Molecular and biological characterization of Trypanosoma cruzi strains isolated from children from Jequitinhonha Valley, State of Minas Gerais, Brazil

Introduction The biological diversity of Trypanosoma cruzi strains plays an important role in the clinical and epidemiological features of Chagas disease. Methods Eight T. cruzi strains isolated from children living in a Chagas disease vector-controlled area of Jequitinhonha Valley, State of Minas Gerais, Brazil, were genetically and biologically characterized. Results The characterizations demonstrated that all of the strains belonged to T. cruzi II, and showed high infectivity and a variable mean maximum peak of parasitemia. Six strains displayed low parasitemia, and two displayed moderate parasitemia. Later peaks of parasitemia and a predominance of intermediate and large trypomastigotes in all T. cruzi strains were observed. The mean pre-patent period was relatively short (4.2±0.25 to 13.7±3.08 days), whereas the patent period ranged from 3.3±1.08 to 34.5±3.52 days. Mortality was observed only in animals infected with strain 806 (62.5%). Histopathological analysis of the heart showed that strains 501 and 806 caused inflammation, but fibrosis was observed only in animals infected with strain 806. Conclusions The results indicate the presence of an association between the biological behavior in mice and the genetic characteristics of the parasites. The study also confirmed general data from Brazil where T. cruzi II lineage is the most prevalent in the domiciliary cycle and generally has low virulence, with some strains capable of inducing inflammatory processes and fibrosis. .

Molecular characterization of Trypanosoma cruzi Mexican strains and their behavior in the mouse experimental model / Caracterização molecular de cepas mexicanas de Trypanosoma cruzi e seu comportamento no modelo experimental do camundongo

INTRODUCTION: For a long time, the importance of Chagas disease in Mexico, where many regarded it as an exotic malady, was questioned. Considering the great genetic diversity among isolates of Trypanosoma cruzi, the importance of this biological characterization, and the paucity of information on the clinical and biological aspects of Chagas disease in Mexico, this study aimed to identify the molecular and biological characterization of Trypanosoma cruzi isolates from different endemic areas of this country, especially of the State of Jalisco. METHODS: Eight Mexican Trypanosoma cruzi strains were biologically and genetically characterized (PCR specific for Trypanosoma cruzi, multiplex-PCR, amplification of space no transcript of the genes of the mini-exon, amplification of polymorphic regions of the mini-exon, classification by amplification of intergenic regions of the spliced leader genes, RAPD - (random amplified polymorphic DNA). RESULTS: Two profiles of parasitaemia were observed, patent (peak parasitaemia of 4.6×10(6) to 10(7) parasites/mL) and subpatent. In addition, all isolates were able to infect 100 percent of the animals. The isolates mainly displayed tropism for striated (cardiac and skeletal) muscle. PCR amplification of the mini-exon gene classified the eight strains as TcI. The RAPD technique revealed intraspecies variation among isolates, distinguishing strains isolated from humans and triatomines and according to geographic origin. CONCLUSIONS: The Mexican T. cruzi strains are myotrophic and belong to group TcI.

INTRODUÇÃO: Durante muito tempo, foi questionada a importância da doença de Chagas no México onde muitos a consideravam um padecimento exótico. Considerando a grande diversidade genética existente, entre os isolados de Trypanosoma cruzi, a importância da caracterização biológica desses e o escasso número de informações sobre os aspectos clínicos e biológicos da doença de Chagas no México, o objetivo deste trabalho foi realizar a caracterização biológica e molecular de isolados de Trypanosoma cruzi originários de diferentes áreas endêmicas deste país, principalmente do Estado de Jalisco. MÉTODOS: Oito cepas mexicanas de Trypanosoma cruzi foram caracterizadas biologicamente e geneticamente (PCR específica para Trypanosoma cruzi, PCR-multiplex, amplificação do espaço não transcrito dos genes do mini-exon, amplificação das regiões polimórficas do gene do mini-exon, classificação pela amplificação de regiões intergênicas dos genes do spliced leader, RAPD - random amplified polymorphic DNA). RESULTADOS: Foram observados dois tipos de parasitemia: patente com picos máximos de parasitemia entre 4,6x10(6) e 10(7) parasitas/mL e subpatente. Além disso, todos os isolados foram capazes de infectar 100 por cento dos animais. Observou-se tropismo predominante pelo músculo estriado (cardíaco e esquelético). As técnicas de PCR do gene do mini-éxon classificaram as oito cepas como TcI e a técnica de RAPD mostrou variação intra-especifica das mesmas, separando as cepas isoladas de humanos daquelas de triatomíneos e por origem geográfica. CONCLUSÕES: As cepas mexicanas de Trypanosoma cruzi são miotrópicas e correspondem ao TcI.

Trypanosoma cruzi: blood parasitism kinetics and their correlation with heart parasitism intensity during long-term infection of Beagle dogs

The goals of the present study were to evaluate the kinetics of blood parasitism by examination of fresh blood, blood culture (BC) and PCR assays and their correlation with heart parasitism during two years of infection in Beagle dogs inoculated with the Be-78, Y and ABC Trypanosoma cruzi strains. Our results showed that the parasite or its kDNA is easily detected during the acute phase in all infected animals. On the other hand, a reduced number of positive tests were verified during the chronic phase of the infection. The frequency of positive tests was correlated with T. cruzi strain. The percentage of positive BC and blood PCR performed in samples from animals inoculated with Be-78 and ABC strains were similar and significantly larger in relation to animals infected with the Y strain.Comparison of the positivity of PCR tests performed using blood and heart tissue samples obtained two years after infection showed two different patterns associated with the inoculated T. cruzi strain: (1) high PCR positivity for both blood and tissue was observed in animals infected with Be-78 or ABC strains; (2) lower and higher PCR positivity for the blood and tissue, respectively, was detected in animals infected with Y strains. These data suggest that the sensitivity of BC and blood PCR was T. cruzi strain dependent and, in contrast, the heart tissue PCR revealed higher sensitivity regardless of the parasite stock.

Trypanosoma cruzi strains isolated from human, vector, and animal reservoir in the same endemic region in Mexico and typed as T. cruzi I, discrete typing unit 1 exhibit considerable biological diversity

In this study, three strains of Trypanosoma cruzi were isolated at the same time and in the same endemic region in Mexico from a human patient with chronic chagasic cardiomyopathy (RyC-H); vector (Triatoma barberi) (RyC-V); and rodent reservoir (Peromyscus peromyscus) (RyC-R). The three strains were characterized by multilocus enzyme electrophoresis, random amplified polymorphic DNA, and by pathological profiles in experimental animals (biodemes). Based on the analysis of genetic markers the three parasite strains were typed as belonging to T. cruzi I major group, discrete typing unit 1. The pathological profile of RyC-H and RyC-V strains indicated medium virulence and low mortality and, accordingly, the strains should be considered as belonging to biodeme Type III. On the other hand, the parasites from RyC-R strain induced more severe inflammatory processes and high mortality (> 40 percent) and were considered as belonging to biodeme Type II. The relationship between genotypes and biological characteristics in T. cruzi strains is still debated and not clearly understood. An expert committee recommended in 1999 that Biodeme Type III would correspond to T. cruzi I group, whereas Biodeme Type II, to T. cruzi II group. Our findings suggest that, at least for Mexican isolates, this correlation does not stand and that biological characteristics such as pathogenicity and virulence could be determined by factors different from those identified in the genotypic characterization

Reinfections with strains of Trypanosoma cruzi, of different biodemes as a factor of aggravation of myocarditis and myositis in mice

Reinfeccões pelo Trypanosoma cruzi em pacientes de áreas endêmicas têm sido mencionadas como fator agravante das manifestacões cardíacas na doenca de Chagas. No presente estudo, a influência da tríplice infeccão com cepas de diferentes biodemas, sobre as lesões do miocárdio e de músculo esquelético foi investigada experimentalmente. Cinqüenta e oito camundongos cronicamente infectados com a cepa Colombiana do Trypanosoma cruzi (Biodema Tipo III) foram sucessivamente reinoculadas como a seguir: 1º grupo - reinfectados com a cepa 21 SF (Tipo II) seguido pela cepa Y (Tipo I); 2º grupo - reinfeccão com a cepa Y seguida pela cepa 21SF. A análise isoenzimática dos parasitas das hemoculturas obtidas dos animais com tríplice infeccão, revelou os padrões dos diferentes zimodemas no mesmo animal. Cada cepa do Trypanosoma cruzi foi re-isolada após quatro passagens em camundongos no 7º, no 14º, ou no 30º dia após a inoculacão com o sangue de camundongos com tríplice infeccão. Resultados da histopatologia demonstraram uma significante exacerbacão das lesões inflamatórias de miocárdio e músculo esquelético, confirmadas pela avaliacão morfométrica. Não foi detectada acentuacão do parasitismo. A possibilidade de aumento da resposta celular nos animais com tríplice infeccão é sugerida.

Experimental Trypanosoma rangeli infection in a mature model

Trypanosoma rangeli experimental murine infections were performed in order to study parasitemias and anti-parasite antibody levels. Three groups of mice were used: a) mice infected with metatrypomastigotes derived from infected bugs; b) mice which received four reinoculations of metatrypomastigotes and c) mice immunosuppressed with cyclophosphamide. The results showed that bloodstream parasites can be found from the first day post inoculation reaching a peak at day 5 or 7 and then start to decline. Parasites disappeared completely from the circulation after 20-25 days. However in the immunosuppressed group, parasites were found in blood up to 45 days post infection. The humoral immune response was monitored using an ELISA test and low levels of specific IgG and IgM unoglobulins were found. However the IgG titers were lower than the IgM. One could conclude that IgM was the predominant immunoglobulin isotype induced in a T. rangeli experimental infection because the highest titers were observed in the reinoculated group. IgM antibodies also showed the most prominent crossreactivities with T. cruzi antigens

Caracterizaçäo de cepas do Trypanosoma cruzi isoladas de doentes nos quais foi realizado transplante de coraçäo / Characterization of Trypanosoma cruzi strains isolated from heart transplanted patients

Three strains of Trypanosoma cruzi were isolated from Chagas' disease patients transplanted for heart failure, after cardiac transplantation, and were studied in an experimental model of Chagas' disease, in mice, with evaluation of parasitic load, mortality and extension of inflammatory infiltrates in the heart. These parameters were compared with the standard strain Y. The strains had differences in the studied parameters, but there was no clear relationship between those and post-transplant evolution of the patients. Probably the clinical response is multifactorial and derives only in part from biological characteristics of the infecting T. cruzi strain, as measured in our model.