Patients allergic to fish tolerate ray based on the low allergenicity of Its parvalbumin.

BACKGROUND: Clinical reactions to bony fish species are common in patients with allergy to fish and are caused by parvalbumins of the beta-lineage. Cartilaginous fish such as rays and sharks contain mainly alpha-parvalbumins and their allergenicity is not well understood. OBJECTIVE: To investigate the allergenicity of cartilaginous fish and their alpha-parvalbumins in individuals allergic to bony fish. METHODS: Sensitization to cod, salmon, and ray among patients allergic to cod, salmon, or both (n = 18) was explored by prick-to-prick testing. Clinical reactivity to ray was assessed in 11 patients by food challenges or clinical workup. IgE-binding to beta-parvalbumins (cod, carp, salmon, barramundi, tilapia) and alpha-parvalbumins (ray, shark) was determined by IgE-ELISA. Basophil activation tests and skin prick tests were performed with beta-parvalbumins from cod, carp, and salmon and alpha-parvalbumins from ray and shark. RESULTS: Tolerance of ray was observed in 10 of 11 patients. Prick-to-prick test reactions to ray were markedly lower than to bony fish (median wheal diameter 2 mm with ray vs 11 mm with cod and salmon). IgE to alpha-parvalbumins was lower (median, 0.1 kU/L for ray and shark) than to beta-parvalbumins (median, >/=1.65 kU/L). Furthermore, alpha-parvalbumins demonstrated a significantly reduced basophil activation capacity compared with beta-parvalbumins (eg, ray vs cod, P < .001; n = 18). Skin prick test further demonstrated lower reactivity to alpha-parvalbumins compared with beta-parvalbumins. CONCLUSIONS: Most patients allergic to bony fish tolerated ray, a cartilaginous fish, because of low allergenicity of its alpha-parvalbumin. A careful clinical workup and in vitro IgE-testing for cartilaginous fish will improve patient management and may introduce an alternative to bony fish into patients' diet.