THE SUSCEPTIBILITY OF ADULT SCHISTOSOMES TO IMMUNE ATTRITION

Mouse infection models are described that demonstrate reduction of egg production in Schistosoma haematobium infections and both worm loss a nd reduced fecundity in S. bovis infections. Neither phenomenum could be shown in S. mansoni infected mice. The immunological basis for thes e anti-adult responses was inferred by comparison with infections in T -cell deprived mice and by serum transfer of the ability to reduce a S . bovis worm burden into immunocompromised hosts. Vaccination with irr adiation attenuated parasites was also shown to have consequences for the adults of a challenge infection of S. haematobium and S. bovis spe cifically. Prior vaccination resulted in an abrogation of the anti-fec undity and adult worm elimination that occurred in non-vaccinated simi larly infected mice. These models are being used to define the targets and mechanisms involved in anti-adult attrition. A serological assay, quantitation of a circulating antigen (CAA) has been assessed for its ability to measure worm burdens of different species of schistosome i n mice. This assay will be used to question whether anti-adult immunit y contributes to the pattern of infection with S. mansoni and S. haema tobium in man.