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 β-lineage. Cartilaginous fish such as rays and sharks contain mainly α-parvalbumins and their allergenicity is not well understood.

OBJECTIVE

To investigate the allergenicity of cartilaginous fish and their α-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 β-parvalbumins (cod, carp, salmon, barramundi, tilapia) and α-parvalbumins (ray, shark) was determined by IgE-ELISA. Basophil activation tests and skin prick tests were performed with β-parvalbumins from cod, carp, and salmon and α-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 α-parvalbumins was lower (median, 0.1 kU/L for ray and shark) than to β-parvalbumins (median, ≥1.65 kU/L). Furthermore, α-parvalbumins demonstrated a significantly reduced basophil activation capacity compared with β-parvalbumins (eg, ray vs cod, P < .001; n = 18). Skin prick test further demonstrated lower reactivity to α-parvalbumins compared with β-parvalbumins.

CONCLUSIONS

Most patients allergic to bony fish tolerated ray, a cartilaginous fish, because of low allergenicity of its α-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.