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Soto Perezchica MM, Guerrero Barrera AL, Avelar Gonzalez FJ, Quezada Tristan T, Macias Marin O. Actinobacillus pleuropneumoniae, surface proteins and virulence: a review. Front Vet Sci 2023; 10:1276712. [PMID: 38098987 PMCID: PMC10720984 DOI: 10.3389/fvets.2023.1276712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Accepted: 10/17/2023] [Indexed: 12/17/2023] Open
Abstract
Actinobacillus pleuropneumoniae (App) is a globally distributed Gram-negative bacterium that produces porcine pleuropneumonia. This highly contagious disease produces high morbidity and mortality in the swine industry. However, no effective vaccine exists to prevent it. The infection caused by App provokes characteristic lesions, such as edema, inflammation, hemorrhage, and necrosis, that involve different virulence factors. The colonization and invasion of host surfaces involved structures and proteins such as outer membrane vesicles (OMVs), pili, flagella, adhesins, outer membrane proteins (OMPs), also participates proteases, autotransporters, and lipoproteins. The recent findings on surface structures and proteins described in this review highlight them as potential immunogens for vaccine development.
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Affiliation(s)
- María M. Soto Perezchica
- Laboratorio de Biología Celular y Tisular, Departamento de Morfología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| | - Alma L. Guerrero Barrera
- Laboratorio de Biología Celular y Tisular, Departamento de Morfología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| | - Francisco J. Avelar Gonzalez
- Laboratorio de Estudios Ambientales, Departamento de Fisiología y Farmacología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| | - Teodulo Quezada Tristan
- Departamento de Ciencias Veterinaria, Centro de Ciencias Agropecuarias, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| | - Osvaldo Macias Marin
- Laboratorio de Biología Celular y Tisular, Departamento de Morfología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
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Hu Y, Jiang C, Zhao Y, Cao H, Ren J, Zeng W, Zhang M, Li Y, He Q, Li W. TurboID screening of ApxI toxin interactants identifies host proteins involved in Actinobacillus pleuropneumoniae-induced apoptosis of immortalized porcine alveolar macrophages. Vet Res 2023; 54:62. [PMID: 37475032 PMCID: PMC10360236 DOI: 10.1186/s13567-023-01194-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 05/30/2023] [Indexed: 07/22/2023] Open
Abstract
Actinobacillus pleuropneumoniae (APP) is a gram-negative pathogenic bacterium responsible for porcine contagious pleuropneumonia (PCP), which can cause porcine necrotizing and hemorrhagic pleuropneumonia. Actinobacillus pleuropneumoniae-RTX-toxin (Apx) is an APP virulence factor. APP secretes a total of four Apx toxins, among which, ApxI demonstrates strong hemolytic activity and cytotoxicity, causing lysis of porcine erythrocytes and apoptosis of porcine alveolar macrophages. However, the protein interaction network between this toxin and host cells is still poorly understood. TurboID mediates the biotinylation of endogenous proteins, thereby targeting specific proteins and local proteomes through gene fusion. We applied the TurboID enzyme-catalyzed proximity tagging method to identify and study host proteins in immortalized porcine alveolar macrophage (iPAM) cells that interact with the exotoxin ApxI of APP. His-tagged TurboID-ApxIA and TurboID recombinant proteins were expressed and purified. By mass spectrometry, 318 unique interacting proteins were identified in the TurboID ApxIA-treated group. Among them, only one membrane protein, caveolin-1 (CAV1), was identified. A co-immunoprecipitation assay confirmed that CAV1 can interact with ApxIA. In addition, overexpression and RNA interference experiments revealed that CAV1 was involved in ApxI toxin-induced apoptosis of iPAM cells. This study provided first-hand information about the proteome of iPAM cells interacting with the ApxI toxin of APP through the TurboID proximity labeling system, and identified a new host membrane protein involved in this interaction. These results lay a theoretical foundation for the clinical treatment of PCP.
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Affiliation(s)
- Yaofang Hu
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Changsheng Jiang
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Yueqiao Zhao
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Hua Cao
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Jingping Ren
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Wei Zeng
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Mengjia Zhang
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
- Key Laboratory of Prevention & Control for African Swine Fever and Other Major Pig Diseases, Ministry of Agriculture and Rural Affairs, Wuhan, China
| | - Yongtao Li
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Qigai He
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China.
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China.
- Hubei Hongshan Laboratory, Wuhan, 430070, China.
- Key Laboratory of Prevention & Control for African Swine Fever and Other Major Pig Diseases, Ministry of Agriculture and Rural Affairs, Wuhan, China.
| | - Wentao Li
- National Key Laboratory of Agricultural Microbiology, College of Animal Sciences and Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China.
- The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China.
- Hubei Hongshan Laboratory, Wuhan, 430070, China.
- Key Laboratory of Prevention & Control for African Swine Fever and Other Major Pig Diseases, Ministry of Agriculture and Rural Affairs, Wuhan, China.
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Filipi K, Rahman WU, Osickova A, Osicka R. Kingella kingae RtxA Cytotoxin in the Context of Other RTX Toxins. Microorganisms 2022; 10:518. [PMID: 35336094 PMCID: PMC8953716 DOI: 10.3390/microorganisms10030518] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 02/22/2022] [Accepted: 02/24/2022] [Indexed: 12/04/2022] Open
Abstract
The Gram-negative bacterium Kingella kingae is part of the commensal oropharyngeal flora of young children. As detection methods have improved, K. kingae has been increasingly recognized as an emerging invasive pathogen that frequently causes skeletal system infections, bacteremia, and severe forms of infective endocarditis. K. kingae secretes an RtxA cytotoxin, which is involved in the development of clinical infection and belongs to an ever-growing family of cytolytic RTX (Repeats in ToXin) toxins secreted by Gram-negative pathogens. All RTX cytolysins share several characteristic structural features: (i) a hydrophobic pore-forming domain in the N-terminal part of the molecule; (ii) an acylated segment where the activation of the inactive protoxin to the toxin occurs by a co-expressed toxin-activating acyltransferase; (iii) a typical calcium-binding RTX domain in the C-terminal portion of the molecule with the characteristic glycine- and aspartate-rich nonapeptide repeats; and (iv) a C-proximal secretion signal recognized by the type I secretion system. RTX toxins, including RtxA from K. kingae, have been shown to act as highly efficient 'contact weapons' that penetrate and permeabilize host cell membranes and thus contribute to the pathogenesis of bacterial infections. RtxA was discovered relatively recently and the knowledge of its biological role remains limited. This review describes the structure and function of RtxA in the context of the most studied RTX toxins, the knowledge of which may contribute to a better understanding of the action of RtxA in the pathogenesis of K. kingae infections.
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Affiliation(s)
| | | | | | - Radim Osicka
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (K.F.); (W.U.R.); (A.O.)
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Nahar N, Turni C, Tram G, Blackall PJ, Atack JM. Actinobacillus pleuropneumoniae: The molecular determinants of virulence and pathogenesis. Adv Microb Physiol 2021; 78:179-216. [PMID: 34147185 DOI: 10.1016/bs.ampbs.2020.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, is responsible for high economic losses in swine herds across the globe. Pleuropneumonia is characterized by severe respiratory distress and high mortality. The knowledge about the interaction between bacterium and host within the porcine respiratory tract has improved significantly in recent years. A. pleuropneumoniae expresses multiple virulence factors, which are required for colonization, immune clearance, and tissue damage. Although vaccines are used to protect swine herds against A. pleuropneumoniae infection, they do not offer complete coverage, and often only protect against the serovar, or serovars, used to prepare the vaccine. This review will summarize the role of individual A. pleuropneumoniae virulence factors that are required during key stages of pathogenesis and disease progression, and highlight progress made toward developing effective and broadly protective vaccines against an organism of great importance to global agriculture and food production.
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Affiliation(s)
- Nusrat Nahar
- Institute for Glycomics, Griffith University, Gold Coast, QLD, Australia
| | - Conny Turni
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia
| | - Greg Tram
- Institute for Glycomics, Griffith University, Gold Coast, QLD, Australia
| | - Patrick J Blackall
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia.
| | - John M Atack
- Institute for Glycomics, Griffith University, Gold Coast, QLD, Australia.
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Park BS, Lee N. A bivalent fusion vaccine composed of recombinant Apx proteins shows strong protection against Actinobacillus pleuroneumoniae serovar 1 and 2 in a mouse model. Pathog Dis 2020; 77:5426212. [PMID: 30939190 DOI: 10.1093/femspd/ftz020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 03/31/2019] [Indexed: 11/12/2022] Open
Abstract
Actinobacillus pleuropneumonia (APP) causes porcine pleuropneumoniae, resulting in severe economic losses in the swine industry. Since there are diverse serotypes of APP, it is necessary for vaccines to induce cross-protection. In this report, we developed a bivalent fusion vaccine, the L vaccine composed of ApxIA and ApxIIA fragments. According to the experimental results of the L vaccine, recombinant protein specific-IgG antibody level increased significantly as well as Apx toxin specific-IgG antibody, suggesting toxin-neutralizing effect. Also, the production of both IgG1 and IgG2a indicates this fusion vaccine induces Th1 and Th2 immune reactions. In addition, lymphocytes were proliferated and immune related-cytokines of TNF-α, IL-12, IFN-γ and IL-5 were detected in the serum after the vaccination. The L vaccine showed a perfect cross-protection against APP serovar 1 and 2 that each secrete different Apx exotoxins. These findings reveal that the fusion L vaccine induces specific humoral and cellular immunity, leading to a perfect cross-protection against A. pleuropneumoniae infections in a murine model.
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Affiliation(s)
- Byung-Sun Park
- Technology Institute, KBNP, Inc., Anyang, Gyeonggi, South Korea
| | - Nakhyung Lee
- Technology Institute, KBNP, Inc., Anyang, Gyeonggi, South Korea
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Frey J. RTX Toxins of Animal Pathogens and Their Role as Antigens in Vaccines and Diagnostics. Toxins (Basel) 2019; 11:toxins11120719. [PMID: 31835534 PMCID: PMC6950323 DOI: 10.3390/toxins11120719] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 12/03/2019] [Accepted: 12/04/2019] [Indexed: 01/19/2023] Open
Abstract
Exotoxins play a central role in the pathologies caused by most major bacterial animal pathogens. The large variety of vertebrate and invertebrate hosts in the animal kingdom is reflected by a large variety of bacterial pathogens and toxins. The group of repeats in the structural toxin (RTX) toxins is particularly abundant among bacterial pathogens of animals. Many of these toxins are described as hemolysins due to their capacity to lyse erythrocytes in vitro. Hemolysis by RTX toxins is due to the formation of cation-selective pores in the cell membrane and serves as an important marker for virulence in bacterial diagnostics. However, their physiologic relevant targets are leukocytes expressing β2 integrins, which act as specific receptors for RTX toxins. For various RTX toxins, the binding to the CD18 moiety of β2 integrins has been shown to be host specific, reflecting the molecular basis of the host range of RTX toxins expressed by bacterial pathogens. Due to the key role of RTX toxins in the pathogenesis of many bacteria, antibodies directed against specific RTX toxins protect against disease, hence, making RTX toxins valuable targets in vaccine research and development. Due to their specificity, several structural genes encoding for RTX toxins have proven to be essential in modern diagnostic applications in veterinary medicine.
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Affiliation(s)
- Joachim Frey
- Vetsuisse Facutly, University of Bern, 3012 Bern, Switzerland
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Proteomic Analysis of Novel Components of Nemopilema nomurai Jellyfish Venom: Deciphering the Mode of Action. Toxins (Basel) 2019; 11:toxins11030153. [PMID: 30857234 PMCID: PMC6468547 DOI: 10.3390/toxins11030153] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/01/2019] [Accepted: 03/01/2019] [Indexed: 02/06/2023] Open
Abstract
Nowadays, proliferation of jellyfish has become a severe matter in many coastal areas around the world. Jellyfish Nemopilema nomurai is one of the most perilous organisms and leads to significant deleterious outcomes such as harm to the fishery, damage the coastal equipment, and moreover, its envenomation can be hazardous to the victims. Till now, the components of Nemopilema nomurai venom (NnV) are unknown owing to scant transcriptomics and genomic data. In the current research, we have explored a proteomic approach to identify NnV components and their interrelation with pathological effects caused by the jellyfish sting. Altogether, 150 proteins were identified, comprising toxins and other distinct proteins that are substantial in nematocyst genesis and nematocyte growth by employing two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI/TOF/MS). The identified toxins are phospholipase A2, phospholipase D Li Sic Tox beta IDI, a serine protease, putative Kunitz-type serine protease inhibitor, disintegrin and metalloproteinase, hemolysin, leukotoxin, three finger toxin MALT0044C, allergens, venom prothrombin activator trocarin D, tripeptide Gsp 9.1, and along with other toxin proteins. These toxins are relatively well characterized in the venoms of other poisonous species to induce pathogenesis, hemolysis, inflammation, proteolysis, blood coagulation, cytolysis, hemorrhagic activity, and type 1 hypersensitivity, suggesting that these toxins in NnV can also cause similar deleterious consequences. Our proteomic works indicate that NnV protein profile represents valuable source which leads to better understanding the clinical features of the jellyfish stings. As one of the largest jellyfish in the world, Nemopilema nomurai sting is considered to be harmful to humans due to its potent toxicity. The identification and functional characterization of its venom components have been poorly described and are beyond our knowledge. Here is the first report demonstrating the methodical overview of NnV proteomics research, providing significant information to understand the mechanism of NnV envenomation. Our proteomics findings can provide a platform for novel protein discovery and development of practical ways to deal with jellyfish stings on human beings.
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Hsu CW, Li SC, Chang NY, Chen ZW, Liao JW, Chen TH, Wang JP, Lin JH, Hsuan SL. Involvement of NF-κB in regulation of Actinobacillus pleuropneumoniae exotoxin ApxI-induced proinflammatory cytokine production in porcine alveolar macrophages. Vet Microbiol 2016; 195:128-135. [PMID: 27771058 DOI: 10.1016/j.vetmic.2016.09.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 09/24/2016] [Accepted: 09/27/2016] [Indexed: 10/20/2022]
Abstract
Actinobacillus pleuropneumoniae is a crucial respiratory pathogen that causes fibrinous, hemorrhagic, necrotizing pleuropneumonia in pigs. A. pleuropneumoniae exotoxins (ApxI to IV) are the major virulence factors contributing to A. pleuropneumoniae pathogenesis. Previously, we demonstrated that ApxI induces the expression of proinflammatory cytokines in porcine alveolar macrophages (PAMs) via the mitogen-activated protein kinases (MAPKs) p38 and cJun NH2-terminal kinase (JNK). Nonetheless, the role of nuclear factor (NF)-κB-a transcription factor widely implicated in immune and inflammatory responses-in ApxI-elicited cytokine production has yet to be defined. In the present study, we examined the involvement of NF-κB in ApxI-elicited production of interleukin (IL)-1β, IL-8, and tumor necrosis factor (TNF)-α in PAMs and investigated the correlation between NF-κB and MAPK (p38 and JNK) pathways in this event. The results of Western blot analysis, confocal microscopy, and a DNA binding activity assay revealed that the classical NF-κB pathway was activated by ApxI, as evidenced by the decreased levels of IκB and subsequent NF-κB translocation and activation in ApxI-stimulated PAMs. Moreover, the blocking of ApxI-induced NF-κB activation significantly attenuated the levels of mRNA and protein secretion of IL-1β, IL-8, and TNF-α in PAMs. Notably, the attenuation of JNK activation by a specific inhibitor (SP600125) reduced ApxI-induced NF-κB activation, whereas a p38 blocker (SB203580) had no effect on the NF-κB pathway. Further examination revealed that the level of phosphorylation at serine 536 on the NF-κB p65 subunit was dependent on JNK activity. Collectively, this study, for the first time, demonstrates a pivotal role of NF-κB in ApxI-induced IL-1β, IL-8, and TNF-α production; JNK, but not p38, may positively affect the activation of the classical NF-κB pathway.
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Affiliation(s)
- Chiung-Wen Hsu
- Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC; Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC
| | - Siou-Cen Li
- Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC; Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC
| | - Nai-Yun Chang
- Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC
| | - Zeng-Weng Chen
- Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC
| | - Jiunn-Wang Liao
- Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC
| | - Ter-Hsin Chen
- Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC
| | - Jyh-Perng Wang
- Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC
| | - Jiunn-Horng Lin
- Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC
| | - Shih-Ling Hsuan
- Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC.
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Affiliation(s)
- Sangyong Lim
- Research Division for Biotechnology, Korea Atomic Energy Research Institute, Jeongeup, Korea
| | - Hyunjin Yoon
- Department of Molecular Science and Technology, Department of Applied Chemistry and Biological Engineering, Ajou University, Suwon, Korea
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Simultaneous detection of antibodies against Apx toxins ApxI, ApxII, ApxIII, and ApxIV in pigs with known and unknown Actinobacillus pleuropneumoniae exposure using a multiplexing liquid array platform. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2013; 21:85-95. [PMID: 24226091 DOI: 10.1128/cvi.00451-13] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Surveillance for the presence of Actinobacillus pleuropneumoniae infection in a population plays a central role in controlling the disease. In this study, a 4-plex fluorescent microbead-based immunoassay (FMIA), developed for the simultaneous detection of IgG antibodies to repeat-in-toxin (RTX) toxins (ApxI, ApxII, ApxIII, and ApxIV) of A. pleuropneumoniae, was evaluated using (i) blood serum samples from pigs experimentally infected with each of the 15 known A. pleuropneumoniae serovars or with Actinobacillus suis, (ii) blood serum samples from pigs vaccinated with a bacterin containing A. pleuropneumoniae serovar 1, 3, 5, or 7, and (iii) blood serum samples from pigs with an unknown A. pleuropneumoniae exposure status. The results were compared to those obtained in a previous study where a dual-plate complement fixation test (CFT) and three commercially available enzyme-linked immunosorbent assays (ELISAs) were conducted on the same sample set. On samples from experimentally infected pigs, the 4-plex Apx FMIA detected specific seroconversion to Apx toxins as early as 7 days postinfection in a total of 29 pigs inoculated with 14 of the 15 A. pleuropneumoniae serovars. Seroconversion to ApxII and ApxIII was detected by FMIA in pigs inoculated with A. suis. The vaccinated pigs showed poor humoral responses against ApxI, ApxII, ApxIII, and ApxIV. In the field samples, the humoral response to ApxIV and the A. pleuropneumoniae seroprevalence increased with age. This novel FMIA (with a sensitivity of 82.7% and a specificity of 100% for the anti-ApxIV antibody) was found to be more sensitive and accurate than current tests (sensitivities, 9.5 to 56%; specificity, 100%) and is potentially an improved tool for the surveillance of disease and for monitoring vaccination compliance.
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Chang NY, Chen ZW, Chen TH, Liao JW, Lin CC, Chien MS, Lee WC, Lin JH, Hsuan SL. Elucidating the role of ApxI in hemolysis and cellular damage by using a novel apxIA mutant of Actinobacillus pleuropneumoniae serotype 10. J Vet Sci 2013; 15:81-9. [PMID: 23820218 PMCID: PMC3973769 DOI: 10.4142/jvs.2014.15.1.81] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 04/11/2013] [Indexed: 11/20/2022] Open
Abstract
Exotoxins produced by Actinobacillus (A.) pleuropneumoniae (Apx) play major roles in the pathogenesis of pleuropneumonia in swine. This study investigated the role of ApxI in hemolysis and cellular damage using a novel apxIA mutant, ApxIA336, which was developed from the parental strain A. pleuropneumoniae serotype 10 that produces only ApxI in vitro. The genotype of ApxIA336 was confirmed by PCR, Southern blotting, and gene sequencing. Exotoxin preparation derived from ApxIA336 was analyzed for its bioactivity towards porcine erythrocytes and alveolar macrophages. Analysis results indicated that ApxIA336 contained a kanamycin- resistant cassette inserted immediately after 1005 bp of the apxIA gene. Phenotype analysis of ApxIA336 revealed no difference in the growth rate as compared to the parental strain. Meanwhile, ApxI production was abolished in the bacterial culture supernatant, i.e. exotoxin preparation. The inability of ApxIA336 to produce ApxI corresponded to the loss of hemolytic and cytotoxic bioactivity in exotoxin preparation, as demonstrated by hemolysis, lactate dehydrogenase release, mitochondrial activity, and apoptosis assays. Additionally, the virulence of ApxIA336 appeared to be attenuated by 15-fold in BALB/c mice. Collectively, ApxI, but not other components in the exotoxin preparation of A. pleuropneumoniae serotype 10, was responsible for the hemolytic and cytotoxic effects on porcine erythrocytes and alveolar macrophages.
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Affiliation(s)
- Nai-Yun Chang
- Graduate Institutes of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, Taichung 402, Taiwan, R.O.C
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Global effects of catecholamines on Actinobacillus pleuropneumoniae gene expression. PLoS One 2012; 7:e31121. [PMID: 22347439 PMCID: PMC3275570 DOI: 10.1371/journal.pone.0031121] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 01/03/2012] [Indexed: 11/26/2022] Open
Abstract
Bacteria can use mammalian hormones to modulate pathogenic processes that play essential roles in disease development. Actinobacillus pleuropneumoniae is an important porcine respiratory pathogen causing great economic losses in the pig industry globally. Stress is known to contribute to the outcome of A. pleuropneumoniae infection. To test whether A. pleuropneumoniae could respond to stress hormone catecholamines, gene expression profiles after epinephrine (Epi) and norepinephrine (NE) treatment were compared with those from untreated bacteria. The microarray results showed that 158 and 105 genes were differentially expressed in the presence of Epi and NE, respectively. These genes were assigned to various functional categories including many virulence factors. Only 18 genes were regulated by both hormones. These genes included apxIA (the ApxI toxin structural gene), pgaB (involved in biofilm formation), APL_0443 (an autotransporter adhesin) and genes encoding potential hormone receptors such as tyrP2, the ygiY-ygiX (qseC-qseB) operon and narQ-narP (involved in nitrate metabolism). Further investigations demonstrated that cytotoxic activity was enhanced by Epi but repressed by NE in accordance with apxIA gene expression changes. Biofilm formation was not affected by either of the two hormones despite pgaB expression being affected. Adhesion to host cells was induced by NE but not by Epi, suggesting that the hormones affect other putative adhesins in addition to APL_0443. This study revealed that A. pleuropneumoniae gene expression, including those encoding virulence factors, was altered in response to both catecholamines. The differential regulation of A. pleuropneumoniae gene expression by the two hormones suggests that this pathogen may have multiple responsive systems for the two catecholamines.
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Sadilkova L, Nepereny J, Vrzal V, Sebo P, Osicka R. Type IV fimbrial subunit protein ApfA contributes to protection against porcine pleuropneumonia. Vet Res 2012; 43:2. [PMID: 22240397 PMCID: PMC3276438 DOI: 10.1186/1297-9716-43-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 01/12/2012] [Indexed: 11/28/2022] Open
Abstract
Porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae accounts for serious economic losses in the pig farming industry worldwide. We examined here the immunogenicity and protective efficacy of the recombinant type IV fimbrial subunit protein ApfA as a single antigen vaccine against pleuropneumonia, or as a component of a multi-antigen preparation comprising five other recombinant antigens derived from key virulence factors of A. pleuropneumoniae (ApxIA, ApxIIA, ApxIIIA, ApxIVA and TbpB). Immunization of pigs with recombinant ApfA alone induced high levels of specific serum antibodies and provided partial protection against challenge with the heterologous A. pleuropneumoniae serotype 9 strain. This protection was higher than that engendered by vaccination with rApxIVA or rTbpB alone and similar to that observed after immunization with the tri-antigen combination of rApxIA, rApxIIA and rApxIIIA. In addition, rApfA improved the vaccination potential of the penta-antigen mixture of rApxIA, rApxIIA, rApxIIIA, rApxIVA and rTbpB proteins, where the hexa-antigen vaccine containing rApfA conferred a high level of protection on pigs against the disease. Moreover, when rApfA was used for vaccination alone or in combination with other antigens, such immunization reduced the number of pigs colonized with the challenge strain. These results indicate that ApfA could be a valuable component of an efficient subunit vaccine for the prevention of porcine pleuropneumonia.
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Affiliation(s)
- Lenka Sadilkova
- Institute of Microbiology of the Academy of Sciences of the Czech Republic, v,v,i,, Videnska 1083, CZ-142 20 Prague, Czech Republic.
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Wu CM, Chen ZW, Chen TH, Liao JW, Lin CC, Chien MS, Lee WC, Hsuan SL. Mitogen-activated protein kinases p38 and JNK mediate Actinobacillus pleuropneumoniae exotoxin ApxI-induced apoptosis in porcine alveolar macrophages. Vet Microbiol 2011; 151:372-8. [DOI: 10.1016/j.vetmic.2011.03.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Revised: 03/26/2011] [Accepted: 03/31/2011] [Indexed: 10/18/2022]
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Zhang W, Shao J, Liu G, Tang F, Lu Y, Zhai Z, Wang Y, Wu Z, Yao H, Lu C. Immunoproteomic analysis of bacterial proteins of Actinobacillus pleuropneumoniae serotype 1. Proteome Sci 2011; 9:32. [PMID: 21703014 PMCID: PMC3148531 DOI: 10.1186/1477-5956-9-32] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2010] [Accepted: 06/26/2011] [Indexed: 11/10/2022] Open
Abstract
Background Actinobacillus pleuropneumoniae (APP) is one of the most important swine pathogens worldwide. Identification and characterization of novel antigenic APP vaccine candidates are underway. In the present study, we use an immunoproteomic approach to identify APP protein antigens that may elicit an immune response in serotype 1 naturally infected swine and serotype 1 virulent strain S259-immunized rabbits. Results Proteins from total cell lysates of serotype 1 APP were separated by two-dimensional electrophoresis (2DE). Western blot analysis revealed 21 immunoreactive protein spots separated in the pH 4-7 range and 4 spots in the pH 7-11 range with the convalescent sera from swine; we found 5 immunoreactive protein spots that separated in the pH 4-7 range and 2 in the pH 7-11 range with hyperimmune sera from S259-immunized rabbits. The proteins included the known antigens ApxIIA, protective surface antigen D15, outer membrane proteins P5, subunit NqrA. The remaining antigens are being reported as immunoreactive proteins in APP for the first time, to our knowledge. Conclusions We identified a total of 42 immunoreactive proteins of the APP serotype 1 virulent strain S259 which represented 32 different proteins, including some novel immunoreactive factors which could be researched as vaccine candidates.
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Affiliation(s)
- Wei Zhang
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Jing Shao
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Guangjin Liu
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Fang Tang
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Yan Lu
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Zhipeng Zhai
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Yang Wang
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Zongfu Wu
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Huochun Yao
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Chengping Lu
- Key Laboratory of Animal Disease Diagnostic & Immunology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
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Frey J. The role of RTX toxins in host specificity of animal pathogenic Pasteurellaceae. Vet Microbiol 2011; 153:51-8. [PMID: 21645978 DOI: 10.1016/j.vetmic.2011.05.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 04/29/2011] [Accepted: 05/10/2011] [Indexed: 10/18/2022]
Abstract
RTX toxins are bacterial pore-forming toxins that are particularly abundant among pathogenic species of Pasteurellaceae, in which they play a major role in virulence. RTX toxins of several primary pathogens of the family of Pasteurellaceae are directly involved in causing necrotic lesions in the target organs. Many RTX toxins are known as haemolysins because they lyse erythrocytes in vitro, an effect that is non-specific, but which serves as a useful marker in bacteriological identification and as an easily measurable signal in vitro in experimental studies. More recent studies have shown that the specific targets of most RTX toxins are leukocytes, with RTX toxins binding to the corresponding β-subunit (CD18) of β2 integrins and then exerting cytotoxic activity. After uptake by the target cell, at sub-lytic concentrations, some RTX toxins are transported to mitochondria and induce apoptosis. For several RTX toxins the binding to CD18 has been shown to be host specific and this seems to be the basis for the host range specificity of these RTX toxins. Observations on two very closely related species of the Pasteurellaceae family, Actinobacillus suis, a porcine pathogen particularly affecting suckling pigs, and Actinobacillus equuli subsp. haemolytica, which causes pyosepticaemia in new-born foals (sleepy foal disease), have revealed that they express different RTX toxins, named ApxI/II and Aqx, respectively. These RTX toxins are specifically cytotoxic for porcine and equine leukocytes, respectively. Furthermore, the ApxI and Aqx toxins of these species, when expressed in an isogenetic background in Escherichia coli, are specifically cytotoxic for leukocytes of their respective hosts. These data indicate the determinative role of RTX toxins in host specificity of pathogenic species of Pasteurellaceae.
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Affiliation(s)
- Joachim Frey
- Institute of Veterinary Bacteriology, University of Bern, Laenggasstrasse 122, CH-3012 Bern, Switzerland.
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Chen ZW, Chien MS, Chang NY, Chen TH, Wu CM, Huang C, Lee WC, Hsuan SL. Mechanisms underlying Actinobacillus pleuropneumoniae exotoxin ApxI induced expression of IL-1β, IL-8 and TNF-α in porcine alveolar macrophages. Vet Res 2011; 42:25. [PMID: 21314908 PMCID: PMC3041667 DOI: 10.1186/1297-9716-42-25] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 01/13/2011] [Indexed: 11/12/2022] Open
Abstract
Actinobacillus pleuropneumoniae (A. pleuropneumoniae) causes fibrino-hemorrhagic necrotizing pleuropneumonia in pigs. Production of proinflammatory mediators in the lungs is an important feature of A. pleuropneumoniae infection. However, bacterial components other than lipopolysaccharide involved in this process remain unidentified. The goals of this study were to determine the role of A. pleuropneumoniae exotoxin ApxI in cytokine induction and to delineate the underlying mechanisms. Using real-time quantitative PCR analysis, we found native ApxI stimulated porcine alveolar macrophages (PAMs) to transcribe mRNAs of IL-1β, IL-8 and TNF-α in a concentration- and time-dependent manner. Heat-inactivation or pre-incubation of ApxI with a neutralizing antiserum attenuated ApxI bioactivity to induce cytokine gene expression. The secretion of IL-1β, IL-8 and TNF-α protein from PAMs stimulated with ApxI was also confirmed by quantitative ELISA. In delineating the underlying signaling pathways contributing to cytokine expression, we observed mitogen-activated protein kinases (MAPKs) p38 and cJun NH2-terminal kinase (JNK) were activated upon ApxI stimulation. Administration of an inhibitor specific to p38 or JNK resulted in varying degrees of attenuation on ApxI-induced cytokine expression, suggesting the differential regulatory roles of p38 and JNK in IL-1β, IL-8 and TNF-α production. Further, pre-incubation of PAMs with a CD18-blocking antibody prior to ApxI stimulation significantly reduced the activation of p38 and JNK, and subsequent expression of IL-1β, IL-8 or TNF-α gene, indicating a pivotal role of β2 integrins in the ApxI-mediated effect. Collectively, this study demonstrated ApxI induces gene expression of IL-1β, IL-8 and TNF-α in PAMs that involves β2 integrins and downstream MAPKs.
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Affiliation(s)
- Zeng-Weng Chen
- Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250, Kuo Kuang Road, Taichung, 402, Taiwan, ROC.
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Kristensen BM, Frees D, Bojesen AM. GtxA from Gallibacterium anatis, a cytolytic RTX-toxin with a novel domain organisation. Vet Res 2009; 41:25. [PMID: 19954731 PMCID: PMC2820230 DOI: 10.1051/vetres/2009073] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 12/02/2009] [Indexed: 11/29/2022] Open
Abstract
Gallibacterium anatis is a pathogen in chickens and other avian species where it is a significant cause of salpingitis and peritonitis. We found that bacterial cells and cell-free, filter-sterilised culture supernatant from the haemolytic G. anatis biovar haemolytica were highly cytotoxic towards avian-derived macrophage-like cells (HD11). We obtained the genome sequence of G. anatis 12656-12 and used a rational approach to identify a gene predicted to encode a 2026 amino acid RTX-toxin, which we named GtxA (Gallibacterium toxin). The construction of a gtxA knock-out mutant showed gtxA to be responsible for G. anatis’ haemolytic and leukotoxic activity. In addition, Escherichia coli expressing gtxA and an adjacent acyltransferase, gtxC, became cytolytic. GtxA was expressed during in vitro growth and was localised in the extracellular protein fraction in a growth phase dependent manner. GtxA had an unusual modular structure; the C-terminal 1000 amino acids of GtxA were homologous to the classical pore-forming RTX-toxins in other members of Pasteurellaceae. In contrast, the N-terminal approximately 950 amino acids had few significant matches in sequence databases. Expression of truncated GtxA proteins demonstrated that the C-terminal RTX-domain had a lower haemolytic activity than the full-length toxin, indicating that the N-terminal domain was required for maximal haemolytic activity. Cytotoxicity towards HD11 cells was not detected with the C-terminal alone, suggesting that the N-terminal domain plays a critical role for the leukotoxicity.
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Affiliation(s)
- Bodil Marie Kristensen
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark
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Vanden Bergh PGAC, Zecchinon LLM, Fett T, Desmecht D. Porcine CD18 mediates Actinobacillus pleuropneumoniae ApxIII species-specific toxicity. Vet Res 2009; 40:33. [PMID: 19356397 PMCID: PMC2701182 DOI: 10.1051/vetres/2009016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Accepted: 04/08/2009] [Indexed: 11/15/2022] Open
Abstract
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 actinomycetemcomitans (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 β2−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.
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Actinobacillus pleuropneumoniae serotype 10 derived ApxI induces apoptosis in porcine alveolar macrophages. Vet Microbiol 2009; 135:327-33. [DOI: 10.1016/j.vetmic.2008.09.071] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 08/04/2008] [Accepted: 09/19/2008] [Indexed: 11/22/2022]
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21
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Vanden Bergh PG, Zecchinon LL, Fett T, Desmecht D. Probing of Actinobacillus pleuropneumoniae ApxIIIA toxin-dependent cytotoxicity towards mammalian peripheral blood mononucleated cells. BMC Res Notes 2008; 1:121. [PMID: 19046441 PMCID: PMC2612674 DOI: 10.1186/1756-0500-1-121] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Accepted: 12/01/2008] [Indexed: 11/24/2022] Open
Abstract
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.
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Affiliation(s)
- Philippe Gac Vanden Bergh
- Pathology Department, Faculty of Veterinary Medicine, University of Liege, Colonster Boulevard 20 B43, B-4000 Liege, Belgium.
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Ramjeet M, Cox AD, Hancock MA, Mourez M, Labrie J, Gottschalk M, Jacques M. Mutation in the LPS outer core biosynthesis gene, galU, affects LPS interaction with the RTX toxins ApxI and ApxII and cytolytic activity of Actinobacillus pleuropneumoniae serotype 1. Mol Microbiol 2008; 70:221-35. [PMID: 18713318 DOI: 10.1111/j.1365-2958.2008.06409.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Lipopolysaccharides (LPS) and Apx toxins are major virulence factors of Actinobacillus pleuropneumoniae, a pathogen of the respiratory tract of pigs. Here, we evaluated the effect of LPS core truncation in haemolytic and cytotoxic activities of this microorganism. We previously generated a highly attenuated galU mutant of A. pleuropneumoniae serotype 1 that has an LPS molecule lacking the GalNAc-Gal II-Gal I outer core residues. Our results demonstrate that this mutant exhibits wild-type haemolytic activity but is significantly less cytotoxic to porcine alveolar macrophages. However, no differences were found in gene expression and secretion of the haemolytic and cytotoxic toxins ApxI and ApxII, both secreted by A. pleuropneumoniae serotype 1. This suggests that the outer core truncation mediated by the galU mutation affects the toxins in their cytotoxic activities. Using both ELISA and surface plasmon resonance binding assays, we demonstrate a novel interaction between LPS and the ApxI and ApxII toxins via the core oligosaccharide. Our results indicate that the GalNAc-Gal II-Gal I trisaccharide of the outer core is fundamental to mediating LPS/Apx interactions. The present study suggests that a lack of binding between LPS and ApxI/II affects the cytotoxicity and virulence of A. pleuropneumoniae.
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Affiliation(s)
- Mahendrasingh Ramjeet
- Groupe de recherche sur les maladies infectieuses du porc, Faculté de médecine vétérinaire, Université de Montréal, St-Hyacinthe, QC, Canada J2S 7C6
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Inzana TJ, Champion A. Use of an inhibition enzyme-linked immunosorbent assay for quantification of capsular polysaccharide or proteins in vaccines. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2007; 14:323-7. [PMID: 17267591 PMCID: PMC1828856 DOI: 10.1128/cvi.00302-06] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An inhibition enzyme-linked immunosorbent assay (ELISA) is described for quantification of capsular polysaccharide or proteins in vaccines and other samples containing whole cells or extracts of Actinobacillus pleuropneumoniae. The assay can be used to quantify any antigen that can be purified and for which highly specific antibodies are not available. The assay can be carried out by any laboratory capable of performing an ELISA.
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Affiliation(s)
- Thomas J Inzana
- Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
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Lee KY, Kim DH, Kang TJ, Kim J, Chung GH, Yoo HS, Arntzen CJ, Yang MS, Jang YS. Induction of protective immune responses against the challenge of Actinobacillus pleuropneumoniae by the oral administration of transgenic tobacco plant expressing ApxIIA toxin from the bacteria. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 2006; 48:381-9. [PMID: 17054716 DOI: 10.1111/j.1574-695x.2006.00158.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Actinobacillus pleuropneumoniae is the causative agent of porcine pleuropneumonia. Among the virulence factors, ApxIIA, a bacterial exotoxin, is reportedly expressed in many serotypes and is considered as a candidate for the development of a vaccine against the bacterial infection. Previously, we isolated a field strain of A. pleuropneumoniae serotype 2 in Korea and characterized its exotoxins to develop an oral vaccine. In this study, we initially confirmed the immunogenicity of ApxIIA expressed in Escherichia coli. We then developed transgenic tobacco expressing ApxIIA and tested its efficacy to induce a protective immune response against A. pleuropneumoniae infection after oral administration of the plant powder. We observed that protective immune responses were induced in mice after oral administration of the plant powder once a week for 4 weeks. Immunoassays revealed that the levels of antigen-specific immunoglobulin G against ApxIIA increased in mice that were fed a powder made from the transgenic plant, but not in mice fed a powder made from wild-type tobacco. Additionally, mice fed the transgenic plant powder were protected from an injection of a lethal dose of A. pleuropneumoniae. These results support that the transgenic plant may be a suitable candidate for an oral vaccine that could be used effectively against A. pleuropneumoniae infection.
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Affiliation(s)
- Kyung-Yeol Lee
- Department of Oral Microbiology, School of Dentistry, Chonbuk National University, Chonju, Korea
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Huang H, Zhou R, Fan H, Dan H, Chen M, Yan L, Bei W, Chen H. Generation of monoclonal antibodies and epitope mapping of ApxIVA of Actinobacillus pleuropneumoniae. Mol Immunol 2006; 43:2130-4. [PMID: 16481039 DOI: 10.1016/j.molimm.2005.12.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Revised: 10/28/2005] [Accepted: 12/23/2005] [Indexed: 10/25/2022]
Abstract
To study functions of ApxIV, a species-specific and in vivo inducible RTX toxin identified in Actinobacillus pleuropneumoniae recently, and to develop a diagnostic trial distinguishing the pigs infected naturally and vaccinated with inactivated and/or subunit vaccines, we attempted to prepare monoclonal antibodies against ApxIV. BALB/c mice were immunized with ApxIVAN and ApxIVAC which are N- and C-terminal halvies (814 and 997 amino acids, respectively) of ApxIVA produced in E. coli BL21 (DE3), respectively. Eight monoclonal antibodies were selected, four (designated as 1A8, 1G5, 3E7 and 4H9) against ApxIVAN and another four (named as 1B12, 2E5, 4D8 and 4G2) against ApxIVAC. Western blot and ELISA additivity assays suggested that all monoclonal antibodies except 1A8 are specific to the corresponding immunogen, 1A8 reacts with both immunogens which have a overlapping region of 156 residues. ELISA additivity tests revealed that at least five epitopes in ApxIV are defined by eight monoclonal antibodies, two between 1 and 866 amino acids, one between 867 and 1022 amino acids and two between 1023 and 1863 amino acids. In conclusion, we have succeeded in producing eight monoclonal antibodies, which react with five different epitopes of ApxIV.
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Affiliation(s)
- Hongliang Huang
- Division of Animal Infectious Disease in the State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, PR China
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Hilbink F, de Lisle GW, Penrose M, Aldersley B, Carman M. Actinobacillus pleuropneumoniae in New Zealand pigs. N Z Vet J 2005; 40:173-5. [PMID: 16031685 DOI: 10.1080/00480169.1992.35726] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Tumamao JQ, Bowles RE, van den Bosch H, Klaasen HLBM, Fenwick BW, Blackall PJ. An evaluation of the role of antibodies to Actinobacillus pleuropneumoniae serovar 1 and 15 in the protection provided by sub-unit and live streptomycin-dependent pleuropneumonia vaccines. Aust Vet J 2005; 82:773-80. [PMID: 15648941 DOI: 10.1111/j.1751-0813.2004.tb13248.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To evaluate the serological response of pigs receiving either the Porcilis APP vaccine or a modified live vaccine based on a streptomycin-dependent (SD) strain of Actinobacillus pleuropneumoniae, and then challenged with an Australian isolate of A. pleuropneumoniae of either serovar 1 or 15 as a means of understanding the protection provided by both vaccines against serovar 1 but not against serovar 15. DESIGN The serological tests evaluated were serovar-specific polysaccharide ELISA tests (for serovar 1 and 15), ELISA tests for antibodies to three A. pleuropneumoniae toxins (ApxI, ApxII and ApxIII) as well as to a 42 kDa outer membrane protein (OMP), a haemolysin neutralisation (HN) assay and immunoblotting. The tests were used to detect antibodies in vaccinated pigs that had been shown to be protected against serovar 1 but not serovar 15. RESULTS In the polysaccharide antigen ELISA assays, both vaccines resulted in a significant rise in the titre in the serovar 1 ELISA but not the serovar 15 ELISA. The Porcilis APP vaccinated pigs showed a significant response in the ApxI, ApxIII and 42 kDa OMP ELISA. In the ApxII ELISA, all pigs tested (the Porcilis APP vaccinates and the controls) were positive on entry to the trial. In the HN assay, the Porcilis APP vaccinated pigs showed a significant response after one dose while the SD vaccinated pigs required two doses of vaccine before a marked rise in titre was induced. Immunoblotting revealed that neither vaccine generated antibodies that recognised the ApxIII produced by serovar 15. CONCLUSIONS The failure of these vaccines to provide protection against serovar 15 may be due to novel virulence factors possessed by serovar 15, significant differences between the ApxIII toxin of serovar 15 and those present in the Porcilis APP vaccine or failure by both vaccines to induce antibodies to the serovar 15 specific polysaccharide.
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Affiliation(s)
- J Q Tumamao
- Agency for Food and Fibre Sciences, Queensland Department of Primary Industries, Animal Research Institute, Yeerongpilly, Queensland 4105.
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Christensen H, Bisgaard M. Revised definition of Actinobacillus sensu stricto isolated from animals. A review with special emphasis on diagnosis. Vet Microbiol 2004; 99:13-30. [PMID: 15019108 DOI: 10.1016/j.vetmic.2003.12.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2003] [Accepted: 12/02/2003] [Indexed: 11/16/2022]
Abstract
The taxonomy of the members of the genus Actinobacillus associated with animals has been reviewed with focus on classification and identification including molecular based characterization, typing and identification. Out of the 22 species or species like taxa reported as Actinobacillus, 19 are associated with animals. When classified on the basis of 16S rRNA sequence based phylogenetic analysis, DNA-DNA hybridizations and phenotypic analysis, Actinobacillus sensu stricto is restricted to include A. lignieresii, A. pleuropneumoniae, A. equuli subsp. equuli, A. equuli subsp. haemolyticus (taxon 11 of Bisgaard), A. hominis, A. suis, A. ureae, A. arthritidis (taxon 9 of Bisgaard), Actinobacillus genomospecies 1 and 2 and the taxa 8 and 26 of Bisgaard. The remaining 11 species of Actinobacillus are unrelated to A. sensu stricto and should consequently be grouped with other genera or be renamed as new genera depending on new data. Identification of members of Actinobacillus at species level is possible through phenotypic characterization combined with information on host of isolation. PCR tests are available for specific detection of A. pleuropneumoniae. Only A. pleuropneumoniae is presently considered as a primary pathogen. Based on different types of RTX genes it is possible to PCR type A. pleuropneumoniae to serotype level. PCR might also be used for the specific detection of A. equuli subsp. haemolyticus. Epidemiological investigations and surveillance have so far included serotyping, multilocus enzyme electrophoresis (MLEE), ribotyping and restriction fragment length profiling.
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Affiliation(s)
- Henrik Christensen
- Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University, Stigbøjlen 4, 1870 Frederiksberg C, Denmark.
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29
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Boekema BKHL, Kamp EM, Smits MA, Smith HE, Stockhofe-Zurwieden N. Both ApxI and ApxII of Actinobacillus pleuropneumoniae serotype 1 are necessary for full virulence. Vet Microbiol 2004; 100:17-23. [PMID: 15135509 DOI: 10.1016/j.vetmic.2003.09.024] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2003] [Revised: 09/18/2003] [Accepted: 09/18/2003] [Indexed: 11/24/2022]
Abstract
Most serotypes of A. pleuropneumoniae produce more than one toxin in vivo. To determine the value of the production of more than one toxin in the development of disease, we tested the pathogenicity of isogenic strains of A. pleuropneumoniae serotype 1 that are mutated in the toxin genes apxIA and/or apxIIA or in the transport genes apxIBD. Bacteria mutated in both apxIA and apxIIA, or in apxIBD, were unable to induce pathological lesions, thereby confirming the conclusion that ApxI and ApxII are essential for the pathogenesis of pleuropneumonia. Infection with isogenic strains lacking either ApxI or ApxII did not consistently lead to pleuropneumonia unlike the parent strain S4074. ApxII seemed at least as important as ApxI for the development of clinical and pathological symptoms. Only one of the four pigs inoculated with a mutant strain unable to produce ApxII developed mild pneumonia whereas two out of the three pigs inoculated with a mutant strain unable to produce ApxI developed more severe lesions. The results indicate that both ApxI and ApxII of A. pleuropneumoniae serotype 1 are necessary for full virulence.
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Affiliation(s)
- Bouke K H L Boekema
- Division of Infectious Diseases and Food Chain Quality, Institute for Animal Science and Health, ID-Lelystad, P.O. Box 65, 8200 AB Lelystad, The Netherlands.
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30
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Burdychova R, Rychtera M, Horvath R, Dendis M, Bartos M. Expression of Actinobacillus pleuropneumonia gene coding for Apx I protein in Escherichia coli. FEMS Microbiol Lett 2004; 230:9-12. [PMID: 14734159 DOI: 10.1016/s0378-1097(03)00622-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
This study presents cloning and expression of Actinobacillus pleuropneumoniae Apx I toxin in Escherichia coli expression system to produce fusion protein for the subsequent immunological studies. The gene coding Apx I toxin was amplified from the A. pleuropneumoniae serotype 10 DNA using polymerase chain reaction and cloned to vector under the control of strong, inducible T7 promoter. The presence of insert was confirmed by PCR screening and sequencing after the propagation of recombinant DNA in E. coli cells. The gene coding A. pleuropneumoniae Apx I toxin was extended with a segment to encode a polyhistidine tag linked to its C-terminal sequence allowing a one-step affinity purification of the complex with Ni-NTA resin. Expression of the Apx I coding sequence in E. coli resulted in the formation of insoluble inclusion bodies purified according to a standard purification protocol. The ease of this expression system, the powerful single-step purification and low costs make it possible to produce Apx I in large amounts to further study the role of Apx I in physiological processes.
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Affiliation(s)
- Radka Burdychova
- Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno, Czech Republic
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31
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Kuhnert P, Berthoud H, Straub R, Frey J. Host cell specific activity of RTX toxins from haemolytic Actinobacillus equuli and Actinobacillus suis. Vet Microbiol 2003; 92:161-7. [PMID: 12488079 DOI: 10.1016/s0378-1135(02)00353-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We assessed and compared host cell specificity of the haemolytic and cytotoxic activity of the RTX toxins from Actinobacillus equuli, an equine pathogen, and Actinobacillus suis, which is pathogenic for pigs. The two bacterial species are closely related, phenotypically as well as phylogenetically, sharing the same 16S rRNA gene sequence. Both species contain specific protein toxins from the family of pore-forming RTX toxins, however, the two species differ in their RTX toxin profiles. Haemolytic A. equuli contains the operon for the Aqx toxin, whereas A. suis harbours genes for ApxI and ApxII. We tested the toxic activity of the corresponding proteins on erythrocytes as well as on lymphocytes isolated from horse and pig blood. The strength of the haemolytic activity for each of the toxins was independent of the origin of erythrocytes. When testing cytotoxic activity, the Aqx protein showed a higher toxic effect for horse lymphocytes than for porcine lymphocytes. On the other hand, ApxI and ApxII showed a strong cytotoxic effect on porcine lymphocytes and a reduced toxicity for horse lymphocytes; the toxicity of ApxII was generally much lower than ApxI. Our results indicate a host species specificity of the toxic activity of RTX toxins Aqx of A. equuli and ApxI and ApxII of A. suis.
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Affiliation(s)
- P Kuhnert
- Institute of Veterinary Bacteriology, University of Bern, Langgassstrasse 122, CH-3012 Bern, Switzerland.
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32
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Bossé JT, Janson H, Sheehan BJ, Beddek AJ, Rycroft AN, Kroll JS, Langford PR. Actinobacillus pleuropneumoniae: pathobiology and pathogenesis of infection. Microbes Infect 2002; 4:225-35. [PMID: 11880056 DOI: 10.1016/s1286-4579(01)01534-9] [Citation(s) in RCA: 264] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Actinobacillus pleuropneumoniae causes porcine pleuropneumonia, a highly contagious disease for which there is no effective vaccine. This review considers how adhesins, iron-acquisition factors, capsule and lipopolysaccharide, RTX cytotoxins and other potential future vaccine components contribute to colonisation, to avoidance of host clearance mechanisms and to damage of host tissues.
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Affiliation(s)
- Janine T Bossé
- Molecular Infectious Diseases Group, Department of Paediatrics, Faculty of Medicine, Imperial College, St. Mary's Campus, W2 1PG, London, UK.
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33
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Cho WS, Chae C. Expression of the apxIV gene in pigs naturally infected with Actinobacillus pleuropneumoniae. J Comp Pathol 2001; 125:34-40. [PMID: 11437514 DOI: 10.1053/jcpa.2001.0474] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The apxIV gene was detected, by in-situ hybridization with a non-radioactive digoxigenin-labelled probe, in formalin-fixed, paraffin wax-embedded samples of lung tissue from 10 pigs naturally infected with Actinobacillus pleuropneumoniae. A 442 base pair DNA probe of the apxIV gene from A. pleuropneumoniae serotype 2 was generated by the polymerase chain reaction. All 10 pigs infected with A. pleuropneumoniae serotypes 2, 5, 6, or an untypable strain showed a distinct, positive signal in the degenerate alveolar leucocytes in alveolar spaces, and in the dense zone of degenerated cells in granulation tissue surrounding the necrotic areas. Thus, the study demonstrated the presence of the apxIV gene in pleuropneumonic lesions caused by A. pleuropneumoniae.
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Affiliation(s)
- W S Cho
- Department of Veterinary Pathology, College of Veterinary Medicine and School of Agricultural Biotechnology, Seoul National University, Suwon 441-744, Kyounggi-Do, Republic of Korea
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34
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Cho WS, Chae C. Genotypic prevalence of apx1V in Actinobacillus pleuropneumoniae field isolates. J Vet Diagn Invest 2001; 13:175-7. [PMID: 11289219 DOI: 10.1177/104063870101300217] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A total of 90 Actinobacillus pleuropneumoniae field strains from pigs were serotyped by slide agglutination and analyzed for the presence of the apxIV gene by polymerase chain reaction. Of the 90 isolates serotyped, serotypes 2 (47 isolates) and 5 (25 isolates) were the most common, followed by serotype 6 (10 isolates). Three isolates belonged to serotype 7, and 5 isolates could not be typed. All 90 A. pleuropneumoniae field isolates tested carried the apxIV gene. This gene is species specific rather than serotype specific. Therefore, the ApxIV toxin has potential value for use both in vaccines and in diagnostic tests.
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Affiliation(s)
- W S Cho
- Department of Veterinary Pathology, College of Veterinary Medicine, School of Agricultural Biotechnology, Seoul National University, Kyounggi Do, Republic of Korea
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35
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Van Overbeke I, Chiers K, Ducatelle R, Haesebrouck F. Effect of endobronchial challenge with Actinobacillus pleuropneumoniae serotype 9 of pigs vaccinated with a vaccine containing Apx toxins and transferrin-binding proteins. JOURNAL OF VETERINARY MEDICINE. B, INFECTIOUS DISEASES AND VETERINARY PUBLIC HEALTH 2001; 48:15-20. [PMID: 11254095 DOI: 10.1046/j.1439-0450.2001.00419.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The efficacy of a subunit vaccine containing the Apx toxins of Actinobacillus pleuropneumoniae and transferrin-binding proteins was determined. Ten pigs were vaccinated twice with the vaccine. Eight control animals were injected twice with a saline solution. Three weeks after the second vaccination, all pigs were endobronchially inoculated with 10(6.5) colony-forming units (CFU) of an A. pleuropneumoniae serotype 9 strain. In the vaccine group, none of the pigs died after inoculation. Only one pig of the control group survived challenge. Surviving pigs were killed at 7 days after challenge. The mean percentage of affected lung tissue was 64% in the control group and 17% in the vaccine group. Actinobacillus pleuropneumoniae was isolated from the lungs of all animals. The mean bacterial titres of the caudal lung lobes were 5.0 x 10(8) CFU/g in the control group and 3.0 x 10(6) CFU/g in the vaccine group. It was concluded that the vaccine induced partial protection against severe challenge.
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Affiliation(s)
- I Van Overbeke
- Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, University of Gent, Merelbeke, Belgium.
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36
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Nielsen R, van den Bosch JF, Plambeck T, Sørensen V, Nielsen JP. Evaluation of an indirect enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to the Apx toxins of Actinobacillus pleuropneumoniae. Vet Microbiol 2000; 71:81-7. [PMID: 10665536 DOI: 10.1016/s0378-1135(99)00157-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The reference strains of the 12 serotypes of Actinobacillus pleuropneumoniae express one or two of three different RTX exotoxins designated Apx I, Apx II and Apx III. The toxins are important virulence factors. In the present study, ELISAs with purified Apx I, Apx II and Apx III, respectively, as antigen were evaluated as candidates for serological diagnosis of Actinobacillus pleuropneumoniae infection in pigs. The pigs were inoculated with biotype 1, serotypes 1-12, and biotype 2, serotype 14, respectively. A strong humoral antibody response was seen to all the three antigens in most pigs irrespective of the serotype used for inoculation. However, titers to the exotoxins secreted by the serotype used for inoculation were generally highest. The results show that toxin proteins of Actinobacillus pleuropneumoniae are antigenically related and that a correlation between serotype and secretion of exotoxin is not revealed serologically in the ELISA test.
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Affiliation(s)
- R Nielsen
- Danish Veterinary Laboratory, Copenhagen, Denmark
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37
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Abstract
Actinobacillus species are Gram-negative bacteria responsible for several quite distinct disease conditions of animals. The natural habitat of the organisms is primarily the upper respiratory tract and oral cavity. A. lignieresii is the cause of actinomycosis (wooden tongue) in cattle: a sporadic, insidiously-developing granulomatous infection. In sharp contrast is A. pleuropneumoniae which is responsible for a rapidly spreading often fatal pneumonia, common among intensively reared pigs. Detailed investigation of this organism has provided a much clearer picture of the bacterial factors involved in causing disease. A. equuli similarly causes a potent septicaemia in the neonatal foal; growing apparently unrestricted once infection occurs. Other members of the genus induce characteristic pathogenesis in their preferred host, with one, A. actinomycetemcomitans, being a cause of human periodontal disease. This article reviews recent understanding of the taxonomy and bacteriology of the organisms, and the aetiology, pathogenicity, diagnosis and control of animal disease caused by Actinobacillus species.
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Affiliation(s)
- A N Rycroft
- Veterinary Bacteriology Group, Department of Pathology and Infectious Diseases, Royal Veterinary College, Hawkshead Lane, North Mymms, AL9 7TA, UK.
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38
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Oswald W, Konine DV, Rohde J, Gerlach GF. First chromosomal restriction map of Actinobacillus pleuropneumoniae and localization of putative virulence-associated genes. J Bacteriol 1999; 181:4161-9. [PMID: 10400571 PMCID: PMC93915 DOI: 10.1128/jb.181.14.4161-4169.1999] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Combined physical and genetic maps of the genomes of Actinobacillus pleuropneumoniae AP76 (serotype 7 clinical isolate) and of A. pleuropneumoniae ATCC 27088 (serotype 1 reference strain) were constructed by using the restriction endonucleases ApaI, AscI, NotI, and SalI. The chromosome sizes as determined by the addition of estimated fragment sizes were 2.4 Mbp, and both maps had a resolution of approximately 100 kbp. The linkages between the ApaI, AscI, NotI, and SalI fragments and their relative positions were determined by (i) fragment excision and redigestion and (ii) partial digests of defined fragments and Southern blot using end-standing probes. The single SalI site within the chromosome of strain A. pleuropneumoniae AP76 was defined as position 1 of the map; for the map of A. pleuropneumoniae ATCC 27088, the corresponding SalI site was chosen. Putative virulence-associated genes (apx, omlA, sodA, tbpBA, ureC, and a repeat element) and housekeeping genes (glyA, metJ, recA, and rhoAP) were positioned on the physical maps and located on the ApaI and NotI fragments of A. pleuropneumoniae serotype reference strains.
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Affiliation(s)
- W Oswald
- Tierärztliche Hochschule Hannover, Institut für Mikrobiologie und Tierseuchen, 30173 Hannover, Germany.
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39
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Leiner G, Franz B, Strutzberg K, Gerlach GF. A novel enzyme-linked immunosorbent assay using the recombinant Actinobacillus pleuropneumoniae ApxII antigen for diagnosis of pleuropneumonia in pig herds. CLINICAL AND DIAGNOSTIC LABORATORY IMMUNOLOGY 1999; 6:630-2. [PMID: 10391878 PMCID: PMC95743 DOI: 10.1128/cdli.6.4.630-632.1999] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
For the surveillance of pig herds infected with porcine pleuropneumonia, an enzyme-linked immunosorbent assay (ELISA) using the recombinant Actinobacillus pleuropneumoniae ApxII protein as species- but not serotype-specific antigen was developed. Using this ELISA, 243 of 400 animals from 22 A. pleuropneumoniae-infected herds were classified as seropositive.
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Affiliation(s)
- G Leiner
- Institut für Mikrobiologie und Tierseuchen, Tierärztliche Hochschule Hannover, 30173 Hannover, Germany
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40
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Prideaux CT, Lenghaus C, Krywult J, Hodgson AL. Vaccination and protection of pigs against pleuropneumonia with a vaccine strain of Actinobacillus pleuropneumoniae produced by site-specific mutagenesis of the ApxII operon. Infect Immun 1999; 67:1962-6. [PMID: 10085043 PMCID: PMC96553 DOI: 10.1128/iai.67.4.1962-1966.1999] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The production of toxin (Apx)-neutralizing antibodies during infection plays a major role in the induction of protective immunity to Actinobacillus pleuropneumoniae reinfection. In the present study, the gene encoding the ApxII-activating protein, apxIIC, was insertionally inactivated on the chromosome of a serovar 7 strain, HS93. Expression of the structural toxin, ApxIIA, and of the two genes required for its secretion, apxIB and apxID, still occurs in this strain. The resulting mutant strain, HS93C- Ampr, was found to secrete the unactivated toxin. Pigs vaccinated with live HS93C- Ampr via the intranasal route were protected against a cross-serovar challenge with a virulent serovar 1 strain of A. pleuropneumoniae. This is the first reported vaccine strain of A. pleuropneumoniae which can be delivered live to pigs and offers cross-serovar protection against porcine pleuropneumonia.
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Affiliation(s)
- C T Prideaux
- Animal Health Laboratory, CSIRO Division of Animal Health, Geelong, Victoria 3120, Australia.
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41
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Ito H, Osaki M, Uchida I, Ohya T, Sekizaki T. Demonstration of the third antigenically distinct outer membrane lipoprotein (OmlA) in Actinobacillus pleuropneumoniae serotype 7. FEMS Microbiol Lett 1998; 167:303-8. [PMID: 9809431 DOI: 10.1111/j.1574-6968.1998.tb13243.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The gene encoding an outer membrane lipoprotein (OmlA) of Actinobacillus pleuropneumoniae strain WF83 (serotype 7 reference strain), designated omlA7, was sequenced. The amino acid sequence of OmlA7 showed 64.5 and 71.6% identity to that of OmlA from serotypes 1 (OmlA1) and 5 (OmlA5), respectively. The first 134 amino acids of OmlA7 were identical to those of OmlA5. A Southern blot analysis revealed the presence of a gene highly homologous to the omlA7 in the reference strains of serotypes 3, 4, 6, and 7. A Western blot analysis using a specific antiserum against a recombinant OmlA7 detected expression of the homologous proteins in the serotypes 4, 6, and 7 reference strains and a serotype 3 field strain, but not in a serotype 3 reference strain. The data demonstrate the third antigenically distinct OmlA is expressed in A. pleuropneumoniae.
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Affiliation(s)
- H Ito
- Laboratory of Clinical Bacteriology, Kyushu Research Station, National Institute of Animal Health, Kagoshima, Japan.
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42
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Huang H, Potter AA, Campos M, Leighton FA, Willson PJ, Yates WD. Pathogenesis of porcine Actinobacillus pleuropneumonia: Part I. Effects of surface components of Actinobacillus pleuropneumoniae in vitro and in vivo. CANADIAN JOURNAL OF VETERINARY RESEARCH = REVUE CANADIENNE DE RECHERCHE VETERINAIRE 1998; 62:93-101. [PMID: 9553707 PMCID: PMC1189454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To understand the role of non-secreted components of Actinobacillus pleuropneumoniae in virulence, we investigated in vitro cytotoxicity and in vivo pulmonary changes in pigs due to various A. pleuropneumoniae (serotype 1) fractions. Following 1.5 h incubation, lipopolysaccharide (LPS), 2 crude extracts and bacterial culture supernatant (BCS) at high concentrations were cytotoxic to porcine pulmonary alveolar macrophages (PAM), peripheral blood mononuclear leucocytes, neutrophils and a cultured porcine bone marrow cell line. Heat-killed bacteria were cytotoxic to PAM after 24 h incubation. The 2 crude extracts were prepared by shaking either intact bacteria after removing culture supernatants (crude surface extract, CSE), or whole bacterial culture (crude surface plus culture supernatant extract, CSSE) with glass beads in saline at 60 degrees C. Further experiments showed that proteins from the bacterial membrane were partially involved in cytotoxicities of these 2 extracts. Both BCS and CSSE caused multivocal hemorrhage and neutrophil infiltration when inoculated into porcine lungs, but CSE did not. The lung:whole body weight ratios of the pigs treated with CSSE were significantly higher (P < 0.05) than those of pigs treated with BCS, CSE, or control solution. It is concluded that beside the secreted proteins, bacterial surface components including LPS and non-secreted proteins were cytotoxic in vitro; and secreted and non-secreted components act synergistically to cause lung lesions.
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Affiliation(s)
- H Huang
- Department of Veterinary Pathology, University of Saskatchewan, Saskatoon
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43
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Chiers K, van Overbeke I, De Laender P, Ducatelle R, Carel S, Haesebrouck F. Effects of endobronchial challenge with Actinobacillus pleuropneumoniae serotype 9 of pigs vaccinated with inactivated vaccines containing the Apx toxins. Vet Q 1998; 20:65-9. [PMID: 9563163 DOI: 10.1080/01652176.1998.9694841] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The efficacy of two inactivated vaccines containing the Apx toxins of Actinobacillus pleuropneumoniae (Hemopig, Biokema, Lausanne, Switzerland and Porcilis App, Intervet, Boxmeer, the Netherlands) was determined. Ten pigs were vaccinated twice with Hemopig and eight pigs with Porcilis App. Ten control animals were injected twice with a saline solution. Three weeks after the second vaccination, all pigs were endobronchially inoculated with 10(5) colony-forming units (CFU) of an A. pleuropneumoniae serotype 9 strain. Increased respiratory rate and/or fever were observed in all vaccinated and control pigs after challenge. One pig of the Hemopig group and of the Porcilis App group died, whereas all pigs of the control group survived the challenge. Surviving pigs were killed at 7 days after challenge. The mean percentage of affected lung tissue was 34% in the control group, 16% in the Hemopig group, and 17% in the Porcilis App group. A. pleuropneumoniae was isolated from the lungs of all 10 control animals, from 7 of the 10 animals vaccinated with Hemopig and from 5 of the 8 animals vaccinated with Porcilis App. The mean bacterial titres of the caudal lung lobes were 1.4 x 10(6) CFU/g in the control group, 1.7 x 10(3) CFU/g in the Hemopig group, and 4.8 x 10(3) CFU/g in the Porcilis App group. In both vaccinated groups the mean number of days with dyspnoea, the mean number of days with fever, the mean percentage of affected lung tissue, and the mean bacterial titre in the caudal lung lobes were significantly lower than in the control group. Significant differences between the two vaccinated groups were not observed. It was concluded that both vaccines induced partial protection.
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Affiliation(s)
- K Chiers
- Laboratory of Veterinary Bacteriology and Mycology, Faculty of Veterinary Medicine, University of Gent, Merelbeke, Belgium
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44
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Haesebrouck F, Chiers K, Van Overbeke I, Ducatelle R. Actinobacillus pleuropneumoniae infections in pigs: the role of virulence factors in pathogenesis and protection. Vet Microbiol 1997; 58:239-49. [PMID: 9453134 DOI: 10.1016/s0378-1135(97)00162-4] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This paper discusses the possible role of virulence factors of Actinobacillus pleuropneumoniae in pathogenesis and protection. Special attention is paid to the Apx-exotoxins and to adhesins.
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Affiliation(s)
- F Haesebrouck
- Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, University of Ghent, Merelbeke, Belgium.
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45
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Kamp EM, Stockhofe-Zurwieden N, van Leengoed LA, Smits MA. Endobronchial inoculation with Apx toxins of Actinobacillus pleuropneumoniae leads to pleuropneumonia in pigs. Infect Immun 1997; 65:4350-4. [PMID: 9317048 PMCID: PMC175624 DOI: 10.1128/iai.65.10.4350-4354.1997] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
To establish the role of the Apx toxins in the pathogenesis of porcine pleuropneumonia, specific-pathogen-free pigs were inoculated deeply endobronchially with either culture filtrates of Actinobacillus pleuropneumoniae serotype 8 or 9, culture filtrates depleted of the Apx toxins by affinity chromatography, depleted culture filtrate supplemented with purified recombinant Apx toxins (rApx), or purified rApx toxins alone. Results of these experiments indicate that ApxI, ApxIII, and, to a lesser extent, ApxII are the bacterial factors that trigger the development of clinical symptoms and lung lesions typical for porcine pleuropneumonia.
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Affiliation(s)
- E M Kamp
- Department of Bacteriology, Institute for Animal Science and Health, Lelystad, The Netherlands.
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46
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Haga Y, Ogino S, Ohashi S, Ajito T, Hashimoto K, Sawada T. Protective efficacy of an affinity-purified hemolysin vaccine against experimental swine pleuropneumonia. J Vet Med Sci 1997; 59:115-20. [PMID: 9070983 DOI: 10.1292/jvms.59.115] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Protective efficacy of Actinobacillus pleuropneumoniae extracellular hemolytic toxins, RTX-toxin I (Apx I) and Apx II, was evaluated in pigs. The hemolysins were purified from culture supernatant of A. pleuropneumoniae strain HA-337, serotype 1 by immunoaffinity chromatography using a monoclonal antibody specific for Apx I or Apx II as ligand. Four pigs were vaccinated with the purified hemolysins absorbed on aluminum phosphate gel adjuvant. Four pigs of a control group were given placebo. Hemolysin-neutralizing antibodies were detected only in vaccinated group after booster injection. One of four control pigs died following an aerosol challenge with the homologous strain, and three surviving pigs developed serious clinical signs of pneumonia and had extensive lung lesions. In contrast, there was no mortality in vaccinated group. Only transient hyperthermia was observed in two vaccinated pigs after challenge. A necropsy, two vaccinated pigs had slight localized pulmonary lesions, though the remaining two had no lung lesions at all. These results indicate that the hemolysin vaccine made of Apx I and Apx II has good protective activity against swine pleuropneumonia caused by A. pleuropneumoniae serotype.
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Affiliation(s)
- Y Haga
- Central Research Laboratories, Nippon Zenyaku Kogyo Co., Ltd., Fukushima, Japan
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47
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Rioux S, Dubreuil D, Bégin C, Laferrière C, Martin D, Jacques M. Evaluation of protective efficacy of an Actinobacillus pleuropneumoniae serotype 1 lipopolysaccharide-protein conjugate in mice. Comp Immunol Microbiol Infect Dis 1997; 20:63-74. [PMID: 9023043 DOI: 10.1016/s0147-9571(96)00022-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Actinobacillus pleuropneumoniae is the causative agent of porcine pleuropneumonia. The major adhesin of A. pleuropneumoniae has previously been identified as a lipopolysaccharide (LPS), and more recently, we demonstrated that high molecular mass LPS were involved in A. pleuropneumoniae adherence to porcine respiratory tract cells. We postulated that immunization with a LPS-based vaccine may confer a protective immunity. The high molecular mass O-polysaccharides obtained after acid hydrolysis and chromatographic separation were conjugated to bovine serum albumin (BSA) as a protein carrier. Groups of mice were injected twice with the following antigen preparations: whole-cell preparation, outer membrane preparation, O-polysaccharide-BSA conjugate, hydrolyzed LPS and phenol/water extracted LPS. A combination of different adjuvants was also used during these immunization procedures to induce a stronger immunological response to the polysaccharide antigen. Two weeks after the second injection, the mice were challenged intranasally with either homologous A. pleuropneumoniae serotype 1 strain or a serotype 5 strain. The highest survival rate, up to 80%, compared to the control groups (P < 0.05), was recorded when the mice were injected twice with 15 micrograms of carbohydrates of O-polysaccharide-BSA conjugate mixed with the saponin-derived adjuvant Quil A. Survival rates of between 60 and 70%, twice those observed in the control groups immunized with PBS, were recorded in mice injected with the O-polysaccharide-BSA conjugate mixed with other adjuvant preparations such as alhydrogel, peanut oil and Freund's incomplete adjuvant. However, the protection induced by the conjugate antigen preparation was serotype specific, because mice challenged with a serotype 5 strain were killed. Taken together, these results confirm the important role of A. pleuropneumoniae LPS in pathogenesis.
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Affiliation(s)
- S Rioux
- Département de Pathologie et Microbiologie, Faculté de Médecine Vétérinaire, Université de Montréal, Québec, Canada
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Maier E, Reinhard N, Benz R, Frey J. Channel-forming activity and channel size of the RTX toxins ApxI, ApxII, and ApxIII of Actinobacillus pleuropneumoniae. Infect Immun 1996; 64:4415-23. [PMID: 8890186 PMCID: PMC174392 DOI: 10.1128/iai.64.11.4415-4423.1996] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The determinants of the Actinobacillus pleuropneumoniae RTX toxins ApxI, ApxII, and ApxIII were expressed in an Escherichia coli strain. The toxins were concentrated from the supernatants of cell cultures. The addition of the toxins to the aqueous-phase-bathing lipid bilayer membranes resulted in an increase in the membrane conductance when membranes made of asolectin or phosphatidylethanolamine were used. The toxins were relatively inactive in membranes made of other lipids. The membrane activity (i.e., the number of channels formed at a given Apx concentration) was different for each of the three Apx toxins. That of ApxI, which has the strongest cytotoxic activity, was highest, followed by that of ApxIII and ApxII, which is the least cytotoxic. The conductance increases of ApxIII and ApxII were smaller by factors of 10 and 50, respectively, than that of ApxI under otherwise identical conditions. Single-channel experiments demonstrated that all three Apx toxins formed ion-permeable channels of different conductances. The major open state was approximately the same for the two hemolytic toxins ApxI and ApxII (540 and 620 pS in 0.15 M KCI), whereas the single-channel conductance of the nonhemolytic ApxIII was approximately one-fifth of that of the other two toxins (95 pS). Experiments with different salts suggested that the Apx channels of A. pleuropneumoniae were exclusively cation selective because of negative charges localized at the channel mouth. Analysis of the single-channel data using the Renkin correction factor suggested that the Apx toxins formed aqueous channels with different diameters for the three toxins. Pore-forming properties of the Apx toxins were compared with those of other RTX toxins. All of these toxins have common features and form channels that are transient but have different sizes as judged from the different single-channel conductances.
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Affiliation(s)
- E Maier
- Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Germany
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Haesebrouk F, Van de Kerkhof A, Dom P, Chiers K, Ducatelle R. Cross-protection between Actinobacillus pleuropneumoniae biotypes-serotypes in pigs. Vet Microbiol 1996; 52:277-84. [PMID: 8972053 DOI: 10.1016/s0378-1135(96)00075-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Four groups of hysterectomy-derived and colostrum-deprived pigs were intranasally inoculated with an Actinobacillus pleuropneumoniae biotype 1-serotype 2 strain (producing RTX toxins ApxII and ApxIII. 6 pigs), an A. pleuropneumoniae biotype 1-serotype 10 strain (producing ApxI. 5 pigs), an A. pleuropneumoniae biotype 2-serotype 2 strain (producing ApxII, 5 pigs) or saline (controls, 7 pigs). All pigs were exposed to A. pleuropneumoniae biotype 1-serotype 2 endobronchial challenge. After challenge, severe clinical signs were observed in all control pigs, one pig immunized with the A. pleuropneumoniae biotype 1-serotype 10 strain and two pigs immunized with the A. pleuropneumoniae biotype 2-serotype 2 strain. These pigs died within 36 h after challenge and 20 to 50% of the lungs were macroscopically affected. In the other pigs, clinical signs were mild or absent and no or only small, focal lung lesions were observed when euthanized at 48 h after challenge. At the time challenge neutralizing antibodies against ApxI only. ApxII only and both ApxII and III were present in sera of pigs immunized with the A. pleuropneumoniae biotype 1-serotype 10 strain, the A. pleuropneumoniae biotype 2-serotype 2 strain and the A. pleuropneumoniae biotype 1-serotype 2 strain, respectively. These results indicate that immune mechanisms other than Apx neutralizing antibodies were involved in partial cross-protection of pigs immunized against A. pleuropneumoniae biotype 1-serotype 10 and challenged with the A. pleuropneumoniae biotype 1-serotype 2.
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Affiliation(s)
- F Haesebrouk
- Laboratory of Veterinary Bacteriology and Mycology, Faculty of Veterinary Medicine, University of Gent, Merelbeke, Belgium.
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Tarigan S, Slocombe RF, Browning GF, Blackall PJ. Characterisation of haemolytic RTX toxins produced by Australian isolates of Actinobacillus pleuropneumoniae. Aust Vet J 1996; 73:164-9. [PMID: 8660237 DOI: 10.1111/j.1751-0813.1996.tb10019.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The haemolytic RTX toxins of 27 isolates of Actinobacillus pleuropneumoniae, representing all serovars that have been isolated in Australia, were characterised. The quantity of protein secreted by these isolates into the media was not significantly different between serovars, but haemolytic activity was detected only in the unconcentrated supernatants from cultures of serovar 1 and 5 isolates. Haemolytic activity in supernatants of serovar 2, 3 and 7 isolates was detected only after the supernatants were concentrated. On Southern hybridisation blots, genomic DNA of serovar 1 and 5 isolates contained regions that were similar to the cloned structural genes for ApxI (apxIA) and for ApxII (apxIIA). In contrast, genomic DNA of serovar 2, 3 and 7 isolates only contained regions similar to, if not identical with, the cloned apxIIA gene. The haemolytic activity of the culture supernatant depends on the type or composition of media and adaptability of the bacteria to in-vitro cultivation. Low passage cultures of A pleuropneumoniae, which were characterised by waxy colonies, produced significantly weaker haemolytic activity than A pleuropneumoniae after several passages in vitro.
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Affiliation(s)
- S Tarigan
- School of Veterinary Science, University of Melbourne, Parkville, Victoria
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