Identification and characterization of a cathepsin L-like cysteine protease from Taenia solium metacestode

Taenia solium metacestode, a larval pork tapeworm, is a causative agent of neurocysticercosis, one of the most common parasitic diseases in the human central nervous system. In this study, we identified a cDNA encoding for a cathepsin L-like cysteine protease from the T solium metacestode (TsCL-1) and characterized the biochemical properties of the recombinant enzyme. The cloned cDNA of 1216 bp encoded 339 amino acids with an approximate molecular weight of 37.6 kDa which containing a typical signal peptide sequence (17 amino acids), a pro-domain (106 amino acids), and a mature domain (216 amino acids). Sequence alignments of TsCL-1 showed low sequence similarity of 27.3-44.6 to cathepsin L-like cysteine proteases from other helminth parasites, but the similarity was increased to 35.9-55.0 when compared to mature domains. The bacterially expressed recombinant protein (rTsCL-1) did not show enzyme activity; however, the rTsCL-1 expressed in Pichia pastoris showed typical biochemical characteristics of cysteine proteases. It degraded human immunoglobulin G (IgG) and bovine serum albumin (BSA), but not collagen. Western blot analysis of the rTsCL-1 showed antigenicity against the sera from patients with cysticercosis, sparganosis or fascioliasis, but weak or no antigenicity against the sera from patients with paragonimiasis or clonorchiasis. (c) 2006 Published by Elsevier B.V.

Molecular variation of Bothriocephalus acheilognathi Yamaguti, 1934 (Cestoda : Pseudophyllidea) in different fish host species based on ITS rDNA sequences

The molecular variation in Bothriocephalus acheilognathi Yamaguti, 1934 from 11 species of freshwater fish collected in Australia, China, the Czech Republic, England and Hawaii was investigated by determining the nucleotide sequences of the internal transcribed spacer region. The length of the first and second internal transcribed spacer sequences of multiple individuals ranged from 553 to 571 bp and 553 to 615 bp, and the G + C content from 53.1 to 53.5%. The percentage sequence divergence varied between 0 and 0.9% in the ITS1 and 0 and 6.6% in the ITS2, respectively, indicating the occurrence of intraspecific variation. It is demonstrated that the fragment length variation resulted primarily from microsatellite polymorphisms present in the ITS region, especially in the ITS2 region. Phylogenetic analyses revealed that B. acheilognathi examined in this study consisted of three closely related genotypes with certain degrees of host-specificity, and the genotype representing isolates from Cyprinus carpio L. was the most common and diverse form within the species B. acheilognathi.