Schistosoma mansoni and S. japonicum: decline of antibodies against diagnostic adult worm antigens (Sm31/32) following praziquantel treatment of mice.

Mice were infected with 10, 100 or 200 cercariae of Schistosoma mansoni or S. japonicum and treated between one and two months later with two doses of praziquantel. At this time, the animals had high levels of antibodies against the adult worm proteins Sm31/32 (schistosome cathepsin B and haemoglobinase). Antibody levels were followed up for about one more year by Western blots and ELISA using purified Sm31/32. Among the 34 surviving mice perfused at the end of the experiments, 14 had between 1 and 4 and one mouse had 8 residual stunted worms. In most mice without detectable worms, anti-Sm31/32 antibodies started to drop within a few months after therapy. In other animals of this group and in those harbouring residual worms, the decrease in titers was not observed or less pronounced. Thus, the presence of even one stunted worm was sufficient to induce continued high titres of antibodies. Decreasing levels of antibody against Sm31/32, however, reflected complete elimination of schistosomes.