Navegando por Autor "Valadares, Helder Magno Silva"
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Item Impact of dual infections on chemotherapeutic efficacy in balb/c mice infected with major genotypes of trypanosoma cruzi.(2007) Martins, Helen Rodrigues; Silva, Rodrigo Moreira da; Valadares, Helder Magno Silva; Toledo, Max Jean de Ornelas; Veloso, Vanja Maria; Avelar, Danielle Marchetti Vitelli; Carneiro, Cláudia Martins; Coelho, George Luiz Lins Machado; Bahia, Maria Terezinha; Martins Filho, Olindo Assis; Macedo, Andréa Mara; Lana, Marta deThe aim of this work was to investigate the impact of dual infections with stocks of Trypanosoma cruzi major genotypes on benznidazole (BZ) treatment efficacy. For this purpose, T. cruzi stocks representative of the genetic T. cruzi lineages, displaying different susceptibilities to BZ, belonging to the major T. cruzi genotypes broadly dispersed in North and South America and important in Chagas’ disease epidemiology were used. Therapeutic efficacy was observed in 27.8% of the animals treated. Following BZ susceptibility classification, significant differences were observed in dual infections on the major genotype level, demonstrating that combinations of genotypes 19 39 and genotypes 19 32 led to a shift in the expected BZ susceptibility profile toward the resistance pattern. Analysis on the T. cruzi stock level demonstrated that 9 out of 24 dual infections shifted the expected BZ susceptibility profile compared with the respective single infections, including shifts toward lower and higher BZ susceptibilities. Microsatellite identification was able to identify a mixture of T. cruzi stocks in 7.7% of the T. cruzi isolates from infected and untreated mice (6.9%) and infected and treated but not cured mice (9.0%), revealing in some mixtures of BZ-susceptible and -resistant stocks that the T. cruzi stock identified after BZ treatment was previously susceptible in single infections. Considering the clonal structure and evolution of T. cruzi, an unexpected result was the identification of parasite subpopulations with distinct microsatellite alleles in relation to the original stocks observed in 12.2% of the isolates. Taken together, the data suggest that mixed infections, already verified in nature, may have an important impact on the efficacy of chemotherapy.Item Molecular and biological characterization of Trypanosoma cruzi strains isolated from children from Jequitinhonha Valley, State of Minas Gerais, Brazil.(2013) Silva, Jaquelline Carla Valamiel de Oliveira e; Assis, Girley Francisco Machado de; Oliveira, Maykon Tavares de; Valadares, Helder Magno Silva; Valle, Ítalo Faria do; Paiva, Nívia Carolina Nogueira de; Martins, Helen Rodrigues; Lana, Marta deThe 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 prepatent 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 infl ammation, but fi brosis 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 confi rmed 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 infl ammatory processes and fi brosis.Item Trypanosoma cruzi : impact of dual-clone infections on parasite biological properties in BALB/c mice.(2006) Martins, Helen Rodrigues; Toledo, Max Jean de Ornelas; Veloso, Vanja Maria; Carneiro, Cláudia Martins; Coelho, George Luiz Lins Machado; Tafuri, Washington Luiz; Bahia, Maria Terezinha; Valadares, Helder Magno Silva; Macedo, Andréa Mara; Lana, Marta deHerein, we have analyzed major biological properties following dual-clone Trypanosoma cruzi infections in BALB/c mice. Eight T. cruzi clonal stocks, two of each principal genotype, including genotype 19 and 20 (T. cruzi I), hybrid genotype 39 (T. cruzi) and 32 (T. cruzi II) were combined into 24 diVerent dual-clone infections. Special attention was given to characterize biological parameters assayed including: prepatent period, patent period, maximum of parasitemia, day of maximum parasitemia, area under the parasitemia curve, infectivity, mortality, and hemoculture positivity. Our Wndings clearly demonstrated that features resultant of dual-clone infections of T. cruzi clonal stocks did not display either the characteristics of the corresponding monoclonal infections or the theoretical mixture based on the respective monoclonal infections. SigniWcant changes in the expected values were observed in 4.2–79.2% of the mixtures considering the eight biological parameters studied. A lower frequency of signiWcant diVerences was found for mixtures composed by phylogenetically distant clonal stocks. Altogether, our data support our hypothesis that mixed T. cruzi infections have a great impact on the biological properties of the parasite in the host and re-emphasizes the importance of considering the possible occurrence of natural mixed infections in humans and their consequences on the biological aspects of ongoing Chagas’ disease.Item Unequivocal identification of subpopulations in putative multiclonal Trypanosoma cruzi strains by FACs single cell sorting and genotyping.(2012) Valadares, Helder Magno Silva; Pimenta, Juliana Ramos; Segatto, Marcela; Veloso, Vanja Maria; Gomes, Mônica Lúcia; Chiari, Egler; Gollob, Kenneth John; Bahia, Maria Terezinha; Lana, Marta de; Franco, Glória Regina; Machado, Carlos Renato; Pena, Sérgio Danilo Junho; Macedo, Andréa MaraTrypanosoma cruzi, the etiological agent of Chagas disease, is a polymorphic species. Evidence suggests that the majority of the T. cruzi populations isolated from afflicted humans, reservoir animals, or vectors are multiclonal. However, the extent and the complexity of multiclonality remain to be established, since aneuploidy cannot be excluded and current conventional cloning methods cannot identify all the representative clones in an infection. To answer this question, we adapted a methodology originally described for analyzing single spermatozoids, to isolate and study single T. cruzi parasites. Accordingly, the cloning apparatus of a Fluorescence-Activated Cell Sorter (FACS) was used to sort single T. cruzi cells directly into 96-wells microplates. Cells were then genotyped using two polymorphic genomic markers and four microsatellite loci. We validated this methodology by testing four T. cruzi populations: one control artificial mixture composed of two monoclonal populations – Silvio X10 cl1 (TcI) and Esmeraldo cl3 (TcII) – and three naturally occurring strains, one isolated from a vector (A316A R7) and two others derived from the first reported human case of Chagas disease. Using this innovative approach, we were able to successfully describe the whole complexity of these natural strains, revealing their multiclonal status. In addition, our results demonstrate that these T. cruzi populations are formed of more clones than originally expected. The method also permitted estimating of the proportion of each subpopulation of the tested strains. The single-cell genotyping approach allowed analysis of intrapopulation diversity at a level of detail not achieved previously, and may thus improve our comprehension of population structure and dynamics of T. cruzi. Finally, this methodology is capable to settle once and for all controversies on the issue of multiclonality.