Purification and preliminary characterization of a protease from the excretion-secretion products of Trichinella spiralis muscle-stage larvae

Functional genes and proteins of Trichinella spp

Research of Trichinella proteins has been conducted with emphasis on excretory-secretory (E-S) products of muscle larvae because of two reasons. The first is that it has prominent and narrow specific antigenicity, and the second is that it may play some role in nurse cell formation after being secreted into host muscle cells. Proteomic analysis of E-S proteins was further advanced by the aid of new analytical methods such as gene cloning, matrix-assisted laser desorption-ionization time-of-flight mass spectrometry, and expressed sequence tags database analysis. As the research progressed, the interest of researchers moved to identification of function of E-S products, which has shed further light on the intriguing relationships between parasites and hosts. Major constituents of the E-S products include 43-, 53-, and 45-kDa glycoprotein derived from the stichosome. Many proteins were discovered in E-S products after the 43-, 53-, and 45-kDa proteins although the relationships among them remain unclear. Some of the new proteins were partially defined in terms of their function including nuclear antigens, MyoD-like protein, TsJ5 protein, etc. There are better-characterized proteins based on the gene molecular method, which allow easier identification of the function of proteins of interest. Such examples were demonstrated by proteinases, proteinase inhibitors, heat shock proteins, glycosidases, etc.

Identification of stage-specifically expressed genes ofTrichinella spiralisby suppression subtractive hybridization

Newborn larvae (NBL) and adult (Ad) stage-specifically expressed genes or members of gene families ofTrichinella spiraliswere identified by suppression subtractive hybridization (SSH)†. Six cDNA clones were identified as NBL stage-specific, including 1 member of theT. spiralisgene family encoding glutamic acid-rich proteins, 2 clones encoding novel serine proteases, 2 closely related clones encoding proteins that are members of a deoxyribonuclease II (DNase II)-like family and 1 clone with no similarity to known genes. Four stage-specific clones encoding homologues of retinoid X receptor, caveolin, C2H2 type zinc finger protein and a putative protein with no homology to known sequences were obtained from 3-day-old adult worms. One gene specifically up-regulated in the 5-day-old adult worms encoding a putative cuticle collagen was also identified.

Localization of a 24-kDa collagenase in the Gymnorhynchus gigas plerocercoid

A 24-kDa collagenase was localized in the Gymnorhynchus gigas plerocercoid immunohistochemically by peroxidase complex staining using polyclonal antibodies from NMRI mouse sera immunized with purified enzyme. Immunoreactivity was determined at different parts of the body (scolex, vesicle and caudal region) and mainly localized in microtriches and parenchymal tissues of the scolex and vesicle. These results, along with the absence of the enzyme in the plerocercoid excretion–secretion products, suggest that the 24-kDa collagenase is produced by parenchymal cells in the anterior region and transported to the outer regions of the worm It is possible that the enzyme plays an important role in degrading parasite tissues during the moulting process.

Proteolytic activity in Caenorhabditis elegans : soluble and insoluble fractions

Proteolytic activities of soluble and insoluble fractions of the free-living soil nematode Caenorhabditis elegans were measured across a range of substrates, temperatures and pH conditions. Several protease inhibitors were also tested under these conditions. Results of these studies indicate that proteolytic activity is present in cytosolic (CF) and non-cytosolic (NCF) fractions of C. elegans extracts at every condition of pH, temperature and buffer assayed. On the other hand, the use of different protease inhibitors demonstrated the existence of exo and endoproteases types in CF as well as NCF. Moreover our results show that the use of two protease inhibitor mixed types proposed by several authors are not enough to avoid this lytic activity when homogenates of this nematode are employed in biochemical assays.

Critical roles for excretory-secretory cysteine proteases during tissue invasion of Paragonimus westermani newly excysted metacercariae

Paragonimus westermani is a trematode parasite, which causes pulmonary and/or extrapulmonary granulomatous disease in humans. Successful invasion of the host tissue is critical for the survival of this tissue-invasive parasite. The enzymatic hydrolysis of host proteins is clearly a prerequisite of this process. In this study, we have investigated the functional roles of the excretory-secretory cysteine proteases of P. westermani newly excysted metacercariae (PwNEM) in tissue invasion. The 27 and 28 kDa enzymes (PwMc27 and PwMc28) purified from PwNEM excretory-secretory products (ESP), preferentially degraded fibrillar proteins, but not globular proteins. PwMc28 significantly facilitated the invasion of PwNEM into mouse peritoneum, whereas a diffusible cysteine protease inhibitor, trans-epoxysuccinyl-L-leuciloamido-(4-guanidino) butane (E-64) inhibited this process dose-dependently. Two distinct isoforms of PwMc28 (PwMc28a and PwMc28b), which exhibited two amino acid differences in their mature domains, were identified by tandem mass spectrometry and sequence analysis. Both enzymes were localized at the tegument on the anterior border and on the oral sucker, which suggests excretion-secretion via exocytosis or via the excretory canal network. The mRNA transcripts of PwMc28a and b were expressed abundantly during the active invasion/migration through the host's tissues, suggesting their relevant function to tissue invasion/migration in the definitive host.

Cloning and analysis of a cDNA encoding a putative serine protease comprising two trypsin-like domains of Trichinella spiralis

The cDNA encoding a putative serine protease, TsSerP, was cloned by degenerative polymerase chain reaction and screening of the cDNA library from Trichinella spiralis adult-newborn larvae stage. Sequence analysis revealed the presence of two trypsin-like serine protease domains flanking a hydrophilic domain, with the catalytic triad residue histidine in the alpha domain substituted by an arginine residue. Southern blots indicated that this was a single copy gene in the parasite genome. Northern blots demonstrated a single 2.3-kb transcript during the muscle larvae and adult stages of T. spiralis. The recombinant protein from the TsSerP beta domain (betaSerP) was produced but not recognised by T. spiralis-infected swine serum. An anti-betaSerP polyclonal serum detected a 69-kDa polypeptide in the soluble antigens of T. spiralis muscle larvae. Immunolocalisation analysis located TsSerP on the inner layer of the cuticle and oesophagus of the parasite, suggesting a potential role in its moulting and/or digestive functions.

Characterization and cloning of metallo-proteinase in the excretory/secretory products of the infective-stage larva of Trichinella spiralis

Inhibitor sensitivity assays using azocaesin and FTC-caesin as substrates showed that the excretory/secretory (E/S) products of the infective-stage larvae of Trichinella spiralis contained serine, metallo-, cysteine and aspartic proteinases. The activity of the metallo-proteinase was zinc ion dependent (within a range of ZnSO(4) concentrations). Gelatin-substrate gel electrophoresis revealed two bands of molecular mass 48 and 58 kDa which were sensitive to the metallo-proteinase inhibitor EDTA. The former peptide was probably a cleavage product of the latter. The authenticity of the 58 kDa metallo-proteinase as an E/S product was confirmed by immunoprecipitation. Using PCR and RACE reactions, a complete nucleotide sequence of the metallo-proteinase gene was obtained. It comprised 2,223 bp with an open reading frame encoding 604 amino acid residues. The 3' untranslated region consisted of 352 bp, including a polyadenylation signal AATAA. A consensus catalytic zinc-binding motif was present. The conserved domains suggest that the cloned metallo-proteinase belongs to the astacin family and occurs as a single copy gene with 11 introns and 10 exons. Cluster analysis showed that the sequence of the metallo-proteinase gene of T. spiralis resembles those of Caenorhabdites elegans and Strongyloides stercoralis.

A putative serine protease among the excretory-secretory glycoproteins of L1 Trichinella spiralis

Trichinella spiralis first-stage larvae infect susceptible hosts by invading epithelial cells that line the small intestine. During this process the larva disgorges several glycoproteins that bear an unusual, highly antigenic sugar moiety, tyvelose (3,6-dideoxy arabinohexose). Monoclonal antibodies specific for tyvelose protect the intestine against infection, implicating tyvelose-bearing glycoproteins as mediators of invasion and niche establishment in the intestinal epithelium. In order to investigate these glycoproteins at the molecular level, we first prepared monoclonal anti-peptide antibodies. The antibodies bind a family of glycoproteins that are present in excretory-secretory products of first-stage larvae and are delivered to epithelial cells during invasion by T. spiralis. The major species present in an affinity purified fraction of crude T. spiralis antigens were subjected to tryptic peptide digestion. De novo amino acid sequencing of the peptides using Q-TOF tandem mass spectrometry, in combination with database searches and antibody screening of an L1 cDNA library, showed that the glycoproteins are variably glycosylated homologues of the serine protease family.

Characterization and purification of cytosolic and membrane-bound protease(s) in adults of Haemonchus contortus

The activity of protease(s) was observed separately in cytosolic and membrane-bound protease(s) from male and female Hae monchus contortus (Nematoda: Trichostrongylidae). Different fractions showed optimum protease activity at 37 degrees C, pH 8.5 and 8.0 mg casein concentration. The female fractions had a particularly high activity of protease(s) in comparison with the male fractions, especially of membrane-bound enzymes in the anterior half. Inhibition, activation studies revealed the presence of four kinds of protease(s) in cytosolic and membrane-bound fractions. Protease(s) in different fractions are purified to a greater extent by higher concentrations of saturated ammonium sulphate solution, i.e. ranging from 50 to 65%. The purification study revealed the presence of multiple forms of protease(s) in cytosolic and membrane-bound extracts of H. contortus.

Purification and partial characterization of proteinase activity in eggs of Dicrocoelium dendriticum

A preliminary purification has been carried out by continuous elution electrophoresis of a 49.5 kDa protease of crude extracts from Dicrocoelium dendriticum eggs. The enzyme showed a high capacity to degrade the collagen derivative azocoll at acidic pH. Although it is necessary to carry out further experiments to confirm any physiological role, this protease could be implicated in penetration mechanisms.

Proteolytic enzymes secreted by larval stage of the parasitic nematode Trichinella spiralis

Excretory/secretory products (ES), collected from in vitro cultures of muscle larvae (L1) of Trichinella spiralis (Owen, 1835) were examined for the presence of proteolytic enzymes. Several discrete proteinases in the size range of 25-55 kDa were identified by substrate gel electrophoresis and were characterised according to pH optima, substrate specificity and inhibitor sensitivity using azocasein assay. Serine, cysteine and metalloproteinases active at pH 5-7 were identified. The serine proteinases were found to predominate and some of them were found to be specific for the larval stage of the parasite. The results from the substrate analysis indicated the presence of collagenolytic and elastolytic activities. The proteinase activity was inhibited by IgG isolated from T. spiralis-infected mice, an observation of relevance to understanding host/parasite interactions and, ultimately, the development of anti-Trichinella vaccine.

A study of proteases throughout the life cycle of Trichinella spiralis

In the present report we study the proteolytic activity of the excretion-secretion and crude extracts of different stages of Trichinella spiralis (Owen, 1835) Railliet, 1895, (muscle-stage larvae, adult worms before and after mating, and newborn larvae) using natural substrates (structural and hematic mammalian proteins). The analysis of the results allow us to set up a certain stage-specificity, as well as an important relationship between the protease patterns throughout the parasite life cycle and how the parasite may overcome both mechanical and humoral barriers within the host. Muscle-stage larvae present a great activity against structural proteins (collagen), while newborn larvae and adult worms degrade principally hematic proteins (hemoglobin, fibrinogen and immunoglobulin G).

Haemonchus contortus: characterization and purification of excretory/secretory protease(s)

The activity of protease(s) has been examined separately in excretory/secretory (E/S) products from male and female Haemonchus contortus (Nematoda: Trichostrongylidae). The E/S proteolytic activity indicated the presence of preabsorptive digestion of host blood and/or tissues. Protease activity was optimum at 37 degrees C, pH 8.5 and 8.0 mg casein. These protease(s) were purified to 32.16- and 88.80-folds from male and female E/S products, respectively, by sequential purification with saturated ammonium sulphate followed by ion-exchange chromatography. The purification study revealed the presence of isomeric forms of protease(s) in the E/S products of H. contortus.

Purification of Trichinella spiralis tubulin: comparison of several analytic procedures

This study compares the purity indices found after purifying tubulin obtained from the nematode parasite Trichinella spiralis, using different chromatographic and electrophoretic methods. Affinity chromatography, using monoclonal antibodies anti-alpha and anti-beta-tubulin fixed to activated Sepharosa 4B-CNBr, yields a tubulin purity of 15%. In contrast, by means of interchange-anionic chromatography using a column of DEAE-Sephadex-A50, we obtained an increase in purity of up to 75%. Finally, with the combined application of preparative electrophoresis and electroelution of proteins in polyacrylamide gels with SDS, we obtained the best results with a purity reaching 90%.

Antibody response to a protease secreted by Trichinella spiralis muscle larvae

In the present study we analyzed the humoral response of Trichinella spiralis-infected mice to a 35-kDa protease (purified from the excretory-secretory products of T. spiralis muscle larvae) by a Western-blot procedure and an enzyme-linked immunosorbent assay (ELISA) technique using a panel of postinfection mouse anti-Trichinella sera. The results demonstrated that this response was time-dependent and that infected mice could be distinguished from controls. In addition, inhibition assays demonstrated that these antisera were capable of abolishing the proteinase activity of the 35-kDa protease in vitro. The occurrence of proteases seems to be a very common feature in parasite crude extracts and excretory-secretory products (McKerrow 1989). It is also known that these enzymes are implicated in important host-parasite interactions, and for this reason, recent reports have proposed the use of parasite proteases both as alternative targets for an induced immune response and as a rich source of antigenic material for diagnostic testing (Hotez et al. 1985; Yamasaki et al. 1989; Song et al. 1990; Frank and Grieve 1991; Britton et al. 1992; Song and Chappell 1993). We have recently purified a protease (mol. wt., 35 kDa) from the excretory-secretory (ES) products of Trichinella spiralis (GM-1 strain) muscle larvae and established some of the biochemical properties of this protease (Armas-Serra et al. 1994).(ABSTRACT TRUNCATED AT 250 WORDS)