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Sanderlin AG, Kurka Margolis H, Meyer AF, Lamason RL. Cell-selective proteomics reveal novel effectors secreted by an obligate intracellular bacterial pathogen. Nat Commun 2024; 15:6073. [PMID: 39025857 PMCID: PMC11258249 DOI: 10.1038/s41467-024-50493-9] [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: 11/27/2023] [Accepted: 07/11/2024] [Indexed: 07/20/2024] Open
Abstract
Pathogenic bacteria secrete protein effectors to hijack host machinery and remodel their infectious niche. Rickettsia spp. are obligate intracellular bacteria that can cause life-threatening disease, but their absolute dependence on the host cell has impeded discovery of rickettsial effectors and their host targets. We implemented bioorthogonal non-canonical amino acid tagging (BONCAT) during R. parkeri infection to selectively label, isolate, and identify effectors delivered into the host cell. As the first use of BONCAT in an obligate intracellular bacterium, our screen more than doubles the number of experimentally validated effectors for the genus. The seven novel secreted rickettsial factors (Srfs) we identified include Rickettsia-specific proteins of unknown function that localize to the host cytoplasm, mitochondria, and ER. We further show that one such effector, SrfD, interacts with the host Sec61 translocon. Altogether, our work uncovers a diverse set of previously uncharacterized rickettsial effectors and lays the foundation for a deeper exploration of the host-pathogen interface.
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Affiliation(s)
- Allen G Sanderlin
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | - Abigail F Meyer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Rebecca L Lamason
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
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Mandel CG, Sanchez SE, Monahan CC, Phuklia W, Omsland A. Metabolism and physiology of pathogenic bacterial obligate intracellular parasites. Front Cell Infect Microbiol 2024; 14:1284701. [PMID: 38585652 PMCID: PMC10995303 DOI: 10.3389/fcimb.2024.1284701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 02/01/2024] [Indexed: 04/09/2024] Open
Abstract
Bacterial obligate intracellular parasites (BOIPs) represent an exclusive group of bacterial pathogens that all depend on invasion of a eukaryotic host cell to reproduce. BOIPs are characterized by extensive adaptation to their respective replication niches, regardless of whether they replicate within the host cell cytoplasm or within specialized replication vacuoles. Genome reduction is also a hallmark of BOIPs that likely reflects streamlining of metabolic processes to reduce the need for de novo biosynthesis of energetically costly metabolic intermediates. Despite shared characteristics in lifestyle, BOIPs show considerable diversity in nutrient requirements, metabolic capabilities, and general physiology. In this review, we compare metabolic and physiological processes of prominent pathogenic BOIPs with special emphasis on carbon, energy, and amino acid metabolism. Recent advances are discussed in the context of historical views and opportunities for discovery.
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Affiliation(s)
- Cameron G. Mandel
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
| | - Savannah E. Sanchez
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
| | - Colleen C. Monahan
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
| | - Weerawat Phuklia
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao People’s Democratic Republic
| | - Anders Omsland
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
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Riffaud CM, Rucks EA, Ouellette SP. Persistence of obligate intracellular pathogens: alternative strategies to overcome host-specific stresses. Front Cell Infect Microbiol 2023; 13:1185571. [PMID: 37284502 PMCID: PMC10239878 DOI: 10.3389/fcimb.2023.1185571] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 05/05/2023] [Indexed: 06/08/2023] Open
Abstract
In adapting to the intracellular niche, obligate intracellular bacteria usually undergo a reduction of genome size by eliminating genes not needed for intracellular survival. These losses can include, for example, genes involved in nutrient anabolic pathways or in stress response. Living inside a host cell offers a stable environment where intracellular bacteria can limit their exposure to extracellular effectors of the immune system and modulate or outright inhibit intracellular defense mechanisms. However, highlighting an area of vulnerability, these pathogens are dependent on the host cell for nutrients and are very sensitive to conditions that limit nutrient availability. Persistence is a common response shared by evolutionarily divergent bacteria to survive adverse conditions like nutrient deprivation. Development of persistence usually compromises successful antibiotic therapy of bacterial infections and is associated with chronic infections and long-term sequelae for the patients. During persistence, obligate intracellular pathogens are viable but not growing inside their host cell. They can survive for a long period of time such that, when the inducing stress is removed, reactivation of their growth cycles resumes. Given their reduced coding capacity, intracellular bacteria have adapted different response mechanisms. This review gives an overview of the strategies used by the obligate intracellular bacteria, where known, which, unlike model organisms such as E. coli, often lack toxin-antitoxin systems and the stringent response that have been linked to a persister phenotype and amino acid starvation states, respectively.
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Analysis of the Type 4 Effectome across the Genus Rickettsia. Int J Mol Sci 2022; 23:ijms232415513. [PMID: 36555155 PMCID: PMC9779031 DOI: 10.3390/ijms232415513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/05/2022] [Accepted: 12/06/2022] [Indexed: 12/13/2022] Open
Abstract
Rickettsia are obligate intracellular bacteria primarily carried by arthropod hosts. The genus Rickettsia contains several vertebrate pathogens vectored by hematophagous arthropods. Despite the potential for disease, our understanding of Rickettsias are limited by the difficulties associated with growing and manipulating obligate intracellular bacteria. To aid with this, our lab conducted an analysis of eight genomes and three plasmids from across the genus Rickettsia. Using OPT4e, a learning algorithm-based program designed to identify effector proteins secreted by the type 4 secretion system, we generated a putative effectome for the genus. We then consolidated effectors into homolog sets to identify effectors unique to Rickettsia with different life strategies or evolutionary histories. We also compared predicted effectors to non-effectors for differences in G+C content and gene splitting. Based on this analysis, we predicted 1571 effectors across the genus, resulting in 604 homolog sets. Each species had unique homolog sets, while 42 were present in all eight species analyzed. Effectors were flagged in association with pathogenic, tick and flea-borne Rickettsia. Predicted effectors also varied in G+C content and frequency of gene splitting as compared to non-effectors. Species effector repertoires show signs of expansion, degradation, and horizontal acquisition associated with lifestyle and lineage.
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Iron Reduction in Dermacentor andersoni Tick Cells Inhibits Anaplasma marginale Replication. Int J Mol Sci 2022; 23:ijms23073941. [PMID: 35409307 PMCID: PMC8999750 DOI: 10.3390/ijms23073941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 03/23/2022] [Accepted: 03/29/2022] [Indexed: 02/04/2023] Open
Abstract
Anaplasma spp. are obligate intracellular, tick-borne, bacterial pathogens that cause bovine and human anaplasmosis. We lack tools to prevent these diseases in part due to major knowledge gaps in our fundamental understanding of the tick-pathogen interface, including the requirement for and molecules involved in iron transport during tick colonization. We determine that iron is required for the pathogen Anaplasma marginale, which causes bovine anaplasmosis, to replicate in Dermacentor andersoni tick cells. Using bioinformatics and protein modeling, we identified three orthologs of the Gram-negative siderophore-independent iron uptake system, FbpABC. Am069, the A. marginale ortholog of FbpA, lacks predicted iron-binding residues according to the NCBI conserved domain database. However, according to protein modeling, the best structural orthologs of Am069 are iron transport proteins from Cyanobacteria and Campylobacterjejuni. We then determined that all three A. marginale genes are modestly differentially expressed in response to altered host cell iron levels, despite the lack of a Ferric uptake regulator or operon structure. This work is foundational for building a mechanistic understanding of iron uptake, which could lead to interventions to prevent bovine and human anaplasmosis.
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Williams V, Menon N, Bhatia P, Biswal M, Sreedharanunni S, Jayashree M, Nallasamy K. Hyperferritinemia in children hospitalized with scrub typhus. Trop Med Health 2021; 49:15. [PMID: 33597024 PMCID: PMC7890859 DOI: 10.1186/s41182-021-00304-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 02/01/2021] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Hyperferritinemia is increasingly associated with mortality in sepsis. Studies estimating the prevalence of hyperferritinemia in pediatric scrub typhus are limited. METHODS This was a secondary analysis of a prospective observational study (FERRIS) from a tertiary care teaching hospital in North India where 72 children with confirmed scrub typhus, 4 (5.5%) PCR positive, 55 (76.4%)-IgM ELISA positive, and 13 (18.1%)-both PCR and ELISA positive, were analyzed. Serum ferritin was measured in 62 children to identify the prevalence of hyperferritinemia and determine its association with mortality. RESULTS Hyperferritinemia (> 500 μg/L) was seen in 72.6% [n = 45] children; 26 (41.9%) were mild (500-2000 μg/L), 13 (21%) were moderate (2000-10,000 μg/L), and 6 (9.7%) were severe (> 10,000 μg/L). Early presentation to hospital (≤ 7 days of febrile illness) had more survivors than late presentation (> 7 days). Non-survivors had significantly higher PRISM III, PELOD-2, hyperlactatemia, hypoalbuminemia, organ dysfunction, need for mechanical ventilation, and need of RRT. Ferritin had poor sensitivity and specificity in predicting survival with AUC of 0.56. Organ dysfunction and risk scores as PRISM III, PELOD 2, and VIS at admission were better predictors with AUC (95% CI) of 0.72 (0.56, 0.89), 0.77 (0.63, 0.92), and 0.90 (0.78, 1.0) respectively. CONCLUSIONS Hyperferritinemia is common in scrub typhus but it did not predict survival. Organ dysfunction and risk scores were better predictors of mortality than ferritin.
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Affiliation(s)
- Vijai Williams
- Division of Pediatric Emergency and Intensive care, Department of Pediatrics, Advanced Pediatrics Centre, Postgraduate Institute of Medical Education & Research, Sector-12, Chandigarh, 160012, India
| | - Nisha Menon
- Division of Pediatric Emergency and Intensive care, Department of Pediatrics, Advanced Pediatrics Centre, Postgraduate Institute of Medical Education & Research, Sector-12, Chandigarh, 160012, India
| | - Prateek Bhatia
- Division of Pediatric Hematology, Department of Pediatrics, Advanced Pediatrics Centre, Postgraduate Institute of Medical Education & Research, Chandigarh, India
| | - Manisha Biswal
- Department of Medical Microbiology, Postgraduate Institute of Medical Education & Research, Chandigarh, India
| | - Sreejesh Sreedharanunni
- Department of Hematology, Postgraduate Institute of Medical Education & Research, Chandigarh, India
| | - Muralidharan Jayashree
- Division of Pediatric Emergency and Intensive care, Department of Pediatrics, Advanced Pediatrics Centre, Postgraduate Institute of Medical Education & Research, Sector-12, Chandigarh, 160012, India
| | - Karthi Nallasamy
- Division of Pediatric Emergency and Intensive care, Department of Pediatrics, Advanced Pediatrics Centre, Postgraduate Institute of Medical Education & Research, Sector-12, Chandigarh, 160012, India.
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Narra HP, Sahni A, Alsing J, Schroeder CLC, Golovko G, Nia AM, Fofanov Y, Khanipov K, Sahni SK. Comparative transcriptomic analysis of Rickettsia conorii during in vitro infection of human and tick host cells. BMC Genomics 2020; 21:665. [PMID: 32977742 PMCID: PMC7519539 DOI: 10.1186/s12864-020-07077-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 09/17/2020] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Pathogenic Rickettsia species belonging to the spotted fever group are arthropod-borne, obligate intracellular bacteria which exhibit preferential tropism for host microvascular endothelium in the mammalian hosts, resulting in disease manifestations attributed primarily to endothelial damage or dysfunction. Although rickettsiae are known to undergo evolution through genomic reduction, the mechanisms by which these pathogens regulate their transcriptome to ensure survival in tick vectors and maintenance by transovarial/transstadial transmission, in contrast to their ability to cause debilitating infections in human hosts remain unknown. In this study, we compare the expression profiles of rickettsial sRNAome/transcriptome and determine the transcriptional start sites (TSSs) of R. conorii transcripts during in vitro infection of human and tick host cells. RESULTS We performed deep sequencing on total RNA from Amblyomma americanum AAE2 cells and human microvascular endothelial cells (HMECs) infected with R. conorii. Strand-specific RNA sequencing of R. conorii transcripts revealed the expression 32 small RNAs (Rc_sR's), which were preferentially expressed above the limit of detection during tick cell infection, and confirmed the expression of Rc_sR61, sR71, and sR74 by quantitative RT-PCR. Intriguingly, a total of 305 and 132 R. conorii coding genes were differentially upregulated (> 2-fold) in AAE2 cells and HMECs, respectively. Further, enrichment for primary transcripts by treatment with Terminator 5'-Phosphate-dependent Exonuclease resulted in the identification of 3903 and 2555 transcription start sites (TSSs), including 214 and 181 primary TSSs in R. conorii during the infection to tick and human host cells, respectively. Seventy-five coding genes exhibited different TSSs depending on the host environment. Finally, we also observed differential expression of 6S RNA during host-pathogen and vector-pathogen interactions in vitro, implicating an important role for this noncoding RNA in the regulation of rickettsial transcriptome depending on the supportive host niche. CONCLUSIONS In sum, the findings of this study authenticate the presence of novel Rc_sR's in R. conorii, reveal the first evidence for differential expression of coding transcripts and utilization of alternate transcriptional start sites depending on the host niche, and implicate a role for 6S RNA in the regulation of coding transcriptome during tripartite host-pathogen-vector interactions.
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Affiliation(s)
- Hema P Narra
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
| | - Abha Sahni
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Jessica Alsing
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Casey L C Schroeder
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - George Golovko
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Anna M Nia
- Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Yuriy Fofanov
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Kamil Khanipov
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Sanjeev K Sahni
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
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Comparative Analysis of Infection by Rickettsia rickettsii Sheila Smith and Taiaçu Strains in a Murine Model. Pathogens 2020; 9:pathogens9090744. [PMID: 32927666 PMCID: PMC7557639 DOI: 10.3390/pathogens9090744] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 08/28/2020] [Accepted: 09/07/2020] [Indexed: 11/22/2022] Open
Abstract
Rocky Mountain spotted fever (RMSF) is a life-threatening tick-borne disease caused by Rickettsia rickettsii, which is widely distributed throughout the Americas. Over 4000 cases of RMSF are recorded annually in the United States, while only around 100 cases are reported in Brazil. Conversely, while case fatality rates in the United States oscillate around 5%, in Brazil they can surpass 70%, suggesting that differences in tick vectoring capacity, population sensitivity, and/or variability in virulence of the rickettsial strains may exist. In this study, we compared the susceptibility of C3H/HeN mice to two highly virulent strains of R. rickettsii, one from the United States (Sheila Smith) and the other from Brazil (Taiaçu). Animals inoculated with the Taiaçu strain succumbed to infection earlier and exhibited severe histological lesions in both liver and spleen sooner than mice infected with the Sheila Smith strain. These differences in survival and signs of the disease are not related to a greater proliferation of the Taiaçu strain, as there were no significant differences in the rickettsial load in mice tissues inoculated with either strain. The present study is the first step to experimentally assess differences in fatality rates of RMSF in two different regions of the American continent.
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Abstract
Coxiella burnetii, the causative agent of Query (Q) fever in humans, is a highly infectious obligate intracellular bacterium. Following uptake into a host cell, C. burnetii replicates within a phagolysosome-derived compartment referred to as the Coxiella-containing vacuole (CCV). During infection, C. burnetii exhibits tropism for tissues related to iron storage and recycling (e.g., the liver and splenic red pulp), suggesting that pathogen physiology is linked to host iron metabolism. Iron has been described to have a limited role in C. burnetii virulence regulation, despite evidence that C. burnetii -infected host cells increase expression of transferrin receptors, thereby suggesting that active iron acquisition by the bacterium occurs upon infection. Through the use of host cell-free culture, C. burnetii was separated from the host cell in order to directly assess the role of different forms of iron in C. burnetii replication and viability, and therefore virulence. Results indicate that C. burnetii tolerates molecular iron over a broad concentration range (i.e., ∼0.001 to 1 mM) and undergoes gross loss of viability upon iron starvation. C. burnetii protein synthesis and energy metabolism, however, occur nearly uninhibited under iron concentrations not permissive to replication. Despite the apparent absence of genes related to acquisition of host-associated iron-containing proteins, C. burnetii replication is supported by hemoglobin, transferrin, and ferritin, likely due to release of iron from such proteins under acidic conditions. Moreover, chelation of host iron pools inhibited pathogen replication during infection of cultured cells.IMPORTANCE Host organisms restrict the availability of iron to invading pathogens in order to reduce pathogen replication. To counteract the host's response to infection, bacteria can rely on redundant mechanisms to obtain biologically diverse forms of iron during infection. C. burnetii appears specifically dependent on molecular iron for replication and viability and exhibits a response to iron akin to bacteria that colonize iron-rich environments. Physiological adaptation of C. burnetii to the unique acidic and degradative environment of the CCV is consistent with access of this pathogen to molecular iron.
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Csicsay F, Flores-Ramirez G, Zuñiga-Navarrete F, Bartošová M, Fučíková A, Pajer P, Dresler J, Škultéty Ľ, Quevedo-Diaz M. Proteomic analysis of Rickettsia akari proposes a 44 kDa-OMP as a potential biomarker for Rickettsialpox diagnosis. BMC Microbiol 2020; 20:200. [PMID: 32640994 PMCID: PMC7341715 DOI: 10.1186/s12866-020-01877-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 06/25/2020] [Indexed: 12/12/2022] Open
Abstract
Background Rickettsialpox is a febrile illness caused by the mite-borne pathogen Rickettsia akari. Several cases of this disease are reported worldwide annually. Nevertheless, the relationship between the immunogenicity of R. akari and disease development is still poorly understood. Thus, misdiagnosis is frequent. Our study is aiming to identify immunogenic proteins that may improve disease recognition and enhance subsequent treatment. To achieve this goal, two proteomics methodologies were applied, followed by immunoblot confirmation. Results Three hundred and sixteen unique proteins were identified in the whole-cell extract of R. akari. The most represented protein groups were found to be those involved in translation, post-translational modifications, energy production, and cell wall development. A significant number of proteins belonged to amino acid transport and intracellular trafficking. Also, some proteins affecting the virulence were detected. In silico analysis of membrane enriched proteins revealed 25 putative outer membrane proteins containing beta-barrel structure and 11 proteins having a secretion signal peptide sequence. Using rabbit and human sera, various immunoreactive proteins were identified from which the 44 kDa uncharacterized protein (A8GP63) has demonstrated a unique detection capability. It positively distinguished the sera of patients with Rickettsialpox from other rickettsiae positive human sera. Conclusion Our proteomic analysis certainly contributed to the lack of knowledge of R. akari pathogenesis. The result obtained may also serve as a guideline for a more accurate diagnosis of rickettsial diseases. The identified 44 kDa uncharacterized protein can be certainly used as a unique marker of rickettsialpox or as a target molecule for the development of more effective treatment.
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Affiliation(s)
- František Csicsay
- Institute of Virology, Biomedical Research Center of the Slovak Academy of Sciences, Dúbravská cesta 9, 845 05, Bratislava, Slovak Republic
| | - Gabriela Flores-Ramirez
- Institute of Virology, Biomedical Research Center of the Slovak Academy of Sciences, Dúbravská cesta 9, 845 05, Bratislava, Slovak Republic
| | - Fernando Zuñiga-Navarrete
- Institute of Virology, Biomedical Research Center of the Slovak Academy of Sciences, Dúbravská cesta 9, 845 05, Bratislava, Slovak Republic
| | - Mária Bartošová
- Institute of Virology, Biomedical Research Center of the Slovak Academy of Sciences, Dúbravská cesta 9, 845 05, Bratislava, Slovak Republic
| | - Alena Fučíková
- Department of Biology, Faculty of Science, University of Hradec Kralove, Hradecká 1285, 500 03, Hradec Králové, Czech Republic
| | - Petr Pajer
- Military Health Institute, Military Medical Agency, Tychonova 1, CZ-160 00, Prague 6, Czech Republic
| | - Jiří Dresler
- Military Health Institute, Military Medical Agency, Tychonova 1, CZ-160 00, Prague 6, Czech Republic
| | - Ľudovít Škultéty
- Institute of Virology, Biomedical Research Center of the Slovak Academy of Sciences, Dúbravská cesta 9, 845 05, Bratislava, Slovak Republic. .,Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague 4, Czech Republic.
| | - Marco Quevedo-Diaz
- Institute of Virology, Biomedical Research Center of the Slovak Academy of Sciences, Dúbravská cesta 9, 845 05, Bratislava, Slovak Republic.
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The Rickettsial Ankyrin Repeat Protein 2 Is a Type IV Secreted Effector That Associates with the Endoplasmic Reticulum. mBio 2018; 9:mBio.00975-18. [PMID: 29946049 PMCID: PMC6020290 DOI: 10.1128/mbio.00975-18] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Strains of Rickettsia rickettsii, the tick-borne agent of Rocky Mountain spotted fever, vary considerably in virulence. Genomic comparisons of R. rickettsii strains have identified a relatively small number of genes divergent in an avirulent strain. Among these is one annotated as Rickettsia ankyrin repeat protein 2 (RARP-2). Homologs of RARP-2 are present in all strains of R. rickettsii, but the protein in the avirulent strain Iowa contains a large internal deletion relative to the virulent Sheila Smith strain. RARP-2 is secreted in a type IV secretion system-dependent manner and exposed to the host cell cytosol. RARP-2 of Sheila Smith colocalizes with multilamellar membranous structures bearing markers of the endoplasmic reticulum (ER), whereas the Iowa protein shows no colocalization with host cell organelles and evidence of proteolytic degradation is detected. Overexpression of Sheila Smith RARP-2 in R. rickettsii Iowa converts this avirulent strain’s typically nonlytic or opaque plaque type to a lytic plaque phenotype similar to that of the virulent Sheila Smith strain. Mutation of a predicted proteolytic active site of Sheila Smith RARP-2 abolished the lytic plaque phenotype but did not eliminate association with host membrane. RARP-2 is thus a type IV secreted effector and released from the rickettsiae into the host cytosol to modulate host processes during infection. Overexpression of Sheila Smith RARP-2 did not, however, restore the virulence of the Iowa strain in a guinea pig model, likely due to the multifactorial nature of rickettsial virulence. Members of the genus Rickettsia are obligate intracellular bacteria that exhibit a range of virulence from harmless endosymbionts of arthropods to the etiologic agents of severe disease. Despite the growing number of available genomes, little is known regarding virulence determinants of rickettsiae. Here, we have characterized an ankyrin repeat-containing protein, RARP-2, which differs between a highly virulent and an avirulent strain of R. rickettsii, the agent of Rocky Mountain spotted fever. RARP-2 is secreted by a type IV secretion system into the cytosol of the host cell, where it interacts with and manipulates the structure of the endoplasmic reticulum. RARP-2 from the avirulent strain is truncated by the loss of seven of 10 ankyrin repeat units but, although secreted, fails to alter ER structure. Recognition of those rickettsial factors associated with virulence will facilitate understanding of regional and strain-specific variation in severity of disease.
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Pokorzynski ND, Thompson CC, Carabeo RA. Ironing Out the Unconventional Mechanisms of Iron Acquisition and Gene Regulation in Chlamydia. Front Cell Infect Microbiol 2017; 7:394. [PMID: 28951853 PMCID: PMC5599777 DOI: 10.3389/fcimb.2017.00394] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 08/23/2017] [Indexed: 01/19/2023] Open
Abstract
The obligate intracellular pathogen Chlamydia trachomatis, along with its close species relatives, is known to be strictly dependent upon the availability of iron. Deprivation of iron in vitro induces an aberrant morphological phenotype termed "persistence." This persistent phenotype develops in response to various immunological and nutritional insults and may contribute to the development of sub-acute Chlamydia-associated chronic diseases in susceptible populations. Given the importance of iron to Chlamydia, relatively little is understood about its acquisition and its role in gene regulation in comparison to other iron-dependent bacteria. Analysis of the genome sequences of a variety of chlamydial species hinted at the involvement of unconventional mechanisms, being that Chlamydia lack many conventional systems of iron homeostasis that are highly conserved in other bacteria. Herein we detail past and current research regarding chlamydial iron biology in an attempt to provide context to the rapid progress of the field in recent years. We aim to highlight recent discoveries and innovations that illuminate the strategies involved in chlamydial iron homeostasis, including the vesicular mode of acquiring iron from the intracellular environment, and the identification of a putative iron-dependent transcriptional regulator that is synthesized as a fusion with a ABC-type transporter subunit. These recent findings, along with the noted absence of iron-related homologs, indicate that Chlamydia have evolved atypical approaches to the problem of iron homeostasis, reinvigorating research into the iron biology of this pathogen.
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Affiliation(s)
- Nick D Pokorzynski
- School of Molecular Biosciences, College of Veterinary Medicine, Washington State UniversityPullman, WA, United States
| | - Christopher C Thompson
- Jefferiss Trust Laboratories, Faculty of Medicine, Imperial College London, St. Mary's HospitalLondon, United Kingdom
| | - Rey A Carabeo
- School of Molecular Biosciences, College of Veterinary Medicine, Washington State UniversityPullman, WA, United States
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Evaluation of changes to the Rickettsia rickettsii transcriptome during mammalian infection. PLoS One 2017; 12:e0182290. [PMID: 28832688 PMCID: PMC5568294 DOI: 10.1371/journal.pone.0182290] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 07/14/2017] [Indexed: 12/12/2022] Open
Abstract
The lifecycle of Rickettsia rickettsii includes infection of both mammalian and arthropod hosts, with each environment presenting distinct challenges to survival. As such, these pathogens likely have distinctive transcriptional strategies for infection of each host. Herein, we report the utilization of next generation sequencing (RNAseq) and bioinformatic analysis techniques to examine the global transcriptional profile of R. rickettsii within an infected animal, and to compare that data to transcription in tissue culture. The results demonstrate substantial R. rickettsii transcriptional alteration in vivo, such that the bacteria are considerably altered from cell culture. Identification of significant transcriptional changes and validation of RNAseq by quantitative PCR are described with particular emphasis on known antigens and suspected virulence factors. Together, these results suggest that transcriptional regulation of a distinct cohort of genes may contribute to successful mammalian infection.
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El Karkouri K, Kowalczewska M, Armstrong N, Azza S, Fournier PE, Raoult D. Multi-omics Analysis Sheds Light on the Evolution and the Intracellular Lifestyle Strategies of Spotted Fever Group Rickettsia spp. Front Microbiol 2017; 8:1363. [PMID: 28775717 PMCID: PMC5517468 DOI: 10.3389/fmicb.2017.01363] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 07/05/2017] [Indexed: 11/13/2022] Open
Abstract
Arthropod-borne Rickettsia species are obligate intracellular bacteria which are pathogenic for humans. Within this genus, Rickettsia slovaca and Rickettsia conorii cause frequent and potentially severe infections, whereas Rickettsia raoultii and Rickettsia massiliae cause rare and milder infections. All four species belong to spotted fever group (SFG) rickettsiae. However, R. slovaca and R. raoultii cause scalp eschar and neck lymphadenopathy (SENLAT) and are mainly associated with Dermacentor ticks, whereas the other two species cause Mediterranean spotted fever (MSF) and are mainly transmitted by Rhipicephalus ticks. To identify the potential genes and protein profiles and to understand the evolutionary processes that could, comprehensively, relate to the differences in virulence and pathogenicity observed between these four species, we compared their genomes and proteomes. The virulent and milder agents displayed divergent phylogenomic evolution in two major clades, whereas either SENLAT or MSF disease suggests a discrete convergent evolution of one virulent and one milder agent, despite their distant genetic relatedness. Moreover, the two virulent species underwent strong reductive genomic evolution and protein structural variations, as well as a probable loss of plasmid(s), compared to the two milder species. However, an abundance of mobilome genes was observed only in the less pathogenic species. After infecting Xenopus laevis cells, the virulent agents displayed less up-regulated than down-regulated proteins, as well as less number of identified core proteins. Furthermore, their similar and distinct protein profiles did not contain some genes (e.g., ompA/B and rickA) known to be related to rickettsial adhesion, motility and/or virulence, but may include other putative virulence-, antivirulence-, and/or disease-related proteins. The identified evolutionary forces herein may have a strong impact on intracellular expressions and strategies in these rickettsiae, and that may contribute to the emergence of distinct virulence and diseases in humans. Thus, the current multi-omics data provide new insights into the evolution and fitness of SFG virulence and pathogenicity, and intracellular pathogenic bacteria.
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Affiliation(s)
- Khalid El Karkouri
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National De La Recherche Scientifique 7278, IRD 198, Institut National De La Santé Et De La Recherche Médicale U1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille UniversitéMarseille, France
| | - Malgorzata Kowalczewska
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National De La Recherche Scientifique 7278, IRD 198, Institut National De La Santé Et De La Recherche Médicale U1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille UniversitéMarseille, France
| | - Nicholas Armstrong
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National De La Recherche Scientifique 7278, IRD 198, Institut National De La Santé Et De La Recherche Médicale U1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille UniversitéMarseille, France
| | - Said Azza
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National De La Recherche Scientifique 7278, IRD 198, Institut National De La Santé Et De La Recherche Médicale U1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille UniversitéMarseille, France
| | - Pierre-Edouard Fournier
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National De La Recherche Scientifique 7278, IRD 198, Institut National De La Santé Et De La Recherche Médicale U1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille UniversitéMarseille, France
| | - Didier Raoult
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National De La Recherche Scientifique 7278, IRD 198, Institut National De La Santé Et De La Recherche Médicale U1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille UniversitéMarseille, France
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Schroeder CLC, Narra HP, Sahni A, Khanipov K, Patel J, Fofanov Y, Sahni SK. Transcriptional profiling of Rickettsia prowazekii coding and non-coding transcripts during in vitro host-pathogen and vector-pathogen interactions. Ticks Tick Borne Dis 2017; 8:827-836. [PMID: 28709615 DOI: 10.1016/j.ttbdis.2017.06.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 06/13/2017] [Accepted: 06/15/2017] [Indexed: 01/09/2023]
Abstract
Natural pathogen transmission of Rickettsia prowazekii, the etiologic agent of epidemic typhus, to humans is associated with arthropods, including human body lice, ticks, and ectoparasites of eastern flying squirrel. Recently, we have documented the presence of small RNAs in Rickettsia species and expression of R. prowazekii sRNAs during infection of cultured human microvascular endothelial cells (HMECs), which represent the primary target cells during human infections. Bacterial noncoding transcripts are now well established as critical post-transcriptional regulators of virulence and adaptation mechanisms in varying host environments. Despite their importance, little is known about the expression profile and regulatory activities of R. prowazekii sRNAs (Rp_sRs) in different host cells encountered as part of the natural life-cycle. To investigate the sRNA expression profile of R. prowazekii during infection of arthropod host cells, we employed an approach combining in vitro infection, bioinformatics, RNA sequencing, and PCR-based quantitation. Global analysis of R. prowazekii transcriptome by strand-specific RNA sequencing enabled us to identify 67 cis-acting (antisense) and 26 trans-acting (intergenic) Rp_sRs expressed during the infection of Amblyomma americanum (AAE2) cells. Comparative evaluation of expression during R. prowazekii infection of HMECs and AAE2 cells by quantitative RT-PCR demonstrated significantly higher expression of four selected Rp_sRs in tick AAE2 cells. Examination of the coding transcriptome revealed differential up-regulation of >150 rickettsial genes in either HMECs or AAE2 cells and yielded evidence for host cell-dependent utilization of alternative transcription start sites by 18 rickettsial genes. Our results thus suggest noticeable differences in the expression of both Rp_sRs as well as the coding transcriptome and the exploitation of multiple transcription initiation sites for select genes during the infection of human endothelium and tick vector cells as the host and yield new insights into rickettsial virulence and transmission mechanisms.
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Affiliation(s)
- Casey L C Schroeder
- Department of Pathology, University of Texas Medical Branch, 301 University Boulevard Galveston, TX 77555, USA.
| | - Hema P Narra
- Department of Pathology, University of Texas Medical Branch, 301 University Boulevard Galveston, TX 77555, USA.
| | - Abha Sahni
- Department of Pathology, University of Texas Medical Branch, 301 University Boulevard Galveston, TX 77555, USA.
| | - Kamil Khanipov
- Department of Pharmacology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA.
| | - Jignesh Patel
- Department of Pathology, University of Texas Medical Branch, 301 University Boulevard Galveston, TX 77555, USA.
| | - Yuriy Fofanov
- Department of Pharmacology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA.
| | - Sanjeev K Sahni
- Department of Pathology, University of Texas Medical Branch, 301 University Boulevard Galveston, TX 77555, USA.
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Spatial Analysis of Severe Fever with Thrombocytopenia Syndrome Virus in China Using a Geographically Weighted Logistic Regression Model. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2016; 13:ijerph13111125. [PMID: 27845737 PMCID: PMC5129335 DOI: 10.3390/ijerph13111125] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 10/28/2016] [Accepted: 11/02/2016] [Indexed: 12/23/2022]
Abstract
Severe fever with thrombocytopenia syndrome (SFTS) is caused by severe fever with thrombocytopenia syndrome virus (SFTSV), which has had a serious impact on public health in parts of Asia. There is no specific antiviral drug or vaccine for SFTSV and, therefore, it is important to determine the factors that influence the occurrence of SFTSV infections. This study aimed to explore the spatial associations between SFTSV infections and several potential determinants, and to predict the high-risk areas in mainland China. The analysis was carried out at the level of provinces in mainland China. The potential explanatory variables that were investigated consisted of meteorological factors (average temperature, average monthly precipitation and average relative humidity), the average proportion of rural population and the average proportion of primary industries over three years (2010-2012). We constructed a geographically weighted logistic regression (GWLR) model in order to explore the associations between the selected variables and confirmed cases of SFTSV. The study showed that: (1) meteorological factors have a strong influence on the SFTSV cover; (2) a GWLR model is suitable for exploring SFTSV cover in mainland China; (3) our findings can be used for predicting high-risk areas and highlighting when meteorological factors pose a risk in order to aid in the implementation of public health strategies.
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Galletti MFBM, Fujita A, Rosa RD, Martins LA, Soares HS, Labruna MB, Daffre S, Fogaça AC. Virulence genes of Rickettsia rickettsii are differentially modulated by either temperature upshift or blood-feeding in tick midgut and salivary glands. Parasit Vectors 2016; 9:331. [PMID: 27287539 PMCID: PMC4902979 DOI: 10.1186/s13071-016-1581-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 05/10/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rickettsia rickettsii, the etiological agent of Rocky Mountain spotted fever, is transmitted to humans by ticks. During tick feeding, R. rickettsii is exposed to both temperature elevation and components of the blood meal, which have previously been associated with the reactivation of its virulence. These environmental stimuli were also reported to modulate virulence genes of R. rickettsii infecting a set of organs of adult females of its natural vector, Amblyomma aureolatum. METHODS In this study, we determined the effects of a temperature upshift, blood-feeding, and both stimuli simultaneously on the expression of 85 selected genes of R. rickettsii infecting either the midgut (MG) or salivary glands (SG) of male and female A. aureolatum by microfluidic high-throughput RT-qPCR. These two organs are key for acquisition of this bacterium by the tick and transmission to the vertebrate host, respectively. RESULTS Data showed that these environmental stimuli exert distinct effects on rickettsial transcription depending on the colonized organ and gender of the vector. Temperature upshift induced the majority of differentially expressed genes of R. rickettsii in tick SG, including tRNA synthetases encoding genes. On the contrary, blood-feeding downregulated most of differentially expressed genes in both organs, but induced type IV secretion system components and OmpB in tick MG. The combined effects of both stimuli resulted in a merged gene expression profile representing features of each stimulus analyzed independently, but was more similar to the profile induced by blood-feeding. CONCLUSION The upregulation of the majority of differentially expressed genes in tick SG by temperature upshift suggests that this stimulus is important to prepare R. rickettsii for transmission to the vertebrate host. Blood-feeding, on the other hand, induced important virulence genes in the tick MG, which might be associated with colonization of the tick and transmission to the vertebrate host. The role of the proteins identified in this study must be addressed and might help to define future targets to block tick infection, thereby preventing RMSF. To our knowledge, this is the first transcriptional tissue-specific study of a virulent strain of R. rickettsii infecting a natural tick vector.
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Affiliation(s)
- Maria Fernanda B M Galletti
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - André Fujita
- Departamento de Ciências da Computação, Instituto de Matemática e Estatística, Universidade de São Paulo, São Paulo, Brazil
| | - Rafael D Rosa
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil.,Departamento de Biologia Celular, Embriologia e Genética, Universidade Federal de Santa Catarina, Santa Catarina, Brazil
| | - Larissa A Martins
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Herbert S Soares
- Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | - Marcelo B Labruna
- Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | - Sirlei Daffre
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Andréa C Fogaça
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil.
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Transcriptome Analysis Reveals a Signature Profile for Tick-Borne Flavivirus Persistence in HEK 293T Cells. mBio 2016; 7:mBio.00314-16. [PMID: 27222466 PMCID: PMC4895102 DOI: 10.1128/mbio.00314-16] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
UNLABELLED Tick-borne flaviviruses (TBFVs) cause febrile illnesses, which may progress to severe encephalitis and/or death in humans globally. Most people who recover from severe acute disease suffer from debilitating neurological sequelae, which may be due to viral persistence, infection-induced neurological cell damage, host response, or some combination of these. Acute TBFV infection of human embryonic kidney (HEK) 293T cells in vitro results in the death of >95% of infected cells by day 5. However, replacing cell growth medium allows surviving cells to repopulate and become persistently infected for extended periods of time. The mechanisms responsible for initiation and maintenance of viral persistence remain vague. We subjected the HEK 293T cell transcriptome to deep sequencing to identify genes differentially expressed during acute infection and persistent infection. A total of 451 genes showed unique significant differential expression levels in persistently infected cells relative to the acute phase of infection. Ingenuity Pathway Analysis results suggested that the expression of prosurvival oncogenes AKT2 and ERBB2 was upregulated in persistently infected cells, whereas proapoptotic genes, such as Bad and the beta interferon 1 (IFN-β1) gene, were downregulated. Genes encoding antiviral cytokines such as the CCL5, tumor necrosis factor alpha (TNF-α), and CXCL10 genes were upregulated during the acute phase, but the same genes were relatively quiescent in persistently infected cells. Exogenous induction of apoptosis demonstrated that persistently infected cells were resistant to apoptosis in a dose-dependent manner. In summary, the differential transcriptome profiles of acute-phase compared to persistently infected HEK 293T cells demonstrated an evasion of apoptosis, which may be critical for a chronic TBFV infection state. These results provide a basis for further study of the mechanisms of TBFV persistence. IMPORTANCE Tick-borne flaviviruses (TBFVs) cause life-threatening encephalitic disease in humans worldwide. Some people who recover from severe disease may suffer prolonged neurological symptoms due to either virus- or host response-induced cell damage or a combination of the two that are linked to viral persistence. By examining the genes that are significantly differentially expressed in acute TBFV infection versus persistent TBFV infection, we may be able to find the molecular basis of viral persistence. Here we used deep sequencing of the host cell transcriptome to discover that the expression levels of prosurvival genes were upregulated in persistently infected cells relative to acute TBFV infections whereas the expression levels of genes that promote programmed cell death were downregulated. In addition, persistently infected cells were also resistant to exogenous chemical induction of cell death, in a dose-dependent manner, compared to uninfected cells. Our results pave the way for further studies aimed at understanding the precise mechanisms of TBFV persistence.
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Gong W, Xiong X, Qi Y, Jiao J, Duan C, Wen B. Identification of novel surface-exposed proteins of Rickettsia rickettsii by affinity purification and proteomics. PLoS One 2014; 9:e100253. [PMID: 24950252 PMCID: PMC4065002 DOI: 10.1371/journal.pone.0100253] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 05/23/2014] [Indexed: 11/18/2022] Open
Abstract
Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, is the most pathogenic member among Rickettsia spp. Surface-exposed proteins (SEPs) of R. rickettsii may play important roles in its pathogenesis or immunity. In this study, R. rickettsii organisms were surface-labeled with sulfo-NHS-SS-biotin and the labeled proteins were affinity-purified with streptavidin. The isolated proteins were separated by two-dimensional electrophoresis, and 10 proteins were identified among 23 protein spots by electrospray ionization tandem mass spectrometry. Five (OmpA, OmpB, GroEL, GroES, and a DNA-binding protein) of the 10 proteins were previously characterized as surface proteins of R. rickettsii. Another 5 proteins (Adr1, Adr2, OmpW, Porin_4, and TolC) were first recognized as SEPs of R. rickettsii herein. The genes encoding the 5 novel SEPs were expressed in Escherichia coli cells, resulting in 5 recombinant SEPs (rSEPs), which were used to immunize mice. After challenge with viable R. rickettsii cells, the rickettsial load in the spleen, liver, or lung of mice immunized with rAdr2 and in the lungs of mice immunized with other rSEPs excluding rTolC was significantly lower than in mice that were mock-immunized with PBS. The in vitro neutralization test revealed that sera from mice immunized with rAdr1, rAdr2, or rOmpW reduced R. rickettsii adherence to and invasion of vascular endothelial cells. The immuno-electron microscopic assay clearly showed that the novel SEPs were located in the outer and/or inner membrane of R. rickettsii. Altogether, the 5 novel SEPs identified herein might be involved in the interaction of R. rickettsii with vascular endothelial cells, and all of them except TolC were protective antigens.
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Affiliation(s)
- Wenping Gong
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Xiaolu Xiong
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
- * E-mail: (BW); (XX)
| | - Yong Qi
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Jun Jiao
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Changsong Duan
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Bohai Wen
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
- * E-mail: (BW); (XX)
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Liu K, Cui N, Fang LQ, Wang BJ, Lu QB, Peng W, Li H, Wang LY, Liang S, Wang HY, Zhang YY, Zhuang L, Yang H, Gray GC, de Vlas SJ, Liu W, Cao WC. Epidemiologic features and environmental risk factors of severe fever with thrombocytopenia syndrome, Xinyang, China. PLoS Negl Trop Dis 2014; 8:e2820. [PMID: 24810269 PMCID: PMC4014392 DOI: 10.1371/journal.pntd.0002820] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 03/11/2014] [Indexed: 11/18/2022] Open
Abstract
Background Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease discovered in rural areas of Central China in 2009, caused by a novel bunyavirus, SFTS virus (SFTSV). The disease usually presents as fever, thrombocytopenia, and leukocytopenia, with case-fatality rates ranging from 2.5% to 30%. Haemaphysalis longicornis was suspected to be the most likely vector of SFTSV. By the end of 2012, the disease had expanded to 13 provinces of China. SFTS patients have been reported in Japan and South Korea, and a disease similar to SFTS has been reported in the United States. Methodology/Principal Findings We characterized the epidemiologic features of 504 confirmed SFTS cases in Xinyang Region, the most severely SFTS-afflicted region in China from 2011 to 2012, and assessed the environmental risk factors. All cases occurred during March to November, with the epidemic peaking from May to July. The patients' ages ranged from 7 to 87 years (median 61 years), and the annual incidence increased with age (χ2 test for trend, P<0.001). The female-to-male ratio of cases was 1.58, and 97.0% of the cases were farmers who resided in the southern and western parts of the region. The Poisson regression analysis revealed that the spatial variations of SFTS incidence were significantly associated with the shrub, forest, and rain-fed cropland areas. Conclusions The distribution of SFTS showed highly significant temporal and spatial heterogeneity in Xinyang Region, with the majority of SFTS cases being elderly farmers who resided in the southern and western parts of the region, mostly acquiring infection between May and July when H. longicornis is highly active. The shrub, rain-fed, and rain-fed cropland areas were associated with high risk for this disease. Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease discovered in rural areas of Central China in 2009, caused by a novel bunyavirus, SFTS virus (SFTSV). The disease usually presents as fever, thrombocytopenia, and leukocytopenia, with case-fatality rates ranging from 2.5% to 30%. By the end of 2012, the disease had expanded to 13 provinces of China. SFTS patients have been reported in Japan and South Korea, and a disease similar to SFTS has been reported in the United States. Here we characterized the epidemiologic features of 504 confirmed SFTS cases in Xinyang, the most severely SFTS-affected region in China from 2011 to 2012, and identified the environmental risk factors. We found the distribution of SFTS cases showed highly significant temporal and spatial heterogeneity, with the majority of SFTS cases being elderly farmers who resided in the southern and western parts of the region, mostly acquiring infection between May and July when H. longicornis is highly active. The shrub, forest, and rain-fed cropland areas were strongly associated with high risk for SFTS.
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Affiliation(s)
- Kun Liu
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
| | - Ning Cui
- The 154 Hospital, People's Liberation Army, Xinyang, People's Republic of China
| | - Li-Qun Fang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
| | - Bing-Jun Wang
- The 154 Hospital, People's Liberation Army, Xinyang, People's Republic of China
| | - Qing-Bin Lu
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
| | - Wei Peng
- The Shangcheng People's Hospital, Shangcheng, People's Republic of China
| | - Hao Li
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
| | - Li-Yuan Wang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
- Anhui Medical University, Hefei, People's Republic of China
| | - Song Liang
- Environmental and Global Health, College of Public Health and Health Professions, and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Hong-Yu Wang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
- Anhui Medical University, Hefei, People's Republic of China
| | - Yao-Yun Zhang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
- Anhui Medical University, Hefei, People's Republic of China
| | - Lu Zhuang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
| | - Hong Yang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
| | - Gregory C. Gray
- Environmental and Global Health, College of Public Health and Health Professions, and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Sake J. de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Wei Liu
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
- * E-mail: (WL); (WCC)
| | - Wu-Chun Cao
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
- * E-mail: (WL); (WCC)
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Sahni SK, Narra HP, Sahni A, Walker DH. Recent molecular insights into rickettsial pathogenesis and immunity. Future Microbiol 2014; 8:1265-88. [PMID: 24059918 DOI: 10.2217/fmb.13.102] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Human infections with arthropod-borne Rickettsia species remain a major global health issue, causing significant morbidity and mortality. Epidemic typhus due to Rickettsia prowazekii has an established reputation as the 'scourge of armies', and as a major determinant of significant 'historical turning points'. No suitable vaccines for human use are currently available to prevent rickettsial diseases. The unique lifestyle features of rickettsiae include obligate intracellular parasitism, intracytoplasmic niche within the host cell, predilection for infection of microvascular endothelium in mammalian hosts, association with arthropods and the tendency for genomic reduction. The fundamental research in the field of Rickettsiology has witnessed significant recent progress in the areas of pathogen adhesion/invasion and host immune responses, as well as the genomics, proteomics, metabolomics, phylogenetics, motility and molecular manipulation of important rickettsial pathogens. The focus of this review article is to capture a snapshot of the latest developments pertaining to the mechanisms of rickettsial pathogenesis and immunity.
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Affiliation(s)
- Sanjeev K Sahni
- Department of Pathology & Institute for Human Infections & Immunity, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
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Dunphy PS, Luo T, McBride JW. Ehrlichia moonlighting effectors and interkingdom interactions with the mononuclear phagocyte. Microbes Infect 2013; 15:1005-16. [PMID: 24141087 PMCID: PMC3886233 DOI: 10.1016/j.micinf.2013.09.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 09/27/2013] [Accepted: 09/30/2013] [Indexed: 01/19/2023]
Abstract
Ehrlichia chaffeensis is an obligately intracellular gram negative bacterium with a small genome that thrives in mammalian mononuclear phagocytes by exploiting eukaryotic processes. Herein, we discuss the latest findings on moonlighting tandem repeat protein effectors and their secretion mechanisms, and novel molecular interkingdom interactions that provide insight into the intracellular pathobiology of ehrlichiae.
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Affiliation(s)
- Paige Selvy Dunphy
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555
| | - Tian Luo
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555
| | - Jere W. McBride
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas 77555
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas 77555
- Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas 77555
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas 77555
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Galletti MFBM, Fujita A, Nishiyama Jr MY, Malossi CD, Pinter A, Soares JF, Daffre S, Labruna MB, Fogaça AC. Natural blood feeding and temperature shift modulate the global transcriptional profile of Rickettsia rickettsii infecting its tick vector. PLoS One 2013; 8:e77388. [PMID: 24155949 PMCID: PMC3796454 DOI: 10.1371/journal.pone.0077388] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 09/04/2013] [Indexed: 11/20/2022] Open
Abstract
Rickettsia rickettsii is an obligate intracellular tick-borne bacterium that causes Rocky Mountain Spotted Fever (RMSF), the most lethal spotted fever rickettsiosis. When an infected starving tick begins blood feeding from a vertebrate host, R. rickettsii is exposed to a temperature elevation and to components in the blood meal. These two environmental stimuli have been previously associated with the reactivation of rickettsial virulence in ticks, but the factors responsible for this phenotype conversion have not been completely elucidated. Using customized oligonucleotide microarrays and high-throughput microfluidic qRT-PCR, we analyzed the effects of a 10°C temperature elevation and of a blood meal on the transcriptional profile of R. rickettsii infecting the tick Amblyomma aureolatum. This is the first study of the transcriptome of a bacterium in the genus Rickettsia infecting a natural tick vector. Although both stimuli significantly increased bacterial load, blood feeding had a greater effect, modulating five-fold more genes than the temperature upshift. Certain components of the Type IV Secretion System (T4SS) were up-regulated by blood feeding. This suggests that this important bacterial transport system may be utilized to secrete effectors during the tick vector’s blood meal. Blood feeding also up-regulated the expression of antioxidant enzymes, which might correspond to an attempt by R. rickettsii to protect itself against the deleterious effects of free radicals produced by fed ticks. The modulated genes identified in this study, including those encoding hypothetical proteins, require further functional analysis and may have potential as future targets for vaccine development.
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Affiliation(s)
| | - André Fujita
- Departamento de Ciências da Computação, Instituto de Matemática e Estatística, Universidade de São Paulo, São Paulo, Brazil
| | - Milton Y. Nishiyama Jr
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Camila D. Malossi
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Adriano Pinter
- Superintendência de Controle de Endemias (SUCEN), São Paulo, Brazil
| | - João F. Soares
- Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | - Sirlei Daffre
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Marcelo B. Labruna
- Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | - Andréa C. Fogaça
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
- * E-mail:
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Abromaitis S, Nelson CS, Previte D, Yoon KS, Clark JM, DeRisi JL, Koehler JE. Bartonella quintana deploys host and vector temperature-specific transcriptomes. PLoS One 2013; 8:e58773. [PMID: 23554923 PMCID: PMC3595295 DOI: 10.1371/journal.pone.0058773] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2012] [Accepted: 02/06/2013] [Indexed: 11/20/2022] Open
Abstract
The bacterial pathogen Bartonella quintana is passed between humans by body lice. B. quintana has adapted to both the human host and body louse vector niches, producing persistent infection with high titer bacterial loads in both the host (up to 105 colony-forming units [CFU]/ml) and vector (more than 108 CFU/ml). Using a novel custom microarray platform, we analyzed bacterial transcription at temperatures corresponding to the host (37°C) and vector (28°C), to probe for temperature-specific and growth phase-specific transcriptomes. We observed that transcription of 7% (93 genes) of the B. quintana genome is modified in response to change in growth phase, and that 5% (68 genes) of the genome is temperature-responsive. Among these transcriptional changes in response to temperature shift and growth phase was the induction of known B. quintana virulence genes and several previously unannotated genes. Hemin binding proteins, secretion systems, response regulators, and genes for invasion and cell attachment were prominent among the differentially-regulated B. quintana genes. This study represents the first analysis of global transcriptional responses by B. quintana. In addition, the in vivo experiments provide novel insight into the B. quintana transcriptional program within the body louse environment. These data and approaches will facilitate study of the adaptation mechanisms employed by Bartonella during the transition between human host and arthropod vector.
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Affiliation(s)
- Stephanie Abromaitis
- Microbial Pathogenesis and Host Defense Program, University of California San Francisco, San Francisco, California, United States of America
- Division of Infectious Diseases, Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
| | - Christopher S. Nelson
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
- Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, California, United States of America
| | - Domenic Previte
- Department of Veterinary and Animal Science, University of Massachusetts at Amherst, Amherst, Massachusetts, United States of America
| | - Kyong S. Yoon
- Department of Veterinary and Animal Science, University of Massachusetts at Amherst, Amherst, Massachusetts, United States of America
| | - J. Marshall Clark
- Department of Veterinary and Animal Science, University of Massachusetts at Amherst, Amherst, Massachusetts, United States of America
| | - Joseph L. DeRisi
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
- Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California, United States of America
| | - Jane E. Koehler
- Microbial Pathogenesis and Host Defense Program, University of California San Francisco, San Francisco, California, United States of America
- Division of Infectious Diseases, Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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Pierlé SA, Dark MJ, Dahmen D, Palmer GH, Brayton KA. Comparative genomics and transcriptomics of trait-gene association. BMC Genomics 2012. [PMID: 23181781 PMCID: PMC3542260 DOI: 10.1186/1471-2164-13-669] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Background The Order Rickettsiales includes important tick-borne pathogens, from Rickettsia rickettsii, which causes Rocky Mountain spotted fever, to Anaplasma marginale, the most prevalent vector-borne pathogen of cattle. Although most pathogens in this Order are transmitted by arthropod vectors, little is known about the microbial determinants of transmission. A. marginale provides unique tools for studying the determinants of transmission, with multiple strain sequences available that display distinct and reproducible transmission phenotypes. The closed core A. marginale genome suggests that any phenotypic differences are due to single nucleotide polymorphisms (SNPs). We combined DNA/RNA comparative genomic approaches using strains with different tick transmission phenotypes and identified genes that segregate with transmissibility. Results Comparison of seven strains with different transmission phenotypes generated a list of SNPs affecting 18 genes and nine promoters. Transcriptional analysis found two candidate genes downstream from promoter SNPs that were differentially transcribed. To corroborate the comparative genomics approach we used three RNA-seq platforms to analyze the transcriptomes from two A. marginale strains with different transmission phenotypes. RNA-seq analysis confirmed the comparative genomics data and found 10 additional genes whose transcription between strains with distinct transmission efficiencies was significantly different. Six regions of the genome that contained no annotation were found to be transcriptionally active, and two of these newly identified transcripts were differentially transcribed. Conclusions This approach identified 30 genes and two novel transcripts potentially involved in tick transmission. We describe the transcriptome of an obligate intracellular bacterium in depth, while employing massive parallel sequencing to dissect an important trait in bacterial pathogenesis.
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Affiliation(s)
- Sebastián Aguilar Pierlé
- Program in Genomics, Department of Veterinary Microbiology and Pathology, Paul G, Allen School for Global Animal Health, Washington State University, Pullman, WA 99164-7040, USA.
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Gerarden KP, Fuchs AM, Koch JM, Mueller MM, Graupner DR, O'Rorke JT, Frost CD, Heinen HA, Lackner ER, Schoeller SJ, House PG, Peterson FC, Veldkamp CT. Solution structure of the cold-shock-like protein from Rickettsia rickettsii. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 68:1284-8. [PMID: 23143233 PMCID: PMC3515365 DOI: 10.1107/s174430911203881x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 09/10/2012] [Indexed: 11/25/2022]
Abstract
The solution structure of the cold-shock-like protein from R. rickettsii, the causative agent of Rocky Mountain spotted fever, is reported. Rocky Mountain spotted fever is caused by Rickettsia rickettsii infection. R. rickettsii can be transmitted to mammals, including humans, through the bite of an infected hard-bodied tick of the family Ixodidae. Since the R. rickettsii genome contains only one cold-shock-like protein and given the essential nature of cold-shock proteins in other bacteria, the structure of the cold-shock-like protein from R. rickettsii was investigated. With the exception of a short α-helix found between β-strands 3 and 4, the solution structure of the R. rickettsii cold-shock-like protein has the typical Greek-key five-stranded β-barrel structure found in most cold-shock domains. Additionally, the R. rickettsii cold-shock-like protein, with a ΔG of unfolding of 18.4 kJ mol−1, has a similar stability when compared with other bacterial cold-shock proteins.
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Affiliation(s)
- Kyle P Gerarden
- Department of Chemistry, University of Wisconsin-Whitewater, 800 West Main Street, Whitewater, WI 53190, USA
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Why are there so few Rickettsia conorii conorii-infected Rhipicephalus sanguineus ticks in the wild? PLoS Negl Trop Dis 2012; 6:e1697. [PMID: 22724035 PMCID: PMC3378603 DOI: 10.1371/journal.pntd.0001697] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 05/02/2012] [Indexed: 11/28/2022] Open
Abstract
Background Rickettsia conorii conorii is the etiological agent of Mediterranean spotted fever, which is transmitted by the brown dog tick, Rhipicephalus sanguineus. The relationship between the Rickettsia and its tick vector are still poorly understood one century after the first description of this disease. Methodology/Principal Findings An entomological survey was organized in Algeria to collect ticks from the houses of patients with spotted fever signs. Colonies of R. conorii conorii-infected and non-infected ticks were established under laboratory conditions. Gimenez staining and electron microscopy on the ovaries of infected ticks indicated heavy rickettsial infection. The transovarial transmission of R. conorii conorii in naturally infected Rh. sanguineus ticks was 100% at eleven generations, and the filial infection rate was up to 99% according to molecular analyses. No differences in life cycle duration were observed between infected and non-infected ticks held at 25°C, but the average weight of engorged females and eggs was significantly lower in infected ticks than in non-infected ticks. The eggs, larvae and unfed nymphs of infected and non-infected ticks could not tolerate low (4°C) or high (37°C) temperatures or long starvation periods. R. conorii conorii-infected engorged nymphs that were exposed to a low or high temperature for one month experienced higher mortality when they were transferred to 25°C than non-infected ticks after similar exposure. High mortality was observed in infected adults that were maintained for one month at a low or high temperature after tick-feeding on rabbits. Conclusion/Significance These preliminary results suggest that infected quiescent ticks may not survive the winter and may help explain the low prevalence of infected Rh. sanguineus in nature. Further investigations on the influence of extrinsic factors on diapaused R. conorii-infected and non-infected ticks are required. The bacterium Rickettsia conorii conorii is the etiological agent of Mediterranean spotted fever (MSF), which is a life-threatening infectious disease that is transmitted by Rhipicephalus sanguineus, the brown dog tick. Rh. sanguineus-R. conorii conorii relationships in the wild are still poorly understood one century after the discovery of the disease. In this study, we collected naturally infected ticks from the houses of people afflicted by MSF in Algeria. Colonies of both infected and non-infected ticks were maintained in our laboratory, and we studied the effect of temperature variations on the infected and non-infected ticks. We did not observe any major differences between the biological life cycle of the infected and non-infected ticks held at 25°C. However, a comparatively higher mortality relative to the control group was noticed when R. conorii conorii-infected engorged nymphs and adults were exposed to a low temperature (4°C) or high temperature (37°C) for one month and transferred to 25°C. R. conorii conorii-infected Rh. sanguineus may maintain and serve as reservoirs for the Rickettsia if they are not exposed to cold temperatures. New populations of ticks might become infected with Rickettsiae when feeding on a bacteremic animal reservoir.
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Kuriakose JA, Miyashiro S, Luo T, Zhu B, McBride JW. Ehrlichia chaffeensis transcriptome in mammalian and arthropod hosts reveals differential gene expression and post transcriptional regulation. PLoS One 2011; 6:e24136. [PMID: 21915290 PMCID: PMC3167834 DOI: 10.1371/journal.pone.0024136] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 08/05/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Human monocytotropic ehrlichiosis is an emerging life-threatening zoonosis caused by obligately intracellular bacterium, Ehrlichia chaffeensis. E. chaffeensis is transmitted by the lone star tick, Amblyomma americanum, and replicates in mononuclear phagocytes in mammalian hosts. Differences in the E. chaffeensis transcriptome in mammalian and arthropod hosts are unknown. Thus, we determined host-specific E. chaffeensis gene expression in human monocyte (THP-1) and in Amblyomma and Ixodes tick cell lines (AAE2 and ISE6) using a whole genome microarray. METHODOLOGY/PRINCIPAL FINDINGS The majority (∼80%) of E. chaffeensis genes were expressed during infection in human and tick cells. There were few differences observed in E. chaffeensis gene expression between the vector Amblyomma and non-vector Ixodes tick cells, but extensive host-specific and differential gene expression profiles were detected between human and tick cells, including higher transcriptional activity in tick cells and identification of gene subsets that were differentially expressed in the two hosts. Differentially and host-specifically expressed ehrlichial genes encoded major immunoreactive tandem repeat proteins (TRP), the outer membrane protein (OMP-1) family, and hypothetical proteins that were 30-80 amino acids in length. Consistent with previous observations, high expression of p28 and OMP-1B genes was detected in human and tick cells, respectively. Notably, E. chaffeensis genes encoding TRP32 and TRP47 were highly upregulated in the human monocytes and expressed as proteins; however, although TRP transcripts were expressed in tick cells, the proteins were not detected in whole cell lysates demonstrating that TRP expression was post transcriptionally regulated. CONCLUSIONS/SIGNIFICANCE Ehrlichia gene expression is highly active in tick cells, and differential gene expression among a wide variety of host-pathogen associated genes occurs. Furthermore, we demonstrate that genes associated with host-pathogen interactions are differentially expressed and regulated by post transcriptional mechanisms.
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Affiliation(s)
- Jeeba A. Kuriakose
- Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Simone Miyashiro
- Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Tian Luo
- Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Bing Zhu
- Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Jere W. McBride
- Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
- Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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Complementation of Rickettsia rickettsii RelA/SpoT restores a nonlytic plaque phenotype. Infect Immun 2011; 79:1631-7. [PMID: 21300770 DOI: 10.1128/iai.00048-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Spotted fever group rickettsiae are known to produce distinct plaque phenotypes. Strains that cause lytic infections in cell culture form clear plaques, while nonlytic strains form opaque plaques in which the cells remain intact. Clear plaques have historically been associated with more-virulent species or strains of spotted fever group rickettsiae. We have selected spontaneous mutant pairs from two independent strains of Rickettsia rickettsii, the virulent R strain and the avirulent Iowa strain. A nonlytic variant of R. rickettsii R, which typically produces clear plaques, was isolated and stably maintained. A lytic variant of the Iowa strain, which characteristically produces opaque plaques, was also selected and maintained. Genomic resequencing of the variants identified only a single gene disrupted in each strain. In both cases, the mutation was in a gene annotated as relA/spoT-like. In the Iowa strain, a single mutation introduced a premature stop codon upstream from region encoding the predicted active site of RelA/SpoT and caused the transition to a lytic plaque phenotype. In R. rickettsii R, the nonlytic plaque phenotype resulted from a single-nucleotide substitution that shifted a tyrosine residue to histidine near the active site of the enzyme. The intact relA/spoT gene thus occurred in variants with the nonlytic plaque phenotype. Complementation of the truncated relA/spoT gene in the Iowa lytic plaque variant restored the nonlytic phenotype. The relA/spoT mutations did not affect the virulence of either strain in a Guinea pig model of infection; R strain lytic and nonlytic variants both induced fever equally, and the mutation in Iowa to a lytic phenotype did not cause them to become virulent.
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Leroy Q, Lebrigand K, Armougom F, Barbry P, Thiéry R, Raoult D. Coxiella burnetii transcriptional analysis reveals serendipity clusters of regulation in intracellular bacteria. PLoS One 2010; 5:e15321. [PMID: 21203564 PMCID: PMC3006202 DOI: 10.1371/journal.pone.0015321] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Accepted: 11/05/2010] [Indexed: 11/19/2022] Open
Abstract
Coxiella burnetii, the causative agent of the zoonotic disease Q
fever, is mainly transmitted to humans through an aerosol route. A spore-like
form allows C. burnetii to resist different environmental
conditions. Because of this, analysis of the survival strategies used by this
bacterium to adapt to new environmental conditions is critical for our
understanding of C. burnetii pathogenicity. Here, we report the
early transcriptional response of C. burnetii under temperature
stresses. Our data show that C. burnetii exhibited minor
changes in gene regulation under short exposure to heat or cold shock. While
small differences were observed, C. burnetii seemed to respond
similarly to cold and heat shock. The expression profiles obtained using
microarrays produced in-house were confirmed by quantitative RT-PCR. Under
temperature stresses, 190 genes were differentially expressed in at least one
condition, with a fold change of up to 4. Globally, the differentially expressed
genes in C. burnetii were associated with bacterial division,
(p)ppGpp synthesis, wall and membrane biogenesis and, especially,
lipopolysaccharide and peptidoglycan synthesis. These findings could be
associated with growth arrest and witnessed transformation of the bacteria to a
spore-like form. Unexpectedly, clusters of neighboring genes were differentially
expressed. These clusters do not belong to operons or genetic networks; they
have no evident associated functions and are not under the control of the same
promoters. We also found undescribed but comparable clusters of regulation in
previously reported transcriptomic analyses of intracellular bacteria, including
Rickettsia sp. and Listeria monocytogenes.
The transcriptomic patterns of C. burnetii observed under
temperature stresses permits the recognition of unpredicted clusters of
regulation for which the trigger mechanism remains unidentified but which may be
the result of a new mechanism of epigenetic regulation.
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Affiliation(s)
- Quentin Leroy
- Unité de Recherche en Maladies Infectieuses et Tropicales
Emergentes, CNRS-IRD, UMR 6236, Faculté de Médecine,
Université de la Méditerranée, Marseille,
France
| | - Kevin Lebrigand
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR
6079 CNRS/UNSA, Sophia Antipolis, France
| | - Fabrice Armougom
- Unité de Recherche en Maladies Infectieuses et Tropicales
Emergentes, CNRS-IRD, UMR 6236, Faculté de Médecine,
Université de la Méditerranée, Marseille,
France
| | - Pascal Barbry
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR
6079 CNRS/UNSA, Sophia Antipolis, France
| | - Richard Thiéry
- Unité de Pathologie des Ruminants, Agence Française de
Sécurité Sanitaire des Aliments (AFSSA) Sophia Antipolis,
France
| | - Didier Raoult
- Unité de Recherche en Maladies Infectieuses et Tropicales
Emergentes, CNRS-IRD, UMR 6236, Faculté de Médecine,
Université de la Méditerranée, Marseille,
France
- * E-mail:
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Cho BA, Cho NH, Min CK, Kim SY, Yang JS, Lee JR, Jung JW, Lee WC, Kim K, Lee MK, Kim S, Kim KP, Seong SY, Choi MS, Kim IS. Global gene expression profile of Orientia tsutsugamushi. Proteomics 2010; 10:1699-715. [PMID: 20186754 DOI: 10.1002/pmic.200900633] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Orientia tsutsugamushi, an obligate intracellular bacterium, is the causative agent of Scrub typhus. The control mechanisms for bacterial gene expression are largely unknown. Here, the global gene expression of O. tsutsugamushi within eukaryotic cells was examined using a microarray and proteomic approaches for the first time. These approaches identified 643 genes, corresponding to approximately 30% of the genes encoded in the genome. The majority of expressed genes belonged to several functional categories including protein translation, protein processing/secretion, and replication/repair. We also searched the conserved sequence blocks (CSBs) in the O. tsutsugamushi genome which is unique in that up to 40% of its genome consists of dispersed repeated sequences. Although extensive shuffling of genomic sequences was observed between two different strains, 204 CSBs, covering 48% of the genome, were identified. When combining the data of CSBs and global gene expression, the CSBs correlates well with the location of expressed genes, suggesting the functional conservation between gene expression and genomic location. Finally, we compared the gene expression of the bacteria-infected fibroblasts and macrophages using microarray analysis. Some major changes were the downregulation of genes involved in translation, protein processing and secretion, which correlated with the reduction in bacterial translation rates and growth within macrophages.
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Affiliation(s)
- Bon-A Cho
- Department of Microbiology and Immunology, College of Medicine and Institute of Endemic Diseases, Seoul National University Medical Research Center, Seoul, Korea
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Leroy Q, Raoult D. Review of microarray studies for host-intracellular pathogen interactions. J Microbiol Methods 2010; 81:81-95. [PMID: 20188126 DOI: 10.1016/j.mimet.2010.02.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 02/12/2010] [Accepted: 02/16/2010] [Indexed: 12/17/2022]
Abstract
Obligate intracellular bacteria are privileged soldiers on the battlefield that represent host-pathogen interactions. Microarrays are a powerful technology that can increase our knowledge about how bacteria respond to and interact with their hosts. This review summarizes the limitations inherent to host-pathogen interaction studies and essential strategies to improve microarray investigations of intracellular bacteria. We have compiled the comparative genomic and gene expression analyses of obligate intracellular bacteria currently available from microarrays. In this review we explore ways in which microarrays can be used to identify polymorphisms in different obligate intracellular bacteria such as Coxiella burnetii, Chlamydia trachomatis, Ehrlichia chaffeensis, Rickettsia prowazekii and Tropheryma whipplei. These microarray studies reveal that, while genomic content is highly conserved in obligate intracellular bacteria, genetic polymorphisms can potentially occur to increase bacterial pathogenesis. Additionally, changes in the gene expression of C. trachomatis throughout its life cycle, as well as changes in the gene expression profile of the pathogens R. prowazekii, Rickettsia rickettsii, Rickettsia typhi, T. whipplei and C. trachomatis following environmental changes, are discussed. Finally, an in vivo model of Rickettsia conorii within the skin is discussed. The gene expression analyses highlight the capacity of obligate intracellular bacteria to adapt to environmental changes and potentially to thwart the host response.
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Affiliation(s)
- Quentin Leroy
- Université de la Méditerranée, URMITE IRD-CNRS 6236, Faculté de Médecine, 27 Bd Jean Moulin, 13385 Marseille cedex 05, France
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Felsheim RF, Kurtti TJ, Munderloh UG. Genome sequence of the endosymbiont Rickettsia peacockii and comparison with virulent Rickettsia rickettsii: identification of virulence factors. PLoS One 2009; 4:e8361. [PMID: 20027221 PMCID: PMC2791219 DOI: 10.1371/journal.pone.0008361] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Accepted: 11/20/2009] [Indexed: 11/26/2022] Open
Abstract
Rickettsia peacockii, also known as the East Side Agent, is a non-pathogenic obligate intracellular bacterium found as an endosymbiont in Dermacentor andersoni ticks in the western USA and Canada. Its presence in ticks is correlated with reduced prevalence of Rickettsia rickettsii, the agent of Rocky Mountain Spotted Fever. It has been proposed that a virulent SFG rickettsia underwent changes to become the East Side Agent. We determined the genome sequence of R. peacockii and provide a comparison to a closely related virulent R. rickettsii. The presence of 42 chromosomal copies of the ISRpe1 transposon in the genome of R. peacockii is associated with a lack of synteny with the genome of R. rickettsii and numerous deletions via recombination between transposon copies. The plasmid contains a number of genes from distantly related organisms, such as part of the glycosylation island of Pseudomonas aeruginosa. Genes deleted or mutated in R. peacockii which may relate to loss of virulence include those coding for an ankyrin repeat containing protein, DsbA, RickA, protease II, OmpA, ScaI, and a putative phosphoethanolamine transferase. The gene coding for the ankyrin repeat containing protein is especially implicated as it is mutated in R. rickettsii strain Iowa, which has attenuated virulence. Presence of numerous copies of the ISRpe1 transposon, likely acquired by lateral transfer from a Cardinium species, are associated with extensive genomic reorganization and deletions. The deletion and mutation of genes possibly involved in loss of virulence have been identified by this genomic comparison. It also illustrates that the introduction of a transposon into the genome can have varied effects; either correlating with an increase in pathogenicity as in Francisella tularensis or a loss of pathogenicity as in R. peacockii and the recombination enabled by multiple transposon copies can cause significant deletions in some genomes while not in others.
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Affiliation(s)
- Roderick F. Felsheim
- Department of Entomology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Timothy J. Kurtti
- Department of Entomology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Ulrike G. Munderloh
- Department of Entomology, University of Minnesota, Saint Paul, Minnesota, United States of America
- * E-mail:
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