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He H, Pramanik AS, Swanson SK, Johnson DK, Florens L, Zückert WR. A Borrelia burgdorferi LptD homolog is required for flipping of surface lipoproteins through the spirochetal outer membrane. Mol Microbiol 2023; 119:752-767. [PMID: 37170643 PMCID: PMC10330739 DOI: 10.1111/mmi.15072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 04/24/2023] [Accepted: 04/25/2023] [Indexed: 05/13/2023]
Abstract
Borrelia spirochetes are unique among diderm bacteria in their lack of lipopolysaccharide (LPS) in the outer membrane (OM) and their abundance of surface-exposed lipoproteins with major roles in transmission, virulence, and pathogenesis. Despite their importance, little is known about how surface lipoproteins are translocated through the periplasm and the OM. Here, we characterized Borrelia burgdorferi BB0838, a distant homolog of the OM LPS assembly protein LptD. Using a CRISPR interference approach, we showed that BB0838 is required for cell growth and envelope stability. Upon BB0838 knockdown, surface lipoprotein OspA was retained in the inner leaflet of the OM, as determined by its inaccessibility to in situ proteolysis but its presence in OM vesicles. The topology of the OM porin/adhesin P66 remained unaffected. Quantitative mass spectrometry of the B. burgdorferi membrane-associated proteome confirmed the selective periplasmic retention of surface lipoproteins under BB0838 knockdown conditions. Additional analysis identified a single in situ protease-accessible BB0838 peptide that mapped to a predicted β-barrel surface loop. Alphafold Multimer modeled a B. burgdorferi LptB2 FGCAD complex spanning the periplasm. Together, this suggests that BB0838/LptDBb facilitates the essential terminal step in spirochetal surface lipoprotein secretion, using an orthologous OM component of a pathway that secretes LPS in proteobacteria.
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Affiliation(s)
- Huan He
- University of Kansas School of Medicine, Department of Microbiology, Molecular Genetics and Immunology, Kansas City, Kansas, USA
| | - Ankita S. Pramanik
- University of Kansas School of Medicine, Department of Microbiology, Molecular Genetics and Immunology, Kansas City, Kansas, USA
| | | | - David K. Johnson
- University of Kansas, Computational Chemical Biology Core, Lawrence, Kansas, USA
| | - Laurence Florens
- Stowers Institute for Medical Research, Kansas City, Missouri, USA
| | - Wolfram R. Zückert
- University of Kansas School of Medicine, Department of Microbiology, Molecular Genetics and Immunology, Kansas City, Kansas, USA
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2
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Bowen HG, Kenedy MR, Johnson DK, MacKerell AD, Akins DR. Identification of a novel transport system in Borrelia burgdorferi that links the inner and outer membranes. Pathog Dis 2023; 81:ftad014. [PMID: 37385817 PMCID: PMC10353723 DOI: 10.1093/femspd/ftad014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/19/2023] [Accepted: 06/27/2023] [Indexed: 07/01/2023] Open
Abstract
Borrelia burgdorferi, the spirochete that causes Lyme disease, is a diderm organism that is similar to Gram-negative organisms in that it contains both an inner and outer membrane. Unlike typical Gram-negative organisms, however, B. burgdorferi lacks lipopolysaccharide (LPS). Using computational genome analyses and structural modeling, we identified a transport system containing six proteins in B. burgdorferi that are all orthologs to proteins found in the lipopolysaccharide transport (LPT) system that links the inner and outer membranes of Gram-negative organisms and is responsible for placing LPS on the surface of these organisms. While B. burgdorferi does not contain LPS, it does encode over 100 different surface-exposed lipoproteins and several major glycolipids, which like LPS are also highly amphiphilic molecules, though no system to transport these molecules to the borrelial surface is known. Accordingly, experiments supplemented by molecular modeling were undertaken to determine whether the orthologous LPT system identified in B. burgdorferi could transport lipoproteins and/or glycolipids to the borrelial outer membrane. Our combined observations strongly suggest that the LPT transport system does not transport lipoproteins to the surface. Molecular dynamic modeling, however, suggests that the borrelial LPT system could transport borrelial glycolipids to the outer membrane.
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Affiliation(s)
- Hannah G Bowen
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 1053 Oklahoma City, OK 73104, United States
| | - Melisha R Kenedy
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 1053 Oklahoma City, OK 73104, United States
| | - David K Johnson
- Shenkel Structural Biology Center, Molecular Graphics and Modeling Laboratory and the Computational Biology Core, University of Kansas, 2034 Becker Drive Lawrence, Kansas 66047, United States
| | - Alexander D MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore 20 North Pine Street Baltimore, Maryland 21201, United States
| | - Darrin R Akins
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 1053 Oklahoma City, OK 73104, United States
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3
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Kuhn HW, Lasseter AG, Adams PP, Avile CF, Stone BL, Akins DR, Jewett TJ, Jewett MW. BB0562 is a nutritional virulence determinant with lipase activity important for Borrelia burgdorferi infection and survival in fatty acid deficient environments. PLoS Pathog 2021; 17:e1009869. [PMID: 34415955 PMCID: PMC8409650 DOI: 10.1371/journal.ppat.1009869] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 09/01/2021] [Accepted: 08/05/2021] [Indexed: 11/22/2022] Open
Abstract
The Lyme disease spirochete Borrelia burgdorferi relies on uptake of essential nutrients from its host environments for survival and infection. Therefore, nutrient acquisition mechanisms constitute key virulence properties of the pathogen, yet these mechanisms remain largely unknown. In vivo expression technology applied to B. burgdorferi (BbIVET) during mammalian infection identified gene bb0562, which encodes a hypothetical protein comprised of a conserved domain of unknown function, DUF3996. DUF3996 is also found across adjacent encoded hypothetical proteins BB0563 and BB0564, suggesting the possibility that the three proteins could be functionally related. Deletion of bb0562, bb0563 and bb0564 individually and together demonstrated that bb0562 alone was important for optimal disseminated infection in immunocompetent and immunocompromised mice by needle inoculation and tick bite transmission. Moreover, bb0562 promoted spirochete survival during the blood dissemination phase of infection. Gene bb0562 was also found to be important for spirochete growth in low serum media and the growth defect of Δbb0562 B. burgdorferi was rescued with the addition of various long chain fatty acids, particularly oleic acid. In mammals, fatty acids are primarily stored in fat droplets in the form of triglycerides. Strikingly, addition of glyceryl trioleate, the triglyceride form of oleic acid, to the low serum media did not rescue the growth defect of the mutant, suggesting bb0562 may be important for the release of fatty acids from triglycerides. Therefore, we searched for and identified two canonical GXSXG lipase motifs within BB0562, despite the lack of homology to known bacterial lipases. Purified BB0562 demonstrated lipolytic activity dependent on the catalytic serine residues within the two motifs. In sum, we have established that bb0562 is a novel nutritional virulence determinant, encoding a lipase that contributes to fatty acid scavenge for spirochete survival in environments deficient in free fatty acids including the mammalian host. Borrelia burgdorferi, the causative agent of Lyme disease, has a small genome and lacks the ability to synthesize essential nutrients on its own as well as many of the virulence properties typical of bacterial pathogens that contribute to disease. The clinical manifestations of Lyme disease predominantly result from inflammation in response to the B. burgdorferi infection. Therefore, nutrient acquisition functions constitute key virulence factors for the pathogen. Fatty acids are critical components of B. burgdorferi membranes and lipoproteins, which the spirochete must scavenge from the host environment. Previously, through a genetic screen for B. burgdorferi genes that are expressed during mammalian infection we identified gene of unknown function, bb0562. Herein, we demonstrate that bb0562 encodes a lipase that plays a role in the release of free fatty acids from triglycerides. Furthermore, bb0562 contributes to B. burgdorferi survival and dissemination in the mammalian host. BB0562 is important for spirochete survival in environments low in free fatty acids thereby adding to B. burgdorferi’s arsenal of nutritional virulence determinants necessary for the pathogen to be maintained in the tick-mouse enzootic cycle and to cause disseminated disease.
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Affiliation(s)
- Hunter W. Kuhn
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Florida, United States of America
| | - Amanda G. Lasseter
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Florida, United States of America
| | - Philip P. Adams
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Florida, United States of America
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States of America
- Postdoctoral Research Associate Program, National Institute of General Medical Sciences, National Institute of Health, Bethesda, Maryland, United States of America
| | - Carlos Flores Avile
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Florida, United States of America
| | - Brandee L. Stone
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Darrin R. Akins
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Travis J. Jewett
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Florida, United States of America
| | - Mollie W. Jewett
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Florida, United States of America
- * E-mail:
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Bista S, Singh P, Bernard Q, Yang X, Hart T, Lin YP, Kitsou C, Singh Rana V, Zhang F, Linhardt RJ, Zhnag K, Akins DR, Hritzo L, Kim Y, Grab DJ, Dumler JS, Pal U. A Novel Laminin-Binding Protein Mediates Microbial-Endothelial Cell Interactions and Facilitates Dissemination of Lyme Disease Pathogens. J Infect Dis 2021; 221:1438-1447. [PMID: 31758693 DOI: 10.1093/infdis/jiz626] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 11/21/2019] [Indexed: 12/13/2022] Open
Abstract
Borrelia burgdorferi conserved gene products BB0406 and BB0405, members of a common B. burgdorferi paralogous gene family, share 59% similarity. Although both gene products can function as potential porins, only BB0405 is essential for infection. Here we show that, despite sequence homology and coexpression from the same operon, both proteins differ in their membrane localization attributes, antibody accessibility, and immunogenicity in mice. BB0406 is required for spirochete survival in mammalian hosts, particularly for the disseminated infection in distant organs. We identified that BB0406 interacts with laminin, one of the major constituents of the vascular basement membrane, and facilitates spirochete transmigration across host endothelial cell barriers. A better understanding of how B. burgdorferi transmigrates through dermal and tissue vascular barriers and establishes disseminated infections will contribute to the development of novel therapeutics to combat early infection.
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Affiliation(s)
- Sandhya Bista
- Department of Veterinary Medicine, University of Maryland, College Park, Maryland, USA
| | - Preeti Singh
- Department of Veterinary Medicine, University of Maryland, College Park, Maryland, USA
| | - Quentin Bernard
- Department of Veterinary Medicine, University of Maryland, College Park, Maryland, USA
| | - Xiuli Yang
- Department of Veterinary Medicine, University of Maryland, College Park, Maryland, USA
| | - Thomas Hart
- Department of Biological Science, State University of New York at Albany, Albany, New York, USA.,Division of Infectious Diseases, Wadsworth Center New York State Department of Health, Albany, New York, USA
| | - Yi-Pin Lin
- Department of Biological Science, State University of New York at Albany, Albany, New York, USA.,Department of Biomedical Science, State University of New York at Albany, Albany, New York, USA
| | - Chrysoula Kitsou
- Department of Veterinary Medicine, University of Maryland, College Park, Maryland, USA
| | - Vipin Singh Rana
- Department of Veterinary Medicine, University of Maryland, College Park, Maryland, USA
| | - Fuming Zhang
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Robert J Linhardt
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York, USA.,Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA.,Department of Biology and Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Kai Zhnag
- Oral and Craniofacial Molecular Biology, School of Dentistry, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Darrin R Akins
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Lucy Hritzo
- Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Yuri Kim
- Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Dennis J Grab
- Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - J Stephen Dumler
- Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Utpal Pal
- Department of Veterinary Medicine, University of Maryland, College Park, Maryland, USA.,Virginia-Maryland College of Veterinary Medicine, College Park, Maryland
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Abstract
Lyme disease (Lyme borreliosis) is a tick-borne, zoonosis of adults and children caused by genospecies of the Borrelia burgdorferi sensu lato complex. The ailment, widespread throughout the Northern Hemisphere, continues to increase globally due to multiple environmental factors, coupled with increased incursion of humans into habitats that harbor the spirochete. B. burgdorferi sensu lato is transmitted by ticks from the Ixodes ricinus complex. In North America, B. burgdorferi causes nearly all infections; in Europe, B. afzelii and B. garinii are most associated with human disease. The spirochete's unusual fragmented genome encodes a plethora of differentially expressed outer surface lipoproteins that play a seminal role in the bacterium's ability to sustain itself within its enzootic cycle and cause disease when transmitted to its incidental human host. Tissue damage and symptomatology (i.e., clinical manifestations) result from the inflammatory response elicited by the bacterium and its constituents. The deposition of spirochetes into human dermal tissue generates a local inflammatory response that manifests as erythema migrans (EM), the hallmark skin lesion. If treated appropriately and early, the prognosis is excellent. However, in untreated patients, the disease may present with a wide range of clinical manifestations, most commonly involving the central nervous system, joints, or heart. A small percentage (~10%) of patients may go on to develop a poorly defined fibromyalgia-like illness, post-treatment Lyme disease (PTLD) unresponsive to prolonged antimicrobial therapy. Below we integrate current knowledge regarding the ecologic, epidemiologic, microbiologic, and immunologic facets of Lyme disease into a conceptual framework that sheds light on the disorder that healthcare providers encounter.
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Affiliation(s)
- Justin D. Radolf
- Department of Medicine, UConn Health, Farmington, CT 06030, USA
- Department of Pediatrics, UConn Health, Farmington, CT 06030, USA
- Departments of Genetics and Genome Sciences, UConn Health, Farmington, CT 06030, USA
- Departments of Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030, USA
- Department of Immunology, UConn Health, Farmington, CT 06030, USA
| | - Klemen Strle
- Division of Infectious Diseases, Wadsworth Center, NY Department of Health, Albany NY, 12208, USA
| | - Jacob E. Lemieux
- Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Franc Strle
- Department of Infectious Diseases, University Medical Center Ljubljana, Ljubljana, Slovenia
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6
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Tkáčová Z, Pulzová LB, Mochnáčová E, Jiménez-Munguía I, Bhide K, Mertinková P, Majerová P, Kulkarni A, Kováč A, Bhide M. Identification of the proteins of Borrelia garinii interacting with human brain microvascular endothelial cells. Ticks Tick Borne Dis 2020; 11:101451. [PMID: 32360026 DOI: 10.1016/j.ttbdis.2020.101451] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 04/15/2020] [Accepted: 04/17/2020] [Indexed: 11/25/2022]
Abstract
Lyme borreliosis is one of the major tick-borne diseases in Europe. Events of the translocation of Borrelia across the blood-brain barrier (BBB) involve multiple interactions between borrelial surface proteins and receptors on the brain microvascular endothelial cells (hBMECs). In this study, we aimed to identify proteins of Borrelia that plausibly interact with hBMECs. The surface proteome of live Borrelia (a neuroinvasive strain of B. garinii) was crosslinked with biotin prior to its incubation with hBMECs. The interacting proteins were recovered by affinity purification, followed by SWATH-MS. Twenty-four interacting candidates were grouped into outer membrane proteins (n = 12) and inner membrane proteins (n = 12) based on the subcellular location as per the predictions of LocateP. Other algorithms like TMHMM 2.0 and LipoP, ontology search and literature review were subsequently applied to each of the identified protein candidates to shortlist the most probable interactors. Six proteins namely, LysM domain protein, BESBP-5, Antigen S1, CRASP-1 (Bg071), Erp23 protein and Mlp family Lipoprotein were selected to produce their recombinant forms and experimentally validate their interaction with hBMECs. All the recombinant proteins interacted with hBMECs, in ELISA and immunocytochemistry. We present here a high-throughput approach of generating a dataset of plausible borrelial ligands followed by a systematic bioinformatic pipeline to categorize the proteins for experimental validation.
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Affiliation(s)
- Zuzana Tkáčová
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Košice, Komenskeho 73, 04001, Kosice, Slovakia
| | - Lucia Borszéková Pulzová
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Košice, Komenskeho 73, 04001, Kosice, Slovakia
| | - Evelína Mochnáčová
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Košice, Komenskeho 73, 04001, Kosice, Slovakia
| | - Irene Jiménez-Munguía
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Košice, Komenskeho 73, 04001, Kosice, Slovakia
| | - Katarína Bhide
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Košice, Komenskeho 73, 04001, Kosice, Slovakia
| | - Patrícia Mertinková
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Košice, Komenskeho 73, 04001, Kosice, Slovakia
| | - Petra Majerová
- Institute of Neuroimmunology of Slovak Academy of Sciences, 84510, Bratislava, Slovakia
| | - Amod Kulkarni
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Košice, Komenskeho 73, 04001, Kosice, Slovakia; Institute of Neuroimmunology of Slovak Academy of Sciences, 84510, Bratislava, Slovakia
| | - Andrej Kováč
- Institute of Neuroimmunology of Slovak Academy of Sciences, 84510, Bratislava, Slovakia
| | - Mangesh Bhide
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Košice, Komenskeho 73, 04001, Kosice, Slovakia; Institute of Neuroimmunology of Slovak Academy of Sciences, 84510, Bratislava, Slovakia.
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7
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Abstract
Spirochetes form a separate phylum of bacteria with two membranes but otherwise unusual morphologies and envelope structures. Distinctive common features of Borrelia, Leptospira, and Treponema include the sequestration of flagella to the periplasm and thin peptidoglycan cell walls that are more closely associated with the inner membrane. Outer membrane compositions differ significantly between the genera. Leptospira most closely track Gram-negative bacteria due to the incorporation of lipopolysaccharides. Treponema and Borrelia outer membranes lack lipopolysaccharide, with treponemes expressing only a few outer membrane proteins and Borrelia displaying a dizzying diversity of abundant surface lipoproteins instead. Phylogenetic and experimental evidence indicates that spirochetes have adapted various modules of bacterial export and secretion pathways to build and maintain their envelopes. Export and insertion pathways in the inner membrane appear conserved, while spirochetal experimentation with various envelope architectures over time has led to variations in secretion pathways in the periplasm and outer membrane. Classical type I to III secretion systems have been identified, with demonstrated roles in drug efflux and export of flagellar proteins only. Unique activities of periplasmic proteases, including a C-terminal protease, are involved in maturation of some periplasmic proteins. Proper lipoprotein sorting within the periplasm appears to be dependent on functional Lol pathways that lack the outer membrane lipoprotein insertase LolB. The abundance of surface lipoproteins in Borrelia and detailed protein sorting studies suggest a lipoprotein secretion pathway that either extends Lol through the outer membrane or bypasses it altogether. Proteins can be released from cells in outer membrane vesicles or, rarely, as soluble proteins.
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Membrane directed expression in Escherichia coli of BBA57 and other virulence factors from the Lyme disease agent Borrelia burgdorferi. Sci Rep 2019; 9:17606. [PMID: 31772280 PMCID: PMC6879480 DOI: 10.1038/s41598-019-53830-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Accepted: 11/05/2019] [Indexed: 12/22/2022] Open
Abstract
Membrane-embedded proteins are critical to the establishment, survival and persistence in the host of the Lyme disease bacterium Borrelia burgdorferi (Bb), but to date, there are no solved structures of transmembrane proteins representing these attractive therapeutic targets. All available structures from the genus Borrelia represent proteins expressed without a membrane-targeting signal peptide, thus avoiding conserved pathways that modify, fold and assemble membrane protein complexes. Towards elucidating structure and function of these critical proteins, we directed translocation of eleven expression-optimized Bb virulence factors, including the signal sequence, to the Escherichia coli membrane, of which five, BBA57, HtrA, BB0238, BB0323, and DipA, were expressed with C-terminal His-tags. P66 was also expressed using the PelB signal sequence fused to maltose binding protein. Membrane-associated BBA57 lipoprotein was solubilized by non-ionic and zwitterionic detergents. We show BBA57 translocation to the outer membrane, purification at a level sufficient for structural studies, and evidence for an α-helical multimer. Previous studies showed multiple critical roles of BBA57 in transmission, joint arthritis, carditis, weakening immune responses, and regulating other Bb outer surface proteins. In describing the first purification of membrane-translocated BBA57, this work will support subsequent studies that reveal the precise mechanisms of this important Lyme disease virulence factor.
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9
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Caimano MJ, Groshong AM, Belperron A, Mao J, Hawley KL, Luthra A, Graham DE, Earnhart CG, Marconi RT, Bockenstedt LK, Blevins JS, Radolf JD. The RpoS Gatekeeper in Borrelia burgdorferi: An Invariant Regulatory Scheme That Promotes Spirochete Persistence in Reservoir Hosts and Niche Diversity. Front Microbiol 2019; 10:1923. [PMID: 31507550 PMCID: PMC6719511 DOI: 10.3389/fmicb.2019.01923] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 08/05/2019] [Indexed: 11/28/2022] Open
Abstract
Maintenance of Borrelia burgdorferi within its enzootic cycle requires a complex regulatory pathway involving the alternative σ factors RpoN and RpoS and two ancillary trans-acting factors, BosR and Rrp2. Activation of this pathway occurs within ticks during the nymphal blood meal when RpoS, the effector σ factor, transcribes genes required for tick transmission and mammalian infection. RpoS also exerts a 'gatekeeper' function by repressing σ70-dependent tick phase genes (e.g., ospA, lp6.6). Herein, we undertook a broad examination of RpoS functionality throughout the enzootic cycle, beginning with modeling to confirm that this alternative σ factor is a 'genuine' RpoS homolog. Using a novel dual color reporter system, we established at the single spirochete level that ospA is expressed in nymphal midguts throughout transmission and is not downregulated until spirochetes have been transmitted to a naïve host. Although it is well established that rpoS/RpoS is expressed throughout infection, its requirement for persistent infection has not been demonstrated. Plasmid retention studies using a trans-complemented ΔrpoS mutant demonstrated that (i) RpoS is required for maximal fitness throughout the mammalian phase and (ii) RpoS represses tick phase genes until spirochetes are acquired by a naïve vector. By transposon mutant screening, we established that bba34/oppA5, the only OppA oligopeptide-binding protein controlled by RpoS, is a bona fide persistence gene. Lastly, comparison of the strain 297 and B31 RpoS DMC regulons identified two cohorts of RpoS-regulated genes. The first consists of highly conserved syntenic genes that are similarly regulated by RpoS in both strains and likely required for maintenance of B. burgdorferi sensu stricto strains in the wild. The second includes RpoS-regulated plasmid-encoded variable surface lipoproteins ospC, dbpA and members of the ospE/ospF/elp, mlp, revA, and Pfam54 paralogous gene families, all of which have evolved via inter- and intra-strain recombination. Thus, while the RpoN/RpoS pathway regulates a 'core' group of orthologous genes, diversity within RpoS regulons of different strains could be an important determinant of reservoir host range as well as spirochete virulence.
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Affiliation(s)
- Melissa J. Caimano
- Department of Medicine, UConn Health, Farmington, CT, United States,Department of Pediatrics, UConn Health, Farmington, CT, United States,Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, United States,*Correspondence: Melissa J. Caimano,
| | | | - Alexia Belperron
- Department of Internal Medicine, Section of Rheumatology, Allergy and Immunology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Jialing Mao
- Department of Internal Medicine, Section of Rheumatology, Allergy and Immunology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Kelly L. Hawley
- Department of Pediatrics, UConn Health, Farmington, CT, United States,Division of Infectious Diseases and Immunology, Connecticut Children’s Medical Center, Hartford, CT, United States
| | - Amit Luthra
- Department of Medicine, UConn Health, Farmington, CT, United States
| | - Danielle E. Graham
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Christopher G. Earnhart
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA, United States
| | - Richard T. Marconi
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA, United States
| | - Linda K. Bockenstedt
- Department of Internal Medicine, Section of Rheumatology, Allergy and Immunology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Jon S. Blevins
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Justin D. Radolf
- Department of Medicine, UConn Health, Farmington, CT, United States,Department of Pediatrics, UConn Health, Farmington, CT, United States,Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, United States,Department of Genetics and Genome Science, UConn Health, Farmington, CT, United States,Department of Immunology, UConn Health, Farmington, CT, United States
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10
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Delineating Surface Epitopes of Lyme Disease Pathogen Targeted by Highly Protective Antibodies of New Zealand White Rabbits. Infect Immun 2019; 87:IAI.00246-19. [PMID: 31085705 DOI: 10.1128/iai.00246-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 05/07/2019] [Indexed: 11/20/2022] Open
Abstract
Lyme disease (LD), the most prevalent vector-borne illness in the United States and Europe, is caused by Borreliella burgdorferi No vaccine is available for humans. Dogmatically, B. burgdorferi can establish a persistent infection in the mammalian host (e.g., mice) due to a surface antigen, VlsE. This antigenically variable protein allows the spirochete to continually evade borreliacidal antibodies. However, our recent study has shown that the B. burgdorferi spirochete is effectively cleared by anti-B. burgdorferi antibodies of New Zealand White rabbits, despite the surface expression of VlsE. Besides homologous protection, the rabbit antibodies also cross-protect against heterologous B. burgdorferi spirochetes and significantly reduce the pathology of LD arthritis in persistently infected mice. Thus, this finding that NZW rabbits develop a unique repertoire of very potent antibodies targeting the protective surface epitopes, despite abundant VlsE, prompted us to identify the specificities of the protective rabbit antibodies and their respective targets. By applying subtractive reverse vaccinology, which involved the use of random peptide phage display libraries coupled with next-generation sequencing and our computational algorithms, repertoires of nonprotective (early) and protective (late) rabbit antibodies were identified and directly compared. Consequently, putative surface epitopes that are unique to the protective rabbit sera were mapped. Importantly, the relevance of newly identified protection-associated epitopes for their surface exposure has been strongly supported by prior empirical studies. This study is significant because it now allows us to systematically test the putative epitopes for their protective efficacy with an ultimate goal of selecting the most efficacious targets for development of a long-awaited LD vaccine.
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Locke JW. Complement Evasion in Borrelia spirochetes: Mechanisms and Opportunities for Intervention. Antibiotics (Basel) 2019; 8:antibiotics8020080. [PMID: 31200570 PMCID: PMC6627623 DOI: 10.3390/antibiotics8020080] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 12/22/2022] Open
Abstract
Lyme disease (LD) is an increasingly prevalent, climate change-accelerated, vector-borne infectious disease with significant morbidity and cost in a proportion of patients who experience ongoing symptoms after antibiotic treatment, a condition known as post-treatment Lyme disease syndrome (PTLDS). Spirochetal bacteria of Borrelia species are the causative agents of LD. These obligate parasites have evolved sophisticated immune evasion mechanisms, including the ability to defeat the innate immune system’s complement cascade. Research on complement function and Borrelia evasion mechanisms, focusing on human disease, is reviewed, highlighting opportunities to build on existing knowledge. Implications for the development of new antibiotic therapies having the potential to prevent or cure PTLDS are discussed. It is noted that a therapy enabling the complement system to effectively counter Borrelia might have lower cost and fewer side-effects and risks than broad-spectrum antibiotic use and could avert the need to develop and administer a vaccine.
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Affiliation(s)
- Jonathan W Locke
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
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Winslow C, Coburn J. Recent discoveries and advancements in research on the Lyme disease spirochete Borrelia burgdorferi. F1000Res 2019; 8. [PMID: 31214329 PMCID: PMC6545822 DOI: 10.12688/f1000research.18379.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/20/2019] [Indexed: 12/26/2022] Open
Abstract
This review highlights some of the highest-profile developments and advancements in the research on
Borrelia burgdorferi, the Lyme disease spirochete, that have emerged in the last two years. Particular emphasis is placed on the controversy surrounding genus nomenclature, antigenic variation at the
vlsE locus, genes involved in infectivity and virulence, membrane characteristics of
B. burgdorferi, and developments in experimental approaches.
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Affiliation(s)
- Christa Winslow
- Department of Microbiology and Immunology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
| | - Jenifer Coburn
- Department of Microbiology and Immunology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.,Department of Medicine, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
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Casjens SR, Di L, Akther S, Mongodin EF, Luft BJ, Schutzer SE, Fraser CM, Qiu WG. Primordial origin and diversification of plasmids in Lyme disease agent bacteria. BMC Genomics 2018; 19:218. [PMID: 29580205 PMCID: PMC5870499 DOI: 10.1186/s12864-018-4597-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 03/12/2018] [Indexed: 12/19/2022] Open
Abstract
Background With approximately one-third of their genomes consisting of linear and circular plasmids, the Lyme disease agent cluster of species has the most complex genomes among known bacteria. We report here a comparative analysis of plasmids in eleven Borreliella (also known as Borrelia burgdorferi sensu lato) species. Results We sequenced the complete genomes of two B. afzelii, two B. garinii, and individual B. spielmanii, B. bissettiae, B. valaisiana and B. finlandensis isolates. These individual isolates carry between seven and sixteen plasmids, and together harbor 99 plasmids. We report here a comparative analysis of these plasmids, along with 70 additional Borreliella plasmids available in the public sequence databases. We identify only one new putative plasmid compatibility type (the 30th) among these 169 plasmid sequences, suggesting that all or nearly all such types have now been discovered. We find that the linear plasmids in the non-B. burgdorferi species have undergone the same kinds of apparently random, chaotic rearrangements mediated by non-homologous recombination that we previously discovered in B. burgdorferi. These rearrangements occurred independently in the different species lineages, and they, along with an expanded chromosomal phylogeny reported here, allow the identification of several whole plasmid transfer events among these species. Phylogenetic analyses of the plasmid partition genes show that a majority of the plasmid compatibility types arose early, most likely before separation of the Lyme agent Borreliella and relapsing fever Borrelia clades, and this, with occasional cross species plasmid transfers, has resulted in few if any species-specific or geographic region-specific Borreliella plasmid types. Conclusions The primordial origin and persistent maintenance of the Borreliella plasmid types support their functional indispensability as well as evolutionary roles in facilitating genome diversity. The improved resolution of Borreliella plasmid phylogeny based on conserved partition-gene clusters will lead to better determination of gene orthology which is essential for prediction of biological function, and it will provide a basis for inferring detailed evolutionary mechanisms of Borreliella genomic variability including homologous gene and plasmid exchanges as well as non-homologous rearrangements. Electronic supplementary material The online version of this article (10.1186/s12864-018-4597-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sherwood R Casjens
- Division of Microbiology and Immunology, Pathology Department and Biology Department, University of Utah School of Medicine, Salt Lake City, UT, USA. .,Biology Department, University of Utah, Salt Lake City, UT, USA. .,Pathology Department, University of Utah School of Medicine, Room 2200K Emma Eccles Jones Medical Research Building, 15 North Medical Drive East, Salt Lake City, UT, 84112, USA.
| | - Lia Di
- Department of Biological Sciences and Center for Translational and Basic Research, Hunter College of the City University of New York, New York, NY, USA
| | - Saymon Akther
- Department of Biology, The Graduate Center, City University of New York, New York, NY, USA
| | - Emmanuel F Mongodin
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Benjamin J Luft
- Department of Medicine, Health Science Center, Stony Brook University, Stony Brook, NY, USA
| | - Steven E Schutzer
- Department of Medicine, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Claire M Fraser
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Wei-Gang Qiu
- Department of Biology, The Graduate Center, City University of New York, New York, NY, USA. .,Department of Biological Sciences and Center for Translational and Basic Research, Hunter College of the City University of New York, New York, NY, USA. .,Department of Physiology and Biophysics & Institute for Computational Biomedicine, Weil Cornell Medical College, New York, USA.
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Outer Membrane Proteins BB0405 and BB0406 Are Immunogenic, but Only BB0405 Is Required for Borrelia burgdorferi Infection. Infect Immun 2017; 85:IAI.00803-16. [PMID: 27920211 DOI: 10.1128/iai.00803-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 11/24/2016] [Indexed: 02/06/2023] Open
Abstract
We recently identified the Borrelia burgdorferi outer membrane protein (OMP) BB0406 and found that the gene encoding this OMP was cotranscribed with the gene encoding the OMP BB0405. Interestingly, BB0405 and BB0406 share 59% similarity and are grouped into the same B. burgdorferi paralogous gene family. Given their overall similarity, it is plausible that both OMPs have similar or overlapping functions in this pathogenic spirochete. BB0405 was recently shown to be required for mammalian infection despite the observations that BB0405 is poorly immunogenic and not recognized during mouse or human infection. BB0405 orthologs have also been shown to bind the complement regulator protein factor H. Therefore, to better elucidate the role of BB0405 and its paralog BB0406 during infection and in serum resistance, we examined both proteins in animal infection, factor H binding, and serum sensitivity assays. Our combined results suggest that BB0405- and BB0406-specific antibodies are borreliacidal and that both OMPs are immunogenic during nonhuman primate infection. Additionally, while BB0405 was found to be required for establishing mouse infection, BB0406 was not found to be essential for infectivity. In contrast to data from previous reports, however, neither OMP was found to bind human factor H or to be required for enhancing serum resistance of B. burgdorferi in vitro.
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