Purification and characterization of an 80-kilodalton Trypanosoma cruzi urinary antigen

Abstract

A Trypanosoma cruzi antigen eliminated in the urine of experimentally infected dogs was detected by enzyme-linked immunosorbent assay between 9 and 28 days after infection. The parasite urinary antigen (UAg) was purified by affinity chromatography with polyclonal antibodies to T. cruzi. The eluate of the antibody column was subjected to high-performance liquid chromatography and showed a single peak of A280. This antigen was the only parasite component found in the urine of infected dogs during the course of acute T. cruzi infection. Antigen characterization was performed by two-dimensional gel electrophoresis, lectin affinity chromatography, proteolytic digestion, and Western blotting (immunoblotting). The isolated UAg exhibited a relative molecular size of 80 kilodaltons (kDa), an isoelectric point of 6.2 to 6.8, binding to concanavalin A, and sensitivity to trypsin. The parasite antigen was electroeluted from polyacrylamide gels and subjected to acid hydrolysis and amino acid analysis by reverse-phase high-performance liquid chromatography. The 80-kDa glycoprotein was recognized by serum antibodies from a wide variety of T. cruzi-infected hosts. The UAg proved to be a highly antigenic component present in different strains of T. cruzi. This 80-kDa polypeptide resembles one of the parasite antigens previously found in the urine of patients with acute Chagas' disease.