Antigenic and allergenic cross-reactivity of Epicoccum nigrum with other fungi

Background: Previous studies have identified Epicoccum nigrum (EN) as an important aeroallergen. Shared allergenicity among some fungi responsible for type I allergic disorders has been reported. Objective: To study the cross-reactivity among different fungi and to identify immunoglobulin (Ig)G and IgE binding components shared between EN and 10 other fungi known to cause respiratory allergy. Methods: Cross-reactivity studies were carried out by enzyme-linked immunoadsorbent assay (ELISA) and immunoblot inhibition using both rabbit antiserum raised against EN and pooled sera from patients' EN-positive skin test. Results: A large number (82%) of EN-sensitive patients showed positive skin reactivity to other fungal extracts. ELISA inhibition revealed >50% inhibition in binding of EN-specific rabbit antibodies with Alternaria alternata, Curvularia lunata, Cladosporium herbarum, and Penicillium citrinum extract, whereas the other extracts showed only 20 to 40% inhibition. Rabbit antisera to A. alternata, C herbarum, and C. lunata reacted with five to seven bands in EN, demonstrating the presence of shared antigens among these fungi. EN requires an amount of 100 ng for 50% IgE ELISA inhibition, whereas 175 ng of A. alternata, 160 ng of C. lunata, and 268 ng of C herbarum and P. citrinum were required for the same. IgE immunoblot and immunoblot inhibition further revealed that 43-, 26-, and 17-kD allergenic bands were shared by EN and A. alternata, whereas the 80- and 37-kD bands were common to both EN and C lunata. EN and C. herbarum shared 63- and 36-kD allergenic bands, whereas EN and P. citrinum shared the 34-kD band. Conclusion: EN showed maximum cross-reactivity with A. alternata followed by C. lunata, C. herbarum, and P. citrinum. This information will be useful in treating EN-allergic patients.