Pascal Grébaut

First isolation of Enterobacter, Enterococcus, and Acinetobacter spp. as inhabitants of the tsetse fly (Glossina palpalis palpalis) midgut

This paper reports the first evidence of the presence of bacteria, other than the three previously described as symbionts, Wigglesworthia glossinidia, Wolbachia, and Sodalis glossinidius, in the midgut of Glossina palpalis palpalis, the tsetse fly, a vector of the chronic form of human African trypanosomiasis in sub-Saharan African countries. Based on the morphological, nutritional, physiological, and phylogenetic results, we identified Enterobacter, Enterococcus, and Acinetobacter spp. as inhabitants of the midgut of the tsetse fly from Angola. Enterobacter spp. was the most frequently isolated. The role of these bacteria in the gut, in terms of vector competence of the tsetse fly, is discussed, as is the possibility of using these bacteria to produce in situ trypanolytic molecules.

Identification of total and differentially expressed excreted-secreted proteins from Trypanosoma congolense strains exhibiting different virulence and pathogenicity.

Animal trypanosomosis is a major constraint to livestock productivity in the tropics and has a significant impact on the life of millions of people globally (mainly in Africa, South America and south-east Asia). In Africa, the disease in livestock is caused mainly by Trypanosoma congolense, Trypanosoma vivax, Trypanosoma evansi and Trypanosoma brucei brucei. The extracellular position of trypanosomes in the bloodstream of their host requires consideration of both the parasite and its naturally excreted-secreted factors (secretome) in the course of pathophysiological processes. We therefore developed and standardised a method to produce purified proteomes and secretomes of African trypanosomes. In this study, two strains of T. congolense exhibiting opposite properties of both virulence and pathogenicity were further investigated through their secretome expression and its involvement in host-parasite interactions. We used a combined proteomic approach (one-dimensional SDS-PAGE and two-dimensional differential in-gel electrophoresis coupled to mass spectrometry) to characterise the whole and differentially expressed protein contents of secretomes. The molecular identification of differentially expressed trypanosome molecules and their correlation with either the virulence process or pathogenicity are discussed with regard to their potential as new diagnostic or therapeutic tools against animal trypanosomosis.

Evaluation of LATEX/T.b.gambiense for mass screening of Trypanosoma brucei gambiense sleeping sickness in Central Africa

We compared the Card Agglutination Test for Trypanosomiasis (CATT), which consists of lyophilized bloodstream form trypomastigotes of Trypanosoma brucei gambiense (T.b.g.) variable antigen type LiTat 1.3, with LATEX/T.b.g., which consists of a lyophilized suspension of latex particles coated with variable surface glycoproteins of T.b.g. variable antigen types LiTat 1.3, 1.5 and 1.6. This study was carried out during two mass screening surveys in 1998 in Campo, a sleeping sickness focus in Cameroon, with a low prevalence (0.3%) and in 1999 in Batangafo which belongs to the Central African focus of Ouham which has a higher prevalence (3%). In Campo, we compared the CATT performed on whole blood with the LATEX/T.b.g. on diluted blood. In Batangafo, both tests were performed on diluted blood. In all circumstances, the specificity of the LATEX/T.b.g. was higher than of CATT. The use of LATEX/T.b.g. on diluted blood instead of CATT results in an important decrease of workload and as a consequence, of costs related to parasitological examinations. In the case of Campo the workload was up to 12 times less than when using CATT 1.3 on whole blood and the cost divided by 3. In Batangafo the workload was decreased by nearly 20% with the LATEX/T.b.g. Finally, it should be noted that in Batangafo, one of the parasitologically confirmed sleeping sickness patients was negative in CATT and positive in LATEX/T.b.g. and that the reading of the test result in LATEX/T.b.g. is easier than in CATT.

Transcriptomics and proteomics in human African trypanosomiasis: Current status and perspectives

Human African trypanosomiasis, or sleeping sickness, is a neglected vector-borne parasitic disease caused by protozoa of the species Trypanosoma brucei sensu lato. Within this complex species, T. b. gambiense is responsible for the chronic form of sleeping sickness in Western and Central Africa, whereas T. b. rhodesiense causes the acute form of the disease in East Africa. Presently, 1.5 million disability-adjusted life years (DALYs) per year are lost due to sleeping sickness. In addition, on the basis of the mortality, the disease is ranked ninth out of 25 human infectious and parasitic diseases in Africa. Diagnosis is complex and needs the intervention of a specialized skilled staff; treatment is difficult and expensive and has potentially life-threatening side effects. The use of transcriptomic and proteomic technologies, currently in rapid development and increasing in sensitivity and discriminating power, is already generating a large panel of promising results. The objective of these technologies is to significantly increase our knowledge of the molecular mechanisms governing the parasite establishment in its vector, the development cycle of the parasite during the parasites intra-vector life, its interactions with the fly and the other microbial inhabitants of the gut, and finally human host-trypanosome interactions. Such fundamental investigations are expected to provide opportunities to identify key molecular events that would constitute accurate targets for further development of tools dedicated to field work for early, sensitive, and stage-discriminant diagnosis, epidemiology, new chemotherapy, and potentially vaccine development, all of which will contribute to fighting the disease. The present review highlights the contributions of the transcriptomic and proteomic analyses developed thus far in order to identify potential targets (genes or proteins) and biological pathways that may constitute a critical step in the identification of new targets for the development of new tools for diagnostic and therapeutic purposes.

Human African Trypanosomiasis Transmission, Kinshasa, Democratic Republic of Congo

To investigate the epidemiology of human African trypanosomiasis (sleeping sickness) in Kinshasa, Democratic Republic of Congo, 2 entomologic surveys were conducted in 2005. Trypanosoma brucei gambiense and human-blood meals were found in tsetse fly midguts, which suggested active disease transmission. Vector control should be used to improve human African trypanosomiasis control efforts.

Secretome of Animal Trypanosomes

Animal trypanosomosis is one of the most severe constraints to agricultural development in sub‐Saharan Africa and is also an important disease of livestock in Latin America and Asia. The causative agents are various species of protozoan parasites belonging to the genus Trypanosoma, among which T. congolense and T. evansi are the major pathogenic species. The extracellular position of trypanosomes obliges us to consider both the parasite and its excreted/secreted factors in the course of the physiopathologic process. The advent of proteomics led us to propose a comparative approach of the proteome (i.e., the whole parasite content) and the secretome (i.e., naturally excreted/secreted molecules) of T. congolense and T. evansi with particular attention to common and specific molecules between strains of differing virulence and pathogenicity. The molecular identification of differentially expressed trypanosome molecules correlated with either the virulence process or the pathogenicity will provide new potential molecular targets for improved field diagnosis and chemotherapy of animal trypanosomosis.

Characterization of sleeping sickness transmission sites in rural and periurban areas of Kinshasa (Republique Democratique du Congo)

To characterize the potential transmission sites of sleeping sickness in Kinshasa, two entomologic surveys were carried out during the dry and the rainy seasons in rural and periurban areas of Kinshasa in 2005. About 610 pyramidal traps were set up, and 897 Glossina fuscipes quanzensis were captured. Environmental and biologic factors were reported, and relationships between these factors were evaluated using logistic regression and multiple correspondence analysis. The biologic factors (the presence of tsetse flies, human blood meals, and teneral flies) were progressively accumulated at each capture site to permit the characterization of the sleeping sickness transmission risk. The dry season was found to be a more favorable period for the disease transmission than the rainy season. Moreover, the landscapes characterized by the presence of argillaceous soils, raised ground cover with forest residues and rivers, were identified as types of environments with greater risk of sleeping sickness transmission. Pig breeding appeared as an important factor increasing the disease transmission. If vector control is continuously performed along rivers segments at high risk, the transmission of sleeping sickness in rural and periurban areas of Kinshasa will considerably decrease.

Pathogeno-Proteomics toward a new approach of host-vector-pathogen interactions

Many scientists working on pathogens (viruses, bacteria, fungi, parasites) are betting heavily on data generated by longitudinal genomic–transcriptomic–proteomic studies to explain biochemical host–vector–pathogen interactions and thus to contribute to disease control. Availability of genome sequences of various organisms, from viruses to complex metazoans, led to the discovery of the functions of the genes themselves. The postgenomic era stimulated the development of proteomic and bioinformatics tools to identify the locations, functions, and interactions of the gene products in tissues and/or cells of living organisms. Because of the diversity of available methods and the level of integration they promote, proteomics tools are potentially able to resolve interesting issues specific not only to host–vector–pathogen interactions in cell immunobiology, but also to ecology and evolution, population biology, and adaptive processes. These new analytical tools, as all new tools, contain pitfalls directly related to experimental design, statistical treatment, and protein identification. Nevertheless, they offer the potency of building large protein–protein interaction networks for in silico analysis of novel biological entities named “interactomes,” a way of modeling host–vector–pathogen interactions to define new interference strategies.

Tsetse flies, trypanosomes, humans and animals: what is proteomics revealing about their crosstalks?

Human and animal African trypanosomoses, or sleeping sickness and Nagana, are neglected vector-borne parasitic diseases caused by protozoa belonging to the Trypanosoma genus. Advances in proteomics offer new tools to better understand host–vector–parasite crosstalks occurring during the complex parasitic developmental cycle, and to determine the outcome of both transmission and infection. In this review, we summarize proteomics studies performed on African trypanosomes and on the interactions with their vector and mammalian hosts. We discuss the contributions and pitfalls of using diverse proteomics tools, and argue about the interest of pathogenoproteomics, both to generate advances in basic research on the best knowledge and understanding of host–vector–pathogen interactions, and to lead to the concrete development of new tools to improve diagnosis and treatment management of trypanosomoses in the near future.

Do Cryptic Reservoirs Threaten Gambiense-Sleeping Sickness Elimination?

Trypanosoma brucei gambiense causes human African trypanosomiasis (HAT). Between 1990 and 2015, almost 440 000 cases were reported. Large-scale screening of populations at risk, drug donations, and efforts by national and international stakeholders have brought the epidemic under control with <2200 cases in 2016. The World Health Organization (WHO) has set the goals of gambiense-HAT elimination as a public health problem for 2020, and of interruption of transmission to humans for 2030. Latent human infections and possible animal reservoirs may challenge these goals. It remains largely unknown whether, and to what extend, they have an impact on gambiense-HAT transmission. We argue that a better understanding of the contribution of human and putative animal reservoirs to gambiense-HAT epidemiology is mandatory to inform elimination strategies.