Publications by authors named "Jan Van Den Abbeele"

66 Publications

Tsetse salivary glycoproteins are modified with paucimannosidic N-glycans, are recognised by C-type lectins and bind to trypanosomes.

PLoS Negl Trop Dis 2021 Feb 2;15(2):e0009071. Epub 2021 Feb 2.

Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.

African sleeping sickness is caused by Trypanosoma brucei, a parasite transmitted by the bite of a tsetse fly. Trypanosome infection induces a severe transcriptional downregulation of tsetse genes encoding for salivary proteins, which reduces its anti-hemostatic and anti-clotting properties. To better understand trypanosome transmission and the possible role of glycans in insect bloodfeeding, we characterized the N-glycome of tsetse saliva glycoproteins. Tsetse salivary N-glycans were enzymatically released, tagged with either 2-aminobenzamide (2-AB) or procainamide, and analyzed by HILIC-UHPLC-FLR coupled online with positive-ion ESI-LC-MS/MS. We found that the N-glycan profiles of T. brucei-infected and naïve tsetse salivary glycoproteins are almost identical, consisting mainly (>50%) of highly processed Man3GlcNAc2 in addition to several other paucimannose, high mannose, and few hybrid-type N-glycans. In overlay assays, these sugars were differentially recognized by the mannose receptor and DC-SIGN C-type lectins. We also show that salivary glycoproteins bind strongly to the surface of transmissible metacyclic trypanosomes. We suggest that although the repertoire of tsetse salivary N-glycans does not change during a trypanosome infection, the interactions with mannosylated glycoproteins may influence parasite transmission into the vertebrate host.
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http://dx.doi.org/10.1371/journal.pntd.0009071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7880456PMC
February 2021

Evaluation of the relative roles of the Tabanidae and Glossinidae in the transmission of trypanosomosis in drug resistance hotspots in Mozambique.

Parasit Vectors 2020 Apr 29;13(1):219. Epub 2020 Apr 29.

Eduardo Mondlane University, Biotechnology Center (CB-EMU), Maputo, Mozambique.

Background: Tsetse flies (Diptera: Glossinidae) and tabanids (Diptera: Tabanidae) are haematophagous insects of medical and veterinary importance due to their respective role in the biological and mechanical transmission of trypanosomes. Few studies on the distribution and relative abundance of both families have been conducted in Mozambique since the country's independence. Despite Nicoadala, Mozambique, being a multiple trypanocidal drug resistance hotspot no information regarding the distribution, seasonality or infection rates of fly-vectors are available. This is, however, crucial to understanding the epidemiology of trypanosomosis and to refine vector management.

Methods: For 365 days, 55 traps (20 NGU traps, 20 horizontal traps and 15 Epsilon traps) were deployed in three grazing areas of Nicoadala District: Namitangurine (25 traps); Zalala (15 traps); and Botao (15 traps). Flies were collected weekly and preserved in 70% ethanol. Identification using morphological keys was followed by molecular confirmation using cytochrome c oxidase subunit 1 gene. Trap efficiency, species distribution and seasonal abundance were also assessed. To determine trypanosome infection rates, DNA was extracted from the captured flies, and submitted to 18S PCR-RFLP screening for the detection of Trypanosoma.

Results: In total, 4379 tabanids (of 10 species) and 24 tsetse flies (of 3 species), were caught. NGU traps were more effective in capturing both the Tabanidae and Glossinidae. Higher abundance and species diversity were observed in Namitangurine followed by Zalala and Botao. Tabanid abundance was approximately double during the rainy season compared to the dry season. Trypanosoma congolense and T. theileri were detected in the flies with overall infection rates of 75% for tsetse flies and 13% for tabanids. Atylotus agrestis had the highest infection rate of the tabanid species. The only pathogenic trypanosome detected was T. congolense.

Conclusions: Despite the low numbers of tsetse flies captured, it can be assumed that they are still the cyclical vectors of trypanosomosis in the area. However, the high numbers of tabanids captured, associated to their demonstrated capacity of transmitting trypanosomes mechanically, suggest an important role in the epidemiology of trypanosomosis in the Nicoadala district. These results on the composition of tsetse and tabanid populations as well as the observed infection rates, should be considered when defining strategies to control the disease.
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http://dx.doi.org/10.1186/s13071-020-04087-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7189697PMC
April 2020

Catalase compromises the development of the insect and mammalian stages of Trypanosoma brucei.

FEBS J 2020 03 29;287(5):964-977. Epub 2019 Oct 29.

Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic.

Catalase is a widespread heme-containing enzyme, which converts hydrogen peroxide (H O ) to water and molecular oxygen, thereby protecting cells from the toxic effects of H O . Trypanosoma brucei is an aerobic protist, which conspicuously lacks this potent enzyme, present in virtually all organisms exposed to oxidative stress. To uncover the reasons for its absence in T. brucei, we overexpressed different catalases in procyclic and bloodstream stages of the parasite. The heterologous enzymes originated from the related insect-confined trypanosomatid Crithidia fasciculata and the human. While the trypanosomatid enzyme (cCAT) operates at low temperatures, its human homolog (hCAT) is adapted to the warm-blooded environment. Despite the presence of peroxisomal targeting signal in hCAT, both human and C. fasciculata catalases localized to the cytosol of T. brucei. Even though cCAT was efficiently expressed in both life cycle stages, the enzyme was active in the procyclic stage, increasing cell's resistance to the H O stress, yet its activity was suppressed in the cultured bloodstream stage. Surprisingly, following the expression of hCAT, the ability to establish the T. brucei infection in the tsetse fly midgut was compromised. In the mouse model, hCAT attenuated parasitemia and, consequently, increased the host's survival. Hence, we suggest that the activity of catalase in T. brucei is beneficial in vitro, yet it becomes detrimental for parasite's proliferation in both invertebrate and vertebrate hosts, leading to an inability to carry this, otherwise omnipresent, enzyme.
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http://dx.doi.org/10.1111/febs.15083DOI Listing
March 2020

Comparative genomic analysis of six Glossina genomes, vectors of African trypanosomes.

Genome Biol 2019 09 2;20(1):187. Epub 2019 Sep 2.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, USA.

Background: Tsetse flies (Glossina sp.) are the vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans, G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes), and Fusca (G. brevipalpis) which represent different habitats, host preferences, and vectorial capacity.

Results: Genomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Vision-associated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges.

Conclusions: Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies.
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http://dx.doi.org/10.1186/s13059-019-1768-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6721284PMC
September 2019

The Tsetse Fly Displays an Attenuated Immune Response to Its Secondary Symbiont, .

Front Microbiol 2019 24;10:1650. Epub 2019 Jul 24.

Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp, Antwerp, Belgium.

, a vertically transmitted facultative symbiont of the tsetse fly, is a bacterium in the early/intermediate state of its transition toward symbiosis, representing an important model for investigating how the insect host immune defense response is regulated to allow endosymbionts to establish a chronic infection within their hosts without being eliminated. In this study, we report on the establishment of a tsetse fly line devoid of only, allowing us to experimentally investigate (i) the complex immunological interactions between a single bacterial species and its host, (ii) how the symbiont population is kept under control, and (iii) the impact of the symbiont on the vector competence of the tsetse fly to transmit the sleeping sickness parasite. Comparative transcriptome analysis showed no difference in the expression of genes involved in innate immune processes between symbiont-harboring ( ) and -free () flies. Re-exposure of () flies to the endosymbiotic bacterium resulted in a moderate immune response, whereas exposure to pathogenic or to a close non-insect associated relative of , i.e., , resulted in full immune activation. We also showed that densities are not affected by experimental activation or suppression of the host immune system, indicating that is resistant to mounted immune attacks and that the host immune system does not play a major role in controlling proliferation. Finally, we demonstrate that the absence or presence of in the tsetse fly does not alter its capacity to mount an immune response to pathogens nor does it affect the fly's susceptibility toward trypanosome infection.
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http://dx.doi.org/10.3389/fmicb.2019.01650DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6668328PMC
July 2019

Complement Receptor 1 availability on red blood cell surface modulates Plasmodium vivax invasion of human reticulocytes.

Sci Rep 2019 06 20;9(1):8943. Epub 2019 Jun 20.

Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.

Plasmodium vivax parasites preferentially invade reticulocyte cells in a multistep process that is still poorly understood. In this study, we used ex vivo invasion assays and population genetic analyses to investigate the involvement of complement receptor 1 (CR1) in P. vivax invasion. First, we observed that P. vivax invasion of reticulocytes was consistently reduced when CR1 surface expression was reduced through enzymatic cleavage, in the presence of naturally low-CR1-expressing cells compared with high-CR1-expressing cells, and with the addition of soluble CR1, a known inhibitor of P. falciparum invasion. Immuno-precipitation experiments with P. vivax Reticulocyte Binding Proteins showed no evidence of complex formation. In addition, analysis of CR1 genetic data for worldwide human populations with different exposure to malaria parasites show significantly higher frequency of CR1 alleles associated with low receptor expression on the surface of RBCs and higher linkage disequilibrium in human populations exposed to P. vivax malaria compared with unexposed populations. These results are consistent with a positive selection of low-CR1-expressing alleles in vivax-endemic areas. Collectively, our findings demonstrate that CR1 availability on the surface of RBCs modulates P. vivax invasion. The identification of new molecular interactions is crucial to guiding the rational development of new therapeutic interventions against vivax malaria.
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http://dx.doi.org/10.1038/s41598-019-45228-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6586822PMC
June 2019

Innate immunity in the tsetse fly (Glossina), vector of African trypanosomes.

Dev Comp Immunol 2019 09 7;98:181-188. Epub 2019 May 7.

Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp, Nationalestraat 155, B-2000, Antwerp, Belgium. Electronic address:

Tsetse flies (Glossina sp.) are medically and veterinary important vectors of African trypanosomes, protozoan parasites that cause devastating diseases in humans and livestock in sub-Saharan Africa. These flies feed exclusively on vertebrate blood and harbor a limited diversity of obligate and facultative bacterial commensals. They have a well-developed innate immune system that plays a key role in protecting the fly against invading pathogens and in modulating the fly's ability to transmit African trypanosomes. In this review, we briefly summarize our current knowledge on the tsetse fly innate immune system and its interaction with the bacterial commensals and the trypanosome parasite.
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http://dx.doi.org/10.1016/j.dci.2019.05.003DOI Listing
September 2019

Towards improving tsetse fly paratransgenesis: stable colonization of Glossina morsitans morsitans with genetically modified Sodalis.

BMC Microbiol 2018 11 23;18(Suppl 1):165. Epub 2018 Nov 23.

Department of Biomedical Sciences, Unit of Veterinary Protozoology, Institute of Tropical Medicine Antwerp, Antwerp, Belgium.

Background: Tsetse flies (Glossina sp.) refractory to trypanosome infection are currently being explored as potential tools to contribute in the control of human and animal African trypanosomiasis. One approach to disrupt trypanosome transmission by the tsetse fly vector involves the use of paratransgenesis, a technique that aims to reduce vector competence of disease vectors via genetic modification of their microbiota. An important prerequisite for developing paratransgenic tsetse flies is the stable repopulation of tsetse flies and their progeny with its genetically modified Sodalis symbiont without interfering with host fitness.

Results: In this study, we assessed by qPCR analysis the ability of a chromosomally GFP-tagged Sodalis (recSodalis) strain to efficiently colonize various tsetse tissues and its transmission to the next generation of offspring using different introduction approaches. When introduced in the adult stage of the fly via thoracic microinjection, recSodalis is maintained at high densities for at least 21 days. However, no vertical transmission to the offspring was observed. Oral administration of recSodalis did not lead to the colonization of either adult flies or their offspring. Finally, introduction of recSodalis via microinjection of third-instar larvae resulted in stably colonized adult tsetse flies. Moreover, the subsequent generations of offspring were also efficiently colonized with recSodalis. We show that proper colonization of the female reproductive tissues by recSodalis is an important determinant for vertical transmission.

Conclusions: Intralarval microinjection of recSodalis proves to be essential to achieve optimal colonization of flies with genetically modified Sodalis and its subsequent dissemination into the following generations of progeny. This study provides the proof-of-concept that Sodalis can be used to drive expression of exogenous transgenes in Glossina morsitans morsitans colonies representing a valuable contribution to the development of a paratransgenic tsetse fly based control strategy.
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http://dx.doi.org/10.1186/s12866-018-1282-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251102PMC
November 2018

Combining paratransgenesis with SIT: impact of ionizing radiation on the DNA copy number of Sodalis glossinidius in tsetse flies.

BMC Microbiol 2018 11 23;18(Suppl 1):160. Epub 2018 Nov 23.

Insect Pest Control Laboratory, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Vienna International Centre, P.O. Box 100, 1400, Vienna, Austria.

Background: Tsetse flies (Diptera: Glossinidae) are the cyclical vectors of the causative agents of African Trypanosomosis, which has been identified as a neglected tropical disease in both humans and animals in many regions of sub-Saharan Africa. The sterile insect technique (SIT) has shown to be a powerful method to manage tsetse fly populations when used in the frame of an area-wide integrated pest management (AW-IPM) program. To date, the release of sterile males to manage tsetse fly populations has only been implemented in areas to reduce transmission of animal African Trypanosomosis (AAT). The implementation of the SIT in areas with Human African Trypanosomosis (HAT) would require additional measures to eliminate the potential risk associated with the release of sterile males that require blood meals to survive and hence, might contribute to disease transmission. Paratransgenesis offers the potential to develop tsetse flies that are refractory to trypanosome infection by modifying their associated bacteria (Sodalis glossinidius) here after referred to as Sodalis. Here we assessed the feasibility of combining the paratransgenesis approach with SIT by analyzing the impact of ionizing radiation on the copy number of Sodalis and the vectorial capacity of sterilized tsetse males.

Results: Adult Glossina morsitans morsitans that emerged from puparia irradiated on day 22 post larviposition did not show a significant decline in Sodalis copy number as compared with non-irradiated flies. Conversely, the Sodalis copy number was significantly reduced in adults that emerged from puparia irradiated on day 29 post larviposition and in adults irradiated on day 7 post emergence. Moreover, irradiating 22-day old puparia reduced the copy number of Wolbachia and Wigglesworthia in emerged adults as compared with non-irradiated controls, but the radiation treatment had no significant impact on the vectorial competence of the flies.

Conclusion: Although the radiation treatment significantly reduced the copy number of some tsetse fly symbionts, the copy number of Sodalis recovered with time in flies irradiated as 22-day old puparia. This recovery offers the opportunity to combine a paratransgenesis approach - using modified Sodalis to produce males refractory to trypanosome infection - with the release of sterile males to minimize the risk of disease transmission, especially in HAT endemic areas. Moreover, irradiation did not increase the vector competence of the flies for trypanosomes.
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http://dx.doi.org/10.1186/s12866-018-1283-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251162PMC
November 2018

How rational drug use reduces trypanosome infections in cattle in chemo-resistance hot-spot villages of northern Togo.

Acta Trop 2019 Feb 19;190:159-165. Epub 2018 Nov 19.

Freie Universitaet Berlin, Institute for Parasitology and Tropical Veterinary Medicine, Robert-von-Ostertag-Str. 7-13, D-14163 Berlin, Germany.

The study assessed an integrated trypanosomosis control strategy in drug-resistant hotspot villages of northern Togo. This strategy comprised (i) rational trypanocidal drug use in symptomatic cattle, (ii) vectors and ticks control by targeted bi-monthly insecticidal spraying of the lower body parts of cattle and (iii) strategic deworming with Albendazole in the beginning and the end of the rainy season. The program was implemented between June 2014 and October 2015 in four villages in northern Togo, which had been previously identified as drug resistant hotspots for diminazene diaceturate (DA) and isometamidium chloride (ISM). The integrated control strategy was implemented in eight cattle herds at risk of the disease from two villages. Twelve herds from two other villages served as controls where trypanosomosis management and deworming remained under control of the farmers. Trypanocidal drug use during the study period was recorded by the intervention team based on the farmers' reports and own observations. Cattle herds were followed-up for trypanosomosis symptoms which were recorded at 3 to 4-month intervals, while extensive trypanosome diagnostics and recording of the packed cell volume were done before and after the intervention. Intervention herds had a significantly lower risk of trypanosome infection with a risk ratio of 0.18 (95% CI: 0.04, 0.91; p = 0.03), but no significant effect on mean packed cell volume was observed. However, trypanocidal treatments per animal per year were lower in intervention herds compared to control herds (0.3 vs 5 for DA and 0.8 vs 2 for ISM). This study demonstrates that the implementation of an integrated best-bet strategy leads to a reduced trypanosome prevalence under lowered trypanocidal use.
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http://dx.doi.org/10.1016/j.actatropica.2018.11.023DOI Listing
February 2019

Drug quality analysis of isometamidium chloride hydrochloride and diminazene diaceturate used for the treatment of African animal trypanosomosis in West Africa.

BMC Vet Res 2018 Nov 20;14(1):361. Epub 2018 Nov 20.

Bioengineering Department, Vrije Universiteit Brussel, Pleinlaan 2, B-1050, Brussels, Belgium.

Background: Diminazene diaceturate (DA) and isometamidium chloride hydrochloride (ISM) are with homidium bromide, the main molecules used to treat African Animal Trypanosomosis (AAT). These drugs can be purchased from official suppliers but also from unofficial sources like local food markets or street vendors. The sub-standard quality of some of these trypanocides is jeopardizing the efficacy of treatment of sick livestock, leading thus to economic losses for the low-resource farmers and is contributing to the emergence and spread of drug resistance. The objective of this study was to assess the quality of trypanocidal drugs sold in French speaking countries of West Africa. In total, 308 drug samples including 282 of DA and 26 of ISM were purchased from official and unofficial sources in Benin, Burkina Faso, Côte d'Ivoire, Mali, Niger and Togo. All samples were analysed at LACOMEV (Dakar, Senegal), a reference laboratory of the World Organisation for Animal Health, by galenic inspection and high performance liquid chromatography.

Results: The results showed that 51.90% of the samples were non-compliant compared to the standards and were containing lower quantity of the active ingredient compared to the indications on the packaging. The non-compliances ranged from 63.27% in Togo to 32.65% in Burkina Faso (61.82% in Benin, 53.84% in Mali, 50% in Côte d'Ivoire, 47.36% in Niger). The rates of non-compliance were not statistically different (P = 0.572) from official or unofficial suppliers and ranged from 30 to 75% and from 0 to 65% respectively. However, the non-compliance was significantly higher for ISM compared to DA (P = 0.028).

Conclusions: The high non-compliance revealed in this study compromises the efficacy of therapeutic strategies against AAT, and is likely to exacerbate chemoresistance in West Africa. Corrective actions against sub-standard trypanocides urgently need to be taken by policy makers and control authorities.
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http://dx.doi.org/10.1186/s12917-018-1633-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6247674PMC
November 2018

Mitonuclear genomics challenges the theory of clonality in Trypanosoma congolense: Reply to Tibayrenc and Ayala.

Mol Ecol 2018 09 24;27(17):3425-3431. Epub 2018 Aug 24.

Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.

We recently published the first genomic diversity study of Trypanosoma congolense, a major aetiological agent of Animal African Trypanosomiasis. We demonstrated striking levels of SNP and indel diversity in the Eastern province of Zambia as a consequence of hybridization between divergent trypanosome lineages. We concluded that these and earlier findings in T. congolense challenge the predominant clonal evolution (PCE) model. In a recent comment, Tibayrenc and Ayala claim that there are many features in T. congolense supporting their theory of clonality. While we can follow the reasoning of the authors, we also identify major limitations in their theory and interpretations that resulted in incorrect conclusions. First, we argue that each T. congolense subgroup should be analysed independently as they may represent different (sub)species rather than "near-clades". Second, the authors neglect major findings of two robust population genetic studies on Savannah T. congolense that provide clear evidence of frequent recombination. Third, we reveal additional events of introgressive hybridization in T. congolense by analysing the maxicircle coding region using next-generation sequencing analyses. At last, we pinpoint two important misinterpretations by the authors and show that there are no spatially and temporally widespread clones in T. congolense. We stand by our earlier conclusions that the clonal framework is unlikely to accurately model the population structure of T. congolense. Other theoretical frameworks such as Maynard Smith's epidemic model may better represent the complex ancestry seen in T. congolense, where clones delimited in space and time arise against a background of recombination.
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http://dx.doi.org/10.1111/mec.14809DOI Listing
September 2018

Neutrophils enhance early Trypanosoma brucei infection onset.

Sci Rep 2018 07 25;8(1):11203. Epub 2018 Jul 25.

Unit of Veterinary Protozoology, Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp (ITM), Antwerp, Belgium.

In this study, Trypanosoma brucei was naturally transmitted to mice through the bites of infected Glossina morsitans tsetse flies. Neutrophils were recruited rapidly to the bite site, whereas monocytes were attracted more gradually. Expression of inflammatory cytokines (il1b, il6), il10 and neutrophil chemokines (cxcl1, cxcl5) was transiently up-regulated at the site of parasite inoculation. Then, a second influx of neutrophils occurred that coincided with the previously described parasite retention and expansion in the ear dermis. Congenital and experimental neutropenia models, combined with bioluminescent imaging, indicate that neutrophils do not significantly contribute to dermal parasite control and elicit higher systemic parasitemia levels during the infection onset. Engulfment of parasites by neutrophils in the skin was rarely observed and was restricted to parasites with reduced motility/viability, whereas live parasites escaped phagocytosis. To our knowledge, this study represents the first description of a trypanosome infection promoting role of early innate immunological reactions following an infective tsetse fly bite. Our data indicate that the trypanosome is not hindered in its early development and benefits from the host innate responses with the neutrophils being important regulators of the early infection, as already demonstrated for the sand fly transmitted Leishmania parasite.
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http://dx.doi.org/10.1038/s41598-018-29527-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6060092PMC
July 2018

Resistance to trypanocidal drugs in cattle populations of Zambezia Province, Mozambique.

Parasitol Res 2018 Feb 20;117(2):429-436. Epub 2017 Dec 20.

Biotechnology Center (CB-UEM-Mozambique), Eduardo Mondlane University, Maputo, Mozambique.

African animal trypanosomosis is a debilitating tsetse-transmitted parasitic disease of sub-Saharan Africa. Therapeutic and prophylactic drugs were introduced more than 50 years ago, and drug resistance is increasingly reported. In a cross-sectional study, 467 cattle were microscopically screened for trypanosomes. Samples were collected in May-July 2014 from five villages (Botao, Mungama, Zalala-Electrosul, Zalala-Madal, and Namitangurine) in Nicoadala district, Zambezia province. To evaluate treatment efficacy, trypanosome-positive animals in each village were randomly assigned to two groups, one treated with 0.5 mg/kg b.w. isometamidium (Inomidium®), the second with 3.5 mg/kg b.w. diminazene (Inomazene®). Cattle were microscopically monitored at days 0, 14, and 28 post-treatment. At day 28, trypanocides were swapped to investigate single or multiple resistance. Microscopically negative samples from the monitoring days were tested using 18S-PCR-RFLP. 22.9% (107/467) was found positive on day 0. On day 14, nine animals in Botao and seven in Mungama were positive. On day 28, in Botao, four animals from the diminazene group and four from the isometamidium group were positive. In Mungama, four animals from the diminazene group were positive on day 28. On day 42, six animals (9%) in Botao and two (9.5%) in Mungama remained positive after drug swap. No relapses occurred in Namitangurine. The 18S-PCR-RFLP consistently detected more positive than microscopy: indeed, positives reached 12, 13, and 8 in Botao and 9, 7, and 4 in Mungama, at days 14, 28, and 42, respectively. Single- and multi-drug resistance in Nicoadala district, Zambezia province, is thus here confirmed. This should be considered when choosing control options.
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http://dx.doi.org/10.1007/s00436-017-5718-1DOI Listing
February 2018

Genomic analysis of Isometamidium Chloride resistance in Trypanosoma congolense.

Int J Parasitol Drugs Drug Resist 2017 12 6;7(3):350-361. Epub 2017 Oct 6.

Department of Biomedical Sciences, Institute of Tropical Medicine, Nationalestraat 155, 2000 Antwerp, Belgium. Electronic address:

Isometamidium Chloride (ISM) is one of the principal drugs used to counteract Trypanosoma congolense infection in livestock, both as a prophylactic as well as a curative treatment. However, numerous cases of ISM resistance have been reported in different African regions, representing a significant constraint in the battle against Animal African Trypanosomiasis. In order to identify genetic signatures associated with ISM resistance in T. congolense, the sensitive strain MSOROM7 was selected for induction of ISM resistance in a murine host. Administered ISM concentrations in immune-suppressed mice were gradually increased from 0.001 mg/kg to 1 mg/kg, the maximal dose used in livestock. As a result, three independent MSOROM7 lines acquired full resistance to this concentration after five months of induction, and retained this full resistant phenotype following a six months period without drug pressure. In contrast, parasites did not acquire ISM resistance in immune-competent animals, even after more than two years under ISM pressure, suggesting that the development of full ISM resistance is strongly enhanced when the host immune response is compromised. Genomic analyses comparing the ISM resistant lines with the parental sensitive line identified shifts in read depth at heterozygous loci in genes coding for different transporters and transmembrane products, and several of these shifts were also found within natural ISM resistant isolates. These findings suggested that the transport and accumulation of ISM inside the resistant parasites may be modified, which was confirmed by flow cytometry and ex vivo ISM uptake assays that showed a decrease in the accumulation of ISM in the resistant parasites.
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http://dx.doi.org/10.1016/j.ijpddr.2017.10.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5645165PMC
December 2017

Evidence for viable and stable triploid Trypanosoma congolense parasites.

Parasit Vectors 2017 Oct 10;10(1):468. Epub 2017 Oct 10.

Department of Biomedical Sciences, Institute of Tropical Medicine, Nationalestraat 155, 2000, Antwerp, Belgium.

Background: Recent whole genome sequencing (WGS) analysis identified a viable triploid strain of Trypanosoma congolense. This triploid strain BANANCL2 was a clone of the field isolate BANAN/83/CRTRA/64 that was collected from cattle in Burkina Faso in 1983.

Results: We demonstrated the viability and stability of triploidy throughout the complete life-cycle of the parasite by infecting tsetse flies with the triploid clone BANANCL2. Proboscis-positive tsetse flies efficiently transmitted the parasites to mice resulting in systemic infections. WGS of the parasites was performed at all life-cycle stages, and a method based on a block alternative allele frequency spectrum was developed to efficiently detect the ploidy profiles of samples with low read depth. This approach confirmed the triploid profile of parasites throughout their life-cycle in the tsetse fly and the mammalian host, demonstrating that triploidy is present at all stages and is stable over time.

Conclusion: The presence of viable field-isolated triploid parasites indicates another possible layer of genetic diversity in natural T. congolense populations. The comparison between triploid and diploid parasites provides a unique model system to study the impact of chromosome copy number variations in African trypanosomes. In addition, the consequences of triploidy can be further investigated using this stable triploid model.
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http://dx.doi.org/10.1186/s13071-017-2406-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5635536PMC
October 2017

Discovery and genomic analyses of hybridization between divergent lineages of Trypanosoma congolense, causative agent of Animal African Trypanosomiasis.

Mol Ecol 2017 Dec 24;26(23):6524-6538. Epub 2017 Aug 24.

Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.

Hybrid populations and introgressive hybridization remain poorly documented in pathogenic micro-organisms, as such that genetic exchange has been argued to play a minor role in their evolution. Recent work demonstrated the existence of hybrid microsatellite profiles in Trypanosoma congolense, a parasitic protozoan with detrimental effects on livestock productivity in sub-Saharan Africa. Here, we present the first population genomic study of T. congolense, revealing a remarkable number of single nucleotide polymorphisms (SNPs), small insertions/deletions (indels) and gene deletions among 56 parasite genomes from ten African countries. One group of parasites from Zambia was particularly diverse, displaying a substantial number of heterozygous SNP and indel sites compared to T. congolense parasites from the nine other sub-Saharan countries. Genomewide 5-kb phylogenetic analyses based on phased SNP data revealed that these parasites were the product of hybridization between phylogenetically distinct T. congolense lineages. Other parasites within the same region in Zambia presented a mosaic of haplotypic ancestry and genetic variability, indicating that hybrid parasites persisted and recombined beyond the initial hybridization event. Our observations challenge traditional views of trypanosome population biology and encourage future research on the role of hybridization in spreading genes for drug resistance, pathogenicity and virulence.
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http://dx.doi.org/10.1111/mec.14271DOI Listing
December 2017

Nanobodies As Tools to Understand, Diagnose, and Treat African Trypanosomiasis.

Front Immunol 2017 30;8:724. Epub 2017 Jun 30.

Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.

African trypanosomes are strictly extracellular protozoan parasites that cause diseases in humans and livestock and significantly affect the economic development of sub-Saharan Africa. Due to an elaborate and efficient (vector)-parasite-host interplay, required to complete their life cycle/transmission, trypanosomes have evolved efficient immune escape mechanisms that manipulate the entire host immune response. So far, not a single field applicable vaccine exists, and chemotherapy is the only strategy available to treat the disease. Current therapies, however, exhibit high drug toxicity and an increased drug resistance is being reported. In addition, diagnosis is often hampered due to the inadequacy of current diagnostic procedures. In the context of tackling the shortcomings of current treatment and diagnostic approaches, nanobodies (Nbs, derived from the heavy chain-only antibodies of camels and llamas) might represent unmet advantages compared to conventional tools. Indeed, the combination of their small size, high stability, high affinity, and specificity for their target and tailorability represents a unique advantage, which is reflected by their broad use in basic and clinical research to date. In this article, we will review and discuss (i) diagnostic and therapeutic applications of Nbs that are being evaluated in the context of African trypanosomiasis, (ii) summarize new strategies that are being developed to optimize their potency for advancing their use, and (iii) document on unexpected properties of Nbs, such as inherent trypanolytic activities, that besides opening new therapeutic avenues, might offer new insight in hidden biological activities of conventional antibodies.
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http://dx.doi.org/10.3389/fimmu.2017.00724DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5492476PMC
June 2017

Human African trypanosomiasis control: Achievements and challenges.

PLoS Negl Trop Dis 2017 04 20;11(4):e0005454. Epub 2017 Apr 20.

Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.

Sleeping sickness, also known as human African trypanosomiasis (HAT), is a neglected disease that impacts 70 million people living in 1.55 million km2 in sub-Saharan Africa. Since the beginning of the 20th century, there have been multiple HAT epidemics in sub-Saharan Africa, with the most recent epidemic in the 1990s resulting in about half a million HAT cases reported between 1990 and 2015. Here we review the status of HAT disease at the current time and the toolbox available for its control. We also highlight future opportunities under development towards novel or improved interventions.
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http://dx.doi.org/10.1371/journal.pntd.0005454DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5398477PMC
April 2017

The Hrg protein is a heme transporter involved in the regulation of stage-specific morphological transitions.

J Biol Chem 2017 04 23;292(17):6998-7010. Epub 2017 Feb 23.

From the Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic,

The human parasite does not synthesize heme and instead relies entirely on heme supplied by its vertebrate host or its insect vector, the tsetse fly. In the host bloodstream scavenges heme via haptoglobin-hemoglobin (HpHb) receptor-mediated endocytosis occurring in the flagellar pocket. However, in the procyclic developmental stage, in which is confined to the tsetse fly midgut, this receptor is apparently not expressed, suggesting that takes up heme by a different, unknown route. To define this alternative route, we functionally characterized heme transporter Hrg in the procyclic stage. RNAi-induced down-regulation of Hrg in heme-limited culture conditions resulted in slower proliferation, decreased cellular heme, and marked changes in cellular morphology so that the cells resemble mesocyclic trypomastigotes. Nevertheless, the Hrg KO developed normally in the tsetse flies at rates comparable with wild-type cells. cells overexpressing Hrg displayed up-regulation of the early procyclin GPEET and down-regulation of the late procyclin EP1, two proteins coating the surface in the procyclic stage. Light microscopy of immunostained Hrg indicated localization to the flagellar membrane, and scanning electron microscopy revealed more intense Hrg accumulation toward the flagellar pocket. Based on these findings, we postulate that senses heme levels via the flagellar Hrg protein. Heme deprivation in the tsetse fly anterior midgut might represent an environmental stimulus involved in the transformation of this important human parasite, possibly through metabolic remodeling.
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http://dx.doi.org/10.1074/jbc.M116.762997DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5409468PMC
April 2017

Tsetse fly tolerance to T. brucei infection: transcriptome analysis of trypanosome-associated changes in the tsetse fly salivary gland.

BMC Genomics 2016 11 25;17(1):971. Epub 2016 Nov 25.

Unit of Veterinary Protozoology, Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp (ITM), Antwerp, Belgium.

Background: For their transmission, African trypanosomes rely on their blood feeding insect vector, the tsetse fly (Glossina sp.). The ingested Trypanosoma brucei parasites have to overcome a series of barriers in the tsetse fly alimentary tract to finally develop into the infective metacyclic forms in the salivary glands that are transmitted to a mammalian host by the tsetse bite. The parasite population in the salivary gland is dense with a significant number of trypanosomes tightly attached to the epithelial cells. Our current knowledge on the impact of the infection on the salivary gland functioning is very limited. Therefore, this study aimed to gain a deeper insight into the global gene expression changes in the salivary glands of Glossina morsitans morsitans in response to an infection with the T. brucei parasite. A detailed whole transcriptome comparison of midgut-infected tsetse with and without a mature salivary gland infection was performed to study the impact of a trypanosome infection on different aspects of the salivary gland functioning and the mechanisms that are induced in this tissue to tolerate the infection i.e. to control the negative impact of the parasite presence. Moreover, a transcriptome comparison with age-matched uninfected flies was done to see whether gene expression in the salivary glands is already affected by a trypanosome infection in the tsetse midgut.

Results: By a RNA-sequencing (RNA-seq) approach we compared the whole transcriptomes of flies with a T. brucei salivary gland/midgut infection versus flies with only a midgut infection or versus non-infected flies, all with the same age and feeding history. More than 7500 salivary gland transcripts were detected from which a core group of 1214 differentially expressed genes (768 up- and 446 down-regulated) were shared between the two transcriptional comparisons. Gene Ontology enrichment analysis and detailed gene expression comparisons showed a diverse impact at the gene transcript level. Increased expression was observed for transcripts encoding for proteins involved in immunity (like several genes of the Imd-signaling pathway, serine proteases, serpins and thioester-containing proteins), detoxification of reactive species, cell death, cytoskeleton organization, cell junction and repair. Decreased expression was observed for transcripts encoding the major secreted proteins such as 5'-nucleotidases, adenosine deaminases and the nucleic acid binding proteins Tsals. Moreover, expression of some gene categories in the salivary glands were found to be already affected by a trypanosome midgut infection, before the parasite reaches the salivary glands.

Conclusions: This study reveals that the T. brucei population in the tsetse salivary gland has a negative impact on its functioning and on the integrity of the gland epithelium. Our RNA-seq data suggest induction of a strong local tissue response in order to control the epithelial cell damage, the ROS intoxication of the cellular environment and the parasite infection, resulting in the fly tolerance to the infection. The modified expression of some gene categories in the tsetse salivary glands by a trypanosome infection at the midgut level indicate a putative anticipatory response in the salivary glands, before the parasite reaches this tissue.
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http://dx.doi.org/10.1186/s12864-016-3283-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123318PMC
November 2016

Characterization of a neuropeptide F receptor in the tsetse fly, Glossina morsitans morsitans.

J Insect Physiol 2016 Oct - Nov;93-94:105-111. Epub 2016 Sep 24.

Functional Genomics and Proteomics, Department of Biology, KU Leuven, Leuven, Belgium. Electronic address:

Neuropeptides related to mammalian neuropeptide Y (NPY) and insect neuropeptide F (NPF) are conserved throughout Metazoa and intimately involved in a wide range of biological processes. In insects NPF is involved in regulating feeding, learning, stress and reproductive behavior. Here we identified and characterized an NPF receptor of the tsetse fly, Glossina morsitans morsitans, the sole transmitter of Trypanosoma parasites causing sleeping sickness. We isolated cDNA sequences encoding tsetse NPF (Glomo-NPF) and its receptor (Glomo-NPFR), and examined their spatial and temporal expression patterns using quantitative PCR. In tsetse flies, npfr transcripts are expressed throughout development and most abundantly in the central nervous system, whereas low expression is found in the flight muscles and posterior midgut. Expression of npf, by contrast, shows low transcript levels during development but is strongly expressed in the posterior midgut and brain of adult flies. Expression of Glomo-npf and its receptor in the brain and digestive system suggests that NPF may have conserved neuromodulatory or hormonal functions in tsetse flies, such as in the regulation of feeding behavior. Cell-based activity studies of the Glomo-NPFR showed that Glomo-NPF activates the receptor up to nanomolar concentrations. The molecular data of Glomo-NPF and Glomo-NPFR paves the way for further investigation of its functions in tsetse flies.
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http://dx.doi.org/10.1016/j.jinsphys.2016.09.013DOI Listing
July 2017

MIF-Mediated Hemodilution Promotes Pathogenic Anemia in Experimental African Trypanosomosis.

PLoS Pathog 2016 09 15;12(9):e1005862. Epub 2016 Sep 15.

Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.

Animal African trypanosomosis is a major threat to the economic development and human health in sub-Saharan Africa. Trypanosoma congolense infections represent the major constraint in livestock production, with anemia as the major pathogenic lethal feature. The mechanisms underlying anemia development are ill defined, which hampers the development of an effective therapy. Here, the contribution of the erythropoietic and erythrophagocytic potential as well as of hemodilution to the development of T. congolense-induced anemia were addressed in a mouse model of low virulence relevant for bovine trypanosomosis. We show that in infected mice, splenic extramedullary erythropoiesis could compensate for the chronic low-grade type I inflammation-induced phagocytosis of senescent red blood cells (RBCs) in spleen and liver myeloid cells, as well as for the impaired maturation of RBCs occurring in the bone marrow and spleen. Rather, anemia resulted from hemodilution. Our data also suggest that the heme catabolism subsequent to sustained erythrophagocytosis resulted in iron accumulation in tissue and hyperbilirubinemia. Moreover, hypoalbuminemia, potentially resulting from hemodilution and liver injury in infected mice, impaired the elimination of toxic circulating molecules like bilirubin. Hemodilutional thrombocytopenia also coincided with impaired coagulation. Combined, these effects could elicit multiple organ failure and uncontrolled bleeding thus reduce the survival of infected mice. MIF (macrophage migrating inhibitory factor), a potential pathogenic molecule in African trypanosomosis, was found herein to promote erythrophagocytosis, to block extramedullary erythropoiesis and RBC maturation, and to trigger hemodilution. Hence, these data prompt considering MIF as a potential target for treatment of natural bovine trypanosomosis.
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http://dx.doi.org/10.1371/journal.ppat.1005862DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5025191PMC
September 2016

Immune Evasion Strategies of Trypanosoma brucei within the Mammalian Host: Progression to Pathogenicity.

Front Immunol 2016 24;7:233. Epub 2016 Jun 24.

Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium; Department of Structural Biology, VIB, Brussels, Belgium.

The diseases caused by African trypanosomes (AT) are of both medical and veterinary importance and have adversely influenced the economic development of sub-Saharan Africa. Moreover, so far not a single field applicable vaccine exists, and chemotherapy is the only strategy available to treat the disease. These strictly extracellular protozoan parasites are confronted with different arms of the host's immune response (cellular as well as humoral) and via an elaborate and efficient (vector)-parasite-host interplay they have evolved efficient immune escape mechanisms to evade/manipulate the entire host immune response. This is of importance, since these parasites need to survive sufficiently long in their mammalian/vector host in order to complete their life cycle/transmission. Here, we will give an overview of the different mechanisms AT (i.e. T. brucei as a model organism) employ, comprising both tsetse fly saliva and parasite-derived components to modulate host innate immune responses thereby sculpturing an environment that allows survival and development within the mammalian host.
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http://dx.doi.org/10.3389/fimmu.2016.00233DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4919330PMC
July 2016

The Dermis as a Delivery Site of Trypanosoma brucei for Tsetse Flies.

PLoS Pathog 2016 07 21;12(7):e1005744. Epub 2016 Jul 21.

Unit of Veterinary Protozoology, Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp (ITM), Antwerp, Belgium.

Tsetse flies are the sole vectors of Trypanosoma brucei parasites that cause sleeping sickness. Our knowledge on the early interface between the infective metacyclic forms and the mammalian host skin is currently highly limited. Glossina morsitans flies infected with fluorescently tagged T. brucei parasites were used in this study to initiate natural infections in mice. Metacyclic trypanosomes were found to be highly infectious through the intradermal route in sharp contrast with blood stream form trypanosomes. Parasite emigration from the dermal inoculation site resulted in detectable parasite levels in the draining lymph nodes within 18 hours and in the peripheral blood within 42 h. A subset of parasites remained and actively proliferated in the dermis. By initiating mixed infections with differentially labeled parasites, dermal parasites were unequivocally shown to arise from the initial inoculum and not from a re-invasion from the blood circulation. Scanning electron microscopy demonstrated intricate interactions of these skin-residing parasites with adipocytes in the connective tissue, entanglement by reticular fibers of the periadipocytic baskets and embedment between collagen bundles. Experimental transmission experiments combined with molecular parasite detection in blood fed flies provided evidence that dermal trypanosomes can be acquired from the inoculation site immediately after the initial transmission. High resolution thermographic imaging also revealed that intradermal parasite expansion induces elevated skin surface temperatures. Collectively, the dermis represents a delivery site of the highly infective metacyclic trypanosomes from which the host is systemically colonized and where a proliferative subpopulation remains that is physically constrained by intricate interactions with adipocytes and collagen fibrous structures.
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http://dx.doi.org/10.1371/journal.ppat.1005744DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4956260PMC
July 2016

Molecular characterization of a short neuropeptide F signaling system in the tsetse fly, Glossina morsitans morsitans.

Gen Comp Endocrinol 2016 09 8;235:142-149. Epub 2016 Jun 8.

Functional Genomics and Proteomics, Department of Biology, KU Leuven, Leuven, Belgium. Electronic address:

Neuropeptides of the short neuropeptide F (sNPF) family are widespread among arthropods and found in every sequenced insect genome so far. Functional studies have mainly focused on the regulatory role of sNPF in feeding behavior, although this neuropeptide family has pleiotropic effects including in the control of locomotion, osmotic homeostasis, sleep, learning and memory. Here, we set out to characterize and determine possible roles of sNPF signaling in the haematophagous tsetse fly Glossina morsitans morsitans, a vector of African Trypanosoma parasites causing human and animal African trypanosomiasis. We cloned the G. m. morsitans cDNA sequences of an sNPF-like receptor (Glomo-sNPFR) and precursor protein encoding four Glomo-sNPF neuropeptides. All four Glomo-sNPF peptides concentration-dependently activated Glomo-sNPFR in a cell-based calcium mobilization assay, with EC50 values in the nanomolar range. Gene expression profiles in adult female tsetse flies indicate that the Glomo-sNPF system is mainly restricted to the nervous system. Glomo-snpfr transcripts were also detected in the hindgut of adult females. In contrast to the Drosophila sNPF system, tsetse larvae lack expression of Glomo-snpf and Glomo-snpfr genes. While Glomo-snpf transcript levels are upregulated in pupae, the onset of Glomo-snpfr expression is delayed to adulthood. Expression profiles in adult tissues are similar to those in other insects suggesting that the tsetse sNPF system may have similar functions such as a regulatory role in feeding behavior, together with a possible involvement of sNPFR signaling in osmotic homeostasis. Our molecular data will enable further investigations into the functions of sNPF signaling in tsetse flies.
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http://dx.doi.org/10.1016/j.ygcen.2016.06.005DOI Listing
September 2016

Trypanosoma brucei Parasites Occupy and Functionally Adapt to the Adipose Tissue in Mice.

Cell Host Microbe 2016 Jun 26;19(6):837-48. Epub 2016 May 26.

Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1990-375 Lisboa, Portugal. Electronic address:

Trypanosoma brucei is an extracellular parasite that causes sleeping sickness. In mammalian hosts, trypanosomes are thought to exist in two major niches: early in infection, they populate the blood; later, they breach the blood-brain barrier. Working with a well-established mouse model, we discovered that adipose tissue constitutes a third major reservoir for T. brucei. Parasites from adipose tissue, here termed adipose tissue forms (ATFs), can replicate and were capable of infecting a naive animal. ATFs were transcriptionally distinct from bloodstream forms, and the genes upregulated included putative fatty acid β-oxidation enzymes. Consistent with this, ATFs were able to utilize exogenous myristate and form β-oxidation intermediates, suggesting that ATF parasites can use fatty acids as an external carbon source. These findings identify the adipose tissue as a niche for T. brucei during its mammalian life cycle and could potentially explain the weight loss associated with sleeping sickness.
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http://dx.doi.org/10.1016/j.chom.2016.05.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4906371PMC
June 2016

Characterization and pharmacological analysis of two adipokinetic hormone receptor variants of the tsetse fly, Glossina morsitans morsitans.

Insect Biochem Mol Biol 2016 Mar 10;70:73-84. Epub 2015 Dec 10.

Functional Genomics and Proteomics, Department of Biology, KU Leuven, Naamsestraat 59, 3000, Leuven, Belgium. Electronic address:

Adipokinetic hormones (AKH) are well known regulators of energy metabolism in insects. These neuropeptides are produced in the corpora cardiaca and perform their hormonal function by interacting with specific G protein-coupled receptors (GPCRs) at the cell membranes of target tissues, mainly the fat body. Here, we investigated the sequences, spatial and temporal distributions, and pharmacology of AKH neuropeptides and receptors in the tsetse fly, Glossina morsitans morsitans. The open reading frames of two splice variants of the Glomo-akh receptor (Glomo-akhr) gene and of the AKH neuropeptide encoding genes, gmmhrth and gmmakh, were cloned. Both tsetse AKHR isoforms show strong sequence conservation when compared to other insect AKHRs. Glomo-AKH prepropeptides also have the typical architecture of AKH precursors. In an in vitro Ca(2+) mobilization assay, Glomo-AKH neuropeptides activated each receptor isoform up to nanomolar concentrations. We identified structural features of tsetse AKH neuropeptides essential for receptor activation in vitro. Gene expression profiles suggest a function for AKH signaling in regulating Glossina energy metabolism, where AKH peptides are released from the corpora cardiaca and activate receptors mainly expressed in the fat body. This analysis of the ligand-receptor coupling, expression, and pharmacology of the two Glomo-AKHR variants facilitates further elucidation of the function of AKH in G. m. morsitans.
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http://dx.doi.org/10.1016/j.ibmb.2015.11.010DOI Listing
March 2016

Peptidomics of Neuropeptidergic Tissues of the Tsetse Fly Glossina morsitans morsitans.

J Am Soc Mass Spectrom 2015 Dec 13;26(12):2024-38. Epub 2015 Oct 13.

Functional Genomics and Proteomics, Department of Biology, KU Leuven, 3000, Leuven, Belgium.

Neuropeptides and peptide hormones are essential signaling molecules that regulate nearly all physiological processes. The recent release of the tsetse fly genome allowed the construction of a detailed in silico neuropeptide database (International Glossina Genome Consortium, Science 344, 380-386 (2014)), as well as an in-depth mass spectrometric analysis of the most important neuropeptidergic tissues of this medically and economically important insect species. Mass spectrometric confirmation of predicted peptides is a vital step in the functional characterization of neuropeptides, as in vivo peptides can be modified, cleaved, or even mispredicted. Using a nanoscale reversed phase liquid chromatography coupled to a Q Exactive Orbitrap mass spectrometer, we detected 51 putative bioactive neuropeptides encoded by 19 precursors: adipokinetic hormone (AKH) I and II, allatostatin A and B, capability/pyrokinin (capa/PK), corazonin, calcitonin-like diuretic hormone (CT/DH), FMRFamide, hugin, leucokinin, myosuppressin, natalisin, neuropeptide-like precursor (NPLP) 1, orcokinin, pigment dispersing factor (PDF), RYamide, SIFamide, short neuropeptide F (sNPF) and tachykinin. In addition, propeptides, truncated and spacer peptides derived from seven additional precursors were found, and include the precursors of allatostatin C, crustacean cardioactive peptide, corticotropin releasing factor-like diuretic hormone (CRF/DH), ecdysis triggering hormone (ETH), ion transport peptide (ITP), neuropeptide F, and proctolin, respectively. The majority of the identified neuropeptides are present in the central nervous system, with only a limited number of peptides in the corpora cardiaca-corpora allata and midgut. Owing to the large number of identified peptides, this study can be used as a reference for comparative studies in other insects. Graphical Abstract ᅟ.
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http://dx.doi.org/10.1007/s13361-015-1248-1DOI Listing
December 2015

Paternal Transmission of a Secondary Symbiont during Mating in the Viviparous Tsetse Fly.

Mol Biol Evol 2015 Aug 7;32(8):1977-80. Epub 2015 Apr 7.

Unit of Veterinary Protozoology, Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp, Antwerp, Belgium Laboratory of Zoophysiology, Department of Physiology, University of Ghent, Ghent, Belgium

Sodalis glossinidius, a maternally inherited secondary symbiont of the tsetse fly, is a bacterium in the early/intermediate state of the transition toward symbiosis, representing an important model for investigating establishment and evolution of insect-bacteria symbiosis. The absence of phylogenetic congruence in tsetse-Sodalis coevolution and the existence of Sodalis genotypic diversity in field flies are suggestive for a horizontal transmission route. However, to date no natural mechanism for the horizontal transfer of this symbiont has been identified. Using novel methodologies for the stable fluorescent-labeling and introduction of modified Sodalis in tsetse flies, we unambiguously show that male-borne Sodalis is 1) horizontally transferred to females during mating and 2) subsequently vertically transmitted to the progeny, that is, paternal transmission. This mixed mode of transmission has major consequences regarding Sodalis' genome evolution as it can lead to coinfections creating opportunities for lateral gene transfer which in turn could affect the interaction with the tsetse host.
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http://dx.doi.org/10.1093/molbev/msv077DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4833065PMC
August 2015