The stage-, strain- and species-specificity of a Schistosoma mansoni egg antigen fraction (CEF6) with serodiagnostic potential

Abstract
The immunological properties of CEF6, a cationic fraction of Schistosoma mansoni egg homogenate (SEA) containing two antigens, omega 1 and alpha 1, have been further investigated in two assays, immunoelectrophoresis (IEP) and enzyme immunoassay (ELISA). Although precipitating antibodies to antigen omega 1 were amongst the first to appear in mice with patient infections, IgG reactivity against CEF6 in ELISA trailed somewhat behind that of IgG activity against unfractionated SEA. Specificity of the two antigens in CEF6 to the egg stage of the parasite life-cycle was demonstrated by the failure of immunizations with cercarial or worm antigens to induce antibodies which reacted against either alpha 1 or omega 1 in IEP, or against CEF6 in ELISA. Mice infected with S. mansoni strains derived from geographically distinct areas, including the Caribbean, South America and Africa, produced antibodies which were reactive against CEF6 prepared from eggs of a Puerto Rican S. mansoni strain that had been maintained in the laboratory for many years. Of the different precipitating anti-SEA antibody species induced by the various S. mansoni strains in mice, those reactive against antigen omega 1 appeared to be present in highest titre. Sera from mice chronically infected with S. japonicum and S. haematobium failed to precipitate CEF6 in IEP and were less reactive with CEF6 than with S. mansoni SEA in ELISA. However, similar degrees of ELISA reactivity against S. mansoni CEF6 and SEA were given by sera from mice infected with S. bovis. The results support the notion that the antigens in CEF6 may be useful in the serodiagnosis of schistosomiasis mansoni infections.

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