We are currently studying the soluble egg
antigens of Schistosoma japonicum in an attempt to determine which
antigens are potent immunogens. Previously, we demonstrated by Ouchterlony immunodiffusion and inhibition of the circumoval precipitin test that the
glycoprotein fraction of soluble egg
antigens contains the
antigens which are most immunogenic in natural
infections. The soluble egg
antigen glycoproteins have now been further fractionated via hydrophobic interaction chromatography on
phenyl Sepharose. We found that there were at least two
antigens involved in the circumoval precipitin reaction. Both the hydrophilic
antigen which we call japonicum
antigen glycoprotein II (JAG II) and a mixture of hydrophobic
antigens (JAG III and the JAG IV complex) were capable of causing a 50% inhibition of the COP reaction around S. japonicum eggs. JAG II was not a major serological
antigen of S. japonicum since it gave only a weak precipitin line upon Ouchterlony immunodiffusion analysis with pooled sera from Filipino patients with chronic S. japonicum
infections. Hydrophobic interaction chromatography yielded preparations which were sufficiently pure for use in radioimmunoassays. By radioimmunoassay, the best
antigens among the
glycoproteins were moderately hydrophobic JAG III and the JAG IV complex. They had large amounts of antibody directed toward them in patients with
schistosomiasis japonica and exhibited little reactivity with S. mansoni. The hydrophilic
glycoproteins JAG I and II were poor immunogens and extensively cross-reacted with S. mansoni. This cross-reactivity means that diagnostic tests with crude soluble egg
antigens would run the risk of potential false-negative results in patients with other
trematode infections.