Identification and characterization of a 30 kd major allergen from Parapenaeus fissurus.

The allergenic components of the shrimp (Parapenaeus fissurus) were identified by immunoblotting with sera from 10 allergic patients. Six components, ranging in molecular weight from about 86 to 39 kd, showed IgE-binding activity and were identified as allergens of the shrimp. The component with a molecular weight of about 39 kd showed the highest frequency of IgE binding (70%) and was considered to be one of its major allergens. Two monoclonal antibodies against this 39 kd component were generated, and their antigenic cross-reactivity with five different kinds of seafood, shrimp, crab, cuttlefish, oyster, and pomfret was analyzed. Monoclonal antibody 1-6-10B reacted with the 39 kd component from shrimp only, but monoclonal antibody 2-7-1E also reacted with the 39 kd component from crab. By extraction with 0.5% sodium dodecylsulfate and ethanol precipitation, a highly purified shrimp 39 kd component was obtained. In two-dimensional gel electrophoresis six isoforms of this purified 39 kd component, with isoelectric point values from 5.1 to 5.6, were identified. No marked difference was observed when the amino acid composition of this purified 39 kd allergen was compared with those of serum albumin from different animals. They all contain a high proportion of acidic amino acids. There was also a 62% to 83% sequence homology among three different pairs of peptide fragments of purified 39 kd components of shrimp and crab. In conclusion, a 39 kd major allergen from the shrimp has been identified and characterized in the present study. According to the suggestions of the International Union of Immunological Societies, this allergen is designated as Par f I.