Phylogenetic analysis of the glucose-6-phosphate isomerase gene in Trypanosoma cruzi

Cynomolgus macaques naturally infected with Trypanosoma cruzi-I exhibit an overall mixed pro-inflammatory/modulated cytokine signature characteristic of human Chagas disease

Background

Non-human primates have been shown to be useful models for Chagas disease. We previously reported that natural T. cruzi infection of cynomolgus macaques triggers clinical features and immunophenotypic changes of peripheral blood leukocytes resembling those observed in human Chagas disease. In the present study, we further characterize the cytokine-mediated microenvironment to provide supportive evidence of the utility of cynomolgus macaques as a model for drug development for human Chagas disease.

Methods and findings

In this cross-sectional study design, flow cytometry and systems biology approaches were used to characterize the ex vivo and in vitro T. cruzi-specific functional cytokine signature of circulating leukocytes from TcI-T. cruzi naturally infected cynomolgus macaques (CH). Results showed that CH presented an overall CD4⁺-derived IFN-γ pattern regulated by IL-10-derived from CD4⁺ T-cells and B-cells, contrasting with the baseline profile observed in non-infected hosts (NI). Homologous TcI-T. cruzi-antigen recall in vitro induced a broad pro-inflammatory cytokine response in CH, mediated by TNF from innate/adaptive cells, counterbalanced by monocyte/B-cell-derived IL-10. TcIV-antigen triggered a more selective cytokine signature mediated by NK and T-cell-derived IFN-γ with modest regulation by IL-10 from T-cells. While NI presented a cytokine network comprised of small number of neighborhood connections, CH displayed a complex cross-talk amongst network elements. Noteworthy, was the ability of TcI-antigen to drive a complex global pro-inflammatory network mediated by TNF and IFN-γ from NK-cells, CD4⁺ and CD8⁺ T-cells, regulated by IL-10⁺CD8⁺ T-cells, in contrast to the TcIV-antigens that trigger a modest network, with moderate connecting edges.

Conclusions

Altogether, our findings demonstrated that CH present a pro-inflammatory/regulatory cytokine signature similar to that observed in human Chagas disease. These data bring additional insights that further validate these non-human primates as experimental models for Chagas disease.

Trypanosoma cruzi is the causative agent of Chagas disease; millions of people are infected with this parasite. One of the major challenges to manage infected patients is the low efficacy of currently available treatments, especially during chronic infection. Different T. cruzi genotypes are known to differ in response to existing drugs (e.g., TcI is quite resistant), and differences among individuals in immune response also are believed to play a role determining therapeutic efficacy. Experimental models and in vitro systems have been proposed for rational searches for new compounds for treating infected individuals, optimally before the infection becomes clinically manifested as Chagas disease. In the field of drug development, the non-human primate models offer a unique and valuable contribution, as a consequence of patho-physiological similarities that mimic many human diseases, including Chagas disease. In the present study, we further investigated the functional features of the immune response triggered by TcI T. cruzi-infection, characterizing the ex vivo as well as the in vitro cytokine microenvironment, upon T. cruzi-antigen recall. Our results revealed that chronically infected cynomolgus macaques display a similar ex vivo cytokine signature to that observed in chronic human Chagas disease. Moreover, CH macaques display a complex cross-talk among the cytokine⁺ leukocyte subsets, enhanced by TcI T. cruzi-antigen recall in vitro. These findings provide additional insights that further validate these non-human primates as experimental models for rational development of new therapeutic agents for Chagas disease.

Real-time PCR strategy for the identification of Trypanosoma cruzi discrete typing units directly in chronically infected human blood

The protozoan Trypanosoma cruzi is the causative agent of Chagas disease, a major public health problem in Latin America. This parasite has a complex population structure comprised by six or seven major evolutionary lineages (discrete typing units or DTUs) TcI-TcVI and TcBat, some of which have apparently resulted from ancient hybridization events. Because of the existence of significant biological differences between these lineages, strain characterization methods have been essential to study T. cruzi in its different vectors and hosts. However, available methods can be laborious and costly, limited in resolution or sensitivity. In this study, a new genotyping strategy by real-time PCR to identify each of the six DTUs in clinical blood samples have been developed and evaluated. Two nuclear (SL-IR and 18S rDNA) and two mitochondrial genes (COII and ND1) were selected to develop original primers. The method was evaluated with eight genomic DNA of T. cruzi populations belonging to the six DTUs, one genomic DNA of Trypanosoma rangeli, and 53 blood samples from individuals with chronic Chagas disease. The assays had an analytical sensitivity of 1-25fg of DNA per reaction tube depending on the DTU analyzed. The selectivity of trials with 20fg/μL of genomic DNA identified each DTU, excluding non-targets DTUs in every test. The method was able to characterize 67.9% of the chronically infected clinical samples with high detection of TcII followed by TcI. With the proposed original genotyping methodology, each DTU was established with high sensitivity after a single real-time PCR assay. This novel protocol reduces carryover contamination, enables detection of each DTU independently and in the future, the quantification of each DTU in clinical blood samples.

Geographical, landscape and host associations of Trypanosoma cruzi DTUs and lineages

Background

The evolutionary history and ecological associations of Trypanosoma cruzi, the need to identify genetic markers that can distinguish parasite subpopulations, and understanding the parasite’s evolutionary and selective processes have been the subject of a significant number of publications since 1998, the year when the first DNA sequence analysis for the species was published.

Methods

The current analysis systematizes and re-analyzes this original research, focusing on critical methodological and analytical variables and results that have given rise to interpretations of putative patterns of genetic diversity and diversification of T. cruzi lineages, discrete typing units (DTUs), and populations, and their associations with hosts, vectors, and geographical distribution that have been interpreted as evidence for parasite subpopulation specificities.

Results

Few studies use hypothesis-driven or quantitative analysis for T. cruzi phylogeny (16/58 studies) or phylogeography (10/13). Among these, only one phylogenetic and five phylogeographic studies analyzed molecular markers directly from tissues (i.e. not from isolates). Analysis of T. cruzi DTU or lineage niche and its geographical projection demonstrate extensive sympatry among all clades across the continent and no significant niche differences among DTUs. DTU beta-diversity was high, indicating diverse host assemblages across regions, while host dissimilarity was principally due to host species turnover and to a much lesser degree to nestedness. DTU-host order specificities appear related to trophic or microenvironmental interactions.

Conclusions

More rigorous study designs and analyses will be required to discern evolutionary processes and the impact of landscape modification on population dynamics and risk for T. cruzi transmission to humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1918-2) contains supplementary material, which is available to authorized users.

Ecological scenario and Trypanosoma cruzi DTU characterization of a fatal acute Chagas disease case transmitted orally (Espírito Santo state, Brazil)

BACKGROUND

Trypanosoma cruzi infection via oral route results in outbreaks or cases of acute Chagas disease (ACD) in different Brazilian regions and poses a novel epidemiological scenario. In the Espírito Santo state (southeastern Brazil), a fatal case of a patient with ACD led us to investigate the enzootic scenario to avoid the development of new cases. At the studied locality, Triatoma vitticeps exhibited high T. cruzi infection rates and frequently invaded residences.

METHODS

Sylvatic and domestic mammals in the Rio da Prata locality, where the ACD case occurred, and in four surrounding areas (Baia Nova, Buenos Aires, Santa Rita and Todos os Santos) were examined and underwent parasitological and serological tests. Triatomines were collected for a fecal material exam, culturing and mini-exon gene molecular characterization, followed by RFLP-PCR of H3/Alul. Paraffin-embedded cardiac tissue of a patient was washed with xylene to remove paraffin and DNA was extracted using the phenol-chloroform method. For genotype characterization, PCR was performed to amplify the 1f8, GPI and 18S rRNA genes. In the case of V7V8 SSU rRNA, the PCR products were molecularly cloned. PCR products were sequenced and compared to sequences in GenBank. Phylogenetic analysis using maximum likelihood method with 1000 bootstrap replicates was performed.

RESULTS

None of the animals showed positive hemocultures. Three rodents and two dogs showed signs of infection, as inferred from borderline serological titers. T. vitticeps was the only triatomine species identified and showed T. cruzi infection by DTUs TcI and TcIV. The analysis of cardiac tissue DNA showed mixed infection by T. cruzi (DTUs I, II, III and IV) and Trypanosoma dionisii.

CONCLUSIONS

Each case or outbreak of ACD should be analyzed as a particular epidemiological occurrence. The results indicated that mixed infections in humans may play a role in pathogenicity and may be more common than is currently recognized. Direct molecular characterization from biological samples is essential because this procedure avoids parasite selection. T. dionisii may under certain and unknown circumstances infect humans. The distribution of T. cruzi DTUS TcIII and TcIV in Brazilian biomes is broader than has been assumed to date.

Vector-borne transmission of Trypanosoma cruzi among captive Neotropical primates in a Brazilian zoo

BACKGROUND

Neotropical primates are important sylvatic hosts of Trypanosoma cruzi, the etiological agent of Chagas disease. Infection is often subclinical, but severe disease has been described in both free-ranging and captive primates. Panstrongylus megistus, a major T. cruzi vector, was found infesting a small-primate unit at Brasília zoo (ZooB), Brazil. ZooB lies close to a gallery-forest patch where T. cruzi circulates naturally. Here, we combine parasitological and molecular methods to investigate a focus of T. cruzi infection involving triatomine bugs and Neotropical primates at a zoo located in the Brazilian Savannah.

METHODS

We assessed T. cruzi infection in vectors using optical microscopy (n = 34) and nested PCR (n = 50). We used quantitative PCR (qPCR) to examine blood samples from 26 primates and necropsy samples from two primates that died during the study. We determined parasite lineages in five vectors and two primates by comparing glucose-6-phosphate isomerase (G6pi) gene sequences.

RESULTS

Trypanosoma cruzi was found in 44 vectors and 17 primates (six genera and eight species); one Mico chrysoleucus and one Saguinus niger had high parasitaemias. Trypanosoma cruzi DNA was detected in three primates born to qPCR-negative mothers at ZooB and in the two dead specimens. One Callithrix geoffroyi became qPCR-positive over a two-year follow-up. All G6pi sequences matched T. cruzi lineage TcI.

CONCLUSIONS

Our findings strongly suggest vector-borne T. cruzi transmission within a small-primate unit at ZooB - with vectors, and perhaps also parasites, presumably coming from nearby gallery forest. Periodic checks for vectors and parasites would help eliminate T. cruzi transmission foci in captive-animal facilities. This should be of special importance for captive-breeding programs involving endangered mammals, and would reduce the risk of accidental T. cruzi transmission to keepers and veterinarians.

Predominance of hybrid discrete typing units of Trypanosoma cruzi in domestic Triatoma infestans from the Bolivian Gran Chaco region

In the Gran Chaco region the reinfestation by Triatoma infestans remains a major problem for control of Chagas disease. Trypanosoma cruzi the agent of the illness presents a broad genetic intraspecific variability which is poorly documented in the Bolivian Gran Chaco. This work presents the identification of the discrete typing units (DTUs) currently recognized for T. cruzi in T. infestans populations collected before and after residual insecticide spraying in four villages in this region. Before spraying, of 84 samples, the frequencies of the DTUs identified by using the multiplex PCR based on the non transcribed spacer of the mini-exon gene (MMPCR) were 0.21 for TcI, 0.70 for TcII/TcV/TcVI, and 0.17 for TcIII/TcIV and no significant difference was observed after spraying (76 samples). Moreover 13% of the total sample corresponds to T. infestans specimens with mixed infection of DTUs of which three were TcII/TcV/TcVI with TcIII/TcIV. The partial sequences of T. cruzi Gpi gene obtained from 14 PCR products agree the MMPCR DTU identification and allowed to precise the occurrence of TcIII, TcII and hybrid TcV/TcVI stocks which were not discriminated by the MMPCR. Given the high prevalence of hybrid stocks, the authors ask whether the recombination event at the origin of hybrids would have taken place in the Gran Chaco where the putative parents are also present.

Scarce events of mitochondrial introgression in Trypanosoma cruzi: new case with a Bolivian strain

Trypanosoma cruzi, the agent of Chagas disease, presents a predominantly clonal structure that has been shaped by recombination events leading to six genetic groups (DTUs, discrete typing units, TcI-TcVI). Several conventional and unconventional genetic exchange events have been described, including hybridization and mitochondrial introgression, which is explored here among Bolivian and Peruvian strains belonging to TcI because recombination events have been previously suspected by means of the MLMT method (multilocus microsatellite typing). We analyzed the variation of one nuclear (Gpi) and one mitochondrial (Nd1) gene among 60 TcI strains and 15 reference strains belonging to the six DTUs. The results clearly showed that one strain isolated from Triatoma infestans in the Cochabamba department (Bolivia) presented a genotype TcI for Gpi and a mitochondrial Nd1 genotype common to the DTUs TcIII, IV, V, and VI; this can be interpreted as a mitochondrial introgression event between distant DTUs. These kinds of events, although probably scarce, may have played an important role in the adaptive evolution of the species.

Trypanosoma cruzi IV causing outbreaks of acute Chagas disease and infections by different haplotypes in the Western Brazilian Amazonia

BACKGROUND

Chagas disease is an emergent tropical disease in the Brazilian Amazon Region, with an increasing number of cases in recent decades. In this region, the sylvatic cycle of Trypanosoma cruzi transmission, which constitutes a reservoir of parasites that might be associated with specific molecular, epidemiological and clinical traits, has been little explored. The objective of this work is to genetically characterize stocks of T. cruzi from human cases, triatomines and reservoir mammals in the State of Amazonas, in the Western Brazilian Amazon.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed 96 T. cruzi samples from four municipalities in distant locations of the State of Amazonas. Molecular characterization of isolated parasites from cultures in LIT medium or directly from vectors or whole human blood was performed by PCR of the non-transcribed spacer of the mini-exon and of the 24 S alfa ribosomal RNA gene, RFLP and sequencing of the mitochondrial cytochrome c oxidase subunit II (COII) gene, and by sequencing of the glucose-phosphate isomerase gene. The T. cruzi parasites from two outbreaks of acute disease were all typed as TcIV. One of the outbreaks was triggered by several haplotypes of the same DTU. TcIV also occurred in isolated cases and in Rhodnius robustus. Incongruence between mitochondrial and nuclear phylogenies is likely to be indicative of historical genetic exchange events resulting in mitochondrial introgression between TcIII and TcIV DTUs from Western Brazilian Amazon. TcI predominated among triatomines and was the unique DTU infecting marsupials.

CONCLUSION/SIGNIFICANCE

DTU TcIV, rarely associated with human Chagas disease in other areas of the Amazon basin, is the major strain responsible for the human infections in the Western Brazilian Amazon, occurring in outbreaks as single or mixed infections by different haplotypes.

Genetic characterization of Trypanosoma cruzi DTUs in wild Triatoma infestans from Bolivia: predominance of TcI

Background

The current persistence of Triatoma infestans (one of the main vectors of Chagas disease) in some domestic areas could be related to re-colonization by wild populations which are increasingly reported. However, the infection rate and the genetic characterization of the Trypanosoma cruzi strains infecting these populations are very limited.

Methodology/Principal Findings

Of 333 wild Triatoma infestans specimens collected from north to south of a Chagas disease endemic area in Bolivia, we characterized 234 stocks of Trypanosoma cruzi using mini-exon multiplex PCR (MMPCR) and sequencing the glucose phosphate isomerase (Gpi) gene. Of the six genetic lineages (“discrete typing units”; DTU) (TcI-VI) presently recognized in T. cruzi, TcI (99.1%) was overdominant on TcIII (0.9%) in wild Andean T. infestans, which presented a 71.7% infection rate as evaluated by microscopy. In the lowlands (Bolivian Chaco), 17 “dark morph” T. infestans were analyzed. None of them were positive for parasites after microscopic examination, although one TcI stock and one TcII stock were identified using MMPCR and sequencing.

Conclusions/Significance

By exploring large-scale DTUs that infect the wild populations of T. infestans, this study opens the discussion on the origin of TcI and TcV DTUs that are predominant in domestic Bolivian cycles.

Chagas disease is a neglected parasitic disease transmitted by bugs (vectors) and represents a serious health problem in the Americas. Although the transmission generally occurs in the houses where the bugs are living, wild populations of vectors are now considered a problem because these populations might enter the houses and recolonize them after eliminating of house populations by insecticide spraying. This is the case of the Southern countries where Triatoma infestans, the principal vector, transmits Trypanosoma cruzi the agent of the disease. This parasite presents a large genetic variability and it is important to know which T. cruzi genotypes are carried by the vectors. The authors found that in the wild T. infestans from the Bolivian Andean region, a principal group of genotype was circulating. In the lowlands (Bolivian Chaco), another additional genotype group was detected. Together with exploring at large scale which genotypes are infecting T. infestans wild populations, this study opens the discussion on the origin T. cruzi genotype groups. Also this study completes our basic knowledge on T. cruzi subspecific genetic variability, and therefore brings new tools for molecular epidemiology of Chagas disease.

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.

Analyses of 32 loci clarify phylogenetic relationships among Trypanosoma cruzi lineages and support a single hybridization prior to human contact

Background

The genetic diversity of Trypanosoma cruzi, the etiological agent of Chagas disease, has been traditionally divided in two major groups, T. cruzi I and II, corresponding to discrete typing units TcI and TcII-VI under a recently proposed nomenclature. The two major groups of T. cruzi seem to differ in important biological characteristics, and are thus thought to represent a natural division relevant for epidemiological studies and development of prophylaxis. To understand the potential connection between the different manifestations of Chagas disease and variability of T. cruzi strains, it is essential to have a correct reconstruction of the evolutionary history of T. cruzi.

Methodology/Principal Findings

Nucleotide sequences from 32 unlinked loci (>26 Kilobases of aligned sequence) were used to reconstruct the evolutionary history of strains representing the known genetic variability of T. cruzi. Thorough phylogenetic analyses show that the original classification of T. cruzi in two major lineages does not reflect its evolutionary history and that there is only strong evidence for one major and recent hybridization event in the history of this species. Furthermore, estimates of divergence times using Bayesian methods show that current extant lineages of T. cruzi diverged very recently, within the last 3 million years, and that the major hybridization event leading to hybrid lineages TcV and TcVI occurred less than 1 million years ago, well before the contact of T. cruzi with humans in South America.

Conclusions/Significance

The described phylogenetic relationships among the six major genetic subdivisions of T. cruzi should serve as guidelines for targeted epidemiological and prophylaxis studies. We suggest that it is important to reconsider conclusions from previous studies that have attempted to uncover important biological differences between the two originally defined major lineages of T. cruzi especially if those conclusions were obtained from single or few strains.

Trypanosoma cruzi is the protozoan parasite that causes Chagas disease, a major health problem in Latin America. The genetic diversity of this parasite has been traditionally divided in two major groups: T. cruzi I and II, which can be further divided in six major genetic subdivisions (subgroups TcI-TcVI). T. cruzi I and II seem to differ in important biological characteristics, and are thought to represent a natural division relevant for epidemiological studies and development of prophylaxis. Having a correct reconstruction of the evolutionary history of T. cruzi is essential for understanding the potential connection between the genetic and phenotypic variability of T. cruzi with the different manifestations of Chagas disease. Here we present results from a comprehensive phylogenetic analysis of T. cruzi using more than 26 Kb of aligned sequence data. We show strong evidence that T. cruzi II (TcII-VI) is not a natural evolutionary group but a paraphyletic lineage and that all major lineages of T. cruzi evolved recently (<3 million years ago [mya]). Furthermore, the sequence data is consistent with one major hybridization event having occurred in this species recently (< 1 mya) but well before T. cruzi entered in contact with humans in South America.

Multilocus sequence typing (MLST) for lineage assignment and high resolution diversity studies in Trypanosoma cruzi

BACKGROUND

Multilocus sequence typing (MLST) is a powerful and highly discriminatory method for analysing pathogen population structure and epidemiology. Trypanosoma cruzi, the protozoan agent of American trypanosomiasis (Chagas disease), has remarkable genetic and ecological diversity. A standardised MLST protocol that is suitable for assignment of T. cruzi isolates to genetic lineage and for higher resolution diversity studies has not been developed.

METHODOLOGY/PRINCIPAL FINDINGS

We have sequenced and diplotyped nine single copy housekeeping genes and assessed their value as part of a systematic MLST scheme for T. cruzi. A minimum panel of four MLST targets (Met-III, RB19, TcGPXII, and DHFR-TS) was shown to provide unambiguous assignment of isolates to the six known T. cruzi lineages (Discrete Typing Units, DTUs TcI-TcVI). In addition, we recommend six MLST targets (Met-II, Met-III, RB19, TcMPX, DHFR-TS, and TR) for more in depth diversity studies on the basis that diploid sequence typing (DST) with this expanded panel distinguished 38 out of 39 reference isolates. Phylogenetic analysis implies a subdivision between North and South American TcIV isolates. Single Nucleotide Polymorphism (SNP) data revealed high levels of heterozygosity among DTUs TcI, TcIII, TcIV and, for three targets, putative corresponding homozygous and heterozygous loci within DTUs TcI and TcIII. Furthermore, individual gene trees gave incongruent topologies at inter- and intra-DTU levels, inconsistent with a model of strict clonality.

CONCLUSIONS/SIGNIFICANCE

We demonstrate the value of systematic MLST diplotyping for describing inter-DTU relationships and for higher resolution diversity studies of T. cruzi, including presence of recombination events. The high levels of heterozygosity will facilitate future population genetics analysis based on MLST haplotypes.

Trypanosoma cruzi IIc: phylogenetic and phylogeographic insights from sequence and microsatellite analysis and potential impact on emergent Chagas disease

Trypanosoma cruzi, the etiological agent of Chagas disease, is highly genetically diverse. Numerous lines of evidence point to the existence of six stable genetic lineages or DTUs: TcI, TcIIa, TcIIb, TcIIc, TcIId, and TcIIe. Molecular dating suggests that T. cruzi is likely to have been an endemic infection of neotropical mammalian fauna for many millions of years. Here we have applied a panel of 49 polymorphic microsatellite markers developed from the online T. cruzi genome to document genetic diversity among 53 isolates belonging to TcIIc, a lineage so far recorded almost exclusively in silvatic transmission cycles but increasingly a potential source of human infection. These data are complemented by parallel analysis of sequence variation in a fragment of the glucose-6-phosphate isomerase gene. New isolates confirm that TcIIc is associated with terrestrial transmission cycles and armadillo reservoir hosts, and demonstrate that TcIIc is far more widespread than previously thought, with a distribution at least from Western Venezuela to the Argentine Chaco. We show that TcIIc is truly a discrete T. cruzi lineage, that it could have an ancient origin and that diversity occurs within the terrestrial niche independently of the host species. We also show that spatial structure among TcIIc isolates from its principal host, the armadillo Dasypus novemcinctus, is greater than that among TcI from Didelphis spp. opossums and link this observation to differences in ecology of their respective niches. Homozygosity in TcIIc populations and some linkage indices indicate the possibility of recombination but cannot yet be effectively discriminated from a high genome-wide frequency of gene conversion. Finally, we suggest that the derived TcIIc population genetic data have a vital role in determining the origin of the epidemiologically important hybrid lineages TcIId and TcIIe.

The molecular epidemiology and phylogeography of Trypanosoma cruzi and parallel research on Leishmania: looking back and to the future

Trypanosoma cruzi is the protozoan agent of Chagas disease, and the most important parasitic disease in Latin America. Protozoa of the genus Leishmania are global agents of visceral and cutaneous leishmaniasis, fatal and disfiguring diseases. In the 1970s multilocus enzyme electrophoresis demonstrated that T. cruzi is a heterogeneous complex. Six zymodemes were described, corresponding with currently recognized lineages, TcI and TcIIa-e – now defined by multiple genetic markers. Molecular epidemiology has substantially resolved the phylogeography and ecological niches of the T. cruzi lineages. Genetic hybridization has fundamentally influenced T. cruzi evolution and epidemiology of Chagas disease. Genetic exchange of T. cruzi in vitro involves fusion of diploids and genome erosion, producing aneuploid hybrids. Transgenic fluorescent clones are new tools to elucidate molecular genetics and phenotypic variation. We speculate that pericardial sequestration plays a role in pathogenesis. Multilocus sequence typing, microsatellites and, ultimately, comparative genomics are improving understanding of T. cruzi population genetics. Similarly, in Leishmania, genetic groups have been defined, including epidemiologically important hybrids; genetic exchange can occur in the sand fly vector. We describe the profound impact of this parallel research on genetic diversity of T. cruzi and Leishmania, in the context of epidemiology, taxonomy and disease control.

Synthesis and trypanocidal activity of 1,4-bis-(3,4,5-trimethoxy-phenyl)-1,4-butanediol and 1,4-bis-(3,4-dimethoxyphenyl)-1,4-butanediol

Chagas' disease is endemic in Central and South American countries. Specific chemotherapy with nifurtimox or benznidazole has been recommended for treatment of recent infection but they have limited efficacy. The natural products veraguensin (1) and grandisin (2) have shown potent in vitro activity against trypomastigote parasite (Y strain) with IC(50) 2.3 microM (1) and 3.7 microM (2). We report herein the synthesis and in vitro trypanocidal evaluation of symmetrical and unsymmetrical 1,4-diaryl-1,4-diol derivatives as potential trypanocidal analogs of natural compounds 1 and 2. Among the synthesized products, compounds 1,4-bis-(3,4,5-trimethoxyphenyl)-1,4-butanediol (6a) and 1,4-bis-(3,4-dimethoxyphenyl)-1,4-butanediol (6b) showed better activity against Trypanosoma cruzi trypomastigotes with IC(50) 100 and 105 microM (Y strain), respectively, and 110 microM (Bolivia strain) for both compounds. However, the most active compound of this series was 1,4-bis-(3,4-dimethoxyphenyl)butane-1,4-dione (7b) with IC(50) 10 and 200 microM against Y and Bolivia strains, respectively.