Trypanosoma rangeli--in vitro metacyclogenesis and fate of metacyclic trypomastigotes after infection to mice and fibroblast cultures

A systematic review of the diagnostic aspects and use of Trypanosoma rangeli as an immunogen for Trypanosoma cruzi infection

INTRODUCTION:

Trypanosoma rangeli is a protozoan that infects several domestic and wild mammals and shows significant distribution in Latin American countries. T. rangeli infection is similar to Chagas disease, both in diagnostic and prophylactic terms. Thus, the objective of this work was to review the diagnostic aspects and use of T. rangeli as an immunogen for Trypanosoma cruzi infection.

METHODS:

For this elaboration, Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were adopted with descriptors derived from the Medical Subject Headings (MeSH) platform in the PubMed/MEDLINE and SciELO databases. The inclusion criteria were defined as original articles on "Trypanosoma rangeli" and diagnostic aspects of T. rangeli infection in humans and/or research on the possible vaccines developed using T. rangeli strains for T. cruzi infection.

RESULTS:

After applying the inclusion and exclusion criteria, 18 articles were procured, of which 4 addressed research on the possible vaccines developed using T. rangeli for T. cruzi infection in vertebrates and the remaining 14 predominantly dealt with the diagnostic aspects of T. rangeli infection in humans.

CONCLUSIONS:

In this study, we formulated a compilation of the essential literature on this subject, emphasizing the need for more accurate and accessible techniques for the differential diagnosis of infections caused by both protozoa, and underscored several prospects in the search for a vaccine for Chagas disease.

Messenger RNA levels of the Polo-like kinase gene (PLK) correlate with cytokinesis in the Trypanosoma rangeli cell cycle

BACKGROUND

Trypanosoma rangeli is a protozoan parasite that is non-virulent to the mammalian host and is morphologically and genomically related to Trypanosoma cruzi, whose proliferation within the mammalian host is controversially discussed.

OBJECTIVES

We aimed to investigate the T. rangeli cell cycle in vitro and in vivo by characterizing the timespan of the parasite life cycle and by proposing a molecular marker to assess cytokinesis.

METHODOLOGY

The morphological events and their timing during the cell cycle of T. rangeli epimastigotes were assessed using DNA staining, flagellum labelling and bromodeoxyuridine incorporation. Messenger RNA levels of four genes previously associated with the cell cycle of trypanosomatids (AUK1, PLK, MOB1 and TRACK) were evaluated in the different T. rangeli forms.

FINDINGS

T. rangeli epimastigotes completed the cell cycle in vitro in 20.8 h. PLK emerged as a potential molecular marker for cell division, as its mRNA levels were significantly increased in exponentially growing epimastigotes compared with growth-arrested parasites or in vitro-differentiated trypomastigotes. PLK expression in T. rangeli can be detected near the flagellum protrusion site, reinforcing its role in the cell cycle. Interestingly, T. rangeli bloodstream trypomastigotes exhibited very low mRNA levels of PLK and were almost entirely composed of parasites in G1 phase.

MAIN CONCLUSIONS

Our work is the first to describe the T. rangeli cell cycle in vitro and proposes that PLK mRNA levels could be a useful tool to investigate the T. rangeli ability to proliferate within the mammalian host bloodstream.

The marsupial trypanosome Trypanosoma copemani is not an obligate intracellular parasite, although it adversely affects cell health

BACKGROUND

Trypanosoma cruzi invades and replicates inside mammalian cells, which can lead to chronic Chagas disease in humans. Trypanosoma copemani infects Australian marsupials and recent investigations indicate it may be able to invade mammalian cells in vitro, similar to T. cruzi. Here, T. cruzi 10R26 strain (TcIIa) and two strains of T. copemani [genotype 1 (G1) and genotype 2 (G2)] were incubated with marsupial cells in vitro. Live-cell time-lapse and fluorescent microscopy, combined with high-resolution microscopy (transmission and scanning electron microscopy) were used to investigate surface interactions between parasites and mammalian cells.

RESULTS

The number of parasites invading cells was significantly higher in T. cruzi compared to either genotype of T. copemani, between which there was no significant difference. While capable of cellular invasion, T. copemani did not multiply in host cells in vitro as there was no increase in intracellular amastigotes over time and no release of new trypomastigotes from host cells, as observed in T. cruzi. Exposure of host cells to G2 trypomastigotes resulted in increased host cell membrane permeability within 24 h of infection, and host cell death/blebbing was also observed. G2 parasites also became embedded in the host cell membrane.

CONCLUSIONS

Trypanosoma copemani is unlikely to have an obligate intracellular life-cycle like T. cruzi. However, T. copemani adversely affects cell health in vitro and should be investigated in vivo in infected host tissues to better understand this host-parasite relationship. Future research should focus on increasing understanding of the T. copemani life history and the genetic, physiological and ecological differences between different genotypes.

Host-Parasite Relationships and Life Histories of Trypanosomes in Australia

Trypanosomes constitute a group of flagellate protozoan parasites responsible for a number of important, yet neglected, diseases in both humans and livestock. The most significantly studied include the causative agents of African sleeping sickness (Trypanosoma brucei) and Chagas disease (Trypanosoma cruzi) in humans. Much of our knowledge about trypanosome host-parasite relationships and life histories has come from these two human pathogens. Recent investigations into the diversity and life histories of wildlife trypanosomes in Australia highlight that there exists a great degree of biological and behavioural variation within and between trypanosomes. In addition, the genetic relationships between some Australian trypanosomes show that they are unexpectedly more closely related to species outside Australia than within it. These findings have led to a growing focus on the importance of understanding parasites occurring naturally in wildlife to (1) better document parasite biodiversity, (2) determine evolutionary relationships and degree of host specificity, (3) understand host-parasite interactions and the role of parasites in the natural ecosystem and (4) identify biosecurity issues of emerging disease in both wildlife and human populations. Here we review what is known about the diversity, life histories, host-parasite interactions and evolutionary relationships of trypanosomes in Australian wildlife. In this context, we focus upon the genetic proximity of key Australian species to the pathogenic T. cruzi and discuss similarities in their biology and behaviour that present a potential risk of human disease transmission by Australian vectors and wildlife.

Revisiting Trypanosoma rangeli Transmission Involving Susceptible and Non-Susceptible Hosts

Trypanosoma rangeli infects several triatomine and mammal species in South America. Its transmission is known to occur when a healthy insect feeds on an infected mammal or when an infected insect bites a healthy mammal. In the present study we evaluated the classic way of T. rangeli transmission started by the bite of a single infected triatomine, as well as alternative ways of circulation of this parasite among invertebrate hosts. The number of metacyclic trypomastigotes eliminated from salivary glands during a blood meal was quantified for unfed and recently fed nymphs. The quantification showed that ~50,000 parasites can be liberated during a single blood meal. The transmission of T. rangeli from mice to R. prolixus was evaluated using infections started through the bite of a single infected nymph. The mice that served as the blood source for single infected nymphs showed a high percentage of infection and efficiently transmitted the infection to new insects. Parasites were recovered by xenodiagnosis in insects fed on mice with infections that lasted approximately four months. Hemolymphagy and co-feeding were tested to evaluate insect-insect T. rangeli transmission. T. rangeli was not transmitted during hemolymphagy. However, insects that had co-fed on mice with infected conspecifics exhibited infection rates of approximately 80%. Surprisingly, 16% of the recipient nymphs became infected when pigeons were used as hosts. Our results show that T. rangeli is efficiently transmitted between the evaluated hosts. Not only are the insect-mouse-insect transmission rates high, but parasites can also be transmitted between insects while co-feeding on a living host. We show for the first time that birds can be part of the T. rangeli transmission cycle as we proved that insect-insect transmission is feasible during a co-feeding on these hosts.

Trypanosoma rangeli uptakes the main lipoprotein from the hemolymph of its invertebrate host

During its life cycle Trypanosoma rangeli crosses the hemolymph of its invertebrate host. In the present study, we demonstrate for the first time the uptake of lipophorin (Lp), the main lipid-transporting particle of insect hemolymph. We observed that living T. rangeli parasites uptake lipids from both 32P- and 3H-, or 125I-labeled Lp. However, the parasites do not uptake any other hemolymphatic protein such as 32P-labeled vitellogenin. The presence of a specific receptor to Lp in the parasite surface is suggested based on experiments using 125I-Lp. We also investigated the intracellular fate of lipids using Texas Red-labeled phosphatidylethanolamine-Lp. Parasites were observed under confocal microscope and displayed fluorescent-labeled lipids close to the flagellar pocket and in vesicles at the posterior region. In conclusion, this study raises a novel set of molecular events which takes place during vector-parasite interaction.