The Use of Lyophilized Schistosoma Mansoni Eggs as Antigenic Particles in a Radioimmunoassay

Lyophilized eggs of Schistosoma mansoni, when incubated briefly with serum from infected mice, bind antibodies, as made evident by subsequent binding of flurorescein labelled anti-IgG or ¹²⁵I-labelled Protein A. On the basis of these findings, a radioimmunoassay was devised which employs whole lyophilized eggs (500 or 250 eggs/serum sample) as antigenic particles and ¹²⁵I-labelled Protein A as a probe for antibody binding. Only 10/d of serum are required to obtain 90% of the maximal binding. Kinetic studies indicated that 70% of the maximal seropositivity develops in mice between five and six weeks after a light infection, reaches a maximum at eight weeks and fluctuates around a high plateau thereafter. Pre-incubation of the test serum with soluble egg antigen (SEA) considerably inhibits antibody binding to the eggs, suggesting that SEA-like antigens participate in the reaction.