Trypanosoma cruzi (kinetoplastida Trypanosomatidae): biological heterogeneity in the isolates derived from wild hosts

New insights into Trypanosoma cruzi genetic diversity, and its influence on parasite biology and clinical outcomes

Chagas disease, caused by Trypanosoma cruzi, remains a serious public health problem worldwide. The parasite was subdivided into six distinct genetic groups, called "discrete typing units" (DTUs), from TcI to TcVI. Several studies have indicated that the heterogeneity of T. cruzi species directly affects the diversity of clinical manifestations of Chagas disease, control, diagnosis performance, and susceptibility to treatment. Thus, this review aims to describe how T. cruzi genetic diversity influences the biology of the parasite and/or clinical parameters in humans. Regarding the geographic dispersion of T. cruzi, evident differences were observed in the distribution of DTUs in distinct areas. For example, TcII is the main DTU detected in Brazilian patients from the central and southeastern regions, where there are also registers of TcVI as a secondary T. cruzi DTU. An important aspect observed in previous studies is that the genetic variability of T. cruzi can impact parasite infectivity, reproduction, and differentiation in the vectors. It has been proposed that T. cruzi DTU influences the host immune response and affects disease progression. Genetic aspects of the parasite play an important role in determining which host tissues will be infected, thus heavily influencing Chagas disease's pathogenesis. Several teams have investigated the correlation between T. cruzi DTU and the reactivation of Chagas disease. In agreement with these data, it is reasonable to suppose that the immunological condition of the patient, whether or not associated with the reactivation of the T. cruzi infection and the parasite strain, may have an important role in the pathogenesis of Chagas disease. In this context, understanding the genetics of T. cruzi and its biological and clinical implications will provide new knowledge that may contribute to additional strategies in the diagnosis and clinical outcome follow-up of patients with Chagas disease, in addition to the reactivation of immunocompromised patients infected with T. cruzi.

Natural infection with Trypanosoma cruzi in three species of non-human primates in southeastern Mexico: A contribution to reservoir knowledge

The mechanisms of infection and dispersion of Trypanosoma cruzi among animals, especially in the sylvatic environment, are still not entirely clear, and various aspects of the transmission dynamics of this parasite in the sylvatic environment are still unknown. T. cruzi is a parasite with a great biological and genetic diversity that infects a wide variety of hosts, therefore, transmission cycles of this parasite are complex. The objective of this study was to determine the prevalence of T. cruzi infection and analyze the genetic variability of the discrete typing units (DTUs) of the parasite in three non-human primate species (Alouatta palliata, Alouatta pigra, and Ateles geoffroyi) in southeastern Mexico. A total of one hundred sixty-four serum samples (42 samples of A. pigra, 41 samples of A. palliata (free-ranging) and 81 samples of A. geoffroyi (hosted in care centers)) were analyzed for the detection of anti-T. cruzi antibodies by ELISA assays. The seroprevalence of infection was 23.39% in A. palliata, 21.40% in A. pigra and 16.27% in A. geoffroyi. Additionally, presence of parasite DNA was assessed by PCR, and the identification of DTUs was performed by real-time PCR coupled to High Resolution Melting (qPCR-HRM). Different DTUs (TcI, TcII, TcIII, TcV and TcVI) were found in the analyzed monkeys. In addition, infection of monkeys was not associated with age or gender, but it was associated with the species. This study reveals the risk of infection in the study area and that the different DTUs of the parasite can coexist in the same habitat, indicating that T. cruzi transmission in the study area is very complex and involves many ecological factors. However, there is a need for long-term studies of host-parasite interactions to provide a solid understanding of the ecology of these species and to understand the dispersion strategies of T. cruzi.

Trypanosoma cruzi in Triatomines and wild mammals in the National Park of Serra das Confusões, Northeastern Brazil

INTRODUCTION

The National Park of Serra das Confusões (NPSC) is a protected area of natural landscape located in Southern Piauí, Brazil, and it is considered as one of the largest and most important protected areas in the Caatinga biome.

METHODS

The natural occurrences of trypanosomatids from hemocultures on small mammals and cultures from intestinal contents triatomines were detected through molecular diagnoses of blood samples, and phylogenetic relationship analysis of the isolates parasites using the trypanosome barcode (V7V8 SSUrDNA) were realized.

RESULTS

Only two Galea spixii (8.1%) and six Triatoma brasiliensis (17.6%) were positive by hemoculture, and the isolates parasites were cryopreserved. All the isolates obtained were positioned on the Trypanosoma cruzi DTU TcI branch.

CONCLUSIONS

Research focused on studying the wild animal fauna in preserved and underexplored environments has made it possible to elucidate indispensable components of different epidemiological chains of diseases with zoonotic potential.

Trypanosoma cruzi genetic diversity: Something new for something known about Chagas disease manifestations, serodiagnosis and drug sensitivity

The genetic diversity of Trypanosoma cruzi, the protozoan agent of Chagas disease, is widely recognized. At present, T. cruzi is partitioned into seven discrete typing units (DTUs), TcI-TcVI and Tcbat. This article reviews the present knowledge on the parasite population structure, the evolutionary relationships among DTUs and their distinct, but not exclusive ecological and epidemiological associations. Different models for the origin of hybrid DTUs are examined, which agree that genetic exchange among T. cruzi populations is frequent and has contributed to the present parasite population structure. The geographic distribution of the prevalent DTUs in humans from the southern United States to Argentina is here presented and the circumstantial evidence of a possible association between T. cruzi genotype and Chagas disease manifestations is discussed. The available information suggests that parasite strains detected in patients, regardless of the clinical presentation, reflect the principal DTU circulating in the domestic transmission cycles of a particular region. In contrast, in several orally transmitted outbreaks, sylvatic strains are implicated. As a consequence of the genotypic and phenotypic differences of T. cruzi strains and the differential geographic distribution of DTUs in humans, regional variations in the sensitivity of the serological tests are verified. The natural resistance to benznidazole and nifurtimox, verified in vivo and in vitro for some parasite stocks, is not associated with any particular DTU, and does not explain the marked difference in the anti-parasitic efficacy of both drugs in the acute and chronic phases of Chagas disease. Throughout this review, it is emphasized that the interplay between parasite and host genetics should have an important role in the definition of Chagas disease pathogenesis, anti-T. cruzi immune response and chemotherapy outcome and should be considered in future investigations.

Biological and Molecular Characterization of Trypanosoma cruzi Strains from Four States of Brazil

Chagas disease affects between six and seven million people. Its etiological agent, Trypanosoma cruzi, is classified into six discrete typing units (DTUs). The biological study of 11 T. cruzi strains presented here included four parameters: growth kinetics, parasitemia curves, rate of macrophage infection, and serology to evaluate IgM, total IgG, IgG1, IgG2a, and IgG3. Sequencing of small subunit of ribosomal RNA (SSU rRNA)was performed and the T. cruzi strains were classified into three DTUs. When their growth in liver infusion tryptose medium was represented in curves, differences among the strains could be noted. The parasitemia profile varied among the strains from the TcI, TcII, and TcIII groups, and the 11 T. cruzi strains produced distinct parasitemia levels in infected BALB/c. The TcI group presented the highest rate of macrophage infection by amastigotes, followed by TcII and TcIII. Reactivity to immunoglobulins was observed in the TcI, TcII, and TcIII; all the animals infected with the different strains of T. cruzi showed anti-T. cruzi antibodies. The molecular study presented here resulted in the classification of the T. cruzi strains into the TcI (Bolivia, T lenti, Tm, SC90); TcII (Famema, SC96, SI8, Y); and TcIII (QMM3, QMM5, SI5) groups. These biological and molecular results from 11 T. cruzi strains clarified the factors involved in the biology of the parasite and its hosts. The collection of triatomine (vector) species, and the study of geographic distribution, as well as biological and molecular characterization of the parasite, will contribute to the reporting and surveillance measures in Brazilian states.

Molecular characterization of trypanosomatid infections in wild howler monkeys (Alouatta caraya) in northeastern Argentina

The transmission of Trypanosoma cruzi by vectors is confined to the Americas, and the infection circulates in at least two broadly defined transmission cycles occurring in domestic and sylvatic habitats. This study sought to detect and characterize infection by T. cruzi and other trypanosomes using PCR strategies in blood samples from free-ranging howler monkeys, Alouatta caraya, in the northeastern Argentina. Blood samples were collected at four sites with variable levels of habitat modification by human activity. PCR was conducted using primers for kinetoplast DNA, satellite DNA and ribosomal DNA of the trypanosomatid parasites. Ribosomal and satellite DNA fragments were sequenced to identify the trypanosomatid species and to characterize the discrete typing units (DTUs) of T. cruzi. Overall, 46% (50/109) of the howlers were positive according to the kDNA-PCR assay, but only 7 of the howlers were positive according to the SatDNA-PCR protocol. We sequenced the amplicons of the satellite DNA obtained from five specimens, and the sequences were 99% and 100% similar to T. cruzi. A sequence typical of DTU T. cruzi I was found in one howler monkey from the "remote" site, while sequences compatible with DTUs II, V, and VI were found in howlers from the "remote", "rural" and "village" sites. We detected 96% positive samples for RibDNA-PCR, 9 of which were sequenced and displayed 99% identity with Trypanosoma minasense, while none showed identity with T. cruzi. The results demonstrated the presence of T. cruzi and a species closely related to T. minasense in blood samples from free-ranging A. caraya, belonging to different T. cruzi DTUs circulating in these howler monkey populations. The results obtained in this study could help evaluate the role of A. caraya as a reservoir of T. cruzi in regions where Chagas disease is hyper-endemic and where the human-wildlife interface is increasing.

Trypanosoma cruzi III causing the indeterminate form of Chagas disease in a semi-arid region of Brazil

OBJECTIVE

Trypanosoma cruzi is subdivided into six discrete typing units (DTUs), TcI-TcVI. The precise identification of each can contribute to tracking wild DTUs that invade the domiciliary environment.

METHODS

Twenty T. cruzi stocks isolated from 16 chagasic patients, two Panstrongylus lutzi, one Galea spixii, and one Euphractus sexcinctus, from different localities in the State of Rio Grande do Norte, Brazil, were characterized by genotyping the 3' region of the 24Sα rRNA gene, the mitochondrial cytochrome oxidase subunit 2 gene, and the spliced leader intergenic region.

RESULTS

TcIII was identified in 18.7% (3/16) of patients from different municipalities, as well as in P. lutzi, G. spixii, and E. sexcinctus, indicating the connection between the sylvatic and domestic cycles in this Brazilian semi-arid region. TcI and TcII were also detected, in 37.5% (6/16) and 43.8% (7/16) of patients, respectively. These DTUs were associated with cardiac, digestive, and indeterminate clinical forms, while TcIII was identified only in patients with the indeterminate form.

CONCLUSIONS

The occurrence of these DTUs reveals important phylogenetic diversity in T. cruzi isolates from humans. TcIII is reported for the first time in northeastern Brazil. These findings appear to indicate an overlap between the sylvatic and domestic transmission cycles of the parasite in this region.

Between a bug and a hard place: Trypanosoma cruzi genetic diversity and the clinical outcomes of Chagas disease

Over the last 30 years, concomitant with successful transnational disease control programs across Latin America, Chagas disease has expanded from a neglected, endemic parasitic infection of the rural poor to an urbanized chronic disease, and now a potentially emergent global health problem. Trypanosoma cruzi infection has a highly variable clinical course, ranging from complete absence of symptoms to severe and often fatal cardiovascular and/or gastrointestinal manifestations. To date, few correlates of clinical disease progression have been identified. Elucidating a putative role for T. cruzi strain diversity in Chagas disease pathogenesis is complicated by the scarcity of parasites in clinical specimens and the limitations of our contemporary genotyping techniques. This article systematically reviews the historical literature, given our current understanding of parasite genetic diversity, to evaluate the evidence for any association between T. cruzi genotype and chronic clinical outcome, risk of congenital transmission or reactivation and orally transmitted outbreaks.

Experimental evidence of biological interactions among different isolates of Trypanosoma cruzi from the Chaco Region

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.

Comparative pathogenicity in Swiss mice of Trypanosoma cruzi IV from northern Brazil and Trypanosoma cruzi II from southern Brazil

The geographical heterogeneity of Chagas disease (ChD) is mainly caused by genetic variability of the etiological agent Trypanosoma cruzi. Our hypothesis was that the pathogenicity for mice may vary with the genetic lineage (or Discrete Typing Unit - DTU) of the parasite. To test this hypothesis, parasitological and histopathological evaluations were performed in mice inoculated with strains belonging to the DTU T. cruzi IV (TcIV) from the State of Amazonas (northern Brazil), or the DTU T. cruzi II (TcII) from the State of Paraná (southern Brazil). Groups of 10 Swiss mice were inoculated with eight strains of TcIV obtained from acute cases (7) from two outbreaks of orally acquired ChD, and from the triatomine Rhodnius robustus (1) from Amazonas; and three strains of TcII obtained from chronic patients in Paraná. We evaluated the pre-patent period, patent period, maximum peak of parasitemia, day of maximum peak of parasitemia, area under the parasitemia curve, inflammatory process, and tissue parasitism in the acute phase. TcIV was less virulent than TcII, and showed significantly (p < 0.005) lower parasitemia levels. Although the levels of tissue parasitism did not differ statistically, mice infected with TcIV displayed significantly (p < 0.001) fewer inflammatory processes than mice infected with TcII. This supported the working hypothesis, since TcIV from Amazonas was less pathogenic than TcII from Paraná; and agreed with the lower severity of human cases of ChD in the Amazon region.

Trypanosoma cruzi I and IV stocks from Brazilian Amazon are divergent in terms of biological and medical properties in mice

Background

In the Brazilian Amazon, clinical and epidemiological frameworks of Chagas disease are very dissimilar in relation to the endemic classical areas of transmission, possibly due to genetic and biological characteristics of the circulating Trypanosoma cruzi stocks. Twenty six T. cruzi stocks from Western Amazon Region attributed to the TcI and TcIV DTUs were comparatively studied in Swiss mice to test the hypothesis that T. cruzi clonal structure has a major impact on its biological and medical properties.

Methodology/Principal Findings

Seventeen parameters were assayed in mice infected with 14 T. cruzi strains belonging to DTU TcI and 11 strains typed as TcIV. In comparison with TcI, TcIV stocks promoted a significantly shorter pre-patent period (p<0.001), a longer patent period (p<0.001), higher values of mean daily parasitemia (p = 0.009) and maximum of parasitemia (p = 0.015), earlier days of maximum parasitemia (p<0.001) and mortality (p = 0.018), higher mortality rates in the acute phase (p = 0.047), higher infectivity rates (p = 0.002), higher positivity in the fresh blood examination (p<0.001), higher positivity in the ELISA at the early chronic phase (p = 0.022), and a higher positivity in the ELISA at the late chronic phase (p = 0.003). On the other hand TcI showed higher values of mortality rates in the early chronic phase (p = 0.014), higher frequency of mice with inflammatory process in any organ (p = 0.005), higher frequency of mice with tissue parasitism in any organ (p = 0.027) and a higher susceptibility to benznidazole (p = 0.002) than TcIV. Survival analysis showing the time elapsed from the day of inoculation to the beginning of the patent period was significantly shorter for TcIV strains and the death episodes triggered following the infection with TcI occurred significantly later in relation to TcIV. The notable exceptions come from positivity in the hemocultures and PCR, for which the results were similar.

Conclusion/Significance

T. cruzi stocks belonging to TcI and TcIV DTUs from Brazilian Amazon are divergent in terms of biological and medical properties in mice.

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi, constituting an important health problem in the American Continent. In the Brazilian Amazon, Chagas disease has been recognized as an emerging problem. There are few studies exploring the genetic and biological framework of stocks of T. cruzi from the Western Brazilian Amazon, where Chagas disease has a profile of lower morbidity and mortality, appearing mainly in the chronic latent form. Here, we carried out the biological characterization in mice of T. cruzi isolates belonging to TcI and TcIV DTUs from the State of Amazonas, Western Brazilian Amazon. T. cruzi stocks belonging to TcI and TcIV DTUs from Brazilian Amazon are divergent in terms of biological and medical properties in mice, with a higher virulence for the latter DTU as revealed by several biological parameters. Results strongly support the working hypothesis that biological differences are proportional to the evolutionary divergence among the DTUs, and highlight the need to take into account the phylogenetic diversity of T. cruzi natural stocks circulating in the emergent areas for Chagas disease in all applied studies dealing with clinical diversity of Chagas disease, immunology, diagnosis, prognosis, and drug and vaccine trials.

Genetic variation and exchange in Trypanosoma cruzi isolates from the United States

Trypanosoma cruzi, the causative agent of Chagas disease, is a multiclonal parasite with high levels of genetic diversity and broad host and geographic ranges. Molecular characterization of South American isolates of T. cruzi has demonstrated homologous recombination and nuclear hybridization, as well as the presence of 6 main genetic clusters or "discrete typing units" (DTUs). Few studies have extensively investigated such exchange events and genetic diversity in North American isolates. In the current study, we genetically characterized over 50 US isolates from wildlife reservoirs (e.g., raccoons, opossums, armadillos, skunks), domestic dogs, humans, nonhuman primates, and reduviid vectors from nine states (TX, CA, OK, SC, FL, GA, MD, LA, TN) using a multilocus sequencing method. Single nucleotide polymorphisms were identified in sequences of the mismatch-repair class 2 (MSH2) and Tc52 genes. Typing based on the two genes often paralleled genotyping by classic methodologies using mini-exon and 18S and 24Sα rRNA genes. Evidence for genetic exchange was obtained by comparing sequence phylogenies of nuclear and mitochondrial gene targets, dihydrofolate reductase-thymidylate synthase (DHFR-TS) and the cytochrome oxidase subunit II- NADH dehydrogenase subunit I region (COII-ND1), respectively. We observed genetic exchange in several US isolates as demonstrated by incongruent mitochondrial and nuclear genes phylogenies, which confirms a previous finding of a single genetic exchange event in a Florida isolate. The presence of SNPs and evidence of genetic exchange illustrates that strains from the US are genetically diverse, even though only two phylogenetic lineages have been identified in this region.

Biological behavior of Trypanosoma cruzi stocks obtained from the State of Amazonas, Western Brazilian Amazon, in mice

INTRODUCTION

The biological diversity of circulating Trypanosoma cruzi stocks in the Amazon region most likely plays an important role in the peculiar clinic-epidemiological features of Chagas disease in this area.

METHODS

Seven stocks of T. cruzi were recently isolated in the State of Amazonas, Brazil, from humans, wild mammals, and triatomines. They belonged to the TcI and Z3 genotypes and were biologically characterized in Swiss mice. Parasitological and histopathological parameters were determined.

RESULTS

Four stocks did not promote patent parasitemia in mice. Three stocks produced low parasitemia, long pre-patent periods, and a patent period of 1 day or oscillating parasitemia. Maximum parasitemia ranged from 1,400 to 2,800 trypomastigotes/0.1 mL blood. Mice inoculated with the T. cruzi stocks studied showed low positivity during fresh blood examinations, ranging from 0% to 28.6%. In hemoculture, positivity ranged from 0% to 100%. Heart tissue parasitism was observed in mice inoculated with stocks AM49 and AM61. Stock AM49 triggered a moderate inflammatory process in heart tissue. A mild inflammatory process was observed in heart tissue for stocks AM28, AM38, AM61, and AM69. An inflammatory process was frequently observed in skeletal muscle. Examinations of brain tissue revealed inflammatory foci and gliosis in mice inoculated with stock AM49.

CONCLUSIONS

Biological and histopathological characterization allowed us to demonstrate the low infectivity and virulence of T. cruzi stocks isolated from the State of Amazonas.

Biological behavior of different Trypanosoma cruzi isolates circulating in an endemic area for Chagas disease in the Gran Chaco region of Argentina

The biological behavior of the different Trypanosoma cruzi strains is still unclear and the importance of exploring the relevance of these differences in natural isolates is of great significance. Herein we describe the biological behavior of four T. cruzi isolates circulating sympatrically in a restricted geographic area in Argentina endemic for Chagas Disease. These isolates were characterized as belonging to the Discrete Typing Units (DTUs) TcI, TcIII, TcV and TcVI as shown by Multilocus Enzyme Electrophoresis and Multilocus Sequence Typing. In order to study the natural behavior of the different isolates and to preserve their natural properties, we developed a vector transmission model that allows their maintenance in the laboratory. The model consisted of serial passages of these parasites between insect vectors and mice. Vector-derived parasite forms were then inoculated in C57BL/6J mice and number of parasite in peripheral blood, serological response and histological damage in acute and chronic phases of the infection were measured. Parasites from DTUs TcI, TcIII and TcVI were detected by direct fresh blood examination, while TcV parasites could only be detected by Polimerase Chain Reaction. No significant difference in the anti-T. cruzi antibody response was found during the chronic phase of infection, except for mice infected with TcV parasites where no antibodies could be detected. Histological sections showed that TcI isolate produced more damage in skeletal muscle while TcVI induced more inflammation in the heart. This work shows differential biological behavior among different parasite isolates obtained from the same cycle of transmission, permitting the opportunity to formulate future hypotheses of clinical and epidemiological importance.

Biological behaviour in mice of Trypanosoma cruzi isolates from Amazonas and Paraná, Brazil

The biological behaviour of 23 Trypanosoma cruzi isolates in Swiss mice was compared. Nineteen isolates were obtained from patients in the acute phase of Chagas disease (13), sylvatic reservoir hosts (Didelphis marsupialis) (3), and triatomine bugs (Rhodnius robustus) (3) from four regions of the State of Amazonas (AM). Four isolates were obtained from chronic chagasic patients in the State of Paraná (PR): three autochthones, and one allochthone from the State of Minas Gerais. Only one isolate was unable to infect the mice. The AM and PR isolates showed the largest number of significant differences from each other. The former had lower mean values in the pre-patent (5.4 days) and patent (4.6 days) periods (PP), with the parasitaemia (Pmax) reaching a peak of 9.9×10(4) blood trypomastigotes (BT)/mL of blood by the 7th day following inoculation. The AM isolates also had higher positivity to fresh-blood examination (FBE) (84.1%) compared to haemoculture (HC) (58.7%) and polymerase chain reaction (PCR) (33.3%), in addition to higher mortality (2.9%). The PR isolates had higher values for PP (18.5 days) and Pmax (99.9×10(4)BT/mL) as well as higher positivity to FBE (87.2%), HC (100%), and PCR (83.3%). The correlations between the biological behaviour of the T. cruzi isolates and the clinical and epidemiological characteristics of Chagas disease are discussed.

The revised Trypanosoma cruzi subspecific nomenclature: rationale, epidemiological relevance and research applications

The protozoan Trypanosoma cruzi, its mammalian reservoirs, and vectors have existed in nature for millions of years. The human infection, named Chagas disease, is a major public health problem for Latin America. T. cruzi is genetically highly diverse and the understanding of the population structure of this parasite is critical because of the links to transmission cycles and disease. At present, T. cruzi is partitioned into six discrete typing units (DTUs), TcI-TcVI. Here we focus on the current status of taxonomy-related areas such as population structure, phylogeographical and eco-epidemiological features, and the correlation of DTU with natural and experimental infection. We also summarize methods for DTU genotyping, available for widespread use in endemic areas. For the immediate future multilocus sequence typing is likely to be the gold standard for population studies. We conclude that greater advances in our knowledge on pathogenic and epidemiological features of these parasites are expected in the coming decade through the comparative analysis of the genomes from isolates of various DTUs.

Molecular characterization of Trypanosoma cruzi Mexican strains and their behavior in the mouse experimental model

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% 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.

Infectivity, pathogenicity, and virulence of Trypanosoma cruzi Isolates from sylvatic animals and vectors, and domestic dogs from the United States in ICR strain mice and SD strain rats

Trypanosoma cruzi, the causative agent of Chagas disease, is widespread in the southern United States. In addition to detection in numerous wildlife host species, cases have been diagnosed in domestic dogs and humans. In the current investigation, groups of laboratory mice [Crl:CD1 (ICR)] were inoculated with one of 18 United States T. cruzi isolates obtained from a wide host range to elucidate their infectivity, pathogenicity, and virulence. In addition, laboratory rats (SD strain) were inoculated with four isolates. Mice and rats were susceptible to infection with all strains, but no morbidity or mortality was noted, which indicates that these T. cruzi isolates from the United States had low virulence for laboratory mice and rats.

Genetically different isolates of Trypanosoma cruzi elicit different infection dynamics in raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana)

Trypanosoma cruzi is a genetically and biologically diverse species. In the current study we determined T. cruzi infection dynamics in two common North American reservoirs, Virginia opossums (Didelphis virginiana) and raccoons (Procyon lotor). Based on previous molecular and culture data from naturally-exposed animals, we hypothesised that raccoons would have a longer patent period than opossums, and raccoons would be competent reservoirs for both genotypes T. cruzi I (TcI) and TcIIa, while opossums would only serve as hosts for TcI. Individuals (n=2 or 3) of each species were inoculated with 1x10(6) culture-derived T. cruzi trypomastigotes of TcIIa (North American (NA) - raccoon), TcI (NA - opossum), TcIIb (South American - human), or both TcI and TcIIa. Parasitemias in opossums gradually increased and declined rapidly, whereas parasitemias peaked sooner in raccoons and they maintained relatively high parasitemia for 5weeks. Raccoons became infected with all three T. cruzi strains, while opossums only became infected with TcI and TcIIb. Although opossums were susceptible to TcIIb, infection dynamics were dramatically different compared with TcI. Opossums inoculated with TcIIb seroconverted, but parasitemia duration was short and only detectable by PCR. In addition, raccoons seroconverted sooner (3-7days post inoculation) than opossums (10days post inoculation). These data suggest that infection dynamics of various T. cruzi strains can differ considerably in different wildlife hosts.

Infection rates and genotypes of Trypanosoma rangeli and T. cruzi infecting free-ranging Saguinus bicolor (Callitrichidae), a critically endangered primate of the Amazon Rainforest

Parasites of wild primates are important for conservation biology and human health due to their high potential to infect humans. In the Amazon region, non-human primates are commonly infected by Trypanosoma cruzi and T. rangeli, which are also infective to man and several mammals. This is the first survey of trypanosomiasis in a critically endangered species of tamarin, Saguinus bicolor (Callitrichidae), from the Brazilian Amazon Rainforest. Of the 96 free-ranging specimens of S. bicolor examined 45 (46.8%) yielded blood smears positive for trypanosomes. T. rangeli was detected in blood smears of 38 monkeys (39.6%) whereas T. cruzi was never detected. Seven animals (7.3%) presented trypanosomes of the subgenus Megatrypanum. Hemocultures detected 84 positive tamarins (87.5%). Seventy-two of 84 (85.7%) were morphologically diagnosed as T. rangeli and 3 (3.1%) as T. cruzi. Nine tamarins (9.4%) yielded mixed cultures of these two species, which after successive passages generated six cultures exclusively of T. cruzi and two of T. rangeli, with only one culture remaining mixed. Of the 72 cultures positive for T. rangeli, 62 remained as established cultures and were genotyped: 8 were assigned to phylogenetic lineage A (12.9%) and 54 to lineage B (87.1%). Ten established cultures of T. cruzi were genotyped as TCI lineage (100%). Transmission of both trypanosome species, their potential risk to this endangered species and the role of wild primates as reservoirs for trypanosomes infective to humans are discussed.

Protease expression analysis in recently field-isolated strains ofTrypanosoma cruzi: a heterogeneous profile of cysteine protease activities between TC I and TC II major phylogenetic groups

Protease expression among TCI and TCII field isolates was analysed. Gelatin-containing gels revealed hydrolysis bands with molecular masses ranging from 45 to 66 kDa. The general protease expression profile showed that TCII isolates presented higher heterogeneity compared to TCI. By utilizing protease inhibitors, we showed that all active proteases at acid pH are cysteine-proteases and all proteases active at alkaline pH are metalloproteases. However, the expression of cruzipain, theT. cruzimajor cysteine-protease, did not reproduce a heterogeneous TCII cysteine zymogram profile. Dendogram analyses based on presence/absence matrices of proteases and cruzipain bands showed a TCI separation from the TCII group with 50–60% similarity. We suggest that the observed cysteine protease diversification contributes to differential host infection between TCI and II genotypes.

Trypanosoma cruzi (Kinetoplastida, Trypanosomatidae) genotypes in neotropical bats in Brazil

Few studies have been conducted to investigate the role played by the order Chiroptera in the sylvatic transmission cycle of Trypanosoma cruzi or their putative association with the main genotypes of the parasite. Here, the purpose was to enlarge the knowledge of this issue, in this sense, 93 specimens of bats included in 4 families, respectively Molossidae, Noctilionidae, Phyllostomidae and Vespertilionidae collected in distinct regions of Brazil were submitted to fresh blood smears and hemocultures. No patent parasitemia was observed but positive hemocultures by T. cruzi were observed in 14% (13/93) of examined samples. The majority of the parasite isolates were obtained from Phyllostomus hastatus (80%) captured in one same buriti hollow palm tree in the Cerrado region. Multilocus enzyme electrophoresis (MLEE) analyses showed that the genetic distance among these isolates was 0.35, almost the same observed when all the isolates (excluding the reference strains) were analyzed (0.40). No correlation of zymodeme with bat genera, species or geographic region of its origin could be observed, moreover, correlation of zymodeme and genotype of the parasite was not strict. Ten out of 14 T. cruzi isolates obtained from bats corresponded to the TCII genotype. Chiropterans with TCI, TCII/TCIII mixed infection as well as Trypanosoma rangeli in single or mixed infections were observed. These results show that bats may harbor and are probably important maintainers of the main genotypes (TCI, TCII, TCIII/Z3) of T. cruzi. These results support the absence of an association of TCII with any mammal order and show that bats, mainly P. hastatus, may act as amplifier hosts of TCII subpopulations of T. cruzi.