ABSTRACT
Analysis of zymograms of extracts of Trypanosoma cruzi isolated from different hosts in Argentina allowed characterization of 12 zymodemes or "isozymic strains," only six of which were found in human patients. Two of these six zymodemes (Z1 and Z12) were widely distributed and found in more than 80% of human patients. These two "major natural clones" differed significantly in pathogenic activity. Because the groupings obtained by studying enzymes and kinetoplast DNA (kDNA) were similar, it is possible to identify the zymodeme by analyzing kDNA. A 290-bp fragment was amplified by PCR using primers for the sequences flanking the hypervariable regions of kDNA minicircles. Labeled probes for this fragment, prepared from Z1 and Z12 reference stocks, hybridized specifically with PCR-amplified kDNA from parasite stocks, allowing identification of zymodemes.
Subject(s)
Chagas Disease/parasitology , DNA, Kinetoplast/analysis , Isoenzymes/analysis , Trypanosoma cruzi/enzymology , Trypanosoma cruzi/genetics , Adolescent , Adult , Aged , Animals , DNA Probes , Female , Humans , Isoenzymes/genetics , Male , Middle Aged , Nucleic Acid Hybridization , Polymerase Chain Reaction/methods , Trypanosoma cruzi/classificationABSTRACT
Trypanosoma cruzi isolated from 55 chronic chagasic patients were grouped into isozymic strains on the basis of electrophoretic patterns for a set of six enzymes. The total sample showed a distribution of asymptomatic (63.6%) and clinically ill (36.4%) patients similar to that generally reported for Chagas' disease. Six of the 12 zymodemes known to exist in Argentina have been isolated from humans. Only two (Z1 and Z12) are frequent and widely distributed in the endemic area. These two zymodemes differ significantly in their pathogenicity. The proportion of asymptomatic patients was higher with the Z1 zymodeme (81.1%) than with the Z12 zymodeme (27.3%). The incidence of heart alterations was lower in Z1 than in Z12 zymodeme patients (18.9% versus 72.7%). Clinically evident acute disease was seen in 36.3% of cases with zymodeme Z12 and in 8.1% of cases with zymodeme Z1. The differences between the two prevalent zymodemes in Argentina are statistically significant. These observations indicate that the Z1 T. cruzi is a more benign strain than Z12. Patients infected with Z1 would be more likely to be asymptomatic for a longer time than those infected with Z12. The risk of cardiac lesion would be greater for patients harboring Z12 T. cruzi than for those with Z1. The results suggest that strain identification could be a useful prognostic tool.
Subject(s)
Chagas Disease/parasitology , Heart/physiopathology , Trypanosoma cruzi/classification , Acute Disease , Adult , Aged , Animals , Chagas Cardiomyopathy/parasitology , Chagas Cardiomyopathy/physiopathology , Chagas Disease/physiopathology , Electrocardiography , Humans , Middle Aged , Trypanosoma cruzi/enzymologyABSTRACT
Isolates of Trypanosoma cruzi from human patients, domestic and sylvatic animals and vector insects were obtained in different areas of Argentina. Electrophoretic patterns of enzymes from extracts of 95 isolates were analysed. On the basis of zymograms providing information on 10 loci, 12 zymodemes are described according to their genotypes. Data presented show fixed heterozygosity, absence of segregation of genotypes, significant departures from Hardy-Weinberg equilibrium, and over-represented genotypes. This evidence supports the hypothesis that sexual reproduction is very restricted or absent in this parasite. The proportion of polymorphic loci is 80%. The expected mean heterozygosity per locus (He) is 0.43, while the observed value (Ho) is 0.24. Differences between these values may be explained by accepting a basically clonal structure for T. cruzi. The data matrix of 12 zymodemes using 28 characters was analysed using a Wagner parsimony algorithm. Two equally most parsimonious unrooted trees were generated; both have 39 steps. The results show clusters clearly separated according to the geographical origin of the stocks. There are some indications of some correlations between genetic composition of the parasite and the clinical picture of the infection in human patients.
Subject(s)
Chagas Disease/epidemiology , Isoenzymes , Polymorphism, Genetic , Trypanosoma cruzi/enzymology , Trypanosoma cruzi/genetics , Animals , Animals, Domestic , Animals, Wild , Argentina/epidemiology , Chagas Disease/congenital , Chronic Disease , Genes, Protozoan , Genetic Linkage , Genotype , Heterozygote , Humans , Insect Vectors , Triatoma/parasitology , Trypanosoma cruzi/classificationABSTRACT
Polyacrylamide gel electrophoretic patterns for six enzymes in 73 isolates and 38 clones of Trypanosoma cruzi from different areas of Argentina were classified into 12 zymodemes. The isolates were obtained from human patients with acute, chronic or congenital Chagas' disease, vector insects, domestic and sylvatic animals. Two out of 8 isolates cloned were shown to be heterogeneous. Zymodemes 1 and 12 exhibit widespread geographic distribution; isolates belonging to both zymodemes account for 55% of the total analyzed. The other zymodemes are not widely geographically dispersed. Although there is a clear predominance of zymodeme 1 among asymptomatic patients, the data do not show a clear relationship between particular zymodemes and the clinical picture. The results suggest that the sylvatic and domestic transmission cycles overlap. This remarkable heterogeneity of T. cruzi in Argentina supports the possible multiclonal origin of these parasite populations.
