Evaluation of a Purified Schistosoma japonicum Glycoprotein Egg Antigen for the Immunodiagnosis of Infection in Man *

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Abstract
A purified glycoprotein, glycoprotein-2, which was isolated from Schistosoma japonicum soluble egg antigen, was tested in an enzyme-linked immunoadsorbent assay for its potential as an immunodiagnostic reagent. Using empirically-derived criteria of endpoint titer, 39/40 sera from S. japonicum-infected individuals were scored correctly as positive in a blind test. Of these, 26/40 were from individuals who excreted fewer than 100 eggs per gram of stool. No cross reactions were observed with sera from uninfected individuals (0/20) or from individuals infected with S. mansoni (0/22), Trichinella spiralis (0/6) or Brugia malayi (0/4). Cross reactions were observed with 3/24 individuals infected with S. hematobium who excreted >2,000 eggs per 10 ml urine. Glycoprotein-2 appears to satisfy the requisite criteria of specificity and sensitivity to warrant further evaluation.