Biochemical characterization and gene structure analysis of the 24-kDa glutathione transferase sigma from Taenia solium.

Taenia solium can cause human taeniasis and/or cysticercosis. The latter can in some instances cause human neurocysticercosis which is considered a priority in disease-control strategies and the prevention of mental health problems. Glutathione transferases are crucial for the establishment and long-term survival of T. solium; therefore, we structurally analyzed the 24-kDa glutathione transferase gene (Ts24gst) of T. solium and biochemically characterized its product. The gene promoter showed potential binding sites for transcription factors and xenobiotic regulatory elements. The gene consists of a transcription start site, four exons split by three introns, and a polyadenylation site. The gene architecture is conserved in cestodes. Recombinant Ts24GST (rTs24GST) was active and dimeric. Anti-rTs24GST serum showed slight cross-reactivity with human sigma-class GST. A 3D model of Ts24GST enabled identification of putative residues involved in interactions of the G-site with GSH and of the H-site with CDNB and prostaglandin D2. Furthermore, rTs24GST showed optimal activity at 45 °C and pH 9, as well as high structural stability in a wide range of temperatures and pHs. These results contribute to the better understanding of this parasite and the efforts directed to fight taeniasis/cysticercosis.

Taenia larvae possess distinct acetylcholinesterase profiles with implications for host cholinergic signalling.

Larvae of the cestodes Taenia solium and Taenia crassiceps infect the central nervous system of humans. Taenia solium larvae in the brain cause neurocysticercosis, the leading cause of adult-acquired epilepsy worldwide. Relatively little is understood about how cestode-derived products modulate host neural and immune signalling. Acetylcholinesterases, a class of enzyme that breaks down acetylcholine, are produced by a host of parasitic worms to aid their survival in the host. Acetylcholine is an important signalling molecule in both the human nervous and immune systems, with powerful modulatory effects on the excitability of cortical networks. Therefore, it is important to establish whether cestode derived acetylcholinesterases may alter host neuronal cholinergic signalling. Here we make use of multiple techniques to profile acetylcholinesterase activity in different extracts of both Taenia crassiceps and Taenia solium larvae. We find that the larvae of both species contain substantial acetylcholinesterase activity. However, acetylcholinesterase activity is lower in Taenia solium as compared to Taenia crassiceps larvae. Further, whilst we observed acetylcholinesterase activity in all fractions of Taenia crassiceps larvae, including on the membrane surface and in the excreted/secreted extracts, we could not identify acetylcholinesterases on the membrane surface or in the excreted/secreted extracts of Taenia solium larvae. Bioinformatic analysis revealed conservation of the functional protein domains in the Taenia solium acetylcholinesterases, when compared to the homologous human sequence. Finally, using whole-cell patch clamp recordings in rat hippocampal brain slice cultures, we demonstrate that Taenia larval derived acetylcholinesterases can break down acetylcholine at a concentration which induces changes in neuronal signalling. Together, these findings highlight the possibility that Taenia larval acetylcholinesterases can interfere with cholinergic signalling in the host, potentially contributing to pathogenesis in neurocysticercosis.

Crystal structures of Triosephosphate Isomerases from Taenia solium and Schistosoma mansoni provide insights for vaccine rationale and drug design against helminth parasites.

Triosephosphate isomerases (TPIs) from Taenia solium (TsTPI) and Schistosoma mansoni (SmTPI) are potential vaccine and drug targets against cysticercosis and schistosomiasis, respectively. This is due to the dependence of parasitic helminths on glycolysis and because those proteins elicit an immune response, presumably due to their surface localization. Here we report the crystal structures of TsTPI and SmTPI in complex with 2-phosphoglyceric acid (2-PGA). Both TPIs fold into a dimeric (ß-α)8 barrel in which the dimer interface consists of α-helices 2, 3, and 4, and swapping of loop 3. TPIs from parasitic helminths harbor a region of three amino acids knows as the SXD/E insert (S155 to E157 and S157 to D159 in TsTPI and SmTPI, respectively). This insert is located between α5 and ß6 and is proposed to be the main TPI epitope. This region is part of a solvent-exposed 310-helix that folds into a hook-like structure. The crystal structures of TsTPI and SmTPI predicted conformational epitopes that could be used for vaccine design. Surprisingly, the epitopes corresponding to the SXD/E inserts are not the ones with the greatest immunological potential. SmTPI, but not TsTPI, habors a sole solvent exposed cysteine (SmTPI-S230) and alterations in this residue decrease catalysis. The latter suggests that thiol-conjugating agents could be used to target SmTPI. In sum, the crystal structures of SmTPI and TsTPI are a blueprint for targeted schistosomiasis and cysticercosis drug and vaccine development.

Characterization of a novel cathepsin L-like protease from Taenia solium metacestodes for the immunodiagnosis of porcine cysticercosis.

Porcine cysticercosis is an endemic parasitic disease caused by infection with Taenia solium that is found predominantly in developing countries. In order to aid in the development of simple diagnostic approaches, identification and characterization of potential new antigens for immunodiagnostic purposes is desired. The cysteine protease family has previously been found to have important immunodiagnostic properties. These proteases are expressed as zymogens which contain a signal peptide, pro-peptide, and an active domain. Subsequent catalytic cleavage of the pro-peptide converts these zymogens into enzymes. With the use of bioinformatic tools we identified an active domain of a novel cathepsin L-like cysteine protease (TsolCL) in the T. solium genome. The TsolCL gene includes 705 nucleotides (nt) within a single intron and a 633 nt exonic sequence encoding an active protein of 211 amino acids. Sequence alignment and phylogenetic analysis suggest that the TsolCL gene is closely related to genes found in Echinoccocus granulosus and E. multiloculars. In addition, TsolCL was found to have a 61.9%-99.0% similarity to other cathepsin L proteins found in other helminths and mammals. We cloned, expressed, purified, and characterized the recombinant active TsolCL (27 kDa) using the baculovirus-insect cell expression system. TsolCL showed cysteine protease enzymatic activity with the capacity to hydrolyze the Z-Phe-Arg-AMC substrate as well as bovine serum albumin. However, TsolCL was not able to hydrolyze human immunoglobulin. In addition, TsolCL has cathepsin L conserved amino acid residues in the catalytic site (Gln8, Cys14, His159, Asn179 and Trp181) and the motif GCNGG. Using ELISA, TsolCL was able to distinguish circulating IgG antibodies between healthy animals and naturally infected pigs with cysticercosis, showing a moderate sensitivity of 83.33% (40/48; 95% CI: [69.8%-92.5 %]), and a specificity of 83.78% (31/37; 95% CI: [67.9%-93.8%]). In conclusion, a novel cathepsin L-like cysteine protease from a T. solium metacestode was expressed successfully in Baculovirus system and was evaluated as a candidate antigen to diagnose porcine cysticercosis using the ELISA immunoassay.

Taenia solium glutathione transferase fraction activates macrophages and favors the development of Th1-type response.

Glutathione (GSH) transferase (GST) is an essential enzyme in cestodes for the detoxification of xenobiotics. In Taenia solium, two GSTs (Ts25GST and Ts26GST kDa) were isolated as a fraction (SGSTF) by GSH-Sepharose-4B. Both are located on the tegument. Immunization assays with SGSTF reduced up to 90% of the parasitic load in a murine model of cysticercosis. It prompted us to investigate how SGSTF induces this protective immune response. To test it, we exposed peritoneal macrophages to SGSTF for 24 h; such exposure favored the production of IL-12, TNF, and IL-10 as well as the expression of nitric oxide synthase 2 inducible (Nos2) and CD86, but did not induce the expression of chitinase-like 3 (Chil3). Confocal microscopy showed that the macrophages internalize the SGSTF which co-localized after 1 h with MHC-II in their plasma membranes. Macrophages exposed to SGSTF and co-cultured with anti-CD3 pre-activated T CD4+ cells, enhanced the proliferation of CD4+ cells, induced high interferon-γ (IFN-γ) secretion, and elevated the expression of CD25 and CD69, molecules associated with cell activation. Similar assay using T CD4+ cells from DO11.10 mice and ovalbumin (OVA) peptide+SGSTF as stimuli, showed enhanced cell proliferation and OVA-specific IFN-γ secretion. These data are in-line with those indicating that the P1, P5, and P6 peptides of Schistosoma japonicum 28GST highly promote T-cell proliferation and Th1 response in vitro We found that such peptides are also present on Ts25GST and Ts26GST. It suggests that SGSTF activates peritoneal macrophages to a classically activated-like phenotype, and that these macrophages induce the differentiation of T CD4+ cells toward a Th1-type response.

A novel enolase from Taenia solium metacestodes and its evaluation as an immunodiagnostic antigen for porcine cysticercosis.

Cysticercosis is a worldwide parasitic disease of humans and pigs principally caused by infection with the larvae of the pork tapeworm Taenia solium. Through the use of the recently-made-available T. solium genome, we identified a gene within a novel 1448 bp ORF that theoretically encodes for a 433 amino acid-long protein and predicted to be an α-enolase closely related to enolases of other flatworms. Additional bioinformatic analyses revealed a putative plasminogen-binding region on this protein, suggesting a potential role for this protein in pathogenesis. On this basis, we isolated the mRNA encoding for this presumptive enolase from T. solium metacestodes and reverse-transcribed it into cDNA before subsequently cloning and expressing it in both E. coli (rEnoTs) and insect cells (rEnoTsBac), in a 6xHis tagged manner. The molecular weights of these two recombinant proteins were ∼48 and ∼50 kDa, respectively, with the differences likely attributable to differential glycosylation. We used spectrophotometric assays to confirm the enolase nature of rEnoTs as well as to measure its enzymatic activity. The resulting estimates of specific activity (60.000 U/mg) and Km (0.091 mM) are quite similar to the catalytic characteristics of enolases of other flatworms. rEnoTs also exhibited high immunogenicity, eliciting a strong polyclonal antibody response in immunized rabbits. We subsequently employed rEnoTsBac for use in an ELISA aimed at discriminating between healthy pigs and those infected with T. solium. This diagnostic assay exhibited a sensitivity of 88.4% (95% CI, 74.92%-96.11%) and a specificity of 83.7% (95% CI: 69.29%-93.19%). In conclusión, this study reports on and enzymatically characterizes a novel enolase from T. solium metacestode, and shows a potential use as an immunodiagnostic for porcine cysticercosis.

Molecular and biochemical characterization of Taenia solium α-enolase.

Enolase (EC 4.2.1.11) acts as a multifunctional enzyme in many organisms, being involved in metabolism, transcription regulation and pathogenesis. In the current study, the recombinant α-enolase from Taenia solium (His-Tseno) was prepared and antiserum against His-Tseno was generated in rabbits. Consequently, we analyzed the enzymatic characteristics, plasminogen binding activity, tissue localization and expression patterns of Tseno. The study demonstrated that the enzymatic activity of His-Tseno was enhanced at pH around 7.0-7.5 and affected by addition of metal ions. Kinetic measurements using 2-phospho-d-glycerate (2-PGA) substrates gave a specific activity of 60.72 ±â€¯0.84 U/mg and 1.1 mM of Km2-PGA value. Plasminogen binding assay showed that His-Tseno could bind to human plasminogen and generate plasmin activated by a tissue-type plasminogen activator (t-PA). In addition, the lysine analogue 6-aminocaproic acid (ε-ACA) could inhibit the binding of plasminogen to His-Tseno. Quantitative real-time PCR confirmed that Tseno was expressed 2.38 folds higher in the adult worms (p < 0.05) than in the cysticerci. Further, an immunolocalization assay indicated that native Tseno was mainly distributed in the tegument and eggs of gravid proglottis from adult T. solium. In conclusion, Tseno executes the innate glycolytic function to supply energy for the growth, egg production, and even invasion of T. solium.

Identification and characterization of Taenia solium enolase as a plasminogen-binding protein.

The larval stage of Taenia solium (cysticerci) is the causal agent of human and swine cysticercosis. When ingested by the host, T. solium eggs are activated and hatch in the intestine, releasing oncospheres that migrate to various tissues and evolve into cysticerci. Plasminogen (Plg) receptor proteins have been reported to play a role in migration processes for several pathogens. This work is aimed to identify Plg-binding proteins in T. solium cysticerci and determine whether T. solium recombinant enolase (rTsEnoA) is capable of specifically binding and activating human Plg. To identify Plg-binding proteins, a 2D-SDS-PAGE ligand blotting was performed, and recognized spots were identified by MS/MS. Seven proteins from T. solium cysticerci were found capable of binding Plg: fascicilin-1, fasciclin-2, enolase, MAPK, annexin, actin, and cytosolic malate dehydrogenase. To determine whether rTsEnoA binds human Plg, a ligand blotting was performed and the results were confirmed by ELISA both in the presence and absence of εACA, a competitive Plg inhibitor. Finally, rTsEnoA-bound Plg was activated to plasmin in the presence of tPA. To better understand the evolution of enolase isoforms in T. solium, a phylogenetic inference analysis including 75 enolase amino acid sequences was conducted. The origin of flatworm enolase isoforms, except for Eno4, is independent of their vertebrate counterparts. Therefore, herein we propose to designate tapeworm protein isoforms as A, B, C, and 4. In conclusion, recombinant enolase showed a strong plasminogen binding and activating activity in vitro. T. solium enolase could play a role in parasite invasion along with other plasminogen-binding proteins.

Resultados de dos encuestas dirigidas a inmigrantes y nativos del sureste español: salud, uso de servicios y necesidad de asistencia médica / Results of two surveys of immigrants and natives in Southeast Spain: health, use of services, and need for medical assistance

Objetivo. Comparar la salud, uso de servicios sanitarios y necesidad insatisfecha de atención médica (NIAM) entre inmigrantes y nativos del sureste español. Material y métodos. Estudio transversal de dos muestras representativas de población: inmigrante (n=1150) y nativa (n=1303; Encuesta Nacional de Salud). Se creó una única base de datos con ponderación específica para cada muestra y se estimaron razones de prevalencia (RP) mediante regresión multivariante. Resultados. Marroquíes, ecuatorianos y europeos del este (EE) declararon peor salud que los nativos (RPs [IC95%]: 2.45 [1.91-3.15]; 1.51 [1.28-1.79] y 1.44 [1.08-1.93], respectivamente). Los inmigrantes hicieron mayor uso de las urgencias (excepto EE) y consumieron menos fármacos. Los marroquíes mostraron la mayor diferencia en la frecuencia de NIAM (RP [IC95%]: 12.20 [5.25-28.37]), principalmente por razones laborales (46%). Conclusiones. La salud y el uso de servicios sanitarios difirieron significativamente entre inmigrantes y nativos. Destaca la NIAM alta en marroquíes por causa laboral.

Objective. To compare the self-perceived health, use of health services and unmet need for health care (UNHC) among immigrants and native populations of Southeast Spain. Materials and methods. Cross-sectional study of two representative samples of 1150 immigrants, and 1303 native participants from the National Health Survey. A single database was created with specific weights for each sample, and prevalence ratios (PR) were estimated by multivariate regression. Results. Moroccans, Ecuadorians and Eastern Europeans (EE) reported poorer health than the native population (PRs [CI95%]: 2.45 [1.91-3.15]; 1.51 [1.28-1.79] and 1.44 [1.08-1.93], respectively). Immigrants made greater use of emergencies that natives (except for EE) and had lower use of medication. Moroccan showed the greatest difference in the frequency of UNHC (PR [CI95%]:12.20 [5.25 - 28.37]), mainly because of working limitations (46%). Conclusions. The health status and use of health services among immigrants differ significantly from those of natives. Results highlight the higher frequency of UNHC among immigrants, especially high in Moroccans.

Triosephosphate isomerase of Taenia solium (TTPI): phage display and antibodies as tools for finding target regions to inhibit catalytic activity.

Previous studies demonstrated that antibodies against triosephosphate isomerase of Taenia solium (TTPI) can alter its enzymatic catalysis. In the present study, we used antibodies produced against the NH2-terminal region of TTPI (1/3NH2TTPI) and the phage display technology to find target regions to inhibit TTPI activity. As a first step, we obtained polyclonal antibodies against non-conserved regions from the 1/3NH2TTPI, which had an inhibitory effect of about 74 % on catalytic activity. Afterward, they were used to screen a library of phage-displayed dodecapeptides; as a result, 41 phage mimotope clones were isolated and grouped according to their amino acid sequence, finding the consensus A1 (VPTXPI), A2 (VPTXXI), B (LTPGQ), and D (DPLPR). Antibodies against selected phage mimotope clones were obtained by rabbit's immunization; these ones clearly recognized TTPI by both Western blot and ELISA. However, only the mimotope PDTS16 (DSVTPTSVMAVA) clone, which belongs to the VPTXXI consensus, raised antibodies capable of inhibiting the TTPI catalytic activity in 45 %. Anti-PDTS16 antibodies were confronted to several synthetic peptides that encompass the 1/3NH2TTPI, and they only recognized three, which share the motif FDTLQK belonging to the helix-α1 in TTPI. This suggests that this motif is the main part of the epitope recognized by anti-PDTS16 antibodies and revealed its importance for TTPI catalysis.

Purification and kinetic analysis of cytosolic and mitochondrial thioredoxin glutathione reductase extracted from Taenia solium cysticerci.

Thioredoxin glutathione reductases (TGRs) (EC 1.8.1.9) were purified to homogeneity from the cytosolic (cTsTGR) and mitochondrial (mTsTGR) fractions of Taenia solium, the agent responsible for neurocysticercosis, one of the major central nervous system parasitic diseases in humans. TsTGRs had a relative molecular weight of 132,000, while the corresponding value per subunit obtained under denaturing conditions, was of 62,000. Specific activities for thioredoxin reductase and glutathione reductase substrates for both TGRs explored were in the range or lower than values obtained for other platyhelminths and mammalian TGRs. cTsTGR and mTsTGR also showed hydroperoxide reductase activity using hydroperoxide as substrate. Km(DTNB) and Kcat(DTNB) values for cTsTGR and mTsTGR (88 µM and 1.9 s(-1); 45 µM and 12.6 s(-1), respectively) and Km(GSSG) and Kcat(GSSG) values for cTsTGR and mTsTGR (6.3 µM and 0.96 s(-1); 4 µM and 1.62 s(-1), respectively) were similar to or lower than those reported for mammalian TGRs. Mass spectrometry analysis showed that 12 peptides from cTsTGR and seven from mTsTGR were a match for gi|29825896 thioredoxin glutathione reductase [Echinococcus granulosus], confirming that both enzymes are TGRs. Both T. solium TGRs were inhibited by the gold compound auranofin, a selective inhibitor of thiol-dependent flavoreductases (I50 = 3.25, 2.29 nM for DTNB and GSSG substrates, respectively for cTsTGR; I50 = 5.6, 25.4 nM for mTsTGR toward the same substrates in the described order). Glutathione reductase activity of cTsTGR and mTsTGR exhibited hysteretic behavior with moderate to high concentrations of GSSG; this result was not observed either with thioredoxin, DTNB or NADPH. However, the observed hysteretic kinetics was suppressed with increasing amounts of both parasitic TGRs. These data suggest the existence of an effective substitute which may account for the lack of the detoxification enzymes glutathione reductase and thioredoxin reductase in T. solium, as has been described for very few other platyhelminths.

Genome-wide analysis of regulatory proteases sequences identified through bioinformatics data mining in Taenia solium.

BACKGROUND: Cysticercosis remains a major neglected tropical disease of humanity in many regions, especially in sub-Saharan Africa, Central America and elsewhere. Owing to the emerging drug resistance and the inability of current drugs to prevent re-infection, identification of novel vaccines and chemotherapeutic agents against Taenia solium and related helminth pathogens is a public health priority. The T. solium genome and the predicted proteome were reported recently, providing a wealth of information from which new interventional targets might be identified. In order to characterize and classify the entire repertoire of protease-encoding genes of T. solium, which act fundamental biological roles in all life processes, we analyzed the predicted proteins of this cestode through a combination of bioinformatics tools. Functional annotation was performed to yield insights into the signaling processes relevant to the complex developmental cycle of this tapeworm and to highlight a suite of the proteases as potential intervention targets. RESULTS: Within the genome of this helminth parasite, we identified 200 open reading frames encoding proteases from five clans, which correspond to 1.68% of the 11,902 protein-encoding genes predicted to be present in its genome. These proteases include calpains, cytosolic, mitochondrial signal peptidases, ubiquitylation related proteins, and others. Many not only show significant similarity to proteases in the Conserved Domain Database but have conserved active sites and catalytic domains. KEGG Automatic Annotation Server (KAAS) analysis indicated that ~60% of these proteases share strong sequence identities with proteins of the KEGG database, which are involved in human disease, metabolic pathways, genetic information processes, cellular processes, environmental information processes and organismal systems. Also, we identified signal peptides and transmembrane helices through comparative analysis with classes of important regulatory proteases. Phylogenetic analysis using Bayes approach provided support for inferring functional divergence among regulatory cysteine and serine proteases. CONCLUSION: Numerous putative proteases were identified for the first time in T. solium, and important regulatory proteases have been predicted. This comprehensive analysis not only complements the growing knowledge base of proteolytic enzymes, but also provides a platform from which to expand knowledge of cestode proteases and to explore their biochemistry and potential as intervention targets.

Sequence analysis and molecular characterization of Wnt4 gene in metacestodes of Taenia solium.

Wnt proteins are a family of secreted glycoproteins that are evolutionarily conserved and considered to be involved in extensive developmental processes in metazoan organisms. The characterization of wnt genes may improve understanding the parasite's development. In the present study, a wnt4 gene encoding 491amino acids was amplified from cDNA of metacestodes of Taenia solium using reverse transcription PCR (RT-PCR). Bioinformatics tools were used for sequence analysis. The conserved domain of the wnt gene family was predicted. The expression profile of Wnt4 was investigated using real-time PCR. Wnt4 expression was found to be dramatically increased in scolex evaginated cysticerci when compared to invaginated cysticerci. In situ hybridization showed that wnt4 gene was distributed in the posterior end of the worm along the primary body axis in evaginated cysticerci. These findings indicated that wnt4 may take part in the process of cysticerci evagination and play a role in scolex/bladder development of cysticerci of T. solium.

Cloning, characterization and functional expression of Taenia solium 17 beta-hydroxysteroid dehydrogenase.

The 17ß-hydroxysteroid dehydrogenases (17ß-HSD) are key enzymes involved in the formation (reduction) and inactivation (oxidation) of sex steroids. Several types have been found in vertebrates including fish, as well as in invertebrates like Caenorhabditis elegans, Ciona intestinalis and Haliotis diversicolor supertexta. To date limited information is available about this enzyme in parasites. We showed previously that Taenia solium cysticerci are able to synthesize sex steroid hormones in vitro when precursors are provided in the culture medium. Here, we identified a T. solium 17ß-HSD through in silico blast searches in the T. solium genome database. This coding sequence was amplified by RT-PCR and cloned into the pcDNA 3.1(+) expression vector. The full length cDNA contains 957bp, corresponding to an open reading frame coding for 319 aa. The highest identity (84%) at the protein level was found with the Echinococcus multilocularis 17ß-HSD although significant similarities were also found with other invertebrate and vertebrate 17ß-HSD sequences. The T. solium Tsol-17ßHSD belongs to the short-chain dehydrogenase/reductase (SDR) protein superfamily. HEK293T cells transiently transfected with Tsol17ß-HSD induced expression of Tsol17ß-HSD that transformed 3H-androstenedione into testosterone. In contrast, 3H-estrone was not significantly transformed into estradiol. In conclusion, T. solium cysticerci express a 17ß-HSD that catalyzes the androgen reduction. The enzyme belongs to the short chain dehydrogenases/reductase family and shares motifs and activity with the type 3 enzyme of some other species.

Evaluation of the non-catalytic binding function of Ts26GST a glutathione transferase isoform of Taenia solium.

Taenia solium glutathione transferase isoform of 26.5 kDa (Ts26GST) was observed to bind non-catalytically to porphyrins, trans-trans-dienals, bile acids and fatty acids, as assessed by inhibition kinetics, fluorescence spectroscopy and competitive fluorescence assays with 8-anilino-1-naphthalene sulfonate (ANS). The quenching of Ts26GST intrinsic fluorescence allowed for the determination of the dissociation constants (KD) for all ligands. Obtained data indicate that Ts26GST binds to all ligands but with different affinity. Porphyrins and lipid peroxide products inhibited Ts26GST catalytic activity up to 100% in contrast with only 20-30% inhibition observed for bile acids and two saturated fatty acids. Non-competitive type inhibition was observed for all enzyme inhibitor ligands except for trans-trans-2,4-decadienal, which exhibited uncompetitive type inhibition. The dissociation constant value KD = 0.7 µM for the hematin ligand, determined by competitive fluorescence assays with ANS, was in good agreement with its inhibition kinetic value Ki = 0.3 µM and its intrinsic fluorescence quenching KD = 0.7 µM. The remaining ligands did not displace ANS from the enzyme suggesting the existence of different binding sites. In addition to the catalytic activity of Ts26GST the results obtained suggest that the enzyme exhibits a ligandin function with broad specificity towards nonsubstrate ligands.

[Cathepsin L cysteine protease from Taenia solium: its biological role in the infection and potential use for the immunodiagnosis of neurocysticercosis]. / Cisteínoproteasas catepsinas L de Taenia solium: rol biológico en la infección y potencial uso para el inmunodiagnóstico de la neurocisticercosis.

Taenia solium is a plane helminth responsible for taeniasis and human cysticercosis, the latter being the result of the consumption of infective eggs. Cysticerci can develop in different human tissues, often in the central nervous system, causing neurocysticercosis (NCC). For the diagnosis of NCC, an adequate interpretation of clinical data, neuroimaging results and serological tests are required. However, serological tests could be improved by developing candidate antigens able to increase their sensibility and specificity. In the last years, a series of surface and secretory proteins of T. solium essential for the parasite-host interaction have been described. One of these families is cathepsin L cysteine proteases, which have a predominant role in the development and survival of the parasite. They take part in the tissue invasion, immune response evasion, excystation and encystment of cysticercus. They are considered potential antigens for the immunodiagnosis of neurocysticercosis.

Cisteínoproteasas Catepsinas L de Taenia solium: Rol biológico en la infección y potencial uso para el inmunodiagnóstico de la neurocisticercosis / Cathepsin L Cysteine Protease from Taenia solium: Its biological role in the infection and potential use for the immunodiagnosis of neurocysticercosis

Taenia solium es un helminto aplanado responsable de la teniosis y de la cisticercosis humana, siendo esta última producida por el consumo de huevos infectivos. Los cisticercos pueden desarrollarse en diferentes tejidos del hombre, frecuentemente en el sistema nervioso central causando la neurocisticercosis (NCC). Para el diagnóstico de la NCC se requiere de una adecuada interpretación de datos clínicos, resultados de neuroimagen y pruebas serológicas. Sin embargo, las pruebas serológicas podrían mejorarse con el desarrollo de antígenos candidatos capaces de incrementar su sensibilidad y especificidad. En los últimos años se han descrito una serie de proteínas de superficie y de secreción de T. solium esenciales para la interacción parásito-hospedero. Una de estas familias son las cisteínoproteasas catepsinas L, las cuales cumplen un rol preponderante para el desarrollo y supervivencia del parásito, participando en la invasión tisular, la evasión de la respuesta inmune, el desenquistamiento y enquistamiento del cisticerco. Son consideradas como antígenos potenciales para el inmunodiagnóstico de la neurocisticercosis.

Taenia solium is a plane helminth responsible for taeniasis and human cysticercosis, the latter being the result of the consumption of infective eggs. Cysticerci can develop in different human tissues, often in the central nervous system, causing neurocysticercosis (NCC). For the diagnosis of NCC, an adequate interpretation of clinical data, neuroimaging results and serological tests are required. However, serological tests could be improved by developing candidate antigens able to increase their sensibility and specificity. In the last years, a series of surface and secretory proteins of T. solium essential for the parasite-host interaction have been described. One of these families is cathepsin L cysteine proteases, which have a predominant role in the development and survival of the parasite. They take part in the tissue invasion, immune response evasion, excystation and encystment of cysticercus. They are considered potential antigens for the immunodiagnosis of neurocysticercosis.

Structural and biochemical studies of a recombinant 25.5 kDa glutathione transferase of Taenia solium metacestode (rTs25GST1-1).

In this work, we studied a recombinant mu-class glutathione transferase of 25.5 kDa from Taenia solium metacestode (rTs25GST1-1) that follows Michaelis­Menten kinetics with 1-chloro-2,4-dinitrobenzene (CDNB). The kinetic parameters obtained for rTs25GST1-1 with CDNB and GSH were V(max) =12.04 µmol/min/mg and K(m)=1.38 mM, and V(max) =10.20 µmol/min/mg and K(m)=0.90, respectively. The optimal activity was found at pH 8 in the 37-40 °C temperature range. Circular dichroism studies for rTs25GST1-1 at different pH showed that it maintains a typical α-helix structure between pH 6.5-7.5, but loses it between pH 8 and 8.5. Thermal CD assays showed rTs25GST1-1 barely changed its secondary structure. Unfolding/refolding assays showed that rTs25GST1-1 retained its structure up to 40 °C without loss of its activity. Additionally, exposure of rTs25GST1-1 to cumene hydroperoxide did not produce significant changes in its structure and only affected 50% of its activity.

Characterization of a monoclonal antibody that specifically inhibits triosephosphate isomerase activity of Taenia solium.

In the present study, we obtained and characterized partially a monoclonal antibody (4H11D10B11 mAb) against triosephosphate isomerase from Taenia solium (TTPI). This antibody recognized the enzyme by both ELISA and western blot and was able to inhibit its enzymatic activity in 74%. Moreover, the antigen-binding fragments (Fabs), products of digestion of the monoclonal antibody with papain, retained almost the same inhibitory effect. We determined the binding site by ELISA; synthetic peptides containing sequences from different non-conserved regions of the TTPI were confronted to the 4H11D10B11 mAb. The epitope recognized by the monoclonal antibody was located on peptide TTPI-56 (ATPAQAQEVHKVVRDWIRKHVDAGIADKARI), and an analysis of mimotopes, obtained with the 4H11D10B11 mAb, suggests that the epitope spans the sequence WIRKHVDAGIAD, residues 193-204 of the enzyme. This epitope is located within helix 6, next to loop 6, an essential active loop during catalysis. The antibody did not recognize triosephosphate isomerase from man and pig, definitive and intermediary hosts of T. solium, respectively. Furthermore, it did not bind to the catalytic site, since kinetic analysis demonstrated that inhibition had a non-competitive profile.

Identification of novel glutathione transferases in Echinococcus granulosus. An evolutionary perspective.

Glutathione transferase enzymes (GSTs) constitute a major detoxification system in helminth parasites and have been related to the modulation of host immune response mechanisms. At least three different GSTs classes have been described in Platyhelminthes: Mu, Sigma and Omega. Mining the genome of Echinococcus multilocularis and the ESTs databases of Taenia solium and E. granulosus identified two new GSTs from the cestode E. granulosus, named EgGST2 and EgGST3. It also revealed that the Omega class of GSTs was absent from the Taenidae family. EgGST2 and EgGST3 are actively expressed in the parasite. In order to know the origin of these new GSTs, in silico analyses were performed. While EgGST2 is classified as belonging to the Sigma class, the data obtained for EgGST3 allowed a less clear interpretation. The study of the evolutionary relatedness based on the C-terminal domain sequence, gene structure conservation and three-dimensional structure predictions, suggests that EgGST3 is derived from the Platyhelminthes' Sigma-class cluster. Interestingly, the N-terminal domain displays some characteristic Omega-class residues, including a Cys residue that is likely to be involved in the catalytic mechanism. We discuss different evolutionary scenarios that could explain the observed patterns.