Anti-schistosome chemotherapy enhanced by antibodies specific for a parasite esterase.

The immune-dependent action of praziquantel has been investigated in Schistosoma mansoni-infected mice by passive transfer of rabbit antisera simultaneously with drug treatment. Significant synergistic activity was obtained with polyspecific sera against culture medium extracts of adult worms, but not with sera against detergent extracts or whole worm homogenates. Serum from a rabbit 'infected' with unattenuated S. mansoni cercariae was also synergistically active with praziquantel, and from this serum were derived two further active and monospecific sera which immunoprecipitated a 27,000 MW antigen with non-specific esterolytic enzyme activity. The antigen against which the monospecific sera reacted was detected by indirect immunofluorescence on the tubercles of drug-treated worms, but not on control worms. The immune-dependence of praziquantel thus appears related to drug-induced damage on the surface on the worm, which results in exposure of antigens sensitive to damage by antibody.