Shrimp allergy beyond Tropomyosin in Italy: clinical relevance of Arginine Kinase, Sarcoplasmic calcium binding protein and Hemocyanin.

BACKGROUND Little is known about the prevalence and clinical relevance of sensitization to shrimp allergens other than tropomyosin. OBJECTIVE We detected the prevalence of arginine kinase and sarcoplasmic calcium binding protein sensitization, and identified a high molecular weight allergen that is frequently recognized by Italian shrimp-allergic patients. METHODS Sera from 40 shrimp-allergic patients underwent the detection of IgE specific for arginine kinase (rPen m 2) and sarcoplasmic calcium-binding protein (rPen m 4) by ISAC 112 Microarray platform and immunoblot analysis. A high molecular weight shrimp allergen was identified by N-terminal amino acid sequencing. RESULTS IgE to rPen m 2 and rPen m 4 were found in 4/40 (10%) and 6/40 (15%) sera, respectively; two sera reacted to both allergens. Clinically, 6/8 Pen m 2 and/or Pen m 4 reactors experienced severe allergies to shrimp. On immunoblot, 4/6 rPen m 4-positive sera showed IgE reactivity at about 20 kDa, whereas no rPen m 2-positive serum reacted at about 40 kDa. Nineteen (47%) sera showed IgE reactivity at molecular weights > 60 kDa. Such profile was not associated with IgE reactivity to rPen m 2 or rPen m 4. N-terminal amino acid sequencing of the high molecular weight allergen led to the identification of hemocyanin. CONCLUSION Shrimp arginine kinase and sarcoplasmic calcium-binding protein are minor allergens sensitizing only 10%-15% of Italian shrimp-allergic patients, but are clinically relevant. Hemocyanin is a clinically relevant high molecular weight shrimp allergen possibly cross-reacting to house dust mite.