Evidence for an immune-dependent action of praziquantel on Schistosoma mansoni in mice.

Effective schistosomicidal action of praziquantel against Schistosoma mansoni infections in mice appears to be dependent to some extent on appropriate immunological stimulation. Indirect evidence consistent with this hypothesis was obtained by demonstrating a positive relationship between drug efficacy and both the intensity and the age of the parasitic infection. More directly, it has previously been shown that praziquantel kills fewer S. mansoni worms in immunosuppressed T cell-deprived mice than in immunologically intact controls; and we show here that infections 5 weeks old, against which the drug alone is sub-optimally active, are more effectively killed by a combination of drug and a rabbit antiserum raised against adult worm antigens.