1→3)-Glucans are known for their potent ability to induce nonspecific inflammatory reactions and are believed to play a role in bioaerosol-induced respiratory symptoms. An inhibition enzyme immunoassay (EIA) was developed for the quantitation of β(1→3)-glucans in dust samples from occupational and residential environments. Immunospecific rabbit antibodies were produced by immunization with bovine serum albumin-conjugated laminarin [β(1→3)-glucan] and affinity chromatography on epoxy-Sepharose- coupled β(1→3)-glucans. The laminarin-based calibration curve in the inhibition EIA ranged from ≃40 to 3,000 ng/ml (15 to 85% inhibition). Another β(1→3)-glucan (curdlan) showed a similar inhibition curve but was three to five times less reactive on a weight basis. Pustulan, presumed to be a β(1→6)-glucan, showed a parallel dose-response curve at concentrations 10 times higher than that of laminarin. Control experiments with NaIO4 and β(1→3)-glucanase treatment to destroy β(1→6)- and β(1→3)-glucan structures, respectively, indicated that the immunoreactivity of pustulan in the assay was due to β(1→3)-glucan and not to β(1→6)-glucan structures. Other polysaccharides, such as mannan and α(1→6)-glucan, did not react in the inhibition EIA. β(1→3)-Glucan extraction of dust samples in water (with mild detergent) was performed by heat treatment (120°C) because aqueous extracts obtained at room temperature did not contain detectable β(1→3)- glucan levels. The assay was shown to detect heat-extractable b(1→3)-glucan in dust samples collected in a variety of occupational and environmental settings. On the basis of duplicate analyses of dust samples, a coefficient of variation of approximately 25% was calculated. It was concluded that the new inhibition EIA offers a useful method for indoor β(1→3)-glucan exposure assessment.