Time-resolved immunofluorometric assay (TR-IFMA) for the detection of the schistosome circulating anodic antigen.
We report the development of a time-resolved immunofluorometric assay (TR-IFMA) for the quantitative determination of the schistosome circulating anodic antigen (CAA). A mouse monoclonal antibody (line 120-1B10-A), recognizing a repetitive epitope on CAA, was used as both antigen-capture antibody and as Europium-labelled antigen-detecting antibody. The lower detection limit of the assay was 20 pg of trichloroacetic acid soluble fraction of adult worm antigen (AWA-TCA) per ml, with a nearly linear measuring range from 20 pg to 130 ng AWA-TCA per ml. The TR-IFMA was compared with an enzyme-linked immunosorbent assay (ELISA), in which the same monoclonal antibody was used as antigen-capture antibody and as alkaline phosphatase-conjugated antibody. The lower detection limit of the TR-IFMA was tenfold lower than that of the ELISA, while the linear range of the TR-IFMA exceeded that of the ELISA one hundred-fold. Serum samples of 80 Burundese individuals infected with Schistosoma mansoni (egg counts ranging from 4 to 2583 eggs per gram of faeces) were tested in both assays. Antigen concentrations in serum of individuals infected with S. mansoni ranged from 0-500 ng AWA-TCA per ml. The correlation between antigen levels measured by TR-IFMA and ELISA was good: Spearman's p = 0.92. Whereas in the ELISA the samples had to be titrated, the wide linear range of the TR-IFMA allowed the assay to be performed at a single serum dilution, at which an exact estimation of the antigen concentration was possible.
de Jonge
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Laboratory of Parasitology, Medical Faculty, University of Leiden, The Netherlands.
Boerman
O C
OC
Deelder
A M
AM
D000293:Adolescent; D000328:Adult; D000818:Animals; D000947:Antigens, Helminth / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D015200:Fluoroimmunoassay; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012550:Schistosoma mansoni / Q000276:immunology*; D012555:Schistosomiasis mansoni / Q000175:diagnosis*
D000947:Antigens, Helminth