Evolutionary genetics of Trypanosoma and Leishmania

Differential expression of meiosis and homologous recombination-related genes in the life cycle of Trypanosoma cruzi

Trypanosoma cruzi has a complex life cycle consisting of four morphological and distinct biological stages. Although some authors suggest that T. cruzi primarily follows clonal reproduction, recent genomic and transcriptomic studies indicate an unorthodox capacity for recombination. We aimed to estimate the differential gene expression of 10 meiosis/homologous recombination-related genes during the T. cruzi life cycle, including epimastigotes, under two different types of stress (oxidative stress and pH changes). We performed RT-qPCR tests using novel-designed primers to estimate the differential gene expression (∆Ct and ∆∆Ct) of nine genes (SPO11, HAP2, RAD50, MRN complex, BRCA2, DMC1, MND1, and RPA1) and RAD51, which was previously reported. Our results show basal expression of all genes during the life cycle, indicating their hypothetical role in several cellular processes but with specific signatures of differential gene expression during the life cycle (HAP2, RPA, RAD50, BRCA2, MND1, and DMC1) and oxidative stress (RPA, MRE11, NBS1, BRCA2, MND1, and RAD51). Additionally, we found that the MRN complex has an independent level of expression in T. cruzi, with profiles of MRE11 and NBS1 upregulated in some stages. Recent studies on other trypanosomatids have highlighted the influence of HAP2 and RPA in recombination and hybridization. If T. cruzi uses the same repertoire of genes, our findings could suggest that metacyclogenesis may be the putative step that the parasite uses to undergo recombination. Likewise, our study reveals the differential profiles of genes expressed in response to oxidative and pH stress. Further studies are necessary to confirm our findings and understand the recombination mechanism in T. cruzi.

Leishmania braziliensis causing human disease in Northeast Brazil presents loci with genotypes in long-term equilibrium

Background

Leishmaniases are neglected tropical diseases that inflict great burden to poor areas of the globe. Intense research has aimed to identify parasite genetic signatures predictive of infection outcomes. Consistency of diagnostic tools based on these markers would greatly benefit from accurate understanding of Leishmania spp. population genetics. We explored two chromosomal loci to characterize a population of L. braziliensis causing human disease in Northeast Brazil.

Methodology/Principal findings

Two temporally distinct samples of L. braziliensis were obtained from patients attending the leishmaniasis clinic at the village of Corte de Pedra: (2008–2011) primary sample, N = 120; (1999–2001) validation sample, N = 35. Parasites were genotyped by Sanger’s sequencing of two 600 base pairs loci starting at nucleotide positions 3,074 and 425,451 of chromosomes 24 and 28, respectively. Genotypes based on haplotypes of biallelic positions in each locus were tested for several population genetic parameters as well as for geographic clustering within the region. Ample geographic overlap of genotypes at the two loci was observed as indicated by non-significant Cusick and Edward’s comparisons. No linkage disequilibrium was detected among combinations of haplotypes for both parasite samples. Homozygous and heterozygous genotypes displayed Hardy-Weinberg equilibrium (HWE) at both loci in the two samples when straight observed and expected counts were compared by Chi-square (p>0.5). However, Bayesian statistics using one million Monte-Carlo randomizations disclosed a less robust HWE for chromosome 24 genotypes, particularly in the primary sample (p = 0.04). Fixation indices (Fst) were consistently lower than 0.05 among individuals of the two samples at both tested loci, and no intra-populational structuralization could be detected using STRUCTURE software.

Conclusions/Significance

These findings suggest that L. braziliensis can maintain stable populations in foci of human leishmaniasis and are capable of robust genetic recombination possibly due to events of sexual reproduction during the parasite’s lifecycle.

Leishmania braziliensis affects poor human populations in the tropics, may cause face disfiguring lesions and may also resist treatment. There has been intense research for markers in these parasites genetic contents for helping predict if an infected human being would be of greater chance of severe disease or treatment failure. The consistent identification of such markers requires a deep understanding of how genes circulate within these parasites’ natural populations. We explored two small segments of DNA (i.e. loci), one on chromosome 24, the other on chromosome 28 of L. braziliensis to characterize a population that causes human disease in Northeast Brazil. We employed two samples of parasites obtained from lesions of patients diagnosed from 1999 to 2001, and from 2008 to 2011. We sequenced the DNA of those loci in each parasite of the two samples. Then, we evaluated the status of several population genetics parameters among them. Based on our findings to that region, we concluded that L. braziliensis can maintain populations that are genetically stable for several years in foci of human leishmaniasis and are capable of robust recombination of their genetic contents, probably due to events of sexual reproduction during its lifecycle.

Combined parasitological and molecular-based diagnostic tools improve the detection of Trypanosoma cruzi in single peripheral blood samples from patients with Chagas disease

INTRODUCTION

In order to detect Trypanosoma cruzi and determine the genetic profiles of the parasite during the chronic phase of Chagas disease (ChD), parasitological and molecular diagnostic methods were used to assess the blood of 91 patients without specific prior treatment.

METHODS

Blood samples were collected from 68 patients with cardiac ChD and 23 patients with an indeterminate form of ChD, followed by evaluation using blood culture and polymerase chain reaction. T . cruzi isolates were genotyped using three different genetic markers.

RESULTS:

Blood culture was positive in 54.9% of all patients, among which 60.3% had the cardiac form of ChD, and 39.1% the indeterminate form of ChD. There were no significant differences in blood culture positivity among patients with cardiac and indeterminate forms. Additionally, patient age and clinical forms did not influence blood culture results. Polymerase chain reaction (PCR) was positive in 98.9% of patients, although comparisons between blood culture and PCR results showed that the two techniques did not agree. Forty-two T . cruzi stocks were isolated, and TcII was detected in 95.2% of isolates. Additionally, one isolate corresponded to TcIII or TcIV, and another corresponded to TcV or TcVI.

CONCLUSIONS

Blood culture and PCR were both effective for identifying T. cruzi using a single blood sample, and their association did not improve parasite detection. However, we were not able to establish an association between the clinical form of ChD and the genetic profile of the parasite.

Genetic variability of Leishmania infantum in naturally infected dogs in the state of Bahia, Brazil

In Brazil, Leishmania infantum mainly affects humans and dogs. The state of Bahia presents many dogs that are positive for this parasite. Despite the importance of epidemiology in this region, there are still very few studies that have assessed the genetic characteristics of L. infantum. The aim of this study is to investigate the genetic variability of L. infantum isolated identified in naturally infected dogs, in order to verify occurrence of subpopulation of this parasite in the different biomes existing in the state of Bahia. Thirty-two samples of L. infantum were analyzed, which were obtained isolated in dogs from the Mata Atlântica (rainforest), Caatinga (semi-arid scrub forest), and Cerrado (a vast tropical savannah eco-region) Bahia municipalities' biomes. All animals presented with clinical changes suggestive of Leishmania spp. and they exhibited positive reactions to serological tests. kDNA analysis with RFLP markers revealed the presence of genetic variability and gene flow in subpopulations of L. infantum; samples from the Mata Atlântica areas were genetically more similar to those from the areas of Caatinga and they were less likely to resemble those of the Cerrado. This data may be used to investigate the dissemination of parasite in the canine population of state of Bahia.

The evolution of trypanosomatid taxonomy

Trypanosomatids are protozoan parasites of the class Kinetoplastida predominately restricted to invertebrate hosts (i.e. possess a monoxenous life-cycle). However, several genera are pathogenic to humans, animals and plants, and have an invertebrate vector that facilitates their transmission (i.e. possess a dixenous life-cycle). Phytomonas is one dixenous genus that includes several plant pathogens transmitted by phytophagous insects. Trypanosoma and Leishmania are dixenous genera that infect vertebrates, including humans, and are transmitted by hematophagous invertebrates. Traditionally, monoxenous trypanosomatids such as Leptomonas were distinguished from morphologically similar dixenous species based on their restriction to an invertebrate host. Nonetheless, this criterion is somewhat flawed as exemplified by Leptomonas seymouri which reportedly infects vertebrates opportunistically. Similarly, Novymonas and Zelonia are presumably monoxenous genera yet sit comfortably in the dixenous clade occupied by Leishmania. The isolation of Leishmania macropodum from a biting midge (Forcipomyia spp.) rather than a phlebotomine sand fly calls into question the exclusivity of the Leishmania-sand fly relationship, and its suitability for defining the Leishmania genus. It is now accepted that classic genus-defining characteristics based on parasite morphology and host range are insufficient to form the sole basis of trypanosomatid taxonomy as this has led to several instances of paraphyly. While improvements have been made, resolution of evolutionary relationships within the Trypanosomatidae is confounded by our incomplete knowledge of its true diversity. The known trypanosomatids probably represent a fraction of those that exist and isolation of new species will help resolve relationships in this group with greater accuracy. This review incites a dialogue on how our understanding of the relationships between certain trypanosomatids has shifted, and discusses new knowledge that informs the present taxonomy of these important parasites.

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.

Genetic homogeneity among Leishmania (Leishmania) infantum isolates from dog and human samples in Belo Horizonte Metropolitan Area (BHMA), Minas Gerais, Brazil

BACKGROUND

Certain municipalities in the Belo Horizonte Metropolitan Area (BHMA), Minas Gerais, Brazil, have the highest human visceral leishmaniasis (VL) mortality rates in the country and also demonstrate high canine seropositivity. In Brazil, the etiologic agent of VL is Leishmania (Leishmania) infantum. The aim of this study was to evaluate the intraspecific genetic variability of parasites from humans and from dogs with different clinical forms of VL in five municipalities of BHMA using PCR-RFLP and two target genes: kinetoplast DNA (kDNA) and gp63.

METHODS

In total, 45 samples of DNA extracted from clinical samples (n = 35) or L. infantum culture (n = 10) were evaluated. These samples originated from three groups: adults (with or without Leishmania/HIV co-infection; n = 14), children (n = 18) and dogs (n = 13). The samples were amplified for the kDNA target using the MC1 and MC2 primers (447 bp), while the Sg1 and Sg2 (1330 bp) primers were used for the gp63 glycoprotein target gene.

RESULTS

The restriction enzyme patterns of all the samples tested were monomorphic.

CONCLUSIONS

These findings reveal a high degree of genetic homogeneity for the evaluated gene targets among L. infantum samples isolated from different hosts and representing different clinical forms of VL in the municipalities of BHMA studied.

Putative panmixia in restricted populations of Trypanosoma cruzi isolated from wild Triatoma infestans in Bolivia

Trypanosoma cruzi, the causative agent of Chagas disease, is subdivided into six discrete typing units (DTUs; TcI-TcVI) of which TcI is ubiquitous and genetically highly variable. While clonality is the dominant mode of propagation, recombinant events play a significant evolutive role. Recently, foci of wild Triatoma infestans have been described in Bolivia, mainly infected by TcI. Hence, for the first time, we evaluated the level of genetic exchange within TcI natural potentially panmictic populations (single DTU, host, area and sampling time). Seventy-nine TcI stocks from wild T. infestans, belonging to six populations were characterized at eight microsatellite loci. For each population, Hardy-Weinberg equilibrium (HWE), linkage disequilibrium (LD), and presence of repeated multilocus genotypes (MLG) were analyzed by using a total of seven statistics, to test the null hypothesis of panmixia (H0). For three populations, none of the seven statistics allowed to rejecting H0; for another one the low size did not allow us to conclude, and for the two others the tests have given contradictory results. Interestingly, apparent panmixia was only observed in very restricted areas, and was not observed when grouping populations distant of only two kilometers or more. Nevertheless it is worth stressing that for the statistic tests of "HWE", in order to minimize the type I error (i. e. incorrect rejection of a true H0), we used the Bonferroni correction (BC) known to considerably increase the type II error ( i. e. failure to reject a false H0). For the other tests (LD and MLG), we did not use BC and the risk of type II error in these cases was acceptable. Thus, these results should be considered as a good indicator of the existence of panmixia in wild environment but this must be confirmed on larger samples to reduce the risk of type II error.

AFLP polymorphisms allow high resolution genetic analysis of American Tegumentary Leishmaniasis agents circulating in Panama and other members of the Leishmania genus

American Tegumentary Leishmaniasis is caused by parasites of the genus Leishmania, and causes significant health problems throughout the Americas. In Panama, Leishmania parasites are endemic, causing thousands of new cases every year, mostly of the cutaneous form. In the last years, the burden of the disease has increased, coincident with increasing disturbances in its natural sylvatic environments. The study of genetic variation in parasites is important for a better understanding of the biology, population genetics, and ultimately the evolution and epidemiology of these organisms. Very few attempts have been made to characterize genetic polymorphisms of parasites isolated from Panamanian patients of cutaneous leishmaniasis. Here we present data on the genetic variability of local isolates of Leishmania, as well as specimens from several other species, by means of Amplified Fragment Length Polymorphisms (AFLP), a technique seldom used to study genetic makeup of parasites. We demonstrate that this technique allows detection of very high levels of genetic variability in local isolates of Leishmania panamensis in a highly reproducible manner. The analysis of AFLP fingerprints generated by unique selective primer combinations in L. panamensis suggests a predominant clonal mode of reproduction. Using fluorescently labeled primers, many taxon-specific fragments were identified which may show potential as species diagnostic fragments. The AFLP permitted a high resolution genetic analysis of the Leishmania genus, clearly separating certain groups among L. panamensis specimens and highly related species such as L. panamensis and L. guyanensis. The phylogenetic networks reconstructed from our AFLP data are congruent with established taxonomy for the genus Leishmania, even when using single selective primer combinations. Results of this study demonstrate that AFLP polymorphisms can be informative for genetic characterization in Leishmania parasites, at both intra and inter-specific levels.

Genetic modulation in Be-78 and Y Trypanosoma cruzi strains after long-term infection in Beagle dogs revealed by molecular markers

The genetic profile of Trypanosoma cruzi was evaluated in parasite populations isolated from Beagle dogs experimentally infected with Be-78 and Y strains that present distinct biological and genetic characteristics. Molecular characterization of the isolates obtained 30days and 2years after infection was carried out. For typing MLEE, sequence polymorphisms of the mitochondrial cytochrome oxidase subunit II gene (COII) and RAPD profiles were used. The profiles of MLEE were the same for the parental Be-78 strains as their respective isolates. However, changes of MLEE profile were observed in two T. cruzi isolates from dogs inoculated with Y strain. Changes in the mitochondrial DNA (COII) and RAPD profiles of the Y strain were also observed. The dendogram constructed by UPGMA with RAPD results indicated two major branches. Global data show that the genetic modulation in polyclonal strains during the long-term infection occurred and was strain-dependent. This study still suggests that each host (here each dog) harbors a determinate T. cruzi population that may change or be modulated throughout long-term infection. This might to hinder the observation of correlation between the genetics of T. cruzi and their biological properties and behavior in different host species due to the complexity of the parasite-host interaction in which probably the genetic background of both should be considered.

The genotypic structure of a multi-host bumblebee parasite suggests a role for ecological niche overlap

The genotypic structure of parasite populations is an important determinant of ecological and evolutionary dynamics of host-parasite interactions with consequences for pest management and disease control. Genotypic structure is especially interesting where multiple hosts co-exist and share parasites. We here analyze the natural genotypic distribution of Crithidia bombi, a trypanosomatid parasite of bumblebees (Bombus spp.), in two ecologically different habitats over a time period of three years. Using an algorithm to reconstruct genotypes in cases of multiple infections, and combining these with directly identified genotypes from single infections, we find a striking diversity of infection for both data sets, with almost all multi-locus genotypes being unique, and are inferring that around half of the total infections are resulting from multiple strains. Our analyses further suggest a mixture of clonality and sexuality in natural populations of this parasite species. Finally, we ask whether parasite genotypes are associated with host species (the phylogenetic hypothesis) or whether ecological factors (niche overlap in flower choice) shape the distribution of parasite genotypes (the ecological hypothesis). Redundancy analysis demonstrates that in the region with relatively high parasite prevalence, both host species identity and niche overlap are equally important factors shaping the distribution of parasite strains, whereas in the region with lower parasite prevalence, niche overlap more strongly contributes to the distribution observed. Overall, our study underlines the importance of ecological factors in shaping the natural dynamics of host-parasite systems.

Microsatellite marker analysis shows differentiation among Trypanosoma cruzi populations of peripheral blood and dejections of Triatoma infestans fed on the same chronic chagasic patients : microsatellite marker analysis and T. cruzi

To investigate whether Trypanosoma cruzi populations found in chagasic cardiopathic and non-cardiopathic patients are genetically differentiated, three molecular microsatellite markers were analysed. This analysis was also applied to compare T. cruzi samples from peripheral blood or dejections of Triatoma infestans fed on the blood of the same patients. In order to obtain the first objective, analyses of predominant T. cruzi genotypes were conducted using three approaches: a locus-by-locus analysis; a Fisher method across three loci; and analysis of molecular variance by Genepop and Arlequin programs. Only with one locus and on the blood samples was a significant differentiation detected among non-cardiopathic and cardiopathic groups, which was not confirmed by the other two methods. On the contrary, with the three approaches, it was found that T. cruzi clones present in the blood of patients are genetically differentiated from those detected in dejections of T. infestans fed on the same patients. Our results showed that the most frequent lineage both in blood as well as in triatomine dejection samples was TcI. No significant difference in T. cruzi lineage distribution was observed among chagasic cardiopathic and non-cardiopathic patients. The majority of the samples (50-60%) had only one T. cruzi clone (uniclonal) either in blood or dejection samples.

TcSNP: a database of genetic variation in Trypanosoma cruzi

The TcSNP database (http://snps.tcruzi.org) integrates information on genetic variation (polymorphisms and mutations) for different stocks, strains and isolates of Trypanosoma cruzi, the causative agent of Chagas disease. The database incorporates sequences (genes from the T. cruzi reference genome, mRNAs, ESTs and genomic sequences); multiple sequence alignments obtained from these sequences; and single-nucleotide polymorphisms and small indels identified by scanning these multiple sequence alignments. Information in TcSNP can be readily interrogated to arrive at gene sets, or SNP sets of interest based on a number of attributes. Sequence similarity searches using BLAST are also supported. This first release of TcSNP contains nearly 170 000 high-confidence candidate SNPs, derived from the analysis of annotated coding sequences. As new sequence data become available, TcSNP will incorporate these data, mapping new candidate SNPs onto the reference genome sequences.

Isolation and analysis of the genetic diversity of repertoires of VSG expression site containing telomeres from Trypanosoma brucei gambiense, T. b. brucei and T. equiperdum

Background

African trypanosomes (including Trypanosoma brucei) are unicellular parasites which multiply in the mammalian bloodstream. T. brucei has about twenty telomeric bloodstream form Variant Surface Glycoprotein (VSG) expression sites (BESs), of which one is expressed at a time in a mutually exclusive fashion. BESs are polycistronic transcription units, containing a variety of families of expression site associated genes (ESAGs) in addition to the telomeric VSG. These polymorphic ESAG families are thought to play a role in parasite-host adaptation, and it has been proposed that ESAG diversity might be related to host range. Analysis of the genetic diversity of these telomeric gene families has been confounded by the underrepresentation of telomeric sequences in standard libraries. We have previously developed a method to selectively isolate sets of trypanosome BES containing telomeres using Transformation associated recombination (TAR) cloning in yeast.

Results

Here we describe the isolation of repertoires of BES containing telomeres from three trypanosome subspecies: Trypanosoma brucei gambiense DAL 972 (causative agent of West-African trypanosomiasis), T. b. brucei EATRO 2340 (a nonhuman infective strain) and T. equiperdum STIB 818 (which causes a sexually transmitted disease in equines). We have sequenced and analysed the genetic diversity at four BES loci (BES promoter region, ESAG6, ESAG5 and ESAG2) from these three trypanosome BES repertoires.

Conclusion

With the exception of ESAG2, the BES sequence repertoires derived from T. b. gambiense are both less diverse than and nearly reciprocally monophyletic relative to those from T. b. brucei and T. equiperdum. Furthermore, although we find evidence for adaptive evolution in all three ESAG repertoires in T. b. brucei and T. equiperdum, only ESAG2 appears to be under diversifying selection in T. b. gambiense. This low level of variation in the T. b. gambiense BES sequence repertoires is consistent both with the relatively narrow host range of this subspecies and its apparent long-term clonality. However, our data does not show a clear correlation between size of trypanosome host range and either number of BESs or extent of ESAG genetic diversity.

Differentiation and gene flow among European populations of Leishmania infantum MON-1

BACKGROUND

Leishmania infantum is the causative agent of visceral and cutaneous leishmaniasis in the Mediterranean region, South America, and China. MON-1 L. infantum is the predominating zymodeme in all endemic regions, both in humans and dogs, the reservoir host. In order to answer important epidemiological questions it is essential to discriminate strains of MON-1.

METHODOLOGY/PRINCIPAL FINDINGS

We have used a set of 14 microsatellite markers to analyse 141 strains of L. infantum mainly from Spain, Portugal, and Greece of which 107 strains were typed by MLEE as MON-1. The highly variable microsatellites have the potential to discriminate MON-1 strains from other L. infantum zymodemes and even within MON-1 strains. Model- and distance-based analysis detected a considerable amount of structure within European L. infantum. Two major monophyletic groups-MON-1 and non-MON-1-could be distinguished, with non-MON-1 being more polymorphic. Strains of MON-98, 77, and 108 were always part of the MON-1 group. Among MON-1, three geographically determined and genetically differentiated populations could be identified: (1) Greece; (2) Spain islands-Majorca/Ibiza; (3) mainland Portugal/Spain. All four populations showed a predominantly clonal structure; however, there are indications of occasional recombination events and gene flow even between MON-1 and non-MON-1. Sand fly vectors seem to play an important role in sustaining genetic diversity. No correlation was observed between Leishmania genotypes, host specificity, and clinical manifestation. In the case of relapse/re-infection, only re-infections by a strain with a different MLMT profile can be unequivocally identified, since not all strains have individual MLMT profiles.

CONCLUSION

In the present study for the first time several key epidemiological questions could be addressed for the MON-1 zymodeme, because of the high discriminatory power of microsatellite markers, thus creating a basis for further epidemiological investigations.

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

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

Increased transmission potential of Leishmania major/Leishmania infantum hybrids

Development of Leishmania infantum/Leishmania major hybrids was studied in two sand fly species. In Phlebotomus papatasi, which supported development of L. major but not L. infantum, the hybrids produced heavy late-stage infections with high numbers of metacyclic promastigotes. In the permissive vector Lutzomyia longipalpis, all Leishmania strains included in this study developed well. Hybrids were found to express L. major lipophosphoglycan, apparently enabling them to survive in P. papatasi midgut. The genetic exchange of the hybrids thus appeared to have enhanced their transmission potential and fitness. A potentially serious consequence is the future spread of the hybrids using this peridomestic and antropophilic vector.

Transmembrane molecules for phylogenetic analyses of pathogenic protists: Leishmania-specific informative sites in hydrophilic loops of trans- endoplasmic reticulum N-acetylglucosamine-1-phosphate transferase

A sequence database was created for the Leishmania N-acetylglucosamine-1-phosphate transferase (nagt) gene from 193 independent isolates. PCR products of this single-copy gene were analyzed for restriction fragment length polymorphism based on seven nagt sequences initially available. We subsequently sequenced 77 samples and found 19 new variants (genotypes). Alignment of all 26 nagt sequences is gap free, except for a single codon addition or deletion. Phylogenetic analyses of the sequences allow grouping the isolates into three subgenera, each consisting of recognized species complexes, i.e., subgenus Leishmania (L. amazonensis-L. mexicana, L. donovani-L. infantum, L. tropica, L. major, and L. turanica-L. gerbilli), subgenus Viannia (L. braziliensis, L. panamensis), and one unclassified (L. enriettii) species. This hierarchy of grouping is also supported by sequence analyses of selected samples for additional single-copy genes present on different chromosomes. Intraspecies divergence of nagt varies considerably with different species complexes. Interestingly, species complexes with less subspecies divergence are more widely distributed than those that are more divergent. The relevance of this to Leishmania evolutionary adaptation is discussed. Heterozygosity of subspecies variants contributes to intraspecies diversity, which is prominent in L. tropica but not in L. donovani-L. infantum. This disparity is thought to result from the genetic recombination of the respective species at different times as a rare event during their predominantly clonal evolution. Phylogenetically useful sites of nagt are restricted largely to several extended hydrophilic loops predicted from hypothetical models of Leishmania NAGT as an endoplasmic reticulum transmembrane protein. In silico analyses of nagt from fungi and other protozoa further illustrate the potential value of this and, perhaps, other similar transmembrane molecules for phylogenetic analyses of single-cell eukaryotes.

Clonal propagation and the fast generation of karyotype diversity: An in vitro Leishmania model

In the present work we studied the karyotype stability during long-term in vitro maintenance in 3 cloned strains of Leishmania (Viannia) peruviana, Leishmania (Viannia) braziliensis and a hybrid between both species. Only the L. (V.) peruviana strain showed an unstable karyotype, even after subcloning. Four chromosomes were studied in detail, each of them characterized by homologous chromosomes of different size (heteromorphy). Variations in chromosome patterns during in vitro maintenance were rapid and discrete, involving loss of heteromorphy or appearance of additional chromosome size variants. The resulting pattern was not the same according to experimental conditions (subinoculation rate or incubation temperature), and interestingly, this was associated with differences in growth behaviour of the respective parasites. No change in total ploidy of the cells was observed by flow cytometry. We discuss several mechanisms that might account for this variation of chromosome patterns, but we favour the occurrence of aneuploidy, caused by aberrant chromosome segregation during mitosis. Our results provide insight into the generation of karyotype diversity in natural conditions and highlight the relativity of the clone concept in parasitology.

The trans-sialidase from Trypanosoma cruzi triggers apoptosis by target cell sialylation

The trans-sialidase, a modified sialidase that transfers sialyl residues among macromolecules, is a unique enzymatic activity expressed by some parasitic trypanosomes being essential for their survival in the mammalian host and/or in the insect vector. The enzyme from Trypanosoma cruzi, the agent of Chagas disease, is found in blood and able to act far from the infection site by inducing apoptosis in cells from the immune system. A central and still unsolved question is whether trans-sialidase-mediated addition or removal of sialic acid to/from host acceptor molecules is the event associated with the apoptosis induced by the enzyme. Here we show that lactitol, a competitive inhibitor that precluded the transference of the sialyl residue to endogenous acceptors but not the hydrolase activity of the enzyme, prevented ex vivo and in vivo the apoptosis caused by the trans-sialidase. By lectin histochemistry, the transference of sialyl residue to the cell surface was demonstrated in vivo and found associated with the apoptosis induction. The sialylation of the CD43 mucin, a key molecule involved in trans-sialidase-apoptotic process, was readily detected and also prevented by lactitol on thymocytes. Therefore, lesions induced by trans-sialidase on the immune system are due to the sialylation of endogenous acceptor molecules.

First report of genetic hybrids between two very divergent Leishmania species: Leishmania infantum and Leishmania major

The genus Leishmania includes many pathogenic species which are genetically very distant. The possibility of genetic exchange between different strains is still an important and debated question. Very few genetic hybrids (i.e., offspring of genetically dissimilar species) have been described in Leishmania. In this study, we report the first example of genetic hybrids occurring between two divergent Leishmania species, Leishmania infantum and Leishmania major. These two species have distinct geographical distributions and are transmitted by different vector species to different mammalian reservoir hosts. These hybrid strains were isolated in Portugal from immunocompromised patients and characterized by molecular and isoenzymatic techniques. These approaches showed that these chimeric strains probably contained the complete genome of both L. major and L. infantum. We believe this is the first report of genetic hybrids between such phylogenetically and epidemiologically distant species of Leishmania. This raises questions about the frequency of such cross-species genetic exchange in natural conditions, modalities of hybrid transmission, their long term maintenance as well as the consequences of these transfers on phenotypes such as drug resistance or pathogenicity.

Trypanosoma brucei DMC1 does not act in DNA recombination, repair or antigenic variation in bloodstream stage cells

Homologous recombination acts in the repair of cellular DNA damage and can generate genetic variation. Some of this variation provides a discrete purpose in the cell, although it can also be genome-wide and contribute to longer-term natural selection. In Trypanosoma brucei, a eukaryotic parasite responsible for sleeping sickness disease in sub-Saharan Africa, homologous recombination acts to catalyse antigenic variation, an immune evasion strategy involving switches in variant surface glycoprotein. In addition, T. brucei can undergo genetic exchange by homologous recombination in the tsetse vector, and some evidence suggests that this occurs by meiosis. Here, we show that T. brucei, Trypanosoma cruzi and Leishmania major each contain a single copy gene whose product is highly related to the eukaryotic meiosis-specific protein Dmc1, which is structurally and functionally related to Rad51. We show that T. brucei DMC1 is transcribed in the bloodstream stage of the parasite, where the gene can be mutated by reverse genetic disruption. DMC1 mutation does not, however, result in detectable alterations in DNA repair, recombination or antigenic variation efficiency in this life cycle stage.

Cutaneous leishmaniasis in the returning traveler

Infection with protozoan parasites of the genus Leishmania leads to a wide variety of clinical disease syndromes called leishmaniasis, or more appropriately the leishmaniases. The three major clinical syndromes are cutaneous leishmaniasis, mucosal leishmaniasis, and visceral leishmaniasis. All three of these syndromes have been documented in returning travelers. This article focuses on cutaneous leishmaniasis with some comment on mucosal leishmaniasis.

Distinct patterns of Trypanosoma cruzi infection in Leontopithecus rosalia in distinct Atlantic coastal rainforest fragments in Rio de Janeiro--Brazil

Previous studies on infection of Trypanosoma cruzi in the Poço das Antas Biological Reserve population of wild free-ranging Leontopithecus rosalia have shown the presence of genotype T. cruzi II, associated in Brazil with human disease. Herein, this study has been extended, the infection being evaluated in L. rosalia of 3 different tamarin populations, inhabiting distinct forest areas located in the same Atlantic Coastal Rainforest. Edentata, Marsupialia, Rodentia and Chiroptera were examined exclusively in the Poço das Antas Biological Reserve. Excluding Chiroptera, T. cruzi infection was found in all orders. Biochemical and molecular characterization demonstrated that golden lion tamarins maintained stable infections by T. cruzi II. The isolates from the other mammals corresponded to T. cruzi I, suggesting independent transmission cycles occurring among the sylvatic mammals inside Poço das Antas Biological Reserve. Significant differences in the infection patterns presented by the 3 populations of wild and captive-born golden lion tamarins were noticed. In Poço das Antas a considerably higher number of positive haemocultures from tamarins with positive serological titres was observed in comparison to those obtained from other areas. The implications for conservation and public health of an active sylvatic cycle in the Atlantic Coastal Rainforest of Rio de Janeiro are discussed.

Lack of correlation between in vitro susceptibility to Benznidazole and phylogenetic diversity of Trypanosoma cruzi, the agent of Chagas disease

Chagas disease remains an important health problem in Central and South America. Nitroimidazole derivative drugs like Benznidazole are commonly used to treat Trypanosoma cruzi infection. Natural variation of drug susceptibility between various T. cruzi stocks has been proposed as a possible explanation of treatment failure. Thus, the aim of this work was to determine potential correlations between in vitro Benznidazole susceptibility of different T. cruzi stocks and their genetic diversity. For this purpose, 16 natural stocks representing the overall genetic diversity of the parasite were analysed. Genetic characterisation was assessed by both random amplified polymorphic DNA (RAPD) and multilocus enzyme electrophoresis (MLEE) analyses. Drug activity was determined by two complementary methods, the MTT-PMS micro-method and FACs analysis. The 50% inhibitory concentrations (IC(50)s) were determined. Important variation of IC(50) values (7.3-16.9 microM) among stocks belonging to different discrete typing units (DTUs) was recorded. Further, correlation analysis showed that natural susceptibility to Benznidazole in T. cruzi expressed as IC(50) level was not related with its genetic structure represented by the different DTUs. These results are discussed in relation with the proposed hypothesis establishing a link between genetic diversity and biological behaviour in T. cruzi.

Multiclonal Leishmania braziliensis population structure and its clinical implication in a region of endemicity for American tegumentary leishmaniasis

In Corte de Pedra (CP), northeastern Brazil, Leishmania braziliensis causes three distinct forms of American tegumentary leishmaniasis (ATL). To test the hypothesis that strain polymorphism may be involved in this disease spectrum and accurately characterize the parasite population structure in CP, we compared one L. major, two non-CP L. braziliensis, one CP L. amazonensis, and 45 CP L. braziliensis isolates, obtained over a 10-year period from localized cutaneous, mucosal, and disseminated leishmaniasis patients, with randomly amplified polymorphic DNA (RAPD). Electrophoretic profiles were mostly unique across species. All typing protocols revealed polymorphism among the 45 CP L. braziliensis isolates, which displayed eight different RAPD patterns and greater than 80% overall fingerprint identity, attesting to the adequacy of the tools to assess strain variability in CP's geographically limited population of parasites. The dendrogram based on the sum of RAPD profiles of each isolate unveiled nine discrete typing units clustered into five clades. Global positioning showed extensive overlap of these clades in CP, precluding geographic sequestration as the mechanism of the observed structuralization. Finally, all forms of ATL presented a statistically significant difference in their frequencies among the clades, suggesting that L. braziliensis genotypes may be accompanied by specific disease manifestation after infection.

Immunization with recombinant paraflagellar rod protein induces protective immunity against Trypanosoma cruzi infection

In the present study, we have produced recombinant paraflagellar rod proteins (PFR) and report their use for successful vaccination of mice against Trypanosoma cruzi. This protection is associated with a highly polarized type 1 cytokine production profile. Additionally, we have analyzed the gene sequence encoding PFR-2 to determine the degree of conservation among seven highly diverse strains of T. cruzi, and found it to be highly conserved. The results presented here indicate that the PFR antigens are highly conserved, and immunization with rPFR-1, PFR-2, or an equimolar mix of the PFR-1, -2, and -3 proteins provides protective immunity against Trypanosoma cruzi.

Protozomics: trypanosomatid parasite genetics comes of age

Trypanosomatid protozoans cause important diseases of humans and their domestic livestock. Various molecular genetic tools are now allowing rapid progress in understanding many of the unique aspects of the molecular and cell biology of these organisms. Diploidy and the lack or difficulty of sexual crossing has been a challenge for forward genetics, but powerful selections and functional complementation have helped to overcome it in Leishmania. RNA interference has been adapted for forward genetics in trypanosomes, in which it is also a powerful tool for reverse genetics. Interestingly, the efficacy of different genetic tools has steered research into different aspects of the biology of these parasites.

Molecular biological applications in the diagnosis and control of leishmaniasis and parasite identification

Molecular biology is increasingly relevant to the diagnosis and control of infectious diseases. Information on DNA sequences has been extensively exploited for the development of polymerase chain reaction-based assays for the diagnosis of leishmaniasis and the identification of parasite species. It has also led to the use of cloned antigen for serodiagnosis. It is expected that the sequencing of the Leishmania major genome and the genomes of other Leishmania species will enable important progress in further improving diagnosis and control. The ability to use genome data to clone and sequence genes, which, when expressed, provide antigens for vaccine development, will increase the possibilities for rational vaccine development. Moreover, DNA on its own will provide the basis for the development of DNA vaccines that may overcome some of the problems encountered with protein-based vaccines. One of the greatest threats to parasite control is the development of drug resistance in parasites. Knowing the molecular basis of drug resistance and the ability to monitor its development with sensitive and specific DNA-based assays for 'resistance alleles' may aid maintaining the effectiveness of available anti-Leishmania drugs. Finally, techniques such as microarrays and nucleic acid sequence-based amplification will eventually allow rapid screening for specific parasite genotypes and assist in diagnostic and epidemiological studies.

Molecular epidemiology of Leishmania infantum on the island of Majorca: a comparison of phenotypic and genotypic tools

In the Mediterranean basin, Leishmania infantum is the causative agent of both visceral and cutaneous leishmaniasis, and is an important opportunistic parasite in patients infected with human immunodeficiency virus (HIV). The commonest method used to study the variability of Leishmania spp. is isoenzyme analysis. In addition to this, we employed 3 assays based on the polymerase chain reaction (PCR): random amplified polymorphic deoxyribonucleic acid (RAPD), intergenic region typing (IRT), based on the amplification of ribosomal ribonucleic acid internal transcribed spacers and restriction fragment length polymorphism (PCR-RFLP). We used 54 L. infantum stocks isolated from HIV co-infected patients, 38 isolated from dogs, 3 isolated from immunocompetent patients and 3 isolated from 1826 sand files in the island of Majorca (Spain), a closed ecological niche. Zymodemes MON-1 (70%), MON-24 (11%) and MON-34 (18%) were found among the human isolates, and MON-1 (95%) and MON-108 (5%) among those from dogs. RAPD and IRT could not discriminate among the strains as they all gave the same pattern, even when different zymodemes were examined. In contrast, PCR-RFLP was able to distinguish the strains and, furthermore, a dendrogram (unweighted pair group method with arithmetic average [UPGMA]) was constructed from the genetic distances derived from RFLP data. The Leishmania isolates from HIV-infected subjects formed a single cluster, supporting the existence of an artificial anthroponotic cycle previously proposed by our group, in which syringes have been substituted for sand flies, and in which certain clones have been spread among intravenous drug users. This contrasts with the clusters representing a zoonotic cycle, involving dogs, sand flies and both immunocompetent and immunocompromised humans.

The origin and evolution of the Leishmania donovani complex as inferred from a mitochondrial cytochrome oxidase II gene sequence

Members of the Leishmania donovani complex are parasites of the reticulo-endothelial system that are often associated with serious epidemics of a life threatening disease known as visceral leishmaniasis or kala-azar. Twenty-two Leishmania isolates representative of the geographical range of the parasite were analysed for sequence variations in their cytochrome oxidase II gene. In performing phylogenetic analysis, the maximum parsimonious, neighbour joining and maximum likelihood trees were congruent and produced a tree that differentiated between two clades conforming to the current classification of the species complex into two species: Leishmania donovani and Leishmania infantum. Furthermore, the molecular haplotypes were concordant, in general, with the isoenzyme data of the complex. The donovani isolates from the Sudan that possessed the most ancestral sequence were of a single haplotype that significantly resembled the sequence of Leishmania major. Our sequence data tallied with a general neutral model of sequence evolution with manifestations of weak selection. The data allowed an approximate dating of the origin of the complex to a period contemporary to or predating the spread of modern humans out of Africa.