IMMUNE ATTRITION OF ADULT SCHISTOSOMES

Mouse infection models are described that demonstrate reduction in the rate of egg production in Schistosoma haematobium worms 6-10 weeks af ter the onset of oviposition and loss of Schistosoma bovis worms aroun d 10 weeks after infection. Neither phenomenon has been shown in Schis tosoma mansoni- or Schistosoma japonicum-infected mice. The immunologi cal basis for these anti-adult responses was inferred by comparison wi th infections in T-cell deprived mice and by transferance of the abili ty to reduce a S. bovis worm burden in immuno-compromised hosts with i mmune serum. Vaccination with irradiation-attenuated parasites of S. h aematobium was also shown to have consequences for the adults of chall enge infections of either S. haematobium or of S. bovis, but not of S. mansoni. Thus, prior vaccination resulted in an abrogation of the red uced egg production by S. haematobium and S. bovis worms and also of t he adult worm elimination that occurred in non-vaccinated S. bovis-inf ected mice. These models are being used to define the targets and mech anisms involved in the attrition of adult worms of schistosomes with t erminal spined eggs.