共查询到20条相似文献,搜索用时 78 毫秒
1.
Valdirene dos Santos Lima Samanta Cristina das Chagas Xavier Irene Fabíola Roman Maldonado André Luiz Rodrigues Roque Ana Carolina Paulo Vicente Ana Maria Jansen 《PloS one》2014,9(12)
Trypanosoma cruzi infection is a complex sylvatic enzooty involving a wide range of animal species. Six discrete typing units (DTUs) of T. cruzi, named TcI to TcVI, are currently recognized. One unanswered question concerning the epidemiology of T. cruzi is the distribution pattern of TcII and hybrid DTUs in nature, including their virtual absence in the Brazilian Amazon, the current endemic area of Chagas disease in Brazil. Herein, we characterized biological samples that were collected in previous epizootiological studies carried out in the Amazon Basin in Brazil. We performed T. cruzi genotyping using four polymorphic genes to identify T. cruzi DTUs: mini-exon, 1f8, histone 3 and gp72. This analysis was conducted in the following biological samples: (i) two T. cruzi isolates obtained by culturing of stools from the triatomine species Rhodnius picttipes and (ii) five serum samples from dogs in which trypomastigotes were observed during fresh blood examination. We report for the first time the presence of TcII and hybrid DTUs (TcV/TcVI) in the Amazon region in mixed infections with TcI. Furthermore, sequencing of the constitutive gene, gp72, demonstrated diversity in TcII even within the same forest fragment. These data show that TcII is distributed in the five main Brazilian biomes and is likely more prevalent than currently described. It is very probable that there is no biological or ecological barrier to the transmission and establishment of any DTU in any biome in Brazil. 相似文献
2.
Paula G. Ragone Cecilia Pérez Brandán Mercedes Monje Rumi Nicolás Tomasini Juan J. Lauthier Rubén O. Cimino Alejandro Uncos Federico Ramos Anahí M. Alberti D′Amato Miguel A. Basombrío Patricio Diosque 《PloS one》2015,10(3)
Many infectious diseases arise from co-infections or re-infections with more than one genotype of the same pathogen. These mixed infections could alter host fitness, the severity of symptoms, success in pathogen transmission and the epidemiology of the disease. Trypanosoma cruzi, the etiological agent of Chagas disease, exhibits a high biological variability often correlated with its genetic diversity. Here, we developed an experimental approach in order to evaluate biological interaction between three T. cruzi isolates belonging to different Discrete Typing Units (DTUs TcIII, TcV and TcVI). These isolates were obtained from a restricted geographical area in the Chaco Region. Different mixed infections involving combinations of two isolates (TcIII + TcV, TcIII + TcVI and TcV + TcVI) were studied in a mouse model. The parameters evaluated were number of parasites circulating in peripheral blood, histopathology and genetic characterization of each DTU in different tissues by DNA hybridization probes. We found a predominance of TcVI isolate in blood and tissues respect to TcIII and TcV; and a decrease of the inflammatory response in heart when the damage of mice infected with TcVI and TcIII + TcVI mixture were compared. In addition, simultaneous presence of two isolates in the same tissue was not detected. Our results show that biological interactions between isolates with different biological behaviors lead to changes in their biological properties. The occurrence of interactions among different genotypes of T. cruzi observed in our mouse model suggests that these phenomena could also occur in natural cycles in the Chaco Region. 相似文献
3.
Juan M. Burgos Marikena G. Risso Simone Frédérique Brenière Christian Barnabé Oscar Campetella María Susana Leguizamón 《PloS one》2013,8(3)
Trypanosoma cruzi the agent of Chagas disease is a monophyletic but heterogeneous group conformed by several Discrete Typing Units (DTUs) named TcI to TcVI characterized by genetic markers. The trans-sialidase (TS) is a virulence factor involved in cell invasion and pathogenesis that is differentially expressed in aggressive and less virulent parasite stocks. Genes encoding TS-related proteins are included in a large family divided in several groups but only one of them contains TS genes. Two closely related genes differing in a T/C transition encode the enzymatically active TS (aTS) and a lectin-like TS (iTS). We quantified the aTS/iTS genes from TcII and TcVI aggressive and TcI low virulent strains and found variable aTS number (1–32) per haploid genome. In spite of being low TS enzyme-expressers, TcI strains carry 28–32 aTS gene copies. The intriguing absence of iTS genes in TcI strains together with the presence of aTS/iTS in TcII and TcVI strains (virulent) were observed. Moreover, after sequencing aTS/iTS from 38 isolates collected along the Americas encompassing all DTUs, the persistent absence of the iTS gene in TcI, TcIII and TcIV was found. In addition, the sequence clustering together with T/C transition analysis correlated to DTUs of T. cruzi. The consistence of TS results with both evolutionary genome models proposed for T. cruzi, namely the “Two Hybridization” and the “Three Ancestor” was discussed and reviewed to fit present findings. Parasite stocks to attempt genetic KO or to assay the involvement of iTS in parasite biology and virulence are finally available. 相似文献
4.
Brenière SF Aliaga C Waleckx E Buitrago R Salas R Barnabé C Tibayrenc M Noireau F 《PLoS neglected tropical diseases》2012,6(5):e1650
Background
The current persistence of Triatoma infestans (one of the main vectors of Chagas disease) in some domestic areas could be related to re-colonization by wild populations which are increasingly reported. However, the infection rate and the genetic characterization of the Trypanosoma cruzi strains infecting these populations are very limited.Methodology/Principal Findings
Of 333 wild Triatoma infestans specimens collected from north to south of a Chagas disease endemic area in Bolivia, we characterized 234 stocks of Trypanosoma cruzi using mini-exon multiplex PCR (MMPCR) and sequencing the glucose phosphate isomerase (Gpi) gene. Of the six genetic lineages (“discrete typing units”; DTU) (TcI-VI) presently recognized in T. cruzi, TcI (99.1%) was overdominant on TcIII (0.9%) in wild Andean T. infestans, which presented a 71.7% infection rate as evaluated by microscopy. In the lowlands (Bolivian Chaco), 17 “dark morph” T. infestans were analyzed. None of them were positive for parasites after microscopic examination, although one TcI stock and one TcII stock were identified using MMPCR and sequencing.Conclusions/Significance
By exploring large-scale DTUs that infect the wild populations of T. infestans, this study opens the discussion on the origin of TcI and TcV DTUs that are predominant in domestic Bolivian cycles. 相似文献5.
Eric Dumonteil Ardem Elmayan Alicia Majeau Weihong Tu Brandy Duhon Preston Marx Wendy Wolfson Garry Balsamo Claudia Herrera 《PLoS neglected tropical diseases》2020,14(12)
BackgroundChagas disease is a neglected zoonosis of growing concern in the southern US, caused by the parasite Trypanosoma cruzi. We genotyped parasites in a large cohort of PCR positive dogs to shed light on parasite transmission cycles and assess potential relationships between parasite diversity and serological test performance.Methodology/principal findingsWe used a metabarcoding approach based on deep sequencing of T. cruzi mini-exon marker to assess parasite diversity. Phylogenetic analysis of 178 sequences from 40 dogs confirmed the presence of T. cruzi discrete typing unit (DTU) TcI and TcIV, as well as TcII, TcV and TcVI for the first time in US dogs. Infections with multiple DTUs occurred in 38% of the dogs. These data indicate a greater genetic diversity of T. cruzi than previously detected in the US. Comparison of T. cruzi sequence diversity indicated that highly similar T. cruzi strains from these DTUs circulate in hosts and vectors in Louisiana, indicating that they are involved in a shared T. cruzi parasite transmission cycle. However, TcIV and TcV were sampled more frequently in vectors, while TcII and TcVI were sampled more frequently in dogs.Conclusions/significanceThese observations point to ecological host-fitting being a dominant mechanism involved in the diversification of T. cruzi-host associations. Dogs with negative, discordant or confirmed positive T. cruzi serology harbored TcI parasites with different mini-exon sequences, which strongly supports the hypothesis that parasite genetic diversity is a key factor affecting serological test performance. Thus, the identification of conserved parasite antigens should be a high priority for the improvement of current serological tests. 相似文献
6.
7.
Tapan Bhattacharyya Jessica Brooks Hernan J. Carrasco Martin S. Llewellyn 《International journal for parasitology》2010,40(8):921-928
Chagas disease, marked by life-long chronic infection with Trypanosoma cruzi, remains a major parasitic disease in Latin America. Genetically heterogeneous, T. cruzi is divided into six discrete typing units (DTUs), most recently grouped as TcI-VI. The trypomastigote small surface antigen (TSSA) of T. cruzi has been described as the only known serological marker to identify infection by TcII-VI, as distinct from TcI. Here, by comparative analysis of a cohort of 25 reference strains representing all the known DTUs, we show that TSSA intra-specific diversity is greater than previously reported. Furthermore, TcIII and IV TSSA PCR products are, contrary to expectation, both digested by PvuII, revealing a more nuanced genotyping pattern. Amino acid sequence diversity reveals that the TSSA epitope considered to be serologically characteristic of TcII-VI is restricted to TcII, V and VI, but not of III or IV, and that the diagnostic peptide described as TcI-specific shares key features with TcIII and IV. Notably, TSSA sequences inferred greater phylogenetic affinities of TcIII and IV to TcI than to TcII, V or VI. A high ratio of non-synonymous to synonymous nucleotide substitutions (ω = 1.233) indicates that the TSSA gene has been under positive selection pressure. The demonstration of lineage-specific epitopes within TcII-VI has implications for sero-epidemiological studies of Chagas disease based on this antigen. 相似文献
8.
9.
Ramírez JD Guhl F Rendón LM Rosas F Marin-Neto JA Morillo CA 《PLoS neglected tropical diseases》2010,4(11):e899
Chagas disease caused by Trypanosoma cruzi is a complex disease that is endemic and an important problem in public health in Latin America. The T. cruzi parasite is classified into six discrete taxonomic units (DTUs) based on the recently proposed nomenclature (TcI, TcII, TcIII, TcIV, TcV and TcVI). The discovery of genetic variability within TcI showed the presence of five genotypes (Ia, Ib, Ic, Id and Ie) related to the transmission cycle of Chagas disease. In Colombia, TcI is more prevalent but TcII has also been reported, as has mixed infection by both TcI and TcII in the same Chagasic patient. The objectives of this study were to determine the T. cruzi DTUs that are circulating in Colombian chronic Chagasic patients and to obtain more information about the molecular epidemiology of Chagas disease in Colombia. We also assessed the presence of electrocardiographic, radiologic and echocardiographic abnormalities with the purpose of correlating T. cruzi genetic variability and cardiac disease. Molecular characterization was performed in Colombian adult chronic Chagasic patients based on the intergenic region of the mini-exon gene, the 24Sα and 18S regions of rDNA and the variable region of satellite DNA, whereby the presence of T.cruzi I, II, III and IV was detected. In our population, mixed infections also occurred, with TcI-TcII, TcI-TcIII and TcI-TcIV, as well as the existence of the TcI genotypes showing the presence of genotypes Ia and Id. Patients infected with TcI demonstrated a higher prevalence of cardiac alterations than those infected with TcII. These results corroborate the predominance of TcI in Colombia and show the first report of TcIII and TcIV in Colombian Chagasic patients. Findings also indicate that Chagas cardiomyopathy manifestations are more correlated with TcI than with TcII in Colombia. 相似文献
10.
Carolina I. Cura Tomas Duffy Raúl H. Lucero Margarita Bisio Julie Péneau Matilde Jimenez-Coello Eva Calabuig María J. Gimenez Edward Valencia Ayala Sonia A. Kjos José Santalla Susan M. Mahaney Nelly M. Cayo Claudia Nagel Laura Barcán Edith S. Málaga Machaca Karla Y. Acosta Viana Laurent Brutus Susana B. Ocampo Christine Aznar Cesar A. Cuba Cuba Ricardo E. Gürtler Janine M. Ramsey Isabela Ribeiro John L. VandeBerg Zaida E. Yadon Antonio Osuna Alejandro G. Schijman 《PLoS neglected tropical diseases》2015,9(5)
Background
Trypanosoma cruzi has been classified into six Discrete Typing Units (DTUs), designated as TcI–TcVI. In order to effectively use this standardized nomenclature, a reproducible genotyping strategy is imperative. Several typing schemes have been developed with variable levels of complexity, selectivity and analytical sensitivity. Most of them can be only applied to cultured stocks. In this context, we aimed to develop a multiplex Real-Time PCR method to identify the six T. cruzi DTUs using TaqMan probes (MTq-PCR).Methods/Principal Findings
The MTq-PCR has been evaluated in 39 cultured stocks and 307 biological samples from vectors, reservoirs and patients from different geographical regions and transmission cycles in comparison with a multi-locus conventional PCR algorithm. The MTq-PCR was inclusive for laboratory stocks and natural isolates and sensitive for direct typing of different biological samples from vectors, reservoirs and patients with acute, congenital infection or Chagas reactivation. The first round SL-IR MTq-PCR detected 1 fg DNA/reaction tube of TcI, TcII and TcIII and 1 pg DNA/reaction tube of TcIV, TcV and TcVI reference strains. The MTq-PCR was able to characterize DTUs in 83% of triatomine and 96% of reservoir samples that had been typed by conventional PCR methods. Regarding clinical samples, 100% of those derived from acute infected patients, 62.5% from congenitally infected children and 50% from patients with clinical reactivation could be genotyped. Sensitivity for direct typing of blood samples from chronic Chagas disease patients (32.8% from asymptomatic and 22.2% from symptomatic patients) and mixed infections was lower than that of the conventional PCR algorithm.Conclusions/Significance
Typing is resolved after a single or a second round of Real-Time PCR, depending on the DTU. This format reduces carryover contamination and is amenable to quantification, automation and kit production. 相似文献11.
Philipp Schwabl Jalil Maiguashca Snchez Jaime A. Costales Sofía Ocaa-Mayorga Maikell Segovia Hernn J. Carrasco Carolina Hernndez Juan David Ramírez Michael D. Lewis Mario J. Grijalva Martin S. Llewellyn 《PLoS genetics》2020,16(12)
Analysis of genetic polymorphism is a powerful tool for epidemiological surveillance and research. Powerful inference from pathogen genetic variation, however, is often restrained by limited access to representative target DNA, especially in the study of obligate parasitic species for which ex vivo culture is resource-intensive or bias-prone. Modern sequence capture methods enable pathogen genetic variation to be analyzed directly from host/vector material but are often too complex and expensive for resource-poor settings where infectious diseases prevail. This study proposes a simple, cost-effective ‘genome-wide locus sequence typing’ (GLST) tool based on massive parallel amplification of information hotspots throughout the target pathogen genome. The multiplexed polymerase chain reaction amplifies hundreds of different, user-defined genetic targets in a single reaction tube, and subsequent agarose gel-based clean-up and barcoding completes library preparation at under 4 USD per sample. Our study generates a flexible GLST primer panel design workflow for Trypanosoma cruzi, the parasitic agent of Chagas disease. We successfully apply our 203-target GLST panel to direct, culture-free metagenomic extracts from triatomine vectors containing a minimum of 3.69 pg/μl T. cruzi DNA and further elaborate on method performance by sequencing GLST libraries from T. cruzi reference clones representing discrete typing units (DTUs) TcI, TcIII, TcIV, TcV and TcVI. The 780 SNP sites we identify in the sample set repeatably distinguish parasites infecting sympatric vectors and detect correlations between genetic and geographic distances at regional (< 150 km) as well as continental scales. The markers also clearly separate TcI, TcIII, TcIV and TcV + TcVI and appear to distinguish multiclonal infections within TcI. We discuss the advantages, limitations and prospects of our method across a spectrum of epidemiological research. 相似文献
12.
Cielo M León Carolina Hernández Marleny Montilla Juan David Ramírez 《Memórias do Instituto Oswaldo Cruz》2015,110(3):387-393
Trypanosoma cruzi is the aetiological agent of Chagas disease, which
affects approximately eight million people in the Americas. This parasite exhibits
genetic variability, with at least six discrete typing units broadly distributed in
the American continent. T. cruzi I (TcI) shows remarkable genetic
diversity; a genotype linked to human infections and a domestic cycle of transmission
have recently been identified, hence, this strain was named TcIDom. The aim of this
work was to describe the spatiotemporal distribution of TcI subpopulations across
humans, insect vectors and mammalian reservoirs in Colombia by means of molecular
typing targeting the spliced leader intergenic region of mini-exon gene. We analysed
101 TcI isolates and observed a distribution of sylvatic TcI in 70% and TcIDom in
30%. In humans, the ratio was sylvatic TcI in 60% and TcIDom in 40%. In mammal
reservoirs, the distribution corresponded to sylvatic TcI in 96% and TcIDom in 4%.
Among insect vectors, sylvatic TcI was observed in 48% and TcIDom in 52%. In
conclusion, the circulation of TcIDom is emerging in Colombia and this genotype is
still adapting to the domestic cycle of transmission. The epidemiological and
clinical implications of these findings are discussed herein. 相似文献
13.
Cristiane Varella Lisboa Rafael Veríssimo Monteiro Andreia Fonseca Martins Samantha Cristina das Chagas Xavier Valdirene dos Santos Lima Ana Maria Jansen 《Memórias do Instituto Oswaldo Cruz》2015,110(3):394-402
Here, we present a review of the dataset resulting from the 11-years follow-up of
Trypanosoma cruzi infection in free-ranging populations of
Leontopithecus rosalia (golden lion tamarin) and
Leontopithecus chrysomelas (golden-headed lion tamarin) from
distinct forest fragments in Atlantic Coastal Rainforest. Additionally, we present
new data regarding T. cruzi infection of small mammals (rodents and
marsupials) that live in the same areas as golden lion tamarins and characterisation
at discrete typing unit (DTU) level of 77 of these isolates. DTU TcII was found to
exclusively infect primates, while TcI infected Didelphis aurita and
lion tamarins. The majority of T. cruzi isolates derived from
L. rosalia were shown to be TcII (33 out 42) Nine T.
cruzi isolates displayed a TcI profile. Golden-headed lion tamarins
demonstrated to be excellent reservoirs of TcII, as 24 of 26 T.
cruzi isolates exhibited the TcII profile. We concluded the following:
(i) the transmission cycle of T. cruzi in a same host species and
forest fragment is modified over time, (ii) the infectivity competence of the golden
lion tamarin population fluctuates in waves that peak every other year and (iii) both
golden and golden-headed lion tamarins are able to maintain long-lasting infections
by TcII and TcI. 相似文献
14.
Jo?o Luís Reis-Cunha Tiago Ant?nio de Oliveira Mendes Rodrigo de Almeida Lourdes Daihana Rodrigues dos Santos Ribeiro Ricardo Andrez Machado-de-Avila Maykon de Oliveira Tavares Denise Silveira Lemos Ant?nia Cláudia Jácome Camara Carlos Chavez Olórtegui Marta de Lana Lúcia Maria da Cunha Galv?o Ricardo Toshio Fujiwara Daniella Castanheira Bartholomeu 《PloS one》2014,9(9)
The protozoan Trypanosoma cruzi is the etiologic agent of Chagas disease, an infection that afflicts approximately 8 million people in Latin America. Diagnosis of chronic Chagas disease is currently based on serological tests because this condition is usually characterized by high anti-T. cruzi IgG titers and low parasitemia. The antigens used in these assays may have low specificity due to cross reactivity with antigens from related parasite infections, such as leishmaniasis, and low sensitivity caused by the high polymorphism among T. cruzi strains. Therefore, the identification of new T. cruzi-specific antigens that are conserved among the various parasite discrete typing units (DTUs) is still required. In the present study, we have explored the hybrid nature of the T. cruzi CL Brener strain using a broad genome screening approach to select new T. cruzi antigens that are conserved among the different parasite DTUs and that are absent in other trypanosomatid species. Peptide arrays containing the conserved antigens with the highest epitope prediction scores were synthesized, and the reactivity of the peptides were tested by immunoblot using sera from C57BL/6 mice chronically infected with T. cruzi strains from the TcI, TcII or TcVI DTU. The two T. cruzi proteins that contained the most promising peptides were expressed as recombinant proteins and tested in ELISA experiments with sera from chagasic patients with distinct clinical manifestations: those infected with T. cruzi from different DTUs and those with cutaneous or visceral leishmaniasis. These proteins, named rTc_11623.20 and rTc_N_10421.310, exhibited 94.83 and 89.66% sensitivity, 98.2 and 94.6% specificity, respectively, and a pool of these 2 proteins exhibited 96.55% sensitivity and 98.18% specificity. This work led to the identification of two new antigens with great potential application in the diagnosis of chronic Chagas disease. 相似文献
15.
Chagas disease is an enzootic disease, in which the flagellate Trypanosoma cruzi infects a large variety of animals. Humans are accidentally infected due to the migration into wild environments. To identify T. cruzi discrete typing units (DTUs), 19 Brazilian isolates from different biomes and hosts were analyzed by PCR amplification of 24Sα rRNA, 18S rRNA and mini-exon gene sequences. The majority of the isolates was classified as TcIIb (TcII) but subtypes TcIIc (TcIII) and TcIId (TcV) were also identified. In addition, in monkeys TcI was detected. 相似文献
16.
Several different models of Trypanosoma cruzi evolution have been proposed. These
models suggest that scarce events of genetic exchange occurred during the
evolutionary history of this parasite. In addition, the debate has focused on the
existence of one or two hybridisation events during the evolution of T. cruzi
lineages. Here, we reviewed the literature and analysed available sequence data to
clarify the phylogenetic relationships among these different lineages. We observed
that TcI, TcIII and TcIV form a monophyletic group and that TcIII and TcIV are not,
as previously suggested, TcI-TcII hybrids. Particularly, TcI and TcIII are sister
groups that diverged around the same time that a widely distributed TcIV split into
two clades (TcIVS and TcIVN). In addition, we collected
evidence that TcIII received TcIVS kDNA by introgression on several
occasions. Different demographic hypotheses (surfing and asymmetrical introgression)
may explain the origin and expansion of the TcIII group. Considering these
hypotheses, genetic exchange should have been relatively frequent between TcIII and
TcIVS in the geographic area in which their distributions overlapped.
In addition, our results support the hypothesis that two independent hybridisation
events gave rise to TcV and TcVI. Consequently, TcIVS kDNA was first
transferred to TcIII and later to TcV and TcVI in TcII/TcIII hybridisation
events. 相似文献
17.
Vanessa Lima-Neiva Helena Keiko Toma Lúcia Maria Abrantes Aguiar Catarina Macedo Lopes Letícia Paschoaletto Dias Teresa Cristina Monte Gonalves Jane Costa 《PLoS neglected tropical diseases》2021,15(11)
An outbreak of Chagas disease, possibly involving its vector Triatoma brasiliensis brasiliensis, was identified in the state of Rio Grande do Norte (RN). Given the historical significance of this vector in public health, the study aimed to evaluate its role in the transmission dynamics of the protozoan Trypanosoma cruzi in an area undergoing desertification in the Seridó region, RN, Brazil. We captured triatomines in sylvatic and anthropic ecotopes. Natural vector infection was determined using parasitological and molecular methods and we identified discrete typing units (DTUs) of T. cruzi by analyzing the COII gene of mtDNA, 24Sα rDNA, and mini-exon gene. Their blood meals sources were identified by amplification and sequencing of the mtDNA cytochrome b gene. A total of 952 T. b. brasiliensis were captured in peridomestic (69.9%) and sylvatic ecotopes (30.4%). A wide range of natural infection rates were observed in peridomestic (36.0% - 71.1%) and sylvatic populations (28.6% - 100.0%). We observed the circulation of TcI and TcII DTUs with a predominance of Tcl in sylvatic and peridomestic environments. Kerodon rupestris, rocky cavy (13/39), Homo sapiens, human (8/39), and Bos taurus, ox (6/39) were the most frequently detected blood meals sources. Thus, Triatoma b. brasiliensis is invading and colonizing the human dwellings. Furthermore, high levels of natural infection, coupled with the detection of TcI and TcII DTUs, and also the detection of K. rupestris and H. sapiens as blood meals sources of infected T. b. brasiliensis indicate a risk of T. cruzi transmission to human populations in areas undergoing desertification. 相似文献
18.
Martin S. Llewellyn Michael D. Lewis Nidia Acosta Matthew Yeo Hernan J. Carrasco Maikell Segovia Jorge Vargas Faustino Torrico Michael A. Miles Michael W. Gaunt 《PLoS neglected tropical diseases》2009,3(9)
Trypanosoma cruzi, the etiological agent of Chagas disease, is highly genetically diverse. Numerous lines of evidence point to the existence of six stable genetic lineages or DTUs: TcI, TcIIa, TcIIb, TcIIc, TcIId, and TcIIe. Molecular dating suggests that T. cruzi is likely to have been an endemic infection of neotropical mammalian fauna for many millions of years. Here we have applied a panel of 49 polymorphic microsatellite markers developed from the online T. cruzi genome to document genetic diversity among 53 isolates belonging to TcIIc, a lineage so far recorded almost exclusively in silvatic transmission cycles but increasingly a potential source of human infection. These data are complemented by parallel analysis of sequence variation in a fragment of the glucose-6-phosphate isomerase gene. New isolates confirm that TcIIc is associated with terrestrial transmission cycles and armadillo reservoir hosts, and demonstrate that TcIIc is far more widespread than previously thought, with a distribution at least from Western Venezuela to the Argentine Chaco. We show that TcIIc is truly a discrete T. cruzi lineage, that it could have an ancient origin and that diversity occurs within the terrestrial niche independently of the host species. We also show that spatial structure among TcIIc isolates from its principal host, the armadillo Dasypus novemcinctus, is greater than that among TcI from Didelphis spp. opossums and link this observation to differences in ecology of their respective niches. Homozygosity in TcIIc populations and some linkage indices indicate the possibility of recombination but cannot yet be effectively discriminated from a high genome-wide frequency of gene conversion. Finally, we suggest that the derived TcIIc population genetic data have a vital role in determining the origin of the epidemiologically important hybrid lineages TcIId and TcIIe. 相似文献
19.
Yeo M Mauricio IL Messenger LA Lewis MD Llewellyn MS Acosta N Bhattacharyya T Diosque P Carrasco HJ Miles MA 《PLoS neglected tropical diseases》2011,5(6):e1049
Background
Multilocus sequence typing (MLST) is a powerful and highly discriminatory method for analysing pathogen population structure and epidemiology. Trypanosoma cruzi, the protozoan agent of American trypanosomiasis (Chagas disease), has remarkable genetic and ecological diversity. A standardised MLST protocol that is suitable for assignment of T. cruzi isolates to genetic lineage and for higher resolution diversity studies has not been developed.Methodology/Principal Findings
We have sequenced and diplotyped nine single copy housekeeping genes and assessed their value as part of a systematic MLST scheme for T. cruzi. A minimum panel of four MLST targets (Met-III, RB19, TcGPXII, and DHFR-TS) was shown to provide unambiguous assignment of isolates to the six known T. cruzi lineages (Discrete Typing Units, DTUs TcI-TcVI). In addition, we recommend six MLST targets (Met-II, Met-III, RB19, TcMPX, DHFR-TS, and TR) for more in depth diversity studies on the basis that diploid sequence typing (DST) with this expanded panel distinguished 38 out of 39 reference isolates. Phylogenetic analysis implies a subdivision between North and South American TcIV isolates. Single Nucleotide Polymorphism (SNP) data revealed high levels of heterozygosity among DTUs TcI, TcIII, TcIV and, for three targets, putative corresponding homozygous and heterozygous loci within DTUs TcI and TcIII. Furthermore, individual gene trees gave incongruent topologies at inter- and intra-DTU levels, inconsistent with a model of strict clonality.Conclusions/Significance
We demonstrate the value of systematic MLST diplotyping for describing inter-DTU relationships and for higher resolution diversity studies of T. cruzi, including presence of recombination events. The high levels of heterozygosity will facilitate future population genetics analysis based on MLST haplotypes. 相似文献20.
WM Monteiro LK Magalhães AR de Sá ML Gomes MJ Toledo L Borges I Pires JA de Oliveira Guerra H Silveira Md Barbosa 《PloS one》2012,7(7):e41284