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

Abstract

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.

Keywords: Food allergy; allergens; arginine kinase; hemocyanin; sarcoplasmic calcium binding protein; shrimp allergy.