Prevalence of antibodies to 72-kilodalton glycoprotein (GP72) in patients with Chagas' disease and further evidence of zymodeme-associated expression of GP72 carbohydrate epitopes.

Three competitive inhibition enzyme-linked immunosorbent assays were developed to examine the expression of the 72-kilodalton glycoprotein (GP72) and of a GP72 carbohydrate epitope in Trypanosoma cruzi strains and clones. A total of 148 strains and clones of known isozyme phenotype (principal zymodeme, Z) were tested. With monoclonal antibody 8G2B9 the enzyme-linked immunosorbent assay confirmed that the majority of Z1 strains and clones derived from them had undetectable levels of the carbohydrate epitope identified by antibody 8G2B9. This epitope was, however, readily detectable in all Z2, Z2(h), and Z3 strains and clones (P less than 0.001; 148 strains and clones tested). Zymodeme-associated differences in GP72 expression were not apparent from the enzyme-linked immunosorbent assay with monoclonal antibody WIC 226.4 (raised against periodate-treated GP72) or from that with rabbit anti-GP72 antiserum (84 or 119 strains and clones tested, respectively). Mice infected with culture-form metacyclic trypomastigotes of Z1, Z29, and Z3 or with blood-form trypomastigotes of Z1 and Z3 developed antibodies to affinity-purified GP72, showing that at least some GP72 epitopes are neither zymodeme specific nor stage specific. A total of 128 serum samples from patients with acute or clinically classified chronic Chagas' disease were assayed for immunoglobulin G (IgG) or IgM anti-GP72 antibodies. During the acute phase anti-GP72 IgM antibodies were elevated, whereas anti-GP72 IgG antibodies were low. There were no significant differences in anti-GP72 antibody levels among chronic-phase patient groups. Anti-GP72 antibodies were detected irrespective of the geographical origin of patients and irrespective of whether acute-phase blood parasitemias were due to Z1 (four patients) or Z2 (two patients).