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Conformational study of Taenia solium metacestode proteins diagnostic for neurocysticercosis: is there a role for unfolding to imrove antigencity?

T. solium cyst infections of the brain (neurocysticercosis) are predominantly solitary cyst infections in India. This poses difficulties for serological diagnostic assays that detect antibodies, as the levels are apparently too low for detection in many of these patients. Antibody detection immunoblot assays for solitary cysticercus granulomas are specific but only 60% sensitive. These tests use a fraction of lentil lectin specific T. solium cyst glycoproteins that contain 7 infection specific proteins of molecular weights 50, 38, 24, 21, 18, 14, 13 kDa, in different concentrations, as antigen. The study was undertaken to determine if altering the structure of T. solium proteins diagnostic for neurocysticercosis will improve their antigenicity and thereby their detecti on of cysticercal antibodies in neurocysticercosis patients.

It is known that conformational alterations of proteins result in increasing the numbers of exosed epitopes and this was attempted with the cyst antigens. Six of the T. solium infection specific glycoproteins of molecular weights 50, 38,24, 18,14, 13kDa were purified to homogenicity by lentil lectin chromatography and preparative SDS-PAGE. These proteins required extensive N-glycosylation and disulfide bonds to maintain their antigencity. Use of urea (5M) induced tertiary conformations of these proteins improved sero-detection on immune blots of cysticercus antibodies among patients with solitary cyst infections to 71% from 62% using antigens not treated with urea.

Providing a cocktail of these antigens in equal concentrations (50-150ng/ml) improved serological antibody detection for solitary cyst infections to 88% but decreased the detection of multi-cyst infections. This paradox requires further study. The sensitivity of antibody detection was 83% for patients with solitary cysticercus granulomas in dot blot assay using each pure antigen at equivalent concentrations of fucose (0.25 pmoles). This study showed that serological diagnostic assays for patients with solitary cysticercus granulomas improved by using unfolded cyst antigens, cocktails of antigens in defined protein concentrations and antigens equivalent in fucose.

Publication

Prabhakarana, V., Rajshekhar, V., Murrell, K.D. and Oommen, A. Conformation sensitive immunoassays improve the serodiagnosis of solitary cysticercus granuloma in Indian patients. Trans R Soc Trop Med Hyg 101: 570,2007

Dr. Anna Oommen

Neurochemistry Laboratory

Department of Neurological Sciences

Christian Medical College, Vellore

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Title Annotation:ABSTRACTS: Some Research Projects Completed Recently
Author:Oommen, Anna
Publication:ICMR Bulletin
Article Type:Abstract
Geographic Code:9INDI
Date:Feb 1, 2010
Words:357
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