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Lau YT, Tan HS. Acinetobacter baumannii subunit vaccines: recent progress and challenges. Crit Rev Microbiol 2024; 50:434-449. [PMID: 37211625 DOI: 10.1080/1040841x.2023.2215303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 03/28/2023] [Accepted: 05/12/2023] [Indexed: 05/23/2023]
Abstract
Acinetobacter baumannii is a Gram-negative, opportunistic pathogen that causes nosocomial infection with a high mortality rate in immunocompromised individuals. With the frequent emergence of multidrug-resistant A. baumannii strains that have rapidly gained resistance to most antibiotics, an extensive search for an effective A. baumannii vaccine is ongoing. Over the decade, many subunit vaccine candidates were identified using reverse vaccinology and in vivo animal studies for validation. Nineteen subunit vaccine candidates with a wide range of efficacy, from 14% to 100% preclinical survival rates, were included in this review. This article provides an updated review of several outer membrane proteins (Omp) that emerged as vaccine candidates with great potential, including OmpA, Omp34, Omp22 and BamA, based on their high conservancy, antigenicity, and immune protection against A. baumannii infection. However, there is still no licenced A. baumannii vaccine currently due to several practical issues that have yet to be resolved, such as inconsistencies between validation studies, antigen variability and insolubility. Moving forward, much investigation and innovation are still required to tackle these challenges for the regulatory approval of an A. baumannii subunit vaccine, including standardisation of immunisation study parameters, improving antigen solubility and the incorporation of nucleic acid vaccine technology.
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Affiliation(s)
- Yi Teng Lau
- School of Science, Monash University Malaysia, Bandar Sunway, Malaysia
| | - Hock Siew Tan
- School of Science, Monash University Malaysia, Bandar Sunway, Malaysia
- Tropical Medicine and Biology Multidisciplinary Platform, Monash University Malaysia, Bandar Sunway, Malaysia
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2
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Buchhorn de Freitas S, Hartwig DD. Promising targets for immunotherapeutic approaches against Acinetobacter baumannii. Microb Pathog 2022; 173:105855. [DOI: 10.1016/j.micpath.2022.105855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/21/2022] [Accepted: 10/24/2022] [Indexed: 11/11/2022]
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Yeganeh O, Shabani M, Pakzad P, Mosaffa N, Hashemi A. Evaluation the reactivity of a peptide-based monoclonal antibody derived from OmpA with drug resistant pulsotypes of Acinetobacter baumannii as a potential therapeutic approach. Ann Clin Microbiol Antimicrob 2022; 21:30. [PMID: 35773688 PMCID: PMC9245400 DOI: 10.1186/s12941-022-00523-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 06/21/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Acinetobacter baumannii is an opportunistic and antibiotic-resistant pathogen that predominantly causes nosocomial infections. There is urgent need for development nonantibiotic-based treatment strategies. We developed a novel monoclonal antibody (mAb) against a peptide of conserved outer membrane protein A (OmpA) and evaluated its reactivity with different pulsotypes of A. baumannii. METHODS Peptide derived from A. baumannii OmpA was conjugated to keyhole limpet hemocyanin and injected into BALB/c mice. Splenocytes of immunized mice were fused with SP2/0 myeloma cells followed by selection of antibody-producing hybridoma cells. After screening of different hybridoma colonies by ELISA, one monoclone was selected as 3F10-C9 and the antibody was tested for reaction with five different Acinetobacter pulsotypes that were resistant to carbapenem antibiotics. The affinity constant was measured by ELISA. The ELISA, western blotting, indirect immunofluorescence (IFA), and in vitro opsonophagocytosis assays were used to evaluate the reactivity of generated mAb. RESULTS The anti-OmpA antibody reacted with the immunizing peptide and had a high affinity (1.94 × 10-9 M) for its antigen in the ELISA. Specific binding of mAb to OmpA was confirmed in Western blot. IFA assays revealed that mAb recognized specific OmpA on the pulsotypes. Opsonophagocytosis assays showed that the mAb increased the bactericidal activity of macrophage cells. The antibody function was higher in the presence of serum complement. CONCLUSIONS The peptide-based mAb demonstrated optimal performance in laboratory experiments which may be appropriate in investigation on OmpA in Acinetobacter pathogenesis and development of passive immunization as a novel therapeutic approach.
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Affiliation(s)
- Omid Yeganeh
- Department of Microbiology, North Tehran Branch, Islamic Azad University, Tehran, Iran
| | - Mahdi Shabani
- Department of Immunology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Parviz Pakzad
- Department of Microbiology, North Tehran Branch, Islamic Azad University, Tehran, Iran
| | - Nariman Mosaffa
- Department of Immunology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Ali Hashemi
- Department of Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Tao Y, Duma L, Rossez Y. Galleria mellonella as a Good Model to Study Acinetobacter baumannii Pathogenesis. Pathogens 2021; 10:1483. [PMID: 34832638 PMCID: PMC8623143 DOI: 10.3390/pathogens10111483] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 11/08/2021] [Accepted: 11/10/2021] [Indexed: 12/29/2022] Open
Abstract
The invertebrate model, Galleria mellonella, has been widely used to study host-pathogen interactions due to its cheapness, ease of handling, and similar mammalian innate immune system. G. mellonella larvae have been proven to be useful and a reliable model for analyzing pathogenesis mechanisms of multidrug resistant Acinetobacter baumannii, an opportunistic pathogen difficult to kill. This review describes the detailed experimental design of G. mellonella/A. baumannii models, and provides a comprehensive comparison of various virulence factors and therapy strategies using the G. mellonella host. These investigations highlight the importance of this host-pathogen model for in vivo pathogen virulence studies. On the long term, further development of the G. mellonella/A. baumannii model will offer promising insights for clinical treatments of A. baumannii infection.
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Affiliation(s)
- Ye Tao
- Université de Technologie de Compiègne, UPJV, UMR CNRS 7025, Enzyme and Cell Engineering, Centre de Recherche Royallieu–CS 60 319 , 60203 Compiègne, France; (Y.T.); (L.D.)
| | - Luminita Duma
- Université de Technologie de Compiègne, UPJV, UMR CNRS 7025, Enzyme and Cell Engineering, Centre de Recherche Royallieu–CS 60 319 , 60203 Compiègne, France; (Y.T.); (L.D.)
- Université de Reims Champagne-Ardenne, CNRS, ICMR UMR 7312, 51097 Reims, France
| | - Yannick Rossez
- Université Lille, CNRS, UMR 8576-UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, F-59000 Lille, France
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Ma C, Chen W. Where are we and how far is there to go in the development of an Acinetobacter vaccine? Expert Rev Vaccines 2021; 20:281-295. [PMID: 33554671 DOI: 10.1080/14760584.2021.1887735] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Healthcare-associated infections caused by multidrug-resistant Acinetobacter baumannii are becoming alarming worldwide. However, the pipeline of new antibiotics is very limited. Vaccination is one of the most cost effective and promising strategies to prevent infections and can play an important role in combat multidrug resistance A. baumannii and prevent the development of new drug resistance. AREA COVERED This review gives an overview of the research and development of A. baumannii vaccines during the past five years (2015-2020), discusses the key progresses and current challenges of the field, and speculates on the future of A. baumannii vaccine development. EXPERT OPINION Moderate progresses have been made in the research and development of A. baumannii vaccine in the last five years, in particular in the areas of identification of new protein targets, development of multicomponent vaccines, and use of vaccines and antibodies as adjuncts for antibiotics therapies. However, substantial scientific and logistic challenges, such as selection of lead vaccine candidates and formulation, vaccine clinical trials and targeted population, and financial incentives, remain. Thus, innovative strategies will be needed before an A. baumannii vaccine candidate can be brought into late stage of preclinical development in next five years.
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Affiliation(s)
- Crystal Ma
- Human Health Therapeutics Research Center (HHT), National Research Council Canada, Ottawa, Ontario Canada
| | - Wangxue Chen
- Human Health Therapeutics Research Center (HHT), National Research Council Canada, Ottawa, Ontario Canada.,Department of Biology, Brock University, St. Catharines, Ontario Canada
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Sogasu D, Girija ASS, Gunasekaran S, Priyadharsini JV. Molecular characterization and epitope-based vaccine predictions for ompA gene associated with biofilm formation in multidrug-resistant strains of A.baumannii. In Silico Pharmacol 2021; 9:15. [PMID: 33520594 PMCID: PMC7829033 DOI: 10.1007/s40203-020-00074-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 12/26/2020] [Indexed: 11/28/2022] Open
Abstract
The present study was conducted to molecularly characterize the biofilm associated ompA gene from the drug resistant strains of A. baumannii and its immuno-dominant vaccine epitope predictions through immuno-informatic approach. ompA was amplified by PCR from the genomic DNA and was sequenced. Using the ORF, ompA protein sequence was retrieved and was subjected for IEDB T cell and B cell epitope analysis for the selection of the epitope peptides. Selected peptides were evaluated using appropriate servers and tools to assess the propensity for its antigenicity, solubility, physico-chemical property, toxigenicity and class-I immunogenicity. MHC class I and II restriction of HLA alleles was also performed. 48% (n = 24) of the strains possessed ompA gene. Protein structure was successfully retrieved with the selection of two epitopes viz., E1- FDGVNRGTRGTSEEGTLGNA and E2-KLSEYPNATARIEGHTDNTGPRKL. Final docking with TLR-2, showed E2 as the best epitope candidate predicted with the highest number of hydrogen bonds.
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Affiliation(s)
- Deepthi Sogasu
- Department of Microbiology, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences [SIMATS], Saveetha University, P.H.Road, Chennai, Tamilnadu, 600077 India
| | - A S Smiline Girija
- Department of Microbiology, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences [SIMATS], Saveetha University, P.H.Road, Chennai, Tamilnadu, 600077 India
| | - Shoba Gunasekaran
- Department of Biotechnology, Dwaraka Doss Goverdhan Doss Vaishnav College, Arumbakkam, Chennai, 60010 India
| | - J Vijayashree Priyadharsini
- DRC, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences [SIMATS], Saveetha University, P.H.Road, Chennai, Tamilnadu 600077 India
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Abarghooi Kahaki F, Monzavi S, Bamehr H, Bandani E, Payandeh Z, Jahangiri A, Khalili S. Expression and Purification of Membrane Proteins in Different Hosts. Int J Pept Res Ther 2020. [DOI: 10.1007/s10989-019-10009-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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8
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Passive immunization with chitosan-loaded biofilm-associated protein against Acinetobacter baumannii murine infection model. GENE REPORTS 2020. [DOI: 10.1016/j.genrep.2020.100708] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Ramezanalizadeh F, Owlia P, Rasooli I. Type I pili, CsuA/B and FimA induce a protective immune response against Acinetobacter baumannii. Vaccine 2020; 38:5436-5446. [DOI: 10.1016/j.vaccine.2020.06.052] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 06/02/2020] [Accepted: 06/18/2020] [Indexed: 12/13/2022]
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Genetic mechanisms of antibiotic resistance and virulence in Acinetobacter baumannii: background, challenges and future prospects. Mol Biol Rep 2020; 47:4037-4046. [PMID: 32303957 DOI: 10.1007/s11033-020-05389-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 03/24/2020] [Indexed: 01/18/2023]
Abstract
With the advent of the multidrug-resistant era, many opportunistic pathogens including the species Acinetobacter baumannii have gained prominence and pose a major global threat to clinical health care. Pathogenicity in bacteria is genetically regulated by a complex network of transcription and virulence factors and a brief overview of the major investigations on comprehending these processes over the past few decades in A. baumanni are compiled here. Many investigators have employed genome sequencing techniques to identify the regions that contribute to antibiotic resistance and comparative genomics to study sequence similarities to understand evolutionary trends of resistance gene transfers between isolates. A summary of these studies given here provides an insight into the invasion and successful colonization of the species. The individual roles played by different genes, regulators & promoters, enzymes, metal ions as well as mobile elements in influencing antibiotic resistance are briefly discussed. Precautionary measures and prospects for developing future strategies by exploring promising new research targets in effective control of multidrug resistant A. baumannii are also analyzed.
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Preparation and Purification of Recombinant Protein Fragment OmpA240-356 from Acinetobacter baumannii as a Novel Epitope for Vaccination. ARCHIVES OF CLINICAL INFECTIOUS DISEASES 2019. [DOI: 10.5812/archcid.85933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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12
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Jahangiri A, Owlia P, Rasooli I, Salimian J, Derakhshanifar E, Naghipour Erami A, Darzi Eslam E, Darvish Alipour Astaneh S. Specific egg yolk antibodies (IgY) confer protection against Acinetobacter baumannii in a murine pneumonia model. J Appl Microbiol 2018; 126:624-632. [PMID: 30353977 DOI: 10.1111/jam.14135] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 09/29/2018] [Accepted: 10/15/2018] [Indexed: 11/30/2022]
Abstract
AIM Acinetobacter baumannii, an increasingly serious health threat, is considered as one of the six most dangerous microbes of high mortality rate. However, treatment of its infections is difficult because of the lack of efficient antibiotic or commercial vaccines. Passive immunization through administration of specific antibodies such as IgY, could be an attractive practical solution. METHODS AND RESULTS In the current study, antigenicity of two recombinant outer membrane proteins (OmpA and Omp34) as well as inactivated whole cell of A. baumannii was assessed by ELISA. Moreover, prophylactic effects of specific IgY antibodies (avian antibody) raised against these antigens were evaluated in a murine pneumonia model. The specific IgY antibodies had various prophylactic effects in the pneumonia model. OmpA was the most potent antigen in terms of triggering antibody and conferring protection. While a synergic effect was observed in ELISA for antibodies raised against a combination of OmpA and Omp34 (which are known as Omp33-36 and Omp34 kDa), an antagonistic effect was unexpectedly seen in challenges. The reason for this phenomenon remains to be precisely addressed. CONCLUSION All the specific IgY antibodies could protect mice against pneumonia caused by A. baumannii. SIGNIFICANCE AND IMPACT OF THE STUDY The specific IgY antibodies could be employed as a pharmaceutical against pneumonia caused by A. baumannii.
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Affiliation(s)
- A Jahangiri
- Department of Biology, Shahed University, Tehran, Iran.,Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - P Owlia
- Molecular Microbiology Research Center, Shahed University, Tehran, Iran.,Department of Microbiology, Shahed University Faculty of Medical Sciences, Tehran, Iran
| | - I Rasooli
- Department of Biology, Shahed University, Tehran, Iran.,Molecular Microbiology Research Center, Shahed University, Tehran, Iran
| | - J Salimian
- Chemical Injuries Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | | | | | - E Darzi Eslam
- Department of Biology, Shahed University, Tehran, Iran
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Cellular and humoral immune response to recombinant Escherichia coli OmpA in cows. PLoS One 2017; 12:e0187369. [PMID: 29088296 PMCID: PMC5663511 DOI: 10.1371/journal.pone.0187369] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 10/18/2017] [Indexed: 12/15/2022] Open
Abstract
The outer membrane protein (Omp) A is a major constituent of the outer membrane of Escherichia coli. This protein has been used in several vaccine development studies, but seldom with a view to vaccinating against mastitis. The objective of this study was to investigate the immunogenicity of E. coli OmpA and its vaccine potential for cows. Both the humoral and cellular immune responses were investigated. The gene for OmpA of the mastitis-causing strain P4 was cloned and expressed, and the recombinant protein (rEcOmpA) purified. Cows were immunized twice with rEcOmpA with adjuvant one month apart by the systemic route. Before immunization, few antibodies to rEcOmpA were detected, and there was little production of IL-17A in a whole blood stimulation assay (WBA) with rEcOmpA. Antibodies to rEcOmpA were induced by immunization. These antibodies were not able to react with E. coli P4, but reacted with a rough P4 mutant prepared by inactivating the rfb locus. This suggests that the complete LPS O-chain precluded the accessibility of antibodies to their target at the outer membrane. The cellular immune response appeared to be biased towards a Th17-type, as more IL-17A than IFN-γ was produced in the OmpA-specific WBA. There was a good correlation between antibody titers and the production of IL-17A in the WBA. The intramammary instillation of rEcOmpA elicited a slight local inflammatory response which was not related to the WBA. Overall, the interest of OmpA as vaccine immunogen was not established, although other experimental conditions (dose, adjuvant, route) need to be investigated to conclude definitively. The study pointed to several important issues such as the accessibility of OmpA to antibodies and the weakness of Th1-type response induced by OmpA.
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Van Lent S, De Vos WH, Huot Creasy H, Marques PX, Ravel J, Vanrompay D, Bavoil P, Hsia RC. Analysis of Polymorphic Membrane Protein Expression in Cultured Cells Identifies PmpA and PmpH of Chlamydia psittaci as Candidate Factors in Pathogenesis and Immunity to Infection. PLoS One 2016; 11:e0162392. [PMID: 27631978 PMCID: PMC5025070 DOI: 10.1371/journal.pone.0162392] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 08/22/2016] [Indexed: 12/22/2022] Open
Abstract
The polymorphic membrane protein (Pmp) paralogous families of Chlamydia trachomatis, Chlamydia pneumoniae and Chlamydia abortus are putative targets for Chlamydia vaccine development. To determine whether this is also the case for Pmp family members of C. psittaci, we analyzed transcription levels, protein production and localization of several Pmps of C. psittaci. Pmp expression profiles were characterized using quantitative real-time PCR (RT-qPCR), immunofluorescence (IF) and immuno-electron microscopy (IEM) under normal and stress conditions. We found that PmpA was highly produced in all inclusions as early as 12 hpi in all biological replicates. In addition, PmpA and PmpH appeared to be unusually accessible to antibody as determined by both immunofluorescence and immuno-electron microscopy. Our results suggest an important role for these Pmps in the pathogenesis of C. psittaci, and make them promising candidates in vaccine development.
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Affiliation(s)
- Sarah Van Lent
- Department of Animal Production, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
- * E-mail:
| | - Winnok H. De Vos
- Department of Veterinary Sciences, Faculty of Pharmaceutical, Biomedical and Veterinary Sciences, University of Antwerp, Antwerp, Belgium
- Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Heather Huot Creasy
- Institute for Genome Sciences and Department of Microbiology & Immunology, University of Maryland School of Medicine, Baltimore, Maryland, Unites States of America
| | - Patricia X. Marques
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, Maryland, Unites States of America
| | - Jacques Ravel
- Institute for Genome Sciences and Department of Microbiology & Immunology, University of Maryland School of Medicine, Baltimore, Maryland, Unites States of America
| | - Daisy Vanrompay
- Department of Animal Production, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Patrik Bavoil
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, Maryland, Unites States of America
| | - Ru-ching Hsia
- University of Maryland, Baltimore, Electron Microscopy Core Imaging Facility, Maryland, Unites States of America
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Characterization of surface antigen protein 1 (SurA1) from Acinetobacter baumannii and its role in virulence and fitness. Vet Microbiol 2016; 186:126-38. [PMID: 27016767 DOI: 10.1016/j.vetmic.2016.02.018] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Revised: 01/24/2016] [Accepted: 02/22/2016] [Indexed: 01/02/2023]
Abstract
Acinetobacter baumannii is a Gram-negative bacillus that causes nosocomial infections, such as bacteremia, pneumonia, and meningitis and urinary tract and wound infections. In the present study, the surface antigen protein 1 (SurA1) gene of A. baumannii strain CCGGD201101 was identified, cloned and expressed, and then its roles in fitness and virulence were investigated. Virulence was observed in the human lung cancer cell lines A549 and HEp-2 at one week after treatment with recombinant SurA1. One isogenic SurA1 knock-out strain, GR0015, which was derived from the A. baumannii strain CCGGD201101 isolated from diseased chicks in a previous study, highlighted the effect of SurA1 on fitness and growth. Its growth rate in LB broth and killing activity in human sera were significantly decreased compared with strain CCGGD201101. In the Galleria mellonella insect model, the isogenic SurA1 knock-out strain exhibited a lower survival rate and decreased dissemination. These results suggest that SurA1 plays an important role in the fitness and virulence of A. baumannii.
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Immunization with a 22-kDa outer membrane protein elicits protective immunity to multidrug-resistant Acinetobacter baumannii. Sci Rep 2016; 6:20724. [PMID: 26853590 PMCID: PMC4745112 DOI: 10.1038/srep20724] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 01/11/2016] [Indexed: 11/28/2022] Open
Abstract
A. baumannii infections are becoming more and more serious health issues with rapid emerging of multidrug and extremely drug resistant strains, and therefore, there is an urgent need for the development of nonantibiotic-based intervention strategies. This study aimed at identifying whether an outer membrane protein with molecular weight of about 22 kDa (Omp22) holds the potentials to be an efficient vaccine candidate and combat A. baumannii infection. Omp22 which has a molecule length of 217 amino acids kept more than 95% conservation in totally 851 reported A. baumannii strains. Recombinant Omp22 efficiently elicited high titers of specific IgG in mice. Both active and passive immunizations of Omp22 increased the survival rates of mice, suppressed the bacterial burdens in the organs and peripheral blood, and reduced the levels of serum inflammatory cytokines and chemokines. Opsonophagocytosis assays showed in vitro that Omp22 antiserum had highly efficient bactericidal activities on clonally distinct clinical A. baumannii isolates, which were partly complements-dependent and opsonophagocytic killing effects. Additionally, administration with as high as 500 μg of Omp22 didn’t cause obvious pathological changes in mice. In conclusion, Omp22 is a novel conserved and probably safe antigen for developing effective vaccines or antisera to control A. baumannii infections.
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Huang W, Wang S, Yao Y, Xia Y, Yang X, Long Q, Sun W, Liu C, Li Y, Ma Y. OmpW is a potential target for eliciting protective immunity against Acinetobacter baumannii infections. Vaccine 2015. [PMID: 26207591 DOI: 10.1016/j.vaccine.2015.07.031] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Acinetobacter baumannii (A. baumannii) is an important conditioned pathogen that causes nosocomial and community-associated infections. In this study, we sought to investigate whether outer membrane protein W (OmpW) is a potential target for eliciting protective immunity against A. baumannii infections. Mice immunized with the fusion protein thioredoxin-OmpW generated strong OmpW-specific IgG responses. In a sepsis model, both active and passive immunizations against OmpW effectively protected mice from A. baumannii infections. This protection was demonstrated by a significantly improved survival rate, reduced bacterial burdens within organs, and the suppressed accumulation of inflammatory cytokines and chemokines in sera. Opsonophagocytic assays with murine macrophage RAW264.7 cells indicated that the bactericidal effects of the antisera derived from the immunized mice are mediated synergistically by specific antibodies and complement components. The antisera presented significant opsonophagocytic activities against homologous strains and clonally distinct clinical isolates in vitro. Protein data analysis showed that the sequence of OmpW, which has a molecule length of 183 amino acids, is more than 91% conserved in reported A. baumannii strains. In conclusion, we identified OmpW as a highly immunogenic and conserved protein as a valuable antigen candidate for the development of an effective vaccine or the preparation of antisera to control A. baumannii infections.
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Affiliation(s)
- Weiwei Huang
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Shijie Wang
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Yufeng Yao
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Ye Xia
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Xu Yang
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Qiong Long
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Wenjia Sun
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Cunbao Liu
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Yang Li
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China
| | - Yanbing Ma
- Laboratory of Molecular Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China; Yunnan Key Laboratory of Vaccine Research & Development on Severe Infectious Diseases, Kunming 650118, China; Yunnan Engineering Research Center of Vaccine Research and Development on Severe Infectious Diseases, Kunming 650118, China.
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Badmasti F, Siadat SD, Bouzari S, Ajdary S, Shahcheraghi F. Molecular detection of genes related to biofilm formation in multidrug-resistant Acinetobacter baumannii isolated from clinical settings. J Med Microbiol 2015; 64:559-564. [DOI: 10.1099/jmm.0.000058] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 03/17/2015] [Indexed: 01/13/2023] Open
Affiliation(s)
- Farzad Badmasti
- Department of Bacteriology, Pasteur Institute of Iran, Tehran, Iran
| | | | - Saeid Bouzari
- Department of Molecular Biology, Pasteur Institute of Iran, Tehran, Iran
| | - Soheila Ajdary
- Department of Immunology, Pasteur Institute of Iran, Tehran, Iran
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Eijkelkamp BA, Stroeher UH, Hassan KA, Paulsen IT, Brown MH. Comparative analysis of surface-exposed virulence factors of Acinetobacter baumannii. BMC Genomics 2014; 15:1020. [PMID: 25422040 PMCID: PMC4256060 DOI: 10.1186/1471-2164-15-1020] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 11/14/2014] [Indexed: 01/19/2023] Open
Abstract
Background Acinetobacter baumannii is a significant hospital pathogen, particularly due to the dissemination of highly multidrug resistant isolates. Genome data have revealed that A. baumannii is highly genetically diverse, which correlates with major variations seen at the phenotypic level. Thus far, comparative genomic studies have been aimed at identifying resistance determinants in A. baumannii. In this study, we extend and expand on these analyses to gain greater insight into the virulence factors across eight A. baumannii strains which are clonally, temporally and geographically distinct, and includes an isolate considered non-pathogenic and a community-acquired A. baumannii. Results We have identified a large number of genes in the A. baumannii genomes that are known to play a role in virulence in other pathogens, such as the recently studied proline-alanine-alanine-arginine (PAAR)-repeat domains of the type VI secretion systems. Not surprising, many virulence candidates appear to be part of the A. baumannii core genome of virulent isolates but were often found to be insertionally disrupted in the avirulent A. baumannii strain SDF. Our study also reveals that many known or putative virulence determinants are restricted to specific clonal lineages, which suggests that these virulence determinants may be crucial for the success of these widespread common clones. It has previously been suggested that the high level of intrinsic and adaptive resistance has enabled the widespread presence of A. baumannii in the hospital environment. This appears to have facilitated the expansion of its repertoire of virulence traits, as in general, the nosocomial strains in this study possess more virulence genes compared to the community-acquired isolate. Conclusions Major genetic variation in known or putative virulence factors was seen across the eight strains included in this study, suggesting that virulence mechanisms are complex and multifaceted in A. baumannii. Overall, these analyses increase our understanding of A. baumannii pathogenicity and will assist in future studies determining the significance of virulence factors within clonal lineages and/or across the species. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1020) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | - Melissa H Brown
- School of Biological Sciences, Flinders University, Adelaide, Australia.
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A conserved region from biofilm associated protein as a biomarker for detection of Acinetobacter baumannii. Microb Pathog 2014; 77:84-8. [PMID: 25450883 DOI: 10.1016/j.micpath.2014.11.004] [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: 08/27/2014] [Revised: 11/01/2014] [Accepted: 11/05/2014] [Indexed: 11/22/2022]
Abstract
Acinetobacter baumannii is the leading cause of nosocominal infection within the family Moraxellaceae. Due to multiple antibiotic resistances of the bacteria, the treatment is very difficult, hence specific and economical test for early diagnosis of infection is needed. Development of such a test requires targeting specific cell surface antigens. Bacterial ability of biofilm formation grants major contribution in antimicrobial resistance and other environmental stresses such as nutrient limitation and dehydration. Biofilm associated protein (Bap), a specific cell surface protein, is directly involved in A. baumannii biofilm formation. The goal of this study is diagnosis of A. baumannii infection exploiting specific target from Bap. A selected subunit of Bap was cloned, expressed and purified. Mice were divided into three groups. Group one was immunized with recombinant Bap subunit, mice in group two were infected with A. baumannii (positive control) and mice in groups three served as negative control. Immunization with Bap subunit resulted in high antibody titers. Animals in control group that received same amount of adjuvant and PBS showed no Bap-specific antibodies. Sensitivity and specificity of the antibodies raised were determined by ELISA and Western blotting. Recombinant Bap subunit was tested by ELISA using sera obtained from A. baumannii infected patients and healthy individuals. This conserved and immunodominant region of Bap could serve as an appropriate target for diagnosis A. baumannii infection.
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Fajardo Bonin R, Chapeaurouge A, Perales J, da Silva JG, do Nascimento HJ, D'Alincourt Carvalho Assef AP, Moreno Senna JP. Identification of immunogenic proteins of the bacterium Acinetobacter baumannii using a proteomic approach. Proteomics Clin Appl 2014; 8:916-23. [PMID: 24899143 DOI: 10.1002/prca.201300133] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 04/08/2014] [Accepted: 05/28/2014] [Indexed: 11/11/2022]
Abstract
PURPOSE Acinetobacter baumannii is an important opportunistic pathogen that causes pneumoniae, urinary tract infections, and/or septicemia in immunocompromised patients. This pathogen is frequently associated with nosocomial outbreaks worldwide and has become particularly problematic because of its prevalence and resistance patterns to several antibiotics. In the present study, we used an immunoproteome-based approach to identify immunogenic proteins located on the surface of A. baumannii for the development of a possible immunotherapy against this devastating bacterial infection. EXPERIMENTAL DESIGN Sera from patients with A. baumannii infections (n = 50) and from a control group of healthy individuals (n = 3) were analyzed for reactivity against A. baumannii outer membrane proteins (OMPs) using Western blot analysis. To identify potential immunogenic proteins in A. baumannii, OMPs were separated by 2DE, and reactive sera from infected patients were randomly selected and divided into two different pools, each containing 15 sera. Finally, MALDI-TOF/TOF mass spectrometric analysis was employed to identify the corresponding proteins. RESULTS This analysis identified six immunoreactive proteins: OmpA, Omp34kDa, OprC, OprB-like, OXA-23, and ferric siderophore receptor protein. Notably, these proteins are highly abundant on the bacterial surface and involved in virulence, antibiotic resistance, and growth. CONCLUSIONS AND CLINICAL RELEVANCE Our results support the notion that the proteins identified in the present immunoproteome study could serve as antigen candidates for the development of vaccines and passive immunotherapies against A. baumannii infections.
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de Gouw D, Jonge MID, Hermans PWM, Wessels HJCT, Zomer A, Berends A, Pratt C, Berbers GA, Mooi FR, Diavatopoulos DA. Proteomics-identified Bvg-activated autotransporters protect against bordetella pertussis in a mouse model. PLoS One 2014; 9:e105011. [PMID: 25133400 PMCID: PMC4136822 DOI: 10.1371/journal.pone.0105011] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 07/15/2014] [Indexed: 11/30/2022] Open
Abstract
Pertussis is a highly infectious respiratory disease of humans caused by the bacterium Bordetella pertussis. Despite high vaccination coverage, pertussis has re-emerged globally. Causes for the re-emergence of pertussis include limited duration of protection conferred by acellular pertussis vaccines (aP) and pathogen adaptation. Pathogen adaptations involve antigenic divergence with vaccine strains, the emergence of strains which show enhanced in vitro expression of a number of virulence-associated genes and of strains that do not express pertactin, an important aP component. Clearly, the identification of more effective B. pertussis vaccine antigens is of utmost importance. To identify novel antigens, we used proteomics to identify B. pertussis proteins regulated by the master virulence regulatory system BvgAS in vitro. Five candidates proteins were selected and it was confirmed that they were also expressed in the lungs of naïve mice seven days after infection. The five proteins were expressed in recombinant form, adjuvanted with alum and used to immunize mice as stand-alone antigens. Subsequent respiratory challenge showed that immunization with the autotransporters Vag8 and SphB1 significantly reduced bacterial load in the lungs. Whilst these antigens induced strong opsonizing antibody responses, we found that none of the tested alum-adjuvanted vaccines - including a three-component aP - reduced bacterial load in the nasopharynx, suggesting that alternative immunological responses may be required for efficient bacterial clearance from the nasopharynx.
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Affiliation(s)
- Daan de Gouw
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands
- Laboratory of Medical Immunology, Department of Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Marien I. de. Jonge
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands
- Laboratory of Medical Immunology, Department of Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Peter W. M. Hermans
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands
- Laboratory of Medical Immunology, Department of Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Hans J. C. T. Wessels
- Nijmegen Centre for Mitochondrial Disorders, Department of Laboratory Medicine, Radboud Proteomics Centre, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Aldert Zomer
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands
- Laboratory of Medical Immunology, Department of Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Alinda Berends
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands
- Laboratory of Medical Immunology, Department of Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Catherine Pratt
- Public Health England, Centre for Emergency Preparedness and Response, Porton Down, Salisbury, United Kingdom
| | - Guy A. Berbers
- Netherlands Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
| | - Frits R. Mooi
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands
- Laboratory of Medical Immunology, Department of Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
- Netherlands Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
| | - Dimitri A. Diavatopoulos
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands
- Laboratory of Medical Immunology, Department of Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
- * E-mail:
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Darvish Alipour Astaneh S, Rasooli I, Mousavi Gargari SL. The role of filamentous hemagglutinin adhesin in adherence and biofilm formation in Acinetobacter baumannii ATCC19606(T). Microb Pathog 2014; 74:42-9. [PMID: 25086432 DOI: 10.1016/j.micpath.2014.07.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/14/2014] [Accepted: 07/21/2014] [Indexed: 11/17/2022]
Abstract
Filamentous hemagglutinin adhesins (FHA) are key factors for bacterial attachment and subsequent cell accumulation on substrates. Here an FHA-like Outer membrane (OM) adhesin of Acinetobacter baumannii ATCC19606(T) was displayed on Escherichia coli. The candidate autotransporter (AT) genes were identified in A. baumannii ATCC19606(T) genome. The exoprotein (FhaB1) and transporter (FhaC1) were produced independently within the same cell (FhaB1C1). The fhaC1 was mutated. In vitro adherence to epithelial cells of the recombinant FhaB1C1 and the mutant strains were compared with A. baumanni ATCC19606(T). A bivalent chimeric protein (K) composed of immunologically important portions of fhaB1 (B) and fhaC1 (C) was constructed. The mice vaccinated with chimeric protein were challenged with A. baumannii ATCC19606(T) and FhaB1C1 producing recombinant E. coli. Mutations in the fhaC1 resulted in the absence of FhaB1 in the OM. Expression of FhaB1C1 enhanced the adherence of recombinant bacteria to A546 bronchial cell line. The results revealed association of FhaB1 with bacterial adhesion and biofilm formation. Immunization with a combination of recombinant B and K proteins proved protective against A. baumanni ATCC19606(T). The findings may be applied in active and passive immunization strategies against A. baumannii.
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Affiliation(s)
| | - Iraj Rasooli
- Department of Biology, Shahed University, Opposite Imam Khomeini's Shrine, Tehran-Qom Express Way, Tehran, Iran; Molecular Microbiology Research Center, Shahed University, Tehran, Iran.
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Identification of novel vaccine candidates against multidrug-resistant Acinetobacter baumannii. PLoS One 2013; 8:e77631. [PMID: 24116234 PMCID: PMC3792912 DOI: 10.1371/journal.pone.0077631] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 09/03/2013] [Indexed: 12/29/2022] Open
Abstract
Acinetobacter baumannii is an emerging opportunistic bacterium associated with nosocomial infections in intensive care units. The alarming increase in infections caused by A. baumannii is strongly associated with enhanced resistance to antibiotics, in particular carbapenems. This, together with the lack of a licensed vaccine, has translated into significant economic, logistic and health impacts to health care facilities. In this study, we combined reverse vaccinology and proteomics to identify surface-exposed and secreted antigens from A. baumannii. Using in silico prediction tools and comparative genome analysis in combination with in vitro proteomic approaches, we identified 42 antigens that could be used as potential vaccine targets. Considering the paucity of effective antibiotics available to treat multidrug-resistant A. baumannii infections, these vaccine targets may serve as a framework for the development of a broadly protective multi-component vaccine, an outcome that would have a major impact on the burden of A. baumannii infections in intensive care units across the globe.
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H-NS plays a role in expression of Acinetobacter baumannii virulence features. Infect Immun 2013; 81:2574-83. [PMID: 23649094 DOI: 10.1128/iai.00065-13] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Acinetobacter baumannii has become a major problem in the clinical setting with the prevalence of infections caused by multidrug-resistant strains on the increase. Nevertheless, only a limited number of molecular mechanisms involved in the success of A. baumannii as a human pathogen have been described. In this study, we examined the virulence features of a hypermotile derivative of A. baumannii strain ATCC 17978, which was found to display enhanced adherence to human pneumocytes and elevated levels of lethality toward Caenorhabditis elegans nematodes. Analysis of cellular lipids revealed modifications to the fatty acid composition, providing a possible explanation for the observed changes in hydrophobicity and subsequent alteration in adherence and motility. Comparison of the genome sequences of the hypermotile variant and parental strain revealed that an insertion sequence had disrupted an hns-like gene in the variant. This gene encodes a homologue of the histone-like nucleoid structuring (H-NS) protein, a known global transcriptional repressor. Transcriptome analysis identified the global effects of this mutation on gene expression, with major changes seen in the autotransporter Ata, a type VI secretion system, and a type I pilus cluster. Interestingly, isolation and analysis of a second independent hypermotile ATCC 17978 variant revealed a mutation to a residue within the DNA binding region of H-NS. Taken together, these mutants indicate that the phenotypic and transcriptomic differences seen are due to loss of regulatory control effected by H-NS.
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Smani Y, McConnell MJ, Pachón J. Role of fibronectin in the adhesion of Acinetobacter baumannii to host cells. PLoS One 2012; 7:e33073. [PMID: 22514602 PMCID: PMC3326023 DOI: 10.1371/journal.pone.0033073] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 02/09/2012] [Indexed: 11/29/2022] Open
Abstract
Adhesion to host cells is an initial and important step in Acinetobacter baumannii pathogenesis. However, there is relatively little information on the mechanisms by which A. baumannii binds to and interacts with host cells. Adherence to extracellular matrix proteins, such as fibronectin, affords pathogens with a mechanism to invade epithelial cells. Here, we found that A. baumannii adheres more avidly to immobilized fibronectin than to control protein. Free fibronectin used as a competitor resulted in dose-dependent decreased binding of A. baumannii to fibronectin. Three outer membrane preparations (OMPs) were identified as fibronectin binding proteins (FBPs): OMPA, TonB-dependent copper receptor, and 34 kDa OMP. Moreover, we demonstrated that fibronectin inhibition and neutralization by specific antibody prevented significantly the adhesion of A. baumannii to human lung epithelial cells (A549 cells). Similarly, A. baumannii OMPA neutralization by specific antibody decreased significantly the adhesion of A. baumannii to A549 cells. These data indicate that FBPs are key adhesins that mediate binding of A. baumannii to human lung epithelial cells through interaction with fibronectin on the surface of these host cells.
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Affiliation(s)
- Younes Smani
- Clinic Unit of Infectious Diseases, Microbiology and Preventive Medicine, Institute of Biomedicine of Seville, IBiS, University Hospital Virgen del Rocío/CSIC/University of Seville, Seville, Spain.
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Oral vaccination with Lactococcus lactis expressing the Vibrio cholerae Wzm protein to enhance mucosal and systemic immunity. Vaccine 2012; 30:3231-8. [PMID: 22426330 DOI: 10.1016/j.vaccine.2012.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2011] [Revised: 02/02/2012] [Accepted: 02/05/2012] [Indexed: 11/22/2022]
Abstract
A gene associated with lipopolysaccharide (LPS) transport was cloned from a local clinical Vibrio cholerae O1 strain of the Ogawa serotype by using the Lactococcus lactis nisin-controlled expression (NICE) system. The V. cholerae wzm gene, which codes for an integral membrane transporter protein, was expressed and targeted to the cytoplasmic membrane, and was crudely isolated through simple centrifugation and SDS solubilization. To examine seroreactivity of this construct, rabbits were orally fed with 10(9) cfu/ml of live, recombinant L. lactis carrying the wzm gene, induced with nisin prior to administration. Recombinant plasmids were retrieved from L. lactis cultured directly from stool samples of inoculated rabbits. Reverse-transcriptase PCR of wzm using the retrieved plasmids confirmed transcription of this gene, indicating viability and stability of the recombinants in vivo. The L. lactis-Wzm construct elicited substantial levels of IgG and sIgA, and challenge with virulent V. cholerae O1 evoked severe diarrhoea in the naive, non-immunised control group, but not in those fed with either recombinant or non-recombinant L. lactis. Oral administration with recombinant L. lactis expressing the V. cholerae wzm gene increases both systemic and mucosal immunity, whereas L. lactis itself appears capable of protecting against the diarrhoeal symptoms caused by V. cholerae. Wzm is a conserved membrane protein associated with the LPS endotoxin, and together with the food-grade L. lactis, represent an attractive target for the development of a safer, live anti-infective therapy against V. cholerae.
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Active and passive immunization protects against lethal, extreme drug resistant-Acinetobacter baumannii infection. PLoS One 2012; 7:e29446. [PMID: 22253723 PMCID: PMC3254619 DOI: 10.1371/journal.pone.0029446] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Accepted: 11/28/2011] [Indexed: 12/04/2022] Open
Abstract
Extreme-drug-resistant (XDR) Acinetobacter baumannii is a rapidly emerging pathogen causing infections with unacceptably high mortality rates due to inadequate available treatment. New methods to prevent and treat such infections are a critical unmet medical need. To conduct a rational vaccine discovery program, OmpA was identified as the primary target of humoral immune response after intravenous infection by A. baumannii in mice. OmpA was >99% conserved at the amino acid level across clinical isolates harvested between 1951 and 2009 from cerebrospinal fluid, blood, lung, and wound infections, including carbapenem-resistant isolates, and was ≥89% conserved among other sequenced strains, but had minimal homology to the human proteome. Vaccination of diabetic mice with recombinant OmpA (rOmpA) with aluminum hydroxide adjuvant markedly improved survival and reduced tissue bacterial burden in mice infected intravenously. Vaccination induced high titers of anti-OmpA antibodies, the levels of which correlated with survival in mice. Passive transfer with immune sera recapitulated protection. Immune sera did not enhance complement-mediated killing but did enhance opsonophagocytic killing of A. baumannii. These results define active and passive immunization strategies to prevent and treat highly lethal, XDR A. baumannii infections.
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