Implications of genetic variability of Trypanosoma cruzi for the pathogenesis of Chagas disease

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.

Chagas Disease: A Silent Threat for Dogs and Humans

Chagas disease (CD) is a vector-borne Neglected Zoonotic Disease (NZD) caused by a flagellate protozoan, Trypanosoma cruzi, that affects various mammalian species across America, including humans and domestic animals. However, due to an increase in population movements and new routes of transmission, T. cruzi infection is presently considered a worldwide health concern, no longer restricted to endemic countries. Dogs play a major role in the domestic cycle by acting very efficiently as reservoirs and allowing the perpetuation of parasite transmission in endemic areas. Despite the significant progress made in recent years, still there is no vaccine against human and animal disease, there are few drugs available for the treatment of human CD, and there is no standard protocol for the treatment of canine CD. In this review, we highlight human and canine Chagas Disease in its different dimensions and interconnections. Dogs, which are considered to be the most important peridomestic reservoir and sentinel for the transmission of T. cruzi infection in a community, develop CD that is clinically similar to human CD. Therefore, an integrative approach, based on the One Health concept, bringing together the advances in genomics, immunology, and epidemiology can lead to the effective development of vaccines, new treatments, and innovative control strategies to tackle CD.

A phased genome assembly of a Colombian Trypanosoma cruzi TcI strain and the evolution of gene families

Chagas is an endemic disease in tropical regions of Latin America, caused by the parasite Trypanosoma cruzi. High intraspecies variability and genome complexity have been challenges to assemble high quality genomes needed for studies in evolution, population genomics, diagnosis and drug development. Here we present a chromosome-level phased assembly of a TcI T. cruzi strain (Dm25). While 29 chromosomes show a large collinearity with the assembly of the Brazil A4 strain, three chromosomes show both large heterozygosity and large divergence, compared to previous assemblies of TcI T. cruzi strains. Nucleotide and protein evolution statistics indicate that T. cruzi Marinkellei separated before the diversification of T. cruzi in the known DTUs. Interchromosomal paralogs of dispersed gene families and histones appeared before but at the same time have a more strict purifying selection, compared to other repeat families. Previously unreported large tandem arrays of protein kinases and histones were identified in this assembly. Over one million variants obtained from Illumina reads aligned to the primary assembly clearly separate the main DTUs. We expect that this new assembly will be a valuable resource for further studies on evolution and functional genomics of Trypanosomatids.

A Review on the Immunological Response against Trypanosoma cruzi

Chagas disease is a chronic systemic infection transmitted by Trypanosoma cruzi. Its life cycle consists of different stages in vector insects and host mammals. Trypanosoma cruzi strains cause different clinical manifestations of Chagas disease alongside geographic differences in morbidity and mortality. Natural killer cells provide the cytokine interferon-gamma in the initial phases of T. cruzi infection. Phagocytes secrete cytokines that promote inflammation and activation of other cells involved in defence. Dendritic cells, monocytes and macrophages modulate the adaptive immune response, and B lymphocytes activate an effective humoral immune response to T. cruzi. This review focuses on the main immune mechanisms acting during T. cruzi infection, on the strategies activated by the pathogen against the host cells, on the processes involved in inflammasome and virulence factors and on the new strategies for preventing, controlling and treating this disease.

An induced population of Trypanosoma cruzi epimastigotes more resistant to complement lysis promotes a phenotype with greater differentiation, invasiveness, and release of extracellular vesicles

Introduction

Chagas disease is a neglected tropical disease caused by Trypanosoma cruzi, which uses blood-feeding triatomine bugs as a vector to finally infect mammalian hosts. Upon entering the host, the parasite needs to effectively evade the attack of the complement system and quickly invade cells to guarantee an infection. In order to accomplish this, T. cruzi expresses different molecules on its surface and releases extracellular vesicles (EVs).

Methods

Here, we have selected a population of epimastigotes (a replicative form) from T. cruzi through two rounds of exposure to normal human serum (NHS), to reach 30% survival (2R population). This 2R population was characterized in several aspects and compared to Wild type population.

Results

The 2R population had a favored metacyclogenesis compared with wild-type (WT) parasites. 2R metacyclic trypomastigotes had a two-fold increase in resistance to complementmediated lysis and were at least three times more infective to eukaryotic cells, probably due to a higher GP82 expression in the resistant population. Moreover, we have shown that EVs from resistant parasites can transfer the invasive phenotype to the WT population. In addition, we showed that the virulence phenotype of the selected population remains in the trypomastigote form derived from cell culture, which is more infective and also has a higher rate of release of trypomastigotes from infected cells.

Conclusions

Altogether, these data indicate that it is possible to select parasites after exposure to a particular stress factor and that the phenotype of epimastigotes remained in the infective stage. Importantly, EVs seem to be an important virulence fator increasing mechanism in this context of survival and persistence in the host.

Modulation of STAT-1, STAT-3, and STAT-6 activities in THP-1 derived macrophages infected with two Trypanosoma cruzi strains

Trypanosoma cruzi is the causative protozoan of Chagas’ Disease, a neglected tropical disease that affects 6−7 million people worldwide. Interaction of the parasite with the host immune system is a key factor in disease progression and chronic symptoms. Although the human immune system is capable of controlling the disease, the parasite has numerous evasion mechanisms that aim to maintain intracellular persistence and survival. Due to the pronounced genetic variability of T. cruzi, co-infections or mixed infections with more than one parasite strain have been reported in the literature. The intermodulation in such cases is unclear. This study aimed to evaluate the co-infection of T. cruzi strains G and CL compared to their individual infections in human macrophages derived from THP-1 cells activated by classical or alternative pathways. Flow cytometry analysis demonstrated that trypomastigotes were more infective than extracellular amastigotes (EAs) and that strain G could infect more macrophages than strain CL. Classically activated macrophages showed lower number of infected cells and IL-4-stimulated cells displayed increased CL-infected macrophages. However, co-infection was a rare event. CL EAs decreased the production of reactive oxygen species (ROS), whereas G trypomastigotes displayed increased ROS detection in classically activated cells. Co-infection did not affect ROS production. Monoinfection by strain G or CL mainly induced an anti-inflammatory cytokine profile by decreasing inflammatory cytokines (IFN-γ, TNF-α, IL-1β) and/or increasing IL-4, IL-10, and TGF-β. Co-infection led to a predominant inflammatory milieu, with reduced IL-10 and TGF-β, and/or promotion of IFN-γ and IL-1β release. Infection by strain G reduced activation of intracellular signal transducer and activator of transcription (STAT) factors. In EAs, monoinfections impaired STAT-1 activity and promoted phosphorylation of STAT-3, both changes may prolong cell survival. Coinfected macrophages displayed pronounced activation of all STATs examined. These activations likely promoted parasite persistence and survival of infected cells. The collective results demonstrate that although macrophages respond to both strains, T. cruzi can modulate the intracellular environment, inducing different responses depending on the strain, parasite infective form, and co-infection or monoinfection. The modulation influences parasite persistence and survival of infected cells.

Biological characteristics of the Trypanosoma cruzi Arequipa strain make it a good model for Chagas disease drug discovery

Trypanosoma cruzi, the causative agent of Chagas disease (CD), is a genuine parasite with tremendous genetic diversity and a complex life cycle. Scientists have studied this disease for more than 100 years, and CD drug discovery has been a mainstay due to the absence of an effective treatment. Technical advances in several areas have contributed to a better understanding of the complex biology and life cycle of this parasite, with the aim of designing the ideal profile of both drug and therapeutic options to treat CD. Here, we present the T. cruzi Arequipa strain (MHOM/Pe/2011/Arequipa) as an interesting model for CD drug discovery. We characterized acute-phase parasitaemia and chronic-phase tropism in BALB/c mice and determined the in vitro and in vivo benznidazole susceptibility profile of the different morphological forms of this strain. The tropism of this strain makes it an interesting model for the screening of new compounds with a potential anti-Chagas profile for the treatment of this disease.

Trypanosoma cruzi Mitochondrial Peroxiredoxin Promotes Infectivity in Macrophages and Attenuates Nifurtimox Toxicity

Trypanosoma cruzi is the causative agent of Chagas disease which is currently treated by nifurtimox (NFX) and benznidazole (BZ). Nevertheless, the mechanism of action of NFX is not completely established. Herein, we show the protective effects of T. cruzi mitochondrial peroxiredoxin (MPX) in macrophage infections and in response to NFX toxicity. After a 3-day treatment of epimastigotes with NFX, MPX content increased (2.5-fold) with respect to control, and interestingly, an MPX-overexpressing strain was more resistant to the drug. The generation of mitochondrial reactive species and the redox status of the low molecular weight thiols of the parasite were not affected by NFX treatment indicating the absence of oxidative stress in this condition. Since MPX was shown to be protective and overexpressed in drug-challenged parasites, non-classical peroxiredoxin activity was studied. We found that recombinant MPX exhibits holdase activity independently of its redox state and that its overexpression was also observed in temperature-challenged parasites. Moreover, increased holdase activity (2-fold) together with an augmented protease activity (proteasome-related) and an enhancement in ubiquitinylated proteins was found in NFX-treated parasites. These results suggest a protective role of MPX holdase activity toward NFX toxicity. Trypanosoma cruzi has a complex life cycle, part of which involves the invasion of mammalian cells, where parasite replication inside the host occurs. In the early stages of the infection, macrophages recognize and engulf T. cruzi with the generation of reactive oxygen and nitrogen species toward the internalized parasite. Parasites overexpressing MPX produced higher macrophage infection yield compared with wild-type parasites. The relevance of peroxidase vs. holdase activity of MPX during macrophage infections was assessed using conoidin A (CA), a covalent, cell-permeable inhibitor of peroxiredoxin peroxidase activity. Covalent adducts of MPX were detected in CA-treated parasites, which proves its action in vivo. The pretreatment of parasites with CA led to a reduced infection index in macrophages revealing that the peroxidase activity of peroxiredoxin is crucial during this infection process. Our results confirm the importance of peroxidase activity during macrophage infection and provide insights for the relevance of MPX holdase activity in NFX resistance.

The Complete Mitochondrial DNA of Trypanosoma cruzi: Maxicircles and Minicircles

The mitochondrial DNA of Trypanosomatids, known as the kinetoplast DNA or kDNA or mtDNA, consists of a few maxicircles and thousands of minicircles concatenated together into a huge complex network. These structures present species-specific sizes, from 20 to 40 Kb in maxicircles and from 0.5 to 10 Kb in minicircles. Maxicircles are equivalent to other eukaryotic mitochondrial DNAs, while minicircles contain coding guide RNAs involved in U-insertion/deletion editing processes exclusive of Trypanosomatids that produce the maturation of the maxicircle-encoded transcripts. The knowledge about this mitochondrial genome is especially relevant since the expression of nuclear and mitochondrial genes involved in oxidative phosphorylation must be coordinated. In Trypanosoma cruzi (T. cruzi), the mtDNA has a dual relevance; the production of energy, and its use as a phylogenetic marker due to its high conservation among strains. Therefore, this study aimed to assemble, annotate, and analyze the complete repertoire of maxicircle and minicircle sequences of different T. cruzi strains by using DNA sequencing. We assembled and annotated the complete maxicircle sequence of the Y and Bug2148 strains. For Bug2148, our results confirm that the maxicircle sequence is the longest assembled to date, and is composed of 21 genes, most of them conserved among Trypanosomatid species. In agreement with previous results, T. cruzi minicircles show a conserved structure around 1.4 Kb, with four highly conserved regions and other four hypervariable regions interspersed between them. However, our results suggest that the parasite minicircles display several sizes and numbers of conserved and hypervariable regions, contrary to those previous studies. Besides, this heterogeneity is also reflected in the three conserved sequence blocks of the conserved regions that play a key role in the minicircle replication. Our results using sequencing technologies of second and third-generation indicate that the different consensus sequences of the maxicircles and minicircles seem to be more complex than previously described indicating at least four different groups in T. cruzi minicircles.

The tissue specific tropism in Trypanosoma cruzi. Is it true?

Systematic microscopical observations on tissues from mice, inoculated with different Trypanosoma cruzi isolates, were carried out in order to assess whether the parasite expresses tissue-specific tropism, or if it can invade tissues pervasively within the mammal host. A total of ninety mice were included in the study. Sixty, subcutaneously-inoculated with 15 × 10⁴T. cruzi-blood trypomastigotes were dissected and examined daily for detecting and counting parasites during 12 days of acute infection. Additionally, two long-term experiments using mice inoculated with 5 × 10³ metacyclic-forms were performed. A group of 10 mice inoculated intraperitoneally and another group of 20 mice inoculated intradermally. Results demonstrated that T. cruzi does not exhibit a tissue-specific tropism, revealing characteristics of a paninfective species able to invade tissues of ectodermal, mesodermal, and endodermal embryonic origin, irrespective of the parasite's lineage, infective form, route of entry, or size of the inoculum causing the host's infection. Details on T. cruzi-tissue invasion, tissue-parasite load during the course time, and the hypothetical potential pseudocyst/amastigote whole-body burden in the murine model is analyzed. The importance of the findings and its interpretation related to human Chagas disease and the tissue-parasite persistence is also discussed.

Trypanosoma Cruzi Genome: Organization, Multi-Gene Families, Transcription, and Biological Implications

Chagas disease caused by the parasite Trypanosoma cruzi affects millions of people. Although its first genome dates from 2005, its complexity hindered a complete assembly and annotation. However, the new sequencing methods have improved genome annotation of some strains elucidating the broad genetic diversity and complexity of this parasite. Here, we reviewed the genomic structure and regulation, the genetic diversity, and the analysis of the principal multi-gene families of the recent genomes for several strains. The telomeric and sub-telomeric regions are sites with high recombination events, the genome displays two different compartments, the core and the disruptive, and the genome plasticity seems to play a key role in the survival and the infection process. Trypanosoma cruzi (T. cruzi) genome is composed mainly of multi-gene families as the trans-sialidases, mucins, and mucin-associated surface proteins. Trans-sialidases are the most abundant genes in the genome and show an important role in the effectiveness of the infection and the parasite survival. Mucins and MASPs are also important glycosylated proteins of the surface of the parasite that play a major biological role in both insect and mammal-dwelling stages. Altogether, these studies confirm the complexity of T. cruzi genome revealing relevant concepts to better understand Chagas disease.

Comparative proteomic analysis of trypomastigotes from Trypanosoma cruzi strains with different pathogenicity

Chagas disease, caused by the parasite Trypanosoma cruzi, is one of the most neglected diseases in Latin America, being currently a global health problem. Its immunopathogenesis is still quite unknown. Moreover, there are important differences in pathogenicity between some different T. cruzi strains. For example, in mice, Y strain produces a high acute lethality while VFRA remains in the host mostly in a chronic manner. Comparative proteomic studies between T. cruzi strains represent a complement for transcriptomics and may allow the detection of relevant factors or distinctive functions. Here for the first time, we compared the proteome of trypomastigotes from 2 strains, Y and VFRA, analyzed by mass spectrometry. Gene ontology analysis were used to display similarities or differences in cellular components, biological processes and molecular functions. Also, we performed metabolic pathways enrichment analysis to detect the most relevant pathways in each strain. Although in general they have similar profiles in the different ontology groups, there were some particular interesting differences. Moreover, there were around 10% of different proteins between Y and VFRA strains, that were shared by other T. cruzi strains or protozoan species. They displayed many common enriched metabolic pathways but some others were uniquely enriched in one strain. Thus, we detected enriched antioxidant defenses in VFRA that could correlate with its ability to induce a chronic infection in mice controlling ROS production, while the Y strain revealed a great enrichment of pathways related with nucleotides and protein production, that could fit with its high parasite replication and lethality. In summary, Y and VFRA strains displayed comparable proteomes with some particular distinctions that could contribute to understand their different biological behaviors.

Trypanosoma cruzi: A review of biological and methodological factors in Mexican strains

Trypanosoma cruzi, responsible for Chagas disease, is a serious public health problem in Latin America with eight million people infected in the world. Clinical manifestations observed in humans due to T. cruzi infection are largely associated with the wide biological and genetic heterogeneity of the parasite. This review presents an overview of the parasitological aspects of various strains of T. cruzi isolated mainly in Mexico, as well as an analysis of the methodological processes used to determine their virulence that could be influencing their biological characterization. We emphasize the importance of using uniform protocols to study T. cruzi virulence, taking into account factors related to: strain (i.e. developmental stage, lineage, biological origin, genetic variability), animal model used (i.e. role of hormones, host immune response, age) and methodology (i.e. inoculum size, inoculation route, and laboratory conditions used during strain maintenance). These uniform protocols will then allow proposing elements for understanding clinical evolution and management of the disease, for providing adequate treatment, and for developing tools for future vaccines against Chagas disease.

Pep5, a Fragment of Cyclin D2, Shows Antiparasitic Effects in Different Stages of the Trypanosoma cruzi Life Cycle and Blocks Parasite Infectivity

Pep5 (WELVVLGKL) is a fragment of cyclin D2 that exhibits a 2-fold increase in the S phase of the HeLa cell cycle. When covalently bound to a cell-penetrating peptide (Pep5-cpp), the nonapeptide induces cell death in several tumor cells, including breast cancer and melanoma cells. Additionally, Pep5-cpp reduces the in vivo tumor volume of rat glioblastoma. Chagas disease, which is caused by the flagellated parasite Trypanosoma cruzi, is a neglected disease that occurs mainly in the Americas, where it is considered an important public health issue. Given that there are only two options for treating the disease, it is exceptionally crucial to search for new molecules with potential pharmacological action against the parasites. In this study, we demonstrate that Pep5-cpp induces cell death in epimastigote, trypomastigote, and amastigote forms of T. cruzi The Pep5-cpp peptide was also able to decrease the percentage of infected cells without causing any detectable toxic effects in mammalian host cells. The infective, i.e., trypomastigote form of T. cruzi pretreated with Pep5-cpp was unable to infect LLC-MK₂ monkey kidney cells. Also, Pep5-binding proteins were identified by mass spectrometry, including calmodulin-ubiquitin-associated protein, which is related to the virulence and parasitemia of T. cruzi Taken together, these data suggest that Pep5 can be used as a novel alternative for the treatment of Chagas disease.

Detection of anti-Trypanosoma cruzi antibodies by chimeric antigens in chronic Chagas disease-individuals from endemic South American countries

Background

Laboratory diagnosis of chronic Chagas disease is a troubling factor due to lack of reference tests. The WHO suggests the use of two distinct commercial serological tests in parallel. The performance of commercial immunoassays might fluctuate depending on the antigenic matrices and the local strains of T. cruzi in different geographical settings. The use of antigenic matrices based on chimeric proteins can solve these limitations. Here, we evaluated the diagnostic performance of two chimeric T. cruzi antigens (IBMP-8.1 and -8.4) to diagnose chronic Chagas disease in individuals from endemic South American countries.

Methodology/Principal findings

IBMP-8.1 and IBMP-8.4 chimeric antigens were expressed as soluble proteins in E. coli and purified using chromatography methods. Reactivity of IBMP-8.1 and IBMP-8.4 was assessed using an in-house ELISA with sera from 122 non-infected and 215 T. cruzi-infected individuals from Argentina, Bolivia, and Paraguay. Cut-off values were based on ROC curves and performance parameters were determined using a dichotomous approach. Area under the curve values were > 99.7% for both IBMP-8.1 and IBMP-8.4 antigens. IgG levels in T. cruzi-positive and negative samples were higher for IBMP-8.4 than IBMP-8.1. Both IBMP-8.1 and -8.4 were 100% specific, while IBMP-8.4 were 100% sensitive compared to IBMP-8.1 (95.3%). Admitting RI values of 1.0 ± 0.10 as the inconclusive interval, 6.2% of the samples tested using IBMP-8.1 and 2.1% using IBMP-8.4 fell inside the grey zone. Based on accuracy and diagnostic odds ratio values, IBMP-8.4 presented the best performance. Differences in sensitivity and IgG levels among the samples from Argentina, Bolivia, and Paraguay were not significant.

Conclusions/Significance

Our findings showed a notable performance of IBMP-8.1 and -8.4 chimeric antigens in diagnosing chronic Chagas disease in individuals from endemic South American countries, confirming our hypothesis that these antigens could be used in geographical areas where distinct T. cruzi DTUs occur.

Infection by Trypanosoma cruzi in the central nervous system in non-human mammals: a systematic review

Currently, the types and distribution of the lesions induced in the central nervous system (CNS) by Trypanosoma cruzi remain unclear as the available evidence is based on fragmented data. Therefore, we developed a systematic review to analyse the main characteristics of the CNS lesions in non-human hosts infected. From a structured search on the PubMed/Medline and Scopus platforms, 32 studies were retrieved, subjected to data extraction and methodological bias analysis. Our results show that the most frequent alterations in the CNS are the presence of different forms of T. cruzi and intense lymphocytes infiltrates. The encephalon is the main target of T. cruzi, and inflammatory changes in the CNS are more frequent and severe in the acute phase of infection. The parasite's genotype and phenotype are associated with the tropism and severity of the CNS lesions. The methodological limitations found in the studies were divergences in inoculation pathways, under-reporting of animal age and weight, sample calculation strategies and histopathological characterization. Since the changes were dependent on the pathogenicity and virulence of the T. cruzi strains, the genotype and phenotype characterization of the parasite are extremely relevant to predict changes in the CNS and the neurological manifestations associated with Chagas' disease.

Relevance of Trypanothione Reductase Inhibitors on Trypanosoma cruzi Infection: A Systematic Review, Meta-Analysis, and In Silico Integrated Approach

Due to the rudimentary antioxidant defenses in Trypanosoma cruzi, disruptors of redox balance are promising candidates for new antitrypanosomal drugs. We developed an integrated model based on systematic review, meta-analyses, and molecular modeling to evaluate the effect of trypanothione reductase (TR) inhibitors in T. cruzi infections. Our findings indicated that the TR inhibitors analyzed were effective in reducing parasitemia and mortality due to Trypanosoma cruzi infection in animal models. The most investigated drugs (clomipramine and thioridazine) showed no beneficial effects on the occurrence of infection-related electrocardiographic abnormalities or the affinity and density of cardiac β-adrenergic receptors. The affinity between the tested ligands and the active site of TR was confirmed by molecular docking. However, the molecular affinity score was unable to explain TR inhibition and T. cruzi death in vitro or the antiparasitic potential of these drugs when tested in preclinical models of T. cruzi infection. The divergence of in silico, in vitro, and in vivo findings indicated that the anti-T. cruzi effects of the analyzed drugs were not restricted to TR inhibition. As in vivo studies on TR inhibitors are still scarce and exhibit methodological limitations, mechanistic and highly controlled studies are required to improve the quality of evidence.

Genomic assemblies of newly sequenced Trypanosoma cruzi strains reveal new genomic expansion and greater complexity

Chagas disease is a complex illness caused by the protozoan Trypanosoma cruzi displaying highly diverse clinical outcomes. In this sense, the genome sequence elucidation and comparison between strains may lead to disease understanding. Here, two new T. cruzi strains, have been sequenced, Y using Illumina and Bug2148 using PacBio, assembled, analyzed and compared with the T. cruzi annotated genomes available to date. The assembly stats from the new sequences show effective improvement of T. cruzi genome over the actual ones. Such as, the largest contig assembled (1.3 Mb in Bug2148) in de novo attempts and the highest mean assembly coverage (71X for Y). Our analysis reveals a new genomic expansion and greater complexity for those multi-copy gene families related to infection process and disease development, such as Trans-sialidases, Mucins and Mucin Associated Surface Proteins, among others. On one side, we demonstrate that multi-copy gene families are located near telomeric regions of the "chromosome-like" 1.3 Mb contig assembled of Bug2148, where they likely suffer high evolutive pressure. On the other hand, we identified several strain-specific single copy genes that might help to understand the differences in infectivity and physiology among strains. In summary, our results indicate that T. cruzi has a complex genomic architecture that may have promoted its evolution.

What makes an effective Chagas disease vector? Factors underlying Trypanosoma cruzi-triatomine interactions

The Chagas disease is caused by the parasite Trypanosoma cruzi, which infect blood-feeding triatomine bugs to finally reach mammal hosts. Chagas disease is endemic in Latin America, and is ranked among the 13 neglected tropical diseases worldwide. Currently, an estimate of 7 million people is infected by T. cruzi, leading to about 22 000 deaths per year throughout the Americas. As occurs with other vectors, a major question towards control programs is what makes a susceptible bug. In this review, we focus on findings linked to insect gut structure and microbiota, immunity, genetics, blood sources, abiotic factors (with special reference to ambient temperature and altitude) to understand the interactions occurring between T. cruzi and triatomine bugs, under a co-evolutionary scenario. These factors lead to varying fitness benefits and costs for bugs, explaining why infection in the insect takes place and how it varies in time and space. Our analysis highlights that major factors are gut components and microbiota, blood sources and temperature. Although their close interaction has never been clarified, knowledge reviewed here may help to boost the success of triatomine control programs, reducing the use of insecticides.

Evaluation of parasite and host genetics in two generations of a family with Chagas disease

Chagas disease, caused by the protozoan Trypanosoma cruzi, is considered to be a multifactorial disease associated with host and parasite genetics, which influence clinical aspects of the disease and other host conditions. In order to understand better the evolution of the disease, this study intended to evaluation of parasite and host genetics in two generations of a family with Chagas disease from the Alto Paranaiba region, Minas Gerais, Brazil, comprising a mother and her five daughters. Several features were evaluated, including the characterization of T. cruzi directly from the blood of patients, host polymorphisms of genes related to cardiomyopathy (TNF, WISP1, CCR5, and TGF-β1) and clinical aspects of the patients. To verify the intraspecific variability of the parasite, the characterization was done directly from human blood using the PCR-LSSP technique and analyzed based on Dice coefficient and unweighted pair group analysis (UPGMA). The host polymorphism was evaluated by PCR-RFLP. The global results showed low variability of the parasites characterized from blood of patients, through Shannon index (0.492) and mean heterozygosity value per locus (0.322). All six patients presented the same genetic polymorphism profile for TNF, WISP1, and TGF-β1, and only one patient was homozygous to CCR5, which suggests that there is no association between the clinical aspects of the patients and their genetic profiles. In conclusion, the findings confirm that the understanding of the clinical evolution of Chagas disease goes beyond the genetic aspects of the parasite and the host.

Relationships between altitude, triatomine (Triatoma dimidiata) immune response and virulence of Trypanosoma cruzi, the causal agent of Chagas' disease

Little is known about how the virulence of a human pathogen varies in the environment it shares with its vector. This study focused on whether the virulence of Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae), the causal agent of Chagas' disease, is related to altitude. Accordingly, Triatoma dimidiata (Hemiptera: Reduviidae) specimens were collected at three different altitudes (300, 700 and 1400 m a.s.l.) in Chiapas, Mexico. The parasite was then isolated to infect uninfected T. dimidiata from the same altitudes, as well as female CD-1 mice. The response variables were phenoloxidase (PO) activity, a key insect immune response, parasitaemia in mice, and amastigote numbers in the heart, oesophagus, gastrocnemius and brain of the rodents. The highest levels of PO activity, parasitaemia and amastigotes were found for Tryp. cruzi isolates sourced from 700 m a.s.l., particularly in the mouse brain. A polymerase chain reaction-based analysis indicated that all Tryp. cruzi isolates belonged to a Tryp. cruzi I lineage. Thus, Tryp. cruzi from 700 m a.s.l. may be more dangerous than sources at other altitudes. At this altitude, T. dimidiata is more common, apparently because the conditions are more beneficial to its development. Control strategies should focus activity at altitudes around 700 m a.s.l., at least in relation to the region of the present study sites.

ABO, Secretor and Lewis histo-blood group systems influence the digestive form of Chagas disease

Chagas disease, caused by Trypanosoma cruzi, can affect the heart, esophagus and colon. The reasons that some patients develop different clinical forms or remain asymptomatic are unclear. It is believed that tissue immunogenetic markers influence the tropism of T. cruzi for different organs. ABO, Secretor and Lewis histo-blood group systems express a variety of tissue carbohydrate antigens that influence the susceptibility or resistance to diseases. This study aimed to examine the association of ABO, secretor and Lewis histo-blood systems with the clinical forms of Chagas disease. We enrolled 339 consecutive adult patients with chronic Chagas disease regardless of gender (cardiomyopathy: n=154; megaesophagus: n=119; megacolon: n=66). The control group was composed by 488 healthy blood donors. IgG anti-T. cruzi antibodies were detected by ELISA. ABO and Lewis phenotypes were defined by standard hemagglutination tests. Secretor (FUT2) and Lewis (FUT3) genotypes, determined by Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), were used to infer the correct histo-blood group antigens expressed in the gastrointestinal tract. The proportions between groups were compared using the χ2 test with Yates correction and Fisher's exact test and the Odds Ratio (OR) and 95% Confidence Interval (95% CI) were calculated. An alpha error of 5% was considered significant with p-values <0.05 being corrected for multiple comparisons (pc). No statistically significant differences were found for the ABO (X2: 2.635; p-value=0.451), Secretor (X2: 0.056; p-value=0.812) or Lewis (X2: 2.092; p-value=0.351) histo-blood group phenotypes between patients and controls. However, B plus AB Secretor phenotypes were prevalent in pooled data from megaesophagus and megacolon patients (OR: 5.381; 95% CI: 1.230-23.529; p-value=0.011; pc=0.022) in comparison to A plus O Secretor phenotypes. The tissue antigen variability resulting from the combined action of ABO and Secretor histo-blood systems is associated with the digestive forms of Chagas disease.

Possible Differences in the Effects of Trypanosoma cruzi on Blood Cells and Serum Protein of Two Wildlife Reservoirs

A key step in the dynamics of vector-borne diseases is the role of seasonality. Trypanosoma cruzi is a protozoan that causes Chagas disease. Some wild mammals are considered natural hosts, yet not all mammals show the same response to infection. We explored the effect of T. cruzi on blood parameters in two mammal carnivores, coati (Nasua narica) and raccoon (Procyon lotor), that were naturally infected in summer and winter seasons. The study was carried out in the Zoological Park "Parque Museo de la Venta," in Southeastern Mexico. Blood samples were collected in summer and winter from 2010 to 2013. Parasite infection was assessed by PCR from whole blood, and a complete hemogram was determined by traditional manual methods. We found that both species had the same T. cruzi I lineage. For coatis, mean corpuscular volume, mean corpuscular hemoglobin, and monocytes were dependent of season, while eosinophils and plasma proteins were significantly different, but with no season effect. For raccoon, erythrocytes, mean corpuscular volume, mean corpuscular hemoglobin, and monocytes were dependent of season. These results and a previous study that indicated interspecific differences in parasitemia in both species suggest that raccoon is a better reservoir than coati. Such a different interspecific response implies that animals do not contribute equally to maintain T. cruzi parasites in the ecosystem. Such inequality differs according to season.

Structural analysis and molecular docking of trypanocidal aryloxy-quinones in trypanothione and glutathione reductases: a comparison with biochemical data

A set of aryloxy-quinones, previously synthesized and evaluated against Trypanosoma cruzi epimastigotes cultures, were found more potent and selective than nifurtimox. One of the possible mechanisms of the trypanocidal activity of these quinones could be inhibition of trypanothione reductase (TR). Considering that glutathione reductase (GR) is the equivalent of TR in humans, biochemical, kinetic, and molecular docking studies in TR and GR were envisaged and compared with the trypanocidal and cytotoxic data of a set of aryloxy-quinones. Biochemical assays indicated that three naphthoquinones (Nq-h, Nq-g, and Nq-d) selectively inhibit TR and the TR kinetic analyses indicated that Nq-h inhibit TR in a noncompetitive mechanism. Molecular dockings were performed in TR and GR in the following three putative binding sites: the catalytic site, the dimer interface, and the nicotinamide adenine dinucleotide phosphate-binding site. In TR and GR, the aryloxy-quinones were found to exhibit high affinity for a site near it cognate-binding site in a place in which the noncompetitive kinetics could be justified. Taking as examples the three compounds with TR specificity (TRS) (Nq-h, Nq-g, and Nq-d), the presence of a network of contacts with the quinonic ring sustained by the triad of Lys62, Met400', Ser464' residues, seems to contribute hardly to the TRS. Compound Nq-b, a naphthoquinone with nitrophenoxy substituent, proved to be the best scaffold for the design of trypanocidal compounds with low toxicity. However, the compound displayed only a poor and non-selective effect toward TR indicating that TR inhibition is not the main reason for the antiparasitic activity of the aryloxy-quinones.

Prevalence and Impact of Chagas Disease Among Latin American Immigrants With Nonischemic Cardiomyopathy in Los Angeles, California

Background—

Chagas disease is a well-known cause of cardiomyopathy in Latin America; however, 300 000 individuals are estimated to have Chagas disease in the United States. This study examined the prevalence and impact of Chagas cardiomyopathy (CCM) in a US population. We hypothesized that patients with CCM would have increased morbidity and mortality when compared with patients with non-CCM.

Methods and Results—

This is a single-center, prospective cohort study. Enrollment criteria were new diagnosis of nonischemic cardiomyopathy (left ventricular ejection fraction ≤40%) and previous residence in Latin America for at least 12 months. Serological testing for Trypanosoma cruzi was performed at enrollment. The primary end point was all-cause mortality or heart transplantation. The secondary end point was heart failure–related hospitalization. A total of 135 patients were enrolled, with a median of 43 months of follow-up. Chagas disease was diagnosed in 25 (19%) patients. The primary end point occurred in 9 patients (36%) in the CCM group and in 11 patients (10%) in the non-CCM group (hazard ratio [HR], 4.46; 95% confidence interval, 1.8–10.8; P =0.001). The secondary end point occurred in 13 patients (52%) in the CCM group and in 35 patients (32%) in the non-CCM group (HR, 2.22; 95% confidence interval, 1.2–4.2; P =0.01).

Conclusions—

There is a high prevalence of Chagas disease among Latin American immigrants diagnosed with nonischemic cardiomyopathy in Los Angeles. Advanced CCM portends a poor prognosis and is associated with increased all-cause mortality/heart transplantation and heart failure–related hospitalization.

Translational challenges of animal models in Chagas disease drug development: a review

Chagas disease, or American trypanosomiasis, caused by Trypanosoma cruzi parasite infection is endemic in Latin America and presents an increasing clinical challenge due to migrating populations. Despite being first identified over a century ago, only two drugs are available for its treatment, and recent outcomes from the first clinical trials in 40 years were lackluster. There is a critical need to develop new drugs to treat Chagas disease. This requires a better understanding of the progression of parasite infection, and standardization of animal models designed for Chagas disease drug discovery. Such measures would improve comparison of generated data and the predictability of test hypotheses and models designed for translation to human disease. Existing animal models address both disease pathology and treatment efficacy. Available models have limited predictive value for the preclinical evaluation of novel therapies and need to more confidently predict the efficacy of new drug candidates in clinical trials. This review highlights the overall lack of standardized methodology and assessment tools, which has hampered the development of efficacious compounds to treat Chagas disease. We provide an overview of animal models for Chagas disease, and propose steps that could be undertaken to reduce variability and improve predictability of drug candidate efficacy. New technological developments and tools may contribute to a much needed boost in the drug discovery process.

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.

Killer Cell Immunoglobulin-like Receptors and Their HLA Ligands are Related with the Immunopathology of Chagas Disease

The aim of this study was to investigate the influence of killer cell immunoglobulin-like receptor (KIR) genes and their human leucocyte antigen (HLA) ligands in the susceptibility of chronic Chagas disease. This case-control study enrolled 131 serologically-diagnosed Chagas disease patients (59 men and 72 women, mean age of 60.4 ± 9.8 years) treated at the University Hospital of Londrina and the Chagas Disease Laboratory of the State University of Maringa. A control group was formed of 165 healthy individuals - spouses of patients or blood donors from the Regional Blood Bank in Maringa (84 men and 81 women, with a mean age of 59.0 ± 11.4 years). Genotyping of HLA and KIR was performed by PCR-SSOP. KIR2DS2-C1 in the absence of KIR2DL2 (KIR2DS2⁺/2DL2^-/C1⁺) was more frequent in Chagas patients (P = 0.020; Pc = 0.040; OR = 2.14) and, in particular, those who manifested chronic chagasic cardiopathy—CCC (P = 0.0002; Pc = 0.0004; OR = 6.64; 95% CI = 2.30–18.60) when compared to the control group, and when CCC group was compared to the patients without heart involvement (P = 0.010; Pc = 0.020; OR = 3.97). The combination pair KIR2DS2⁺/2DL2^-/KIR2DL3⁺/C1⁺ was also positively associated with chronic chagasic cardiopathy. KIR2DL2 and KIR2DS2 were related to immunopathogenesis in Chagas disease. The combination of KIR2DS2 activating receptor with C1 ligand, in the absence of KIR2DL2, may be related to a risk factor in the chronic Chagas disease and chronic chagasic cardiopathy.

Chagas disease is an infection caused by the haemoflagellate protozoan Trypanosoma cruzi. It is one of the most important public health problems in Latin America, and was first described by Carlos Justiniano Ribeiro das Chagas, a Brazilian physician and scientist, in 1909. It is mostly vector-borne transmitted to humans by contact with faeces of triatomine bugs. The World Health Organization estimates that about 6 to 7 million people are currently infected with T. cruzi worldwide. The disease is characterised by acute and chronic phases. The immune response during disease development is crucial for protection because immunological imbalances can lead to heart and digestive tract lesions in chagasic patients. In this work we analysed the role of receptors of immune cells known as Natural Killer cells (killer cell immunoglobulin-like receptor—KIR) and their ligands (Human leukocyte antigens—HLA) in chagasic patients compared to healthy individuals. The uncontrolled activation of NK cells can lead to tissue damage, which, in turn, leads to the development of serious chronic illness. We found that KIR-HLA complex may be related to a risk factor in the chronic Chagas disease and chronic chagasic cardiopathy.

Trypanothione reductase inhibitors: Overview of the action of thioridazine in different stages of Chagas disease

Thioridazine (TDZ) is a phenothiazine that has been shown to be one of the most potent phenothiazines to inhibit trypanothione reductase irreversibly. Trypanothione reductase is an essential enzyme for the survival of Trypanosoma cruzi in the host. Here, we reviewed the use of this drug for the treatment of T. cruzi experimental infection. In our laboratory, we have studied the effect of TDZ for the treatment of mice infected with different strains of T. cruzi and treated in the acute or in the chronic phases of the experimental infection, using two different schedules: TDZ at a dose of 80 mg/kg/day, for 3 days starting 1h after infection (acute phase), or TDZ 80 mg/kg/day for 12 days starting 180 days post infection (d.p.i.) (chronic phase). In our experience, the treatment of infected mice, in the acute or in the chronic phases of the infection, with TDZ led to a large reduction in the mortality rates and in the cardiac histological and electrocardiographical abnormalities, and modified the natural evolution of the experimental infection. These analyses reinforce the importance of treatment in the chronic phase to decrease, retard or stop the evolution to chagasic myocardiopathy. Other evidence leading to the use of this drug as a potential chemotherapeutic agent for Chagas disease treatment is also revised.

Are Members of the Triatoma brasiliensis (Hemiptera, Reduviidae) Species Complex Able to Alter the Biology and Virulence of a Trypanosoma cruzi Strain?

Trypanosoma cruzi is the causative agent of Chagas disease, transmitted to humans and mammals by blood-sucking hemipteran insects belonging to the Triatominae subfamily. The two main genotypes of T. cruzi (TcI and TcII) differ in many characteristics concerning their genetic profile. Despite the extensive literature on vectors and the etiologic agent, several interactive aspects between these two elements of Chagas disease are still waiting to be further clarified. Here, biological and histological features resulting from the interaction between Albino Swiss mice and T. cruzi isolate PB913 after passages through vectors of the Triatoma brasiliensis species complex were evaluated. Comparing the four members of the T. brasiliensis species complex-Triatoma brasiliensis brasiliensis Neiva, Triatoma brasiliensis macromelasoma Galvão, Triatoma melanica Neiva & Lent, and Triatoma juazeirensis Costa & Felix-no significant differences in parasitemia of the infected mice were observed. At 20 days post-infection, the highest number of parasites was observed in the group of mice that were infected with parasites obtained from T. b. macromelasoma. Tropism of the parasites to different organs such as heart, bladder, and skeletal muscles followed by inflammatory cell infiltrates was observed with quantitative and qualitative differences. Even though the four members of the T. brasiliensis species complex differ in their geographical distribution, morphology, biology, ecology, and genetics, no significant influence on the parasitemia of the T. cruzi PB913 isolate was detected. After evaluation of the tissue samples, a higher pathogenicity of parasites obtained from T. b. brasiliensis was noticeable.

Mast cells in the colon of Trypanosoma cruzi-infected patients: are they involved in the recruitment, survival and/or activation of eosinophils?

Megacolon is frequently observed in patients who develop the digestive form of Chagas disease. It is characterized by dilation of the rectum-sigmoid portion and thickening of the colon wall. Microscopically, the affected organ presents denervation, which has been considered as consequence of an inflammatory process that begins at the acute phase and persists in the chronic phase of infection. Inflammatory infiltrates are composed of lymphocytes, macrophages, natural killer cells, mast cells, and eosinophils. In this study, we hypothesized that mast cells producing tryptase could influence the migration and the activation of eosinophils at the site, thereby contributing to the immunopathology of the chronic phase. We seek evidence of interactions between mast cells and eosinophils through (1) evaluation of eosinophils, regarding the expression of PAR2, a tryptase receptor; (2) correlation analysis between densities of mast cells and eosinophils; and (3) ultrastructural studies. The electron microscopy studies revealed signs of activation of mast cells and eosinophils, as well as physical interaction between these cells. Immunohistochemistry and correlation analyses point to the participation of tryptase immunoreactive mast cells in the migration and/or survival of eosinophils at the affected organ.

Repolarization Parameters Are Associated With Mortality In Chagas Disease Patients In The United States

Objective

The goal of this study was to examine the association between ECG repolarization parameters and mortality in Chagas disease (CD) patients living in the United States.

Methods

CD patients with cardiomyopathy (CM) and bundle branch block (BBB) or BBB alone were compared to age- and sex-matched controls. QT interval, QT dispersion (QTd), T wave peak to T wave end duration (Tp-Te) and T wave peak to T wave end dispersion ((Tp-Te)d) were measured. Presence of fractionated QRS (fQRS) was also assessed. The main outcome measure was the association between ECG parameters and mortality or need for cardiac transplant.

Results

A total of 18 CM and 13 BBB CD patients were studied with 97% originating from Mexico or Central America. QTd (60.0±15.0 ms vs 43.5±9.8 ms, P=0.0002), Tp-Te (102.6±29.3 ms vs 77.1±11.0 ms, P=0.0002) and (Tp-Te)d (39.5±9.4 ms vs 22.7±7.6 ms, P<0.0001) were prolonged in CD CM patients compared to CM controls. Chagas CM patients had more fQRS then controls (84.2±0.10% vs 33.3±0.11%, p=0.0005). QTd (59.9±15.0 ms vs 29.5±6.9 ms, P=0.0001) and (Tp-Te)d (40.0±15.9 ms vs 18.5±5.4 ms, p<0.0001) were longer in the CD BBB group compared to BBB controls. Univariate analysis showed QTd (56.9±15.0 ms vs 46.5±17.3 ms, p=0.0412) and (Tp-Te)d (36.8±13.5 ms vs 28.5±13.3 ms, p=0.0395) were associated with death and/or need for cardiac transplant.

Conclusion

Our results indicate that P-max and PD are useful electrocardiographic markers for identifying the β-TM-high-risk patients for AF onset, even when the cardiac function is conserved.

Circulating Trypanosoma cruzi populations differ from those found in the tissues of the same host during acute experimental infection

We evaluated the presence and distribution of two Trypanosoma cruzi natural isolates in blood, heart, skeletal muscle, liver, and spleen tissues in the acute phase of the experimental infection (35 days postinfection) in order to determine if the populations present in blood were different to those found in the tissues of the same host. Thirty mice were infected with 50 forms of each isolate or with a combination of them. Presence and molecular characterization of the parasites in the host tissues were determined by specific PCR. Cardiac and skeletal muscle alterations were analyzed by histological studies. T. cruzi variability in the host tissues was analyzed through RFLP studies. Both isolates used consisted of a mixture of two T. cruzi lineages. Specific PCRs were positive for most of the samples from the 3 groups analyzed. Cardiac and skeletal muscle sections from the groups infected with one isolate presented mild to moderate inflammatory infiltrates; the group infected with both isolates showed severe inflammatory infiltrates and the presence of amastigote nests in both tissues. Different parasite populations were found in circulation and in the tissues from the same host. These results are important for patients with high probability of mixed infections in endemic areas and contribute to the knowledge of parasite/host interactions.

Regional variation in the correlation of antibody and T-cell responses to Trypanosoma cruzi

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is a major cause of morbidity and mortality in Central and South America. Geographic variations in the sensitivity of serologic diagnostic assays to T. cruzi may reflect differences in T. cruzi exposure. We measured parasite-specific T-cell responses among seropositive individuals in two populations from South America with widely varying antibody titers against T. cruzi. Antibody titers among seropositive individuals were significantly lower in Arequipa, Peru compared with Santa Cruz, Bolivia. Similarly, the proportion of seropositive individuals with positive T-cell responses was lower in Peru than Bolivia, resulting in overall lower frequencies of interferon-γ (IFNγ)-secreting cells from Peruvian samples. However, the magnitude of the IFNγ response was similar among the IFNγ responders in both locations. These data indicate that immunological discrepancies based on geographic region are reflected in T-cell responses as well as antibody responses.

Temporal variation of Trypanosoma cruzi discrete typing units in asymptomatic Chagas disease patients

Chagas disease caused by Trypanosoma cruzi is a public health problem in Latin America. This parasite displays a high genetic diversity evidenced in six Discrete Typing Units (DTUs) namely TcI-TcVI. The aim of this study was to observe the temporal variation of the DTUs in asymptomatic patients at three different times (10 days interval). The results showed that intermittence is the rule in the bloodstream of Chagas disease patients. The patients showed different detectable DTUs with short time intervals, which favors the clonal histiotropic model and the multiclonality structure of this parasite.

Chronic Chagas' heart disease: a disease on its way to becoming a worldwide health problem: epidemiology, etiopathology, treatment, pathogenesis and laboratory medicine

Chagas' disease, caused by Trypanosoma cruzi infection, is ranked as the most serious parasitic disease in Latin America. Nearly 30% of infected patients develop life-threatening complications, and with a latency of 10-30 years, mostly Chagas' heart disease which is currently the major cause of morbidity and mortality in Latin America, enormously burdening economic resources and dramatically affecting patients' social and labor situations. Because of increasing migration, international tourism and parasite transfer by blood contact, intrauterine transfer and organ transplantation, Chagas' heart disease could potentially become a worldwide problem. To raise awareness of this problem, we reflect on the epidemiology and etiopathology of Chagas' disease, particularly Chagas' heart disease. To counteract Chagas' heart disease, in addition to the general interruption of the infection cycle and chemotherapeutic elimination of the infection agent, early and effective causal or symptomatic therapies would be indispensable. Prerequisites for this are improved knowledge of the pathogenesis and optimized patient management. From economic and logistics viewpoints, this last prerequisite should be performed using laboratory medicine tools. Consequently, we first summarize the mechanisms that have been suggested as driving Chagas' heart disease, mainly those associated with the presence of autoantibodies against G-protein-coupled receptors; secondly, we indicate new treatment strategies involving autoantibody apheresis and in vivo autoantibody neutralization; thirdly, we present laboratory medicine tools such as autoantibody estimation and heart marker measurement, proposed for diagnosis, risk assessment and patient guidance and lastly, we critically reflect upon the increase in inflammation and oxidative stress markers in Chagas' heart disease.

Protective human leucocyte antigen haplotype, HLA-DRB1*01-B*14, against chronic Chagas disease in Bolivia

BACKGROUND

Chagas disease, caused by the flagellate parasite Trypanosoma cruzi affects 8-10 million people in Latin America. The mechanisms that underlie the development of complications of chronic Chagas disease, characterized primarily by pathology of the heart and digestive system, are not currently understood. To identify possible host genetic factors that may influence the clinical course of Chagas disease, Human Leucocyte Antigen (HLA) regional gene polymorphism was analyzed in patients presenting with differing clinical symptoms.

METHODOLOGY

Two hundred and twenty nine chronic Chagas disease patients in Santa Cruz, Bolivia, were examined by serological tests, electrocardiogram (ECG), and Barium enema colon X-ray. 31.4% of the examinees showed ECG alterations, 15.7% megacolon and 58.1% showed neither of them. A further 62 seropositive megacolon patients who had undergone colonectomy due to acute abdomen were recruited. We analyzed their HLA genetic polymorphisms (HLA-A, HLA-B, MICA, MICB, DRB1 and TNF-alpha promoter region) mainly through Sequence based and LABType SSO typing test using LUMINEX Technology.

PRINCIPAL FINDINGS

The frequencies of HLA-DRB1*01 and HLA-B*14:02 were significantly lower in patients suffering from megacolon as well as in those with ECG alteration and/or megacolon compared with a group of patients with indeterminate symptoms. The DRB1*0102, B*1402 and MICA*011 alleles were in strong Linkage Disequilibrium (LD), and the HLA-DRB1*01-B*14-MICA*011 haplotype was associated with resistance against chronic Chagas disease.

CONCLUSIONS

This is the first report of HLA haplotype association with resistance to chronic Chagas disease.

Genetic epidemiology of Chagas disease

Genetic epidemiological approaches hold great promise for improving the understanding of the determinants of susceptibility to infection with Trypanosoma cruzi and the causes of differential disease outcome in T. cruzi-infected individuals. To date, a variety of approaches have been used to understand the role of genetic factors in Chagas disease. Quantitative genetic techniques have been used to estimate the heritabilities for seropositivity for T. cruzi infection and traits that are associated with disease progression in chronic T. cruzi infection. These studies have demonstrated that a significant proportion of the variation in seropositivity and a number of traits related to Chagas disease progression is attributable to genetic factors. Candidate gene studies have provided intriguing evidence for the roles of numerous individual genes in determining cardiac outcomes in chronically infected individuals. Recent results from a long-term study of Chagas disease in a rural area of Brazil have documented that over 60% of the variation in seropositivity status is attributable to genetic factors in that population. Additionally, there are significant genetic effects on a number of electrocardiographic measures and other Chagas disease-related traits. The application of genome-wide approaches will yield new evidence for the roles of specific genes in Chagas disease.

Mitochondrial involvement in chronic chagasic cardiomyopathy

The pathogenesis of chronic chagasic cardiopathy is still under discussion; there is considerable evidence that inflammatory infiltrates and their mediators have a direct effect on cardiac cells. Here we studied the structure and function of cardiac mitochondria in chronic chagasic myocardiopathy. Cardiac mitochondrial structure and enzyme activity of citrate synthase and complexes I to IV of the respiratory chain were studied in albino Swiss mice infected with Trypanosoma cruzi (Tulahuen strain or SGO Z12 isolate) on 365 days post-infection (dpi). The presence of parasites in cardiac and skeletal muscle was also investigated. The activity of complexes I to IV was altered in different ways, according to the strain employed (P<0.0001), in relation to the cristae disorganisation and the parasite persistence found in the Tulahuen group, and the chronic inflammatory process described in both groups; citrate synthase activity also increased in both infected groups. Changes in mitochondrial structure were detected in 89% of Tulahuen- and 58% of SGO Z12-infected mice. In this paper we demonstrate that parasite persistence and inflammation are likely to be involved in the structural and functional alterations in cardiac mitochondria from chronically T. cruzi-infected mice, demonstrating that the parasite strain determines different mitochondrial changes in chagasic cardiopathy.

Molecular mechanisms of host cell invasion by Trypanosoma cruzi

The protozoan parasite Trypanosoma cruzi, the etiologic agent of Chagas disease, is an obligate intracellular protozoan pathogen. Overlapping mechanisms ensure successful infection, yet the relationship between these cellular events and clinical disease remains obscure. This review explores the process of cell invasion from the perspective of cell surface interactions, intracellular signaling, modulation of the host cytoskeleton and endosomal compartment, and the intracellular innate immune response to infection.

Lineage analysis of circulating Trypanosoma cruzi parasites and their association with clinical forms of Chagas disease in Bolivia

Background

The causative agent of Chagas disease, Trypanosoma cruzi, is divided into 6 Discrete Typing Units (DTU): Tc I, IIa, IIb, IIc, IId and IIe. In order to assess the relative pathogenicities of different DTUs, blood samples from three different clinical groups of chronic Chagas disease patients (indeterminate, cardiac, megacolon) from Bolivia were analyzed for their circulating parasites lineages using minicircle kinetoplast DNA polymorphism.

Methods and Findings

Between 2000 and 2007, patients sent to the Centro Nacional de Enfermedades Tropicales for diagnosis of Chagas from clinics and hospitals in Santa Cruz, Bolivia, were assessed by serology, cardiology and gastro-intestinal examinations. Additionally, patients who underwent colonectomies due to Chagasic magacolon at the Hospital Universitario Japonés were also included. A total of 306 chronic Chagas patients were defined by their clinical types (81 with cardiopathy, 150 without cardiopathy, 100 with megacolon, 144 without megacolon, 164 with cardiopathy or megacolon, 73 indeterminate and 17 cases with both cardiopathy and megacolon). DNA was extracted from 10 ml of peripheral venous blood for PCR analysis. The kinetoplast minicircle DNA (kDNA) was amplified from 196 out of 306 samples (64.1%), of which 104 (53.3%) were Tc IId, 4 (2.0%) Tc I, 7 (3.6%) Tc IIb, 1 (0.5%) Tc IIe, 26 (13.3%) Tc I/IId, 1 (0.5%) Tc I/IIb/IId, 2 (1.0%) Tc IIb/d and 51 (25.9%) were unidentified. Of the 133 Tc IId samples, three different kDNA hypervariable region patterns were detected; Mn (49.6%), TPK like (48.9%) and Bug-like (1.5%). There was no significant association between Tc types and clinical manifestations of disease.

Conclusions

None of the identified lineages or sublineages was significantly associated with any particular clinical manifestations in the chronic Chagas patients in Bolivia.

Around 30–50% of Trypanosoma cruzi infections in Latin America cause chronic Chagas disease 10–30 years after the primary infection due to lack of effective treatment. The major clinical complications associated with chronic Chagas disease are cardiac myositis (leading to cardiac failure), and autonomous neuroplexus degeneration of the digestive tract that can cause megacolon or megaesophagus. Therefore, there are three major clinical forms of Chagas disease; cardiac, digestive and indeterminate (asymptomatic). The parasites, which can infect humans as well as other mammals, are transmitted by species of triatomines commonly found in the Americas. The parasite is divided in at least six discrete typing units: TcI, TcIIa–e. In humans, the TcI is mainly observed in Central America and northern parts of South America while the TcIIb/d/e is confined mainly to the southern cone of Latin America. We determined which DTU were prevalent in chronic patients in Bolivia, where the three clinical forms and several DTUs of the parasites are present, in order to determine whether there was a link between a particular parasite DTU and a particular clinical outcome. We found a vast majority of TcIId but its kDNA polymorphism showed no association with any of the clinical manifestations of chronic Chagas.

Chagas disease

Chagas disease is a chronic, systemic, parasitic infection caused by the protozoan Trypanosoma cruzi, and was discovered in 1909. The disease affects about 8 million people in Latin America, of whom 30-40% either have or will develop cardiomyopathy, digestive megasyndromes, or both. In the past three decades, the control and management of Chagas disease has undergone several improvements. Large-scale vector control programmes and screening of blood donors have reduced disease incidence and prevalence. Although more effective trypanocidal drugs are needed, treatment with benznidazole (or nifurtimox) is reasonably safe and effective, and is now recommended for a widened range of patients. Improved models for risk stratification are available, and certain guided treatments could halt or reverse disease progression. By contrast, some challenges remain: Chagas disease is becoming an emerging health problem in non-endemic areas because of growing population movements; early detection and treatment of asymptomatic individuals are underused; and the potential benefits of novel therapies (eg, implantable cardioverter defibrillators) need assessment in prospective randomised trials.

Involvement of the beta-adrenergic system in the cardiac chronic form of experimental Trypanosoma cruzi infection

Changes in the cardiac beta-adrenergic system in early stages of Trypanosoma cruzi infection have been described. Here, we studied an early (135 days post-infection-p.i.) and a late stage (365 days p.i.) of the cardiac chronic form of the experimental infection (Tulahuen or SGO-Z12 strains), determining plasma epinephrine and norepinephrine levels, beta-receptor density, affinity and function, cardiac cAMP concentration and phosphodiesterase activity, cardiac contractility, and the presence of beta-receptor autoantibodies. Tulahuen-infected mice presented lower epinephrine and norepinephrine levels; lower beta-receptor affinity and density; a diminished norepinephrine response and higher cAMP levels in the early stage, and a basal contractility similar to non-infected controls in the early and augmented in the late stage. The Tulahuen strain induced autoantibodies with weak beta-receptor interaction. SGO-Z12-infected mice presented lower norepinephrine levels and epinephrine levels that diminished with the evolution of the infection; lower beta-receptor affinity and an increased density; unchanged epinephrine and norepinephrine response in the early and a diminished response in the late stage; higher cAMP levels and unchanged basal contractility. The SGO-Z12 isolate induced beta-receptor autoantibodies with strong interaction with the beta-receptors. None of the antibodies, however, acted a as beta-receptor agonist. The present results demonstrate that this system is seriously compromised in the cardiac chronic stage of T. cruzi infection.