Isolation and Characterization of a Blood P1 Active Carbohydrate Antigen of Echinococcus Granulosus Cyst Membrane

A glycoprotein antigen was isolated from the membrane of hydatid cysts of sheep and human origin. The constituent sugars of the carbohydrate moiety of this antigen are galactose, galactosamine, and glucosamine. The antigen shows a high P1 blood group activity when tested by hemagglutination-inhibition assay with anti-P1 sera. Moreover, it precipitates 11 out of 21 sera of human patients with echniococcosis. However, none of these sera has complete or incomplete agglutinating anti-P1 antibodies. The immunochemical analysis shows that P1 determinants reactive with anti-P1 sera, and antigenic determinants reactive with human precipitating antibodies are on the same macromolecule. Patients with cyst pulmonary localization show a higher reactivity as compared with those with hepatic localization. The immunodominant group involved in the precipitin reaction appears to be an α-galactosyl residue.