Evaluation of recombinant HP6-Tsag, an 18 kDa Taenia saginata oncospheral adhesion protein, for the diagnosis of cysticercosis

Generation and application of a monoclonal antibody against the 18-kDa oncosphere antigen of Taenia pisiformis

Taenia pisiformis is a parasite that causes cysticercosis pisiformis, which has acquired economic relevance because of its effects on animal welfare and production. A useful assay for the detection of T. pisiformis is needed for the prevention of cysticercosis pisiformis and control of the parasite. The 18-kDa oncosphere antigen is expressed in the oncosphere of several cysticerci in species of the genus Taenia, including T. pisiformis. This protein plays an important role in tissue invasion and has extensive applications in diagnosis. In this study, the T. pisiformis 18-kDa oncosphere antigen (TPO18) was expressed in soluble form and successfully purified for use in the production of monoclonal antibodies (MAbs) against TPO18. Twenty hybridomas were obtained using ELISA, and the subcloning process identified three positive hybridoma cell lines, which were designated as 4E8, 5G5, and 7E8. MAb 7E8 exhibited the highest titer and had an IgG2b heavy chain and a kappa light chain. Western blot analysis demonstrated that MAb 7E8 reacted with GST-TPO18. Immunohistochemistry showed that TPO18 was widely distributed in the drape and wall of uteri in adults of T. pisiformis adults and in the fibrous layer of the sucker and cyst cavity of T. pisiformis cysticerci. This research will provide a foundation for the development of diagnostic tools and will contribute to a better understanding of the functions of TPO18.

Development of the multi-epitope chimeric antigen rqTSA-25 from Taenia saginata for serological diagnosis of bovine cysticercosis

Bovine cysticercosis is a worldwide distributed zoonosis caused by the larval form of Taenia saginata present in bovine muscles. The diagnosis is based on the postmortem inspection at slaughterhouses and consists of the macroscopic visualization of lesions caused by cysticercosis in muscle sites. However, parasitized animals can pass unnoticed during sanitary inspection. Thus, the objective of this study was to characterize and evaluate the performance of different peptides from different regions of T. saginata for the cysticercosis diagnosis using enzyme-linked immunosorbent assay. We generated and evaluated a new recombinant protein chimera derived from the fusion of different peptides. We selected three distinct regions of T. saginata and predicted six peptides with antigenic potential (EP2–EP7). These peptides were analyzed individually and selected for generating a new chimeric recombinant protein. The new protein was termed rqTSA-25, and its performance rates were: 93.3% sensitivity (confidence interval (CI) = 76–98%), 95.3% specificity (CI = 82–99%), 93% positive predictive value (CI = 76–98%), 95% negative predictive value (CI = 82–99%), and 95% accuracy. In the immunoblot, this protein showed no false positive or false negative reaction. Thus, the use of rqTSA-25 is recommended for the diagnosis of bovine cysticercosis.

Taenia saginata cysticercosis occurs worldwide. The prevalence related is higher mainly in developing countries, causing damage to public health and economic losses. Through our study, a new antigen with high diagnostic potential was developed for use in laboratory serological tests, aiming at the detection of bovine cysticercosis. In this way, it was possible to contribute significantly to the improvement of the diagnosis of this disease.

Evaluation of a synthetic peptide from the Taenia saginata 18kDa surface/secreted oncospheral adhesion protein for serological diagnosis of bovine cysticercosis

Bovine cysticercosis is a zoonotic infection widely spread throughout Brazil, creating a burden on hygiene maintenance and the economy. Diagnosis of cysticercosis usually relies on post mortem inspection of carcasses in slaughterhouses. This detection method provides only low sensitivity. Recent advancements have improved the performance of serologic tests, such as ELISA, providing greater sensitivity and specificity. The objective of the current study was to identify and evaluate a synthetic peptide derived from the Taenia saginata 18kDa oncospheric surface protein for the diagnosis of bovine cysticercosis in ELISA. Test performance of the identified peptide was compared to an ELISA based on a heterologous crude Taenia crassiceps antigen (Tcra), widely used for the sero-diagnosis of bovine cysticercosis. Based on the primary sequence of an in silico structural model of the 18kDa protein, an epitope region designated EP1 was selected (46-WDTKDMAGYGVKKIEV-61). The peptide derived from this region yielded 91.6% (CI=80-96%) sensitivity and 90% (CI=82-95%) specificity when used in an ELISA, whereas the crude antigen yielded 70% (CI=56-8%) sensitivity and 82% (CI=73-89%) specificity. Thus, we conclude that EP1 has higher diagnostic potential for detecting bovine cysticercosis than the crude antigen Tcra.

A lateral flow assay (LFA) for the rapid detection of extraparenchymal neurocysticercosis using cerebrospinal fluid

A lateral flow assay (LFA) for the diagnosis and monitoring of extraparenchymal neurocysticercosis, has been developed. The assay is based on the use of the monoclonal antibody HP10, and when applied to cerebrospinal fluid, correctly identified 34 cases of active extraparenchymal neurocysticercosis, but was negative with 26 samples from treated and cured neurocysticercosis patients and with 20 samples from unrelated neurological diseases. There was complete agreement between the HP10 Ag-ELISA results and the HP10-LFA. The HP10-LFA thus has utility for diagnosis and treatment of extraparenchymal neurocysticercosis, frequently a more dangerous form of the infection.

Usefulness of serological ELISA assay for Taenia saginata to detect naturally infected bovines

Bovine cysticercosis, a cosmopolitan disease caused by Taenia saginata, leads to economic losses due to carcass devaluation at slaughter. Sanitary inspection at slaughterhouses, the routine diagnostic method in Brazil, lacks the necessary sensitivity to detect the mildly infected cattle that are typically encoutered in Brazil. In this study we have tested cattle sera from animals diagnosed as positive and negative by veterianry inspection for (1) anti-parasite antibodies using metacestodes antigens (T. solium vesicular fluid and T. saginata secretions) and (2) the HP10 secreted antigen of viable metacestodes. The cut-off values were calculated by ROC curve for intense and mild infections conditions, and by the classical method ( for negative samples). The sensitivity and specificity of these diagnostic tests were different depending on the assumed cut-off value and, importantly, whether the infection was mild or intense. In spite of these observations, however, such ELISA assays for serum antibodies and parasite antigens constitute an important tool for epidemiological porposes, and in establishing priorities for the control of bovine cysticercosis.

Taenia solium metacestode fasciclin-like protein is reactive with sera of chronic neurocysticercosis

OBJECTIVES

Neurocysticercosis (NC), an infection of the central nervous system with Taenia solium metacestodes (TsM), invokes a formidable neurological disease. A bundle of antigens is applicable for serodiagnosis of active cases, while they demonstrate fairly low reactivity against sera of chronic NC. Identification of sensitive biomarkers for chronic NC is critical for appropriate management of patients.

METHODS

Proteome analysis revealed several isoforms of 65- and 83-kDa TsM fasciclin-like proteins (TsMFas) to be highly reactive with sera of chronic NC. A cDNA encoding one of the 83-kDa TsMFas (TsMFas1) was isolated from a cDNA library. We expressed a recombinant protein (rTsMFas1) and evaluated its diagnostic potential employing sera from chronic NC (n = 80), tissue-invasive cestodiases (n = 169) and trematodiases (n = 80) and those of normal controls (n = 50).

RESULTS

Secretory TsMFas1 was composed of 766 amino acid polypeptide and harboured fasciclin and fasciclin-superfamily domains. The protein was constitutively expressed in metacestode and adult stages, with preferential locality in the scolex. Bacterially expressed rTsMFas1 exhibited 78.8% sensitivity (63/80 cases) and 93% specificity (278/299 samples) in diagnosing chronic NC. Some cross-reactivity was observed with sera of cystic echinococcosis (10/56, 17.8%) and sparganosis (4/50, 8%). Positive and negative predictive values were 75% and 95.5%, respectively.

CONCLUSION

TsM fasciclin-like protein may be useful for differential diagnosis of chronic NC in clinical settings, especially where both NC and other infectious cerebral granulomatoses are prevalent.

Advances in diagnosis and spatial analysis of cysticercosis and taeniasis

Human cysticercosis, caused by accidental ingestion of eggs of Taenia solium, is one of the most pathogenic helminthiases and is listed among the 17 WHO Neglected Tropical Diseases. Controlling the life-cycle of T. solium between humans and pigs is essential for eradication of cysticercosis. One difficulty for the accurate detection and identification of T. solium species is the possible co-existence of two other human Taenia tapeworms (T. saginata and T. asiatica, which do not cause cysticercosis in humans). Several key issues for taeniasis/cysticercosis (T/C) evidence-based epidemiology and control are reviewed: (1) advances in immunological and molecular tools for screening of human and animals hosts and identification of Taenia species, with a focus on real-time detection of taeniasis carriers and infected animals in field community screenings, and (2) spatial ecological approaches that have been used to detect geospatial patterns of case distributions and to monitor pig activity and behaviour. Most recent eco-epidemiological studies undertaken in Sichuan province, China, are introduced and reviewed.

Head-to-head comparison of three vaccination strategies based on DNA and raw insect-derived recombinant proteins against Leishmania

Parasitic diseases plague billions of people among the poorest, killing millions annually, and causing additional millions of disability-adjusted life years lost. Leishmaniases affect more than 12 million people, with over 350 million people at risk. There is an urgent need for efficacious and cheap vaccines and treatments against visceral leishmaniasis (VL), its most severe form. Several vaccination strategies have been proposed but to date no head-to-head comparison was undertaken to assess which is the best in a clinical model of the disease. We simultaneously assayed three vaccination strategies against VL in the hamster model, using KMPII, TRYP, LACK, and PAPLE22 vaccine candidate antigens. Four groups of hamsters were immunized using the following approaches: 1) raw extracts of baculovirus-infected Trichoplusia ni larvae expressing individually one of the four recombinant proteins (PROT); 2) naked pVAX1 plasmids carrying the four genes individually (DNA); 3) a heterologous prime-boost (HPB) strategy involving DNA followed by PROT (DNA-PROT); and 4) a Control including empty pVAX1 plasmid followed by raw extract of wild-type baculovirus-infected T. ni larvae. Hamsters were challenged with L. infantum promastigotes and maintained for 20 weeks. While PROT vaccine was not protective, DNA vaccination achieved protection in spleen. Only DNA-PROT vaccination induced significant NO production by macrophages, accompanied by a significant parasitological protection in spleen and blood. Thus, the DNA-PROT strategy elicits strong immune responses and high parasitological protection in the clinical model of VL, better than its corresponding naked DNA or protein versions. Furthermore, we show that naked DNA coupled with raw recombinant proteins produced in insect larvae biofactories -the cheapest way of producing DNA-PROT vaccines- is a practical and cost-effective way for potential "off the shelf" supplying vaccines at very low prices for the protection against leishmaniases, and possibly against other parasitic diseases affecting the poorest of the poor.

The highly antigenic 53/25 kDa Taenia solium protein fraction with cathepsin-L like activity is present in the oncosphere/cysticercus and induces non-protective IgG antibodies in pigs

Cathepsin L-like proteases are secreted by several parasites including Taenia solium. The mechanism used by T. solium oncospheres to degrade and penetrate the intestine and infect the host is incompletely understood. It is assumed that intestinal degradation is driven by the proteolytic activity of enzymes secreted by the oncosphere. Blocking the proteolytic activity by an antibody response would prevent the oncosphere penetration and further infection. Serine and cysteine proteases including chymotrypsin, trypsin, elastase, and cathepsin L, are secreted by T. solium and Taenia saginata oncospheres when cultured in vitro, being potential vaccine candidates. However, the purification of a sufficient quantity of proteases secreted by oncospheres to conduct a vaccine trial is costly and lengthy. A 53/25 kDa cathepsin L-like fraction partially purified from T. solium cyst fluid was described previously as an important antigen for immunodiagnostics. In this study we found that this antigen is present in the T. solium oncosphere and is also secreted by the cysticercus. This protein fraction was tested for its ability to protect pigs against an oral challenge with T. solium oncospheres in a vaccine trial. IgG antibodies against the 53/25 kDa cathepsin L-like protein fraction were elicited in the vaccinated animals but did not confer protection.

Immunodiagnosis of neurocysticercosis: ways to focus on the challenge

Neurocysticercosis (NCC) is a disease of the central nervous system that is considered a public health problem in endemic areas. The definitive diagnosis of this disease is made using a combination of tools that include imaging of the brain and immunodiagnostic tests, but the facilities for performing them are usually not available in endemic areas. The immunodiagnosis of NCC is a useful tool that can provide important information on whether a patient is infected or not, but it presents many drawbacks as not all infected patients can be detected. These tests rely on purified or semipurified antigens that are sometimes difficult to prepare. Recent efforts have focused on the production of recombinant or synthetic antigens for the immunodiagnosis of NCC and interesting studies propose the use of new elements as nanobodies for diagnostic purposes. However, an immunodiagnostic test that can be considered as "gold standard" has not been developed so far. The complex nature of cysticercotic disease and the simplicity of common immunological assumptions involved explain the low scores and reproducibility of immunotests in the diagnosis of NCC. Here, the most important efforts for developing an immunodiagnostic test of NCC are listed and discussed. A more punctilious strategy based on the design of panels of confirmed positive and negative samples, the use of blind tests, and a worldwide effort is proposed in order to develop an immunodiagnostic test that can provide comparable results. The identification of a set of specific and representative antigens of T. solium and a thorough compilation of the many forms of antibody response of humans to the many forms of T. solium disease are also stressed as necessary.

Specific phage-displayed peptides discriminate different forms of neurocysticercosis by antibody detection in the serum samples

Neurocysticercosis (NC), caused by Taenia solium metacestode, infects the central nervous system and is a devastating parasitic infection. Diagnosis is based on symptoms, imaging, serology and epidemiology. Current markers present variable sensitivity and specificity, frequent cross-reactions and are not able to discriminate NC clinical forms. The aim of this study was to select mimotopes of T. solium metacestode antigens that may be used in NC immunodiagnosis, specifically to discriminate between active and inactive forms. A random peptide phage display library was screened against IgY from chickens immunized with total saline extract from T. solium metacestodes and validated against 110 serum samples, classified into active NC (18), inactive NC (22), cross-reactive parasitic diseases (40) and healthy controls (30). We have successfully selected seven peptides with significant immunoreactivity to IgG of NC patients, with sensitivity ranging from 95.5% to 100% to detect the inactive form and specificity varied from 85.7% to 94.3%. One phage-displayed peptide (Cc48) can be directly used as biomarker to distinguish inactive from active forms with an accuracy of 95.7%, and this novel mimotope may also be used as an auxiliary tool to neuroimaging tests and treatment follow-up.

Insect larvae biofactories as a platform for influenza vaccine production

Increased production capacity is one of the most important priorities for seasonal and pandemic influenza vaccines. In the present study, we used a baculovirus-insect larvae system (considered small, living biofactories) to improve the production of recombinant influenza virus H1N1 hemagglutinin (HA). Insect larvae produced four-fold more HA protein than insect cells per biomass unit (1 g of fresh larvae weight). A single infected Trichoplusia ni larva produced up to 113 μg of soluble and easily purified recombinant HA, an amount similar to that produced by 1.2×10(8) Sf21 insect cells infected by the same baculovirus. The use of the KDEL endoplasmic reticulum retention signal fused to the HA protein further increased recombinant protein production. Larvae-derived HA was immunogenically functional in vaccinated mice, inducing the generation of hemagglutination inhibition antibodies and a protective immune response against a lethal challenge with a highly virulent virus. The productivity, scalability and cost efficiency of small, living biofactories based on insect larvae suggest a broad-based strategy for the production of recombinant subunit vaccines against seasonal or pandemic influenza as an alternative to fermentation technologies.

Taenia saginata metacestode antigenic fractions without affinity to concanavalin A are an important source of specific antigens for the diagnosis of human neurocysticercosis

Taenia saginata metacestode antigens have been constituted a useful alternative antigen for neurocysticercosis (NC) serodiagnosis, particularly due to an increasing difficulty to obtain Taenia solium homologous antigen. Cross-reactivity with Echinococcus granulosus infection occurs in homologous and heterologous antigens and could be avoided by using different purified methods. The present study evaluated antigen fractions obtained from saline extracts of T. saginata metacestodes purified by affinity chromatography with jacalin or concanavalin A (ConA) lectins to detect IgG antibodies by enzyme-linked immunosorbent assay (ELISA) and immunoblot analysis to diagnose human NC. Serum samples were collected from 142 individuals: 40 of them were diagnosed with NC, 62 presented Taenia sp. and other parasites, and 40 were apparently healthy individuals. The jacalin- and ConA-unbound fractions demonstrated sensitivity and specificity higher than those of bound fractions. Among unbound fractions, ConA demonstrated statistically higher sensitivity and specificity by ELISA (90% and 93.1%, respectively). By immunoblot assay, the 64- to 68-kDa component from the ConA-unbound fraction showed 100% sensitivity and specificity, making this component suitable for use as a specific antigen for diagnosis of NC. To our knowledge, this is the first report showing the relevance of using the unbound ConA fraction of T. saginata metacestodes to diagnose NC. In conclusion, the results obtained herein clearly demonstrate that antigenic fractions without affinity to ConA, obtained from T. saginata metacestodes, are an important source of specific peptides and are efficient in the diagnosis of NC when tested by immunoblot assay.

Peptide epitopes of the Taenia solium antigen Ts8B2 are immunodominant in human and porcine cysticercosis

Ts8B2 is a gene which encodes for a member of the Taenia solium metacestode 8kDa antigen family. Since the Ts8B2-GST recombinant protein compares very favourably with other diagnostic antigens, and in order to study the antigenic nature and structure of this molecule, the Ts8B2 was expressed in prokaryotic and eukaryotic systems. The diagnostic potential of the recombinant Ts8B2 proteins was evaluated by enzyme-linked immunosorbent assays (ELISA) using a collection of serum and cerebrospinal fluid (CSF) samples from patients with clinically defined neurocysticercosis (NCC), and also sera from T. solium infected pigs. Despite the predicted glycosylation of the Ts8B2-Bac recombinant protein, there was very little difference in assay sensitivity/specificity when the Ts8B2 reagent was expressed in either prokaryotic or eukaryotic systems, suggesting that peptidic Ts8B2 epitopes are immunodominant in porcine cysticercosis and human neurocysticercosis. Conveniently, production of recombinant Ts8B2 in Escherichia coli is economical and facile, making it a feasible and practical choice as a diagnostic reagent for use in endemic areas. The Ts8B2 ELISA is particularly useful for the diagnosis of active as opposed to inactive cases of NCC and conduct of the assay is also facilitated by the fact that assay sensitivity is significantly greater when serum as opposed to CSF samples are employed.

Transcriptome analysis of Taenia solium cysticerci using Open Reading Frame ESTs (ORESTES)

BACKGROUND

Human infection by the pork tapeworm Taenia solium affects more than 50 million people worldwide, particularly in underdeveloped and developing countries. Cysticercosis which arises from larval encystation can be life threatening and difficult to treat. Here, we investigate for the first time the transcriptome of the clinically relevant cysticerci larval form.

RESULTS

Using Expressed Sequence Tags (ESTs) produced by the ORESTES method, a total of 1,520 high quality ESTs were generated from 20 ORESTES cDNA mini-libraries and its analysis revealed fragments of genes with promising applications including 51 ESTs matching antigens previously described in other species, as well as 113 sequences representing proteins with potential extracellular localization, with obvious applications for immune-diagnosis or vaccine development.

CONCLUSION

The set of sequences described here will contribute to deciphering the expression profile of this important parasite and will be informative for the genome assembly and annotation, as well as for studies of intra- and inter-specific sequence variability. Genes of interest for developing new diagnostic and therapeutic tools are described and discussed.

The Taenia saginata homologue of the major surface antigen of Echinococcus spp. is immunogenic and 97% identical to its Taenia solium homologue

The TEG-Tsag gene of Taenia saginata is homologous to the genes expressing the two major surface antigens of Echinococcus spp. (EM10 and EG10). Surface antigens of parasites are logical candidates for vaccines, and in this paper we demonstrate that cattle vaccinated with the recombinant TEG-Tsag protein, either used singly or in conjunction with the recombinant HP6-Tsag protein, the major 18 kDa surface/secreted antigen of T. saginata oncospheres, produce excellent antibody responses to both these recombinant proteins. Thus TEG-Tsag may have utility as a vaccine and also as a diagnostic tool for bovine cysticercosis. In addition, as we now demonstrate a 97% homology between TEG-Tsag and its Taenia solium homologue, TEG-Tsol, this latter molecule may have similar potential in the control of human and porcine cysticercosis. The TEG molecule is characterized by an N-terminal FERM domain and a C-terminal ERM domain which are found in a number of cytoskeletal-associated proteins located at the interface between the plasma membrane and the cytoskeleton and in proteins that interact with lipid membranes. The FERM domain is also postulated to bind to adhesion proteins, in a PIP2-regulated fashion, providing a link between cytoskeletal signals and membrane dynamics. Thus TEG protein may play a role in tegument function and interaction with the host.

Characterization of a novel Taenia solium oncosphere antigen

Infections due to Taenia solium in humans (taeniasis/cysticercosis) remain a complex health problem, particularly in developing countries. We identified two oncosphere proteins that might protect the porcine intermediate host against cysticercosis and therefore help prevent disease in humans. One of these proteins was further identified by two-dimensional gel electrophoresis and micro-sequencing. The gene encoding this protective protein was also identified, cloned and characterized. The native 31.5 kDa protein Tso31 has four variants at the cDNA level. The longest sequence from which the others seem to derive, encodes a 253 amino acid peptide. The predicted protein has a molecular weight of 25.1 kDa, one putative N-glycosylation site, two fibronectin type III domains, and one C terminal transmembrane domain. The gene structure of the protein consists of four exons and three introns. The finding of one gene and four different cDNAs for Tso31 suggests the existence of a possible mechanism of differential splicing in this parasite. The Tso31 protein is exclusive to T. solium oncospheres with a putative protein structure of an extra-cellular receptor-like protein. The Tso31 protein was expressed as a recombinant protein fused to GST and tested in a vaccine to determine its effectiveness in protecting pigs against cysticercosis. Only two pigs out of eight vaccinated were protected and although the total median number of cyst decreased in vaccinated pigs compared to controls this decrease was not statistically significant (P = 0.09).