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Montero DA, Vidal RM, Velasco J, George S, Lucero Y, Gómez LA, Carreño LJ, García-Betancourt R, O’Ryan M. Vibrio cholerae, classification, pathogenesis, immune response, and trends in vaccine development. Front Med (Lausanne) 2023; 10:1155751. [PMID: 37215733 PMCID: PMC10196187 DOI: 10.3389/fmed.2023.1155751] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 04/14/2023] [Indexed: 05/24/2023] Open
Abstract
Vibrio cholerae is the causative agent of cholera, a highly contagious diarrheal disease affecting millions worldwide each year. Cholera is a major public health problem, primarily in countries with poor sanitary conditions and regions affected by natural disasters, where access to safe drinking water is limited. In this narrative review, we aim to summarize the current understanding of the evolution of virulence and pathogenesis of V. cholerae as well as provide an overview of the immune response against this pathogen. We highlight that V. cholerae has a remarkable ability to adapt and evolve, which is a global concern because it increases the risk of cholera outbreaks and the spread of the disease to new regions, making its control even more challenging. Furthermore, we show that this pathogen expresses several virulence factors enabling it to efficiently colonize the human intestine and cause cholera. A cumulative body of work also shows that V. cholerae infection triggers an inflammatory response that influences the development of immune memory against cholera. Lastly, we reviewed the status of licensed cholera vaccines, those undergoing clinical evaluation, and recent progress in developing next-generation vaccines. This review offers a comprehensive view of V. cholerae and identifies knowledge gaps that must be addressed to develop more effective cholera vaccines.
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Affiliation(s)
- David A. Montero
- Departamento de Microbiología, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Roberto M. Vidal
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Instituto Milenio de Inmunología e Inmunoterapia, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Juliana Velasco
- Unidad de Paciente Crítico, Clínica Hospital del Profesor, Santiago, Chile
- Programa de Formación de Especialista en Medicina de Urgencia, Universidad Andrés Bello, Santiago, Chile
| | - Sergio George
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Yalda Lucero
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Departamento de Pediatría y Cirugía Infantil, Hospital Dr. Roberto del Rio, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Leonardo A. Gómez
- Departamento de Microbiología, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Leandro J. Carreño
- Instituto Milenio de Inmunología e Inmunoterapia, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Programa de Inmunología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Richard García-Betancourt
- Programa de Inmunología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Miguel O’Ryan
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
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2
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Takahashi E, Ochi S, Mizuno T, Morita D, Morita M, Ohnishi M, Koley H, Dutta M, Chowdhury G, Mukhopadhyay AK, Dutta S, Miyoshi SI, Okamoto K. Virulence of Cholera Toxin Gene-Positive Vibrio cholerae Non-O1/non-O139 Strains Isolated From Environmental Water in Kolkata, India. Front Microbiol 2021; 12:726273. [PMID: 34489915 PMCID: PMC8417801 DOI: 10.3389/fmicb.2021.726273] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 08/02/2021] [Indexed: 11/13/2022] Open
Abstract
Cholera toxin (CT)-producing Vibrio cholerae O1 and O139 cause acute diarrheal disease and are proven etiological agents of cholera epidemics and pandemics. On the other hand, V. cholerae non-O1/non-O139 are designated as non-agglutinable (NAG) vibrios and are not associated with epidemic cholera. The majority of NAG vibrios do not possess the gene for CT (ctx). In this study, we isolated three NAG strains (strains No. 1, 2, and 3) with ctx from pond water in Kolkata, India, and examined their pathogenic properties. The enterotoxicity of the three NAG strains in vivo was examined using the rabbit ileal intestinal loop test. Strain No. 1 induced the accumulation of fluid in the loop, and the volume of fluid was reduced by simultaneous administration of anti-CT antiserum into the loop. The volume of fluid in the loop caused by strains No. 2 and 3 was small and undetectable, respectively. Then, we cultured these three strains in liquid medium in vitro at two temperatures, 25°C and 37°C, and examined the amount of CT accumulated in the culture supernatant. CT was accumulated in the culture supernatant of strain No.1 when the strain was cultured at 25°C, but that was low when cultured at 37°C. The CT amount accumulated in the culture supernatants of the No. 2 and No. 3 strains was extremely low at both temperature under culture conditions examined. In order to clarify the virulence properties of these strains, genome sequences of the three strains were analyzed. The analysis showed that there was no noticeable difference among three isolates both in the genes for virulence factors and regulatory genes of ctx. However, vibrio seventh pandemic island-II (VSP-II) was retained in strain No. 1, but not in strains No. 2 or 3. Furthermore, it was revealed that the genotype of the B subunit of CT in strain No. 1 was type 1 and those of strains No. 2 and 3 were type 8. Histopathological examination showed the disappearance of villi in intestinal tissue exposed to strain No. 1. In addition, fluid accumulated in the loop due to the action of strain No. 1 had hemolytic activity. This indicated that strain No. 1 may possesses virulence factors to induce severe syndrome when the strain infects humans, and that some strains of NAG vibrio inhabiting pond water in Kolkata have already acquired virulence, which can cause illness in humans. There is a possibility that these virulent NAG vibrios, which have acquired genes encoding factors involved in virulence of V. cholerae O1, may emerge in various parts of the world and cause epidemics in the future.
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Affiliation(s)
- Eizo Takahashi
- Collaborative Research Center of Okayama University for Infectious Diseases in India, NICED-JICA Building, Kolkata, India.,Department of Health Pharmacy, Yokohama University of Pharmacy, Yokohama, Japan
| | - Sadayuki Ochi
- Department of Health Pharmacy, Yokohama University of Pharmacy, Yokohama, Japan
| | - Tamaki Mizuno
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences of Okayama University, Okayama, Japan
| | - Daichi Morita
- Collaborative Research Center of Okayama University for Infectious Diseases in India, NICED-JICA Building, Kolkata, India
| | - Masatomo Morita
- Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan
| | - Makoto Ohnishi
- Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan
| | - Hemanta Koley
- National Institute of Cholera and Enteric Diseases, NICED-JICA Building, Kolkata, India
| | - Moumita Dutta
- National Institute of Cholera and Enteric Diseases, NICED-JICA Building, Kolkata, India
| | - Goutam Chowdhury
- National Institute of Cholera and Enteric Diseases, NICED-JICA Building, Kolkata, India
| | - Asish K Mukhopadhyay
- National Institute of Cholera and Enteric Diseases, NICED-JICA Building, Kolkata, India
| | - Shanta Dutta
- National Institute of Cholera and Enteric Diseases, NICED-JICA Building, Kolkata, India
| | - Shin-Ichi Miyoshi
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences of Okayama University, Okayama, Japan
| | - Keinosuke Okamoto
- Collaborative Research Center of Okayama University for Infectious Diseases in India, NICED-JICA Building, Kolkata, India
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3
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González-Larraza PG, López-Goerne TM, Padilla-Godínez FJ, González-López MA, Hamdan-Partida A, Gómez E. IC 50 Evaluation of Platinum Nanocatalysts for Cancer Treatment in Fibroblast, HeLa, and DU-145 Cell Lines. ACS OMEGA 2020; 5:25381-25389. [PMID: 33043218 PMCID: PMC7542800 DOI: 10.1021/acsomega.0c03759] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 09/09/2020] [Indexed: 05/27/2023]
Abstract
Cancer is a major public health problem being one of the main causes of morbidity and mortality today. Recent advances in catalytic nanomedicine have offered new cancer therapies based on the administration of nanoparticles (NPs) of platinum (Pt) dispersed in catalytic mesoporous nanomaterials (titania, TiO2) with highly selective cytotoxic properties and no adverse effects. A half maximal inhibitory concentration (IC50) study was carried out in cancerous cell lines (HeLa, DU-145, and fibroblasts) to evaluate the cytotoxic effect of different nanomaterials [Pt/TiO2, TiO2, and Pt(acac)2] synthesized by the sol-gel method at concentrations 0-1000 μg/mL. The assays showed that IC50 values for Pt in functionalized TiO2 (NPt) in HeLa (53.74 ± 2.95 μg/mL) and DU-145 (75.07 ± 5.48 μg/mL) were lower than those of pure TiO2 (74.29 ± 8.95 and 82.02 ± 6.03 μg/mL, respectively). Pt(acac)2 exhibited no cytotoxicity. Normal cells (fibroblasts) treated with NPt exhibited no significant growth inhibition, suggesting the high selectivity of the compound for cancerous cells only. TiO2 and NPt were identified as antineoplastic compounds in vitro. Pt(acac)2 is not recommendable because of the low cytotoxicity observed.
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Affiliation(s)
- Pamela G. González-Larraza
- Department of Health Care, Autonomous Metropolitan
University Xochimilco, Coyoacan, Mexico City 04960, Mexico
| | - Tessy M. López-Goerne
- Department of Health Care, Autonomous Metropolitan
University Xochimilco, Coyoacan, Mexico City 04960, Mexico
| | - Francisco J. Padilla-Godínez
- Department of Health Care, Autonomous Metropolitan
University Xochimilco, Coyoacan, Mexico City 04960, Mexico
- Department of Mathematics and Physics, Western Institute of Technology and Higher Education, San Pedro Tlaquepaque, Jalisco 45604, Mexico
| | - Marco A. González-López
- Department of Health Care, Autonomous Metropolitan
University Xochimilco, Coyoacan, Mexico City 04960, Mexico
| | - Aida Hamdan-Partida
- Department of Health Care, Autonomous Metropolitan
University Xochimilco, Coyoacan, Mexico City 04960, Mexico
| | - Esteban Gómez
- AG Nanooptik, Humboldt-Universtät zu Berlin, Berlin 10117, Germany
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4
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Davoodi S, Foley E. Host-Microbe-Pathogen Interactions: A Review of Vibrio cholerae Pathogenesis in Drosophila. Front Immunol 2020; 10:3128. [PMID: 32038640 PMCID: PMC6993214 DOI: 10.3389/fimmu.2019.03128] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 12/23/2019] [Indexed: 12/14/2022] Open
Abstract
Most animals maintain mutually beneficial symbiotic relationships with their intestinal microbiota. Resident microbes in the gastrointestinal tract breakdown indigestible food, provide essential nutrients, and, act as a barrier against invading microbes, such as the enteric pathogen Vibrio cholerae. Over the last decades, our knowledge of V. cholerae pathogenesis, colonization, and transmission has increased tremendously. A number of animal models have been used to study how V. cholerae interacts with host-derived resources to support gastrointestinal colonization. Here, we review studies on host-microbe interactions and how infection with V. cholerae disrupts these interactions, with a focus on contributions from the Drosophila melanogaster model. We will discuss studies that highlight the connections between symbiont, host, and V. cholerae metabolism; crosstalk between V. cholerae and host microbes; and the impact of the host immune system on the lethality of V. cholerae infection. These studies suggest that V. cholerae modulates host immune-metabolic responses in the fly and improves Vibrio fitness through competition with intestinal microbes.
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Affiliation(s)
| | - Edan Foley
- Department of Medical Microbiology and Immunology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
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5
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Gao H, Xu J, Lu X, Li J, Lou J, Zhao H, Diao B, Shi Q, Zhang Y, Kan B. Expression of Hemolysin Is Regulated Under the Collective Actions of HapR, Fur, and HlyU in Vibrio cholerae El Tor Serogroup O1. Front Microbiol 2018; 9:1310. [PMID: 29971055 PMCID: PMC6018088 DOI: 10.3389/fmicb.2018.01310] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 05/29/2018] [Indexed: 12/19/2022] Open
Abstract
The biotype El Tor of serogroup O1 and most of the non-O1/non-O139 strains of Vibrio cholerae can produce an extracellular pore-forming toxin known as cholera hemolysin (HlyA). Expression of HlyA has been previously reported to be regulated by the quorum sensing (QS) and the regulatory proteins HlyU and Fur, but lacks the direct evidence for their binding to the promoter of hlyA. In the present work, we showed that the QS regulator HapR, along with Fur and HlyU, regulates the transcription of hlyA in V. cholerae El Tor biotype. At the late mid-logarithmic growth phase, HapR binds to the three promoters of fur, hlyU, and hlyA to repress their transcription. At the early mid-logarithmic growth phase, Fur binds to the promoters of hlyU and hlyA to repress their transcription; meanwhile, HlyU binds to the promoter of hlyA to activate its transcription, but it manifests direct inhibition of its own gene. The highest transcriptional level of hlyA occurs at an OD600 value of around 0.6–0.7, which may be due to the subtle regulation of HapR, Fur, and HlyU. The complex regulation of HapR, Fur, and HlyU on hlyA would be beneficial to the invasion and pathogenesis of V. cholerae during the different infection stages.
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Affiliation(s)
- He Gao
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Jialiang Xu
- Key Laboratory of Cleaner Production and Integrated Resource Utilization of China National Light Industry, School of Food and Chemical Engineering, Beijing Technology and Business University, Beijing, China
| | - Xin Lu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Jie Li
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Jing Lou
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Hongqun Zhao
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Baowei Diao
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Qiannan Shi
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Yiquan Zhang
- School of Medicine, Jiangsu University, Zhenjiang, China
| | - Biao Kan
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
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6
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Castillo D, Pérez-Reytor D, Plaza N, Ramírez-Araya S, Blondel CJ, Corsini G, Bastías R, Loyola DE, Jaña V, Pavez L, García K. Exploring the Genomic Traits of Non-toxigenic Vibrio parahaemolyticus Strains Isolated in Southern Chile. Front Microbiol 2018; 9:161. [PMID: 29472910 PMCID: PMC5809470 DOI: 10.3389/fmicb.2018.00161] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 01/24/2018] [Indexed: 01/30/2023] Open
Abstract
Vibrio parahaemolyticus is the leading cause of seafood-borne gastroenteritis worldwide. As reported in other countries, after the rise and fall of the pandemic strain in Chile, other post-pandemic strains have been associated with clinical cases, including strains lacking the major toxins TDH and TRH. Since the presence or absence of tdh and trh genes has been used for diagnostic purposes and as a proxy of the virulence of V. parahaemolyticus isolates, the understanding of virulence in V. parahaemolyticus strains lacking toxins is essential to detect these strains present in water and marine products to avoid possible food-borne infection. In this study, we characterized the genome of four environmental and two clinical non-toxigenic strains (tdh-, trh-, and T3SS2-). Using whole-genome sequencing, phylogenetic, and comparative genome analysis, we identified the core and pan-genome of V. parahaemolyticus of strains of southern Chile. The phylogenetic tree based on the core genome showed low genetic diversity but the analysis of the pan-genome revealed that all strains harbored genomic islands carrying diverse virulence and fitness factors or prophage-like elements that encode toxins like Zot and RTX. Interestingly, the three strains carrying Zot-like toxin have a different sequence, although the alignment showed some conserved areas with the zot sequence found in V. cholerae. In addition, we identified an unexpected diversity in the genetic architecture of the T3SS1 gene cluster and the presence of the T3SS2 gene cluster in a non-pandemic environmental strain. Our study sheds light on the diversity of V. parahaemolyticus strains from the southern Pacific which increases our current knowledge regarding the global diversity of this organism.
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Affiliation(s)
- Daniel Castillo
- Marine Biological Section, University of Copenhagen, Helsingør, Denmark
| | - Diliana Pérez-Reytor
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Nicolás Plaza
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Sebastián Ramírez-Araya
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile.,Departamento de Ciencias Básicas, Facultad de Ciencias, Universidad Santo Tomás, Santiago, Chile
| | - Carlos J Blondel
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Gino Corsini
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Roberto Bastías
- Laboratory of Microbiology, Institute of Biology, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | | | - Víctor Jaña
- Facultad de Medicina Veterinaria y Agronomía, Universidad de Las Américas, Santiago, Chile
| | - Leonardo Pavez
- Facultad de Medicina Veterinaria y Agronomía, Universidad de Las Américas, Santiago, Chile.,Departamento de Ciencias Químicas y Biológicas, Universidad Bernardo O'Higgins, Santiago, Chile
| | - Katherine García
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
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7
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Shubin AV, Demidyuk IV, Komissarov AA, Rafieva LM, Kostrov SV. Cytoplasmic vacuolization in cell death and survival. Oncotarget 2018; 7:55863-55889. [PMID: 27331412 PMCID: PMC5342458 DOI: 10.18632/oncotarget.10150] [Citation(s) in RCA: 204] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Accepted: 06/06/2016] [Indexed: 12/15/2022] Open
Abstract
Cytoplasmic vacuolization (also called cytoplasmic vacuolation) is a well-known morphological phenomenon observed in mammalian cells after exposure to bacterial or viral pathogens as well as to various natural and artificial low-molecular-weight compounds. Vacuolization often accompanies cell death; however, its role in cell death processes remains unclear. This can be attributed to studying vacuolization at the level of morphology for many years. At the same time, new data on the molecular mechanisms of the vacuole formation and structure have become available. In addition, numerous examples of the association between vacuolization and previously unknown cell death types have been reported. Here, we review these data to make a deeper insight into the role of cytoplasmic vacuolization in cell death and survival.
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Affiliation(s)
- Andrey V Shubin
- Laboratory of Protein Engineering, Institute of Molecular Genetics, Moscow, Russia.,Laboratory of Chemical Carcinogenesis, N.N. Blokhin Russian Cancer Research Center, Moscow, Russia.,Laboratory of Biologically Active Nanostructures, N.F. Gamaleya Institute of Epidemiology and Microbiology, Moscow, Russia
| | - Ilya V Demidyuk
- Laboratory of Protein Engineering, Institute of Molecular Genetics, Moscow, Russia
| | - Alexey A Komissarov
- Laboratory of Protein Engineering, Institute of Molecular Genetics, Moscow, Russia
| | - Lola M Rafieva
- Laboratory of Protein Engineering, Institute of Molecular Genetics, Moscow, Russia
| | - Sergey V Kostrov
- Laboratory of Protein Engineering, Institute of Molecular Genetics, Moscow, Russia
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8
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Goleij Z, Mahmoodzadeh Hosseini H, Amin M, Halabian R, Imani Fooladi AA. Prokaryotic toxins provoke different types of cell deaths in the eukaryotic cells. TOXIN REV 2017. [DOI: 10.1080/15569543.2017.1294180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Zoleikha Goleij
- Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran and
| | | | - Mohsen Amin
- Department of Drug and Food Control, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
| | - Raheleh Halabian
- Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran and
| | - Abbas Ali Imani Fooladi
- Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran and
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9
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Ludovico MS, Martins LM, Bianco JER, Andrade CGTDJ, Falcon R, Joazeiro PP, Gatti MSV, Yano T. Plesiomonas shigelloides exports a lethal cytotoxic-enterotoxin (LCE) by membrane vesicles. Braz J Infect Dis 2016; 20:546-555. [PMID: 27770615 PMCID: PMC9427589 DOI: 10.1016/j.bjid.2016.08.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 08/12/2016] [Accepted: 08/20/2016] [Indexed: 11/28/2022] Open
Abstract
Plesiomonas shigelloides isolated from water in Brazil was previously described as a hemorrhagic heat-labile cytotoxic-enterotoxin producer. We purified this toxin from culture supernatants using ion metallic affinity chromatography (IMAC) followed by molecular exclusion chromatography. The pure toxin presented molecular mass of 50 kDa and isoelectric point (pI) around 6.9 by 2D electrophoresis. When injected intravenously, the purified cytotoxic-enterotoxin induced also severe spasms followed by sudden death of mice. Hence, we entitled it as lethal cytotoxic-enterotoxin (LCE). The presence of membrane vesicles (MVs) on cell surfaces of P. shigelloides was observed by scan electron microscopy (SEM). From these MVs the LCE toxin was extracted and confirmed by biological and serological assays. These data suggest that P. shigelloides also exports this cytotoxic-enterotoxin by membrane vesicles, a different mechanism of delivering extra cellular virulence factors, so far not described in this bacterium.
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Affiliation(s)
- Marilucia Santos Ludovico
- Universidade Estadual de Campinas (UNICAMP), Departamento de Genética, Evolução e Bioagentes, Campinas, SP, Brazil
| | | | - Juares Ednaldo Romero Bianco
- Universidade Estadual de Campinas (UNICAMP), Departamento de Bioquímica e Biologia Tecidual, Campinas, SP, Brazil
| | | | - Rosabel Falcon
- Instituto de Medicina Tropical "Pedro Kourí" (IPK), Departamento de Microbiología, La Habana, Cuba
| | - Paulo Pinto Joazeiro
- Universidade Estadual de Campinas (UNICAMP), Departamento de Bioquímica e Biologia Tecidual, Campinas, SP, Brazil
| | - Maria Silvia Viccari Gatti
- Universidade Estadual de Campinas (UNICAMP), Departamento de Genética, Evolução e Bioagentes, Campinas, SP, Brazil
| | - Tomomasa Yano
- Universidade Estadual de Campinas (UNICAMP), Departamento de Genética, Evolução e Bioagentes, Campinas, SP, Brazil.
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10
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Characterization of Vibrio cholerae isolates from 1976 to 2013 in Shandong Province, China. Braz J Microbiol 2016; 48:173-179. [PMID: 27780663 PMCID: PMC5221356 DOI: 10.1016/j.bjm.2016.09.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 06/09/2016] [Indexed: 11/22/2022] Open
Abstract
Cholera continues to be a serious public health issue in developing countries. We analyzed the epidemiological data of cholera from 1976 to 2013 in Shandong Province, an eastern coastal area of China. A total of 250 Vibrio cholerae isolates were selected for PCR analysis of virulence genes and pulsed-field gel electrophoresis (PFGE). The analysis of the virulence genes showed that the positive rates for tcpA and tcpI were the highest among strains from the southwest region, which had the highest incidence rate of cholera. Low positive rates for tcpA, tcpI and ctxAB among isolates from after 2000 may be an influencing factor contributing to the contemporary decline in cholera incidence rates. Spatiotemporal serotype shifts (Ogawa, Inaba, Ogawa, Inaba and O139) generally correlated with the variations in the PFGE patterns (PIV, PIIIc, PIa, PIIIb, PIIIa, PIb, and PII). O1 strains from different years or regions also had similar PFGE patterns, while O139 strains exclusively formed one cluster and differed from all other O1 strains. These data indicate that V. cholerae isolates in Shandong Province have continually undergone spatiotemporal changes. The serotype switching between Ogawa and Inaba originated from indigenous strains, while the emergence of serogroup O139 appeared to be unrelated to endemic V. cholerae O1 strains.
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11
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Miyashita SI, Sagane Y, Suzuki T, Matsumoto T, Niwa K, Watanabe T. "Non-Toxic" Proteins of the Botulinum Toxin Complex Exert In-vivo Toxicity. Sci Rep 2016; 6:31043. [PMID: 27507612 PMCID: PMC4978960 DOI: 10.1038/srep31043] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 07/12/2016] [Indexed: 01/26/2023] Open
Abstract
The botulinum neurotoxin (BoNT) causes muscle paralysis and is the most potent toxin in nature. BoNT is associated with a complex of auxiliary “Non-Toxic” proteins, which constitute a large-sized toxin complex (L-TC). However, here we report that the “Non-Toxic” complex of serotype D botulinum L-TC, when administered to rats, exerts in-vivo toxicity on small-intestinal villi. Moreover, Serotype C and D of the “Non-Toxic” complex, but not BoNT, induced vacuole-formation in a rat intestinal epithelial cell line (IEC-6), resulting in cell death. Our results suggest that the vacuole was formed in a manner distinct from the mechanism by which Helicobacter pylori vacuolating toxin (VacA) and Vibrio cholerae haemolysin induce vacuolation. We therefore hypothesise that the serotype C and D botulinum toxin complex is a functional hybrid of the neurotoxin and vacuolating toxin (VT) which arose from horizontal gene transfer from an ancestral BoNT-producing bacterium to a hypothetical VT-producing bacterium.
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Affiliation(s)
- Shin-Ichiro Miyashita
- Department of Food and Cosmetic Science, Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan
| | - Yoshimasa Sagane
- Department of Food and Cosmetic Science, Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan
| | - Tomonori Suzuki
- Department of Nutritional Science and Food Safety, Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan
| | | | - Koichi Niwa
- Department of Food and Cosmetic Science, Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan
| | - Toshihiro Watanabe
- Department of Food and Cosmetic Science, Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan
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Khilwani B, Chattopadhyay K. Signaling beyond Punching Holes: Modulation of Cellular Responses by Vibrio cholerae Cytolysin. Toxins (Basel) 2015; 7:3344-58. [PMID: 26308054 PMCID: PMC4549754 DOI: 10.3390/toxins7083344] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 08/12/2015] [Accepted: 08/14/2015] [Indexed: 01/20/2023] Open
Abstract
Pore-forming toxins (PFTs) are a distinct class of membrane-damaging cytolytic proteins that contribute significantly towards the virulence processes employed by various pathogenic bacteria. Vibrio cholerae cytolysin (VCC) is a prominent member of the beta-barrel PFT (beta-PFT) family. It is secreted by most of the pathogenic strains of the intestinal pathogen V. cholerae. Owing to its potent membrane-damaging cell-killing activity, VCC is believed to play critical roles in V. cholerae pathogenesis, particularly in those strains that lack the cholera toxin. Large numbers of studies have explored the mechanistic basis of the cell-killing activity of VCC. Consistent with the beta-PFT mode of action, VCC has been shown to act on the target cells by forming transmembrane oligomeric beta-barrel pores, thereby leading to permeabilization of the target cell membranes. Apart from the pore-formation-induced direct cell-killing action, VCC exhibits the potential to initiate a plethora of signal transduction pathways that may lead to apoptosis, or may act to enhance the cell survival/activation responses, depending on the type of target cells. In this review, we will present a concise view of our current understanding regarding the multiple aspects of these cellular responses, and their underlying signaling mechanisms, evoked by VCC.
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Affiliation(s)
- Barkha Khilwani
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences Indian Institute of Science Education and Research Mohali Sector 81, S. A. S. Nagar, Manauli PO 140306, Punjab, India.
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences Indian Institute of Science Education and Research Mohali Sector 81, S. A. S. Nagar, Manauli PO 140306, Punjab, India.
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Rai AK, Chattopadhyay K. Revisiting the membrane interaction mechanism of a membrane-damaging β-barrel pore-forming toxinVibrio choleraecytolysin. Mol Microbiol 2015; 97:1051-62. [DOI: 10.1111/mmi.13084] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/05/2015] [Indexed: 01/14/2023]
Affiliation(s)
- Anand Kumar Rai
- Centre for Protein Science, Design and Engineering; Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Sector 81, SAS Nagar, Manauli Mohali Punjab 140306 India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering; Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Sector 81, SAS Nagar, Manauli Mohali Punjab 140306 India
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Vibrio cholerae Cytolysin: Structure–Function Mechanism of an Atypical β-Barrel Pore-Forming Toxin. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 842:109-25. [DOI: 10.1007/978-3-319-11280-0_7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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15
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Espinoza-Mellado MDR, López-Villegas EO, Arteaga-Garibay RI, Giono-Cerezo S. Cell vacuolation induced by Haemophilus influenzae supernatants in HEp-2 cells. Mem Inst Oswaldo Cruz 2014; 108:1074-7. [PMID: 24402145 PMCID: PMC4005551 DOI: 10.1590/0074-0276130716] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Accepted: 10/02/2013] [Indexed: 11/22/2022] Open
Abstract
Haemophilus influenzae belongs to respiratory tract microbiota. We
observed vacuoles formation in previous studies with H. influenzae
culture supernatants, so in this work we characterised that cytotoxic effect. We
observed an abundant production of acidic cytoplasmic vacuoles due to the presence of
a “vacuolating factor” in H. influenzae supernatants which was characterised as
thermolabile. Greatest vacuolating activity was observed when utilizing the fraction
> 50 kDa. The presence of a large number of vacuoles in HEp-2 cells was verified
by transmission electron microscopy and some vacuoles were identified with a double
membrane and/or being surrounded by ribosomes. These results suggest similar
behaviour to that of vacuolating effects described by autotransporter proteins an
undescribed cytotoxic effect induced by H. influenzae .
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Ikigai H, Otsuru H, Yamamoto K, Shimamura T. Structural Requirements of Cholesterol for Binding toVibrio choleraeHemolysin. Microbiol Immunol 2013; 50:751-7. [PMID: 17053310 DOI: 10.1111/j.1348-0421.2006.tb03848.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cholesterol is necessary for the conversion of Vibrio cholerae hemolysin (VCH) monomers into oligomers in liposome membranes. Using different sterols, we determined the stereochemical structures of the VCH-binding active groups present in cholesterol. The VCH monomers are bound to cholesterol, diosgenin, campesterol, and ergosterol, which have a hydroxyl group at position C-3 (3betaOH) in the A ring and a C-C double bond between positions C-5 and C-6 (C-C Delta(5)) in the B ring. They are not bound to epicholesterol and dihydrocholesterol, which form a covalent link with a 3alphaOH group and a C-C single bond between positions C-5 and C-6, respectively. This result suggests that the 3betaOH group and the C-CDelta(5) bond in cholesterol are required for VCH monomer binding. We further examined VCH oligomer binding to cholesterol. However, this oligomer did not bind to cholesterol, suggesting that the disappearance of the cholesterol-binding potential of the VCH oligomer might be a result of the conformational change caused by the conversion of the monomer into the oligomer. VCH oligomer formation was observed in liposomes containing sterols with the 3betaOH group and the C-C Delta(5) bond, and it correlated with the binding affinity of the monomer to each sterol. Therefore, it seems likely that monomer binding to membrane sterol leads to the assembly of the monomer. However, since oligomer formation was induced by liposomes containing either epicholesterol or dihydrocholesterol, the 3betaOH group and the C-C Delta(5) bond were not essential for conversion into the oligomer.
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Affiliation(s)
- Hajime Ikigai
- Department of Chemistry and Biochemistry, Suzuka National College of Technology, Suzuka, Mie 510-0294, Japan.
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The products of the reaction between 6-amine-1,3-dimethyl uracil and bis-chalcones induce cytotoxicity with massive vacuolation in HeLa cervical cancer cell line. Eur J Med Chem 2013; 60:350-9. [DOI: 10.1016/j.ejmech.2012.12.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 12/06/2012] [Accepted: 12/10/2012] [Indexed: 11/19/2022]
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Sahu SN, Lewis J, Patel I, Bozdag S, Lee JH, LeClerc JE, Cinar HN. Genomic analysis of immune response against Vibrio cholerae hemolysin in Caenorhabditis elegans. PLoS One 2012; 7:e38200. [PMID: 22675448 PMCID: PMC3364981 DOI: 10.1371/journal.pone.0038200] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 05/04/2012] [Indexed: 11/18/2022] Open
Abstract
Vibrio cholerae cytolysin (VCC) is among the accessory V. cholerae virulence factors that may contribute to disease pathogenesis in humans. VCC, encoded by hlyA gene, belongs to the most common class of bacterial toxins, known as pore-forming toxins (PFTs). V. cholerae infects and kills Caenorhabditis elegans via cholerae toxin independent manner. VCC is required for the lethality, growth retardation and intestinal cell vacuolation during the infection. However, little is known about the host gene expression responses against VCC. To address this question we performed a microarray study in C. elegans exposed to V. cholerae strains with intact and deleted hlyA genes. Many of the VCC regulated genes identified, including C-type lectins, Prion-like (glutamine [Q]/asparagine [N]-rich)-domain containing genes, genes regulated by insulin/IGF-1-mediated signaling (IIS) pathway, were previously reported as mediators of innate immune response against other bacteria in C. elegans. Protective function of the subset of the genes up-regulated by VCC was confirmed using RNAi. By means of a machine learning algorithm called FastMEDUSA, we identified several putative VCC induced immune regulatory transcriptional factors and transcription factor binding motifs. Our results suggest that VCC is a major virulence factor, which induces a wide variety of immune response- related genes during V. cholerae infection in C. elegans.
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Affiliation(s)
- Surasri N. Sahu
- Division of Virulence Assessment, Food and Drug Administration, Laurel, Maryland, United States of America
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee, United States of America
| | - Jada Lewis
- Division of Molecular Biology, Food and Drug Administration, Laurel, Maryland, United States of America
| | - Isha Patel
- Division of Molecular Biology, Food and Drug Administration, Laurel, Maryland, United States of America
| | - Serdar Bozdag
- Neuro-Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jeong H. Lee
- Division of Virulence Assessment, Food and Drug Administration, Laurel, Maryland, United States of America
- Kyungpook National University (KNU), Daegu, South Korea
| | - Joseph E. LeClerc
- Division of Molecular Biology, Food and Drug Administration, Laurel, Maryland, United States of America
| | - Hediye Nese Cinar
- Division of Virulence Assessment, Food and Drug Administration, Laurel, Maryland, United States of America
- * E-mail:
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Suppressed induction of proinflammatory cytokines by a unique metabolite produced by Vibrio cholerae O1 El Tor biotype in cultured host cells. Infect Immun 2011; 79:3149-58. [PMID: 21576340 DOI: 10.1128/iai.01237-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Vibrio cholerae O1 has two biotypes, El Tor and Classical, and the latter is now presumed to be extinct in nature. Under carbohydrate-rich growth conditions, El Tor biotype strains produce the neutral fermentation end product 2,3-butanediol (2,3-BD), which prevents accumulation of organic acids from mixed acid fermentation and thus avoids a lethal decrease in the medium pH, while the Classical biotype strains fail to do the same. In this study, we investigated the inhibitory effect of 2,3-BD on the production of two proinflammatory biomarkers, intreleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-α), in human intestinal epithelial HT29 and alveolar epithelial A549 cells. Cell-free culture supernatants of El Tor strain N16961 grown in LB supplemented with 1% glucose induced a negligible amount of IL-8 or TNF-α, while the Classical O395 strain induced much higher levels of these proinflammatory cytokines. On the other hand, three mutant strains constructed from the N16961 strain with defects in the constitutive 2,3-BD pathway were also able to induce high levels of cytokines. When HT29 and A549 cells were treated with bacterial flagella, known proinflammatory cytokine inducers, and chemically synthesized 2,3-BD at various concentrations, a dose-dependent decrease in IL-8 and TNF-α production was observed, demonstrating the suppressive effect of 2,3-BD on the production of proinflammatory cytokines in epithelial cells. Upon cotreatment with extraneous 2,3-BD, elevated levels of IκBα, the inhibitor of the NF-κB pathway, were detected in both HT29 and A549 cells. Furthermore, treatments containing 2,3-BD elicited lower levels of NF-κB-responsive luciferase activity, demonstrating that the reduced cytokine production is likely through the inhibition of the NF-κB pathway. These results reveal a novel and potential role of 2,3-BD as an immune modulator that might have conferred a superior pathogenic potential of the El Tor over the Classical biotype.
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Mazumdar B, Ganguly S, Ghosh AN, Banerjee KK. The role of C-terminus carbohydrate-binding domain of Vibrio cholerae haemolysin/cytolysin in the conversion of the pre-pore β-barrel oligomer to a functional diffusion channel. Indian J Med Res 2011; 133:131-7. [PMID: 21415486 PMCID: PMC3089043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND & OBJECTIVES Vibrio cholerae cytolysin/hemolysin (VCC) is a 65 kDa pore-forming toxin (PFT) secreted by O1 El Tor and non-O1 strains. The purified toxin, which contains two C-terminus carbohydrate-binding domains in addition to the cytolytic domain at the core, causes lysis of a wide spectrum of eukaryotic cells at picomolar concentrations, apoptogenesis of intestinal and immune cells and accumulation of fluid in rabbit ligated ileal loop. Therefore, it may potentially complement the action of cholera toxin (CT) in diarrheagenic strains that do not produce CT. We showed earlier that β1-galactosyl-terminated glycoconjugates are strong inhibitors of its pore-forming activity, though carbohydrates are not functional receptors of VCC. Here, we investigate how the 15 kDa C-terminus β-prism lectin domain contributed to pore formation in erthrocytes. METHODS VCC was isolated from the culture supernatant of late log phase grown bacteria and purified to homogeneity by chromatography. The 50 kDa truncated variant was generated by restricted proteolysis. Liposome was prepared by sonication of a suspension of phospholipids and calceine release assay was done by spectrofluorometric monitoring of the released dye trapped in liposome. Formation of β-barrel oligomers in erythrocyte stroma was monitored by scanning electron microscopy. RESULTS Proteolytic truncation of the C-terminus β-prism lectin domain decreased hemolytic activity of the toxin by ~800-fold without causing a significant change in pore-forming activity toward synthetic lipid vesicles devoid of incorporated glycoproteins/glycolipids. Truncation at the C-terminus did not impair membrane-binding or assembly to the oligomeric pore. INTERPRETATION & CONCLUSIONS Our data indicated that the C-terminus domain played a critical role in translocation of the pre-pore oligomeric assembly from the cell surface or lipid-water interface to the hydrocarbon core of the membrane bilayer, signaling the formation of functional diffusion channels.
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Affiliation(s)
- Budhaditya Mazumdar
- Division of Biochemistry, National Institute of Cholera & Enteric Diseases (ICMR), Kolkata, India
| | - Sreerupa Ganguly
- Division of Biochemistry, National Institute of Cholera & Enteric Diseases (ICMR), Kolkata, India
| | - Amar N. Ghosh
- Division of Electron Microscopy, National Institute of Cholera & Enteric Diseases (ICMR), Kolkata, India
| | - Kalyan K. Banerjee
- Division of Biochemistry, National Institute of Cholera & Enteric Diseases (ICMR), Kolkata, India,Reprint requests: Dr Kalyan K. Banerjee, Scientist ‘F’, Division of Biochemistry, National Institute of Cholera & Enteric Diseases, Kolkata 700 010, India e-mail:
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Cinar HN, Kothary M, Datta AR, Tall BD, Sprando R, Bilecen K, Yildiz F, McCardell B. Vibrio cholerae hemolysin is required for lethality, developmental delay, and intestinal vacuolation in Caenorhabditis elegans. PLoS One 2010; 5:e11558. [PMID: 20644623 PMCID: PMC2903476 DOI: 10.1371/journal.pone.0011558] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 06/09/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Cholera toxin (CT) and toxin-co-regulated pili (TCP) are the major virulence factors of Vibrio cholerae O1 and O139 strains that contribute to the pathogenesis of disease during devastating cholera pandemics. However, CT and TCP negative V. cholerae strains are still able to cause severe diarrheal disease in humans through mechanisms that are not well understood. METHODOLOGY/PRINCIPAL FINDINGS To determine the role of other virulence factors in V. cholerae pathogenesis, we used a CT and TCP independent infection model in the nematode Caenorhabditis elegans and identified the hemolysin A (hlyA) gene as a factor responsible for animal death and developmental delay. We demonstrated a correlation between the severity of infection in the nematode and the level of hemolytic activity in the V. cholerae biotypes. At the cellular level, V. cholerae infection induces formation of vacuoles in the intestinal cells in a hlyA dependent manner, consistent with the previous in vitro observations. CONCLUSIONS/SIGNIFICANCE Our data strongly suggest that HlyA is a virulence factor in C. elegans infection leading to lethality and developmental delay presumably through intestinal cytopathic changes.
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Affiliation(s)
- Hediye Nese Cinar
- Division of Virulence Assessment, Food and Drug Administration, Laurel, Maryland, USA.
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Ou G, Rompikuntal PK, Bitar A, Lindmark B, Vaitkevicius K, Wai SN, Hammarström ML. Vibrio cholerae cytolysin causes an inflammatory response in human intestinal epithelial cells that is modulated by the PrtV protease. PLoS One 2009; 4:e7806. [PMID: 19907657 PMCID: PMC2771358 DOI: 10.1371/journal.pone.0007806] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Accepted: 10/10/2009] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Vibrio cholerae is the causal intestinal pathogen of the diarrheal disease cholera. It secretes the protease PrtV, which protects the bacterium from invertebrate predators but reduces the ability of Vibrio-secreted factor(s) to induce interleukin-8 (IL-8) production by human intestinal epithelial cells. The aim was to identify the secreted component(s) of V. cholerae that induces an epithelial inflammatory response and to define whether it is a substrate for PrtV. METHODOLOGY/PRINCIPAL FINDINGS Culture supernatants of wild type V. cholerae O1 strain C6706, its derivatives and pure V. cholerae cytolysin (VCC) were analyzed for the capacity to induce changes in cytokine mRNA expression levels, IL-8 and tumor necrosis factor-alpha (TNF-alpha) secretion, permeability and cell viability when added to the apical side of polarized tight monolayer T84 cells used as an in vitro model for human intestinal epithelium. Culture supernatants were also analyzed for hemolytic activity and for the presence of PrtV and VCC by immunoblot analysis. CONCLUSIONS/SIGNIFICANCE We suggest that VCC is capable of causing an inflammatory response characterized by increased permeability and production of IL-8 and TNF-alpha in tight monolayers. Pure VCC at a concentration of 160 ng/ml caused an inflammatory response that reached the magnitude of that caused by Vibrio-secreted factors, while higher concentrations caused epithelial cell death. The inflammatory response was totally abolished by treatment with PrtV. The findings suggest that low doses of VCC initiate a local immune defense reaction while high doses lead to intestinal epithelial lesions. Furthermore, VCC is indeed a substrate for PrtV and PrtV seems to execute an environment-dependent modulation of the activity of VCC that may be the cause of V. cholerae reactogenicity.
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Affiliation(s)
- Gangwei Ou
- Department of Clinical Microbiology/Immunology, Umeå University, Umeå, Sweden
| | | | - Aziz Bitar
- Department of Clinical Microbiology/Immunology, Umeå University, Umeå, Sweden
| | - Barbro Lindmark
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | | | - Sun Nyunt Wai
- Department of Molecular Biology, Umeå University, Umeå, Sweden
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Quorum sensing negatively regulates hemolysin transcriptionally and posttranslationally in Vibrio cholerae. Infect Immun 2009; 78:461-7. [PMID: 19858311 DOI: 10.1128/iai.00590-09] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent work has shown that in addition to cholera toxin (CT) and the toxin-coregulated pilus (TCP), other cytotoxic proteins in Vibrio cholerae also cause disease symptoms, and this is particularly evident in strains lacking CT. One such protein is the hemolysin encoded by hlyA. Here we show that, like CT and TCP, HlyA is repressed by the quorum-sensing-regulated transcription factor HapR. This repression occurs on two levels: one at the transcriptional level that is independent of the metalloprotease HapA and one at the posttranslational level that is mediated by HapA. The transcriptional regulation is significantly more apparent on solid media than in liquid cultures. This is the first time that hemolysis has been shown to be directly regulated by quorum sensing in V. cholerae, and it is interesting that, like other virulence factors, HlyA is also repressed by HapR, which is expressed late in infection.
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Kumar P, Peter WA, Thomas S. Rapid detection of virulence-associated genes in environmental strains of Vibrio cholerae by multiplex PCR. Curr Microbiol 2009; 60:199-202. [PMID: 19841974 DOI: 10.1007/s00284-009-9524-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2009] [Accepted: 10/01/2009] [Indexed: 12/01/2022]
Abstract
Vibrio cholerae, the causative agent of cholera is ubiquitously distributed in aquatic environment particularly in coastal waters, estuaries, and rivers. In the present investigation, a multiplex PCR assay was developed for the detection of virulence-associated genes (rtxA, tcpA, ctxA, hlyA, and sto) in environmental isolates of V. cholerae. A total of 90 strains isolated from different environmental sources were screened for the presence of virulence-associated genes. Our results showed that this method represents a simple, cost effective, and robust tool for rapid detection of virulence-associated genes. This multiplex PCR can be used for examining prevalence of virulence-associated genes and hence will be useful for better understanding of epidemiology of environmental V. cholerae.
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Affiliation(s)
- Praveen Kumar
- Cholera and Environmental Microbiology Lab, Department of Molecular Microbiology, Rajiv Gandhi Center for Biotechnology, Trivandrum, Kerala, India
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The Vibrio cholerae flagellar regulatory hierarchy controls expression of virulence factors. J Bacteriol 2009; 191:6555-70. [PMID: 19717600 DOI: 10.1128/jb.00949-09] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae is a motile bacterium responsible for the disease cholera, and motility has been hypothesized to be inversely regulated with virulence. We examined the transcription profiles of V. cholerae strains containing mutations in flagellar regulatory genes (rpoN, flrA, flrC, and fliA) by utilizing whole-genome microarrays. Results revealed that flagellar transcription is organized into a four-tiered hierarchy. Additionally, genes with proven or putative roles in virulence (e.g., ctx, tcp, hemolysin, and type VI secretion genes) were upregulated in flagellar regulatory mutants, which was confirmed by quantitative reverse transcription-PCR. Flagellar regulatory mutants exhibit increased hemolysis of human erythrocytes, which was due to increased transcription of the thermolabile hemolysin (tlh). The flagellar regulatory system positively regulates transcription of a diguanylate cyclase, CdgD, which in turn regulates transcription of a novel hemagglutinin (frhA) that mediates adherence to chitin and epithelial cells and enhances biofilm formation and intestinal colonization in infant mice. Our results demonstrate that the flagellar regulatory system modulates the expression of nonflagellar genes, with induction of an adhesin that facilitates colonization within the intestine and repression of virulence factors maximally induced following colonization. These results suggest that the flagellar regulatory hierarchy facilitates correct spatiotemporal expression patterns for optimal V. cholerae colonization and disease progression.
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Kumar P, Peter WA, Thomas S. Detection of virulence genes in Vibrio cholerae isolated from aquatic environment in Kerala, Southern India. Appl Biochem Biotechnol 2008; 151:256-62. [PMID: 18401561 DOI: 10.1007/s12010-008-8184-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Accepted: 02/19/2008] [Indexed: 11/29/2022]
Abstract
Vibrio cholerae is the etiologic agent of cholera. It is an autochthonous inhabitant of all aquatic environments. The virulence of V. cholerae is maintained by the CTX genetic element and tcpA gene. In the present investigation, environmental strains of V. cholerae isolated from different aquatic biotopes in Kerala were identified and serotyped. The antibiotic resistance pattern and presence of virulence and regulatory genes were examined. We found the presence of toxigenic non-O1/non-O139 strains harboring the CTX genetic element, heat-stable enterotoxin, rtxA gene, El Tor hemolysin, and Vibrio pathogenicity island (VPI). The strains also produced the cholera toxin (CT) as determined by monosialoganglioside enzyme-linked immunosorbent assay. A few strains belonging to the O1 serogroup but lacking the CTX genetic element were also observed. The majority of the environmental strains belonged to non-O1/non-O139 serogroup with many possessing toxR, ompU, heat-stable enterotoxin, and rtxA gene. The toxigenic non-O1/non-O139 strains exhibited resistance to trimethoprim, ampicillin, and polymixin B and intermediate resistance to co-trimoxazole. However, all other environmental strains were found resistant to ampicillin and polymixin B. Our findings demonstrate that the virulence genes are dispersed among the environmental strains of V. cholerae and a complex aquatic environment can give rise to pathogenic V. cholerae.
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Affiliation(s)
- Praveen Kumar
- Department of Molecular Microbiology, Rajiv Gandhi Centre for Biotechnology, Trivandrum, Kerala, India
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Identification and characterization of a repeat-in-toxin gene cluster in Vibrio anguillarum. Infect Immun 2008; 76:2620-32. [PMID: 18378637 DOI: 10.1128/iai.01308-07] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio anguillarum is the causative agent of vibriosis in fish. Hemolysins of V. anguillarum have been considered virulence factors during infection. One hemolysin gene, vah1, has been previously identified but does not account for all hemolytic activity. The mini-Tn10Km mutagenesis performed with a vah1 mutant resulted in a hemolysin-negative mutant. The region surrounding the mutation was cloned and sequenced, revealing a putative rtx operon with six genes (rtxACHBDE), where rtxA encodes an exotoxin, rtxC encodes an RtxA activator, rtxH encodes a conserved hypothetical protein, and rtxBDE encode the ABC transporters. Single mutations in rtx genes did not result in a hemolysin-negative phenotype. However, strains containing a mutation in vah1 and a mutation in an rtx gene resulted in a hemolysin-negative mutant, demonstrating that the rtx operon is a second hemolysin gene cluster in V. anguillarum M93Sm. Reverse transcription-PCR analysis revealed that the rtxC and rtxA genes are cotranscribed, as are the rtxBDE genes. Additionally, Vah1 and RtxA each have cytotoxic activity against Atlantic salmon kidney (ASK) cells. Single mutations in vah1 or rtxA attenuate the cytotoxicity of V. anguillarum M93Sm. A vah1 rtxA double mutant is no longer cytotoxic. Moreover, Vah1 and RtxA each have a distinct cytotoxic effect on ASK cells, Vah1 causes cell vacuolation, and RtxA causes cell rounding. Finally, wild-type and mutant strains were tested for virulence in juvenile Atlantic salmon. Only strains containing an rtxA mutation had reduced virulence, suggesting that RtxA is a major virulence factor for V. anguillarum.
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Vibrio cholerae cytolysin is essential for high enterotoxicity and apoptosis induction produced by a cholera toxin gene-negative V. cholerae non-O1, non-O139 strain. Microb Pathog 2008; 44:118-28. [DOI: 10.1016/j.micpath.2007.08.013] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Accepted: 08/10/2007] [Indexed: 12/21/2022]
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Olivier V, Haines GK, Tan Y, Satchell KJF. Hemolysin and the multifunctional autoprocessing RTX toxin are virulence factors during intestinal infection of mice with Vibrio cholerae El Tor O1 strains. Infect Immun 2007; 75:5035-42. [PMID: 17698573 PMCID: PMC2044521 DOI: 10.1128/iai.00506-07] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The seventh cholera pandemic that started in 1961 was caused by Vibrio cholerae O1 strains of the El Tor biotype. These strains produce the pore-forming toxin hemolysin, a characteristic used clinically to distinguish classical and El Tor biotypes. Even though extensive in vitro data on the cytolytic activities of hemolysin exist, the connection of hemolysin to virulence in vivo is not well characterized. To study the contribution of hemolysin and other accessory toxins to pathogenesis, we utilized the model of intestinal infection in adult mice sensitive to the actions of accessory toxins. In this study, we showed that 4- to 6-week-old streptomycin-fed C57BL/6 mice were susceptible to intestinal infection with El Tor strains, which caused rapid death at high doses. Hemolysin had the predominant role in lethality, with a secondary contribution by the multifunctional autoprocessing RTX (MARTX) toxin. Cholera toxin and hemagglutinin/protease did not contribute to lethality in this model. Rapid death was not caused by increased dissemination due to a damaged epithelium since the numbers of CFU recovered from spleens and livers 6 h after infection did not differ between mice inoculated with hemolysin-expressing strains and those infected with non-hemolysin-expressing strains. Although accessory toxins were linked to virulence, a strain defective in the production of accessory toxins was still immunogenic since mice immunized with a multitoxin-deficient strain were protected from a subsequent lethal challenge with the wild type. These data suggest that hemolysin and MARTX toxin contribute to vaccine reactogenicity but that the genes for these toxins can be deleted from vaccine strains without affecting vaccine efficacy.
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Affiliation(s)
- Verena Olivier
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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A Type III Secretion System in Vibrio cholerae Translocates a Formin/Spire Hybrid-like Actin Nucleator to Promote Intestinal Colonization. Cell Host Microbe 2007; 1:95-107. [DOI: 10.1016/j.chom.2007.03.005] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Revised: 03/01/2007] [Accepted: 03/22/2007] [Indexed: 12/17/2022]
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Martins LM, Catani CF, Falcón RM, Carbonell GV, Azzoni AA, Yano T. Induction of apoptosis in Vero cells by Aeromonas veronii biovar sobria vacuolating cytotoxic factor. ACTA ACUST UNITED AC 2007; 49:197-204. [PMID: 17286562 DOI: 10.1111/j.1574-695x.2006.00176.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recently, a cytotoxin named vacuolating cytotoxic factor (VCF) in Aeromonas sobria and Aeromonas veronii biovar sobria was described. We have now purified this factor using ion metallic affinity chromatography. The VCF is a nonhemolytic enterotoxin that acts as a serine protease. The toxin can be partially neutralized by serum antiaerolysin and it induced not only cytoplasmatic vacuole formation, but also mitochondrial disorders that must be signaling the apoptotic pathways, leading to Vero (African green monkey kidney) cell death. These results suggest that the VCF is a virulence factor of these bacteria, participating in the processes of human disease provoked by preformed toxins in food and infection.
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Gutierrez MG, Saka HA, Chinen I, Zoppino FCM, Yoshimori T, Bocco JL, Colombo MI. Protective role of autophagy against Vibrio cholerae cytolysin, a pore-forming toxin from V. cholerae. Proc Natl Acad Sci U S A 2007; 104:1829-34. [PMID: 17267617 PMCID: PMC1794277 DOI: 10.1073/pnas.0601437104] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Autophagy is the unique, regulated mechanism for the degradation of organelles. This intracellular process acts as a prosurvival pathway during cell starvation or stress and is also involved in cellular response against specific bacterial infections. Vibrio cholerae is a noninvasive intestinal pathogen that has been studied extensively as the causative agent of the human disease cholera. V. cholerae illness is produced primarily through the expression of a potent toxin (cholera toxin) within the human intestine. Besides cholera toxin, this bacterium secretes a hemolytic exotoxin termed V. cholerae cytolysin (VCC) that causes extensive vacuolation in epithelial cells. In this work, we explored the relationship between the vacuolation caused by VCC and the autophagic pathway. Treatment of cells with VCC increased the punctate distribution of LC3, a feature indicative of autophagosome formation. Moreover, VCC-induced vacuoles colocalized with LC3 in several cell lines, including human intestinal Caco-2 cells, indicating the interaction of the large vacuoles with autophagic vesicles. Electron microscopy analysis confirmed that the vacuoles caused by VCC presented hallmarks of autophagosomes. Additionally, biochemical evidence demonstrated the degradative nature of the VCC-generated vacuoles. Interestingly, autophagy inhibition resulted in decreased survival of Caco-2 cells upon VCC intoxication. Also, VCC failed to induce vacuolization in Atg5-/- cells, and the survival response of these cells against the toxin was dramatically impaired. These results demonstrate that autophagy acts as a cellular defense pathway against secreted bacterial toxins.
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Affiliation(s)
- Maximiliano Gabriel Gutierrez
- *Laboratorio de Biología Celular y Molecular, Instituto de Histología y Embriología–Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
| | - Hector Alex Saka
- Departamento de Bioquímica Clínica, Centro de Investigaciones en Bioquímica Clínica e Inmunología–CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina
| | - Isabel Chinen
- Servicio de Fisiopatogenia, Instituto Nacional de Enfermedades Infecciosas, Administración Nacional de Laboratorios e Institutos de Salud “Dr. Carlos G. Malbrán,” 1281 Buenos Aires, Argentina; and
| | - Felipe C. M. Zoppino
- *Laboratorio de Biología Celular y Molecular, Instituto de Histología y Embriología–Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
| | - Tamotsu Yoshimori
- Department of Cell Genetics, National Institute of Genetics, Yata 1111 Mishima, Shizuoka 455-8540, Japan
| | - Jose Luis Bocco
- Departamento de Bioquímica Clínica, Centro de Investigaciones en Bioquímica Clínica e Inmunología–CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina
- To whom correspondence may be addressed. E-mail:
or
| | - María Isabel Colombo
- *Laboratorio de Biología Celular y Molecular, Instituto de Histología y Embriología–Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
- To whom correspondence may be addressed. E-mail:
or
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Restrepo D, Huprikar SS, VanHorn K, Bottone EJ. O1 and non-O1 Vibrio cholerae bacteremia produced by hemolytic strains. Diagn Microbiol Infect Dis 2006; 54:145-8. [PMID: 16426794 DOI: 10.1016/j.diagmicrobio.2005.08.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Accepted: 08/02/2005] [Indexed: 01/09/2023]
Abstract
Vibrio cholerae are Gram-negative bacteria capable of producing serious infections. They are differentiated into O1 and non-O1 serogroups, depending on their ability to agglutinate with specific antiserum. In contrast to non-O1 V. cholerae, which are more prone to invading the bloodstream, V. cholerae O1 is rarely the cause of bacteremia. We describe 2 cases of O and non-O1 V. cholerae bacteremia in patients with hepatitis C virus cirrhosis. We postulate that the hemolytic properties of the isolates contributed to their virulence in immunocompromised hosts.
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Affiliation(s)
- Dalilah Restrepo
- Division of Infectious Diseases, Department of Medicine, The Mount Sinai Hospital, New York, NY, USA
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34
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Pantano S, Montecucco C. A molecular model of the Vibrio cholerae cytolysin transmembrane pore. Toxicon 2005; 47:35-40. [PMID: 16330061 DOI: 10.1016/j.toxicon.2005.09.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 08/31/2005] [Accepted: 09/22/2005] [Indexed: 01/05/2023]
Abstract
The cytotoxic activity of some of the most pathogenic strains of Vibrio cholerae is associated with a cytolysin protein (VCC), which forms oligomeric transmembrane pores and changes the permeability of intestinal cells. We present here a model structure of the transmembrane pore of VCC based on sequence comparison with other pore-forming toxins. VCC is suggested to form a transmembrane beta-barrel pore with a relatively large trans vestibule region. Calculations of the electrostatic profile within the pore lumen provide a rationale for the low conductance and selectivity of the VCC ion channel.
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Affiliation(s)
- Sergio Pantano
- Venetian Institute of Molecular Medicine (VIMM),Via Orus 2, 35129, Padova, Italy.
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35
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Chakraborty R, Chakraborty S, De K, Sinha S, Mukhopadhyay AK, Khanam J, Ramamurthy T, Takeda Y, Bhattacharya SK, Nair GB. Cytotoxic and cell vacuolating activity of Vibrio fluvialis isolated from paediatric patients with diarrhoea. J Med Microbiol 2005; 54:707-716. [PMID: 16014422 DOI: 10.1099/jmm.0.45820-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vibrio fluvialis is a halophilic Vibrio species associated with acute diarrhoeal illness in humans. It has the potential to cause outbreaks and has an association with paediatric diarrhoea. In this study, 11 V. fluvialis strains isolated from hospitalized patients with acute diarrhoea at the Infectious Diseases Hospital, Kolkata were extensively characterized. All the strains showed growth in peptone broth containing 7% NaCl. The strains showed variable results in Voges-Proskauer test and to a vibriostatic agent. There was also variation in their antibiograms, and some of the strains were multidrug resistant. Among the 11 strains, two showed only a single band difference in their PFGE profile and the remaining strains showed nine different PFGE patterns. However, unlike PFGE, the strains exhibited close matches and clustering in their ribotype patterns. The haemolytic effect on sheep red blood cells varied with strains. Partial sequence analysis revealed that the V. fluvialis haemolysin gene has 81% homology with that of the El Tor haemolysin of Vibrio cholerae. A striking finding was the capability of all the strains to evoke distinct cytotoxic and vacuolation effects on HeLa cells.
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Affiliation(s)
- Rupa Chakraborty
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - Subhra Chakraborty
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - Keya De
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - Sutapa Sinha
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - Asish K Mukhopadhyay
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - Jasmina Khanam
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - Thandavarayan Ramamurthy
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - Yoshifumi Takeda
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - Sujit K Bhattacharya
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
| | - G Balakrish Nair
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Beliaghata, Kolkata - 700 010, India 2Jadavpur University, Jadavpur, Kolkata - 700 032, India 3Jissen Women's University, 4-1-1, Osakane Hinocity, Tokyo 191-8510, Japan 4International Centre for Diarrhoeal Diseases Research, Bangladesh, Mohakhali, Dhaka - 1212, Bangladesh
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36
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Nardi ARM, Salvadori MR, Coswig LT, Gatti MSV, Leite DS, Valadares GF, Neto MG, Shocken-Iturrino RP, Blanco JE, Yano T. Type 2 heat-labile enterotoxin (LT-II)-producing Escherichia coli isolated from ostriches with diarrhea. Vet Microbiol 2004; 105:245-9. [PMID: 15708822 DOI: 10.1016/j.vetmic.2004.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2004] [Revised: 11/12/2004] [Accepted: 11/12/2004] [Indexed: 10/26/2022]
Abstract
The culture supernatant of Escherichia coli, isolated from ostriches with diarrhea in Brazil, caused elongation in Vero cell, rounding in Chinese hamster ovary (CHO) cells and a cytoplasmic vacuolation in ostrich embryo fibroblasts (OEF), but it was not cytotoxic for chicken embryo fibroblasts (CEF). These effects were not neutralized by antiserum to cholera toxin. Polymerase chain reaction assays showed that the ostrich E. coli contained the gene encoding (eltII-A), but not those for type 1 heat-labile enterotoxin (eltA), heat-stable enterotoxins (estA, estB), verocytotoxins (stx-I, stx-II), or cytotoxic necrotizing factors (cnf 1, cnf 2). All isolates belonged to serotype O15:H8. The enteropathogenic relevance of LT-II in ostrich diarrhea remains undetermined.
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Affiliation(s)
- Ana Rita M Nardi
- Faculdade de Medicina Veterinária, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Jaboticabal, SP, Brazil
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37
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Nakasone N, Toma C, Song T, Iwanaga M. Purification and characterization of a novel metalloprotease isolated fromAeromonas caviae. FEMS Microbiol Lett 2004. [DOI: 10.1111/j.1574-6968.2004.tb09687.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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38
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de Bernard M, Cappon A, Del Giudice G, Rappuoli R, Montecucco C. The multiple cellular activities of the VacA cytotoxin of Helicobacter pylori. Int J Med Microbiol 2004; 293:589-97. [PMID: 15149036 DOI: 10.1078/1438-4221-00299] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Helicobacter pylori has elaborated a unique set of virulence factors that allow it to colonize the stomach wall. These factors include urease, helicoidal shape, flagella, adhesion and pro-inflammatory molecules. Here we discuss the molecular and cellular mechanisms of action of the vacuolating cytotoxin VacA. Its activities are discussed in terms of tissue alterations which promote the release of nutrients necessary to the growth and survival of the bacterium in its nutrient-poor ecological niche. This toxin also shows some pro-inflammatory and immunosuppressive activities which may be functional to the establishment of a chronic type of inflammation.
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Affiliation(s)
- Marina de Bernard
- Dipartimento di Scienze Biomediche, Università di Padova, Istituto Veneto di Medicina Molecolare, Padova, Italy
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Vance RE, Zhu J, Mekalanos JJ. A constitutively active variant of the quorum-sensing regulator LuxO affects protease production and biofilm formation in Vibrio cholerae. Infect Immun 2003; 71:2571-6. [PMID: 12704130 PMCID: PMC153284 DOI: 10.1128/iai.71.5.2571-2576.2003] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae normally inhabits aquatic habitats but can cause a severe diarrheal illness in humans. Its arsenal of virulence factors includes a secreted hemagglutinin (HA) protease. An HA protease-deficient mutant of V. cholerae was isolated and designated E7946 mpc. E7946 mpc was found to contain a point mutation in the luxO quorum-sensing regulator. In accordance with this finding, E7946 mpc exhibits a defect in quorum sensing. The mutant luxO allele [luxO(Con)] produces a protein with a leucine-to-glutamine substitution at amino acid 104. Transfer of the luxO(Con) allele to an otherwise wild-type background was sufficient to eliminate HA protease expression; conversely, deletion of luxO(Con) from E7946 mpc restored protease activity. We demonstrate that LuxO(Con) constitutively represses the transcription of hapR, an essential positive regulator of HA protease. Interestingly, strains harboring luxO(Con) form enhanced biofilms, and enhanced biofilm formation does not appear to be dependent on reduced HA protease expression. Taken together, the results confirm the role of LuxO as a central "switch" that coordinately regulates virulence-related phenotypes such as protease production and biofilm formation.
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Affiliation(s)
- Russell E Vance
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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40
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Pichel M, Rivas M, Chinen I, Martín F, Ibarra C, Binsztein N. Genetic diversity of Vibrio cholerae O1 in Argentina and emergence of a new variant. J Clin Microbiol 2003; 41:124-34. [PMID: 12517837 PMCID: PMC149600 DOI: 10.1128/jcm.41.1.124-134.2003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genetic diversity of Vibrio cholerae O1 strains from Argentina was estimated by random amplified polymorphic DNA (RAPD) analysis and pulsed-field gel electrophoresis (PFGE). Twenty-nine isolates carrying the virulence genes ctxA, zot, ace, and tcpA appeared to represent a single clone by both typing methods; while 11 strains lacking these virulence genes exhibited several heterogeneous RAPD and PFGE patterns. Among the last group, a set of isolates from the province Tucumán showed a single RAPD pattern and four closely related PFGE profiles. These strains, isolated from patients with diarrhea, did not produce the major V. cholerae O1 virulence determinants, yet cell supernatants of these isolates caused a heat-labile cytotoxic effect on Vero and Y-1 cells and elicited significant variations on the water flux and short-circuit current in human small intestine mounted in an Ussing chamber. All these effects were completely abolished by incubation with a specific antiserum against El Tor hemolysin, suggesting that this virulence factor was responsible for the toxic activity on both the epithelial cells and the small intestine specimens and may hence be involved in the development of diarrhea. We propose "Tucumán variant" as the designation for this new cluster of cholera toxin-negative V. cholerae O1 strains.
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Affiliation(s)
- Mariana Pichel
- Departamento de Bacteriología, Instituto Nacional de Enfermedades Infecciosas, ANLIS Dr. Carlos G. Malbrán, Ministerio de Salud, 1281 Capital Federal, Argentina
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41
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Guyer DM, Radulovic S, Jones FE, Mobley HLT. Sat, the secreted autotransporter toxin of uropathogenic Escherichia coli, is a vacuolating cytotoxin for bladder and kidney epithelial cells. Infect Immun 2002; 70:4539-46. [PMID: 12117966 PMCID: PMC128167 DOI: 10.1128/iai.70.8.4539-4546.2002] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The secreted autotransporter toxin (Sat) of uropathogenic Escherichia coli exhibits cytopathic activity upon incubation with HEp-2 cells. We further investigated the effects of Sat on cell lines more relevant to the urinary tract, namely, those derived from bladder and kidney epithelium. Sat elicited elongation of cells and apparent loosening of cellular junctions upon incubation with Vero kidney cells. Additionally, incubation with Sat triggered significant vacuolation within the cytoplasm of both human bladder (CRL-1749) and kidney (CRL-1573) cell lines. This activity has been associated with only a few other known toxins. Following transurethral infection of CBA mice with a sat mutant, no reduction of CFU in urine, bladder, or kidney tissue was seen compared to that in mice infected with wild-type E. coli CFT073. However, significant histological changes were observed within the kidneys of mice infected with wild-type E. coli CFT073, including dissolution of the glomerular membrane and vacuolation of proximal tubule cells. Such damage was not observed in kidney sections of mice infected with a Sat-deficient mutant. These results indicate that Sat, a vacuolating cytotoxin expressed by uropathogenic E. coli CFT073, elicits defined damage to kidney epithelium during upper urinary tract infection and thus contributes to pathogenesis of urinary tract infection.
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Affiliation(s)
- Debra M Guyer
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore 21201, USA
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42
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Moschioni M, Tombola F, de Bernard M, Coelho A, Zitzer A, Zoratti M, Montecucco C. The Vibrio cholerae haemolysin anion channel is required for cell vacuolation and death. Cell Microbiol 2002; 4:397-409. [PMID: 12102686 DOI: 10.1046/j.1462-5822.2002.00199.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Several strains of Vibrio cholerae secrete a haemolytic toxin of 63 kDa, termed V. cholerae cytolysin (VCC). This toxin causes extensive vacuolation and death of cells in culture and forms an anion-selective channel in planar lipid bilayers and in cells. Here, we identify inhibitors of the VCC anion channel and show that the formation of the anion channel is necessary for the development of the vacuoles and for the cell death induced by this toxin. Using markers of cell organelles, we show that vacuoles derive from different intracellular compartments and we identify the contribution of late endosomes and of the trans-Golgi network in vacuole biogenesis.
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Affiliation(s)
- Monica Moschioni
- Centro CNR Biomembrane and Dipartimento di Scienze Biomediche Sperimentali, Università di Padova, Via G. Colombo 3, 35121, Padova, Italy
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Fullner KJ, Boucher JC, Hanes MA, Haines GK, Meehan BM, Walchle C, Sansonetti PJ, Mekalanos JJ. The contribution of accessory toxins of Vibrio cholerae O1 El Tor to the proinflammatory response in a murine pulmonary cholera model. J Exp Med 2002; 195:1455-62. [PMID: 12045243 PMCID: PMC2193536 DOI: 10.1084/jem.20020318] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
The contribution of accessory toxins to the acute inflammatory response to Vibrio cholerae was assessed in a murine pulmonary model. Intranasal administration of an El Tor O1 V. cholerae strain deleted of cholera toxin genes (ctxAB) caused diffuse pneumonia characterized by infiltration of PMNs, tissue damage, and hemorrhage. By contrast, the ctxAB mutant with an additional deletion in the actin-cross-linking repeats-in-toxin (RTX) toxin gene (rtxA) caused a less severe pathology and decreased serum levels of proinflammatory molecules interleukin (IL)-6 and murine macrophage inflammatory protein (MIP)-2. These data suggest that the RTX toxin contributes to the severity of acute inflammatory responses. Deletions within the genes for either hemagglutinin/protease (hapA) or hemolysin (hlyA) did not significantly affect virulence in this model. Compound deletion of ctxAB, hlyA, hapA, and rtxA created strain KFV101, which colonized the lung but induced pulmonary disease with limited inflammation and significantly reduced serum titers of IL-6 and MIP-2. 100% of mice inoculated with KFV101 survive, compared with 20% of mice inoculated with the ctxAB mutant. Thus, the reduced virulence of KFV101 makes it a prototype for multi-toxin deleted vaccine strains that could be used for protection against V. cholerae without the adverse effects of the accessory cholera toxins.
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Affiliation(s)
- Karla Jean Fullner
- Departments of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Morton 6-626, Chicago, IL 60611, USA.
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44
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Martins LM, Marquez RF, Yano T. Incidence of toxic Aeromonas isolated from food and human infection. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 2002; 32:237-42. [PMID: 11934569 DOI: 10.1111/j.1574-695x.2002.tb00559.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
One hundred and ninety four Aeromonas isolates (99 from food and 95 from clinical sources) were analyzed as to the species involved and the toxins produced. Of the clinical isolates of Aeromonas, 29.4% were enterotoxigenic, 43.1% were hemolytic and 89% were cytotoxigenic. Among the food isolates, 18.2% were enterotoxigenic, 17.1% were hemolytic and 72.7% were cytotoxigenic. Aeromonas sobria and Aeromonas veronii produced more enterotoxin and cytotoxin than the other isolates, whereas A. veronii and Aeromonas salmonicida produced cell-free hemolysin. Most of the isolates produced cytotoxins (81%) active on Vero (green monkey kidney) and Chinese hamster ovary cells, but only the culture supernatant of A. sobria produced vacuolation in these cell lines.
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Affiliation(s)
- Luciano Moura Martins
- Departamento de Microbiologia e Imunologia, Instituto de Biologia (IB), Universidade Estadual de Campinas (UNICAMP), C.P. 6109, 13081-970, Campinas, SP, Brazil
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45
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10 Membranolytic toxins. J Microbiol Methods 2002. [DOI: 10.1016/s0580-9517(02)31011-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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46
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Abstract
Like a variety of other pathogenic bacteria, Aeromonas hydrophila secretes a pore-forming toxin that contribute to its virulence. The last decade has not only increased our knowledge about the structure of this toxin, called aerolysin, but has also shed light on how it interacts with its target cell and how the cell reacts to this stress. Whereas pore-forming toxins are generally thought to lead to brutal death by osmotic lysis of the cell, based on what is observed for erythrocytes, recent studies have started to reveal far more complicated pathways leading to death of nucleated mammalian cells.
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Affiliation(s)
- M Fivaz
- Department of Biochemistry, Faculty of Sciences, University of Geneva, 30 quai E. Ansermet, 1211 Geneva 4, Switzerland
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47
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Fivaz M, Abrami L, Tsitrin Y, van der Goot FG. Aerolysin from Aeromonas hydrophila and related toxins. Curr Top Microbiol Immunol 2001; 257:35-52. [PMID: 11417121 DOI: 10.1007/978-3-642-56508-3_3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- M Fivaz
- Department of Biochemistry, Faculty of Sciences, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland
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48
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Abstract
A PCR that amplifies a recently discovered Vibrio cholerae RTX (repeat in toxin) toxin gene was developed. Among 166 clinical and environmental isolates of V. cholerae causing epidemics and sporadic cases of cholera in various parts of the world, all were found to be toxigenic by both PCR and HEp-2 cell cytotoxicity assay. Standard strains of the classical biotype containing a deletion within the gene cluster exhibited negative results by both assays. This is the first rapid genotyping method for differentiation of V. cholerae O1 classical biotype strains from El Tor biotype strains as well as strains of other non-O1 serogroups including serogroup O139. The PCR assay that was developed also specifically detects RTX toxin genes in V. cholerae, as clinical isolates of Vibrio parahaemolyticus, diarrheagenic Escherichia coli, Aeromonas species, and Plesiomonas species were all negative by the RTX toxin-specific PCR as well as the HEp-2 cytotoxicity assay. These findings highlight the characteristics of the RTX toxins in V. cholerae. Their role in the pathogenicity of the bacterium requires further investigation.
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Affiliation(s)
- K H Chow
- Department of Microbiology, The University of Hong Kong, China
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49
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Figueroa-Arredondo P, Heuser JE, Akopyants NS, Morisaki JH, Giono-Cerezo S, Enríquez-Rincón F, Berg DE. Cell vacuolation caused by Vibrio cholerae hemolysin. Infect Immun 2001; 69:1613-24. [PMID: 11179335 PMCID: PMC98064 DOI: 10.1128/iai.69.3.1613-1624.2001] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Non-O1 strains of Vibrio cholerae implicated in gastroenteritis and diarrhea generally lack virulence determinants such as cholera toxin that are characteristic of epidemic strains; the factors that contribute to their virulence are not understood. Here we report that at least one-third of diarrhea-associated nonepidemic V. cholerae strains from Mexico cause vacuolation of cultured Vero cells. Detailed analyses indicated that this vacuolation was related to that caused by aerolysin, a pore-forming toxin of Aeromonas; it involved primarily the endoplasmic reticulum at early times (approximately 1 to 4 h after exposure), and resulted in formation of large, acidic, endosome-like multivesicular vacuoles (probably autophagosomes) only at late times (approximately 16 h). In contrast to vacuolation caused by Helicobacter pylori VacA protein, that induced by V. cholerae was exacerbated by agents that block vacuolar proton pumping but not by endosome-targeted weak bases. It caused centripetal redistribution of endosomes, reflecting cytoplasmic alkalinization. The gene for V. cholerae vacuolating activity was cloned and was found to correspond to hlyA, the structural gene for hemolysin. HlyA protein is a pore-forming toxin that causes ion leakage and, ultimately, eukaryotic cell lysis. Thus, a distinct form of cell vacuolation precedes cytolysis at low doses of hemolysin. We propose that this vacuolation, in itself, contributes to the virulence of V. cholerae strains, perhaps by perturbing intracellular membrane trafficking or ion exchange in target cells and thereby affecting local intestinal inflammatory or other defense responses.
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Affiliation(s)
- P Figueroa-Arredondo
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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50
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Mel SF, Fullner KJ, Wimer-Mackin S, Lencer WI, Mekalanos JJ. Association of protease activity in Vibrio cholerae vaccine strains with decreases in transcellular epithelial resistance of polarized T84 intestinal epithelial cells. Infect Immun 2000; 68:6487-92. [PMID: 11035765 PMCID: PMC97739 DOI: 10.1128/iai.68.11.6487-6492.2000] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Culture supernatants prepared from reactogenic strains of Vibrio cholerae cause a decrease in the transcellular epithelial resistance of T84 intestinal cells. This decrease correlates with the presence of hemagglutinin/protease but not with the presence of other potential accessory toxins or proteases. These data suggest a possible role for hemagglutinin/protease in reactogenicity, although other factors may also contribute.
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Affiliation(s)
- S F Mel
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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