Development of a pathogenesis-based therapy for peeling skin syndrome type 1.

BACKGROUND: Peeling skin syndrome type 1 (PSS1) is a rare and severe autosomal recessive form of congenital ichthyosis. Patients are affected by pronounced erythroderma accompanied by pruritus and superficial generalized peeling of the skin. The disease is caused by nonsense mutations or complete deletion of the CDSN gene encoding for corneodesmosin (CDSN). PSS1 severely impairs quality of life and therapeutic approaches are totally unsatisfactory. OBJECTIVES: The objective of this study was to develop the first steps towards a specific protein replacement therapy for CDSN deficiency. Using this approach, we aimed to restore the lack of CDSN and improve cell-cell cohesion in the transition area of the stratum granulosum (SG) to the stratum corneum. METHODS: Human CDSN was recombinantly expressed in Escherichia coli. A liposome-based carrier system, prepared with a cationic lipopeptide to mediate the transport to the outer membrane of keratinocytes, was developed. This formulation was chosen for CDSN delivery into the skin. The liposomal carrier system was characterized with respect to size, stability and toxicity. Furthermore, the interaction with primary keratinocytes and human epidermal equivalents was investigated. RESULTS: The liposomes showed an accumulation at the membranes of keratinocytes. CDSN-deficient epidermal equivalents that were treated with liposomal encapsulated CDSN demonstrated presence of CDSN in the SG. Finally, the penetration assay and histological examinations revealed an improved epidermal integrity for CDSN-deficient epidermal equivalents, if they were treated with liposomal encapsulated CDSN. CONCLUSIONS: This study presents the first preclinical in vitro experiments for a future specific protein replacement therapy for patients affected by PSS1.

LEKTI domains D6, D7 and D8+9 serve as substrates for transglutaminase 1: implications for targeted therapy of Netherton syndrome.

BACKGROUND: Transglutaminase (TG)1 plays a key role in the formation of the cornified envelope and thus in the maintenance of the epidermal barrier. Patients with Netherton syndrome (LEKTI deficiency) have increased activity of both TG1 and serin proteases. OBJECTIVES: To determine whether there is a functional biochemical link between TG1 and LEKTI and whether LEKTI domains could possibly serve as substrates for TG1. METHODS: We analysed the protein sequence of LEKTI for possible TG1 recognition sites using bioinformatics. Synthetic peptides and recombinant LEKTI domains D6, D7 and D8+9 were examined in vitro and in situ for possible substrate specificity. The recombinant LEKTI domains were studied for inhibitory activity in a kallikrein (KLK)5 activity test. RESULTS: We identified possible TG1 consensus sequences in LEKTI domains D6, D7 and D8+9, pointing to a novel biological link between these two proteins. Indeed, synthesized short peptides from these consensus sequences were incorporated into the TG1 activity zone of the epidermis. In vitro the entire recombinant domains of LEKTI showed substrate specificity for TG1, which was again confirmed in situ. The inhibitory activity of the recombinant LEKTI domains was confirmed by a KLK5 inhibition test. The strongest inhibition was observed for domains D8+9. CONCLUSIONS: There are specific domains of LEKTI that are recognized and processed by TG1. LEKTI domains D6, D7 and D8+9 contribute to the formation and protection of the cornified envelope. These results impact the development of protein replacement therapy approaches for Netherton syndrome. What's already known about this topic? LEKTI and transglutaminase (TG)1 are key proteins involved in the terminal differentiation of the epidermis. Lack of LEKTI causes Netherton syndrome; TG1 deficiency causes lamellar ichthyosis. The serine protease inhibitor LEKTI is processed into different functional units. Among different target proteases, kallikrein (KLK)5 appears to be a key player in disease pathology. It has been demonstrated that LEKTI domain 6 inhibits KLK5 and KLK7; LEKTI domains 8-11 also inhibit KLK14. What does this study add? The single LEKTI domains 6, 7 and the functional unit of domains 8 and 9 contain recognition motifs for TG1. We show that these domains and unit are crosslinked into the epidermis by TG1. Functional analyses of the recombinant LEKTI domains revealed that LEKTI D8+9 has the strongest inhibitory effect on KLK5. What is the translational message? The novel functional link between LEKTI and TG1 should be taken into account when considering the development of a targeted topical protein therapy for Netherton syndrome. The unit of domains D8+9 may be sufficient for this purpose.

Medicinal plant extracts and plant-derived polyphenols with anthelmintic activity against intestinal nematodes.

Covering: 2001 up to the end of 2016Polyphenols comprise a structurally diverse class of natural products. As the development of new anthelmintic drugs against soil-transmitted helminthiases is an urgent need and polyphenols are widely used in the treatment of nematode infections in traditional medicine and modern science, we summarize the state of knowledge in the period of mainly 2001 up to the end of 2016 on plant extracts with known polyphenolic composition and of defined polyphenols, mainly from the classes of condensed and hydrolysable tannins, flavonoids, and phenylpropanoids. The diverse biological activity against different helminths and the underlying mechanisms are reviewed.

Immune recognition of excretory and secretory products of the filarial nematode Onchocerca ochengi in cattle and human sera.

Excretory-secretory (ES) products of nematodes and other helminths are the first molecules to interact with cell surfaces and soluble proteins within the host. In the present study, ES products of the filarial nematode Onchocerca ochengi were investigated as a model for Onchocerca volvulus, the causative agent of river blindness. These products were collected from adult and larval stages in vitro over a period of 7 days, to compare their immunological recognition in cattle and human sera, infected with species of Onchocerca. From the 156 sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) ES products or extracts, protein bands showed different patterns between female and male products. A comparison of antibody recognition of the different ES products by sera from infected cattle and humans, when analysed by enzyme-linked immunosorbent assay (ELISA), revealed a relatively higher reactivity of the female somatic extract to human and cattle sera compared to ES products of both genders. Nevertheless, similar reactivity of the O. ochengi male and female ES products to human and cattle sera was noticed. As a result, the interaction of ES products with the surface of the host and immune system often led to host responses, including the generation of antibodies. The O. ochengi ES products are therefore good sources of potential immunogenic proteins. The identification of these ES products is in progress, with the aim of developing vaccine candidates against human onchocerciasis.

Immune recognition of Onchocerca volvulus proteins in the human host and animal models of onchocerciasis.

Onchocerca volvulus is a tissue-dwelling, vector-borne nematode parasite of humans and is the causative agent of onchocerciasis or river blindness. Natural infections of BALB/c mice with Litomosoides sigmodontis and of cattle with Onchocerca ochengi were used as models to study the immune responses to O. volvulus-derived recombinant proteins (OvALT-2, OvNLT-1, Ov103 and Ov7). The humoral immune response of O. volvulus-infected humans against OvALT-2, OvNLT-1 and Ov7 revealed pronounced immunoglobulin G (IgG) titres which were, however, significantly lower than against the lysate of O. volvulus adult female worms. Sera derived from patients displaying the hyperreactive form of onchocerciasis showed a uniform trend of higher IgG reactivity both to the single proteins and the O. volvulus lysate. Sera derived from L. sigmodontis-infected mice and from calves exposed to O. ochengi transmission in a hyperendemic area also contained IgM and IgG1 specific for O. volvulus-derived recombinant proteins. These results strongly suggest that L. sigmodontis-specific and O. ochengi-specific immunoglobulins elicited during natural infection of mice and cattle cross-reacted with O. volvulus-derived recombinant antigens. Monitoring O. ochengi-infected calves over a 26-month period, provided a comprehensive kinetic of the humoral response to infection that was strictly correlated with parasite load and occurrence of microfilariae.

Immunization with Brugia malayi Hsp70 protects mice against Litomosoides sigmodontis challenge infection.

More than 1·5 billion people are at risk of being infected with filarial nematodes worldwide. Therapy and control of transmission are mainly based on mass drug distribution. As these drugs have to be administered annually or biannually and might be loosing their efficacy, a vaccine against filariae is an alternative approach to chemotherapy. In the current study, we have analysed the potential of Brugia malayi heat shock protein 70 (BmHsp70) as a vaccine candidate in a murine helminth infection. Immunization of BALB/c mice with alum-precipitated recombinant BmHsp70 conferred partial protection against subsequent challenge infection with the rodent parasite Litomosoides sigmodontis. Immunization resulted in reduced numbers of larvae in the pleural cavity as well as reduced numbers of circulating microfilariae. Reduced parasite burden was associated with high titres of BmHsp70-specific antibodies and increased production of type I and II cytokines in response to L. sigmodontis antigen and BmHsp70. In summary, the immunization with BmHsp70 induced cellular and humoral immune responses and partially protected against L. sigmodontis in a challenge infection. Therefore, we hypothesize that BmHsp70 might be considered as a potential vaccine candidate for reduction in the incidence of B. malayi infections in future studies.

Anthelmintic activity of phenolic acids from the axlewood tree Anogeissus leiocarpus on the filarial nematode Onchocerca ochengi and drug-resistant strains of the free-living nematode Caenorhabditis elegans.

The effect of three phenols (ellagic, gentisic and gallic acids) from the axlewood tree Anogeissus leiocarpus on Onchocerca ochengi and drug-resistant strains of Caenorhabditis elegans, a model organism for research on nematode parasites, is investigated. Worms were incubated in different concentrations of phenols and their survival was monitored after 48 h. Among the three acids, ellagic acid strongly affected the survival of O. ochengi microfilariae, O. ochengi adults, a wild-type C. elegans and anthelmintic-resistant strains of C. elegans, namely albendazole (CB3474), levamisole (CB211, ZZ16) and ivermectin (VC722, DA1316), with LC50 values ranging from 0.03 mm to 0.96 mm. These results indicate that the binding of ellagic acid in the worm differs from that of resistant strains of C. elegans. The efficacy of both gallic and gentisic acids was not significantly changed in resistant strains of C. elegans treated with levamisole (ZZ16, LC50= 9.98 mm, with gallic acid), albendazole (CB3474, LC50= 7.81 mm, with gentisic acid) and ivermectin (DA1316, LC50= 10.62 mm, with gentisic acid). The efficacy of these three pure compounds is in accordance with the use of A. leiocarpus from its locality of origin. The in vivo toxicity data reveal that the thresholds are up to 200 times higher than the determined LC50 values. Thus, ellagic acid could be a potential option for the treatment of nematode infections, even in cases of drug resistance towards established anthelmintic drugs.

In vitro activity of Cameroonian and Ghanaian medicinal plants on parasitic (Onchocerca ochengi) and free-living (Caenorhabditis elegans) nematodes.

Ethanolic and aqueous extracts of selected medicinal plants from Cameroon and Ghana were assessed for their in vitro anthelmintic activity by using the bovine filarial parasite Onchocerca ochengi and the free living nematode Caenorhabditis elegans, a model organism for research on nematode parasites. Worms were incubated in the presence of different concentrations of extracts and inhibitory effects were monitored at different time points. Among the extracts used in this study, ethanolic extracts of Anogeissus leiocarpus, Khaya senegalensis, Euphorbia hirta and aqueous extracts from Annona senegalensis and Parquetina nigrescens affected the growth and survival of C. elegans and O. ochengi significantly. The mortality was concentration dependent with an LC50 ranging between 0.38 and 4.00 mg/ml for C. elegans (after 72 h) and between 0.08 and 0.55 mg/ml for O. ochengi after a 24 h incubation time. Preliminary phytochemical screenings on these extracts revealed the presence of flavonoids, alkaloids, saponins, carbohydrates and tannins in the extracts. Accordingly, application of A. leiocarpus, K. senegalensis, E. hirta and A. senegalensis extracts could provide alternatives in the control of helminthic infections.

Immunohistological studies on neoplasms of female and male Onchocerca volvulus: filarial origin and absence of Wolbachia from tumor cells.

Up to 5% of untreated female Onchocerca volvulus filariae develop potentially fatal pleomorphic neoplasms, whose incidence is increased following ivermectin treatment. We studied the occurrence of 8 filarial proteins and of Wolbachia endobacteria in the tumor cells. Onchocercomas from patients, untreated and treated with antibiotics and anthelminthics, were examined by immunohistology. Neoplasms were diagnosed in 112 of 3587 female and in 2 of 1570 male O. volvulus. The following proteins and other compounds of O. volvulus were expressed in the cells of the neoplasms: glutathione S-transferase 1, lysosomal aspartic protease, cAMP-dependent protein kinase, alpha-enolase, aspartate aminotransferase, ankyrin E1, tropomyosin, heat shock protein 60, transforming growth factor-beta, and prostaglandin E(2). These findings prove the filarial origin of the neoplasms and confirm the pleomorphism of the tumor cells. Signs indicating malignancy of the neoplasms are described. Wolbachia were observed in the hypodermis, oocytes, and embryos of tumor-harbouring filariae using antibodies against Wolbachia surface protein, Wolbachia HtrA-type serine protease, and Wolbachia aspartate aminotransferase. In contrast, Wolbachia were not found in the cells of the neoplasms. Further, neoplasm-containing worms were not observed after more than 10 months after the start of sufficient treatment with doxycycline or doxycycline plus ivermectin.

Extract and the quassinoid ailanthone from Ailanthus altissima inhibit nematode reproduction by damaging germ cells and rachis in the model organism Caenorhabditis elegans.

Bark and leaves of Ailanthus altissima (Mill.) Swingle are widely used in European folk medicine to treat intestinal worm infections. The study aimed to rationalize a potential anthelmintic effect of A. altissima extract against the model organism Caenorhabditis elegans. A methanol-water (7:3, v/v) extract of the primary stem bark was tested on L4 larvae of C. elegans for induction of mortality and influence on reproduction. Bioactivity-guided fractionation was performed by chromatography on MCI-gel, preparative HPLC on RP18 stationary phase and fast-centrifugal-partition-chromatography. Structural elucidation of isolated quassinoids was performed by NMR and HR-ESI-MS. The sterilizing effect on C. elegans was investigated by light microscopy and atomic force microscopy of ultra-sections. Different GFP-tagged reporter strains were used to identify involved signaling pathways. A. altissima extract (1 mg/mL) irreversibly inhibited the reproduction of C. elegans L4 larvae. This effect was dependent on the larval stage since L3 larvae and adults were less affected. Bioactivity-guided fractionation revealed the quassinoid ailanthone 1 as the major active compound (IC50 2.47 µM). The extract caused severe damages to germ cells and rachis, which led to none or only poorly developed oocytes. These damages led to activation of the transcription factor DAF-16, which plays a major role in the nematode's response to stress. A regulation via the respective DAF-2/insulin-like signaling pathway was not observed. The current findings support the traditional use of A. altissma in phytotherapy to treat helminth infections and provide a base for standardization of the herbal material.

Comparative characterization of two galectins excreted-secreted from intestine-dwelling parasitic versus free-living females of the soil-transmitted nematode Strongyloides.

Helminths are complex pathogens that ensure their long-term survival by influencing the immune responses of their host. Excretory/secretory products (ESP) can exert immunoregulatory effects which foster parasite survival. Galectins represent a widespread group of ß-galactoside-binding proteins which are involved in a multitude of biological processes operative in parasite-host interaction. We had earlier identified seven galectins in Strongyloides ratti, four of them detected in the ESP of distinct developmental stages of the parasite. In the present report, we focused on the characterization of two of them, Sr-galectin-1 (Sr-Gal-1) and Sr-galectin-3 (Sr-Gal-3). While Sr-Gal-3 expression was strongest in parasitic females, Sr-Gal-1 was predominantly expressed in free-living females. Both proteins were cloned and recombinantly expressed in an E. coli expression system. Their glycan-binding activity was verified by haemagglutination and glycan array analysis. Furthermore, primary immunological activities of the Sr-galectins were initially investigated by the application of an in vitro mucosal 3D-culture model, comprising of mucosa-associated epithelial and dendritic cells. The Sr-galectins stimulated preferentially the release of the type 2 cytokines thymic stromal lymphopoietin and IL-22, a first indication for immunoregulatory activity. In addition, the Sr-galectins dose-dependently fostered cell migration. Our results confirm the importance of these carbohydrate-binding proteins in host-parasite-interaction by indicating possible interaction with the host mucosa-associated cells.

The gamma-glutamylcysteine synthetase of Onchocerca volvulus.

The tripeptide glutathione (GSH) plays an important role in the maintenance of the intracellular thiol redox state and in detoxification processes. The intracellular GSH level depends on glutathione reductase as well as on GSH synthesis. The first and rate limiting step in the synthetic pathway is catalysed by gamma-glutamylcysteine synthetase (gamma-GCS). The gamma-GCS was partially purified from the filarial parasite Onchocerca volvoulus and preliminary steady state kinetics were performed. The Ki-value for L-buthionine-S,R-sulphoximine (BSO), a specific inhibitor of gamma-GCS, was determined to be 0.13 microM, which is 54-fold lower than the Ki-value for the mammalian enzyme. Filarial gamma-GCS was also inhibited by cystamine with a Ki-value of 3.9 microM compared with 22.2 microM determined for the rat enzyme. Further, the cDNA and the gene of the O. volvulus gamma-GCS were cloned and sequenced. The gene of 5762 bp is composed of 14 exons and 13 introns. Southern blot analysis indicates that the gamma-GCS gene is present as a single-copy gene. In accordance with Northern blot analysis, the entire cDNA sequence encompasses 2377 bp. At its 5' end a nematode-specific spliced leader 130 bp upstream of the first in frame methionine was identified. The cDNA encodes a polypeptide of 652 amino acids with 50 and 69% sequence identity to the human and the Caenorhabditis elegans counterparts, respectively. The filarial gamma-GCS is proposed as a potential drug target.

Primary sequence and activity analyses of a catalase from Ascaris suum.

A complete cDNA encoding the catalase (EC 1.11.1.6) has been isolated from the parasitic nematode Ascaris suum (AsCAT). The active-site residues, the residues involved in ligand interaction, and NADPH-binding residues of the bovine liver catalase-type enzyme are highly conserved in the AsCAT predicted amino acid sequence. To confirm that the AsCAT cDNA encodes a functional enzyme, active recombinant protein (rAsCAT) was produced in a procaryotic expression system. The subunit molecular mass of the purified recombinant protein (rAsCAT) was determined to be approximately 60 kDa. According to gel filtration, the molecular mass of the active enzyme is 240 kDa, indicating that the catalase subunits form a homotetramer in solution. The optical spectrum of rAsCAT shows a typical ferric haem spectrum with a Soret band at 407 nm. Fluorescence spectroscopy demonstrates that rAsCAT binds NADPH. rAsCAT has catalase activity with hydrogen peroxide over a broad pH range, with a specific activity of 37,800 U mg-1. In addition to its catalase activity, rAsCAT displays peroxidase activity using the substrates t-butyl hydroperoxide and o-dianisidine. The haem ligands NaN3 and KCN caused a 50% inhibition of catalase activity at 9 and 19 microM, respectively. In the presence of a H2O2-generating system, catalase activity of rAsCAT was inhibited by 3-aminotriazole, phenolic compounds, and drugs.

Gene structure of the extracellular glutathione S-transferase from Onchocerca volvulus and its overexpression and promoter analysis in transgenic Caenorhabditis elegans.

Two highly similar genes encoding unique extracellular, glycosylated glutathione S-transferases (GSTs) of the human-pathogenic nematode, Onchocerca volvulus (Ov-GST1a and Ov-GST1b), have been isolated and characterised. The genes are approximately 3 kb in length and consist of seven exons interrupted by introns of approximately 100 bp in length, with the exception of intron II, which is approximately 1.6 kb in length. Interestingly, exon I and II encode a signal peptide and an N-terminal extension before sequence homology to other GSTs begins. The 5' flanking region was sequenced and analysed for transcription factor binding sites. Consistent with the lack of a TATA box, analysis of the mRNAs by primer extension showed multiple transcription start sites spread over a 60 bp region. To examine the activity and specificity of the Ov-GST1a gene promoter, we have exploited Caenorhabditis elegans as a heterologous transformation system. To analyse whether transgenic C. elegans are able to carry out processing and post-transcriptional modifications of the Ov-GST1a correctly, the protein was ectopically overexpressed in C. elegans. The parasite-derived Ov-GST1a gene product was correctly processed in transgenic C. elegans and posttranslational modifications, such as signal peptide cleavage and N-glycosylation, were performed successfully. This further demonstrates the potential of C. elegans as a host for expression of candidate vaccine antigens from O. volvulus and affirms the role of C. elegans as a model for parasitic nematodes.

Characterization of enzymatically active Onchocerca volvulus Cu/Zn superoxide dismutase expressed in Escherichia coli.

The Onchocerca volvulus superoxide dismutase was expressed in Escherichia coli, using a protocol designed to produce the native enzyme rather than a fusion protein. The recombinant O. volvulus superoxide dismutase (rOVSOD) was found in the cytosol of the disrupted bacteria and represented > 10% of the total bacterial protein. The enzyme was purified to homogeneity using DEAE-Sepharose chromatography, followed by phenyl-Sepharose chromatography. The rOVSOD was enzymatically active which was demonstrated by its reactivity with O2.- produced either by the xanthine-xanthine oxidase system or by stimulated eosinophils. The specific activity was determined to be 4668 U mg-1. This activity could be blocked by rabbit antiserum raised against the rOVSOD. The maximal activity was obtained upon supplementation of the bacterial growth media and enzyme buffer with copper and zinc ions. Activity characteristics in the presence of inhibitors was also characteristic of a Cu/Zn superoxide dismutase. The rOVSOD has an apparent subunit molecular mass of 16,000 in SDS-PAGE. The active enzyme behaves as a dimer of 32 kDa as determined by gel filtration.

Biochemical analysis, gene structure and localization of the 24 kDa glutathione S-transferase from Onchocerca volvulus.

Survival of Onchocerca volvulus, a pathogenic human filarial parasite, is likely to depend upon the detoxification activities of the glutathione S-transferases (GSTs). The 24 kDa O. volvulus GST, OvGST2, was expressed in a bacterial system and the recombinant protein was purified to homogeneity by affinity chromatography. Specific activities of the recombinant OvGST2 (rOvGST2) with a variety of substrates, and in the presence of inhibitors, were determined. With the universal substrate 1-chloro-2,4-dinitrobenzene, the specific activity of rOvGST2 was 2130 nmol min-1 mg-1. The rOvGST2 showed relatively limited selenium-independent glutathione peroxidase activity, but secondary products of lipid peroxidation, namely members of the trans,trans-alka-2,4-dienal,trans-alk-2-enal and 4-hydroxyalk-2-enal series, were conjugated to glutathione via OvGST2 dependent activity. The gene encoding the OvGST2 was isolated and the nucleotide sequence determined. The ovgst2 gene was found to possess seven exons with six intervening sequences, with all except one having consensus splice-site junctions. This intron/exon organisation of the ovgst2 gene is almost identical with those described for the mammalian Pi class GST genes, consistent with the protein structural evidence that the OvGST2 is related to the Pi class GSTs. Southern blot analysis with total parasite genomic DNA indicated a single copy gene, with a restriction pattern consistent with that of the isolated gene. The tissue distribution of the OvGST2 was examined in O. volvulus by immunohistochemistry and was shown to be distinct from that of the OvGST1. The OvGST2 was located throughout the syncytial hypodermis of male and female adult worms, as well as in the uterine epithelium. Microfilariae, and infective third stage larvae of O. volvulus, isolated from Simulium neavei, were immunopositive for OvGST2.

Molecular cloning, expression and characterization of a recombinant glutathione S-transferase from Echinococcus multilocularis.

We report the identification and characterization of the first cestode glutathione S-transferase (GST) cDNA sequence. A fragment of an Echinococcus multilocularis glutathione S-transferase cDNA was isolated by the polymerase chain reaction. Subsequently, a Lambda zap cDNA library prepared from mRNA from protoscolices of E. multilocularis was screened with this PCR fragment. A complete cDNA clone was isolated and the nucleotide sequence determined. Analysis of the E. multilocularis GST-deduced amino acid sequence indicates that it is clearly related to the mammalian mu-class GSTs. The E. multilocularis GST cDNA was expressed in Escherichia coli, using a protocol designed to produce the native enzyme rather than a fusion protein. The 25.5-kDa enzyme subunit was purified to homogeneity using glutathione-sepharose chromatography. Gel filtration demonstrated that this GST is enzymatically active as a homodimer. The recombinant enzyme had conjugating activity with organic hydroperoxides and with members of the trans,trans-2,4 alkadienal and trans-2-alkenal series, which are secondary products of lipid peroxidation.

Identification of a stress-responsive Onchocerca volvulus glutathione S-transferase (Ov-GST-3) by RT-PCR differential display.

The effects of oxidative insult on gene transcript levels in the filarial nematode Onchocerca volvulus were investigated using differential display RT-PCR. Oxidative stress was applied with the reagents paraquat, plumbagin and xanthine-xanthine oxidase. In all three cases, a cDNA fragment encoding a novel glutathione S-transferase (GST) resembling members of the theta-class was identified as upregulated (PQ29, PG112, XOD26). The subsequently isolated full-length cDNA harbors a 753-bp open reading frame encoding a GST with 268 amino acid residues and a predicted molecular mass of 31 kDa. This stress-responsive GST (Ov-GST-3) possesses only 14 and 21% sequence identity with the other O. volvulus GSTs (Ov-GST-1 and Ov-GST-2, respectively). Interestingly, Ov-GST-3 shares higher sequence identity with GSTs that are upregulated due to environmental stress. In order to confirm the specific upregulation of the Ov-GST-3 transcripts identified by differential display and to analyze the mRNA levels of the other Ov-GSTs (Ov-GST-1 and Ov-GST-2) under elevated stress conditions, a semi-quantitative polymerase chain reaction-enzyme-linked immunosorbent assay was performed. The Ov-GST-3 gene transcript level increased dramatically in response to xanthine-xanthine oxidase and to a lesser extent with paraquat and plumbagin. In contrast, Ov-GST-1 and Ov-GST-2 did not show any significant alterations in their steady-state mRNA levels in response to oxidative stress when examining the same mRNA samples. The present study clearly demonstrates that Ov-GST-3 is a critical enzyme in the defense against oxidative stress.

A common class of nematode glutathione S-transferase (GST) revealed by the theoretical proteome of the model organism Caenorhabditis elegans.

The genome verified C. elegans free-living nematode model is a new tool for investigating gene expression in human and animal nematode parasites. There is limited information on designating glutathione S-transferase (GST) to specific classes in lower invertebrates such as nematodes. Following cloning, amino acid sequence alignment, recombinant expression and Western blotting we provide evidence of a new GST class in nematodes or lower invertebrates.