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

Identification of immunodominant antigens in Mexican strains of Trypanosoma cruzi

Chagas disease represents an important public health problem. In Mexico most studies have been performed using Trypanosoma cruzi' antigens extracted from strains of other geographical origins. This work was aimed at developing a reactive antigen to perform serological diagnosis of Chagas' disease, using Mexican T. cruzi strains. We prepared antigenic extracts from epimastigotes, trypomastigotes and sphaeromastigotes of three Mexican strains. Parasites homogenate was obtained by lysis and sonication, solubilized proteins were analyzed by SDS-PAGE, Western-blot assays, and ELISA to determine the reactivity against sera from chagasic reference serum and chagasic and leishmaniasic patients and healthy donors. Western Blot profiles revealed, with the reference serum, eleven main components between 212 to 25 kDa; however, five bands corresponding to 74, 44, 31, 25 and 18 kDa antigens were recognized by the T. cruzi reactive sera from Mexican chagasic patients, which did not cross-react with Leishmania mexicana. Antigens from the Tequesquitengo strain yielded the best reactivity in the enzymatic immunoassay, thus enabling us to propose their use for serodiagnoses of Chagas' disease in Mexico.

Deletion of an immunodominant Trypanosoma cruzi surface glycoprotein disrupts flagellum-cell adhesion

Null mutants of the Trypanosoma cruzi insect stage-specific glycoprotein GP72 were created by targeted gene replacement. Targeting plasmids were constructed in which the neomycin phosphotransferase and hygromycin phosphotransferase genes were flanked by GP72 sequences. These plasmids were sequentially transfected into T. cruzi epimastigotes by electroporation. Southern blot analyzes indicated that precise replacement of the two genes had occurred. No aberrant rearrangements occurred at the GP72 locus and no GP72 gene sequences had been translocated elsewhere in the genome. Western blots confirmed that GP72 is not expressed in these null mutants. The morphology of the mutants is dramatically different from wild-type. In both mutant and wild-type parasites, the flagellum emerges from the flagellar pocket. In the null mutant the normal attachment of the flagellum to the cell membrane of the parasite is lost.

Characterization of a candidate gene for GP72, an insect stage-specific antigen of Trypanosoma cruzi

The Trypanosoma cruzi insect stage-specific antigen GP72 was purified from epimastigotes and the amino acid sequences of peptide fragments determined. Oligonucleotides derived from these data were used to amplify and clone a cDNA sequence, which was used to isolate a full-length gene. All the sequenced peptides were encoded within the gene. The characteristics of the encoded 62,600-Da protein, including a potential amino-terminal signal sequence, a hydrophobic carboxy-terminus, and a large number of potential O-glycosylation sites, are consistent with the properties of GP72. No sequence homologies were found in searches of DNA and protein data banks. GP72 is encoded by a single pair of non-telomeric allelic genes.

Serodiagnosis of Chagas' disease using monoclonal antibody against Trypanosoma cruzi-specific Mr 25,000 antigen

A mouse monoclonal antibody TCF87, prepared previously, was reactive with Trypanosoma cruzi-specific Mr 25,000 antigen regardless of strain. The Mr 25,000 antigen was recognized by all sera from chagasic patients living in different areas of South America, when examined by Western immunoblotting analysis. Although many antigens of T. cruzi epimastigotes were also recognized by sera from patients with leishmaniasis, the Mr 25,000 antigen of T. cruzi did not react with leishmaniasic sera. These results indicate that Mr 25,000 antigen recognized by TCF87 is valuable as a diagnostic antigen for Chagas' disease. When a competition enzyme-linked immunosorbent assay using TCF87 was carried out, all sera from Chagas' disease patients showed positive inhibition. By contrast, all patients with leishmaniasis or other parasitic diseases were scored as seronegative. The present study suggests that competition enzyme-linked immunosorbent assay using monoclonal antibody against the Mr 25,000 antigen of T. cruzi will be useful for serodiagnosis of Chagas' disease in areas where leishmaniasis is co-endemic.