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Miranda-CasoLuengo R, Yerlikaya Z, Luo H, Cheng C, Blanco A, Haas A, Meijer WG. The N-terminal domain is required for cell surface localisation of VapA, a member of the Vap family of Rhodococcus equi virulence proteins. PLoS One 2024; 19:e0298900. [PMID: 38421980 PMCID: PMC10903876 DOI: 10.1371/journal.pone.0298900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 01/31/2024] [Indexed: 03/02/2024] Open
Abstract
Rhodococcus equi pneumonia is an important cause of mortality in foals worldwide. Virulent equine isolates harbour an 80-85kb virulence plasmid encoding six virulence-associated proteins (Vaps). VapA, the main virulence factor of this intracellular pathogen, is known to be a cell surface protein that creates an intracellular niche for R. equi growth. In contrast, VapC, VapD and VapE are secreted into the intracellular milieu. Although these Vaps share very high degree of sequence identity in the C-terminal domain, the N-terminal domain (N-domain) of VapA is distinct. It has been proposed that this domain plays a role in VapA surface localization but no direct experimental data provides support to such hypothesis. In this work, we employed R. equi 103S harbouring an unmarked deletion of vapA (R. equi ΔvapA) as the genetic background to express C-terminal Strep-tagged Vap-derivatives integrated in the chromosome. The surface localization of these proteins was assessed by flow cytometry using the THE2122;-NWSHPQFEK Tag FITC-antibody. We show that VapA is the only cell surface Vap encoded in the virulence plasmid. We present compelling evidence for the role of the N-terminal domain of VapA on cell surface localization using fusion proteins in which the N-domain of VapD was exchanged with the N-terminus of VapA. Lastly, using an N-terminally Strep-tagged VapA, we found that the N-terminus of VapA is exposed to the extracellular environment. Given the lack of a lipobox in VapA and the exposure of the N-terminal Strep-tag, it is possible that VapA localization on the cell surface is mediated by interactions between the N-domain and components of the cell surface. We discuss the implications of this work on the light of the recent discovery that soluble recombinant VapA added to the extracellular medium functionally complement the loss of VapA.
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Affiliation(s)
- Raúl Miranda-CasoLuengo
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Dublin, Ireland
| | - Zeynep Yerlikaya
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Dublin, Ireland
- Department of Microbiology, School of Veterinary Medicine, Firat University, Elazığ, Türkiye
| | - Haixia Luo
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Dublin, Ireland
| | - Cheng Cheng
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Dublin, Ireland
| | - Alfonso Blanco
- Flow Cytometry Core Technology, UCD Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Dublin, Ireland
| | - Albert Haas
- Institute for Cell Biology, University of Bonn, Bonn, Germany
| | - Wim G. Meijer
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Dublin, Ireland
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Haubenthal T, Hansen P, Krämer I, Gindt M, Jünger-Leif A, Utermöhlen O, Haas A. Specific preadaptations of Rhodococcus equi cooperate with its Virulence-associated protein A during macrophage infection. Mol Microbiol 2023; 119:285-301. [PMID: 36627747 DOI: 10.1111/mmi.15026] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/03/2023] [Accepted: 01/04/2023] [Indexed: 01/12/2023]
Abstract
Gram-positive Rhodococcus equi (Prescotella equi) is a lung pathogen of foals and immunocompromised humans. Intra-macrophage multiplication requires production of the bacterial Virulence-associated protein A (VapA) which is released into the phagosome lumen. VapA pH-neutralizes intracellular compartments allowing R. equi to multiply in an atypical macrophage phagolysosome. Here, we show that VapA does not support intra-macrophage growth of several other bacterial species demonstrating that only few bacteria have the specific preadaptations needed to profit from VapA. We show that the closest relative of R. equi, environmental Rhodococcus defluvii (Prescotella defluvii), does not multiply in macrophages at 37°C even when VapA is present because of its thermosensitivity but it does so once the infection temperature is lowered providing rare experimental evidence for 'thermal restriction'. Using growth experiments with isolated macrophage lysosomes and modified infection schemes we provide evidence that R. equi resists the attack by phagolysosome contents at low pH for several hours. During this time, R. equi produces and secretes VapA which enables it to grow at the expense of lysosome constituents. We present arguments that, under natural infection conditions, R. equi is VapA-less during the initial encounter with the host. This has important implications for vaccine development.
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Affiliation(s)
| | - Philipp Hansen
- Institute for Cell Biology, University of Bonn, Bonn, Germany
| | - Ina Krämer
- Institute for Cell Biology, University of Bonn, Bonn, Germany
| | - Mélanie Gindt
- Institute for Cell Biology, University of Bonn, Bonn, Germany
| | | | - Olaf Utermöhlen
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Germany
| | - Albert Haas
- Institute for Cell Biology, University of Bonn, Bonn, Germany
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Abstract
Pollution with microplastic has become a prime environmental concern. The various ways in which human-made polymers and microorganisms interact are little understood, and this is particularly true for microplastic and pathogenic microorganisms. Previous reports demonstrated that expression of central virulence-associated protein A (VapA) of the pathogenic bacterium Rhodococcus equi is shut off at 30°C, whereas it is strongly expressed at 37°C, a temperature which may serve as an intrahost cue. Here, we show that cultivation at 30°C in disposable plastic tubes increases mRNA levels of vapA 70-fold compared to growth in conventional glass tubes. Strong expression of vapA in plastic tubes does not seem to be caused by a compound leaching from plastic but rather by tube surface properties. Expression stimulation during growth in plastic is regulated by the R. equi transcription regulators VirR and VirS, indicating that plastic-induced vapA expression is (co)regulated through the canonical vapA expression pathway. Our observations have important implications for the future analysis and assessment of environmental microplastic contaminations in that they show that, in principle, contact of pathogens with environmental plastic can increase their virulence. IMPORTANCE Millions of tons small plastic pieces (microplastic) find their way into the environment every year. They pose digestive and toxicity problems to various life forms in soil, freshwater, and seawater. Additionally, microplastic offers an opportunity for microorganisms to attach and to become an important part of a “plastisphere community.” The significance of our study lies in the documentation of a sharp increase in production of a central virulence factor by a bacterial pathogen when the bacterium is in touch with certain makes of plastic. Although this feature may not reflect an increased health risk in case of this particular soilborne pathogen, our data disclose a new facet of how microplastics can endanger life.
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MacArthur I, Anastasi E, Alvarez S, Scortti M, Vázquez-Boland JA. Comparative Genomics of Rhodococcus equi Virulence Plasmids Indicates Host-Driven Evolution of the vap Pathogenicity Island. Genome Biol Evol 2017; 9:1241-1247. [PMID: 28369330 PMCID: PMC5434932 DOI: 10.1093/gbe/evx057] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2017] [Indexed: 01/16/2023] Open
Abstract
The conjugative virulence plasmid is a key component of the Rhodococcus equi accessory genome essential for pathogenesis. Three host-associated virulence plasmid types have been identified: the equine pVAPA and porcine pVAPB circular variants, and the linear pVAPN found in bovine (ruminant) isolates. We recently characterized the R. equi pangenome (Anastasi E, et al. 2016. Pangenome and phylogenomic analysis of the pathogenic actinobacterium Rhodococcus equi. Genome Biol Evol. 8:3140–3148.) and we report here the comparative analysis of the virulence plasmid genomes. Plasmids within each host-associated type were highly similar despite their diverse origins. Variation was accounted for by scattered single nucleotide polymorphisms and short nucleotide indels, while larger indels—mostly in the plasticity region near the vap pathogencity island (PAI)—defined plasmid genomic subtypes. Only one of the plasmids analyzed, of pVAPN type, was exceptionally divergent due to accumulation of indels in the housekeeping backbone. Each host-associated plasmid type carried a unique PAI differing in vap gene complement, suggesting animal host-specific evolution of the vap multigene family. Complete conservation of the vap PAI was observed within each host-associated plasmid type. Both diversity of host-associated plasmid types and clonality of specific chromosomal-plasmid genomic type combinations were observed within the same R. equi phylogenomic subclade. Our data indicate that the overall strong conservation of the R. equi host-associated virulence plasmids is the combined result of host-driven selection, lateral transfer between strains, and geographical spread due to international livestock exchanges.
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Affiliation(s)
- Iain MacArthur
- Division of Infection and Immunity, The Roslin Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Elisa Anastasi
- Division of Infection and Immunity, The Roslin Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Sonsiray Alvarez
- Division of Infection and Immunity, The Roslin Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Mariela Scortti
- Division of Infection and Immunity, The Roslin Institute, University of Edinburgh, Edinburgh, United Kingdom.,Edinburgh Medical School (Biomedical Sciences), University of Edinburgh, Edinburgh, United Kingdom
| | - José A Vázquez-Boland
- Division of Infection and Immunity, The Roslin Institute, University of Edinburgh, Edinburgh, United Kingdom.,Edinburgh Medical School (Biomedical Sciences), University of Edinburgh, Edinburgh, United Kingdom.,Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
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Functional characterization of the Mycobacterium abscessus genome coupled with condition specific transcriptomics reveals conserved molecular strategies for host adaptation and persistence. BMC Genomics 2016; 17:553. [PMID: 27495169 PMCID: PMC4974804 DOI: 10.1186/s12864-016-2868-y] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 06/30/2016] [Indexed: 11/10/2022] Open
Abstract
Background Mycobacterium abscessus subsp. abscessus (MAB) is a highly drug resistant mycobacterium and the most common respiratory pathogen among the rapidly growing non-tuberculous mycobacteria. MAB is also one of the most deadly of the emerging cystic fibrosis (CF) pathogens requiring prolonged treatment with multiple antibiotics. In addition to its “mycobacterial” virulence genes, the genome of MAB harbours a large accessory genome, presumably acquired via lateral gene transfer including homologs shared with the CF pathogens Pseudomonas aeruginosa and Burkholderia cepacia. While multiple genome sequences are available there is little functional genomics data available for this important pathogen. Results We report here the first multi-omics approach to characterize the primary transcriptome, coding potential and potential regulatory regions of the MAB genome utilizing differential RNA sequencing (dRNA-seq), RNA-seq, Ribosome profiling and LC-MS proteomics. In addition we attempt to address the genomes contribution to the molecular systems that underlie MAB’s adaptation and persistence in the human host through an examination of MABs transcriptional response to a number of clinically relevant conditions. These include hypoxia, exposure to sub-inhibitory concentrations of antibiotics and growth in an artificial sputum designed to mimic the conditions within the cystic fibrosis lung. Conclusions Our integrated map provides the first comprehensive view of the primary transcriptome of MAB and evidence for the translation of over one hundred new short open reading frames (sORFs). Our map will act as a resource for ongoing functional genomics characterization of MAB and our transcriptome data from clinically relevant stresses informs our understanding of MAB’s adaptation to life in the CF lung. MAB’s adaptation to growth in artificial CF sputum highlights shared metabolic strategies with other CF pathogens including P. aeruginosa and mirrors the transcriptional responses that lead to persistence in mycobacteria. These strategies include an increased reliance on amino acid metabolism, and fatty acid catabolism and highlights the relevance of the glyoxylate shunt to growth in the CF lung. Our data suggests that, similar to what is seen in chronically persisting P. aeruginosa, progression towards a biofilm mode of growth would play a more prominent role in a longer-term MAB infection. Finally, MAB’s transcriptional response to antibiotics highlights the role of antibiotic modifications enzymes, active transport and the evolutionarily conserved WhiB7 driven antibiotic resistance regulon. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2868-y) contains supplementary material, which is available to authorized users.
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Kakuda T, Miyazaki S, Hagiuda H, Takai S. Transcriptional regulation by VirR and VirS of members of the Rhodococcus equi virulence-associated protein multigene family. Microbiol Immunol 2016; 59:495-9. [PMID: 26094962 DOI: 10.1111/1348-0421.12277] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 05/18/2015] [Accepted: 06/17/2015] [Indexed: 11/30/2022]
Abstract
A virulence plasmid of Rhodococcus equi harbors the vap mutigene family. Here it is shown that transcription of vap gene family members other than vapA (vapD, vapE and vapG) is regulated by temperature and pH and abolished when either virS or virR is deleted. Expression of VirS in the absence of functional VirR was found to increase the transcription of vap genes to the amount expressed in the presence of VirR. These findings suggest that transcription of vap genes is regulated by VirS and that VirR is involved in the mechanism of transcriptional responses to temperature and pH.
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Affiliation(s)
- Tsutomu Kakuda
- Laboratory of Animal Hygiene, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada Aomori, 034-8628, Japan
| | - Shiko Miyazaki
- Laboratory of Animal Hygiene, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada Aomori, 034-8628, Japan
| | - Hirofumi Hagiuda
- Laboratory of Animal Hygiene, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada Aomori, 034-8628, Japan
| | - Shinji Takai
- Laboratory of Animal Hygiene, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada Aomori, 034-8628, Japan
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Transcriptome reprogramming by plasmid-encoded transcriptional regulators is required for host niche adaption of a macrophage pathogen. Infect Immun 2015; 83:3137-45. [PMID: 26015480 DOI: 10.1128/iai.00230-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 05/18/2015] [Indexed: 11/20/2022] Open
Abstract
Rhodococcus equi is a facultative intracellular pathogen of macrophages, relying on the presence of a conjugative virulence plasmid harboring a 21-kb pathogenicity island (PAI) for growth in host macrophages. The PAI encodes a family of 6 virulence-associated proteins (Vaps) in addition to 20 other proteins. The contribution of these to virulence has remained unclear. We show that the presence of only 3 virulence plasmid genes (of 73 in total) is required and sufficient for intracellular growth. These include a single vap family member, vapA, and two PAI-located transcriptional regulators, virR and virS. Both transcriptional regulators are essential for wild-type-level expression of vapA, yet vapA expression alone is not sufficient to allow intracellular growth. A whole-genome microarray analysis revealed that VirR and VirS substantially integrate themselves into the chromosomal regulatory network, significantly altering the transcription of 18% of all chromosomal genes. This pathoadaptation involved significant enrichment of select gene ontologies, in particular, enrichment of genes involved in transport processes, energy production, and cellular metabolism, suggesting a major change in cell physiology allowing the bacterium to grow in the hostile environment of the host cell. The results suggest that following the acquisition of the virulence plasmid by an avirulent ancestor of R. equi, coevolution between the plasmid and the chromosome took place, allowing VirR and VirS to regulate the transcription of chromosomal genes in a process that ultimately promoted intracellular growth. Our findings suggest a mechanism for cooption of existing chromosomal traits during the evolution of a pathogenic bacterium from an avirulent saprophyte.
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An Invertron-Like Linear Plasmid Mediates Intracellular Survival and Virulence in Bovine Isolates of Rhodococcus equi. Infect Immun 2015; 83:2725-37. [PMID: 25895973 DOI: 10.1128/iai.00376-15] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 04/16/2015] [Indexed: 12/16/2022] Open
Abstract
We report a novel host-associated virulence plasmid in Rhodococcus equi, pVAPN, carried by bovine isolates of this facultative intracellular pathogenic actinomycete. Surprisingly, pVAPN is a 120-kb invertron-like linear replicon unrelated to the circular virulence plasmids associated with equine (pVAPA) and porcine (pVAPB variant) R. equi isolates. pVAPN is similar to the linear plasmid pNSL1 from Rhodococcus sp. NS1 and harbors six new vap multigene family members (vapN to vapS) in a vap pathogenicity locus presumably acquired via en bloc mobilization from a direct predecessor of equine pVAPA. Loss of pVAPN rendered R. equi avirulent in macrophages and mice. Mating experiments using an in vivo transconjugant selection strategy demonstrated that pVAPN transfer is sufficient to confer virulence to a plasmid-cured R. equi recipient. Phylogenetic analyses assigned the vap multigene family complement from pVAPN, pVAPA, and pVAPB to seven monophyletic clades, each containing plasmid type-specific allelic variants of a precursor vap gene carried by the nearest vap island ancestor. Deletion of vapN, the predicted "bovine-type" allelic counterpart of vapA, essential for virulence in pVAPA, abrogated pVAPN-mediated intramacrophage proliferation and virulence in mice. Our findings support a model in which R. equi virulence is conferred by host-adapted plasmids. Their central role is mediating intracellular proliferation in macrophages, promoted by a key vap determinant present in the common ancestor of the plasmid-specific vap islands, with host tropism as a secondary trait selected during coevolution with specific animal species.
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Okoko T, Blagova EV, Whittingham JL, Dover LG, Wilkinson AJ. Structural characterisation of the virulence-associated protein VapG from the horse pathogen Rhodococcus equi. Vet Microbiol 2015; 179:42-52. [PMID: 25746683 PMCID: PMC4518536 DOI: 10.1016/j.vetmic.2015.01.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 01/30/2015] [Accepted: 01/31/2015] [Indexed: 01/20/2023]
Abstract
The 3-dimensional structure of a Rhodococcus equi virulence protein was determined. VapG comprises a closed beta barrel domain preceded by a natively disordered region. The structures of VapB, VapD and VapG are closely superimposable. The VAP structures lack recognisable ligand or protein binding sites. Phagosome-induced conformational changes may be required for virulence.
Virulence and host range in Rhodococcus equi depends on the variable pathogenicity island of their virulence plasmids. Notable gene products are a family of small secreted virulence-associated proteins (Vaps) that are critical to intramacrophagic proliferation. Equine-adapted strains, which cause severe pyogranulomatous pneumonia in foals, produce a cell-associated VapA that is necessary for virulence, alongside five other secreted homologues. In the absence of biochemical insight, attention has turned to the structures of these proteins to develop a functional hypothesis. Recent studies have described crystal structures for VapD and a truncate of the VapA orthologue of porcine-adapted strains, VapB. Here, we crystallised the full-length VapG and determined its structure by molecular replacement. Electron density corresponding to the N-terminal domain was not visible suggesting that it is disordered. The protein core adopted a compact elliptical, anti-parallel β-barrel fold with β1–β2–β3–β8–β5–β6–β7–β4 topology decorated by a single peripheral α-helix unique to this family. The high glycine content of the protein allows close packing of secondary structural elements. Topologically, the surface has no indentations that indicate a nexus for molecular interactions. The distribution of polar and apolar groups on the surface of VapG is markedly uneven. One-third of the surface is dominated by exposed apolar side-chains, with no ionisable and only four polar side-chains exposed, giving rise to an expansive flat hydrophobic surface. Other surface regions are more polar, especially on or near the α-helix and a belt around the centre of the β-barrel. Possible functional significance of these recent structures is discussed.
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Affiliation(s)
- Tebekeme Okoko
- Department of Applied Sciences, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK
| | - Elena V Blagova
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
| | - Jean L Whittingham
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Lynn G Dover
- Department of Applied Sciences, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK
| | - Anthony J Wilkinson
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
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Whittingham JL, Blagova EV, Finn CE, Luo H, Miranda-CasoLuengo R, Turkenburg JP, Leech AP, Walton PH, Murzin AG, Meijer WG, Wilkinson AJ. Structure of the virulence-associated protein VapD from the intracellular pathogen Rhodococcus equi. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:2139-51. [PMID: 25084333 PMCID: PMC4118825 DOI: 10.1107/s1399004714012632] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 05/30/2014] [Indexed: 01/17/2023]
Abstract
Rhodococcus equi is a multi-host pathogen that infects a range of animals as well as immune-compromised humans. Equine and porcine isolates harbour a virulence plasmid encoding a homologous family of virulence-associated proteins associated with the capacity of R. equi to divert the normal processes of endosomal maturation, enabling bacterial survival and proliferation in alveolar macrophages. To provide a basis for probing the function of the Vap proteins in virulence, the crystal structure of VapD was determined. VapD is a monomer as determined by multi-angle laser light scattering. The structure reveals an elliptical, compact eight-stranded β-barrel with a novel strand topology and pseudo-twofold symmetry, suggesting evolution from an ancestral dimer. Surface-associated octyl-β-D-glucoside molecules may provide clues to function. Circular-dichroism spectroscopic analysis suggests that the β-barrel structure is preceded by a natively disordered region at the N-terminus. Sequence comparisons indicate that the core folds of the other plasmid-encoded virulence-associated proteins from R. equi strains are similar to that of VapD. It is further shown that sequences encoding putative R. equi Vap-like proteins occur in diverse bacterial species. Finally, the functional implications of the structure are discussed in the light of the unique structural features of VapD and its partial structural similarity to other β-barrel proteins.
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Affiliation(s)
- Jean L. Whittingham
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Elena V. Blagova
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Ciaran E. Finn
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Haixia Luo
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Raúl Miranda-CasoLuengo
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Johan P. Turkenburg
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Andrew P. Leech
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Paul H. Walton
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Alexey G. Murzin
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, England
| | - Wim G. Meijer
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Anthony J. Wilkinson
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
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IcgA is a virulence factor of Rhodococcus equi that modulates intracellular growth. Infect Immun 2014; 82:1793-800. [PMID: 24549327 DOI: 10.1128/iai.01670-13] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Virulence of the intracellular pathogen Rhodococcus equi depends on a 21.3-kb pathogenicity island located on a conjugative plasmid. To date, the only nonregulatory pathogenicity island-encoded virulence factor identified is the cell envelope-associated VapA protein. Although the pathogenicity islands from porcine and equine R. equi isolates have undergone major rearrangements, the virR operon (virR-icgA-vapH-orf7-virS) is highly conserved in both, suggesting these genes play an important role in pathogenicity. VirR and VirS are transcriptional regulators controlling expression of pathogenicity island genes, including vapA. Here, we show that while vapH and orf7 are dispensable for intracellular growth of R. equi, deletion of icgA, formerly known as orf5, encoding a major facilitator superfamily transport protein, elicited an enhanced growth phenotype in macrophages and a significant reduction in macrophage viability, while extracellular growth in broth remained unaffected. Transcription of virS, located downstream of icgA, and vapA was not affected by the icgA deletion during growth in broth or in macrophages, showing that the enhanced growth phenotype caused by deletion of icgA was not mediated through abnormal transcription of these genes. Transcription of icgA increased 6-fold within 2 h following infection of macrophages and remained significantly higher 48 h postinfection compared to levels at the start of the infection. The major facilitator superfamily transport protein IcgA is the first factor identified in R. equi that negatively affects intracellular replication. Aside from VapA, it is only the second pathogenicity island-encoded structural protein shown to play a direct role in intracellular growth of this pathogenic actinomycete.
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Vázquez-Boland JA, Giguère S, Hapeshi A, MacArthur I, Anastasi E, Valero-Rello A. Rhodococcus equi: the many facets of a pathogenic actinomycete. Vet Microbiol 2013; 167:9-33. [PMID: 23993705 DOI: 10.1016/j.vetmic.2013.06.016] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 06/27/2013] [Indexed: 12/20/2022]
Abstract
Rhodococcus equi is a soil-dwelling pathogenic actinomycete that causes pulmonary and extrapulmonary pyogranulomatous infections in a variety of animal species and people. Young foals are particularly susceptible and develop a life-threatening pneumonic disease that is endemic at many horse-breeding farms worldwide. R. equi is a facultative intracellular parasite of macrophages that replicates within a modified phagocytic vacuole. Its pathogenicity depends on a virulence plasmid that promotes intracellular survival by preventing phagosome-lysosome fusion. Species-specific tropism of R. equi for horses, pigs and cattle appears to be determined by host-adapted virulence plasmid types. Molecular epidemiological studies of these plasmids suggest that human R. equi infection is zoonotic. Analysis of the recently determined R. equi genome sequence has identified additional virulence determinants on the bacterial chromosome. This review summarizes our current understanding of the clinical aspects, biology, pathogenesis and immunity of this fascinating microbe with plasmid-governed infectivity.
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Affiliation(s)
- José A Vázquez-Boland
- Microbial Pathogenesis Unit, School of Biomedical Sciences and Edinburgh Infectious Diseases, University of Edinburgh, Edinburgh EH9 3JT, UK; Grupo de Patogenómica Bacteriana, Facultad de Veterinaria, Universidad de León, 24071 León, Spain.
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Miranda-CasoLuengo AA, Miranda-CasoLuengo R, Lieggi NT, Luo H, Simpson JC, Meijer WG. A real-time impedance based method to assess Rhodococcus equi virulence. PLoS One 2013; 8:e60612. [PMID: 23555995 PMCID: PMC3610927 DOI: 10.1371/journal.pone.0060612] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 02/28/2013] [Indexed: 11/19/2022] Open
Abstract
Rhodococcus equi is a facultative intracellular pathogen of macrophages and the causative agent of foal pneumonia. R. equi virulence is usually assessed by analyzing intracellular growth in macrophages by enumeration of bacteria following cell lysis, which is time consuming and does not allow for a high throughput analysis. This paper describes the use of an impedance based real-time method to characterize proliferation of R. equi in macrophages, using virulent and attenuated strains lacking the vapA gene or virulence plasmid. Image analysis suggested that the time-dependent cell response profile (TCRP) is governed by cell size and roundness as well as cytoxicity of infecting R. equi strains. The amplitude and inflection point of the resulting TCRP were dependent on the multiplicity of infection as well as virulence of the infecting strain, thus distinguishing between virulent and attenuated strains.
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Affiliation(s)
| | - Raúl Miranda-CasoLuengo
- UCD School of Biomolecular and Biomedical Science and Conway Institute, University College Dublin, Dublin, Ireland
| | - Nora T. Lieggi
- UCD School of Biology and Environmental Science and Conway Institute, University College Dublin, Dublin, Ireland
| | - Haixia Luo
- UCD School of Biomolecular and Biomedical Science and Conway Institute, University College Dublin, Dublin, Ireland
| | - Jeremy C. Simpson
- UCD School of Biology and Environmental Science and Conway Institute, University College Dublin, Dublin, Ireland
| | - Wim G. Meijer
- UCD School of Biomolecular and Biomedical Science and Conway Institute, University College Dublin, Dublin, Ireland
- * E-mail:
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