Antigenicity of adult Schistosoma mansoni alkaline phosphatase

Antibodies to the alkaline phosphatase (AP) of Schistosoma mansoni in infected human and mice sera were evaluated by a direct solid-phase AP immunoadsorption assay (APIA) and by Western blot and immunostaining. APIA consisted of (a) solid-phase capture of immunoglobulins from infected human or mice, (b) immunoadsorption of the enzyme antigen by the antibodies, and (c) detection of the enzymatic activity. By this procedure the appearance of the anti-AP response in mice was detected around 50 days post-infection; this response was not specific for an AP of a given schistosome strain and it was not induced by an autoimmunity phenomenon. Fourteen out of 15 sera from infected people tested by APIA showed a clear antibody response against this enzyme. Immunoblots in non-reducing conditions supported APIA results indicating that the parasite AP was specifically recognized by the antibodies present in infected human and mice sera. These results suggest the possible usefulness of the schistosome AP as a marker for S. mansoni infection.