Antibody response to Salmonella typhi in human schistosomiasis mansoni.

Antibody response to Salmonella typhi O and H antigens was evaluated in 24 individuals with either hepatointestinal or hepatosplenic schistosomiasis mansoni before and after typhoid vaccination, and compared with that of non-infected controls. Before vaccination, Schistosoma-infected patients showed a higher frequency of positive antibody to O antigen and the same frequency to H antigen when compared with that of healthy individuals. However, those with hepatosplenic schistosomiasis showed higher titres of antibody to H antigen than those with hepatointestinal disease or healthy individuals. Infected subjects, particularly those with hepatointestinal disease, showed a decreased response after typhoid vaccine. This diminished ability to mount an immune response towards typhoid antigens during schistosomiasis may interfere with the clearance of the bacteria from blood stream and, therefore, play a role in the prolonged survival of salmonella as observed in some patients with chronic salmonellosis associated with schistosomiasis.