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Protection of mice against Schistosoma mansoni infection by passive transfer of sera from infected rabbits

Sera from rabbits infected with unattenuated Schistosoma mansoni cercariae conferred significant levels of protection against S. mansoni challenge (P < 0.001) after passive transfer to mice. Infected rabbit sera were only effective in conferring protection when transferred during the first week of infection, and were not effective when administered against liver‐stage worms. Immunoglobulins isolated from the infected rabbit sera with Protein A‐Sepharose were shown to be responsible for the transfer of protection to mice. Immunofluorescence studies demonstrated that the sera were more reactive against the surface of three hour‐old mechanically transformed schistosomula than against the surfaces of lung‐stage schistosomula. The sera from infected rabbits reacted polyspecifically against antigens in cercaria, schistosomula, and the worm and egg stages of the S. mansoni life‐cycle. The host parasite relationship of S. mansoni in the rabbit is discussed.