Evaluation of lower molecular mass (20-24 kDa) Taenia solium cysticercus antigen fraction by ELISA and dot blot for the serodiagnosis of neurocysticercosis in children

Recurrent syncopal episodes in a pregnant patient with neurocysticercosis

Neurocysticercosis (NCC) is the most common parasitic infection of the nervous system and acquired epilepsy in low-resource settings due to the pork tapeworm, Taenia solium. Humans contract the intestinal infection of the adult tapeworm (taeniasis) through the fecal-oral route after consuming undercooked food, particularly pork or water, contaminated with tapeworm eggs. When the larvae invades the central nervous system (CNS), the infection causes NCC, which often manifests as late-onset seizures, chronic headaches, and intracranial hypertension. We describe a 31-year-old Hispanic multigravida woman from Guatemala, at 33 weeks of gestation, who presented with multiple syncopal and hypotensive episodes prompting a Computed tomography (CT) image of the head revealing multiple small cerebral calcifications indicating NCC. In this article, we highlight the significance of early symptom recognition and diagnostic workup for NCC in areas with diverse immigrant populations. We also discuss the epidemiology, clinical manifestations, and current treatment modalities available for NCC.

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 K_m (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.

Pediatric neurocysticercosis: current challenges and future prospects

Neurocysticercosis (NCC) is an acquired infection of the nervous system caused by encysted larvae of Taenia solium. It is a major cause of epilepsy in the tropics and the commonest cause of focal seizures in North Indian children. T. solium teniasis-cysticercosis is considered a parasitic "Neglected Tropical Diseases" endemic throughout Southeast Asia. NCC in children has pleomorphic manifestations depending on the location, number and viability of the cysts, and host response. Even with advancing knowledge of the disease manifestations, many aspects related to diagnosis and treatment, particularly in children, still remain controversial and pose challenges to clinical practice. There is no gold standard test to diagnose NCC and the management recommendations are still emerging. This review provides an overview of diagnosis of NCC in children and its management with special focus on current challenges and future prospects.

Cysticercus cellulosae antigens in the serodiagnosis of neurocysticercosis

Neurocysticercosis (NCC) is difficult to diagnose clinically because of its varied clinical presentation. However, an accurate diagnosis is possible only after suspicion on epidemiological grounds, proper interpretation of the clinical data, analysis of the findings on imaging studies, and specific immunological tests on the serum and cerebrospinal fluid (CSF). The diagnosis of NCC by any single parameter thus continues to remain difficult. In the past, detection of NCC was based on autopsy studies and histological confirmation. In recent times, the advent of imaging methods such as computed tomography and magnetic resonance imaging have provided excellent non-invasive tools for easy detection of NCC. Nevertheless, an imaging technique of the brain, although useful, is not considered as a gold standard for the diagnosis of NCC. Serological tests are being increasingly used in adjunct with imaging techniques, to aid the diagnosis of NCC. Immunodiagnostic techniques include detection methods for specific antibodies and for circulating parasite antigens in the serum and CSF. Currently, many of the immunodiagnostic tests, including the enzyme-linked immunosorbent assay and enzyme immunotransfer blot, use purified native antigens for the immunodiagnosis of NCC. Nevertheless, the main problem with the use of native cysticercal antigens is that the native proteins often show cross reactions with sera from humans infected with other parasites. The preparation of native antigens also demand a constant supply of parasitic material from the intermediate host pig. In order to overcome the problems in using native antigens, the recombinant antigens or synthetic peptides, which can be produced under stable conditions, are being evaluated for the serodiagnosis of NCC.

Evaluation of an immunodot blot technique for the detection of antibodies against Taenia solium larval antigens

Immunodiagnostic tests represent an important tool for diagnosis of cysticercosis, the disease caused by cysticerci of Taenia solium. Accurate diagnosis of neurocysticercosis (NCC) requires costly neuroimaging techniques (magnetic resonance imaging and computed tomography), which are seldom affordable for people in endemic countries. Hence, new low-cost diagnostic methods offering good sensitivity and specificity are needed. Here, we studied four immunodiagnostic tests immunodot blot Tsol-p27, a commercial ELISA, and Western blot Tsol-p27/TsolHSP36, and compared them with a commercial enzyme-linked immunoelectrotransfer blot (EITB) that we regarded as the gold standard method. The analyzed serum samples were obtained from 160 patients: 94 epileptics suspected of NCC, six individuals confirmed NCC-positive, and 60 with positive (30) or negative (30) serology for Chagas diseases. Of the 100 serum samples from epileptic patients, 13 were positive and 87 negative by EITB. Compared to Western blot Tsol-p27, immunodot blot Tsol-p27 offered similar specificity (97.8% vs. 95.6%) but better sensitivity (86.7% vs. 76.4%). The ELISA was similar to the immunodot blot Tsol-p27 regarding both sensitivity and specificity. Western blot TsolHSP36 provided the lowest sensitivity (61.9%) and specificity (86.1%). None of the antibodies in the serum samples from the Chagas control groups were recognized by immunodot blot Tsol-p27. Our results indicate that the immunodot blot Tsol-p27 provides good sensitivity and specificity. Furthermore, considering the simplicity and low cost of this test, it might be preferable as a diagnostic method in poorly equipped laboratories in endemic countries.

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.

A dot-ELISA using a partially purified cathepsin-L-like protein fraction from Taenia solium cysticerci, for the diagnosis of human neurocysticercosis

Human neurocysticercosis (NCC), caused by the cestode Taenia solium, is responsible for a significant amount of neurological morbidity and epilepsy in developing countries. The disease remains highly endemic in many areas, despite several efforts and interventions to control it. A simple, cheap and fast diagnostic assay that is suitable for use in field conditions is highly desired. In immunodiagnostics based on western immunoblots or standard ELISA, a cathepsin-L-like protein purified from the cysticercus fluid has previously performed well as an antigen. In a recent study in Peru, the same 53/25-kDa antigen was therefore used in the development of a dot-ELISA that could be employed for mass screenings under field conditions. The assay was standardized and tested not only against sera from a large group of NCC cases but also against sera from patients with other common parasitic infections, so that sensitivity and specificity could be assessed. For NCC, the assay gave better sensitivity in the detection of individuals with extraparenchymal cysts (94·4%-100%) or multiple parenchymal cysts (74·6%-80·0%) than in the detection of individuals with single parenchymal cysts (29·4%-45·1%). The assay also showed a high specificity for NCC (99·0%-100%), with a very low level of cross-reactivity with other parasitic infections. The dot-ELISA developed in this study is a highly specific, simple, cheap and rapid test for NCC that could be used under field conditions, even in the low-resource settings that are common in developing countries.

Neurocysticercosis: relationship between Taenia antigen levels in CSF and MRI

OBJECTIVE

To determine the relationship between Taenia antigen (TA) detection in cerebrospinal fluid (CSF) and magnetic resonance imaging (MRI) findings in patients with definite diagnosis of neurocysticercosis (NC).

METHOD

Sixty-three patients with definite diagnosis of NC were submitted to a MRI of the brain, and to a CSF examination, with a meticulous search for TA by ELISA.

RESULTS

TA detection was positive in 36 patients (57.1%). A total of 836 lesions were analyzed, greatly within the cerebral parenchyma (98.7 of the lesions). Intact or non-degenerating cysts were the most common evolutive phase observed (50.4% of all lesions), 22.1% were degenerating cysts and 19.5% calcified cysts. We observed a significant relationship between TA levels detected and the total number of lesions and the number of non-degenerating cysts, but not with calcified lesions.

CONCLUSION

According to our results, we propose at least four important types of contribution: (1) TA detection may allow etiologic diagnosis in transitional phases of NC, with non-characteristic images; (2) in final stages of evolution of cysticercoids in the CNS, lesions may not appear on CT or MRI, and TA detection may contribute to a definite etiologic diagnosis; (3) TA detection may permit diagnosis of NC in some patients with previous negative tests for antibody detection in CSF; (4) TA detection may represent an accurate marker of disease activity in the epileptic form of NC.

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.

Update on eosinophilic meningoencephalitis and its clinical relevance

Eosinophilic meningoencephalitis is caused by a variety of helminthic infections. These worm-specific infections are named after the causative worm genera, the most common being angiostrongyliasis, gnathostomiasis, toxocariasis, cysticercosis, schistosomiasis, baylisascariasis, and paragonimiasis. Worm parasites enter an organism through ingestion of contaminated water or an intermediate host and can eventually affect the central nervous system (CNS). These infections are potentially serious events leading to sequelae or death, and diagnosis depends on currently limited molecular methods. Identification of parasites in fluids and tissues is rarely possible, while images and clinical examinations do not lead to a definitive diagnosis. Treatment usually requires the concomitant administration of corticoids and anthelminthic drugs, yet new compounds and their extensive and detailed clinical evaluation are much needed. Eosinophilia in fluids may be detected in other infectious and noninfectious conditions, such as neoplastic disease, drug use, and prosthesis reactions. Thus, distinctive identification of eosinophils in fluids is a necessary component in the etiologic diagnosis of CNS infections.

Neurocysticercosis in children

Neurocysticercosis (NCC) is a common cause of seizures and neurologic disease. Although there may be variable presentations depending on the stage and location of cysts in the nervous system, most children (> 80%) present with seizures particularly partial seizures. About a third of cases have headache and vomiting. Diagnosis is made by either CT or MRI. Single enhancing lesions are the commonest visualization of a scolex confirms the diagnosis. Some cases have multiple cysts with a characteristic starry-sky appearance. Management involves use of anticonvulsants for seizures and steroids for cerebral edema. The use of cysticidal therapy continues to be debated. Controlled studies have shown that cysticidal therapy helps in increased and faster resolution of CT lesions. Improvement in long-term seizure control has not yet been proven. Children with single lesions have a good outcome and seizure recurrence rate is low. Children with multiple lesions have recurrent seizures. Extraparenchymal NCC has a guarded prognosis but it is rare in children. In endemic areas NCC must be considered in the differential diagnosis of seizures and various other neurological disorders.