METHODS: Purified recombinant beta-parvalbumin, beta-enolase and aldolase A allergens of grass carp produced by transformed E. coli cells were coated onto microtiter plates for detection of specific IgE against fish allergens present in sera of 14 subjects with a clinical history of IgE-mediated fish allergy. IgE reactivity to recombinant allergens from C. idella and to cod, tuna and salmon extracts was tested by IgE ELISA and ImmunoCAP respectively.
RESULTS: Parvalbumin from C. idella was recognized by all subjects while Gad m 1 was recognized by 10 (71.4%) subjects. There was significant correlation between IgE reactivity to C. idella parvalbumin and Gad m 1, and IgE reactivity to C. idella was higher than to Gad m 1. IgE reactivity was observed in one patient to aldolase and none to enolase. C. idella parvalbumin inhibited IgE binding to immobilized Gad m 1 for more than 80% even at the lowest concentration (1 mg/ml). Reciprocally, Gad m 1 only inhibited 40% of IgE binding to C. idella parvalbumin at 1 mg/ml.
CONCLUSIONS: Grass carp has a higher diagnostic value for fish allergy diagnosis in Hong Kong patients when compared to cod. This study also highlights the need to use the right fish species for allergy diagnosis. (funded by Hong Kong Institute of Allergy Research Grant)