A new immunologic test for CNS cysticercosis

Immunological and molecular diagnosis of cysticercosis

Cysticercosis, the infection with the larval stage of Taenia solium, is a cause of neurological symptoms including seizures, affecting the quality of life of patients and their families. Diagnosis focuses on brain imaging and serological tests are mostly used as confirmatory tools. Most cases, however, occur in poor endemic areas, where both kinds of diagnostic tools are poorly available. Development of point of care diagnostic tests is one of the most important priorities for cysticercosis researches today. The ideal point of care test would require detection of viable cysticercosis and hopefully identify cases with severe or progressive forms of neurocysticercosis, leading to referral of the patient for specialized medical attention. This manuscript describes the evolution of the serological diagnosis of cysticercosis over time, and the characteristics of the most common currently available tools, their advantages and disadvantages, and their potential use in future diagnostic tests.

Neurocysticercosis immunodiagnosis using Taenia solium cysticerci crude soluble extract, excretory secretory and lower molecular mass antigens in serum and urine samples of Indian children

Neurocysticercosis (NCC), the most common neurological disorder of parasite etiology, results from lodgement of Taenia solium cysticerci in the central nervous system and is now increasingly being recognized in children. The confirmed diagnosis is based collectively on radiological findings and serodiagnostic techniques. The serodiagnostic techniques have variable sensitivity and specificity depending upon the technique, antigens used, location and number of cysts. Crude soluble extract (CSE), excretory secretory (ES) and lower molecular mass (LMM) (10-30 kDa) antigenic fraction of T. solium cysticerci were evaluated for antibody detection in serum and urine samples by ELISA. Serum and urine samples were collected each from 125 clinically suspected and radiologically proven NCC (111 with single Computed Tomography (CT) lesions and 14 with multiple CT lesions) and 125 control subjects (60 with neurological disorders other than NCC, 40 with other parasitic diseases and 25 apparently healthy subjects). The sensitivity of the ELISA with the use of CSE, ES and LMM antigenic fractions was 38.4%, 63.2% and 30.4% with serum (cut off dilution 400), 46.4%, 44% and 47.2% with neat urine and the specificity was 88%, 76.8% and 85.6% with serum (cut off dilution 400), 66.4%, 65.2% and 58.4% with neat urine samples, respectively. The study suggests that detection of antibody to ES antigen in serum samples may serve useful purpose for the serodiagnosis of human NCC.

Neurocysticercosis: a review

BACKGROUND

In North America, the largest number of neurosurgical cases stemming from parasitic infections involves the larval form of Taenia solium, the infectious organism causing neurocysticercosis. This infection of the central nervous system (CNS) is most commonly seen in areas with significant immigrant populations and can often present particular challenges to treating physicians.

METHODS

A review of the literature was performed, highlighting the epidemiology, parasitology, and clinical manifestations of neurocysticercosis. Particular attention was paid to 4 locations of neurocysticercosis lesions: parenchymal, subarachnoid/cisternal, intraventricular, and spinal.

RESULTS

Both medical and surgical interventions may be necessary for adequate treatment of neurocysticercosis, depending on various factors, including location of lesion.

CONCLUSIONS

A review of neurocysticercosis, with particular attention paid to location of disease involvement in the CNS, provides important information to the clinical management of this disease.

Dot-ELISA for the diagnosis of neurocysticercosis

The aim of the present study was to standardize and evaluate dot-Enzyme linked immunosorbent assay (Dot-ELISA), a simple and rapid test for the detection of cysticercus antibodies in the serum for the diagnosis of neurocysticercosis (NCC). The antigen used in the study was a complete homogenate of Cysticercus cellulosae cysts obtained from infected pigs and dotted on to nitrocellulose membrane. Test sera were collected from the patients of NCC, and control sera from patients with other diseases and healthy students and blood donors of the Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER) Hospital, Pondicherry, during a study period from 2001 to 2003. Dot-ELISA detected antibodies in 14 of 25 (56%) in clinically suspected cases of NCC, 13 of 23 (56.5%) in CT/MRI proven cases of NCC and 2 of 25 (8%) each in non-cysticercal CNS infection controls and healthy controls. The test showed a sensitivity of 56.25%, specificity of 92%, positive predictive value of 87.09%, and negative predictive value of 70.76%. Results of the present study shows that the Dot-ELISA as a simple test can be used in the field or poorly equipped laboratories for diagnosis of NCC .

Immunodiagnostic tools for human and porcine cysticercosis

The development of improved immunodiagnostic tools has contributed to our knowledge on the importance of taeniosis/cysticercosis by enabling sero-epidemiological surveys and community-based studies to be carried out. Immunodiagnostic techniques include detection methods for specific antibodies and for circulating parasite antigen in serum or cerebrospinal fluid. The antigens used in immunoblot and enzyme-linked immunosorbent assay (ELISA) for antibody detection have evolved from crude extracts to highly purified specific fractions and recombinant antigens of the glycoprotein family, increasing both the sensitivity and the specificity of the tests. The application of ELISA for the detection of circulating parasite antigens may present some diagnostic advantages since it demonstrates not only exposure but also active infections. Until now only a few of the current techniques have been standardised and fully validated, making comparisons between studies difficult. The lack of a gold standard is a serious drawback. In surveys on cysticercosis, antibody detection systems have been useful in identifying the risk factors associated with transmission of Taenia solium; a high seroprevalence in a community indicates a "hot spot" where preventive and control measures should be applied. In contrast, the potential use of immunodiagnostic tools to identify cases of neurocysticercosis (NCC) in man is subject to debate. The correlation between a positive serology and neurological symptoms and/or lesions indicative for NCC on neuro-imaging techniques is poor to fair in most studies. This may be explained by the unpredictable clinical outcome of the infection and the variable immunological response of the human host to infection. A major problem is that in many developing countries, neuro-imaging methods are inaccessible and/or too expensive for the rural population at risk. Under these conditions, serology may provide the only tool for diagnosis of the infection.

Taenia solium cysticercosis

Cysticercosis, the infection of the larval tissue stage of the pork tapeworm, Taenia solium, is endemic to most developing countries and increasingly is seen in industrialized countries because of immigration. Human infection is a major cause of acquired epilepsy, and porcine infection causes important economic losses to farm workers. Clinical manifestations vary because of the variable number, size, and location of the cysts and the immune response of the host. Diagnosis is based on imaging techniques (CT and MR imaging) and serology (immunoblot). Current research efforts are centered on control and eradication of the taeniasis cysticercosis complex in endemic areas.

Acute cysticercal meningitis in children: response to praziquantel

Acute purulent meningitis as a manifestation of cerebral cysticercosis is uncommon. We report two children aged 12 months and 3 years who presented with clinical signs of acute meningitis and whose initial cerebrospinal fluid (CSF), except for negative culture, was typical of purulent meningitis. However, eosinophils were present in subsequent examinations of the CSF and the haemagglutination titre for cysticercus rose. Praziquantel was given to both children with dramatic improvement in clinical and CSF findings.

Childhood neurocysticercosis--epidemiology, diagnosis and course

Neurocysticercosis was diagnosed in 0.89% of children enrolled in our Child Neurology Clinic in the years 1979 to 1990. The commonest presenting symptom was seizures (90%) followed by raised intracranial pressure (44%). CT scans revealed a variety of lesions including low and high attenuation cysts, periventricular edema, hydrocephalus and calcification. ELISA was useful in substantiating the diagnosis in almost 70% of cases. Only 18 patients who had active disease merited treatment with praziquantel. The clinical and CT response was good. Follow-up revealed spontaneous quiescence in many patients with inactive disease.

Neurocysticercosis: a short review and presentation of a Scandinavian case

Cysticercosis is a disease entity caused by the larval form (Cysticercus cellulosae) of the pork tapeworm (Taenia solium). When man becomes the intermediate host, cysticercal cysts can develop in various organs. Neurocysticercosis, i.e. cysticercosis of the central nervous system, can lead to a broad range of neurological disturbances. The disease is usually confined to geographical regions where sanitation is poor but can occur among immigrants or travellers from such regions. Due to increased travel and immigration the disease may appear in non-endemic areas. We describe a recent case of neurocysticercosis in a 28-year-old Danish woman, who had been travelling in the Far East. She was successfully treated with praziquantel. A short review of the literature is given as the knowledge of the diagnosis and treatment of the disease has increased greatly in the last decade.

[Immunohistochemical observation on the antigens inducing IgG and IgM antibodies against sparganum]

Localization and characterization of the antigenic components of sparganum which induced IgG and IgM antibodies in the host were studied by immunohistochemical techniques and SDS-PAGE and Western blotting. The antigen recognized by IgG antibody of rats or mice which were immunized by infection or injection of crude extracts of metacestodes of Spirometra erinacei, was located in the parenchyma of sparganum, especially at the cortex and around the calcareous corpuscles. The immunoreaction was demonstrated not only in the encysted fibrous wall of host but around the arterioles or venules in the connective tissue of host. The antigen recognized by IgM antibody of rats or mice was also observed in the parenchyma of sparganum and in the connective tissue of host. By 5-20% gradient SDS-PAGE and EIBT, we detected antigenic components by IgG and IgM antibodies of the rat or mouse immunized by infection or injection of crude extract of spargana. Twenty-three antigenic bands from crude extracts of spargana were recognized by IgG antibody and 15 components by IgM antibody of immunized rats. Out of the bands recognized by IgG and IgM antibodies, 15 were cross-reacted each other. Twenty components of excretory-secretory proteins from spargana were recognized by IgG, and 5 components by IgM antibody of immunized rats. By IgG and IgM antibodies of immunized mice, 16 components of crude extracts were recognized by IgG antibody and 9 components by IgM antibody. Twenty components of excretory-secretory preparation were recognized by IgG antibody and 5 components by IgM antibody. Thirteen components of crude extracts were cross-reacted by IgG antibody of rats and mice.

Cerebral cysticercosis as a common cause of epilepsy in Gurkhas in Hong Kong

A prospective study of Nepalese adults (Gurkhas) based in Hong Kong who presented with adult-onset epileptiform seizures determined that cerebral cysticercosis was causative in 7 out of 8 cases. The relative roles of specific cysticercal serology and computerised axial tomography in diagnosis are discussed. Serum IgE levels were found to be raised in all patients with cerebral cysticercosis in the absence of other parasitic infection and reverted to normal after the patients were treated with praziquantel. Evidence suggests that the Gurkhas acquired their cysticercal infections in Nepal.

Imunological characterization of antigens from cysticercus and sparganum and their application to immunodiagnosis 1. Immunological characteristics of crude antigenic components from Cysticercus cellulosae

We studied the serological reaction between various antigenic components from Cysticercus cellulosae and IgG antibodies in sera of cysticercosis, sparganosis, hydatidosis patients and normal humans by ELISA and EITB. In serological tests by ELISA, we recognized cross reaction of Cysticercus antigenic components with IgG antibodies in heterologous sera such as sparganosis and hydatidosis patients or normal humans. The crude antigenic components of Cysticercus showed lower ELISA sensitivity in homologous sera from cysticercosis patients than heterologous sera from hydatidosis patients. A total of 31 polypeptide bands with 260 KDa-22 KDa molecular weights were detected by SDS-PAGE, and 11 of them showed strong intensity. Total 22 components of them were recognized by IgG antibodies in cysticercosis patients sera. However, 12 of them were recognized also by normal human sera, 11 were by sparganosis sera, and 21 were by hydatidosis patients sera. The crude antigenic components of 104 KDa, 82 KDa, 72 KDa, 59 KDa and 34 KDa molecular weights were nonspecific ones, which cross-reacted with sera of either cysticercosis, sparganosis, hydatidosis patients or normal humans.

Intracranial synthesis of specific IgG antibody in cerebrospinal fluid of neurocysticercosis patients

To determine the source of Cysticercus-specific IgG antibody in cerebro-spinal fluid(CSF), paired samples of serum and CSF were collected from confirmed neurocysticercosis, other neurologic diseases and normal control. The antibody levels in serum and CSF were measured by enzyme-linked immunosorbent assay (ELISA). With the measurement of total protein, albumin and IgG concentration in serum and CSF, the contribution of IgG in CSF were calculated in transudation, exudation and intracranial synthesis using the formula of Tourtellotte and Ma (1978). Mean concentrations of total protein, albumin, IgG and proportional IgG levels in CSF by transudation, exudation and intracranial synthesis were elevated in neurocysticercosis. But only the intracranial synthesis of IgG showed a statistically significant correlation with the specific IgG antibody levels in CSF. In CSF from lateral ventricle in the 4th ventricular neurocysticercosis, the protein concentrations were normal and the specific antibody levels were negative. However, in consecutively secured lumbar CSF from the same patients, the former were increased and the latter were positive. These results indicated that, in neurocysticercosis, the specific IgG antibody in CSF was a local product of intracranial synthesis.

[A cerebrospinal fluid syndrome in neurocysticercosis]

The study is based on 371 cerebrospinal fluid (CSF) samples and 324 serum samples from 40 patients with neurocysticercosis (NC) submitted to treatment with praziquantel. The aim of the study is a critical evaluation on humoral immunity in CSF NC syndrome. The analysis of NC patients at diagnosis and in the follow-up period was performed considering three connected criteria: the clinical one, the CSF examination and the computed tomography. For the study of CSF and serum samples a systematization of collection was scheduled in relation to: diagnosis; period of treatment; follow-up. A total of 13 samples for each case for a follow-up period of two years was scheduled. For the study of humoral immunity a semiquantitative methodology was employed to verify the intra blood-brain barrier (BBB) gamma globulins synthesis. It was based upon electrophoretic profile data on CSF and serum proteins, and relations and indexes. Normal values were previously characterized in a normal control group. This group was formed by 50 patients with chronic headache who presented normal neurological examination, as well as, CSF-examination and serum proteinogram under the safety limits of normality. To verify intra BBB gamma globulins synthesis it was considered the gamma globulin content of the CSF and serum, the gamma globulins/prealbumin + albumin relationship, the Link and Tibbling index, the intra BBB gamma globulins synthesis of Tourtellotte and col., and the appearance of oligoclonal bands in the CSF. Confirmation of the disease was performed by immunological reactions for cysticercosis: complement fixation test in CSF and serum; immunofluorescent test and enzyme-linked immunosorbent assay (ELISA) in CSF. Interference factors in the CSF NC syndrome were analysed at first such as those related to: clinical aspects, time of disease, previous dependence on corticotherapy, ventricular derivation shunts, tomographic findings. It was shown that all of them produce several degrees of interference in the intensity of the CSF NC syndrome. Data on intra BBB gamma globulins synthesis were verified in 37 patients (92.5%). It occurred in a persistent pattern in 18 cases (45%) during all the study phases, and not showed changes that might be related to treatment. On the other hand, it was shown that analysis of the results must always be performed case by case due to large dispersion of events observed and the differences of behavior of data related to humoral immunity, when critically analysed during diagnosis, treatment period and in the follow-up.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization by enzyme-linked immunosorbent assay of the humoral immune response in patients with neurocysticercosis and its application in immunodiagnosis

The enzyme-linked immunosorbent assay was standardized for the search for specific antibodies in human neurocysticercosis. A crude cysticercal extract and two partially purified antigenic fractions were used, as well as serum and cerebrospinal fluid (CSF) samples of different groups of subjects. Immunoglobulin G (IgG) antibodies were detected in serum and CSF, with a sensitivity of 85 and 90%, respectively. Specificity was 96% with a partially purified antigen and 100% with the crude cysticercal extract. IgM and IgA antibodies were detected less frequently, and IgE was detected only occasionally, both in serum and CSF. Analysis of serum and CSF samples drawn from the same patient did not always reveal the presence of anticysticercus antibodies in both samples. A significant correlation was found between the presence or absence of IgG antibodies in the CSF and the morphological appearance of the parasite (undamaged or calcified). Variations in the humoral response were not found to correlate with clinical and laboratory findings.

Anticysticercous antibodies in serum and cerebrospinal fluid in patients with cerebral cysticercosis

Fifty-one cases of cerebral cysticercosis proved by surgery or CT scanning were studied prospectively with the ELISA test in order to detect anticysticercous antibodies in blood and CSF. The ELISA test was also performed for detection of antibodies in 20 control patients who had CSF withdrawn during a myelogram and in 119 serum samples of asymptomatic subjects. We found an overall sensitivity of the ELISA test in the blood of 87% with a specificity of 90%. In the CSF we found a sensitivity of 87% with a specificity of 100%. However, when we compared patients with cerebral cysticercosis of a benign type with patients with cerebral cysticercosis of a malignant type we found a serum sensitivity of 75% for the benign group as compared to 93% of the malignant group. The CSF sensitivity was 80% in the benign group and 93% in the malignant group. This difference was statistically significant.

Evaluation of enzyme-linked immunosorbent assay in serological diagnosis of human neurocysticercosis using paired samples of serum and cerebrospinal fluid

The applicability of micro-ELISA was evaluatd in human neuro-cysticercosis using paired samples of serum and CSF. A total of 355 cases who were mostly neurologic patients was subjected. Cystic fluid of C. cellulosae was used as antigen in protein concentration of 2.5 micro-g/ml. Serum was diluted to 1:100 and CSF was undiluted in the assay for the specific IgG antibody level. The differential criterion of the positive reaction was the abs. of 0.18 in both samples. The results were summarized as follows: The overall sensitivity of the micro-ELISA in 71 confirmed neurocysticercosis was 90.1%; the sensitivity by serum was 77.5% and that by CSF was 83.1%. CSF was a more sensitive and valuable material. Most of the false negative cases of neuro-cysticercosis showed far lower level of abs. rather than marginal. The overall specificity of the micro-ELISA in 52 confirmed other neurologic diseases was 88.5%; the specificities by serum and by CSF were 94.2% respectively. Cases of other neurologic diseases did not show false positive reactions in both samples. When serum was assayed, taeniasis(2/18), sparganosis(2/20), paragonimiasis(1/56), clonorchiasis(1/15) and fascioliasis(1/1) cases showed cross reactions. When CSF was assayed, 2 of 10 neuro-sparganosis showed cross reactions while none of 9 neuro-paragonimiasis showed it. Out of 71 confirmed neuro-cysticercosis cases, 6 and 11 showed cross reactions by serum and CSF to crude extract antigen of sparganum; but no case did show it to crude extract antigen of Paragonimus westermani. Ventricular CSF showed low or negative levels of IgG antibody than lumbar CSF unless the lesion was at the lateral ventricle itself. Out of 4 racemose cysticercosis cases, 3 showed positive reaction in serum while all of 3 examined CSF were positive. The above results indicated that the serological test for detecting the specific IgG antibody by micro-ELISA using paired samples of serum and CSF was very helpful for clinical differentiation of neuro-cysticercosis from neurologic diseases of other causes.

Serologic and intradermal tests for parasitic infections

For years, the diagnosis of most parasitic diseases has depended upon the direct demonstration of the parasite or its cysts, eggs, or larvae in specimens. In some infections, direct demonstration of the causative agent or its stages is almost impossible. In such cases, indirect techniques, such as serologic methods, have been found to be more practical and sensitive than are direct methods. Most serologic methods have been devised to detect antibodies. Tests for the detection of antigen are just beginning to be utilized; however, the practicality and under what situations antigen detection tests can be used await further testing. The majority of the serum antibody tests employ a heterogeneous mixture of antigens. Antigens derived from whole adult or larval stages usually result in tests with poor specificity and/or sensitivity. The necessity for better purified and standardized antigens cannot be over emphasized. Although there have been many major advances in the serodiagnosis of parasitic infections, a major drawback to routine use of parasitic serologies is the lack of commercially available reliable test kits. For the diagnosis of most parasitic diseases, one must rely upon specialty laboratories or public health laboratories. Before any laboratory begins to offer parasitic test serologies, they should contact their local or state public health laboratory or the Parasitic Serologic Section of the Centers for Disease Control to determine the pros and cons of these tests. Information of this type should be used to inform the physician of the limitations of the test in the differential diagnosis.

Enzyme-linked immunosorbent assay for the diagnosis of cerebral cysticercosis

Central nervous system cysticercosis is common in countries where Taenia solium occurs in pigs and the level of hygiene and sanitation is low. The clinical presentation may include epileptic seizures, focal neurological deficits, hydrocephalus, or aseptic meningitis. The disease is frequently seen in California residents of Hispanic origin. It sometimes occurs in whites from homes that employ Hispanic cooks. Diagnosis is often difficult. Computerized tomography scan and brain biopsy are the most reliable diagnostic procedures, but each has its limitations. We have found that a radioimmunoassay improves our diagnostic capability, and more recently we have adapted this to an enzyme-linked immunosorbent assay that is equally sensitive and specific and, in addition, obviates the need for radioactive materials. Details of the enzyme-linked immunosorbent assay procedure and its application to the diagnosis of central nervous system cysticercosis form the basis of this report.