Development of fluorescent antibodies directed against larval stages, eggs, and adults of Schistosoma mansoni in mice harbouring unisexual or bisexual infections.

The development of antibodies corresponding to the different developmental phases of Schistosoma mansoni was studied in mice subjected to experimental unisexual and bisexual infections. Blood samples were taken at weekly intervals for up to 5 months and tested by indirect immunofluorescence against frozen sections of male and female worms (collected from animals with unisexual infections), of liver of infected hamsters (containing schistosome eggs) and of the hepatopancreas of infected snails (containing schistosome larval stages). Antibodies appeared around the 10th day. The earlier appearance of antilarval antibodies observed previously could not be confirmed. The study of unisexual infections demonstrated that anti-egg antibodies can be differentiated from antilarval and anti-adult worm antibodies. With all four antigens a stronger serological reaction was obtained in bisexual than in unisexual infections. The anti-male antibodies were always present at higher concentrations than the anti-female antibodies.