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.