How monoxenous trypanosomatids revealed hidden feeding habits of their tsetse fly hosts.

Tsetse flies are well-known vectors of trypanosomes pathogenic for humans and livestock. For these strictly blood-feeding viviparous flies, the host blood should be the only source of nutrients and liquids, as well as any exogenous microorganisms colonising their intestine. Here we describe the unexpected finding of several monoxenous trypanosomatids in their gut. In a total of 564 individually examined Glossina (Austenia) tabaniformis (Westwood) (436 specimens) and Glossina (Nemorhina) fuscipes fuscipes (Newstead) (128 specimens) captured in the Dzanga-Sangha Protected Areas, Central African Republic, 24 (4.3%) individuals were infected with monoxenous trypanosomatids belonging to the genera Crithidia Léger, 1902; Kentomonas Votýpka, Yurchenko, Kostygov et Lukes, 2014; Novymonas Kostygov et Yurchenko, 2020; Obscuromonas Votýpka et Lukes, 2021; and Wallacemonas Kostygov et Yurchenko, 2014. Moreover, additional 20 (3.5%) inspected tsetse flies harboured free-living bodonids affiliated with the genera Dimastigella Sandon, 1928; Neobodo Vickerman, 2004; Parabodo Skuja, 1939; and Rhynchomonas Klebs, 1892. In the context of the recently described feeding behaviour of these dipterans, we propose that they become infected while taking sugar meals and water, providing indirect evidence that blood is not their only source of food and liquids.

Microorganisms as a Potential Source of Molecules to Control Trypanosomatid Diseases.

Trypanosomatids are the causative agents of leishmaniasis and trypanosomiasis, which affect about 20 million people in the world's poorest countries, leading to 95,000 deaths per year. They are often associated with malnutrition, weak immune systems, low quality housing, and population migration. They are generally recognized as neglected tropical diseases. New drugs against these parasitic protozoa are urgently needed to counteract drug resistance, toxicity, and the high cost of commercially available drugs. Microbial bioprospecting for new molecules may play a crucial role in developing a new generation of antiparasitic drugs. This article reviews the current state of the available literature on chemically defined metabolites of microbial origin that have demonstrated antitrypanosomatid activity. In this review, bacterial and fungal metabolites are presented; they originate from a range of microorganisms, including cyanobacteria, heterotrophic bacteria, and filamentous fungi. We hope to provide a useful overview for future research to identify hits that may become the lead compounds needed to accelerate the discovery of new drugs against trypanosomatids.

Trypanosomatid Flagellar Pocket from Structure to Function.

The trypanosomatids Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. are flagellate eukaryotic parasites that cause serious diseases in humans and animals. These parasites have cell shapes defined by a subpellicular microtubule array and all share a number of important cellular features. One of these is the flagellar pocket, an invagination of the cell membrane around the proximal end of the flagellum, which is an important organelle for endo/exocytosis. The flagellar pocket plays a crucial role in parasite pathogenicity and persistence in the host and has a great influence on cell morphogenesis and cell division. Here, we compare the morphology and function of the flagellar pockets between different trypanosomatids, with their life cycles and ecological niches likely influencing these differences.

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.

Lysophosphatidylcholine triggers cell differentiation in the protozoan parasite Herpetomonas samuelpessoai through the CK2 pathway.

BACKGROUND: Protozoa are distantly related to vertebrates but present some features of higher eukaryotes, making them good model systems for studying the evolution of basic processes such as the cell cycle. Herpetomonas samuelpessoai is a trypanosomatid parasite isolated from the hemipteran insect Zelus leucogrammus. Lysophosphatidylcholine (LPC) is implicated in the transmission and establishment of Chagas disease, whose etiological agent is Trypanosoma cruzi. LPC is synthesized by T. cruzi and its vectors, the hemipteran Rhodnius prolixus and Triatoma infestans. Platelet-activating factor (PAF), a phospholipid with potent and diverse physiological and pathophysiological actions, is a powerful inducer of cell differentiation in Herpetomonas muscarum muscarum and T. cruzi. The enzyme phospholipase A2 (PLA2) catalyzes the hydrolysis of the 2-ester bond of 3-sn-phosphoglyceride, transforming phosphatidylcholine (PC) into LPC. METHODS: In this study, we evaluated cellular differentiation, PLA2 activity and protein kinase CK2 activity of H. samuelpessoai in the absence and in the presence of LPC and PAF. RESULTS: We demonstrate that both PC and LPC promoted a twofold increase in the cellular differentiation of H. samuelpessoai, through CK2, with a concomitant inhibition of its cell growth. Intrinsic PLA2 most likely directs this process by converting PC into LPC. CONCLUSIONS: Our results suggest that the actions of LPC on H. samuelpessoai occur upon binding to a putative PAF receptor and that the protein kinase CK2 plays a major role in this process. Cartoon depicting a model for the synthesis and functions of LPC in Herpetomonas samuelpessoai, based upon our results regarding the role of LPC on the cell biology of Trypanosoma cruzi [28-32]. N nucleus, k kinetoplast, PC phosphatidylcholine, LPC lysophosphatidylcholine, PLA2 phospholipase A2, PAFR putative PAF receptor in trypanosomatids [65], CK2 protein kinase CK2 [16].

Unique Aspects of rRNA Biogenesis in Trypanosomatids.

Trypanosomatids are protozoan parasites that cycle between an insect and a mammalian host. The large-subunit rRNA of these organisms undergoes unique processing events absent in other eukaryotes. Recently, small nucleolar RNAs (snoRNAs) that mediate these specific cleavages were identified. Trypanosomatid rRNA is rich in RNA modifications such as 2'-O-methylation (Nm) and pseudouridylation (Ψ) that are also guided by these snoRNAs. A subset of these modifications is developmentally regulated and increased in the parasite form that propagates in the mammalian host. Such hypermodification contributes the temperature adaptation and hence infectivity during cycling of the parasite. rRNA processing and modification should be considered promising drug targets for fighting the diseases caused by these parasites.

More than Microtubules: The Structure and Function of the Subpellicular Array in Trypanosomatids.

The subpellicular microtubule array defines the wide range of cellular morphologies found in parasitic kinetoplastids (trypanosomatids). Morphological studies have characterized array organization, but little progress has been made towards identifying the molecular mechanisms that are responsible for array differentiation during the trypanosomatid life cycle, or the apparent stability and longevity of array microtubules. In this review, we outline what is known about the structure and biogenesis of the array, with emphasis on Trypanosoma brucei, Trypanosoma cruzi, and Leishmania, which cause life-threatening diseases in humans and livestock. We highlight unanswered questions about this remarkable cellular structure that merit new consideration in light of our recently improved understanding of how the 'tubulin code' influences microtubule dynamics to generate complex cellular structures.

Trypanosomatid parasites infecting managed honeybees and wild solitary bees.

The parasite Crithidia mellificae (Kinetoplastea: Trypanosomatidae) infects honeybees, Apis mellifera. No pathogenic effects have been found in individual hosts, despite positive correlations between infections and colony mortalities. The solitary bee Osmia cornuta might constitute a host, but controlled infections are lacking to date. Here, we challenged male and female O. cornuta and honeybee workers in laboratory cages with C. mellificae. No parasite cells were found in any control. Parasite numbers increased 6.6 fold in honeybees between days 6 and 19 p.i. and significantly reduced survival. In O. cornuta, C. mellificae numbers increased 2-3.6 fold within cages and significantly reduced survival of males, but not females. The proportion of infected hosts increased in O. cornuta cages with faeces, but not in honeybee cages without faeces, suggesting faecal - oral transmission. The data show that O. cornuta is a host of C. mellificae and suggest that males are more susceptible. The higher mortality of infected honeybees proposes a mechanism for correlations between C. mellificae infections and colony mortalities.

Development of Phytomonas lipae sp. n. (Kinetoplastea: Trypanosomatidae) in the true bug Coreus marginatus (Heteroptera: Coreidae) and insights into the evolution of life cycles in the genus Phytomonas.

Here we described a new trypanosomatid species, Phytomonas lipae, parasitizing the dock bug Coreus marginatus based on axenic culture and in vivo material. Using light and electron microscopy we characterized the development of this flagellate in the intestine, hemolymph and salivary glands of its insect host. The intestinal promastigotes of Phytomonas lipae do not divide and occur only in the anterior part of the midgut. From there they pass into hemolymph, increasing in size, and then to salivary glands, where they actively proliferate without attachment to the host's epithelium and form infective endomastigotes. We conducted molecular phylogenetic analyses based on 18s rRNA, gGAPDH and HSP83 gene sequences, of which the third marker performed the best in terms of resolving phylogenetic relationships within the genus Phytomonas. Our inference demonstrated rather early origin of the lineage comprising the new species, right after that of P. oxycareni, which represents the earliest known branch within the Phytomonas clade. This allowed us to compare the development of P. lipae and three other Phytomonas spp. in their insect hosts and reconstruct the vectorial part of the life cycle of their common ancestor.

Trypanosomatids Are Much More than Just Trypanosomes: Clues from the Expanded Family Tree.

Trypanosomes and leishmanias are widely known parasites of humans. However, they are just two out of several phylogenetic lineages that constitute the family Trypanosomatidae. Although dixeny - the ability to infect two hosts - is a derived trait of vertebrate-infecting parasites, the majority of trypanosomatids are monoxenous. Like their common ancestor, the monoxenous Trypanosomatidae are mostly parasites or commensals of insects. This review covers recent advances in the study of insect trypanosomatids, highlighting their diversity as well as genetic, morphological and biochemical complexity, which, until recently, was underappreciated. The investigation of insect trypanosomatids is providing an important foundation for understanding the origin and evolution of parasitism, including colonization of vertebrates and the appearance of human pathogens.

UDP-glycosyltransferase genes in trypanosomatid genomes have diversified independently to meet the distinct developmental needs of parasite adaptations.

BACKGROUND: Trypanosomatid parasites such as Trypanosoma spp. and Leishmania spp. are a major source of infectious disease in humans and domestic animals worldwide. Fundamental to the host-parasite interactions of these potent pathogens are their cell surfaces, which are highly decorated with glycosylated proteins and other macromolecules. Trypanosomatid genomes contain large multi-copy gene families encoding UDP-dependent glycosyltransferases (UGTs), the primary role of which is cell-surface decoration. Here we report a phylogenetic analysis of UGTs from diverse trypanosomatid genomes, the aim of which was to understand the origin and evolution of their diversity. RESULTS: By combining phylogenetics with analyses of recombination, and selection, we compared UGT repertoire, genomic context and sequence evolution across 19 trypanosomatids. We identified a UGT lineage present in stercorarian trypanosomes and a free-living kinetoplastid Bodo saltans that likely represents the ancestral state of this gene family. The phylogeny of parasite-specific genes shows that UGTs repertoire in Leishmaniinae and salivarian trypanosomes has expanded independently and with distinct evolutionary dynamics. In the former, the ancestral UGT repertoire was organised in a tandem array from which sporadic transpositions to telomeric regions occurred, allowing expansion most likely through telomeric exchange. In the latter, the ancestral UGT repertoire was comprised of seven subtelomeric lineages, two of which have greatly expanded potentially by gene transposition between these dynamic regions of the genome. CONCLUSIONS: The phylogeny of UGTs confirms that they represent a substantial parasite-specific innovation, which has diversified independently in the distinct trypanosomatid lineages. Nonetheless, developmental regulation has been a strong driver of UGTs diversification in both African trypanosomes and Leishmania.

Metal- and metalloid-containing drugs for the treatment of trypanosomatid diseases.

The trypanosomatid-induced diseases are considered as neglected, because the countries where they kill people are not important markets for western big pharmaceutical companies. However, recently some effort has been made to translate the use of already known drugs to neglected infectious disease. Although many metals are essential to life, many disorders affecting metal homeostasis and bioavailability are responsible for several human diseases. Metals can be toxic even at very low concentrations and semimetals are classified as toxic and dangerous for the environment. However, metal- and metalloid-based therapeutic drugs have existed for centuries. Some of them, as antimony and arsenic compounds, are still the first line drugs used for the treatment of leishmaniasis and trypanosomiases in developing countries. Other metal complexes (as those of Ag, Pt, Pd and Au), already present in the market for cancer therapies or to cure bacterial infection or for anti-inflammatory treatments, have been proposed also against the vector-borne infections caused by trypanosomatids. The use of novel approaches based on nanotechnologies, allowing selective targeting, may represent a promising strategy to decrease the toxicity of these drugs.

Quantitative PCR assessment of Lotmaria passim in Apis mellifera colonies co-infected naturally with Nosema ceranae.

A recently described trypanosomatid species Lotmaria passim and the microsporidium Nosema ceranae infect the honey bee (Apis mellifera), but the interspecific dynamic of these two common gut parasites is unknown. In this study, a real-time qPCR assay was developed to enable the specific detection and quantification of L. passim. The annual dynamics of N. ceranae and L. passim infections were evaluated in ten A. mellifera colonies naturally infected with both parasites at one apiary in Serbia from March 2016 to March 2017. Ten samples (60 bees abdomens) were taken from each colony on 8 sampling occasions. L. passim infection level was evaluated with qPCR, while N. ceranae infection was measured by spore counts. N. ceranae infection level was significantly higher in comparison with that of L. passim (spore or cell equivalents/bee, respectively). Significant positive correlation between infection levels of the parasite species indicates their similar annual dynamics, whilst the differences in the levels of infection between particular months point to a seasonal pattern in the incidence of both parasites. The assay which has been developed and validated creates opportunity for detailed study of L. passim infection kinetics and the improvement in the management practices in beekeeping related to these two parasites.

Life cycle of Blastocrithidia papi sp. n. (Kinetoplastea, Trypanosomatidae) in Pyrrhocoris apterus (Hemiptera, Pyrrhocoridae).

Blastocrithidia papi sp. n. is a cyst-forming trypanosomatid parasitizing firebugs (Pyrrhocoris apterus). It is a member of the Blastocrithidia clade and a very close relative of B. largi, to which it is almost identical through its SSU rRNA gene sequence. However, considering the SL RNA gene these two species represent quite distinct, not even related typing units. Morphological analysis of the new species revealed peculiar or even unique features, which may be useful for future taxonomic revision of the genus Blastocrithidia. These include a breach in the microtubular corset of rostrum at the site of contact with the flagellum, absence of desmosomes between flagellum and rostrum, large transparent vacuole near the flagellar pocket, and multiple vacuoles with fibrous content in the posterior portion of the cell. The study of the flagellates' behavior in the host intestine revealed that they may attach both to microvilli of enterocytes using swollen flagellar tip and to extracellular membranes layers using hemidesmosomes of flagellum. Laboratory experiments on B. papi transmission in P. apterus demonstrated that the parasite may be transmitted vertically (via contaminated surface of eggs) and horizontally (via contaminated substrate and/or necrophagy). We argue that the parasite exploits transmission mechanisms intended for obligate bacterial symbionts of P. apterus.

Ribosome Assembly in Trypanosomatids: A Novel Therapeutic Target.

In Liu et al., the authors present a 2.5-Å structure of the Trypanosoma cruzi 60S ribosomal subunit and propose a model for the stepwise assembly of the large-subunit ribosomal RNA (rRNA). Based on this study, we discuss how the unique features of trypanosomatid ribosome assembly offer potential drug targets.

Absence of Leishmaniinae and Nosematidae in stingless bees.

Bee pollination is an indispensable component of global food production and plays a crucial role in sustainable agriculture. The worldwide decline of bee populations, including wild pollinators, poses a threat to this system. However, most studies to date are situated in temperate regions where Apini and Bombini are very abundant pollinators. Tropical and subtropical regions where stingless bees (Apidae: Meliponini) are generally very common, are often overlooked. These bees also face pressure due to deforestation and agricultural intensification as well as the growing use and spread of exotic pollinators as Apis mellifera and Bombus species. The loss or decline of this important bee tribe would have a large impact on their provided ecosystem services, in both wild and agricultural landscapes. The importance of pollinator diseases, which can contribute to decline, has not been investigated so far in this bee tribe. Here we report on the first large pathogen screening of Meliponini species in southern Brazil. Remarkably we observed that there was an absence of Leishmaniinae and Nosematidae, and a very low occurrence of Apicystis bombi. Our data on disease prevalence in both understudied areas and species, can greatly improve our knowledge on the distribution of pathogens among bee species.

Nectar chemistry mediates the behavior of parasitized bees: consequences for plant fitness.

Plants produce an array of secondary metabolites that play important ecological roles as anti-herbivore and anti-pathogen defenses. Many herbivores experience physiological costs when they consume secondary metabolites, yet some also benefit, for example when these chemicals confer resistance to parasites and predators. Secondary metabolites are often present in nectar and pollen, which is paradoxical given that floral rewards are important in the attraction of mutualists rather than deterrence of antagonists. Motivated by studies of interactions among plants, herbivores, and parasites, as well as research showing that secondary metabolites can reduce bee disease, we characterized the occurrence of two iridoid glycosides, aucubin and catalpol, in floral rewards and other tissues of the bee pollinated plant, Chelone glabra. We then experimentally investigated effects of nectar iridoid glycoside concentrations on the foraging behavior of bumble bee pollinators naturally afflicted by a parasitoid fly and a protozoan intestinal parasite, and subsequent effects on an estimate of plant reproduction. We found that floral nectar had lower iridoid glycoside concentrations than leaves, pollen, and corollas, and that, compared to those plant parts, the relative ratio of the two primary iridoid glycosides, aucubin and catalpol, was reversed in nectar. Whether bees carried parasitoid fly larvae did not affect their response to nectar chemistry; however, there was a significant interaction between protozoan parasite infection and nectar treatment, with infected bees foraging longer at flowers with high compared to low nectar iridoid glycoside concentrations. Parasitized bees were also more likely to return to inflorescences with high iridoid glycoside nectar. Consequently, flowers in the high iridoid glycoside nectar treatment donated significantly more pollen to conspecific stigmas than did flowers in the low iridoid glycoside treatment, suggesting an increase in male plant fitness. Taken together, these results demonstrate that nectar secondary metabolites can mediate the behavior of pollinators with subsequent benefits for estimates of plant reproduction.

High Frequency of Trypanosoma congolense Savannah Type (Kinetoplastida: Trypanosomatidae) Among Tsetse Flies (Diptera: Glossinidae) in a Historic Trypanosoma Foci in North-Eastern Gabon: Preliminary Study [corrected].

Human African trypanosomiasis became a neglected disease after the 1960s, when case numbers dropped dramatically. It again became a public health problem in sub-Saharan Africa at the end of the 1990s, when new cases were reported, notably in Central Africa, and specifically in Gabon, where historic foci existed and new cases have been reported. Therefore, the present study reports on an entomological survey conducted in May 2012 to determine the pathogenic trypanosome infection rate in tsetse flies and characterize the diversity of Trypanosoma species in the Ivindo National Park (INP) in northeastern Gabon. Nine Vavoua traps were used to catch tsetse over a 7-days period. All tsetse flies captured were identified to species, dissected, and trypanosome species identified using polymerase chain reaction (PCR). In total, 160 tsetse flies were analyzed, including Glossina palpalis palpalis, Glossina fusca congolense, and Glossina tachinoïdes The trypanosome infection rate of the flies was 6.3 and 31.9% using microscopy and PCR, respectively. The species identified were Trypanosoma congolense savannah type, Trypanosoma brucei brucei, Trypanosoma brucei gambiense, Trypanosoma vivax, and Trypanosoma congolense forest type. Trypanosoma risk index was 0.75 and 7.05 for humans and for animals, respectively. This study illustrates the diversity of Trypanosoma species infecting the tsetse flies in the INP. The simultaneous occurrence of Trypanosoma and tsetse from the palpalis group may suggest that the reservoirs of African animal trypanosomiasis should be carefully monitored in this area.

Transient Superdiffusion and Long-Range Correlations in the Motility Patterns of Trypanosomatid Flagellate Protozoa.

We report on a diffusive analysis of the motion of flagellate protozoa species. These parasites are the etiological agents of neglected tropical diseases: leishmaniasis caused by Leishmania amazonensis and Leishmania braziliensis, African sleeping sickness caused by Trypanosoma brucei, and Chagas disease caused by Trypanosoma cruzi. By tracking the positions of these parasites and evaluating the variance related to the radial positions, we find that their motions are characterized by a short-time transient superdiffusive behavior. Also, the probability distributions of the radial positions are self-similar and can be approximated by a stretched Gaussian distribution. We further investigate the probability distributions of the radial velocities of individual trajectories. Among several candidates, we find that the generalized gamma distribution shows a good agreement with these distributions. The velocity time series have long-range correlations, displaying a strong persistent behavior (Hurst exponents close to one). The prevalence of "universal" patterns across all analyzed species indicates that similar mechanisms may be ruling the motion of these parasites, despite their differences in morphological traits. In addition, further analysis of these patterns could become a useful tool for investigating the activity of new candidate drugs against these and others neglected tropical diseases.

Symbiont transmission entails the risk of parasite infection.

Like many animals, firebugs (Hemiptera, Pyrrhocoridae) rely on behavioural adaptations to successfully endow their offspring with microbial mutualists. To transmit the nutritionally beneficial Coriobacteriaceae symbionts, female firebugs smear egg surfaces with symbiont-containing faecal droplets that are subsequently ingested by newly hatched nymphs through active probing to initiate infection. Alternatively, the symbionts can be acquired horizontally through contact with faeces of infected conspecifics. Here, we report that these adaptations ensuring successful transmission of bacterial symbionts among firebugs are exploited by the specialized trypanosomatid parasite Leptomonas pyrrhocoris. Using comparative transcriptomics, fluorescence in situ hybridization (FISH) and controlled bioassays, we demonstrate that the transmission cycle of L. pyrrhocoris mirrors that of the bacterial mutualists, with high efficiency for both vertical and horizontal transmission. This indicates that the parasite capitalizes on pre-existing behavioural adaptations (egg smearing and probing) to facilitate its own transfer within host populations, adaptations that likely evolved to initiate and maintain an association with beneficial gut symbionts. Thus, the transmission of mutualistic microbes across host generations can entail a significant risk of co-transmitting pathogens or parasites, thereby exerting selective pressures on the host to evolve more specific mechanisms of transfer.