Identification of a 24 kDa excretory secretory protein in Anisakis simplex.

A gene coding for a 24 kDa protein (22 U homologous; As22U) was isolated from the Anisakis simplex third-stage larvae cDNA library during expressed sequence tag analysis. As22U was 636 bp long, and was found to code for 212 amino acid residues with a calculated mass of 23.5 kDa and a PI of 9.06. The As22U deduced amino acid sequence harbored a signal peptide region and 16 highly conserved cysteine residues, and it was identified in both the total extracts and excretory secretory (ES) protein of A. simplex. Its molecular weight was measured at 24 kDa via western blot analysis. The expression levels of thymic stromal lymphopoietin, IL-25, and CXCL1 (Gro-α) genes were increased at 6h after recombinant As22U treatment in mouse intestinal epithelial cells. Additionally, thymus and activation-regulated chemokine gene levels were increased at 14 h after treatment. Although we do not currently have sufficient evidence to determine whether As22U plays a role as an allergen, this remains possible. Further in vivo studies may provide some insight as to the allergenic properties of As22U.