No abstract

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.

No abstract

Mice can be partially protected against Schistosoma japonicum by prior exposure to ultraviolet (UV)-attenuated infections which fail to survive to the adult stage and produce no overt pathology in the host. Optimum resistance was induced by parasites exposed to 40 seconds of UV, significantly lower levels of resistance being stimulated by both shorter and longer exposures. No consistent relationship between the degree of resistance induced and the number of irradiated cercariae given could be demonstrated and equivocal results were obtained when comparing the efficacy of single and multiple vaccinations. Vaccinations with UV-attenuated cercariae given intraperitoneally (i.p.) were as efficacious as those given percutaneously but mice were as or more resistant to challenges given by the i.p. route, the possible reasons are discussed. There was no observed delay in the migration of the challenge, vaccinated mice being as resistant when perfused 6 or 3·5 weeks after challenge. Vaccination was species specific since mice exposed to either UV-attenuated S. japonicum cercariae or gamma-attenuated S. mansoni cercariae were resistant to homologous but not heterologous challenge.