Characterization of allergens of Anisakis simplex

Background: Anisakis simplex is an intestinal parasite of sea mammals. The larvae infect crustaceans, cephalopods and fish. Humans may consume A. simplex third stage larvae (L3) when eating infected raw or under‐cooked fish. Consumed larvae cause an inflammatory reaction when they penetrate the digestive mucosa. The larvae or their secretory/excretory products can sensitize humans and induce an immunoglobulin E (IgE)‐mediated allergic reaction. This parasite is now being implicated in numerous cases of allergic reactions after eating fish. The purpose of this study was to evaluate the allergenicity of proteins present in an extract of the third stage larva. Methods: Rabbit antiserum raised to A. simplex somatic extract (L3) was reacted by crossed immunoelectrophoresis (CIE) with the same somatic extract. Crossed radioimmunoelectrophoresis (CRIE) was also performed by incubating CIE gels first in the sera of 13 individuals with positive immunoCAP to A. simplex and then in radiolabeled anti‐human IgE. Results: Twelve to 16 antigen–antibody precipitin peaks were visualized on Coomassie blue stained CIE gels in which somatic extract was reacted with somatic‐antiserum. Autoradiography of CRIE gels showed that 18 different proteins bound IgE in patient sera. Individual patients had serum IgE directed at two to 10 different allergens. Five of these allergens were recognized by ≥50% of the patients. No allergen was recognized by every patient and no patient had serum IgE directed at all 18 allergens. Conclusion: Somatic extracts of A. simplex L3 larva contain a large number of allergenic molecules and there is significant variability between patients in their sensitivity and reactivity to these allergens.