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See detailMolecular evidence of Anaplasma phagocytophilum in wild boar (Sus scrofa) in Belgium
Nahayo, Adrien; Bardiau, Marjorie ULg; Volpe, Rosario ULg et al

in BMC Veterinary Research (2014), 10(80),

Anaplasma phagocytophilum is a tick-borne pathogen of veterinary and human importance. Both ticks as vectors and vertebrates as reservoir hosts are essential for the cycle maintenance of this bacterium ... [more ▼]

Anaplasma phagocytophilum is a tick-borne pathogen of veterinary and human importance. Both ticks as vectors and vertebrates as reservoir hosts are essential for the cycle maintenance of this bacterium. Currently, the whole range of animal species reservoirs for A. phagocytophilum in natural environment is still unknown. Therefore, the aim of this study was to estimate the prevalence of infection with A. phagocytophilum in the wild boar population in southern Belgium. [less ▲]

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See detailHepatitis E virus infection in suids and cervids in southern Belgium
Thiry, Damien ULg; Mauroy, Axel ULg; Fett, Thomas ULg et al

Conference (2014, April)

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See detailIngénierie génétique d'une β2-intégrine LFA-1 bovine résistante à la leucotoxine de Mannheimia haemolytica
Fett, Thomas ULg

Doctoral thesis (2012)

Domesticated bovines are known since decades to be prone to bacterial pneumonias. Among the causative agents, a consensus emerged stating that Mannheimia haemolytica is the most frequent bacterium ... [more ▼]

Domesticated bovines are known since decades to be prone to bacterial pneumonias. Among the causative agents, a consensus emerged stating that Mannheimia haemolytica is the most frequent bacterium isolated from bovine lungs throughout the world. Moreover, it appeared that its virulence specifically targets ruminant lungs in vivo and ruminant leucocytes in vitro. When the thesis was started, the two main actors underlying this species-specific virulence were known: the leukotoxin (LKT) on the pathogen side and the beta2-integrin LFA-1 on the host side. The objective of the thesis was to contribute to the understanding of the LKT/LFA 1 interaction at the molecular level. Using a between-species perspective, we showed that (i) the CD11a subunit of the LFA-1 heterodimer was not involved in the LKT-specificity for ruminant LFA-1, (ii) the EGF-3 module within the CD18 controls the susceptibility of any given CD18 to LKT and (iii) a non cleavable signal peptide conjugated to a LKT susceptible EGF-3-containing CD18 exacerbates LKT pronecrotic effects. [less ▲]

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See detailPorcine CD18 mediates Actinobacillus pleuropneumoniae ApxIII species-specific toxicity
Vanden bergh, Philippe; Zecchinon, Laurent; Fett, Thomas ULg et al

in Veterinary Research (2009), 40(4), 33

Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, produces Apx toxins that are recognized as major virulence factors. Recently, we showed that ApxIIIA-cytotoxic activity ... [more ▼]

Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, produces Apx toxins that are recognized as major virulence factors. Recently, we showed that ApxIIIA-cytotoxic activity specifically targets Sus scrofa leukocytes. Since both LtxA from Aggregatibacter actinomycetem comitans (aggressive periodontitis in humans) and LktA from Mannheimia haemolytica (pneumonia in ruminants) share this characteristic, respectively towards human and ruminant leukocytes, and because both use the CD18 subunit to interact with their respective LFA-1, we hypothesized that ApxIIIA was likely to bind porcine CD18 to exercise its deleterious effects on pig leukocytes. A beta(2)-integrin-deficient ApxIIIA-resistant human erythroleukemic cell line was transfected either with homologous or heterologous CD11a/ CD18 heterodimers using a set of plasmids coding for human (ApxIIIA-resistant), bovine (-resistant) and porcine (-susceptible) CD11a and CD18 subunits. Cell preparations that switched from ApxIIIA-resistance to -susceptibility were then sought to identify the LFA-1 subunit involved. The results showed that the ApxIIIA-resistant recipient cell line was rendered susceptible only if the CD18 partner within the LFA-1 heterodimer was that of the pig. It is concluded that porcine CD18 is necessary to mediate A. pleuropneumoniae ApxIIIA toxin-induced leukolysis. [less ▲]

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See detailLa mannheimiose : d’une liaison (moléculaire) fatale à une des principales maladies d’élevage des ruminants
Fett, Thomas ULg; Zecchinon, Laurent; Vanden Bergh, Philippe et al

in Annales de Médecine Vétérinaire (2009), 153(1), 31-53

Les pneumonies bactériennes constituent un problème majeur dans l'élevage et l'engraissement des bovins, avec des répercussions très élevées en termes de morbidité et de mortalité. Parmi les différentes ... [more ▼]

Les pneumonies bactériennes constituent un problème majeur dans l'élevage et l'engraissement des bovins, avec des répercussions très élevées en termes de morbidité et de mortalité. Parmi les différentes causes biologiques recensées, Mannheimia haemolytica tient le haut de l’affiche puisqu’elle est connue comme agent pathogène compliquant principal, voire systématique. Une de ses particularités est qu’elle ne déclenche de pneumonie broncho-alvéolaire fibrino-hémorragique que chez les ruminants. Les lésions observées résultent d’une nécrose en masse des neutrophiles et macrophages et du relarguage de leurs différents constituants. Au niveau moléculaire, cette spécificité trouve son origine dans l’intimité de la liaison entre la leucotoxine, le facteur de virulence majeur de la bactérie, et la sous-unité CD18 des récepteurs de surface leucocytaires bêta2-intégrines. La revue décrit cette liaison et ses conséquences aux niveaux macroscopique et microscopique, avant de faire le point sur les dernières avancées de la recherche et d’ébaucher quelques perspectives thérapeutiques. [less ▲]

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See detailLes facteurs de virulence d’Actinobacillus pleuropneumoniae, l’agent étiologique de la pleuropneumonuie porcine
Vanden Bergh, Philippe ULg; Fett, Thomas ULg; Zecchinon, Laurent ULg et al

in Annales de Médecine Vétérinaire (2008), 152(2), 74-96

Porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae is a frequent and highly infectious disease generating significant economic losses related to deficiency in zootechnical profits and ... [more ▼]

Porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae is a frequent and highly infectious disease generating significant economic losses related to deficiency in zootechnical profits and intensive use of antibiotics. This synthesis aims to review the bacterium elements necessary to pathogenesis development. At first time, we describe activation, secretion and cytotoxic action of Apx toxins, recognized as A. pleuropneumoniae major virulence factors. Then, we develop the other ones which are the lipopolysaccharides, the polysaccharidic capsule, the fimbriae, iron and other nutrients capture systems, various proteases, installation of certain metabolic ways, flagella and the biofilm. [less ▲]

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See detailProbing of Actinobacillus pleuropneumoniae ApxIIIA toxin-dependent cytotoxicity towards mammalian peripheral blood mononucleated cells
Vanden Bergh, Philippe ULg; Zecchinon, Laurent ULg; Fett, Thomas ULg et al

in BMC Research Notes (2008)

BACKGROUND: Actinobacillus pleuropneumoniae, the causative bacterial agent of porcine pleuropneumonia, produces Apx toxins which belong to RTX toxin family and are recognized as the major virulence ... [more ▼]

BACKGROUND: Actinobacillus pleuropneumoniae, the causative bacterial agent of porcine pleuropneumonia, produces Apx toxins which belong to RTX toxin family and are recognized as the major virulence factors. So far, their target receptor(s) has not been identified and the disease cytopathogenesis remains poorly understood. Production of an active Apx toxin and characterization of its toxic activity constitute the premises necessary to the description of its interaction with a potential receptor. From this point of view, we produced an active recombinant ApxIIIA toxin in order to characterize its toxicity on peripheral blood mononucleated cells (PBMCs) isolated from several species. FINDINGS: Toxin preparation exercises a strong cytotoxic action on porcine PBMCs which is directly related to recombinant ApxIIIA since preincubation with polymyxin B does not modify the cytotoxicity rate while preincubation with a monospecific polyclonal antiserum directed against ApxIIIA does. The cell death process triggered by ApxIIIA is extremely fast, the maximum rate of toxicity being already reached after 20 minutes of incubation. Moreover, ApxIIIA cytotoxicity is species-specific because llama, human, dog, rat and mouse PBMCs are resistant. Interestingly, bovine and caprine PBMCs are slightly sensitive to ApxIIIA toxin too. Finally, ApxIIIA cytotoxicity is cell type-specific as porcine epithelial cells are resistant. CONCLUSION: We have produced an active recombinant ApxIIIA toxin and characterized its specific cytotoxicity on porcine PBMCs which will allow us to get new insights on porcine pleuropneumonia pathogenesis in the future. [less ▲]

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See detailMannheimia haemolytica leukotoxin-induced cytolysis of caprine (Capra hircus) leukocytes is mediated by the CD18 subunit of beta2-integrins
Fett, Thomas ULg; Zecchinon, Laurent ULg; Vanden Bergh, Philippe ULg et al

in Microbial Pathogenesis (2008), 45

Mannheimiosis is the major respiratory disease among some ruminants, whereas it is not pathogenic for other mammals, an observation that has been attributed to a specific interaction between Mannheimia ... [more ▼]

Mannheimiosis is the major respiratory disease among some ruminants, whereas it is not pathogenic for other mammals, an observation that has been attributed to a specific interaction between Mannheimia haemolytica leukotoxin (Lkt) and bovine or ovine CD18 subunit of lymphocyte function-associated antigen-1 (LFA-1) and Mac-1. We therefore hypothesized that Lkt utilizes CD18 as its receptor on caprine leukocytes as well. We have transiently transfected the b2-integrins-deficient K-562 cell line with cDNAs encoding caprine CD11a and caprine CD18 to determine the susceptibility of the transfectants to Lktinduced cytolysis. Flow cytometric analysis of the transfectants revealed surface expression of caprine LFA-1 and lysis by Lkt in a concentration-dependent manner whereas the parent cells were not. Moreover, K562 cells expressing caprine CD18 and human or bovine CD11a were also sensitive to Lkt whereas K-562 cells expressing caprine CD11a and human CD18 were not. Taken together, these results indicate that CD18 on caprine leukocytes serves as a receptor for Lkt. [less ▲]

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See detailFlow Cytometric Probing of Mitochondrial Function in Equine Peripheral Blood Mononuclear Cells
Cassart, Dominique ULg; Fett, Thomas ULg; Sarlet, Michaël ULg et al

in BMC Veterinary Research (2007), 3

BACKGROUND: The morphopathological picture of a subset of equine myopathies is compatible with a primary mitochondrial disease, but functional confirmation in vivo is still pending. The cationic dye JC-1 ... [more ▼]

BACKGROUND: The morphopathological picture of a subset of equine myopathies is compatible with a primary mitochondrial disease, but functional confirmation in vivo is still pending. The cationic dye JC-1 exhibits potential-dependent accumulation in mitochondria that is detectable by a fluorescence shift from green to orange. As a consequence, mitochondrial membrane potential can be optically measured by the orange/green fluorescence intensity ratio. A flow cytometric standardized analytic procedure of the mitochondrial function of equine peripheral blood mononuclear cells is proposed along with a critical appraisal of the crucial questions of technical aspects, reproducibility, effect of time elapsed between blood sampling and laboratory processing and reference values. RESULTS: The JC-1-associated fluorescence orange and green values and their ratio were proved to be stable over time, independent of age and sex and hypersensitive to intoxication with a mitochondrial potential dissipator. Unless time elapsed between blood sampling and laboratory processing does not exceed 5 hours, the values retrieved remain stable. Reference values for clinically normal horses are given. CONCLUSION: Whenever a quantitative measurement of mitochondrial function in a horse is desired, blood samples should be taken in sodium citrate tubes and kept at room temperature for a maximum of 5 hours before the laboratory procedure detailed here is started. The hope is that this new test may help in confirming, studying and preventing equine myopathies that are currently imputed to mitochondrial dysfunction. [less ▲]

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See detailThe wild boar (Sus scrofa) Lymphocyte function-associated antigen-1 (CD11a/CD18) receptor : cDNA sequencing, structure analysis and comparison with homologues
Vanden Bergh, Philippe ULg; Zecchinon, Laurent ULg; Fett, Thomas ULg et al

in BMC Veterinary Research (2007), 3

BACKGROUND: The most predominant beta2-integrin lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alphaLbeta2), expressed on all leukocytes, is essential for many adhesive functions of the ... [more ▼]

BACKGROUND: The most predominant beta2-integrin lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alphaLbeta2), expressed on all leukocytes, is essential for many adhesive functions of the immune system. Interestingly, RTX toxin-producing bacteria specifically target this leukocyte beta2-integrin which exacerbates lesions and disease development. RESULTS: This study reports the sequencing of the wild boar beta2-integrin CD11a and CD18 cDNAs. Predicted CD11a and CD18 subunits share all the main structural characteristics of their mammalian homologues, with a larger interspecies conservation for the CD18 than the CD11a. Besides these strong overall similarities, wild boar and domestic pig LFA-1 differ by 2 (CD18) and 1 or 3 (CD11a) substitutions, of which one is located in the crucial I-domain (CD11a, E168D). CONCLUSION: As most wild boars are seropositive to the RTX toxin-producing bacterium Actinobacillus pleuropneumoniae and because they have sustained continuous natural selection, future studies addressing the functional impact of these polymorphisms could bring interesting new information on the physiopathology of Actinobacillus pleuropneumoniae-associated pneumonia in domestic pigs. [less ▲]

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See detailKey roles of LFA-1 in leukocyte migration and immune response
Zecchinon, Laurent ULg; Fett, Thomas ULg; Vanden Bergh, Philippe ULg et al

in Clinical & Applied Immunology Reviews (2006), 6

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See detailAnatomy of the Lymphocyte function-associated antigen-1
Zecchinon, Laurent ULg; Fett, Thomas ULg; Vanden Bergh, Philippe ULg et al

in Clinical & Applied Immunology Reviews (2006), 6

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See detailLFA-1 and associated diseases: the dark side of a receptor
Zecchinon, Laurent ULg; Fett, Thomas ULg; Vanden Bergh, Philippe ULg et al

in Clinical & Applied Immunology Reviews (2006), 6

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See detailBind another day: the LFA-1/ICAM-1 interation as therapeutic target
Zecchinon, Laurent ULg; Fett, Thomas ULg; Vanden Bergh, Philippe ULg et al

in Clinical & Applied Immunology Reviews (2006), 6

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See detailCloning and characterisation of the primary structure of the sheep lymphocyte function-associated antigen-1 alpha subunit
Fett, Thomas ULg; Zecchinon, Laurent ULg; Baise, Etienne ULg et al

in Molecular Immunology (2005), 42(12), 1503-1508

The leukocyte integrins play a critical role in a number of cellular adhesive interactions during the immune response. The ovine cDNA encoding CD1 1a, the predominant a subunit of the beta(2)-integrin ... [more ▼]

The leukocyte integrins play a critical role in a number of cellular adhesive interactions during the immune response. The ovine cDNA encoding CD1 1a, the predominant a subunit of the beta(2)-integrin family, was sequenced and compared with the human, bovine and murine sequences. Despite some focal differences, it shares all the main characteristics of its known mammalian homologues. Along with the ovine CD18-encoding cDNA, which is available for a few months, the sequence data provided here will allow the Ovis aries beta(2)-integrin CD1 1a/CD18 (LEA-1, alpha(L)beta 2) expression in vitro as a tool to examine the specificities of inflammation in the ovine species. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailHow Mannheimia haemolytica defeats host defence through a kiss of death mechanism
Zecchinon, Laurent ULg; Fett, Thomas ULg; Desmecht, Daniel ULg

in Veterinary Research (2005), 36(Mar-Apr), 133-156

Mannheimia haemolytica induced pneumonias are only observed in goats, sheep and cattle. The bacterium produces several virulence factors,whose principal ones are lipopolysaccharide and leukotoxin. The ... [more ▼]

Mannheimia haemolytica induced pneumonias are only observed in goats, sheep and cattle. The bacterium produces several virulence factors,whose principal ones are lipopolysaccharide and leukotoxin. The latter is cytotoxic only for ruminant leukocytes, a phenomenon that is correlated with its ability to bind and interact with the ruminant beta2-integrin Lymphocyte Function-associated Antigen 1. This paper globally reviews all the information available on host-pathogen interactions underlying respiratory mannheimiosis (formerly pasteurellosis), from the stable and the Petri dish to the biochemical cascade of events triggered by the leukotoxin inside ruminant leukocytes. One conclusion can be made: the most widespread cattle respiratory disease with the most important impact on beef production worldwide, is probably due to a tiny ruminant-specific focal variation in the CD18- and/or CD11a-expressing genes. [less ▲]

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See detailMolecular characterization of the caprine (Capra hircus) lymphocyte function-associated antigen-1 alpha subunit
Fett, Thomas ULg; Zecchinon, Laurent ULg; Baise, Etienne ULg et al

in BMC Veterinary Research (2005)

Background: Lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alpha L beta 2) is required for many cellular adhesive interactions during the immune response. Results: The Capra hircus CD11a ... [more ▼]

Background: Lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alpha L beta 2) is required for many cellular adhesive interactions during the immune response. Results: The Capra hircus CD11a-encoding cDNA was sequenced and compared with its human, murine, rat, bovine and ovine counterparts. Despite some focal differences, it shares all the main characteristics of its known mammalian homologues. Conclusion: Therefore, along with the caprine CD18-encoding cDNA, which has been available for a few months, the sequence data revealed here will allow the Capra hircus LFA-1 expression in vitro as a tool to explore the specificities of inflammation in the caprine species. [less ▲]

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See detailMolecular cloning and characterisation of the CD18 partner in ovine (Ovis aries) beta(2)-integrins
Zecchinon, Laurent ULg; Fett, Thomas ULg; Baise, Etienne ULg et al

in Gene (2004), 334

The leukocyte integrins play a critical role in a number of cellular adhesive interactions during the immune response. We describe here the isolation and characterization of the ovine beta(2) (CD18 ... [more ▼]

The leukocyte integrins play a critical role in a number of cellular adhesive interactions during the immune response. We describe here the isolation and characterization of the ovine beta(2) (CD18) subunit, common to the leukocyte beta(2)-integrin family. The deduced 770-amino-acid sequence reveals a transmembrane protein with 81%, 83% and 95% identity with its murine, human and bovine homologues, respectively. Comparisons of CD18 sequences emphasize the functional importance of the beta(2) subunit I-like domain and included metal ion-dependent adhesion site (MIDAS)-like motif and confirm that of the cytoplasmic tail. The data provided here will offer the possibility to explore new avenues in studies based on the ovine model. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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