Chromatography of a saline extract of Taenia saginata.
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Biomedical subjects
Publications and source records attributed to L J Harrison.
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Current diagnosis of neurocysticercosis relies mostly on computerized tomography and nuclear magnetic resonance, with detection of antibodies being confirmatory rather than decisive. An assay which detects parasite products in cerebrospinal fluid would conclusively demonstrate a current infection and could be important when decisions regarding treatment must be made. Cerebrospinal fluid from patients with neurocysticercosis was used in 4 enzyme immunoassay capture tests designed to detect parasite products. Of the systems tested, one, based on the use of a monoclonal antibody reactive with a surface and secretion component of the metacestode, was particularly promising, giving a sensitivity of 72%. The assay has the double advantage of a very low background and a proved specificity for the products of living cysticerci. The other 3 systems (monoclonal anti-vesicular fluid antibody, polyclonal antibody against a saline extract and polyclonal anti-antigen B antibody) were less sensitive. Results with the anti-antigen B system support the proposal that products of low immunogenicity are the most appropriate targets for the serological detection of the parasite.
The efficacy of albendazole (ABZ) treatment for human neurocysticercosis (NCC) was assessed by using a monoclonal antibody-based parasite antigen detection ELISA which specifically detects the products of living cysticerci in human serum. The assay displayed 85% diagnostic sensitivity, detecting 39 of 46 NCC cases. Only patients with a single viable cyst or only enhancing lesions (degenerating parasites) were seronegative. Specificity of the assay was 92% (23/25) when tested in healthy Peruvian volunteers. In 'cured' patients, in whom all parasites died after ABZ therapy, parasite antigen levels fell sharply by 3 months post treatment. This pattern was not observed in patients refractory to treatment. The sensitivity of the assay with serum samples, and its ability to identify successfully treated patients, make this monoclonal antibody-based ELISA the test of choice for the follow-up of NCC cases.
An enzyme-linked immunosorbent assay (ELISA) for the detection of antigen secreted by viable Taenia solium metacestodes (Ag-ELISA) was applied to 43 pre-treatment and 47 follow-up cerebrospinal fluid (CSF) samples from Peruvian patients with neurocysticercosis demonstrated by computed tomography and enzyme-linked immunoelectrotransfer blot assay. The sensitivity of the assay was 86%. Negative pre-treatment results in the Ag-ELISA test were restricted to patients with only a single live cyst or only enhancing lesions. Patients with hydrocephalus had higher levels of circulating antigen. There was no difference between antigen levels in CSF taken before and immediately after treatment (day 14). Levels of parasite antigen were significantly positively correlated with the number of live cysts detected by tomography and were also proportional to the number and intensity of antibody reactions recognized by the immunoblot diagnostic test. In contrast, there was a negative correlation with the number of enhancing lesions revealed by tomography, supporting the hypothesis that enhancing lesions correspond to a terminal, moribund stage of the parasite. The use of antigen-detection tests specific for viable metacestodes has immediate utility in the clinical context, not only providing important information on the viability of the parasites but also leading to an improved understanding of the pathogenesis of neurocysticercosis before and after drug treatment.