Saline extract of Taenia saginata metacestodes as an alternative antigen for the immunodiagnosis of neurocysticercosis in human cerebrospinal fluid

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.

Antiparasitic treatment of cerebral cysticercosis: lessons and experiences from China

Cysticercosis is a tropical disease caused by infection with the larval stage of the pork tapeworm, Taenia solium. Humans and pigs acquire cysticercosis by ingesting T. solium eggs shed in the feces of humans with taeniasis (i.e., infected with an adult intestinal tapeworm). Cerebral cysticercosis occurs when the cysts of T. solium develop within the central nervous system, and it is the primary cause of illness in T. solium infection. Currently, cerebral cysticercosis is endemic worldwide, and it is a leading cause of adult-onset epilepsy in developing countries. However, it is now increasingly detected in developed countries due to the immigration of T. solium carriers from the endemic areas. The antiparasitic treatment of cerebral cysticercosis remains controversial till now. In China, except a few cases who conform to the contraindicated criteria of antiparasitic therapy, most cerebral cysticercosis patients with symptoms and signs are given etiological treatment. This paper reviews the antiparasitic therapy of cerebral cysticercosis in China during the past several decades. Praziquantel treatment with different regimens has been used, and various efficacies are achieved. In the early stage, unsatisfactory therapeutic efficacy was achieved due to small doses and short treatment courses. Afterwards, the therapeutic efficacy became increasingly remarkable in both adults and children with the increases in dosage and courses. Albendazole also presents activity against cysticercosis with slow and moderate action, and it has been widely used in the treatment of the infection. The comparison between praziquantel and albendazole treatments showed that the immediate and short-term effects of albendazole treatment were better than those of praziquantel treatment, but similar mid- and long-term efficacies were observed following albendazole and praziquantel treatments. The combination of albendazole and praziquantel treatments can increase the therapeutic efficacy, and now, from the massive clinical practices, most of Chinese clinical specialists propose the combination therapy of albendazole and praziquantel for cerebral cysticercosis with simultaneous administration of steroids, especially in the first course. In addition, administration of praziquantel at a high dose can become a diagnostic treatment for suspected cerebral cysticercosis and serve as a supplement of the currently available diagnostic methods, such as diagnoses based on the clinical features, immunology, CT and MRI imaging, etc., in some atypical cerebral cysticercosis patients. Praziquantel and albendazole treatments have some adverse reactions, and to control these adverse effects, all the cerebral cysticercosis patients should be treated in hospital. According to the type of cerebral cysticercosis, especially for intracranial hypertension type and meningocephalitis type, the dosages of anti-cysticercus drugs need to follow a gradually increasing pattern. During the period of anti-cysticercosis treatments, steroids and/or dehydrating agents need be administered which can alleviate the intracranial hypertension and so on. Traditional Chinese medicines have been also used in the treatment of cerebral cysticercosis and achieve satisfactory outcomes. However, the compound prescription of traditional Chinese medicines is very complex, and the effective components are not fully clear. Some cerebral cysticercosis patients with very high intracranial tension could not receive antiparasitic treatment immediately, and surgical treatment is required. Chinese surgeons also achieve some successful experiences, but not all the cysticercus can be removed completely during the surgery. Therefore, antiparasitic drugs are still needed after the operation. The rehabilitative treatment is supplementary in the therapy of cerebral cysticercosis. In China, the rehabilitative treatment of cerebral cysticercosis is still at the initial stage. These lessons and experiences in China can be shared with medical staff and researchers from other countries where the disease is endemic.

Taenia saginata metacestode antigenic fractions obtained by ion-exchange chromatography: potential source of immunodominant markers applicable in the immunodiagnosis of human neurocysticercosis

The aim of this study was to fractionate and partially characterize fractions obtained from the total saline extract (SE) of Taenia saginata metacestodes after ion-exchange procedure in carboxymethyl sepharose (CM) and diethylaminoethyl sepharose (DEAE) resins, as a source of antigenic markers applicable in the immunodiagnosis of neurocysticercosis (NCC). For IgG detection by enzyme-linked immunosorbent assay (ELISA) and immunoblotting, 140 serum samples were analyzed: 45 from patients with NCC (G1), 50 from patients with other parasitic infections (G2), and 45 from healthy individuals. Sensitivity (Se), specificity (Sp), area under curve (AUC), and likelihood ratios (LR) were calculated. CM S2 and DEAE S2 fractions provided high diagnostic values (Se 88.8% and 93.4%; Sp 93.7% and 92.6%; AUC 0.965 and 0.987; LR+ 14.07 and 12.67; LR- 0.11 and 0.07, respectively). In conclusion, CM S2 and DEAE S2 fractions are important sources of specific peptides, with high efficiency to diagnose NCC.

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.

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.

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.