1,721,190 research outputs found
Association between <i>IL1</i> gene polymorphism and human African trypanosomiasis in populations of sleeping sickness foci of southern Cameroon
Full text linkBackgroundHuman African Trypanosomiasis (HAT) is a neglected tropical disease caused by infections due to Trypanosoma brucei subspecies. In addition to the well-established environmental and behavioural risks of becoming infected, there is evidence for a genetic component to the response to trypanosome infection. We undertook a candidate gene case-control study to investigate genetic associations further.MethodologyWe genotyped one polymorphism in each of seven genes (IL1A, IL1RN, IL4RN, IL6, HP, HPR, and HLA-G) in 73 cases and 250 controls collected from 19 ethno-linguistic subgroups stratified into three major ethno-linguistic groups, 2 pooled ethno-linguistic groups and 11 ethno-linguistic subgroups from three Cameroonian HAT foci. The seven polymorphic loci tested consisted of three SNPs, three variable numbers of tandem repeat (VNTR) and one INDEL.ResultsWe found that the genotype (TT) and minor allele (T) of IL1A gene as well as the genotype 1A3A of IL1RN were associated with an increased risk of getting Trypanosoma brucei gambiense and develop HAT when all data were analysed together and also when stratified by the three major ethno-linguistic groups, 2 pooled ethno-linguistic subgroups and 11 ethno-linguistic subgroups.ConclusionThis study revealed that one SNP rs1800794 of IL1A and one VNTR rs2234663 of IL1RN were associated with the increased risk to be infected by Trypanosoma brucei gambiense and develop sleeping sickness in southern Cameroon. The minor allele T and the genotype TT of SNP rs1800794 in IL1A as well as the genotype 1A3A of IL1RN rs2234663 VNTR seem to increase the risk of getting Trypanosoma brucei gambiense infections and develop sleeping sickness in southern Cameroon.</div
Differences in gene expression profiles in early and late stage rhodesiense HAT individuals in Malawi.
Full text linkT. b. rhodesiense is the causative agent of Rhodesian human African trypanosomiasis (r-HAT) in Malawi. Clinical presentation of r-HAT in Malawi varies between foci and differs from East African HAT clinical phenotypes. The purpose of this study was to gain more insights into the transcriptomic profiles of patients with early stage 1 and late stage 2 HAT disease in Malawi. Whole blood from individuals infected with T. b. rhodesiense was used for RNA-Seq. Control samples were from healthy trypanosome negative individuals matched on sex, age range, and disease foci. Illumina sequence FASTQ reads were aligned to the GRCh38 release 84 human genome sequence using HiSat2 and differential analysis was done in R Studio using the DESeq2 package. XGR, ExpressAnalyst and InnateDB algorithms were used for functional annotation and gene enrichment analysis of significant differentially expressed genes. RNA-seq was done on 23 r-HAT case samples and 28 healthy controls with 7 controls excluded for downstream analysis as outliers. A total of 4519 genes were significant differentially expressed (p adjusted <0.05) in individuals with early stage 1 r-HAT disease (n = 12) and 1824 genes in individuals with late stage 2 r-HAT disease (n = 11) compared to controls. Enrichment of innate immune response genes through neutrophil activation was identified in individuals with both early and late stages of the disease. Additionally, lipid metabolism genes were enriched in late stage 2 disease. We further identified uniquely upregulated genes (log2 Fold Change 1.4-2.0) in stage 1 (ZNF354C) and stage 2 (TCN1 and MAGI3) blood. Our data add to the current understanding of the human transcriptome profiles during T. b. rhodesiense infection. We further identified biological pathways and transcripts enriched than were enriched during stage 1 and stage 2 r-HAT. Lastly, we have identified transcripts which should be explored in future research whether they have potential of being used in combination with other markers for staging or r-HAT
Towards novel treatment options for human and animal trypanosomiasis : from mechanistic insights in antiparasitic compounds to immunological aspects of early infection
No full textAbstract: Human African trypanosomiasis is a neglected tropical disease caused by the tsetse fly-transmitted unicellular protozoa Trypanosoma brucei gambiense and T. b. rhodesiense. Inoculation of the parasite into the skin results in infection of the host. The first stage of the disease is characterized by non-specific flu-like symptoms due to parasite multiplication in the lymphatics and the bloodstream. Parasite invasion of the central nervous system causes severe neurological symptoms. A wide range of other trypanosome species are responsible for disease in wild and domestic animals causing a widespread socioeconomic problem. The therapies that are currently available are limited in number and face disadvantages of toxicity and drug resistance. Despite decades of research, effective vaccines to protect humans and animals from infection are still lacking. In addition, asymptomatic individuals who remain undiagnosed and hence untreated can still contribute to disease transmission. The development of novel treatment strategies will therefore be crucial to achieve disease elimination. The first aim of this thesis was to evaluate and characterize novel anti-trypanosomal compounds. The medicinal chemistry group of the UGent developed a series of nucleoside analogues based on structural elements of the natural nucleoside antibiotics tubercidin and cordycepin, which were previously shown to have high antiparasitic potency but accompanied by extreme host toxicity. We identified 2 promising nucleoside analogues with high activity against Stage-II disease. Mechanistic evaluation using a whole-genome RNAi library identified TbAT1, ADKIN and 4EIP as involved in their mode-of-action. Evaluation of the adenosine analogues for the treatment of animal trypanosomiasis was able to identify compounds showing a broad activity profile across multiple parasite species/strains. The second aim was to characterize the early immunological events that occur upon the bite of an infected tsetse fly to gather the scientific knowledge necessary to develop novel intervention strategies based on the host-parasite interplay. Neutrophils were previously identified as being rapidly recruited to the site of infection, exhibiting a surprising pro-parasitic response. Detailed in vitro and in vivo analysis of the role of the neutrophil showed that neutrophils become activated upon parasitic stimulation but without a negative impact om parasite replication. In naturally infected mouse models, neutrophils play a role in parasite retention at the site of infection and impact on systemic organ colonization. Analysis of parasite burdens in various tissues identified the lungs as a site of strong parasite proliferation pointing to a potential role as parasitic tissue reservoir. Parasite presence resulted in a large influx of immune cells and change in the transcriptional profile, however, without detrimental effect on lung function. Depletion of specific immune cell subsets including eosinophils, NK cells and IgM+ B cells may underly the increased susceptibility of patients to opportunistic infections
Infection and drug resistance in visceral leishmaniasis : sand fly transmission and entry in host macrophages
No full textAbstract: abstract not availabl
Bioluminescent and molecular tracking of treatment failure in drug-susceptible and -resistent visceral leishmaniasis models
No full textPharmacology of novel drugs against visceral leishmaniasis and African trypanosomiasis
No full textAbstract: Visceral leishmaniasis (VL) and human African trypanosomiasis (HAT) are tropical neglected diseases caused by the respective parasites, Leishmania infantum or L. dononani and Trypanosoma brucei gambiense or T. b. rhodesiense. These parasite species can cause serious infections resulting in serious clinical symptoms and eventual death when left untreated. Current treatment options for VL and HAT are less than adequate as they lack efficacy, are not devoid of adverse effects, and suffer from an increasing incidence of treatment failure. Hence, new drugs are needed, and multiple efforts have recently resulted in the identification of nitroimidazoles, oxaboroles and aminopyrazoles as promising antileishmanial lead series and of pyrazolopyrimidinones as a potential class of antitrypanosomal compounds. The first aim was to evaluate the antiparasitic effects of these novel compounds to assess their further potential in the field. The novel antileishmanial lead series were shown to have killing potential both in vitro and in vivo, and were additionally effective in strains resistant to current antileishmanial drugs. The excellent in vitro activity of antitrypanosomal pyrazolopyrimidinones did not translate in mouse models, with inadequate parasite clearance in an acute first-stage infection model and with additional toxicity issues in the chronic second-stage disease model. Improvement of this lead series is necessary before considering further development. The second aim was to determine the mechanism-of-action (MoA) and mode-of-resistance (MoR) of the selected lead series. A number of techniques was used to unravel the drug target of the antileishmanials, including resistance selection followed by whole-genome sequencing, selection of a genome-wide overexpression library (Cosmid-sequencing), metabolomics, and an upcoming proteomics technique, named drug affinity responsive target stability (DARTS). These did not result in the unequivocal deconvolution of the drug target but identified multiple genes putatively involved in the MoA and MoR of the drugs. The MoA of the pyrazolopyrimidinones, on the other hand, was studied using a whole-genome knockdown library combined with an untargeted metabolomics approach. The S-adenosylmethionine (AdoMet) pathway was found to be commonly perturbed, suggesting its involvement in the MoA of the compound. Single gene knockdown and overexpression experiments could not yet identify the drug target. To conclude, it is clear that the nitroimidazoles, aminopyrazoles and oxaboroles are very promising and could become the next antileishmanial drugs on the market. Rapid resistance development in the field might not be a primary issue and implementation of these drugs in combination regimens might be possible as the MoA of each series is clearly distinct and differs from the conventional antileishmanial drugs. However, the MoA and MoR of these series need to be further explored with complementary techniques. The pyrazolopyrimidinones, on the contrary, need to be further optimized to achieve an enhanced efficacy in the two stages of HAT disease. The identification of the AdoMet pathway as potential drug target may help in the discovery and synthesis of more potent and safer alternatives
Characterizing the bone marrow as a parasitological niche responsible for antileishmanial treatment failure
No full textAbstract: Visceral leishmaniasis (VL) is a lethal parasitic disease caused by the intracellular protozoan Leishmania and is transmitted through the bites of sand flies. In the vertebrate host, parasites infect cells of the liver, spleen and bone marrow (BM). Treatment options are scarce, as are novel leads in the R&D pipeline. Moreover, toxicity, resistance and post-treatment relapse are common and currently no effective test-of-cure exists. There is no human vaccine available and knowledge on protective immunity is limited. All of these obstruct disease elimination and constitute a major clinical concern. In this thesis, a specific cell type was uncovered as source of relapse, namely the long-term hematopoietic stem cell (LT-HSC) in the BM. An enormous number of parasites reside within this hospitable niche that is characterized by low oxidative burst levels and a higher tolerance to antileishmanial drugs. Infected LT-HSC express a unique transcriptional signature, termed StemLeish. Cross-species analyses revealed significant overlap with human VL and HIV co-infected blood transcriptomes. Using siRNA silencing, knockdown of major upregulated StemLeish genes Rgs1, Cxcr4, Ell2, Vav1 and Twistnb confirmed their prominence in regulating LT-HSC infection. Cxcr4 proved important for the observed decrease in oxidative burst, suggesting a central position of this gene in shaping the LT-HSC niche, corroborated by in vivo therapeutic exploration. In LT-HSC, amastigotes rapidly enter quiescence, a phenotype with a higher capacity to survive antileishmanial treatment, providing an informal link to relapse. Parasites that transitioned through quiescence displayed an increased cellular infectivity and high sand fly transmission capacity. Transcriptional profiling revealed a novel set of markers and potential drivers of quiescence. Lastly, the impact of VL on B cell lymphopoiesis and humoral immunity was investigated. Corroborating the documented VL clinical manifestation of polyclonal hypergammaglobulinemia, infection was found to increase B cell progenitors in the BM, and all analyzed B cell subtypes of the spleen. Using immunization against a fluorescent heterologous antigen, it was shown that VL infection does not impair humoral immune memory. Surprisingly, the B cell interacts with Leishmania, carrying amastigotes, extracellularly attached while remaining in a resting, non-replicative state. Collectively, the results in this thesis deliver unprecedented insights regarding post-treatment relapse and humoral immunity during VL infection, providing novel drug targets and biomarkers for both host-directed and parasite-directed therapeutics using differential genes from quiescent amastigotes residing in a relapse-prone niche. This data will have a direct impact on drug screening efforts tweaked to overcome relapse
Drug-resistance in visceral leishmaniasis : impact on parasite infectivity in the vertebrate host and sand fly vector
No full textAbstract: Visceral leishmaniasis (VL) is causing 50,000 to 90,000 new cases annually and more than 20,000 deaths which makes it the deadliest parasitic disease after malaria. In the absence of a successful vaccine, the main VL control strategy is dependent on chemotherapy, however, only a few antileishmanial treatment options are available. Miltefosine (MIL) is currently the only oral drug for VL but is failing to fully clear parasites in an increasing number of patients. These treatment failures could initially not be linked to the emergence of resistance, although more recently a few MIL-resistant (MIL-R) clinical isolates have been described. In order to safeguard the use of MIL for future VL therapies, it is essential to evaluate the impact of MIL-resistance on parasite fitness in the vertebrate host and sand fly vector as this could indicate the potential spread of resistant parasites into the population. In accordance with previous studies using a laboratory MIL-R L.infantum, a decreased infectivity of the vertebrate host was observed for a natural MIL-R L. infantum. However, no impact on the development of the parasite in the sand fly vector was observed. These results indicate that the impact of resistance on parasite fitness in the vertebrate host and insect vector may not necessarily be the same and indicate the potential transmission of MIL-R parasites. To enable a combined study of the infection dynamics and underlying immunological events for differential in vivo infectivity and drug efficacy, firefly luciferase (PpyRE9) / red fluorescent protein (DsRed) double-reporter strains were generated of laboratory MIL-R and syngeneic MIL-sensitive (MIL-S) Leishmania infantum. Results show that MIL-R parasites induce an increased innate immune response that is characterized by enhanced influx and infection of neutrophils, monocytes and dendritic cells in the liver and elevated serum IFN-? levels, finally resulting in a relatively lower burden of MIL-R parasites in liver macrophages. The elevated IFN-? levels were shown to originate from an increased response of hepatic NK and NKT cells to the MIL-R parasites which contributed to the attenuated MIL-R phenotype. In addition, it was demonstrated that the presence of MIL could increase the in vivo fitness of MIL-R parasites by lowering NK and NKT cell activation, leading to a reduced IFN-? production. These results highlight the potential risk of MIL treatment in sustaining infections with resistant parasites. Close monitoring of parasite drug susceptibility and adjusted treatment protocols would therefore be beneficial
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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