In Vivo Diagnosis with Purified Tropomyosin Comparison of Tropomyosin Sensitization in Shellfish and Mite Allergic Patients

Tropomyosin is the most studied shellfish allergen. This pan-allergen is involved in cross-reactivity between invertebrates, including mites. The objective was to determine the relevance of tropomyosin sensitization in shellfish and non-shellfish allergic individuals by in vivo diagnosis with purified tropomyosin. Patients residing in the Mediterranean Coast of Spain, were selected for the study according to two inclusion criteria: sensitization to house dust mites (Dermatophagoides pteronyssinus and/or Dermatophagoides farinae) and/or symptoms after shellfish consumption. Individuals that fulfilled the inclusion criteria were divided in two groups: Shellfish allergic patients (Group S) and Non-shellfish allergic patients (Group N). Tropomyosin from shrimp (Pen a 1), was purified under GMP conditions and used for SPT (50 μg/ml). Clinical information about patients was also collected. Tropomyosin showed purity higher than 95%. A total of 850 patients were enrolled, 790 in group N and 60 in group S. 65 % of patients from group S were also sensitized to mites. Forty-two individuals showed positive SPT to Tropomyosin. The prevalence of sensitization was 2.7% in group N and 35% in group S. Twenty-one of the patients positive to tropomyosin had clinical symptoms after shellfish consumption (50%), 3 (14.3%) of them suffered anaphylaxis. Shellfish allergic group reported more frequent presence of cockroaches at home. The prevalence of tropomyosin was lower in non-shellfish allergic patients (2.7%) respect to shellfish-allergic patients (35%). Tropomyosin is a clinically relevant sensitizer: half of the patients sensitized to tropomyosin reported clinical allergy to seafood. The tropomyosin SPT is a powerful tool for in vivo diagnosis.