  Les facteurs de virulence d’Actinobacillus pleuropneumoniae, l’agent étiologique de la pleuropneumonuie porcineVanden Bergh, Philippe  ; Fett, Thomas ; Zecchinon, Laurent et alin 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 ▲] Detailed reference viewed: 44 (5 ULg)Probing of Actinobacillus pleuropneumoniae ApxIIIA toxin-dependent cytotoxicity towards mammalian peripheral blood mononucleated cellsVanden Bergh, Philippe ; Zecchinon, Laurent ; Fett, Thomas et alin 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 ▲] Detailed reference viewed: 33 (3 ULg)Mannheimia haemolytica leukotoxin-induced cytolysis of caprine (Capra hircus) leukocytes is mediated by the CD18 subunit of beta2-integrinsFett, Thomas ; Zecchinon, Laurent ; Vanden Bergh, Philippe et alin 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 ▲] Detailed reference viewed: 17 (6 ULg)The wild boar (Sus scrofa) Lymphocyte function-associated antigen-1 (CD11a/CD18) receptor : cDNA sequencing, structure analysis and comparison with homologuesVanden Bergh, Philippe ; Zecchinon, Laurent ; Fett, Thomas et alin 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 ▲] Detailed reference viewed: 19 (3 ULg)Key roles of LFA-1 in leukocyte migration and immune responseZecchinon, Laurent ; Fett, Thomas ; Vanden Bergh, Philippe et alin Clinical & Applied Immunology Reviews (2006), 6 Detailed reference viewed: 14 (1 ULg)Anatomy of the Lymphocyte function-associated antigen-1Zecchinon, Laurent ; Fett, Thomas ; Vanden Bergh, Philippe et alin Clinical & Applied Immunology Reviews (2006), 6 Detailed reference viewed: 16 (2 ULg)LFA-1 and associated diseases: the dark side of a receptorZecchinon, Laurent ; Fett, Thomas ; Vanden Bergh, Philippe et alin Clinical & Applied Immunology Reviews (2006), 6 Detailed reference viewed: 16 (1 ULg)Bind another day: the LFA-1/ICAM-1 interation as therapeutic targetZecchinon, Laurent ; Fett, Thomas ; Vanden Bergh, Philippe et alin Clinical & Applied Immunology Reviews (2006), 6 Detailed reference viewed: 14 (4 ULg)The CD11a partner in Sus scrofa lymphocyte function-associated antigen-1 (LFA-1) : mRNA cloning, structure analysis and comparison with mammalian homologsVanden Bergh, Philippe ; Fett, Thomas ; Zecchinon, Laurent et alin BMC Veterinary Research (2005) Detailed reference viewed: 13 (7 ULg) |
||
