GSK-3 kinase a putative therapeutic target in trypanosomatid parasites

Trypanosomatids are an important group of parasites that predominate in tropical and subtropical areas of the planet, which cause diseases that are classified as forgotten and neglected by the world health organization. In this group of parasites, we find Trypanosoma cruzi, Trypanosoma brucei, Trypanosoma brucei rhodesiense and Leishmania spp, for which there is no vaccine available, and its control has focused mainly on pharmacological treatment. Due to the poverty situation where these diseases are found and the biological complexity of these parasites, there are multiple variables to control, including the diversity of species, the complexity of their life cycles, drug resistance, cytotoxicity, the limited use in pregnant women, the high costs of treatment and the little-known pharmacological mechanisms of action, among others. It is therefore necessary to find new strategies and approaches for the treatment of these parasitic diseases. Among these new approaches is the rational search for new targets based on the allosteric inhibition of protein kinases, which have been little studied in trypanosomatids. Among these kinases, we find Glycogen Synthase Kinase-3 (GSK-3), a kinase of great pharmacological interest, which is under intense basic and clinical research by pharmaceutical companies for the treatment of cancer. This kinase, highly studied in the PI3K/AKT/mTOR pathway signaling in humans, has an orthologous gene in these parasites (GSK-3 s), which has proven to be essential for them in response to different challenges; Therefore, it is notable to increase research in this kinase in order to achieve a broad structural and functional characterization in the different species of trypanosomatids.

Cultivation of monoxenous trypanosomatids: A minireview

Trypanosomatids are obligatory parasites, some of which are responsible for important human and animal diseases, but the vast majority of trypanosomatids are restricted to invertebrate hosts. Isolation and in vitro cultivation of trypanosomatids from insect hosts enable their description, characterization, and subsequently genetic and genomic studies. However, exact nutritional requirements are still unknown for most trypanosomatids and thus very few defined media are available. This mini review provides information about the role of different ingredients, recommendations and advice on essential supplements and important physicochemical parameters of culture media with the aim of facilitating first attempts to cultivate insect-infesting trypanosomatids, with a focus on monoxenous trypanosomatids.

Prioritization of Trypanosoma brucei editosome protein interactions interfaces at residue resolution through proteome-scale network analysis

BACKGROUND

Trypanosoma brucei is the causative agent for trypanosomiasis in humans and livestock, which presents a growing challenge due to drug resistance. While identifying novel drug targets is vital, the process is delayed due to a lack of functional information on many of the pathogen's proteins. Accordingly, this paper presents a computational framework for prioritizing drug targets within the editosome, a vital molecular machinery responsible for mitochondrial RNA processing in T. brucei. Importantly, this framework may eliminate the need for prior gene or protein characterization, potentially accelerating drug discovery efforts.

RESULTS

By integrating protein-protein interaction (PPI) network analysis, PPI structural modeling, and residue interaction network (RIN) analysis, we quantitatively ranked and identified top hub editosome proteins, their key interaction interfaces, and hotspot residues. Our findings were cross-validated and further prioritized by incorporating them into gene set analysis and differential expression analysis of existing quantitative proteomics data across various life stages of T. brucei. In doing so, we highlighted PPIs such as KREL2-KREPA1, RESC2-RESC1, RESC12A-RESC13, and RESC10-RESC6 as top candidates for further investigation. This includes examining their interfaces and hotspot residues, which could guide drug candidate selection and functional studies.

CONCLUSION

RNA editing offers promise for target-based drug discovery, particularly with proteins and interfaces that play central roles in the pathogen's life cycle. This study introduces an integrative drug target identification workflow combining information from the PPI network, PPI 3D structure, and reside-level information of their interface which can be applicable to diverse pathogens. In the case of T. brucei, via this pipeline, the present study suggested potential drug targets with residue-resolution from RNA editing machinery. However, experimental validation is needed to fully realize its potential in advancing urgently needed antiparasitic drug development.

Frequent Parasitism of Apis mellifera by Trypanosomatids in Geographically Isolated Areas with Restricted Beekeeping Movements

Trypanosomatids form a group of high prevalence protozoa that parasitise honey bees, with Lotmaria passim as the predominant species worldwide. However, the knowledge about the ecology of trypanosomatids in isolated areas is limited. The Portuguese archipelagos of Madeira and Azores provide an interesting setting to investigate these parasites because of their geographic isolation, and because they harbour honey bee populations devoid of two major enemies: Varroa destructor and Nosema ceranae. Hence, a total of 661 honey bee colonies from Madeira and the Azores were analysed using different molecular techniques, through which we found a high prevalence of trypanosomatids despite the isolation of these islands. L. passim was the predominant species and, in most colonies, was the only one found, even on islands free of V. destructor and/or N. ceranae with severe restrictions on colony movements to prevent the spread of them. However, islands with V. destructor had a significantly higher prevalence of L. passim and, conversely, islands with N. ceranae did not shown any significant correlation with the trypanosomatid. Crithidia bombi was detected in Madeira and on three islands of the Azores, almost always coincident with L. passim. By contrast, Crithidia mellificae was not detected in any sample. A high-throughput sequencing analysis distinguished two main haplotypes of L. passim, which accounted for 98% of the total sequence reads. This work suggests that L. passim and C. bombi are parasites that have been associated with honey bees predating the spread of V. destructor and N. ceranae.

Trypanosomatids in honey bee colonies in Spain: A new specific qPCR method for specific quantification of Lotmaria passim, Crithidia mellificae and Crithidia bombi

Bee trypanosomatids have not been widely studied due to the original belief that these organisms were not pathogenic to honey bees. However, trypanosomatids have been linked to increased winter mortality in honey bee colonies in recent years and it has been shown that these pathogens can shorten a honey bee worker's lifespan in laboratory conditions. These studies found that this mortality corresponded to dose-dependent infection. Although Lotmaria passim is the most prevalent species worldwide, the natural load in colonies remains poorly investigated. Here we describe a new highly specific and sensitive qPCR method that allows the differentiation and quantification of the parasitic load of each of the three most common trypanosomatid species described to date in honey bee colonies: L. passim, Crithidia mellificae, and Crithidia bombi. We have used this new method to analyze honey bee colonies in central Spain and confirm that L. passim is the most common species and the one with higher parasitic loads in the colonies, which increased over the years, being higher in spring than in autumn. Crithidia mellificae was present along the study, with the highest prevalence in autumn 2019 and lately it was only found in non-quantifiable loads. Crithidia bombi was not detected in any of the colonies analyzed.

Design, synthesis and biological evaluation of antiparasitic dinitroaniline-ether phospholipid hybrids

A series of nine novel ether phospholipid-dinitroaniline hybrids were synthesized in an effort to deliver more potent antiparasitic agents with improved safety profile compared to miltefosine. The compounds were evaluated for their in vitro antiparasitic activity against L. infantum, L.donovani, L. amazonensis, L. major and L. tropica promastigotes, L. infantum and L. donovani intracellular amastigotes, Trypanosoma brucei brucei and against different developmental stages of Trypanosoma cruzi. The nature of the oligomethylene spacer between the dinitroaniline moiety and the phosphate group, the length of the side chain substituent on the dinitroaniline and the choline or homocholine head group were found to affect both the activity and toxicity of the hybrids. The early ADMET profile of the derivatives did not reveal major liabilities. Hybrid 3, bearing an 11-carbon oligomethylene spacer, a butyl side chain and a choline head group, was the most potent analogue of the series. It exhibited a broad spectrum antiparasitic profile against the promastigotes of New and Old World Leishmania spp., against intracellular amastigotes of two L. infantum strains and L. donovani, against T. brucei and against T. cruzi Y strain epimastigotes, intracellular amastigotes and trypomastigotes. The early toxicity studies revealed that hybrid 3 showed a safe toxicological profile while its cytotoxicity concentration (CC50) against THP-1 macrophages being >100 μM. Computational analysis of binding sites and docking indicated that the interaction of hybrid 3 with trypanosomatid α-tubulin may contribute to its mechanism of action. Furthermore, compound 3 was found to interfere with the cell cycle in T. cruzi epimastigotes, while ultrastructural studies using SEM and TEM in T. cruzi showed that compound 3 affects cellular processes that result in changes in the Golgi complex, the mitochondria and the parasite's plasma membrane. The snapshot pharmacokinetic studies showed low levels of 3 after 24 h following oral administration of 100 mg/Kg, while, its homocholine congener compound 9 presented a better pharmacokinetic profile.

Natural infection with Leishmania (Mundinia) martiniquensis supports Culicoides peregrinus (Diptera: Ceratopogonidae) as a potential vector of leishmaniasis and characterization of a Crithidia sp. isolated from the midges

The prevalence of autochthonous leishmaniasis in Thailand is increasing but the natural vectors that are responsible for transmission remain unknown. Experimental in vivo infections in Culicoides spp. with Leishmania (Mundinia) martiniquensis and Leishmania (Mundinia) orientalis, the major causative pathogens in Thailand, have demonstrated that biting midges can act as competent vectors. Therefore, the isolation and detection of Leishmania and other trypanosomatids were performed in biting midges collected at a field site in an endemic area of leishmaniasis in Tha Ruea and a mixed farm of chickens, goats, and cattle in Khuan Phang, Nakhon Si Thammarat province, southern Thailand. Results showed that Culicoides peregrinus was the abundant species (>84%) found in both locations and only cow blood DNA was detected in engorged females. Microscopic examination revealed various forms of Leishmania promastigotes in the foregut of several C. peregrinus in the absence of bloodmeal remnants, indicating established infections. Molecular identification using ITS1 and 3'UTR HSP70 type I markers showed that the Leishmania parasites found in the midges were L. martiniquensis. The infection rate of L. martiniquensis in the collected flies was 2% in Tha Ruea and 6% in Khuan Phang, but no L. orientalis DNA or parasites were found. Additionally, organisms from two different clades of Crithidia, both possibly new species, were identified using SSU rRNA and gGAPDH genes. Choanomastigotes and promastigotes of both Crithidia spp. were observed in the hindgut of the dissected C. peregrinus. Interestingly, midges infected with both L. martiniquensis and Crithidia were found. Moreover, four strains of Crithidia from one of the clades were successfully isolated into culture. These parasites could grow at 37°C in the culture and infect BALB/c mice macrophages but no multiplication was observed, suggesting they are thermotolerant monoxenous trypanosomatids similar to Cr. thermophila. These findings provide the first evidence of natural infection of L. martiniquensis in C. peregrinus supporting it as a potential vector of L. martiniquensis.

Shining the spotlight on the neglected: new high-quality genome assemblies as a gateway to understanding the evolution of Trypanosomatidae

BACKGROUND

Protists of the family Trypanosomatidae (phylum Euglenozoa) have gained notoriety as parasites affecting humans, domestic animals, and agricultural plants. However, the true extent of the group's diversity spreads far beyond the medically and veterinary relevant species. We address several knowledge gaps in trypanosomatid research by undertaking sequencing, assembly, and analysis of genomes from previously overlooked representatives of this protistan group.

RESULTS

We assembled genomes for twenty-one trypanosomatid species, with a primary focus on insect parasites and Trypanosoma spp. parasitizing non-human hosts. The assemblies exhibit sizes consistent with previously sequenced trypanosomatid genomes, ranging from approximately 18 Mb for Obscuromonas modryi to 35 Mb for Crithidia brevicula and Zelonia costaricensis. Despite being the smallest, the genome of O. modryi has the highest content of repetitive elements, contributing nearly half of its total size. Conversely, the highest proportion of unique DNA is found in the genomes of Wallacemonas spp., with repeats accounting for less than 8% of the assembly length. The majority of examined species exhibit varying degrees of aneuploidy, with trisomy being the most frequently observed condition after disomy.

CONCLUSIONS

The genome of Obscuromonas modryi represents a very unusual, if not unique, example of evolution driven by two antidromous forces: i) increasing dependence on the host leading to genomic shrinkage and ii) expansion of repeats causing genome enlargement. The observed variation in somy within and between trypanosomatid genera suggests that these flagellates are largely predisposed to aneuploidy and, apparently, exploit it to gain a fitness advantage. High heterogeneity in the genome size, repeat content, and variation in chromosome copy numbers in the newly-sequenced species highlight the remarkable genome plasticity exhibited by trypanosomatid flagellates. These new genome assemblies are a robust foundation for future research on the genetic basis of life cycle changes and adaptation to different hosts in the family Trypanosomatidae.

G-Quadruplexes as Key Transcriptional Regulators in Neglected Trypanosomatid Parasites

G-quadruplexes (G4s) are nucleic acid secondary structures that have been linked to the functional regulation of eukaryotic organisms. G4s have been extensively characterised in humans and emerging evidence suggests that they might also be biologically relevant for human pathogens. This indicates that G4s might represent a novel class of therapeutic targets for tackling infectious diseases. Bioinformatic studies revealed a high prevalence of putative quadruplex-forming sequences (PQSs) in the genome of protozoans, which highlights their potential roles in regulating vital processes of these parasites, including DNA transcription and replication. In this work, we focus on the neglected trypanosomatid parasites, Trypanosoma and Leishmania spp., which cause debilitating and deadly diseases across the poorest populations worldwide. We review three examples where G4-formation might be key to modulate transcriptional activity in trypanosomatids, providing an overview of experimental approaches that can be used to exploit the regulatory roles and relevance of these structures to fight parasitic infections.

Radial spoke protein 9 is necessary for axoneme assembly in Plasmodium but not in trypanosomatid parasites

Flagella are important for eukaryote cell motility, including in sperm, and are vital for life cycle progression of many unicellular eukaryotic pathogens. The "9+2" axoneme in most motile flagella comprises nine outer doublet and two central-pair singlet microtubules. T-shaped radial spokes protrude from the outer doublets towards the central pair and are necessary for effective beating. We asked if there were radial spoke adaptations associated with parasite lineage-specific properties in apicomplexans and trypanosomatids. Following an orthologue search for experimentally uncharacterised radial spoke proteins (RSPs), we identified and analysed RSP9. Trypanosoma brucei and Leishmania mexicana, have an extensive RSP complement including two divergent RSP9 orthologs, necessary for flagellar beating and swimming. Detailed structural analysis showed that neither ortholog is needed for axoneme assembly in Leishmania. In contrast, Plasmodium has a reduced set of RSPs including a single RSP9 ortholog. deletion of which in Plasmodium berghei leads to failure of axoneme formation, failed male gamete release, greatly reduced fertilisation and inefficient life cycle progression in the mosquito. This indicates contrasting selection pressures on axoneme complexity, likely linked with the different mode of assembly of trypanosomatid versus Plasmodium flagella.

An overview of the trypanosomatid (Kinetoplastida: Trypanosomatidae) parasites infecting several mammal species in Colombia

BACKGROUND

Trypanosomatids are among the most critical parasites for public health due to their impact on human, animal, and plant health. Diseases associated with these pathogens manifest mainly in poor and vulnerable populations, where social, environmental, and biological factors modulate the case incidence and geographical distribution.

METHODS

We used Sanger and amplicon-based next-generation sequencing (NGS) in samples from different mammals to identify trypanosomatid infections in several departments in Colombia. A total of 174 DNA samples (18 humans, 83 dogs, and 73 wild mammals) were analyzed by conventional PCR using a fragment of the heat shock protein 70 (Hsp70) gene and Sanger sequenced the positive samples. Twenty-seven samples were sent for amplicon-based NGS using the same gene fragment. Data obtained were used to perform diversity analyses.

RESULTS

One hundred and thirteen samples were positive for PCR by Hsp70 fragment; these corresponded to 22.1% Leishmania spp., 18.6% L. amazonensis, 9.7% L. braziliensis, 14.2% L. infantum, 8% L. panamensis, and 27.4% Trypanosoma cruzi. Comparison of the identified species by the two sequencing technologies used resulted in 97% concordance. Alpha and beta diversity indices were significant, mainly for dogs; there was an interesting index of coinfection events in the analyzed samples: different Leishmania species and the simultaneous presence of T. cruzi and even T. rangeli in one of the samples analyzed. Moreover, a low presence of L. braziliensis was observed in samples from wild mammals. Interestingly, to our knowledge, this is the first report of Leishmania detection in Hydrochaeris hydrochaeris (capybara) in Colombia.

CONCLUSIONS

The Hsp70 fragment used in this study is an optimal molecular marker for trypanosomatid identification in many hosts and allows the identification of different species in the same sample when amplicon-based sequencing is used. However, the use of this fragment for molecular diagnosis through conventional PCR should be carefully interpreted because of this same capacity to identify several parasites. This point is of pivotal importance in highly endemic countries across South America because of the co-circulation of different genera from the Trypanosomatidae family. The findings show an interesting starting point for One Health approaches in which coevolution and vector-host interactions can be studied.

Molecular Identification of Host Blood Meals and Detection of Blood Parasites in Culicoides Latreille (Diptera: Ceratopogonidae) Collected from Phatthalung Province, Southern Thailand

Five hundred and fifty-nine female biting midges were collected, and seventeen species in six subgenera (Avaritia, Haemophoructus, Hoffmania, Meijerehelea, Remmia, and Trithecoides) and two groups (Clavipalpis and Shortti) were identified. The dominant Culicoides species was C. peregrinus (30.94%), followed by C. subgenus Trithecoides. From blood meal analysis of engorged biting midges, they were found to feed on cows, dogs, pigs, and avians. The majority of blood preferences of biting midges (68%; 49/72) displayed a mixed pattern of host blood DNA (cow and avian). The overall non-engorged biting midge field infectivity rate was 1.44 % (7/487). We detected Leucocytozoon sp. in three Culicoides specimens, one from each species: C. fulvus, C. oxystoma, and C. subgenus Trithecoides. Crithidia sp. was found in two C. peregrinus specimens, and Trypanosoma sp. and P. juxtanucleare were separately found in two C. guttifer. More consideration should be paid to the capacity of biting midges to transmit pathogens such as avian haemosporidian and trypanosomatid parasites. To demonstrate that these biting midges are natural vectors of trypanosomatid parasites, additional research must be conducted with a greater number of biting midges in other endemic regions.

Trypanosoma cruzi and Leishmania spp. in rodents in a peri-urban area of Central Mexico

Rodents are one of the most relevant groups of mammals involved in the process of zoonotic disease transmission. Their ability to adapt to anthropized environments allows them to come into contact with humans with often negative consequences for the latter. The present study designed to detect the presence of Trypanosoma cruzi and Leishmania spp. in rodents living in the peri-urban area of Queretaro in central Mexico. This research was carried out during two seasons of collection of wild and domestic rodents, in three localities within the peri-urban area of the state of Queretaro. These collections were carried out during the dry season of February-May 2017 and in the rainy season of August-November 2017. Samples were obtained from the tail tip, from which DNA was purified using the DNeasy Blood & Tissue Kit. End-point PCR was used for the identification of Trypanosoma cruzi and Leishmania spp. A total of 82 rodents were caught, represented in three families, six genera and seven species, of which 29 (35.3%) were positive for Trypanosoma cruzi; 13 (15.8%) for Leishmania spp.; and 12 individuals presented co-infection with both parasites (14.6%). This study confirmed the presence of Trypanosoma cruzi and Leishmania spp. in synanthropic rodents in the peri-urban area of Queretaro, where Chagas and Leishmaniosis diseases are not considered endemic. It is necessary to continue researching for the presence of vectors, as well as for the detection of diseases caused by parasites in humans and thus be able to confirm the transmission cycle of Trypanosoma cruzi and Leishmania spp. in this central Mexican city.

Mechanism of Action and Implication of Naphthoquinone as Potent Anti-trypanosomal Drugs

Naphthoquinone is a heterocyclic moiety whose natural derivatives are present as bioactive compounds in many plants and have stimulated a resurgence of interest in the past decades due to their wide range of pharmacological activities. Naphthoquinone agents have dynamic pharmacophores and privileged sub-structures in the chemistry of medicine. They have received much interest in drug discovery as trypanocidal because naphthoquinone and their derivatives revealed massive significance potential against the trypanosomes. Among natural naphthoquinones, lapachol, β-lapachone and its α-isomer exhibited useful trypanocidal activities. Some naphthoquinones have already been used commercially as an antiparasitic agent. Several naphthoquinones with diverse structural motifs have been synthesized and evaluated mainly against Trypanosoma cruzi and some studies have also been reported against Trypanosoma brucei and Trypanosoma evansi. This review summarized various mechanisms of action of naphthoquinone like reductive activation of quinone by the production of the semiquinone, generation of reactive oxygen species and free radicals such as superoxide anion radical and H2O2, and oxidative stress in the parasite. The information assembled in this review will help to understand the mechanism behind the activity and may also be useful to find the bio-efficacy of naphthoquinone compounds upon substitution against trypanosomatids.

Analysis of domain organization and functional signatures of trypanosomatid keIF4Gs

Translation initiation is the first step in three essential processes leading to protein synthesis. It is carried out by proteins called translation initiation factors and ribosomes on the mRNA. One of the critical translation initiation factors in eukaryotes is eIF4G which is a scaffold protein that helps assemble translation initiation complexes that carry out translation initiation which ultimately leads to polypeptide synthesis. Trypanosomatids are a large family of kinetoplastids, some of which are protozoan parasites that cause diseases in humans through transmission by vectors. While the protein translation mechanisms in eukaryotes and prokaryotes are well understood, the protein translation factors and mechanisms in trypanosomatids are poorly understood necessitating further studies. Unlike other eukaryotes, trypanosomatids contain five eIF4G orthologues with diversity in length and sequences. Here, I have used bioinformatics tools to look at trypanosomatid keIF4G orthologue sequences and report that there are similarities and considerable differences in their domains/motifs organization and signature amino acid sequences that are required for different functions as compared to human eIF4G. My analysis suggests that there is likely to be considerable diversity and complexity in trypanosomatid keIF4G functions as compared to other eukaryotes.

Leishmania diversity in bats from an endemic area for visceral and cutaneous leishmaniasis in Southeastern Brazil

This study aimed to determine the occurrence of Leishmania infection in bats in urban and wild areas in an endemic municipality for visceral and cutaneous leishmaniasis in Minas Gerais, Brazil. Between April 2014 to April 2015, 247 bats were captured and classified into 26 species belonging to Phyllostomidae (90.7%), Vespertilionidae (8.1%) and Molossidae (1.2%) families. Blood samples from 247 bats were collected and submitted to nested-PCR, targeting the variable V7-V8 region of the SSU rRNA gene, followed by sequencing of the PCR product. The overall infection rate of Leishmania spp. in bats was 4.4%. Of the eleven bats infected, ten were frugivorous bats: Artibeus planirostris (8/11), Artibeus lituratus (1/11) and Artibeus cinereus (1/11) and one a nectarivorous bat (Glossophaga soricina). None of the individuals exhibited macroscopic alterations in the skin, spleen or liver. Phylogenetic analysis separated Leishmania species in clades corresponding to the subgenera Viannia, Leishmania, and Mundinia, and supported that the isolates characterized in the present study clustered closely with Leishmania (Viannia) sp., Leishmania (Leishmania) infantum and Leishmania (Leishmania) amazonensis. Here we report for the first time the bat Artibeus cinereus as a host of Leishmania (Leishmania) amazonensis. In the study we found that the mean abundance of bats did not differ in wild habitats and urban areas and that bat-parasite interactions were similarly distributed in the two environments. On the other hand, further studies should be conducted in more recent times to verify whether there have been changes in these parameters.

The Trypanosomatids Cell Cycle: A Brief Report

Trypanosomatids are protozoan parasites among which are the etiologic agents of various infectious diseases in humans, such as Trypanosoma cruzi (causative agent of Chagas disease), Trypanosoma brucei (causative agent of sleeping sickness), and species of the genus Leishmania (causative agents of leishmaniases). The cell cycle in these organisms presents a sequence of events conserved throughout evolution. However, these parasites also have unique characteristics that confer some peculiarities related to the cell cycle phases. This review compares general and peculiar aspects of the cell cycle in the replicative forms of trypanosomatids. Moreover, a brief discussion about the possible cross-talk between telomeres and the cell cycle is presented. Finally, we intend to open a discussion on how a profound understanding of the cell cycle would facilitate the search for potential targets for developing antiparasitic therapies that could help millions of people worldwide.

Update on the biological relevance of lysine acetylation as a novel drug target in trypanosomatids

The number of acetylated proteins identified from bacteria to mammals has grown exponentially in the last ten years and it is now accepted that acetylation is a key component in most eukaryotic signaling pathways, as important as phosphorylation. The enzymes involved in this process are well described in mammals; acetyltransferases and deacetylases are found inside and outside the nuclear compartment and have different regulatory functions. In trypanosomatids several of these enzymes have been described and are postulated to be novel antiparasitic targets for the rational design of drugs. In this review article we present an update of the most important known acetylated proteins in trypanosomatids analyzing the acetylomes available. Also, we summarize the information available regarding acetyltransferases and deacetylases in trypanosomes and their potential use as chemotherapeutic targets.

A nuclear enterprise: zooming in on nuclear organization and gene expression control in the African trypanosome

African trypanosomes are early divergent protozoan parasites responsible for high mortality and morbidity as well as a great economic burden among the world's poorest populations. Trypanosomes undergo antigenic variation in their mammalian hosts, a highly sophisticated immune evasion mechanism. Their nuclear organization and mechanisms for gene expression control present several conventional features but also a number of striking differences to the mammalian counterparts. Some of these unorthodox characteristics, such as lack of controlled transcription initiation or enhancer sequences, render their monogenic antigen transcription, which is critical for successful antigenic variation, even more enigmatic. Recent technological developments have advanced our understanding of nuclear organization and gene expression control in trypanosomes, opening novel research avenues. This review is focused on Trypanosoma brucei nuclear organization and how it impacts gene expression, with an emphasis on antigen expression. It highlights several dedicated sub-nuclear bodies that compartmentalize specific functions, whilst outlining similarities and differences to more complex eukaryotes. Notably, understanding the mechanisms underpinning antigen as well as general gene expression control is of great importance, as it might help designing effective control strategies against these organisms.

A recombinant protein (MyxoTLm) for the serological diagnosis of acute and chronic Trypanosoma vivax infection in cattle

Human trypanosomiases and animal trypanosomoses are caused by distinct protozoan parasites of the genus Trypanosoma. The etiological agents of bovine trypanosomosis (BT) are T. vivax, T. congolense, or T. brucei, whose acute infections are initially characterized by hyperthermia, following moderate to severe anemia, subcutaneous edema, lethargy, reduced milk production, progressive weight loss, enlarged lymph nodes, reproductive disorders and death. Animals that survive the acute phase might recover and progress to the chronic, often asymptomatic, phase of infection. Despite their low sensitivity due to the characteristic low parasitemia, simple and costless direct parasitological examinations are the preferred diagnostic methods for animals. Thus, most of the epidemiological studies of BT are based on serological techniques using crude antigen. In this study, we describe the use of the MyxoTLm recombinant protein as an antigen on serological assays. Anti-T. vivax IgM and anti-T. vivax IgG ELISA assays using purified MyxoTLm revealed specificity rates of 91.30 % and 95.65 % and sensitivity rates of 82.35 % and 88.23 %, respectively, being higher than reported for crude antigens. Also, MyxoTLm demonstrated a good performance to detect IgM (ROC curve area = 0.8568) and excellent performance to detect IgG (ROC curve area = 0.9565) when compared to a crude antigen. T. evansi crude antigen used in the indirect anti-T. vivax IgM ELISA reached 70.58 % sensitivity and 78.26 % specificity, and had a lower test performance (ROC curve area = 0.7363). When applied to the anti-T. vivax IgG ELISA, the crude antigen reached 82.35 % sensitivity and 69.56 % specificity, also presenting a low performance with area under the ROC curve of 0.7570. Therefore, the use of MyxoTLm as an antigen on serological diagnosis of BT revealed to increase the sensitivity and the specificity if compared to crude antigens.

Reproduction in Trypanosomatids: Past and Present

Simple Summary

The reproduction of trypanosomatids is a fundamental issue for host–parasite interaction, and its biological importance lies in knowing how these species acquire new defense mechanisms against the countermeasures imposed by the host, which is consistent with the theory of the endless race or the Red Queen hypothesis for the existence of meiotic sex. Moreover, the way these species re-produce may also be at the origin of novel and more virulent clades and is relevant from a thera-peutic or vaccination point of view, as sex may contribute to increased tolerance and even to the rapid acquisition of drug resistance mechanisms. Kinetoplastids are single-celled organisms, many of them being responsible for important parasitic diseases, globally termed neglected diseases, which are endemic in low-income countries. Leishmaniasis, African (sleeping sickness) and American trypanosomiasis (Chagas disease) caused by trypanosomatids are among the most ne-glected tropical scourges related to poverty and poor health systems. The reproduction of these microorganisms has long been considered to be clonal due to population genetic observations. However, there is increasing evidence of true sex and genetic exchange events under laboratory conditions. We would like to highlight the importance of this topic in the field of host/parasite in-terplay, virulence, and drug resistance.

Abstract

Diseases caused by trypanosomatids (Sleeping sickness, Chagas disease, and leishmaniasis) are a serious public health concern in low-income endemic countries. These diseases are produced by single-celled parasites with a diploid genome (although aneuploidy is frequent) organized in pairs of non-condensable chromosomes. To explain the way they reproduce through the analysis of natural populations, the theory of strict clonal propagation of these microorganisms was taken as a rule at the beginning of the studies, since it partially justified their genomic stability. However, numerous experimental works provide evidence of sexual reproduction, thus explaining certain naturally occurring events that link the number of meiosis per mitosis and the frequency of mating. Recent techniques have demonstrated genetic exchange between individuals of the same species under laboratory conditions, as well as the expression of meiosis specific genes. The current debate focuses on the frequency of genomic recombination events and its impact on the natural parasite population structure. This paper reviews the results and techniques used to demonstrate the existence of sex in trypanosomatids, the inheritance of kinetoplast DNA (maxi- and minicircles), the impact of genetic exchange in these parasites, and how it can contribute to the phenotypic diversity of natural populations.

Mitochondrial Ca2+ homeostasis in trypanosomes

Mitochondrial calcium ion (Ca2+) uptake is important for buffering cytosolic Ca2+ levels, for regulating cell bioenergetics, and for cell death and autophagy. Ca2+ uptake is mediated by a mitochondrial Ca2+ uniporter (MCU) and the discovery of this channel in trypanosomes has been critical for the identification of the molecular nature of the channel in all eukaryotes. However, the trypanosome uniporter, which has been studied in detail in Trypanosoma cruzi, the agent of Chagas disease, and T. brucei, the agent of human and animal African trypanosomiasis, has lineage-specific adaptations which include the lack of some homologues to mammalian subunits, and the presence of unique subunits. Here, we review newly emerging insights into the role of mitochondrial Ca2+ homeostasis in trypanosomes, the composition of the uniporter, its functional characterization, and its role in general physiology.

Effects of trypanocidal drugs on DNA synthesis: new insights into melarsoprol growth inhibition

Trypanothione is the primary thiol redox carrier in Trypanosomatids whose biosynthesis and utilization pathways contain unique enzymes that include suitable drug targets against the human parasites in this family. Overexpression of the rate-limiting enzyme, γ-glutamylcysteine synthetase (GSH1), can increase the intracellular concentration of trypanothione. Melarsoprol directly inhibits trypanothione and has predicted the effects on downstream redox biology, including ROS management and dNTP synthesis that require further investigation. Thus, we hypothesized that melarsoprol treatment would inhibit DNA synthesis, which was tested using BrdU incorporation assays and cell cycle analyses. In addition, we analysed the effects of eflornithine, which interfaces with the trypanothione pathway, fexinidazole, because of the predicted effects on DNA synthesis, and pentamidine as an experimental control. We found that melarsoprol treatment resulted in a cell cycle stall and a complete inhibition of DNA synthesis within 24 h, which were alleviated by GSH1 overexpression. In contrast, the other drugs analysed had more subtle effects on DNA synthesis that were not significantly altered by GSH1 expression. Together these findings implicate DNA synthesis as a therapeutic target that warrants further investigation in the development of antitrypanosomal drugs.

Extracellular Vesicles during TriTryps infection: Complexity and future challenges

The trypanosomatid pathogens Leishmania spp., Trypanosoma cruzi, and Trypanosoma brucei, currently grouped as TriTryps, have evolved through the time to overcome the upfront innate immune response and establish the infection in humans adapting many aspects of the parasite-cell host interaction. Extracellular vesicles (EVs) emerge as critical structures carrying different key molecules from parasites and target cells that interact continuously during infection. Current information regarding the structure and composition of these vesicles provide new insights into the primary role of TriTryps-EVs reviewed in this work. Expanding knowledge about these critical vesicular structures will promote advances in basic sciences and in translational applications controlling pathogenesis in the neglected tropical diseases caused by TriTryps.

Epitranscriptome machinery in Trypanosomatids: New players on the table?

Trypanosoma and Leishmania parasites cause devastating tropical diseases resulting in serious global health consequences. These organisms have complex life cycles with mammalian hosts and insect vectors. The parasites must, therefore, survive in different environments, demanding rapid physiological and metabolic changes. These responses depend upon regulation of gene expression, which primarily occurs posttranscriptionally. Altering the composition or conformation of RNA through nucleotide modifications is one posttranscriptional mechanism of regulating RNA fate and function, and modifications including N6-methyladenosine (m6A), N1-methyladenosine (m1A), N5-methylcytidine (m5C), N4-acetylcytidine (ac4C), and pseudouridine (Ψ), dynamically regulate RNA stability and translation in diverse organisms. Little is known about RNA modifications and their machinery in Trypanosomatids, but we hypothesize that they regulate parasite gene expression and are vital for survival. Here, we identified Trypanosomatid homologs for writers of m1A, m5C, ac4C, and Ψ and analyze their evolutionary relationships. We systematically review the evidence for their functions and assess their potential use as therapeutic targets. This work provides new insights into the roles of these proteins in Trypanosomatid parasite biology and treatment of the diseases they cause and illustrates that Trypanosomatids provide an excellent model system to study RNA modifications, their molecular, cellular, and biological consequences, and their regulation and interplay.

Field Isolation and Cultivation of Trypanosomatids from Insects

Monoxenous (one host) trypanosomatids from insects and other invertebrates can be introduced into axenic culture relatively easily and efficiently, allowing for their transfer from the field into the laboratory. Here we describe simple methods and alternative cultivation protocols, the wider application of which will allow substantial expansion of trypanosomatids available for research.

The ultimate fate determinants of drug induced cell-death mechanisms in Trypanosomatids

Chemotherapy constitutes a major part of modern-day therapy for infectious and chronic diseases. A drug is said to be effective if it can inhibit its target, induce stress, and thereby trigger an array of cell death pathways in the form of programmed cell death, autophagy, necrosis, etc. Chemotherapy is the only treatment choice against trypanosomatid diseases like Leishmaniasis, Chagas disease, and sleeping sickness. Anti-trypanosomatid drugs can induce various cell death phenotypes depending upon the drug dose and growth stage of the parasites. The mechanisms and pathways triggering cell death in Trypanosomatids serve to help identify potential targets for the development of effective anti-trypanosomatids. Studies show that the key proteins involved in cell death of trypanosomatids are metacaspases, Endonuclease G, Apoptosis-Inducing Factor, cysteine proteases, serine proteases, antioxidant systems, etc. Unlike higher eukaryotes, these organisms either lack the complete set of effectors involved in cell death pathways, or are yet to be deciphered. A detailed summary of the existing knowledge of different drug-induced cell death pathways would help identify the lacuna in each of these pathways and therefore open new avenues for research and thereby new therapeutic targets to explore. The cell death pathway associated complexities in metazoans are absent in trypanosomatids; hence this summary can also help understand the trigger points as well as cross-talk between these pathways. Here we provide an in-depth overview of the existing knowledge of these drug-induced trypanosomatid cell death pathways, describe their associated physiological changes, and suggest potential interconnections amongst them.

RPA-1 from Leishmania sp.: Recombinant Protein Expression and Purification, Molecular Modeling, and Molecular Dynamics Simulations Protocols

RPA is a conserved heterotrimeric complex and the major single-stranded DNA (ssDNA)-binding protein heterotrimeric complex, which in eukaryotes is formed by the RPA-1, RPA-2, and RPA-3 subunits. The main structural feature of RPA is the presence of the oligonucleotide/oligosaccharide-binding fold (OB-fold) domains, responsible for ssDNA binding and protein:protein interactions. Among the RPA subunits, RPA-1 bears three of the four OB folds involved with RPA-ssDNA binding, although in some organisms RPA-2 can also bind ssDNA. The OB-fold domains are also present in telomere end-binding proteins (TEBP), essential for chromosome end protection. RPA-1 from Leishmania sp., as well as RPA-1 from trypanosomatids, a group of early-divergent protozoa, shows some structural differences compared to higher eukaryote RPA-1. Also, RPA-1 from Leishmania sp., similar to TEBPs, may exert telomeric protective functions. Remarkably, different pieces of evidence have pointed out that trypanosomatids may not have OB fold-containing TEBPs. Moreover, recent data indicate that trypanosomatid RPA-1 may be considered a TEBP since it shares with TEBPs conserved functional and structural features. However, it is still unknown whether the RPA-1 protective telomeric role is exclusive to trypanosomatids or is also present in other primitive eukaryotes. Here, we describe a protocol to obtain highly purified and biologically active Leishmania amazonensis recombinant RPA-1, and to perform molecular modeling and molecular dynamics simulations methods which could be probably applied to functional and structural studies of homologous proteins in other primitive eukaryotes.

Taking a re-look at cap-binding signatures of the mRNA cap-binding protein eIF4E orthologues in trypanosomatids

Protein translation leading to polypeptide synthesis involves three distinct events, namely, initiation, elongation, and termination. Translation initiation is a multi-step process that is carried out by ribosomes on the mRNA with the assistance of a large number of proteins called translation initiation factors. Trypanosomatids are kinetoplastidas (flagellated protozoans), some of which cause acute disease syndromes in humans. Vector-borne transmission of protozoan parasites like Leishmania and Trypanosoma causes diseases that affect a large section of the world population and lead to significant morbidity and mortality. The mechanisms of translation initiation in higher eukaryotes are relatively well understood. However, structural and functional conservation of initiation factors in trypanosomatids are only beginning to be understood. Studies carried out so far suggests that at least in Leishmania and Trypanosoma eIF4E function may not be restricted to canonical translation initiation and some of the homologues may have alternate/non-canonical functions. Nonetheless, all of them bind the cap analogs, albeit with different efficiencies, indicating that this property may play an important role in the functionality of eIF4Es. Here, I give a brief background of trypanosomatid eIF4Es and revisit the cap-binding signatures of eIF4E orthologues in trypanosomatids, whose genome sequences are available, in detail, in comparison to human eIF4E1 and Trypanosoma cruzi eIF4E5, with an expanded list of members of this group in light of newer findings. The group 1 and 2 eIF4Es may use either a variation of heIF4E1 or T. cruzi eIF4E5 cap-4-binding signatures, while eIF4E5 and eIF4E6 use distinct amino acid contacts.

The Functioning of Na+-ATPases from Protozoan Parasites: Are These Pumps Targets for Antiparasitic Drugs?

The ENA ATPases (from exitus natru: the exit of sodium) belonging to the P-type ATPases are structurally very similar to the sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA); they exchange Na⁺ for H⁺ and, therefore, are also known as Na⁺-ATPases. ENA ATPases are required in alkaline milieu, as in the case for Aspergillus, where other transporters cannot mediate an uphill Na⁺ efflux. They are also important for salt tolerance, as described for Arabidopsis. During their life cycles, protozoan parasites might encounter a high pH environment, thus allowing consideration of ENA ATPases as possible targets for controlling certain severe parasitic diseases, such as Chagas' Disease. Phylogenetic analysis has now shown that, besides the types IIA, IIB, IIC, and IID P-type ATPases, there exists a 5th subgroup of ATPases classified as ATP4-type ATPases, found in Plasmodium falciparum and Toxoplasma gondii. In malaria, for example, some drugs targeting PfATP4 destroy Na⁺ homeostasis; these drugs, which include spiroindolones, are now in clinical trials. The ENA P-type (IID P-type ATPase) and ATP4-type ATPases have no structural homologue in mammalian cells, appearing only in fungi, plants, and protozoan parasites, e.g., Trypanosoma cruzi, Leishmania sp., Toxoplasma gondii, and Plasmodium falciparum. This exclusivity makes Na⁺-ATPase a potential candidate for the biologically-based design of new therapeutic interventions; for this reason, Na⁺-ATPases deserves more attention.

Two phylogenetically divergent isocitrate dehydrogenases are encoded in Leishmania parasites. Molecular and functional characterization of Leishmania mexicana isoenzymes with specificity towards NAD+ and NADP

Leishmania parasites are of great relevance to public health because they are the causative agents of various long-term and health-threatening diseases in humans. Dependent on the manifestation, drugs either require difficult and lengthy administration, are toxic, expensive, not very effective or have lost efficacy due to the resistance developed by these pathogens against clinical treatments. The intermediary metabolism of Leishmania parasites is characterized by several unusual features, among which whether the Krebs cycle operates in a cyclic and/or in a non-cyclic mode is included. Our survey of the genomes of Leishmania species and monoxenous parasites such as those of the genera Crithidia and Leptomonas (http://www.tritrypdb.org) revealed that two genes encoding putative isocitrate dehydrogenases (IDHs) -with distantly related sequences- are strictly conserved among these parasites. Thus, in this study, we aimed to functionally characterize the two leishmanial IDH isoenzymes, for which we selected the genes LmxM10.0290 (Lmex_IDH-90) and LmxM32.2550 (Lmex_IDH-50) from L. mexicana. Phylogenetic analysis showed that Lmex_IDH-50 clustered with members of Subfamily I, which contains mainly archaeal and bacterial IDHs, and that Lmex_IDH-90 was a close relative of eukaryotic enzymes comprised within Subfamily II IDHs. 3-D homology modeling predicted that both IDHs exhibited the typical folding motifs recognized as canonical for prokaryotic and eukaryotic counterparts, respectively. Both IDH isoforms displayed dual subcellular localization, in the cytosol and the mitochondrion. Kinetic studies showed that Lmex_IDH-50 exclusively catalyzed the reduction of NAD⁺, while Lmex_IDH-90 solely used NADP⁺ as coenzyme. Besides, Lmex_IDH-50 differed from Lmex_IDH-90 by exhibiting a nearly 20-fold lower apparent K_m value towards isocitrate (2.0 μM vs 43 μM). Our findings showed, for the first time, that the genus Leishmania differentiates not only from other trypanosomatids such as Trypanosoma cruzi and Trypanosoma brucei, but also from most living organisms, by exhibiting two functional homo-dimeric IDHs, highly specific towards NAD⁺ and NADP⁺, respectively. It is tempting to argue that any or both types of IDHs might be directly or indirectly linked to the Krebs cycle and/or to the de novo synthesis of glutamate. Our results about the biochemical and structural features of leishmanial IDHs show the relevance of deepening our knowledge of the metabolic processes in these pathogenic parasites to potentially identify new therapeutic targets.

Determination of Intracellular Ca2+ Concentration in the Human Pathogens Trypanosomatids Leishmania mexicana and Trypanosoma cruzi by the Use of the Fluorescent Ca2+ Indicator Fura-2

Ca²⁺ is an essential signaling messenger in all eukariotic cells, playing a pivotal role in many cellular functions as cell growth control (differentiation, fertilization and apoptosis), secretion, gene expression, enzyme regulation, among many others. This basic premise includes trypanosomatids as Trypanosoma cruzi and various species of Leishmania, the causative agents of Chagas disease and leishmaniasis respectively, where intracellular Ca²⁺ concentration ([Ca²⁺]_i) has been demonstrated to be finely regulated. Nevertheless [Ca²⁺]_i has been difficult to measure because of its very low cytoplasmic concentration (typically around 50-100 nM), when compared to the large concentration in the outside milieu (around 2 mM in blood). The development of intracellular fluorescent Ca²⁺-sensitive indicators has been of paramount importance to achieve this goal. The success was based on the synthesis of acetoximethylated derivative precursors, which allow the fluorescent molecules typically composed of many hydrophilic carboxyl groups responsible for its high affinity Ca²⁺-binding (and therefore very hydrophilic), to easily cross the plasma membrane. Once in the cell interior, unspecific esterases split the hydrophobic moiety from the fluorescent backbone structure, releasing the carboxyl groups, transforming it in turn to the acid form of the molecule, which remain trapped in the cytoplasm and regain its ability to fluoresce in a Ca²⁺-dependent manner. Among them, Fura-2 is by far the most used, because it is a ratiometric (two different wavelength excitation and one emission) Ca²⁺ indicator with a Ca²⁺ affinity compatible with the [Ca²⁺]_i. This protocol essentially consists in loading exponential phase parasites with Fura-2 and recording changes in [Ca²⁺]_i by mean of a double wavelength spectrofluorometer. This technique allows the acquisition of valuable information about [Ca²⁺]_i changes in real time, as a consequence of diverse stimuli or changes in conditions, as addition of drugs or different natural modulators.

Seropositivity for Trypanosoma cruzi and Leishmania mexicana in dogs from a metropolitan region of Central Mexico

Trypanosoma cruzi and Leishmania mexicana are parasites of humans and other mammals, causing American Trypanosomiasis and Cutaneous Leishmaniasis, respectively. Domestic dogs are considered key hosts for these parasites in the domicile and peridomicile cycles of transmission, due to their abundance and contact with human population. In Mexico, there are few studies that involve the study of infection with these parasites in dogs, and have only been carried out mainly in the endemic areas for these diseases. In the state of Querétaro (Mexico), infections with both parasites have been reported for dogs only from rural areas, with no records for the metropolitan zone. We analyzed the seropositivity to T. cruzi and L. mexicana in dogs from localities within of the metropolitan zone of Querétaro City in order to determine if these animals are exposed to these parasites and thus, could be an important part of the transmission cycle of these trypanosomatids in a densely populated urban region within the state of Querétaro, Mexico. Serum samples were collected from 303 dogs housed in the Animal Control centers of the municipalities of Querétaro and El Marques, analyzed by indirect ELISA and Western Blot using as an antigen the Iron Superoxide Dismutase (FeSODe) of the parasites. From the total serum samples, we detected 10.2% of seropositivity for T. cruzi and 2.9% for L. mexicana. Our results represent the first evidence of infection with T. cruzi in domestic dogs from the Metropolitan Zone of Querétaro, and the first record for L. mexicana in Central Mexico. Ongoing investigations seek to confirm the circulation of these parasites in the area to evaluate the risk associated to the human population.

Poly(ADP-ribose) metabolism in human parasitic protozoa

Poly(ADP-ribosyl)ation reactions constitute a post-translational protein modification synthesized in higher eukaryotes by a family of poly(ADP-ribose)polymerases (PARP) and catabolized mainly by poly(ADP-ribose) glycohydrolase (PARG). The best understood role of PARP is the maintenance of genomic integrity via the promotion of DNA repair that leads to cell survival when low levels of genotoxic stress occur. The participation of PARP in unleashing cell death at higher levels of damage has also been broadly studied. The biology of poly(ADP-ribosyl)ation in protozoan parasites, however, still remains a mystery. This review will examine the presence of the key enzyme involved in ADP-ribose polymer (PAR) metabolism in protozoan parasites associated with human diseases. Theoretical and experimental data obtained up to date have revealed the presence of PAR metabolism only in the trypanosomatids Trypanosoma cruzi and T. brucei, the apicomplexan Toxoplasma gondii and Entamoeba histolytica. T. cruzi and T. brucei, as opposed to humans and other organisms, have only one PARP and one PARG with subcellular localizations that are distinct from the ones described for their mammalian counterparts. The topics discussed in this review describe the first studies on PAR metabolism in trypanosomatids, specially the role of PAR on DNA damage response, cell cycle progression and cell death after genotoxic stimuli. The results described show differences in some aspects of PAR metabolism in trypanosomatids in comparison to other eukaryotes. New questions about the function of this metabolic pathway in the parasites under study are open and we hope it encourages the research community to explore this signaling pathway as a new possible target of clinical relevance in these and other disease-causing parasites.

Diversity and genome mapping assessment of disordered and functional domains in trypanosomatids

The proteins that have structural disorder exemplify a class of proteins which is part of a new frontier in structural biology that demands a new understanding of the paradigm of structure/function correlations. In order to address the location, relative distances and the functional/structural correlation between disordered and conserved domains, consensus disordered predictions were mapped together with CDD domains in Leishmania braziliensis M2904, Leishmania infantum JPCM5, Trypanosoma cruzi CL-Brener Esmeraldo-like, Trypanosoma cruzi Dm28c, Trypanosoma cruzi Sylvio X10, Blechomonas ayalai B08-376 and Paratrypanosoma confusum CUL13 predicted proteomes. Our results depicts the role of protein disorder in key aspects of parasites biology highlighting: a) statistical significant association between genome structural location of protein disordered consensus stretches and functional domains; b) that disordered protein stretches appear in greater percentage at upstream or downstream position of the predicted domain; c) a possible role of structural disorder in several gene expression, control points that includes but are not limited to: i) protein folding; ii) protein transport and degradation; and iii) protein modification. In addition, for values of protein with disorder content greater than 40%, a small percentage of protein binding sites in IDPs/IDRs, a higher hypothetical protein annotation frequency was observed than expected by chance and trypanosomatid multigene families linked with virulence are rich in protein with disorder content. SIGNIFICANCE: T. cruzi and Leishmania spp are the etiological agents of Chagas disease and leishmaniasis, respectively. Currently, no vaccine or effective drug treatment is available against these neglected diseases and the knowledge about the post-transcriptional and post-translational mechanisms of these organisms, which are key for this scenario, remain scarce. This study depicts the potential impact of the proximity between protein structural disorder and functional domains in the post-transcriptional regulation of pathogenic versus human non-pathogenic trypanosomatids. Our results revealed a significant statistical relationship between the genome structural locations of these two variables and disordered regions appearing more frequently at upstream or downstream positions of the CDD locus domain. This flexibility feature would maintain structural accessibility of functional sites for post-translational modifications, shedding light into this important aspect of parasite biology. This hypothesis is corroborated by the functional enrichment analysis of disordered proteins subset that highlight the involvement of this class of proteins in protein folding, protein transport and degradation and protein modification. Furthermore, our results pointed out: a) the impact of protein disorder in the process of genome annotation (proteins tend to be annotated as hypothetical when the disorder content reaches ~40%); b) that trypanosomatid multigenic families linked with virulence have a key protein disorder content.

A review of the systematics, species identification and diagnostics of the Trypanosomatidae using the maxicircle kinetoplast DNA: from past to present

The Trypanosomatid family are a diverse and widespread group of protozoan parasites that belong to the higher order class Kinetoplastida. Containing predominantly monoxenous species (i.e. those having only a single host) that are confined to invertebrate hosts, this class is primarily known for its pathogenic dixenous species (i.e. those that have two hosts), serving as the aetiological agents of the important neglected tropical diseases including leishmaniasis, American trypanosomiasis (Chagas disease) and human African trypanosomiasis. Over the past few decades, a multitude of studies have investigated the diversity, classification and evolutionary history of the trypanosomatid family using different approaches and molecular targets. The mitochondrial-like DNA of the trypanosomatid parasites, also known as the kinetoplast, has emerged as a unique taxonomic and diagnostic target for exploring the evolution of this diverse group of parasitic eukaryotes. This review discusses recent advancements and important developments that have made a significant impact in the field of trypanosomatid systematics and diagnostics in recent years.

Airyscan Superresolution Microscopy to Study Trypanosomatid Cell Biology

The recent introduction by Carl Zeiss Ltd. of the Airyscan detector module for their LSM880 confocal laser-scanning microscope has enabled routine superresolution microscopy to be combined with the advantages of confocal-based fluorescence imaging. Resulting enhanced spatial resolution in X, Y, and Z provides tractable opportunity to derive new insight into protein localization(s), organelle dynamics, and thence protein function within trypanosomatids or other organisms. Here, we describe methods for preparing slides, cells, and basic microscope setup for fluorescence imaging of trypanosomatids using the LSM-880 with Airyscan platform.

Proteins involved in the biosynthesis of lipophosphoglycan in Leishmania: a comparative genomic and evolutionary analysis

BACKGROUND

Leishmania spp. are digenetic parasites capable of infecting humans and causing a range of diseases collectively known as leishmaniasis. The main mechanisms involved in the development and permanence of this pathology are linked to evasion of the immune response. Crosstalk between the immune system and particularities of each pathogenic species is associated with diverse disease manifestations. Lipophosphoglycan (LPG), one of the most important molecules present on the surface of Leishmania parasites, is divided into four regions with high molecular variability. Although LPG plays an important role in host-pathogen and vector-parasite interactions, the distribution and phylogenetic relatedness of the genes responsible for its synthesis remain poorly explored. The recent availability of full genomes and transcriptomes of Leishmania parasites offers an opportunity to leverage insight on how LPG-related genes are distributed and expressed by these pathogens.

RESULTS

Using a phylogenomics-based framework, we identified a catalog of genes involved in LPG biosynthesis across 22 species of Leishmania from the subgenera Viannia and Leishmania, as well as 5 non-Leishmania trypanosomatids. The evolutionary relationships of these genes across species were also evaluated. Nine genes related to the production of the glycosylphosphatidylinositol (GPI)-anchor were highly conserved among compared species, whereas 22 genes related to the synthesis of the repeat unit presented variable conservation. Extensive gain/loss events were verified, particularly in genes SCG1-4 and SCA1-2. These genes act, respectively, on the synthesis of the side chain attached to phosphoglycans and in the transfer of arabinose residues. Phylogenetic analyses disclosed evolutionary patterns reflective of differences in host specialization, geographic origin and disease manifestation.

CONCLUSIONS

The multiple gene gain/loss events identified by genomic data mining help to explain some of the observed intra- and interspecies variation in LPG structure. Collectively, our results provide a comprehensive catalog that details how LPG-related genes evolved in the Leishmania parasite specialization process.

In silico prediction of a new lead compound targeting enolase of trypanosomatids through structure-based virtual screening and molecular dynamic studies

Enolase is one of the key glycolytic metalloenzyme in many organisms, and it is a potential therapeutic target including trypanosomatids. Sequence and structural analysis of enolase of Trypanosoma bruzi (TbENO), Trypanosoma cruzi (TcENO) and Leishmania donovani (LdENO) revealed conserved sequence pattern and structural features. Hence identification of an inhibitor against enolase of one trypanosomatid organism may have similar effects on enolase of homologous organisms belonging to same family. In the process to identify potent inhibitor compounds against TbENO by in silico methods, compounds containing the substructures of substrate, i.e. phosphoenolpyruvate (PEP) and the well-known inhibitors, fluoro-2-phosphono-acetohydroxamate (FPAH) and phosphono-acetohydroxamate (PAH), were collected. Virtual screening and induced fit docking studies were carried out to explore compounds that have better binding affinity than PEP and FPAH. PPPi was found to be the top hit exhibiting significant binding affinity towards enolase. Glide energy values of two other compounds represented by PubChem ID: 511392 and 101803456 was in good agreement with PEP and PAH. TbENO-PPPi complex was subjected to molecular orbital analysis and molecular dynamic studies by considering its remarkable binding affinity as it could be a potent inhibitor of enolase. Despite being an endogenous compound, based on the results of this study, we highlight PPPi to be a lead compound, and its structure can be treated as a model for further chemical modifications to obtain more potent antagonists.

Measurement of Energy States of the Trypanosomatid Mitochondrion

The evaluation of mitochondrial functionality is critical to interpret most biological data at the (eukaryotic) cellular level. For example, metabolism, cell cycle, epigenetic regulation, cell death mechanisms, autophagy, differentiation, and response redox imbalance are dependent on the mitochondrial state. In case of parasitic organisms, such as trypanosomatids, it is very often important to have information on mitochondrial functionality in order to assess the mechanisms of actions of drugs being proposed for therapy. In this chapter we present a set of methods that together allow to evaluate with some precision the mitochondrial functionality in Trypanosoma cruzi and Trypanosoma brucei. We discuss how to determine O2 consumption, mitochondrial inner membrane potential, ATP production, and the endogenous production of reactive oxygen species.

Isolation and Characterization of Acidocalcisomes from Trypanosomatids

Acidocalcisomes are membrane-bounded, electron-dense, acidic organelles, rich in calcium and polyphosphate. These organelles were first described in trypanosomatids and later found from bacteria to human cells. Some of the functions of the acidocalcisome are the storage of cations and phosphorus, participation in pyrophosphate (PPi) and polyphosphate (polyP) metabolism, calcium signaling, maintenance of intracellular pH homeostasis, autophagy, and osmoregulation. Isolation of acidocalcisomes is an important technique for understanding their composition and function. Here, we provide detailed subcellular fractionation protocols using iodixanol gradient centrifugations to isolate high-quality acidocalcisomes from Trypanosoma brucei, which are subsequently validated by electron microscopy, and enzymatic and immunoblot assays with organellar markers.

Horse flies (Diptera: Tabanidae) of three West African countries: A faunistic update, barcoding analysis and trypanosome occurrence

Horse flies (Diptera: Tabanidae) are of medical and veterinary importance since they transmit a range of pathogens. The horse fly fauna of tropical Africa is still poorly known, and in some geographical areas has not been studied for decades. This study summarizes the results of tabanid collections performed in three West African countries where only sparse data were previously available, the Central African Republic (CAR), Gabon and Liberia. Of 1093 collected specimens, 28 morphospecies and 26 genospecies belonging to six genera were identified, including the first findings of eleven morphospecies in the countries where horse flies were collected: Philoliche (Subpangonia) gravoti Surcouf, 1908 and Tabanus ianthinus Surcouf, 1907 are new records for Liberia; Ancala fasciata f. mixta (Surcouf, 1914), Tabanus fraternus Macquart, 1846, and T. triquetrornatus Carter, 1915 for CAR; Chrysops longicornis Macquart, 1838, Haematopota albihirta Karsch, 1887, H. bowdeni Oldroyd, 1952, and H. brucei Austen, 1908 for Gabon; and Tabanus secedens f. regnaulti Surcouf, 1912 and T. thoracinus Palisot de Beauvois, 1807 for Gabon and Liberia. Species identification of all 28 morphospecies based on morphological features was further supplemented by barcoding of cytochrome oxidase I (COI). Based on the COI sequences of 115 specimens representing 74 haplotypes, a phylogenetic tree was constructed to illustrate the relationships among the tabanid species found and to demonstrate their intra- and interspecific divergences. Our study enriches the current number of barcoded tabanids with another 22 genospecies. Based on the analysis of molecular data we question the taxonomic relevance of the morphological forms Ancala fasciata f. mixta and Tabanus secedens f. regnaulti. A parasitological survey based on nested PCR of 18S rRNA revealed a high (˜25%) prevalence of Trypanosoma theileri in the studied horse flies, accompanied by two species of monoxenous trypanosomatids, Crithidia mellificae and Blastocrithidia sp.

Application of Dithiocarbamates as Potential New Antitrypanosomatids-Drugs: Approach Chemistry, Functional and Biological

Dithiocarbamates represent a class of compounds that were evaluated in different biomedical applications because of their chemical versatility. For this reason, several pharmacological activities have already been attributed to these compounds, such as antiparasitic, antiviral, antifungal activities, among others. Therefore, compounds that are based on dithiocarbamates have been evaluated in different in vivo and in vitro models as potential new antimicrobials. Thus, the purpose of this review is to present the possibilities of using dithiocarbamate compounds as potential new antitrypanosomatids-drugs, which could be used for the pharmacological control of Chagas disease, leishmaniasis, and African trypanosomiasis.

Potential Drug Targets in the Pentose Phosphate Pathway of Trypanosomatids

The trypanosomatids, Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp, are causative agents of important human diseases such as African sleeping sickness, Chagas' disease and Leishmaniasis, respectively. The high impact of these diseases on human health and economy worldwide, the unsatisfactory available chemotherapeutic options and the absence of human effective vaccines, strongly justifies the search for new drugs. The pentose phosphate pathway has been proposed to be a viable strategy to defeat several infectious diseases, including those from trypanosomatids, as it includes an oxidative branch, important in the maintenance of cell redox homeostasis, and a non-oxidative branch in which ribose 5-phosphate and erythrose 4-phosphate, precursors of nucleic acids and aromatic amino acids, are produced. This review provides an overview of the available chemotherapeutic options against these diseases and discusses the potential of genetically validated enzymes from the pentose phosphate pathway of trypanosomatids to be explored as potential drug targets.

DiCre-Based Inducible Gene Expression

Induction of gene expression is a valuable approach for functional studies since it allows for the assessment of phenotypes without the need for clonal selection. Inducible expression can find a wide range of applications, from the study of essential genes to the characterization of overexpression of genes of interest. Here, we describe a detailed protocol for the use of the DiCre-based inducible gene expression system in Leishmania parasites. This is a tightly regulated induction system that allows for time- and dose-controlled expression of gene products, as rapidly as within 12 h.

Analysis of DNA Exchange Using Thymidine Analogs (ADExTA) in Trypanosoma cruzi

Trypanosoma cruzi is a protozoan parasite belonging to the Trypanosomatidae family. Although the trypanosomatids multiply predominantly by clonal generation, the presence of DNA exchange in some of them has been puzzling researchers over the years, mainly because it may represent a novel form that these organisms use to gain variability. Analysis of DNA Exchange using Thymidine Analogs (ADExTA) is a method that allows the in vitro detection and measurement of rates of DNA exchange, particularly in trypanosomatid cells, in a rapid and simple manner by indirect immunofluorescence assay (IFA). The method can be used to detect DNA exchange within one trypanosomatid lineage or among different lineages by paired analysis. The principle of this assay is based on the incorporation of two distinguishable halogenated thymidine analogs called 5'-chloro-2'-deoxyuridine (CldU) and 5'-iodo-2'-deoxyuridine (IdU) during DNA replication. After mixing the two cell cultures that had been previously incorporated with CldU and IdU separately, the presence of these unusual deoxynucleosides in the genome can be detected by specific antibodies. For this, a DNA denaturation step is required to expose the sites of thymidine analogs incorporated. Subsequently, a secondary reaction using fluorochrome-labeled antibodies will generate distinct signals under fluorescence analysis. By using this method, DNA exchange verification (i.e., the presence of both CldU and IdU in the same cell) is possible using a standard fluorescence microscope. It typically takes 2-3 days from the thymidine analogs incorporation to results. Of note, ADExTA is relatively cheap and does not require transfections or harsh genetic manipulation. These features represent an advantage when compared to other time-consuming protocols that demand DNA manipulation to introduce distinct drug-resistance markers in different cells for posterior selection.

Genomic comparison of Trypanosoma conorhini and Trypanosoma rangeli to Trypanosoma cruzi strains of high and low virulence

Background

Trypanosoma conorhini and Trypanosoma rangeli, like Trypanosoma cruzi, are kinetoplastid protist parasites of mammals displaying divergent hosts, geographic ranges and lifestyles. Largely nonpathogenic T. rangeli and T. conorhini represent clades that are phylogenetically closely related to the T. cruzi and T. cruzi-like taxa and provide insights into the evolution of pathogenicity in those parasites. T. rangeli, like T. cruzi is endemic in many Latin American countries, whereas T. conorhini is tropicopolitan. T. rangeli and T. conorhini are exclusively extracellular, while T. cruzi has an intracellular stage in the mammalian host.

Results

Here we provide the first comprehensive sequence analysis of T. rangeli AM80 and T. conorhini 025E, and provide a comparison of their genomes to those of T. cruzi G and T. cruzi CL, respectively members of T. cruzi lineages TcI and TcVI. We report de novo assembled genome sequences of the low-virulent T. cruzi G, T. rangeli AM80, and T. conorhini 025E ranging from ~ 21–25 Mbp, with ~ 10,000 to 13,000 genes, and for the highly virulent and hybrid T. cruzi CL we present a ~ 65 Mbp in-house assembled haplotyped genome with ~ 12,500 genes per haplotype. Single copy orthologs of the two T. cruzi strains exhibited ~ 97% amino acid identity, and ~ 78% identity to proteins of T. rangeli or T. conorhini. Proteins of the latter two organisms exhibited ~ 84% identity. T. cruzi CL exhibited the highest heterozygosity. T. rangeli and T. conorhini displayed greater metabolic capabilities for utilization of complex carbohydrates, and contained fewer retrotransposons and multigene family copies, i.e. trans-sialidases, mucins, DGF-1, and MASP, compared to T. cruzi.

Conclusions

Our analyses of the T. rangeli and T. conorhini genomes closely reflected their phylogenetic proximity to the T. cruzi clade, and were largely consistent with their divergent life cycles. Our results provide a greater context for understanding the life cycles, host range expansion, immunity evasion, and pathogenesis of these trypanosomatids.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5112-0) contains supplementary material, which is available to authorized users.

Maintenance of Trypanosoma cruzi, T. evansi and Leishmania spp. by domestic dogs and wild mammals in a rural settlement in Brazil-Bolivian border

Domestic dogs are considered reservoirs hosts for several vector-borne parasites. This study aimed to evaluate the role of domestic dogs as hosts for Trypanosoma cruzi, Trypanosoma evansi and Leishmania spp. in single and co-infections in the Urucum settlement, near the Brazil-Bolivian border. Additionally, we evaluated the involvement of wild mammals’ in the maintenance of these parasites in the study area. Blood samples of dogs (n = 62) and six species of wild mammals (n = 36) were collected in July and August of 2015. The infections were assessed using parasitological, serological and molecular tests. Clinical examination of dogs was performed and their feeding habits were noted. Overall, 87% (54/62) of sampled dogs were positive for at least one trypanosomatid species, in single (n = 9) and co-infections (n = 45). We found that 76% of dogs were positive for T. cruzi, four of them displayed high parasitemias demonstrated by hemoculture, including one strain types TcI, two TcIII and one TcIII/TcV. Around 73% (45/62) of dogs were positive to T. evansi, three with high parasitemias as seen by positive microhematocrit centrifuge technique. Of dogs sampled, 50% (31/62) were positive for Leishmania spp. by PCR or serology. We found a positive influence of (i) T. evansi on mucous pallor, (ii) co-infection by T. cruzi and Leishmania with onychogryphosis, and (iii) all parasites to skin lesions of sampled dogs. Finally, feeding on wild mammals had a positive influence in the Leishmania spp. infection in dogs. We found that 28% (5/18) coati Nasua nasua was co-infected for all three trypanosamatids, demonstrating that it might play a key role in maintenance of these parasites. Our results showed the importance of Urucum region as a hotspot for T. cruzi, T. evansi and Leishmania spp. and demonstrated that dogs can be considered as incidental hosts.

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Observation of high occurrence of dogs co-infected by trypanosomatids.

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Dogs infected by TcI, TcIII and TcIII/TcV.

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Nasua nasua is a key species in the sylvatic cycles of trypanosomatids.

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Direct effect of trypanosomatids' infection in clinical signs of dogs.

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Dogs as sentinels to human infection in the Brazil-Bolivian border.

Challenges in drug discovery targeting TriTryp diseases with an emphasis on leishmaniasis

Tritryps diseases are devastating parasitic neglected infections caused by Leishmania spp., Trypanosoma cruzi and Trypanosoma brucei subspecies. Together, these parasites affect more than 30 million people worldwide and cause high mortality and morbidity. Leishmaniasis comprises a complex group of diseases with clinical manifestation ranging from cutaneous lesions to systemic visceral damage. Antimonials, the first-choice drugs used to treat leishmaniasis, lead to high toxicity and carry significant contraindications limiting its use. Drug-resistant parasite strains are also a matter for increasing concern, especially in areas with very limited resources. The current scenario calls for novel and/or improvement of existing therapeutics as key research priorities in the field. Although several studies have shown advances in drug discovery towards leishmaniasis in recent years, key knowledge gaps in drug discovery pipelines still need to be addressed. In this review we discuss not only scientific and non-scientific bottlenecks in drug development, but also the central role of public-private partnerships for a successful campaign for novel treatment options against this devastating disease.

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Treatment options targeting TriTryp diseases are limited.

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Scientific and non-scientific bottlenecks need to be unveiled for the development of new treatments.

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Private and public sector partnership is key to allow advances in bench-to-bedside science.

An unexpected diversity of trypanosomatids in fecal samples of great apes

Charismatic great apes have been used widely and effectively as flagship species in conservation campaigns for decades. These iconic representatives of their ecosystems could also play a role as reservoirs of several zoonotic diseases. Recently it was demonstrated that African great apes can host Leishmania parasites (Kinetoplastea: Trypanosomatidae). Given that this finding raised a strong negative reaction from leishmania experts and the subsequent discussion did not lead to a clear resolution, we decided to analyze wild gorilla (Gorilla gorilla gorilla) and chimpanzee (Pan troglodytes troglodytes) fecal samples collected from the same area in Cameroon as in the original study. Fecal samples, used to circumvent the difficulties and ethics involved in obtaining blood samples from endangered wild apes, were screened by three different PCR assays for detection of Leishmania DNA. We did not detect any leishmania parasites in analyzed feces; however, sequencing of SSU rRNA revealed an unexpected diversity of free-living bodonids (Kinetoplastea: Bodonidae) and parasitic trypanosomatids (Kinetoplastea: Trypanosomatidae) other than Leishmania. A single detected Phytomonas species, found in chimpanzee feces, most likely originated from animal plant food. On the other hand, the presence of four free-living bodonid species and four parasitic insect monoxenous trypanosomatid, including two possible new species of the genus Herpetomonas, could be explained as ex post contamination of feces either from the environment or from flies (Diptera: Brachycera).

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We analyzed wild gorilla and chimpanzee fecal samples, from the area where a previous study detected Leishmania parasites.

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We detected leishmania DNA neither in great ape fecal samples nor in feces of experimentally infected rodents.

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We revealed unexpected diversity of bodonids, monoxenous and dixenous trypanosomatids other than Leishmania.