Background Animal African trypanosomosis, a disease mainly caused by the protozoan parasite Trypanosoma congolense, is a major constraint to livestock productivity and has a significant impact in the developing countries of Africa. RNA interference (RNAi) has been used to study gene function and identify drug and vaccine targets in a variety of organisms including trypanosomes. However, trypanosome RNAi studies have mainly been conducted in T. brucei, as a model for human infection, largely ignoring livestock parasites of economical importance such as T. congolense, which displays different pathogenesis profiles. The whole T. congolense life cycle can be completed in vitro, but this attractive model displayed important limitations: (i) genetic tools were currently limited to insect forms and production of modified infectious BSF through differentiation was never achieved, (ii) in vitro differentiation techniques lasted several months, (iii) absence of long-term bloodstream forms (BSF) in vitro culture prevented genomic analyses. Methodology/Principal Findings We optimized culture conditions for each developmental stage and secured the differentiation steps. Specifically, we devised a medium adapted for the strenuous development of stable long-term BSF culture. Using Amaxa nucleofection technology, we greatly improved the transfection rate of the insect form and designed an inducible transgene expression system using the IL3000 reference strain. We tested it by expression of reporter genes and through RNAi. Subsequently, we achieved the complete in vitro life cycle with dramatically shortened time requirements for various wild type and transgenic strains. Finally, we established the use of modified strains for experimental infections and underlined a host adaptation phase requirement. Conclusions/Significance We devised an improved T. congolense model, which offers the opportunity to perform functional genomics analyses throughout the whole life cycle. It represents a very useful tool to understand pathogenesis mechanisms and to study potential therapeutic targets either in vitro or in vivo using a mouse model.

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Complete in vitro life cycle of Trypanosoma congolense: development of genetic tools.

Lipid peroxidation associated with anemia in rats experimentally infected with Trypanosoma evansi.

Very recent reports have documented that Trypanosoma evansi, the etiological agent of the livestock disease "surra," can cause human trypanosomiasis. In contrast to trypanosomes causing human African trypanosomiasis, T. evansi has a wide geographic distribution and host range, yet information about the immunobiological aspects of T. evansi trypanosomiasis is limited. Here, we show that, although T. evansi causes the induction of tumor necrosis factor (TNF), interferon-gamma, and nitric oxide during the early stage of infection, none of these molecules are crucial for parasitemia control and survival of the infected animal. However, TNF and TNF receptor 2 affect the induction of late-stage anemia. Using B cell- and immunoglobulin M (IgM)-deficient mice, we identified IgM as being crucial for parasitemia control and host survival. Collectively, our results show that, compared with other trypanosomes, T. evansi displays a distinct host-parasite interaction profile, give that, despite an infection-associated induction of proinflammatory molecules, only IgM antibodies contribute significantly to parasite control.

Control of Trypanosoma evansi Infection Is IgM Mediated and Does Not Require a Type I Inflammatory Response

Pathogenic mechanisms of Trypanosoma evansi infections.

https://www.cell.com/trends/parasitology/pdf/S1471-4922(08)00180-3.pdf

Contributions of experimental mouse models to the understanding of African trypanosomiasis

Trypanosoma evansi (Trypanosomatidae, Kinetoplastida) is a salivarian trypanosomatid that infects eight mammal orders spread over America, Europe and Asia. In Brazil, T. evansi is the etiological agent of "Mal de Cadeiras", a horse disease very often described in the region known as Pantanal do Mato Grosso. Few data concerning the genetic diversity and biology of subpopulations of T. evansi that circulate in Brazil are available. The factors that modulate the interaction of this parasite with its hosts also remain to be elucidated. Here we evaluated the course of experimental infection of six T. evansi isolates derived from domestic and wild animals in Swiss-Webster mice and three Mus musculus lineages. The follow-up included biological, immunological as well as biochemical and hematological parameters. The same isolates as well as three others were characterized by pulsed-field electrophoresis. Our results showed that T. evansi isolates displayed significant differences regarding behavior and morbidity patterns in the distinct mouse lineages. Nevertheless, these differences could not be correlated with pulsed-field electrophoresis profiles. Indeed, concerning this molecular marker, only microheterogeneity was observed. Moreover, we observed that the outcome of the infection is defined by both host genetic background and peculiarities (virulence factors) of the distinct T. evansi isolates. Anemia and hypoglycemia were the only features that could be observed in all mouse lineages, independently of the inoculated T. evansi subpopulation. In addition, our data also show that Mus musculus is a suitable model host for the study of the different pathogenetic features of T. evansi infection.

Trypanosoma evansi in inbred and Swiss-Webster mice: distinct aspects of pathogenesis

"Mal de Cadeiras", an enzootic disease caused by Trypanosoma evansi, is one of the most important trypanosomiases in the Brazilian Pantanal region. The disease affects mainly horses, which are widely used in extensive cattle production, an activity of greatest economical significance for the region. The parasite also infects sylvan (coatis and capybaras) and domestic (dogs) animals, respectively considered wild and domestic reservoirs of T. evansi. For a better understanding of the interaction of T. evansi with its rodent host, we evaluated the differences in the specific antibody level patterns and in the parasitic peptides recognition patterns of experimentally infected Wistar rats. The rats experimentally infected with T. evansi isolates obtained from coatis, dogs and horses were submitted to indirect immunofluorescence test (IgM e IgG) and Western blotting. The serological titers for IgM and IgG ranged between 1:40 and 1:160. The most recognized polypeptide profiles were in a range of 17 and 74 kDa. Our data suggest that the humoral immune response in Wistar rats is not sufficient for granting an effective control of T. evansi infections.

https://www.scielo.br/pdf/mioc/v96n7/4176.pdf

Adriana Oliveira Queiroz

Papers

Trypanosoma evansi in inbred and Swiss-Webster mice: distinct aspects of pathogenesis

Specific Antibody Levels and Antigenic Recognition of Wistar Rats Inoculated with Distinct Isolates of Trypanosoma evansi