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Gong Y, Jiang R, Guo RH, Jo SJ, Jeong H, Moon K, Rhee JH, Kim YR. TolCV1 inhibition by NPPB renders Vibrio vulnificus less virulent and more susceptible to antibiotics. Antimicrob Agents Chemother 2025; 69:e0050224. [PMID: 39670721 PMCID: PMC11784226 DOI: 10.1128/aac.00502-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2024] [Accepted: 11/24/2024] [Indexed: 12/14/2024] Open
Abstract
Bacterial efflux pumps play important roles in the antibiotic resistance and excretion of virulence factors. We previously characterized that TolCV1, a component of efflux pumps, plays critical roles in resistance to antibiotics and bile and also RtxA1 toxin secretion of Vibrio vulnificus. In this context, we speculated that TolCV1 blockers would have a dual effect of enhancing susceptibility to antibiotics and suppressing virulence of V. vulnificus. Here, we show that the chloride channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) increases susceptibility to antibiotics and suppresses cytotoxicity of V. vulnificus through inhibition of TolCV1. NPPB significantly decreased TolCV1 in V. vulnificus cells by liberating the protein from the cell body. Checkerboard assay showed that NPPB enhanced the antimicrobial activities of antibiotics such as kanamycin, tetracycline, erythromycin, and ampicillin against V. vulnificus. Moreover, NPPB inhibited the secretion of RtxA1 toxin and protected host cells from V. vulnificus-induced cytotoxicity. In addition, NPPB markedly suppressed V. vulnificus growth in the presence of bile salts and enhanced the therapeutic effect of tetracycline in V. vulnificus-infected mice. The safety and efficacy of NPPB were confirmed at the cellular and animal levels. Collectively, TolCV1 inhibition by NPPB renders V. vulnificus less virulent and more susceptible to antibiotics.
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Affiliation(s)
- Yue Gong
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Chonnam National University, Gwangju, Republic of Korea
- Department of Pharmacy, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Rui Jiang
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Chonnam National University, Gwangju, Republic of Korea
| | - Rui Hong Guo
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Chonnam National University, Gwangju, Republic of Korea
| | - Se Jin Jo
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Chonnam National University, Gwangju, Republic of Korea
| | - Hyeongju Jeong
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Chonnam National University, Gwangju, Republic of Korea
| | - Kyuho Moon
- College of Pharmacy, Kyung Hee University, Seoul, Republic of Korea
| | - Joon Haeng Rhee
- Clinical Vaccine R&D Center and Department of Microbiology, Combinatorial Tumor Immunotherapy MRC, Chonnam National University Medical School, Hwasun-gun, Jeonnam, Republic of Korea
| | - Young Ran Kim
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Chonnam National University, Gwangju, Republic of Korea
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He Q, Yuan H, Bu Y, Hu J, Olatunde OZ, Gong L, Wang P, Hu T, Li Y, Lu C. Mesoporous Oxidized Mn-Ca Nanoparticles as Potential Antimicrobial Agents for Wound Healing. Molecules 2024; 29:2960. [PMID: 38998912 PMCID: PMC11243354 DOI: 10.3390/molecules29132960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2024] [Revised: 06/07/2024] [Accepted: 06/16/2024] [Indexed: 07/14/2024] Open
Abstract
Managing chronic non-healing wounds presents a significant clinical challenge due to their frequent bacterial infections. Mesoporous silica-based materials possess robust wound-healing capabilities attributed to their renowned antimicrobial properties. The current study details the advancement of mesoporous silicon-loaded MnO and CaO molecules (HMn-Ca) against bacterial infections and chronic non-healing wounds. HMn-Ca was synthesized by reducing manganese chloride and calcium chloride by urotropine solution with mesoporous silicon as the template, thereby transforming the manganese and calcium ions on the framework of mesoporous silicon. The developed HMn-Ca was investigated using scanning electron microscopy (SEM), transmission electron microscope (TEM), ultraviolet-visible (UV-visible), and visible spectrophotometry, followed by the determination of Zeta potential. The production of reactive oxygen species (ROS) was determined by using the 3,3,5,5-tetramethylbenzidine (TMB) oxidation reaction. The wound healing effectiveness of the synthesized HMn-Ca is evaluated in a bacterial-infected mouse model. The loading of MnO and CaO inside mesoporous silicon enhanced the generation of ROS and the capacity of bacterial capture, subsequently decomposing the bacterial membrane, leading to the puncturing of the bacterial membrane, followed by cellular demise. As a result, treatment with HMn-Ca could improve the healing of the bacterial-infected wound, illustrating a straightforward yet potent method for engineering nanozymes tailored for antibacterial therapy.
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Affiliation(s)
- Qianfeng He
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- College of Chemistry, Fuzhou University, Fuzhou 350116, China
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
| | - Hui Yuan
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
| | - Youshen Bu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- College of Chemistry, Fuzhou University, Fuzhou 350116, China
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
| | - Jiangshan Hu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
| | - Olagoke Zacchaeus Olatunde
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
| | - Lijie Gong
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
| | - Peiyuan Wang
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
| | - Ting Hu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
| | - Yuhang Li
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
- Key Laboratory of Functional and Clinical Translational Medicine, Fujian Province University, Xiamen Medical College, Xiamen 361023, China
| | - Canzhong Lu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China; (Q.H.); (H.Y.); (Y.B.); (J.H.); (O.Z.O.); (L.G.); (P.W.); (T.H.)
- Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen 361021, China
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Hernández-Cabanyero C, Sanjuán E, Mercado L, Amaro C. Evidence that fish death after Vibrio vulnificus infection is due to an acute inflammatory response triggered by a toxin of the MARTX family. FISH & SHELLFISH IMMUNOLOGY 2023; 142:109131. [PMID: 37832748 DOI: 10.1016/j.fsi.2023.109131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 09/27/2023] [Accepted: 10/01/2023] [Indexed: 10/15/2023]
Abstract
Vibrio vulnificus is an emerging zoonotic pathogen associated with fish farms that is capable of causing a hemorrhagic septicemia known as warm-water vibriosis. According to a recent transcriptomic and functional study, the death of fish due to vibriosis is more related to the inflammatory response of the host than to the tissue lesions caused by the pathogen. In this work, we hypothesize that the RtxA1 toxin (a V. vulnificus toxin of the MARTX (Multifunctional Autoprocessing Repeats in Toxin) family) is the key virulence factor that would directly or indirectly trigger this fatal inflammatory response. Our hypothesis was based on previous studies that showed that rtxA1-deficient mutants maintained their ability to colonize and invade, but were unable to kill fish. To demonstrate this hypothesis, we infected eels (model of fish vibriosis) by immersion with a mutant deficient in RtxA1 production and analyzed their transcriptome in blood, red blood cells and white blood cells during early vibriosis (0, 3 and 12 h post-infection). The transcriptomic results were compared with those obtained in the previous study in which eels were infected with the V. vulnificus parental strain, and were functionally validated. Overall, our results confirm that fish death after V. vulnificus infection is due to an acute, early and atypical inflammatory response triggered by RtxA1 in which red blood cells seem to play a central role. These results could be relevant to other vibriosis as the toxins of this family are widespread in the Vibrio genus.
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Affiliation(s)
- Carla Hernández-Cabanyero
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Dr. Moliner, 50, 46100, Valencia, Spain
| | - Eva Sanjuán
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Dr. Moliner, 50, 46100, Valencia, Spain
| | - Luis Mercado
- Instituto de Biología. Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Carmen Amaro
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Dr. Moliner, 50, 46100, Valencia, Spain.
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Lu K, Li Y, Chen R, Yang H, Wang Y, Xiong W, Xu F, Yuan Q, Liang H, Xiao X, Huang R, Chen Z, Tian C, Wang S. Pathogenic mechanism of Vibrio vulnificus infection. Future Microbiol 2023; 18:373-383. [PMID: 37158065 DOI: 10.2217/fmb-2022-0243] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023] Open
Abstract
Vibrio vulnificus is a fatal, opportunistic human pathogen transmitted through the consumption of raw/undercooked seafood or direct contact. V. vulnificus infection progresses rapidly and has severe consequences; some cases may require amputation or result in death. Growing evidence suggests that V. vulnificus virulence factors and regulators play a large role in disease progression, involving host resistance, cellular damage, iron acquisition, virulence regulation and host immune responses. Its disease mechanism remains largely undefined. Further evaluation of pathogenic mechanisms is important for selecting appropriate measures to prevent and treat V. vulnificus infection. In this review, the possible pathogenesis of V. vulnificus infection is described to provide a reference for treatment and prevention.
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Affiliation(s)
- Kun Lu
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Yang Li
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Rui Chen
- Department of Orthopedics, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Hua Yang
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Yong Wang
- Hemodialysis Center, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Wei Xiong
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Fang Xu
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Qijun Yuan
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Haihui Liang
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Xian Xiao
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Renqiang Huang
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Zhipeng Chen
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Chunou Tian
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
| | - Songqing Wang
- Department of Neurosurgery, First Naval Hospital of Southern Theater Command, Zhanjiang, 524000, China
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Characteristic Metabolic Changes in Skeletal Muscle Due to Vibrio vulnificus Infection in a Wound Infection Model. mSystems 2023; 8:e0068222. [PMID: 36939368 PMCID: PMC10153474 DOI: 10.1128/msystems.00682-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2023] Open
Abstract
Vibrio vulnificus is a bacterium that inhabits warm seawater or brackish water environments and causes foodborne diseases and wound infections. In severe cases, V. vulnificus invades the skeletal muscle tissue, where bacterial proliferation leads to septicemia and necrotizing fasciitis with high mortality. Despite this characteristic, information on metabolic changes in tissue infected with V. vulnificus is not available. Here, we elucidated the metabolic changes in V. vulnificus-infected mouse skeletal muscle using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). Metabolome analysis revealed changes in muscle catabolites and energy metabolites during V. vulnificus infection. In particular, succinic acid accumulated but fumaric acid decreased in the infected muscle. However, the virulence factor deletion mutant revealed that changes in metabolites and bacterial proliferation were abolished in skeletal muscle infected with a multifunctional-autoprocessing repeats-in-toxin (MARTX) mutant. On the other hand, mice that were immunosuppressed via cyclophosphamide (CPA) treatment exhibited a similar level of bacterial counts and metabolites between the wild type and MARTX mutant. Therefore, our data indicate that V. vulnificus induces metabolic changes in mouse skeletal muscle and proliferates by using the MARTX toxin to evade the host immune system. This study indicates a new correlation between V. vulnificus infections and metabolic changes that lead to severe reactions or damage to host skeletal muscle. IMPORTANCE V. vulnificus causes necrotizing skin and soft tissue infections (NSSTIs) in severe cases, with high mortality and sign of rapid deterioration. Despite the severity of the infection, the dysfunction of the host metabolism in skeletal muscle triggered by V. vulnificus is poorly understood. In this study, by using a mouse wound infection model, we revealed characteristic changes in muscle catabolism and energy metabolism in skeletal muscle associated with bacterial proliferation in the infected tissues. Understanding such metabolic changes in V. vulnificus-infected tissue may provide crucial information to identify the mechanism via which V. vulnificus induces severe infections. Moreover, our metabolite data may be useful for the recognition, identification, or detection of V. vulnificus infections in clinical studies.
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Integrated Analysis of Transcriptome and Metabolome Reveals Distinct Responses of Pelteobagrus fulvidraco against Aeromonas veronii Infection at Invaded and Recovering Stage. Int J Mol Sci 2022; 23:ijms231710121. [PMID: 36077519 PMCID: PMC9456318 DOI: 10.3390/ijms231710121] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 08/29/2022] [Accepted: 09/01/2022] [Indexed: 11/16/2022] Open
Abstract
Yellow catfish (Pelteobagrus fulvidraco) is an important aquaculture fish susceptible to Aeromonas veronii infection, which causes acute death resulting in huge economic losses. Understanding the molecular processes of host immune defense is indispensable to disease control. Here, we conducted the integrated and comparative analyses of the transcriptome and metabolome of yellow catfish in response to A. veronii infection at the invaded stage and recovering stage. The crosstalk between A. veronii-induced genes and metabolites uncovered the key biomarkers and pathways that strongest contribute to different response strategies used by yellow catfish at corresponding defense stages. We found that at the A. veronii invading stage, the immune defense was strengthened by synthesizing lipids with energy consumption to repair the skin defense line and accumulate lipid droplets promoting intracellular defense line; triggering an inflammatory response by elevating cytokine IL-6, IL-10 and IL-1β following PAMP-elicited mitochondrial signaling, which was enhanced by ROS produced by impaired mitochondria; and activating apoptosis by up-regulating caspase 3, 7 and 8 and Prostaglandin F1α, meanwhile down-regulating FoxO3 and BCL6. Apoptosis was further potentiated via oxidative stress caused by mitochondrial dysfunction and exceeding inflammatory response. Additionally, cell cycle arrest was observed. At the fish recovering stage, survival strategies including sugar catabolism with D-mannose decreasing; energy generation through the TCA cycle and Oxidative phosphorylation pathways; antioxidant protection by enhancing Glutathione (oxidized), Anserine, and α-ketoglutarate; cell proliferation by inducing Cyclin G2 and CDKN1B; and autophagy initiated by FoxO3, ATG8 and ATP6V1A were highlighted. This study provides a comprehensive picture of yellow catfish coping with A. veronii infection, which adds new insights for deciphering molecular mechanisms underlying fish immunity and developing stage-specific disease control techniques in aquaculture.
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Vibrio vulnificus PlpA facilitates necrotic host cell death induced by the pore forming MARTX toxin. J Microbiol 2022; 60:224-233. [PMID: 35102528 DOI: 10.1007/s12275-022-1448-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 01/10/2022] [Accepted: 01/10/2022] [Indexed: 10/19/2022]
Abstract
Opportunistic pathogen Vibrio vulnificus causes severe systemic infection in humans with high mortality. Although multiple exotoxins have been characterized in V. vulnificus, their interactions and potential synergistic roles in pathogen-induced host cell death have not been investigated previously. By employing a series of multiple exotoxin deletion mutants, we investigated whether specific exotoxins of the pathogen functioned together to achieve severe and rapid necrotic cell death. Human epithelial cells treated with V. vulnificus with a plpA deletion background exhibited an unusually prolonged cell blebbing, suggesting the importance of PlpA, a phospholipase A2, in rapid necrotic cell death by this pathogen. Additional deletion of the rtxA gene encoding the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin did not result in necrotic cell blebs. However, if the rtxA gene was engineered to produce an effector-free MARTX toxin, the cell blebbing was observed, indicating that the pore forming activity of the MARTX toxin is sufficient, but the MARTX toxin effector domains are not necessary, for the blebbing. When a recombinant PlpA was treated on the blebbed cells, the blebs were completely disrupted. Consistent with this, MARTX toxin-pendent rapid release of cytosolic lactate dehydrogenase was significantly delayed in the plpA deletion background. Mutations in other exotoxins such as elastase, cytolysin/hemolysin, and/or extracellular metalloprotease did not affect the bleb formation or disruption. Together, these findings indicate that the pore forming MARTX toxin and the phospholipase A2, PlpA, cooperate sequentially to achieve rapid necrotic cell death by inducing cell blebbing and disrupting the blebs, respectively.
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Gong Y, Guo RH, Rhee JH, Kim YR. TolCV1 Has Multifaceted Roles During Vibrio vulnificus Infection. Front Cell Infect Microbiol 2021; 11:673222. [PMID: 33996641 PMCID: PMC8120275 DOI: 10.3389/fcimb.2021.673222] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 04/12/2021] [Indexed: 01/22/2023] Open
Abstract
RtxA1 is a major cytotoxin of Vibrio vulnificus (V. vulnificus) causing fatal septicemia and necrotic wound infections. Our previous work has shown that RpoS regulates the expression and secretion of V. vulnificus RtxA1 toxin. This study was conducted to further investigate the potential mechanisms of RpoS on RtxA1 secretion. First, V. vulnificus TolCV1 and TolCV2 proteins, two Escherichia coli TolC homologs, were measured at various time points by Western blotting. The expression of TolCV1 was increased time-dependently, whereas that of TolCV2 was decreased. Expression of both TolCV1 and TolCV2 was significantly downregulated in an rpoS deletion mutation. Subsequently, we explored the roles of TolCV1 and TolCV2 in V. vulnificus pathogenesis. Western blot analysis showed that RtxA1 toxin was exported by TolCV1, not TolCV2, which was consistent with the cytotoxicity results. Furthermore, the expression of TolCV1 and TolCV2 was increased after treatment of the host signal bile salt and the growth of tolCV1 mutant was totally abolished in the presence of bile salt. A tolCV1 mutation resulted in significant reduction of V. vulnificus induced-virulence in mice. Taken together, TolCV1 plays key roles in RtxA1 secretion, bile salt resistance, and mice lethality of V. vulnificus, suggesting that TolCV1 could be an attractive target for the design of new medicines to treat V. vulnificus infections.
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Affiliation(s)
- Yue Gong
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Rui Hong Guo
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Joon Haeng Rhee
- Clinical Vaccine R&D Center, Department of Microbiology, Combinatorial Tumor Immunotherapy MRC, Chonnam National University Medical School, Hwasun-gun, South Korea
| | - Young Ran Kim
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
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Shivappagowdar A, Garg S, Srivastava A, Hada RS, Kalia I, Singh AP, Garg LC, Pati S, Singh S. Pathogenic Pore Forming Proteins of Plasmodium Triggers the Necrosis of Endothelial Cells Attributed to Malaria Severity. Toxins (Basel) 2021; 13:toxins13010062. [PMID: 33467515 PMCID: PMC7839052 DOI: 10.3390/toxins13010062] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 11/05/2020] [Accepted: 11/08/2020] [Indexed: 11/17/2022] Open
Abstract
Severe malaria caused by Plasmodium falciparum poses a major global health problem with high morbidity and mortality. P. falciparum harbors a family of pore-forming proteins (PFPs), known as perforin like proteins (PLPs), which are structurally equivalent to prokaryotic PFPs. These PLPs are secreted from the parasites and, they contribute to disease pathogenesis by interacting with host cells. The severe malaria pathogenesis is associated with the dysfunction of various barrier cells, including endothelial cells (EC). Several factors, including PLPs secreted by parasites, contribute to the host cell dysfunction. Herein, we have tested the hypothesis that PLPs mediate dysfunction of barrier cells and might have a role in disease pathogenesis. We analyzed various dysfunctions in barrier cells following rPLP2 exposure and demonstrate that it causes an increase in intracellular Ca2+ levels. Additionally, rPLP2 exposed barrier cells displayed features of cell death, including Annexin/PI positivity, depolarized the mitochondrial membrane potential, and ROS generation. We have further performed the time-lapse video microscopy of barrier cells and found that the treatment of rPLP2 triggers their membrane blebbing. The cytoplasmic localization of HMGB1, a marker of necrosis, further confirmed the necrotic type of cell death. This study highlights the role of parasite factor PLP in endothelial dysfunction and provides a rationale for the design of adjunct therapies against severe malaria.
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Affiliation(s)
- Abhishek Shivappagowdar
- Department of Life Science, School of Natural Sciences, Shiv Nadar University, Chithera, Gautam Buddha Nagar, Uttar Pradesh 201314, India; (A.S.); (A.S.); (R.S.H.); (S.P.)
| | - Swati Garg
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India;
| | - Akriti Srivastava
- Department of Life Science, School of Natural Sciences, Shiv Nadar University, Chithera, Gautam Buddha Nagar, Uttar Pradesh 201314, India; (A.S.); (A.S.); (R.S.H.); (S.P.)
| | - Rahul S. Hada
- Department of Life Science, School of Natural Sciences, Shiv Nadar University, Chithera, Gautam Buddha Nagar, Uttar Pradesh 201314, India; (A.S.); (A.S.); (R.S.H.); (S.P.)
| | - Inderjeet Kalia
- Infectious Disease Lab, National Institute of Immunology, New Delhi 110067, India; (I.K.); (A.P.S.)
| | - Agam P. Singh
- Infectious Disease Lab, National Institute of Immunology, New Delhi 110067, India; (I.K.); (A.P.S.)
| | - Lalit C. Garg
- Gene Regulation Laboratory, National Institute of Immunology, New Delhi 110067, India;
| | - Soumya Pati
- Department of Life Science, School of Natural Sciences, Shiv Nadar University, Chithera, Gautam Buddha Nagar, Uttar Pradesh 201314, India; (A.S.); (A.S.); (R.S.H.); (S.P.)
| | - Shailja Singh
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India;
- Correspondence:
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Guo RH, Gong Y, Kim SY, Rhee JH, Kim YR. DIDS inhibits Vibrio vulnificus cytotoxicity by interfering with TolC-mediated RtxA1 toxin secretion. Eur J Pharmacol 2020; 884:173407. [PMID: 32735984 DOI: 10.1016/j.ejphar.2020.173407] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/10/2020] [Accepted: 07/23/2020] [Indexed: 12/28/2022]
Abstract
Vibrio vulnificus (V. vulnificus) infection, frequently resulting in fatal septicemia, has become a growing health concern worldwide. The present study aimed to explore the potential agents that could protect against V. vulnificus cytotoxicity, and to analyze the possible underlying mechanisms. First, we observed that 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid disodium salt hydrate (DIDS) significantly suppressed V. vulnificus cytotoxicity to host cells by using a lactate dehydrogenase (LDH) assay. DIDS did not exhibit any effect on host cell viability, bacterial growth, microbial adhesion and swarming motility. DIDS effectively lowered V. vulnificus RtxA1 toxin-induced calcium influx into host mitochondria and RtxA1 binding to host cells. To further elucidate the underlying mechanism, the synthesis and secretion of RtxA1 toxin were investigated by Western blotting. Intriguingly, DIDS selectively inhibited the secretion of RtxA1 toxin, but did not influence its synthesis. Consequently, the outer membrane portal TolC, a key conduit for RtxA1 export coupled with tripartite efflux pumps, was examined by RT-PCR and Western blotting. We found that DIDS significantly reduced the expression of TolCV1 protein at the transcriptional level. Taken together, these results suggest that DIDS is a promising new paradigm as an antimicrobial drug that targets TolC-mediated toxin.
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Affiliation(s)
- Rui Hong Guo
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Republic of Korea
| | - Yue Gong
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Republic of Korea
| | - Soo Young Kim
- Clinical Vaccine R&D Center and Department of Microbiology, Chonnam National University Medical School, Republic of Korea
| | - Joon Haeng Rhee
- Clinical Vaccine R&D Center and Department of Microbiology, Chonnam National University Medical School, Republic of Korea
| | - Young Ran Kim
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Republic of Korea.
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11
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Guo RH, Im YJ, Shin SI, Jeong K, Rhee JH, Kim YR. Vibrio vulnificus RtxA1 cytotoxin targets filamin A to regulate PAK1- and MAPK-dependent cytoskeleton reorganization and cell death. Emerg Microbes Infect 2019; 8:934-945. [PMID: 31237474 PMCID: PMC6598492 DOI: 10.1080/22221751.2019.1632153] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cytoskeletal rearrangement and acute cytotoxicity occur in Vibrio vulnificus-infected host cells. RtxA1 toxin, a multifunctional autoprocessing repeats-in-toxin (MARTX), is essential for the pathogenesis of V. vulnificus and the programmed necrotic cell death. In this study, HeLa cells expressing RtxA1 amino acids 1491–1971 fused to GFP were observed to be rounded. Through yeast two-hybrid screening and subsequent immunoprecipitation validation assays, we confirmed the specific binding of a RtxA11491–1971 fragment with host-cell filamin A, an actin cross-linking scaffold protein. Downregulation of filamin A expression decreased the cytotoxicity of RtxA1 toward host cells. Furthermore, the phosphorylation of JNK and p38 MAPKs was induced by the RtxA1-filamin A interaction during the toxin-mediated cell death. However, the phosphorylation of these MAPKs was not observed during the RtxA1 intoxication of filamin A-deficient M2 cells. In addition, the depletion of pak1, which appeared to be activated by the RtxA1-filamin A interaction, inhibited RtxA1-induced phosphorylation of JNK and p38, and the cells treated with a pak1 inhibitor exhibited decreased RtxA1-mediated cytoskeletal rearrangement and cytotoxicity. Thus, the binding of filamin A by the RtxA11491–1971 domain appears to be a requisite to pak1-mediated MAPK activation, which contributes to the cytoskeletal reorganization and host cell death.
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Affiliation(s)
- Rui Hong Guo
- a College of Pharmacy and Research Institute of Drug Development , Chonnam National University , Gwangju , Republic of Korea
| | - Young Jun Im
- a College of Pharmacy and Research Institute of Drug Development , Chonnam National University , Gwangju , Republic of Korea
| | - Soo Im Shin
- c Department of Bioengineering and Biotechnology, College of Engineering , Chonnam National University , Gwangju , Republic of Korea
| | - Kwangjoon Jeong
- b Clinical Vaccine R&D Center and Department of Microbiology , Chonnam National University Medical School , Hwasun , Republic of Korea
| | - Joon Haeng Rhee
- b Clinical Vaccine R&D Center and Department of Microbiology , Chonnam National University Medical School , Hwasun , Republic of Korea
| | - Young Ran Kim
- a College of Pharmacy and Research Institute of Drug Development , Chonnam National University , Gwangju , Republic of Korea
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12
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Duong-Nu TM, Jeong K, Hong SH, Puth S, Kim SY, Tan W, Lee KH, Lee SE, Rhee JH. A stealth adhesion factor contributes to Vibrio vulnificus pathogenicity: Flp pili play roles in host invasion, survival in the blood stream and resistance to complement activation. PLoS Pathog 2019; 15:e1007767. [PMID: 31437245 PMCID: PMC6748444 DOI: 10.1371/journal.ppat.1007767] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 09/17/2019] [Accepted: 07/19/2019] [Indexed: 02/06/2023] Open
Abstract
The tad operons encode the machinery required for adhesive Flp (fimbrial low-molecular-weight protein) pili biogenesis. Vibrio vulnificus, an opportunistic pathogen, harbors three distinct tad loci. Among them, only tad1 locus was highly upregulated in in vivo growing bacteria compared to in vitro culture condition. To understand the pathogenic roles of the three tad loci during infection, we constructed single, double and triple tad loci deletion mutants. Interestingly, only the Δtad123 triple mutant cells exhibited significantly decreased lethality in mice. Ultrastructural observations revealed short, thin filamentous projections disappeared on the Δtad123 mutant cells. Since the pilin was paradoxically non-immunogenic, a V5 tag was fused to Flp to visualize the pilin protein by using immunogold EM and immunofluorescence microscopy. The Δtad123 mutant cells showed attenuated host cell adhesion, decreased biofilm formation, delayed RtxA1 exotoxin secretion and subsequently impaired translocation across the intestinal epithelium compared to wild type, which could be partially complemented with each wild type operon. The Δtad123 mutant was susceptible to complement-mediated bacteriolysis, predominantly via the alternative pathway, suggesting stealth hiding role of the Tad pili. Complement depletion by treating with anti-C5 antibody rescued the viable count of Δtad123 in infected mouse bloodstream to the level comparable to wild type strain. Taken together, all three tad loci cooperate to confer successful invasion of V. vulnificus into deeper tissue and evasion from host defense mechanisms, ultimately resulting in septicemia.
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Affiliation(s)
- Tra-My Duong-Nu
- Department of Microbiology, Chonnam National University Medical School, Hwasun-gun, Jeonnam, Republic of Korea
- Clinical Vaccine R&D Center, Chonnam National University, Hwasun-gun, Jeonnam, Republic of Korea
| | - Kwangjoon Jeong
- Department of Microbiology, Chonnam National University Medical School, Hwasun-gun, Jeonnam, Republic of Korea
- Clinical Vaccine R&D Center, Chonnam National University, Hwasun-gun, Jeonnam, Republic of Korea
| | - Seol Hee Hong
- Clinical Vaccine R&D Center, Chonnam National University, Hwasun-gun, Jeonnam, Republic of Korea
- Department of Pharmacology and Dental Therapeutics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea
| | - Sao Puth
- Department of Microbiology, Chonnam National University Medical School, Hwasun-gun, Jeonnam, Republic of Korea
- Clinical Vaccine R&D Center, Chonnam National University, Hwasun-gun, Jeonnam, Republic of Korea
- Combinatorial Tumor Immunotherapy MRC, Chonnam National University Medical School, Hwasun-gun, Jeonnam, Republic of Korea
| | - Soo Young Kim
- Department of Microbiology, Chonnam National University Medical School, Hwasun-gun, Jeonnam, Republic of Korea
- Clinical Vaccine R&D Center, Chonnam National University, Hwasun-gun, Jeonnam, Republic of Korea
| | - Wenzhi Tan
- Department of Microbiology, Chonnam National University Medical School, Hwasun-gun, Jeonnam, Republic of Korea
- Clinical Vaccine R&D Center, Chonnam National University, Hwasun-gun, Jeonnam, Republic of Korea
| | - Kwang Ho Lee
- Center for Research Facilities, Chonnam National University, Gwangju, Republic of Korea
| | - Shee Eun Lee
- Clinical Vaccine R&D Center, Chonnam National University, Hwasun-gun, Jeonnam, Republic of Korea
- Department of Pharmacology and Dental Therapeutics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea
| | - Joon Haeng Rhee
- Department of Microbiology, Chonnam National University Medical School, Hwasun-gun, Jeonnam, Republic of Korea
- Clinical Vaccine R&D Center, Chonnam National University, Hwasun-gun, Jeonnam, Republic of Korea
- Department of Pharmacology and Dental Therapeutics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea
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13
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Gavin HE, Satchell KJF. RRSP and RID Effector Domains Dominate the Virulence Impact of Vibrio vulnificus MARTX Toxin. J Infect Dis 2019; 219:889-897. [PMID: 30289477 PMCID: PMC6386806 DOI: 10.1093/infdis/jiy590] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Accepted: 10/04/2018] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The bacterial pathogen Vibrio vulnificus causes severe septic foodborne infections. The multifunctional autoprocessing repeats-in-toxins (MARTX) toxin is an important secreted virulence factor. The effector domain region is essential for lethal intestinal infection in mice, but the contribution of each of the 5 effector domains to infection has not been investigated. METHODS V. vulnificus mutants with varying effector domain content were inoculated intragastrically to mice, and the time to death was monitored to establish the contribution of each effector domain to overall virulence. Each strain was also tested for bacterial dissemination from the intestine to internal organs and for inhibition of phagocytosis. RESULTS The effector domain region was required for V. vulnificus to inhibit phagocytosis by J774 macrophages, but no single effector domain was required. No single MARTX effector domain was necessary for bacterial dissemination. Nonetheless, overall survival of infected mice differed with respect to the infecting V. vulnificus strain. Removal of rid or rrsp significantly reduced the virulence potential of V. vulnificus, while deletion of duf1 or abh accelerated the time to death. CONCLUSION Rho GTPases inactivation domain and Ras/Rap1-specific endopeptidase each exert greater effects on virulence than other MARTX domains, suggesting that modulation of the Rho/Ras family of GTPases is a critical function of the toxin during intestinal infection.
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Affiliation(s)
- Hannah E Gavin
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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14
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Kim BS. The Modes of Action of MARTX Toxin Effector Domains. Toxins (Basel) 2018; 10:toxins10120507. [PMID: 30513802 PMCID: PMC6315884 DOI: 10.3390/toxins10120507] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 11/20/2018] [Accepted: 11/27/2018] [Indexed: 12/26/2022] Open
Abstract
Many Gram-negative bacterial pathogens directly deliver numerous effector proteins from the bacterium to the host cell, thereby altering the target cell physiology. The already well-characterized effector delivery systems are type III, type IV, and type VI secretion systems. Multifunctional autoprocessing repeats-in-toxin (MARTX) toxins are another effector delivery platform employed by some genera of Gram-negative bacteria. These single polypeptide exotoxins possess up to five effector domains in a modular fashion in their central regions. Upon binding to the host cell plasma membrane, MARTX toxins form a pore using amino- and carboxyl-terminal repeat-containing arms and translocate the effector domains into the cells. Consequently, MARTX toxins affect the integrity of the host cells and often induce cell death. Thus, they have been characterized as crucial virulence factors of certain human pathogens. This review covers how each of the MARTX toxin effector domains exhibits cytopathic and/or cytotoxic activities in cells, with their structural features revealed recently. In addition, future directions for the comprehensive understanding of MARTX toxin-mediated pathogenesis are discussed.
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Affiliation(s)
- Byoung Sik Kim
- Department of Food Science and Engineering, ELTEC College of Engineering, Ewha Womans University, Seoul 03760, Korea.
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15
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Guo RH, Lim JY, Tra My DN, Jo SJ, Park JU, Rhee JH, Kim YR. Vibrio vulnificus RtxA1 Toxin Expression Upon Contact With Host Cells Is RpoS-Dependent. Front Cell Infect Microbiol 2018; 8:70. [PMID: 29600196 PMCID: PMC5862816 DOI: 10.3389/fcimb.2018.00070] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 02/27/2018] [Indexed: 12/18/2022] Open
Abstract
The expression of virulence genes in bacteria is known to be regulated by various environmental and host factors. Vibrio vulnificus, an estuarine bacterium, experiences a dramatic environmental change during its infection process. We reported that V. vulnificus RtxA1 toxin caused acute cell death only when close contact to host cells was allowed. A sigma factor RpoS is a very important regulator for the maximal survival of pathogens under stress conditions. Here, we studied the role of RpoS in V. vulnificus cytotoxicity and mouse lethality. The growth of rpoS mutant strain was comparable to that of wild-type in heart infusion (HI) media and DMEM with HeLa cell lysate. An rpoS mutation resulted in decreased cytotoxicity, which was restored by in trans complementation. Interestingly, host contact increased the expression and secretion of V. vulnificus RtxA1 toxin, which was decreased and delayed by the rpoS mutation. Transcription of the cytotoxic gene rtxA1 and its transporter rtxB1 was significantly increased after host factor contact, whereas the activity was decreased by the rpoS mutation. In contrast, the rpoS mutation showed no effect on the transcriptional activity of a cytolytic heamolysin gene (vvhA). Additionally, the LD50 of the rpoS mutant was 15-fold higher than that of the wild-type in specific pathogen-free CD-1 female mice. Taken together, these results show that RpoS regulates the expression of V. vulnificus RtxA1 toxin and its transporter upon host contact.
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Affiliation(s)
- Rui Hong Guo
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Ju Young Lim
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Duong Nu Tra My
- Department of Molecular Medicine, Chonnam National University, Gwangju, South Korea
| | - Se Jin Jo
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Jung Up Park
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Joon Haeng Rhee
- Department of Microbiology, Clinical Vaccine R&D Center, Chonnam National University Medical School, Gwangju, South Korea
| | - Young Ran Kim
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
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16
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Woida PJ, Satchell KJF. Coordinated delivery and function of bacterial MARTX toxin effectors. Mol Microbiol 2017; 107:133-141. [PMID: 29114985 DOI: 10.1111/mmi.13875] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2017] [Indexed: 12/22/2022]
Abstract
Bacteria often coordinate virulence factors to fine-tune the host response during infection. These coordinated events can include toxins counteracting or amplifying effects of another toxin or though regulating the stability of virulence factors to remove their function once it is no longer needed. Multifunctional autoprocessing repeats-in toxin (MARTX) toxins are effector delivery toxins that form a pore into the plasma membrane of a eukaryotic cell to deliver multiple effector proteins into the cytosol of the target cell. The function of these proteins includes manipulating actin cytoskeletal dynamics, regulating signal transduction pathways and inhibiting host secretory pathways. Investigations into the molecular mechanisms of these effector domains are providing insight into how the function of some effectors overlap and regulate one another during infection. Coordinated crosstalk of effector function suggests that MARTX toxins are not simply a sum of all their parts. Instead, modulation of cell function by effector domains may depend on which other effector domain are co-delivered. Future studies will elucidate how these effectors interact with each other to modulate the bacterial host interaction.
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Affiliation(s)
- Patrick J Woida
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
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17
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Jang KK, Lee ZW, Kim B, Jung YH, Han HJ, Kim MH, Kim BS, Choi SH. Identification and characterization of Vibrio vulnificus plpA encoding a phospholipase A 2 essential for pathogenesis. J Biol Chem 2017; 292:17129-17143. [PMID: 28855258 DOI: 10.1074/jbc.m117.791657] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 08/28/2017] [Indexed: 12/23/2022] Open
Abstract
The marine bacterium Vibrio vulnificus causes food-borne diseases, which may lead to life-threatening septicemia in some individuals. Therefore, identifying virulence factors in V. vulnificus is of high priority. We performed a transcriptome analysis on V. vulnificus after infection of human intestinal HT29-methotrexate cells and found induction of plpA, encoding a putative phospholipase, VvPlpA. Bioinformatics, biochemical, and genetic analyses demonstrated that VvPlpA is a phospholipase A2 secreted in a type II secretion system-dependent manner. Compared with the wild type, the plpA mutant exhibited reduced mortality, systemic infection, and inflammation in mice as well as low cytotoxicity toward the human epithelial INT-407 cells. Moreover, plpA mutation attenuated the release of actin and cytosolic cyclophilin A from INT-407 cells, indicating that VvPlpA is a virulence factor essential for causing lysis and necrotic death of the epithelial cells. plpA transcription was growth phase-dependent, reaching maximum levels during the early stationary phase. Also, transcription factor HlyU and cAMP receptor protein (CRP) mediate additive activation and host-dependent induction of plpA Molecular biological analyses revealed that plpA expression is controlled via the promoter, P plpA , and that HlyU and CRP directly bind to P plpA upstream sequences. Taken together, this study demonstrated that VvPlpA is a type II secretion system-dependent secretory phospholipase A2 regulated by HlyU and CRP and is essential for the pathogenicity of V. vulnificus.
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Affiliation(s)
- Kyung Ku Jang
- From the National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, and
| | - Zee-Won Lee
- From the National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, and
| | - Bityeoul Kim
- From the National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, and
| | - Young Hyun Jung
- the Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Medicine, BK21 PLUS Creative Veterinary Research Center, Seoul National University, Seoul 08826, South Korea and
| | - Ho Jae Han
- the Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Medicine, BK21 PLUS Creative Veterinary Research Center, Seoul National University, Seoul 08826, South Korea and
| | - Myung Hee Kim
- the Infection and Immunity Research Laboratory, Metabolic Regulation Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, South Korea
| | - Byoung Sik Kim
- the Infection and Immunity Research Laboratory, Metabolic Regulation Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, South Korea
| | - Sang Ho Choi
- From the National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, and
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18
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Lee SJ, Jung YH, Kim JS, Lee HJ, Lee SH, Lee KH, Jang KK, Choi SH, Han HJ. A Vibrio vulnificus VvpM Induces IL-1β Production Coupled with Necrotic Macrophage Death via Distinct Spatial Targeting by ANXA2. Front Cell Infect Microbiol 2017; 7:352. [PMID: 28848713 PMCID: PMC5554522 DOI: 10.3389/fcimb.2017.00352] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 07/21/2017] [Indexed: 12/23/2022] Open
Abstract
An inflammatory form of phagocyte death evoked by the Gram-negative bacterium Vibrio (V.) vulnificus (WT) is one of hallmarks to promote their colonization, but the virulence factor and infectious mechanism involved in this process remain largely unknown. Here, we identified extracellular metalloprotease VvpM as a new virulence factor and investigated the molecular mechanism of VvpM which acts during the regulation of the inflammatory form of macrophage death and bacterial colonization. Mutation of the vvpM gene appeared to play major role in the prevention of IL-1β production due to V. vulnificus infection in macrophage. However, the recombinant protein (r) VvpM caused IL-1β production coupled with necrotic cell death, which is highly susceptible to the knockdown of annexin A2 (ANXA2) located in both membrane lipid and non-lipid rafts. In lipid rafts, rVvpM recruited NOX enzymes coupled with ANXA2 to facilitate the production of ROS responsible for the epigenetic and transcriptional regulation of NF-κB in the IL-1β promoter. rVvpM acting on non-lipid rafts increased LC3 puncta formation and autophagic flux, which are required for the mRNA expression of Atg5 involved in the autophagosome formation process. The autophagy activation caused by rVvpM induced NLRP3 inflammasome-dependent caspase-1 activation in the promoting of IL-1β production. In mouse models of V. vulnificus infection, the VvpM mutant failed to elevate the level of pro-inflammatory responses closely related to IL-1β production and prevented bacterial colonization. These findings delineate VvpM efficiently regulates two pathogenic pathways that stimulate NF-κB-dependent IL-1β production and autophagy-mediated NLRP3 inflammasome via distinct spatial targeting by ANXA2.
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Affiliation(s)
- Sei-Jung Lee
- Department of Pharmaceutical Engineering, Daegu Haany UniversityGyeongsan, South Korea
| | - Young Hyun Jung
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National UniversitySeoul, South Korea
| | - Jun Sung Kim
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National UniversitySeoul, South Korea
| | - Hyun Jik Lee
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National UniversitySeoul, South Korea
| | - Sang Hun Lee
- Medical Science Research Institute, Soonchunhyang University Seoul HospitalSeoul, South Korea
- Departments of Biochemistry, Soonchunhyang University College of MedicineCheonan, South Korea
| | - Kyu-Ho Lee
- Department of Life Science, Sogang UniversitySeoul, South Korea
| | - Kyung Ku Jang
- National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Seoul National UniversitySeoul, South Korea
| | - Sang Ho Choi
- National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Seoul National UniversitySeoul, South Korea
| | - Ho Jae Han
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Science and BK21 PLUS Program for Creative Veterinary Science Research Center, Seoul National UniversitySeoul, South Korea
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19
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Variable Virulence of Biotype 3 Vibrio vulnificus due to MARTX Toxin Effector Domain Composition. mSphere 2017; 2:mSphere00272-17. [PMID: 28815212 PMCID: PMC5555677 DOI: 10.1128/mspheredirect.00272-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 07/07/2017] [Indexed: 01/22/2023] Open
Abstract
Vibrio vulnificus is an environmental organism that causes septic human infections characterized by high morbidity and mortality. The annual incidence and global distribution of this pathogen are increasing as ocean waters warm. Clinical strains exhibit variations in the primary virulence toxin, suggesting a potential for the emergence of new strains with altered virulence properties. A clonal outbreak of tilapia-associated wound infections in Israel serves as a natural experiment for the sudden emergence of a new V. vulnificus strain. The effector domain content of the multifunctional autoprocessing RTX (MARTX) toxin of the outbreak-associated biotype 3 (BT3) strains was previously shown to harbor a modification generated by recombination. The modification introduced an actin-induced adenylate cyclase effector domain (ExoY) and an effector domain that disrupts the Golgi organelle (DmX). Here, we report that the exchange of these effector domains for a putative progenitor biotype 1 toxin arrangement produces a toxin that slows the lysis kinetics of targeted epithelial cells but increases cellular rounding phenotypes in response to bacteria. In addition, replacing the biotype 3 toxin variant with the putative progenitor biotype 1 variant renders the resulting strain significantly more virulent in mice. This suggests that the exchange of MARTX effector domains during the emergence of BT3 generated a toxin with reduced toxin potency, resulting in decreased virulence of this outbreak-associated strain. We posit that selection for reduced virulence may serve as a route for this lethal infectious agent to enter the human food chain by allowing it to persist in natural hosts. IMPORTANCEVibrio vulnificus is a serious infection linked to climate change. The virulence capacity of these bacteria can vary by gene exchange, resulting in new variants of the primary virulence toxin. In this study, we tested whether the emergence of an epidemic strain of V. vulnificus with a novel toxin variant correlated with a change in virulence. We found that restoring the biotype 3 toxin variant to the putative progenitor-type toxin resulted in dramatically increased virulence, revealing that the emergence of the biotype 3 strain could be linked to virulence reduction. This reduced virulence, previously found also in the biotype 1 strain, suggests that reduced virulence may stimulate outbreaks, as strains have greater capacity to enter the human food chain through reduced impact to environmental hosts.
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20
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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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21
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Gavin HE, Beubier NT, Satchell KJF. The Effector Domain Region of the Vibrio vulnificus MARTX Toxin Confers Biphasic Epithelial Barrier Disruption and Is Essential for Systemic Spread from the Intestine. PLoS Pathog 2017; 13:e1006119. [PMID: 28060924 PMCID: PMC5218395 DOI: 10.1371/journal.ppat.1006119] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 12/12/2016] [Indexed: 12/14/2022] Open
Abstract
Vibrio vulnificus causes highly lethal bacterial infections in which the Multifunctional Autoprocessing Repeats-in-Toxins (MARTX) toxin product of the rtxA1 gene is a key virulence factor. MARTX toxins are secreted proteins up to 5208 amino acids in size. Conserved MARTX N- and C-terminal repeat regions work in concert to form pores in eukaryotic cell membranes, through which the toxin's central region of modular effector domains is translocated. Upon inositol hexakisphosphate-induced activation of the of the MARTX cysteine protease domain (CPD) in the eukaryotic cytosol, effector domains are released from the holotoxin by autoproteolytic activity. We previously reported that the native MARTX toxin effector domain repertoire is dispensable for epithelial cellular necrosis in vitro, but essential for cell rounding and apoptosis prior to necrotic cell death. Here we use an intragastric mouse model to demonstrate that the effector domain region is required for bacterial virulence during intragastric infection. The MARTX effector domain region is essential for bacterial dissemination from the intestine, but dissemination occurs in the absence of overt intestinal tissue pathology. We employ an in vitro model of V. vulnificus interaction with polarized colonic epithelial cells to show that the MARTX effector domain region induces rapid intestinal barrier dysfunction and increased paracellular permeability prior to onset of cell lysis. Together, these results negate the inherent assumption that observations of necrosis in vitro directly predict bacterial virulence, and indicate a paradigm shift in our conceptual understanding of MARTX toxin function during intestinal infection. Results implicate the MARTX effector domain region in mediating early bacterial dissemination from the intestine to distal organs-a key step in V. vulnificus foodborne pathogenesis-even before onset of overt intestinal pathology.
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Affiliation(s)
- Hannah E. Gavin
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States of America
| | - Nike T. Beubier
- Department of Pathology, Northwestern University Feinberg School of Medicine and Northwestern Memorial Hospital, Chicago, IL, United States of America
| | - Karla J. F. Satchell
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States of America
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Lim JY, Kim CM, Rhee JH, Kim YR. Effects of Pyrogallol on Growth and Cytotoxicity of Wild-Type and katG Mutant Strains of Vibrio vulnificus. PLoS One 2016; 11:e0167699. [PMID: 27936080 PMCID: PMC5147952 DOI: 10.1371/journal.pone.0167699] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 11/18/2016] [Indexed: 12/05/2022] Open
Abstract
Vibrio vulnificus is a causative agent of fatal septicemia and necrotic wound infection and the pathogen infection became an important public health problem in many counties. Vibrio vulnificus causes RtxA1 toxin-induced acute cell death. We tried to identify natural products that inhibit the acute cytotoxicity of V. vulnificus using a lactate hydrogenase assay. A polyphenol pyrogallol protected HeLa cells from V. vulnificus-induced cytotoxicity. Pyrogallol also decreased the growth of V. vulnificus; this inhibitory effect was more significant during log phase than stationary phase. To further elucidate the inhibitory mechanism, pyrogallol-induced toxicity was compared between a V. vulnificus catalase-peroxidase mutant (katG−) and the isogenic wild-type MO6-24/O strains. No growth was observed for the katG− mutant in the presence of pyrogallol (50 μg/mL) even after 24 h, whereas the wild-type strain demonstrated growth recovery following a prolonged lag phase. Pyrogallol-mediated growth inhibition of the katG− mutant strain was partially rescued by exogenous catalase treatment. These results indicate that the mechanism by which pyrogallol inhibits the growth and cytotoxicity of V. vulnificus likely involves polyphenol-induced prooxidant damage. Taken together, these results suggest that pyrogallol has potential for development as a new paradigm drug to treat infectious diseases.
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Affiliation(s)
- Ju Young Lim
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Chonnam National University, Gwangju, Republic of Korea
| | - Choon-Mee Kim
- Premedical Sciences, Chosun University Medical School, Gwangju, Republic of Korea
| | - Joon Haeng Rhee
- Clinical Vaccine Research and Development Center, Department of Microbiology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Young Ran Kim
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Chonnam National University, Gwangju, Republic of Korea
- * E-mail:
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Abstract
Multifunctional-autoprocessing repeats-in-toxin (MARTX) toxins are a heterogeneous group of toxins found in a number of Vibrio species and other Gram-negative bacteria. The toxins are composed of conserved repeat regions and an autoprocessing protease domain that together function as a delivery platform for transfer of cytotoxic and cytopathic domains into target eukaryotic cell cytosol. Within the cells, the effectors can alter biological processes such as signaling or cytoskeletal structure, presumably to the benefit of the bacterium. Ten effector domains are found in the various Vibrio MARTX toxins, although any one toxin carries only two to five effector domains. The specific toxin variant expressed by a species can be modified by homologous recombination to acquire or lose effector domains, such that different strains within the same species can express distinct variants of the toxins. This review examines the conserved structural elements of the MARTX toxins and details the different toxin arrangements carried by Vibrio species and strains. The catalytic function of domains and how the toxins are linked to pathogenesis of human and animals is described.
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All Three TonB Systems Are Required for Vibrio vulnificus CMCP6 Tissue Invasiveness by Controlling Flagellum Expression. Infect Immun 2015; 84:254-65. [PMID: 26527216 DOI: 10.1128/iai.00821-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 10/24/2015] [Indexed: 01/22/2023] Open
Abstract
TonB systems actively transport iron-bound substrates across the outer membranes of Gram-negative bacteria. Vibrio vulnificus CMCP6, which causes fatal septicemia and necrotizing wound infections, possesses three active TonB systems. It is not known why V. vulnificus CMCP6 has maintained three TonB systems throughout its evolution. The TonB1 and TonB2 systems are relatively well characterized, while the pathophysiological function of the TonB3 system is still elusive. A reverse transcription-PCR (RT-PCR) study showed that the tonB1 and tonB2 genes are preferentially induced in vivo, whereas tonB3 is persistently transcribed, albeit at low expression levels, under both in vitro and in vivo conditions. The goal of the present study was to elucidate the raison d'être of these three TonB systems. In contrast to previous studies, we constructed in-frame single-, double-, and triple-deletion mutants of the entire structural genes in TonB loci, and the changes in various virulence-related phenotypes were evaluated. Surprisingly, only the tonB123 mutant exhibited a significant delay in killing eukaryotic cells, which was complemented in trans with any TonB operon. Very interestingly, we discovered that flagellum biogenesis was defective in the tonB123 mutant. The loss of flagellation contributed to severe defects in motility and adhesion of the mutant. Because of the difficulty of making contact with host cells, the mutant manifested defective RtxA1 toxin production, which resulted in impaired invasiveness, delayed cytotoxicity, and decreased lethality for mice. Taken together, these results indicate that a series of virulence defects in all three TonB systems of V. vulnificus CMCP6 coordinately complement each other for iron assimilation and full virulence expression by ensuring flagellar biogenesis.
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Gavin HE, Satchell KJF. MARTX toxins as effector delivery platforms. Pathog Dis 2015; 73:ftv092. [PMID: 26472741 DOI: 10.1093/femspd/ftv092] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/07/2015] [Indexed: 12/14/2022] Open
Abstract
Bacteria frequently manipulate their host environment via delivery of microbial 'effector' proteins to the cytosol of eukaryotic cells. In the case of the multifunctional autoprocessing repeats-in-toxins (MARTX) toxin, this phenomenon is accomplished by a single, >3500 amino acid polypeptide that carries information for secretion, translocation, autoprocessing and effector activity. MARTX toxins are secreted from bacteria by dedicated Type I secretion systems. The released MARTX toxins form pores in target eukaryotic cell membranes for the delivery of up to five cytopathic effectors, each of which disrupts a key cellular process. Targeted cellular processes include modulation or modification of small GTPases, manipulation of host cell signaling and disruption of cytoskeletal integrity. More recently, MARTX toxins have been shown to be capable of heterologous protein translocation. Found across multiple bacterial species and genera--frequently in pathogens lacking Type 3 or Type 4 secretion systems--MARTX toxins in multiple cases function as virulence factors. Innovative research at the intersection of toxin biology and bacterial genetics continues to elucidate the intricacies of the toxin as well as the cytotoxic mechanisms of its diverse effector collection.
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Affiliation(s)
- Hannah E Gavin
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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26
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Kim YR, Lee SE, Kim JR, Rhee JH. Safety and vaccine efficacy of an attenuated Vibrio vulnificus strain with deletions in major cytotoxin genes. FEMS Microbiol Lett 2015; 362:fnv169. [PMID: 26381905 DOI: 10.1093/femsle/fnv169] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2015] [Indexed: 11/12/2022] Open
Abstract
Vibrio vulnificus is a human pathogen causing a rapidly progressing fatal septicemia. We have previously reported that a V. vulnificus large toxin RtxA1 causes programmed necrotic cell death through calcium-mediated mitochondrial dysfunction. Here we developed a live attenuated vaccine strain (CMM781) having deletions in three genes encoding major virulence factors: RTX cytotoxin (rtxA1), hemolysin/cytolysin (vvhA) and metalloprotease (vvpE) of a clinical isolate strain CMCP6. The CMM781 strain showed significant attenuation in cytotoxicity and mouse lethality. The safety of CMM781 was also confirmed by measuring the transepithelial electric resistance of Caco-2 cell monolayers. Intragastric immunization of mice with the live attenuated V. vulnificus strain resulted in induction of systemic and mucosal antibodies specific to the pathogen. Moreover, the vaccinated mice were protected from challenges with high doses of the virulent strain through various injection routes. These results suggest that CMM781 appears to be a safe and effective vaccine candidate that would provide significant protection against V. vulnificus infection.
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Affiliation(s)
- Young Ran Kim
- Clinical Vaccine R&D Center, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun 519-763, Korea College of Pharmacy, Chonnam National University, Gwangju 500-757, Korea
| | - Shee Eun Lee
- Clinical Vaccine R&D Center, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun 519-763, Korea Department of Pharmacology and Dental Therapeutics, Dental Research Institute, Chonnam National University, Gwangju 500-757, Korea
| | - Jong Ro Kim
- Busung Food and Business, Jangheung, Jeonnam 529-873, Korea
| | - Joon Haeng Rhee
- Clinical Vaccine R&D Center, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun 519-763, Korea Research Institute of Vibrio Infections and Genome Research Center for Enteropathogenic Bacteria, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun 519-763, Korea Department of Microbiology, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun 519-763, Korea
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The Makes Caterpillars Floppy (MCF)-Like Domain of Vibrio vulnificus Induces Mitochondrion-Mediated Apoptosis. Infect Immun 2015; 83:4392-403. [PMID: 26351282 DOI: 10.1128/iai.00570-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Accepted: 08/26/2015] [Indexed: 12/17/2022] Open
Abstract
The multifunctional-autoprocessing repeats-in-toxin (MARTXVv) toxin of Vibrio vulnificus plays a significant role in the pathogenesis of this bacterium through delivery of up to five effector domains to the host cells. Previous studies have established that the MARTXVv toxin is linked to V. vulnificus dependent induction of apoptosis, but the region of the large multifunction protein essential for this activity was not previously identified. Recently, we showed that the Makes Caterpillar Floppy-like MARTX effector domain (MCFVv) is an autoproteolytic cysteine protease that induces rounding of various cell types. In this study, we demonstrate that cell rounding induced by MCFVv is coupled to reduced metabolic rate and inhibition of cellular proliferation. Moreover, delivery of MCFVv into host cells either as a fusion to the N-terminal fragment of anthrax toxin lethal factor or when naturally delivered as a V. vulnificus MARTX toxin led to loss of mitochondrial membrane potential, release of cytochrome c, activation of Bax and Bak, and processing of caspases and poly-(ADP-ribose) polymerase (PARP-γ). These studies specifically link the MCFVv effector domain to induction of the intrinsic apoptosis pathway by V. vulnificus.
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28
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Extracellular Ca2+-dependent enhancement of cytocidal potency of zoledronic acid in human oral cancer cells. Eur J Pharmacol 2015; 761:44-54. [DOI: 10.1016/j.ejphar.2015.04.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 03/28/2015] [Accepted: 04/01/2015] [Indexed: 11/20/2022]
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Callol A, Reyes-López FE, Roig FJ, Goetz G, Goetz FW, Amaro C, MacKenzie SA. An Enriched European Eel Transcriptome Sheds Light upon Host-Pathogen Interactions with Vibrio vulnificus. PLoS One 2015. [PMID: 26207370 PMCID: PMC4514713 DOI: 10.1371/journal.pone.0133328] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Infectious diseases are one of the principal bottlenecks for the European eel recovery. The aim of this study was to develop a new molecular tool to be used in host-pathogen interaction experiments in the eel. To this end, we first stimulated adult eels with different pathogen-associated molecular patterns (PAMPs), extracted RNA from the immune-related tissues and sequenced the transcriptome. We obtained more than 2x106 reads that were assembled and annotated into 45,067 new descriptions with a notable representation of novel transcripts related with pathogen recognition, signal transduction and the immune response. Then, we designed a DNA-microarray that was used to analyze the early immune response against Vibrio vulnificus, a septicemic pathogen that uses the gills as the portal of entry into the blood, as well as the role of the main toxin of this species (RtxA13) on this early interaction. The gill transcriptomic profiles obtained after bath infecting eels with the wild type strain or with a mutant deficient in rtxA13 were analyzed and compared. Results demonstrate that eels react rapidly and locally against the pathogen and that this immune-response is rtxA13-dependent as transcripts related with cell destruction were highly up-regulated only in the gills from eels infected with the wild-type strain. Furthermore, significant differences in the immune response against the wild type and the mutant strain also suggest that host survival after V. vulnificus infection could depend on an efficient local phagocytic activity. Finally, we also found evidence of the presence of an interbranchial lymphoid tissue in European eel gills although further experiments will be necessary to identify such tissue.
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Affiliation(s)
- Agnès Callol
- Departament de Microbiologia i Ecologia, Universitat de Valencia, Burjassot, Spain
- Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Felipe E. Reyes-López
- Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
- Department de Biologia cel·lular, Fisiologia Animal i Immunologia, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Francisco J. Roig
- Departament de Microbiologia i Ecologia, Universitat de Valencia, Burjassot, Spain
| | - Giles Goetz
- Northwest Fisheries Science Center, Seattle, United States of America
| | | | - Carmen Amaro
- Departament de Microbiologia i Ecologia, Universitat de Valencia, Burjassot, Spain
| | - Simon A. MacKenzie
- Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
- * E-mail:
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30
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Lee TH, Chung KM. Development and characterization of a catalytically inactive cysteine protease domain of RtxA1/MARTXVv as a potential vaccine for Vibrio vulnificus. Microbiol Immunol 2015; 59:555-61. [PMID: 26177798 DOI: 10.1111/1348-0421.12284] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 07/01/2015] [Accepted: 07/12/2015] [Indexed: 01/22/2023]
Abstract
Recent studies have defined several virulence factors as vaccine candidates against Vibrio vulnificus. However, most of these factors have the potential to cause pathogenic effects in the vaccinees or induce incomplete protection. To overcome these drawbacks, a catalytically inactive form, CPDVv (C3725S), of the well-conserved cysteine protease domain (CPD) of V. vulnificus multifunctional autoprocessing repeats-in-toxin (MARTXVv /RtxA1) was recombinantly generated and characterized. Notably, active and passive immunization with CPDVv (C3725S) conferred protective immunity against V. vulnificus strains. These results may provide a novel framework for developing safe and efficient subunit vaccines and/or therapeutics against V. vulnificus that target the CPD of MARTX toxins.
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Affiliation(s)
| | - Kyung Min Chung
- Department of Microbiology and Immunology.,Institute for Medical Science, Chonbuk National University Medical School, Jeonju, Jeonbuk, 561-756, Korea
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Kim BA, Lim JY, Rhee JH, Kim YR. Characterization of Prohibitin 1 as a Host Partner of Vibrio vulnificus RtxA1 Toxin. J Infect Dis 2015; 213:131-8. [PMID: 26136468 DOI: 10.1093/infdis/jiv362] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 06/22/2015] [Indexed: 11/14/2022] Open
Abstract
RtxA1 toxin, which results in cytoskeletal rearrangement, contact cytotoxicity, hemolysis, tissue invasion, and lethality in mice, is the most potent cytotoxic virulence factor of Vibrio vulnificus. Bioinformatics analysis of rtxA1 predicted 4 functional domains that presumably performed discrete functions during host cell killing. V. vulnificus RtxA1 has a unique domain designated as RtxA1-D2, corresponding to amino acids 1951-2574, which is absent in Vibrio cholerae multifunctional-autoprocessing repeats-in-toxin, suggesting that this domain confers specific biological functions to V. vulnificus RtxA1. HeLa cells expressing green fluorescent protein-RtxA1-D2 became round and lost their viability. A yeast 2-hybrid system identified prohibitin (PHB) 1 as the host partner of RtxA1-D2. The specific interaction of RtxA1-D2 with PHB1 was confirmed by performing immunoprecipitation. Interestingly, V. vulnificus RtxA1 up-regulated PHB1 expression on the cytoplasmic membrane of host cells. Extracellular signal-regulated kinase and p38 mitogen-activated protein kinase pathways were confirmed as being important in the up-regulation of PHB1 by using inhibitors. Down-regulation of PHB1 by small interfering RNAs decreased the cytotoxicity of RtxA1-D2 against HeLa cells. The pretreatment of an anti-PHB1 antibody impaired the cytotoxicity of V. vulnificus RtxA1. These results suggest that the involvement PHB1 in the RtxA1 cytotoxicity has significant implications for the pathogenesis of V. vulnificus infections.
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Affiliation(s)
- Bo A Kim
- Clinical Vaccine R&D Center, Chonnam National University Hwasun Hospital, Chonnam National University Medical School
| | - Ju Young Lim
- College of Pharmacy, Chonnam National University, Gwangju, Korea
| | - Joon Haeng Rhee
- Clinical Vaccine R&D Center, Chonnam National University Hwasun Hospital, Chonnam National University Medical School
| | - Young Ran Kim
- College of Pharmacy, Chonnam National University, Gwangju, Korea
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Vibrio vulnificus RtxA1 modulated calcium flux contributes reduced internalization in phagocytes. Life Sci 2015; 132:55-60. [PMID: 25916802 DOI: 10.1016/j.lfs.2015.03.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 03/05/2015] [Accepted: 03/25/2015] [Indexed: 12/17/2022]
Abstract
AIMS Vibrio vulnificusis an opportunistic pathogen that causes primary septicemia and wound infection with high mortality rate. This pathogen produces an RTX toxin (RtxA1) which can cause host cell rounding, cell death and interference with internalization by host phagocytes. However, the mechanism of RtxA1-induced phagocyte paralysis is not clear. MAIN METHODS Using the murine macrophage cell line RAW264.7, we measured cytotoxicity and phagocytosis of V. vulnificusin normal and calcium-depleted media. To deplete extracellular and cytosolic Ca(2+), cells were exposed to the calcium chelators ethylene glycol tetraacetic acid (EGTA) and 1,2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, tetraacetoxymethyl esteris (BAPTA-AM), respectively. The cytotoxicity was examined by measuring the activity of lactate dehydrogenase (LDH) released from the damaged cells. The gentamicin protection assay was conducted to determine the number of internalized bacteria, while acridine orange staining was applied to visualize the intracellular bacteria. The fluorescent indicator fura-2-acetoxymethyl ester (fura 2-AM) was used to measure the Ca(2+)signal post-infection. KEY FINDINGS We revealed that extracellular Ca(2+)was essential for phagocytes to internalize V. vulnificus. Meanwhile, cytosolic Ca(2+)flux in RAW264.7 cells induced by an RtxA1 isogenic mutant was repressed by the parent strain. Furthermore, depletion of extracellular Ca(2+)level by EGTA significantly reduced the cytotoxicity but did not affect the antiphagocytic activity of RtxA1 toxin. SIGNIFICANCE Our results indicated that RtxA1 may interfere with cytosolic Ca(2+)flux of phagocyte to promote bacteria colonization.
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Distinct roles of the repeat-containing regions and effector domains of the Vibrio vulnificus multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin. mBio 2015; 6:mBio.00324-15. [PMID: 25827415 PMCID: PMC4453568 DOI: 10.1128/mbio.00324-15] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Vibrio vulnificus is a seafood-borne pathogen that destroys the intestinal epithelium, leading to rapid bacterial dissemination and death. The most important virulence factor is the multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin comprised of effector domains in the center region flanked by long repeat-containing regions which are well conserved among MARTX toxins and predicted to translocate effector domains. Here, we examined the role of the repeat-containing regions using a modified V. vulnificus MARTX (MARTXVv) toxin generated by replacing all the internal effector domains with β-lactamase (Bla). Bla activity was detected in secretions from the bacterium and also in the cytosol of intoxicated epithelial cells. The modified MARTXVv toxin without effector domains retained its necrotic activity but lost its cell-rounding activity. Further, deletion of the carboxyl-terminal repeat-containing region blocked toxin secretion from the bacterium. Deletion of the amino-terminal repeat-containing region had no effect on secretion but completely abolished translocation and necrosis. Neither secretion nor translocation was affected by enzymatically inactivating the cysteine protease domain of the toxin. These data demonstrate that the amino-terminal and carboxyl-terminal repeat-containing regions of the MARTXVv toxin are necessary and sufficient for the delivery of effector domains and epithelial cell lysis in vitro but that effector domains are required for other cytopathic functions. Furthermore, Ca2+-dependent secretion of the modified MARTXVv toxin suggests that nonclassical RTX-like repeats found in the carboxyl-terminal repeat-containing region are functionally similar to classical RTX repeats found in other RTX proteins. Up to 95% of deaths from seafood-borne infections in the United States are due solely to one pathogen, V. vulnificus. Among its various virulence factors, the MARTXVv toxin has been characterized as a critical exotoxin for successful pathogenesis of V. vulnificus in mouse infection models. Similarly to MARTX toxins of other pathogens, MARTXVv toxin is comprised of repeat-containing regions, central effector domains, and an autoprocessing cysteine protease domain. Yet how each of these regions contributes to essential activities of the toxins has not been fully identified for any of MARTX toxins. Using modified MARTXVv toxin fused with β-lactamase as a reporter enzyme, the portion(s) responsible for toxin secretion from bacteria, effector domain translocation into host cells, rapid host cell rounding, and necrotic host cell death was identified. The results are relevant for understanding how MARTXVv toxin serves as both a necrotic pore-forming toxin and an effector delivery platform.
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Vibrio vulnificus VvhA induces NF-κB-dependent mitochondrial cell death via lipid raft-mediated ROS production in intestinal epithelial cells. Cell Death Dis 2015; 6:1655. [PMID: 25695598 PMCID: PMC4669806 DOI: 10.1038/cddis.2015.19] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 01/07/2015] [Accepted: 01/07/2015] [Indexed: 01/29/2023]
Abstract
The Gram-negative bacterium Vibrio vulnificus produces hemolysin (VvhA), which induces cytotoxicity in mammalian cells. However, our understanding of the cytotoxic mechanism and the modes of action of VvhA are still fragmentary and incomplete. The recombinant protein (r) VvhA (50 pg/ml) significantly induces necrotic cell death and apoptosis in human intestinal epithelial (INT-407) cells. The apoptotic cell death induced by rVvhA is highly susceptible to the sequestration of cholesterol by methyl-β-cyclodextrin, whereas for necrotic cell death, this shows a marginal effect. We found that rVvhA induces the aggregation of lipid raft components coupled with NADPH oxidase enzymes, in which rVvhA increased the interaction of NADPH oxidase 2 (NOX2, gp91phox) with a cytosolic protein NCF1 (p47phox) to facilitate the production of reactive oxygen species (ROS). rVvhA uniquely stimulated a conventional PKC isoform PKCα and induced the phosphorylation of both ERK and JNK, which are responsible for the activation of transcription factor NF-κB. rVvhA induced an NF-κB-dependent imbalance of the Bcl-2/Bax ratio, the release of mitochondrial cytochrome c, and caspase-3/-9 activation during its promotion of apoptotic cell death. In addition, rVvhA has the ability to inhibit the expression of cell cycle-related proteins, such as CDK2, CDK4, cyclin D1, and cyclin E. These results demonstrate that rVvhA induces NF-κB-dependent mitochondrial cell death via lipid raft-mediated ROS production by the distinct activation of PKCα and ERK/JNK in intestinal epithelial cells.
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Monoclonal antibodies against Vibrio vulnificus RtxA1 elicit protective immunity through distinct mechanisms. Infect Immun 2014; 82:4813-23. [PMID: 25156730 DOI: 10.1128/iai.02130-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Vibrio vulnificus causes rapidly progressing septicemia with an extremely high mortality rate (≥50%), even with aggressive antibiotic treatment. The bacteria secrete multifunctional autoprocessing repeats-in-toxin (MARTX) toxins, which are involved in the pathogenesis of Gram-negative Vibrio species. Recently, we reported that immunization with the C-terminal region of V. vulnificus RtxA1/MARTXVv, RtxA1-C, elicits a protective immune response against V. vulnificus through a poorly defined mechanism. In this study, we generated a panel of new monoclonal antibodies (MAbs) against V. vulnificus RtxA1-C and investigated their protective efficacies and mechanisms in a mouse model of infection. Prophylactic administration of seven MAbs strongly protected mice against lethal V. vulnificus infection (more than 90% survival). Moreover, three of these MAbs (21RA, 24RA, and 47RA) demonstrated marked efficacy as postexposure therapy. Notably, 21RA was therapeutically effective against lethal V. vulnificus infection by a variety of routes. Using Fab fragments and a neutropenic mouse model, we showed that 21RA and 24RA mediate protection from V. vulnificus infection through an Fc-independent and/or neutrophil-independent pathway. In contrast, 47RA-mediated protection was dependent on its Fc region and was reduced to 50% in neutropenic mice compared with 21RA-mediated and 24RA-mediated protection. Bacteriological study indicated that 21RA appears to enhance the clearance of V. vulnificus from the blood. Overall, these studies suggest that humoral immunity controls V. vulnificus infection through at least two different mechanisms. Furthermore, our panel of MAbs could provide attractive candidates for the further development of immunoprophylaxis/therapeutics and other therapies against V. vulnificus that target the MARTX toxin.
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In vivo efficacy of the combination of ciprofloxacin and cefotaxime against Vibrio vulnificus sepsis. PLoS One 2014; 9:e101118. [PMID: 24978586 PMCID: PMC4076242 DOI: 10.1371/journal.pone.0101118] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 06/03/2014] [Indexed: 12/18/2022] Open
Abstract
Objectives The invivo efficacy of a cefotaxime-ciprofloxacin combination against Vibrio vulnificus and the effects on rtxA1 expression of commonly used antibiotics are unknown. Methods In vitro time-kill studies were performed to evaluate synergism. Female BALB/c mice were injected subcutaneously with 1×107 or 1×108 cfu of V. vulnificus. Antibiotic therapy was initiated at 2 h after inoculation in the following four therapy groups: cefotaxime; ciprofloxacin; cefotaxime-plus-ciprofloxacin; and cefotaxime-plus-minocycline. The cytotoxicity of V. vulnificus for HeLa cells was measured using the lactate dehydrogenase assay; rtxA1 transcription was measured in a transcriptional reporter strain using a β-galactosidase assay. Results In vitro time-kill assays exhibited synergism between cefotaxime and ciprofloxacin. In the animal experiments, the 96-h survival rate for the cefotaxime-plus-ciprofloxacin group (85%; 17/20) was significantly higher than that of the cefotaxime-plus-minocycline (35%; 7/20) and cefotaxime alone (0%; 0/20) groups (P<0.05 for both). Bacterial counts in the liver and spleen were significantly lower in the cefotaxime-plus-ciprofloxacin group 24 and 48 h after treatment, relative to the other groups. At sub-inhibitory concentrations, ciprofloxacin inhibited more effectively rtxA1 transcription and mammalian cell cytotoxicity than either minocycline or cefotaxime (P<0.05 for both). Conclusions Ciprofloxacin is more effective at reducing rtxA1 transcription and subsequent cytotoxicity than either minocycline or cefotaxime, and the combination of ciprofloxacin and cefotaxime was more effective in clearing V. vulnificus invivo than previously used regimens. These data suggest that the combination of ciprofloxacin and cefotaxime is an effective option for the treatment of V. vulnificus sepsis in humans.
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Lee TH, Kim MH, Lee CS, Lee JH, Rhee JH, Chung KM. Protection against Vibrio vulnificus infection by active and passive immunization with the C-terminal region of the RtxA1/MARTXVv protein. Vaccine 2013; 32:271-6. [PMID: 24252692 DOI: 10.1016/j.vaccine.2013.11.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 09/27/2013] [Accepted: 11/06/2013] [Indexed: 11/29/2022]
Abstract
Vibrio vulnificus is a foodborne pathogen that is prevalent in coastal waters worldwide. Infection with V. vulnificus causes septicemia with fatality rates exceeding 50% even with aggressive antibiotic therapy. Several vaccine studies to prevent V. vulnificus infection have been performed but have had limited success. In this study, we identified the C-terminal region (amino acids 3491 to 4701) of the V. vulnificus multifunctional autoprocessing RTX (MARTXVv or RtxA1) protein, RtxA1-C, as a promising antigen that induces protective immune responses against V. vulnificus. Vaccination of mice with recombinant RtxA1-C protein with adjuvant elicited a robust antibody response and a dramatic reduction in blood bacterial load in mice infected intraperitoneally. Vaccination resulted in significant protection against lethal challenge with V. vulnificus. Furthermore, intraperitoneal passive immunization with serum raised against the recombinant RtxA1-C protein demonstrated marked efficacy in both prophylaxis and therapy. These results suggest that active and passive immunization against the C-terminal region of the RtxA1 protein may be an effective approach in the prevention and therapy of V. vulnificus infections.
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Affiliation(s)
- Tae Hee Lee
- Department of Microbiology and Immunology, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-756, Republic of Korea
| | - Mi Hyun Kim
- Department of Microbiology and Immunology, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-756, Republic of Korea
| | - Chang-Seop Lee
- Department of Internal Medicine, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-756, Republic of Korea
| | - Ju-Hyung Lee
- Department of Preventive Medicine, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-756, Republic of Korea
| | - Joon Haeng Rhee
- Clinical Vaccine R&D Center, Chonnam National University Medical School, Gwangju 520-724, Republic of Korea; Department of Microbiology, Chonnam National University Medical School, Gwangju 520-724, Republic of Korea
| | - Kyung Min Chung
- Department of Microbiology and Immunology, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-756, Republic of Korea; Institute for Medical Science, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-756, Republic of Korea.
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Contribution of six flagellin genes to the flagellum biogenesis of Vibrio vulnificus and in vivo invasion. Infect Immun 2013; 82:29-42. [PMID: 24101693 DOI: 10.1128/iai.00654-13] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Vibrio vulnificus is a halophilic pathogenic bacterium that is motile due to the presence of a single polar flagellum. V. vulnificus possesses a total of six flagellin genes organized into two loci (flaFBA and flaCDE). We proved that all six of the flagellin genes were transcribed, whereas only five (FlaA, -B, -C, -D, and -F) of the six flagellin proteins were detected. To understand roles of the six V. vulnificus flagellins in motility and virulence, mutants with single and multiple flagellin deletions were constructed. Mutations in flaB or flaC or the flaCDE locus resulted in a significant decrease in motility, adhesion, and cytotoxicity, whereas single mutations in the other flagellin genes or the flaFBA locus showed little or no effect. The motility was completely abolished only in the mutant lacking all six flagellin genes (flaFBA flaCDE). Surprisingly, a double mutation of flaB and flaD, a gene sharing 99% identity with the flaB at the amino acid level, resulted in the largest decrease in motility, adhesion, and cytotoxicity except for the mutant in which all six genes were deleted (the hexa mutant). Additionally, the 50% lethal doses (LD50s) of the flaB flaD and the flaFBA flaCDE mutants increased 23- and 91-fold in a mouse model, respectively, and the in vitro and in vivo invasiveness of the mutants was significantly decreased compared to that of the wild type. Taken together, the multiple flagellin subunits differentially contribute to the flagellum biogenesis and the pathogenesis of V. vulnificus, and among the six flagellin genes, flaB, flaD, and flaC were the most influential components.
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