Molecular cloning and characterization of a serine proteinase inhibitor from Trichinella spiralis

We produced a recombinant protein from a cDNA library from muscle larvae of Trichinella spiralis which had proteinase inhibitory activity. The predict ed amino acid sequence of the clone had an identity of only 30% to the seri ne proteinase inhibitors (serpins) from Caenorhabditis elegans or Brugia ma layi. At the putative reactive region, however, the identity was about 50%. The recombinant protein expressed in Escherichia coli inhibited 82% of the activity of the serine proteinase (trypsin). Stage-specific expression of this protein was suggested from the following experiments. Antibody against the recombinant protein could stain proteins migrating at about 42 kDa (wh ich is the expected size from the sequence) in crude extracts from newborn larvae and 18-day post-infection (p.i.) muscle larvae, but it failed to sta in any proteins in crude extracts from 30-day p.i. muscle larvae. Productio n of mRNA transcript for the serpin gene was restricted largely to the newb orn larvae and to 18-day p.i. muscle larvae. The antibody reacted with the stichocytes of the larvae at 18 days p.i., but did not react with the muscl e larvae at 24 days and 30 days p.i.