Assessment of antigenic fractions of varying hydrophobicity from Taenia solium metacestodes for the diagnosis of human neurocysticercosis

IgY antibody and human neurocysticercosis: a novel approach on immunodiagnosis usingTaenia crassicepshydrophobic antigens

Human neurocysticercosis (NCC) is a worldwide neglected disease caused byTaenia soliummetacestode and responsible for various complications and neurological disorders. This study aimed to evaluate the use of specific immunoglobulin Y (IgY) produced by laying hens immunized with a hydrophobic fraction ofTaenia crassicepsmetacestodes (hFTc) in NCC diagnosis. Egg yolk IgY antibodies were fractionated, purified and characterized. Enzyme-linked immunosorbent assay (ELISA) was carried out to evaluate the production kinetics and avidity maturation of anti-hFTcIgY antibodies throughout the IgY obtention process. Antigen recognition tests were carried out by Western blotting and immunofluorescence antibody test using purified and specific anti-hFTcIgY antibodies for detection of parasitic antigens ofT. crassicepsandT. soliummetacestodes. Sandwich ELISA was performed to detect circulating immune complexes formed by IgG and parasitic antigens in human sera. The results showed high diagnostic values (93.2% sensitivity and 94.3% specificity) for immune complexes detection in human sera with confirmed NCC. In conclusion, specific IgY antibodies produced from immunized hens with hFTcantigens were efficient to detectT. soliumimmune complexes in human sera, being an innovative and potential tool for NCC immunodiagnosis.

Antigenic fractions from Taenia crassiceps metacestodes obtained by hydrophobicity for the immunodiagnosis of active and inactive forms of neurocysticercosis in human cerebrospinal fluid samples

This study aimed to evaluate the total extract of Taenia crassiceps metacestodes (TC) and its antigenic fractions obtained by Triton X-114 fractionation techniques, such as detergent (DC) and aqueous (AC), in the immunodiagnosis of human neurocysticercosis (NCC). Cerebrospinal fluid samples were divided into two groups: Group 1 (n=40), which was further divided into active (n=20) and inactive (n=20) NCC, and Group 2 (control group), which comprised 39 CSF samples from patients who had another neurological disorder, were suffering from other infectious diseases of the brain or had other parasitic infections. The total extracts and antigenic fractions were tested by enzyme-linked immunosorbent assay (ELISA) to detect human IgG anti-Taenia solium. T. crassiceps fractions (DC and AC) showed the same value of sensitivity (Se), 100%, for active and inactive NCC and a specificity (Sp) of 97.4%. The DS fraction obtained from T. solium showed 100% Se for active NCC, 95% Se for inactive NCC and a 92.3% Sp. The AS fraction obtained from T. solium showed 100% Se for both active and inactive NCC and a 94.9% Sp. There was a positive correlation between the total saline extract of T. crassiceps (TC) and T. solium (TS) and their fractions (DC, AC, DS and AS). Positive predictive value, negative predictive value, diagnostic efficiency and Youden index were calculated. In conclusion, these results demonstrated that detergent and aqueous fractions obtained from T. crassiceps metacestodes are important sources of specific antigens and are efficient for immunodiagnosis of active and inactive NCC.

Usefulness of gel filtration fraction as potential biomarker for neurocysticercosis in serum: towards a new diagnostic tool

There is an increasing interest in improving neurocysticercosis (NCC) diagnosis through the search of new and alternative antigenic sources, as those obtained from heterologous antigens. The aim of this study was to obtain potential biomarkers for NCC diagnosis after gel filtration chromatography [gel filtration fraction (GFF)] from the total saline extract (SE) from Taenia saginata metacestodes, followed by protein identification and application in immunodiagnostic. SE and GFF proteic profiles were characterized in gel electrophoresis, and diagnostic performance was verified by testing 160 serum samples through enzyme-linked immunosorbent assay and immunoblotting. Sensitivity (Se), specificity (Sp) and other diagnostic parameters were calculated. Polypeptides of interest in the diagnosis of human NCC present at GFF were analysed by mass spectrometry (MS) and B-cell epitopes were predicted. GFF had the best diagnostic parameters: Se 93·3%; Sp 93%; AUC 0·990; LR+ = 13·42 and LR− = 0·07, and proved to be useful reacting with serum samples in immunoblotting. Proteic profile ranged from 64 to 68 kDa and enolase and calcium binding protein calreticulin precursor were identified after MS. The enolase and calcium-binding protein calreticulin precursor showed 18 and 10 predicted B-cell epitopes, respectively. In conclusion we identified important markers in the GFF with high efficiency to diagnose NCC.

Differential antigenic protein recovery from Taenia solium cyst tissues using several detergents

Human and porcine cysticercosis is caused by the larval stage of the flatworm Taenia solium (Cestoda). The protein extracts of T. solium cysts are complex mixtures including cyst's and host proteins. Little is known about the influence of using different detergents in the efficiency of solubilization-extraction of these proteins, including relevant antigens. Here, we describe the use of CHAPS, ASB-14 and Triton X-100, alone or in combination in the extraction buffers, as a strategy to notably increase the recovery of proteins that are usually left aside in insoluble fractions of cysts. Using buffer with CHAPS alone, 315 protein spots were detected through 2D-PAGE. A total of 255 and 258 spots were detected using buffers with Triton X-100 or ASB-14, respectively. More protein spots were detected when detergents were combined, i.e., 2% CHAPS, 1% Triton X-100 and 1% ASB-14 allowed detection of up to 368 spots. Our results indicated that insoluble fractions of T. solium cysts were rich in antigens, including several glycoproteins that were sensitive to metaperiodate treatment. Host proteins, a common component in protein extracts of cysts, were present in larger amounts in soluble than insoluble fractions of cysts proteins. Finally, antigens present in the insoluble fraction were more appropriate as a source of antigens for diagnostic procedures.

Serodiagnosis of human neurocysticercosis using antigenic components of Taenia solium metacestodes derived from the unbound fraction from jacalin affinity chromatography

The aim of the present study was to analyse Taenia solium metacestode antigens that were derived from the unbound fraction of jacalin affinity chromatography and subsequent tert-octylphenoxy poly (oxyethylene) ethanol Triton X-114 (TX-114) partitioning in the diagnosis of human neurocysticercosis (NCC). Immunoassays were designed to detect T. solium-specific IgG antibodies by ELISA and immunoblot. Serum samples were collected from 132 individuals who were categorised as follows: 40 had NCC, 62 presented Taenia spp or other parasitic diseases and 30 were healthy individuals. The jacalin-unbound (J unbound ) fraction presented higher sensitivity and specificity rates than the jacalin-bound fraction and only this fraction was subjected to subsequent TX-114 partitioning, resulting in detergent (DJ unbound ) and aqueous (AJ unbound ) fractions. The ELISA sensitivity and specificity were 85% and 84.8% for J unbound , 92.5% and 93.5% for DJ unbound and 82.5% and 82.6% for AJ unbound . By immunoblot, the DJ unbound fraction showed 100% sensitivity and specificity and only serum samples from patients with NCC recognised the 50-70 kDa T. solium-specific components. We conclude that the DJ unbound fraction can serve as a useful tool for the differential immunodiagnosis of NCC by immunoblot.

Genetic polymorphism in Taenia solium metacestodes from different Brazilian geographic areas

The aim of the present study is to investigate genetic polymorphisms in Taenia solium metacestodes from different Brazilian geographical areas and to relate them to antibody recognition in serum samples of neurocysticercosis (NC) patients. Metacestodes were obtained from the Distrito Federal (DF), Bahia, Minas Gerais (MG) and São Paulo (SP) regions of Brazil. Samples of human sera from 49 individuals with NC, 68 individuals with other helminthiasis and 40 healthy volunteers were analysed (157 individuals in total). Antigens were prepared and used in enzyme-linked immunosorbent assay and western blotting assays to detect specific immunoglobulin G antibodies. Genetic distances between metacestode populations were analysed using random amplified polymorphic DNA (RAPD) analysis. Our results show that there was a higher frequency of reactivity in the DF region in the sera from NC patients (p < 0.05), while discrimination between active and inactive NC was seen only in extracts from the MG and SP regions (p < 0.05). Using RAPD, the sample from the DF region presented a greater increase compared to the other regions. A relationship between genetic polymorphisms among T. solium metacestodes from different areas in Brazil and the differences in antibody detection in patients with NC were established.

Hydrophobic fraction of Taenia saginata metacestodes, rather than hydrophilic fraction, contains immunodominant markers for diagnosing human neurocysticercosis

INTRODUCTION

Considering that alternative antigens for diagnosing neurocysticercosis continue to be a challenge because of the increasing difficulty in obtaining parasites from naturally infected pigs for preparation of Taenia solium homologous antigen, the aim of the present study was to evaluate the detergent (D) and aqueous (A) fractions from saline extract of Taenia saginata metacestodes for diagnosing neurocysticercosis.

METHODS

Taenia saginata was obtained from naturally infected bovines in the Triângulo Mineiro region, State of Minas Gerais, Brazil. The carcasses came from cold storage units and had been slaughtered in accordance with the inspection technique recommended by the Federal Inspection Service. The D and A fractions were obtained by using Triton X-114 (TX-114). Serum samples were obtained from 40 patients with a diagnosis of neurocysticercosis, 45 with other parasitic diseases and 30 from apparently normal individuals. IgG antibody levels were evaluated using the ELISA and immunoblotting assays.

RESULTS

The ELISA sensitivity and specificity were 95% and 73.3%, when using saline extract; 95% and 82.6% for the D fraction; and 65% and 61.3% for the A fraction, respectively. The immunoblotting assay confirmed the ELISA results, such that the D fraction was more efficient than the other extracts, and the 70-68 kDa component was immunodominant among neurocysticercosis patients.

CONCLUSIONS

These results demonstrated that the D fraction from Taenia saginata metacestodes obtained using TX-114 can be used as a heterologous antigenic fraction in the immunoblotting assay for serologically diagnosing human neurocysticercosis, given its ability to select immunodominant antigens.

Hydrophobic fractions from Strongyloides venezuelensis for use in the human immunodiagnosis of strongyloidiasis

The objective of the present research was to evaluate detergent and aqueous phases of total saline (TS) and alkaline extracts of Strongyloides venezuelensis for human strongyloidiasis immunodiagnosis. Total extracts and detergent and aqueous antigenic fractions were separated using Triton X-114 and were examined by enzyme-linked immunosorbent assay (ELISA) and immunoblotting (IB) tests to detect immunoglobulin G (IgG). Serum samples were obtained from 120 individuals: 40 strongyloidiasis patients (group I), 40 patients with other parasitic diseases (group II), and 40 apparently healthy individuals (group III). Each extract provided a different profile of antigenic components as recognized by IgG in IB. The detergent fraction of the TS extract demonstrated the highest sensitivity and specificity for ELISA and IB. The results indicated that the detergent saline fraction, purified from S. venezuelensis, furnished the most valid results for the strongyloidiasis immunodiagnosis and could be employed as an alternative antigen and as a useful source of specific polypeptides.

Selection of high affinity peptide ligands for detection of circulating antibodies in neurocysticercosis

Neurocysticercosis (NC), caused by Taenia solium, is the most common infection caused by helminthes of the human central nervous system. In this study, a random peptide phage display library was used to isolate peptide ligands as potential markers for neurocysticercosis diagnosis, because occurrence of cross-reactions with other helminthes species in the current used markers. We selected different peptides using IgG purified from pooled sera of neurocysticercosis patients. To investigate the diagnostic potential of recombinant peptides, we have tested different panels of serum samples by Phage-ELISA, and 10 phage clones strongly bound to the anti-T. solium IgGs in NC sera, with an accuracy range from 84.2% to 95%. The phage clones, NC(4)1 and NC(2)8, presented the highest sensitivity and specificity (100%), respectively, and most important, some phage clones did not react with patients' sera from Echinococcus granulosus infected patients. The validation with a competitive ELISA assay demonstrated that the selected phages could mimic T. solium epitopes and bind specifically to the pool of NC sera. Finally, the two recombinant antigens may become potential biomarkers for serodiagnosis of NC, and the Phage-ELISA demonstrated to be a very good assay, being reproducible, simple, fast, and low-cost due to its production through Escherichia coli culture, allowing a high throughput screening of NC.

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.

Immunodiagnosis of human neurocysticercosis using a synthetic peptide selected by phage-display

The usefulness of a synthetic peptide in the serodiagnosis of Taenia solium human neurocysticercosis (NC) has been evaluated. Phage-displayed peptides were screened with human antibodies to scolex protein antigen from cysticercus cellulosae (SPACc). One clone was found to interact specifically with anti-SPACc IgGs. The corresponding synthetic peptide was found to be recognized in ELISA by NC patient's sera. The study was carried out with sera from 28 confirmed NC patients, 13 control sera and 73 sera from patients suffering from other infectious diseases. A 93% sensibility and a 94.3% specificity was achieved. Figures of 89% and 31.4% of sensibility and specificity were obtained in a SPACc-based ELISA. Immunoblotting of SPACc with anti-peptide antibodies revealed a single band of approximately 45 kDa in 1D and four 45 kDa isoforms in 2D-gel electrophoresis. A strong and specific immunostaining in the fibers beneath the suckers, at the base of the rostellum, and in the tissue surrounding the scolex of cysticerci was observed by immunomicroscopy. Our results show that a peptide-based immunodiagnostic of neurocisticercosis can be envisioned.