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Eskeland S, Bø-Granquist EG, Stuen S, Lybeck K, Wilhelmsson P, Lindgren PE, Makvandi-Nejad S. Temporal patterns of gene expression in response to inoculation with a virulent Anaplasma phagocytophilum strain in sheep. Sci Rep 2023; 13:20399. [PMID: 37989861 PMCID: PMC10663591 DOI: 10.1038/s41598-023-47801-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 11/18/2023] [Indexed: 11/23/2023] Open
Abstract
The aim of this study was to characterize the gene expression of host immune- and cellular responses to a Norwegian virulent strain of Anaplasma phagocytophilum, the cause of tick-borne fever in sheep. Ten sheep were intravenously inoculated with a live virulent strain of A. phagocytophilum. Clinical-, observational-, hematological data as well as bacterial load, flow cytometric cell count data from peripheral blood mononuclear cells and host's gene expression post infection was analysed. The transcriptomic data were assessed for pre-set time points over the course of 22 days following the inoculation. Briefly, all inoculated sheep responded with clinical signs of infection 3 days post inoculation and onwards with maximum bacterial load observed on day 6, consistent with tick-borne fever. On days, 3-8, the innate immune responses and effector processes such as IFN1 signaling pathways and cytokine mediated signaling pathways were observed. Several pathways associated with the adaptive immune responses, namely T-cell activation, humoral immune responses, B-cell activation, and T- and B-cell differentiation dominated on the days of 8, 10 and 14. Flow-cytometric analysis of the PBMCs showed a reduction in CD4+CD25+ cells on day 10 and 14 post-inoculation and a skewed CD4:CD8 ratio indicating a reduced activation and proliferation of CD4-T-cells. The genes of important co-stimulatory molecules such as CD28 and CD40LG, important in T- and B-cell activation and proliferation, did not significantly change or experienced downregulation throughout the study. The absence of upregulation of several co-stimulatory molecules might be one possible explanation for the low activation and proliferation of CD4-T-cells during A. phagocytophilum infection, indicating a suboptimal CD4-T-cell response. The upregulation of T-BET, EOMES and IFN-γ on days 8-14 post inoculation, indicates a favoured CD4 Th1- and CD8-response. The dynamics and interaction between CD4+CD25+ and co-stimulatory molecules such as CD28, CD80, CD40 and CD40LG during infection with A. phagocytophilum in sheep needs further investigation in the future.
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Affiliation(s)
- Sveinung Eskeland
- Department of Production Animal Clinical Science, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Elizabeth Stephansens Vei 15, 1433, Ås, Norway.
| | - Erik G Bø-Granquist
- Department of Production Animal Clinical Science, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Elizabeth Stephansens Vei 15, 1433, Ås, Norway
| | - Snorre Stuen
- Department of Production Animal Clinical Science, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Kyrkjevegen 332/334, 4325, Sandnes, Norway
| | - Kari Lybeck
- Norwegian Veterinary Institute, Elizabeth Stephansens Vei 1, 1433, Ås, Norway
| | - Peter Wilhelmsson
- Division of Clinical Microbiology, Laboratory Medicine, National Reference Laboratory for Borrelia and Other Tick-Borne Bacteria, Region Jönköping County, 553 05, Jönköping, Sweden
| | - Per-Eric Lindgren
- Division of Inflammation and Infection, Department of Biomedical and Clinical Sciences, Linköping University, 581 83, Linköping, Sweden
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Londoño AF, Scorpio DG, Dumler JS. Innate immunity in rickettsial infections. Front Cell Infect Microbiol 2023; 13:1187267. [PMID: 37228668 PMCID: PMC10203653 DOI: 10.3389/fcimb.2023.1187267] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 04/19/2023] [Indexed: 05/27/2023] Open
Abstract
Rickettsial agents are a diverse group of alpha-proteobacteria within the order Rickettsiales, which possesses two families with human pathogens, Rickettsiaceae and Anaplasmataceae. These obligate intracellular bacteria are most frequently transmitted by arthropod vectors, a first step in the pathogens' avoidance of host cell defenses. Considerable study of the immune responses to infection and those that result in protective immunity have been conducted. Less study has focused on the initial events and mechanism by which these bacteria avoid the innate immune responses of the hosts to survive within and propagate from host cells. By evaluating the major mechanisms of evading innate immunity, a range of similarities among these bacteria become apparent, including mechanisms to escape initial destruction in phagolysosomes of professional phagocytes, those that dampen the responses of innate immune cells or subvert signaling and recognition pathways related to apoptosis, autophagy, proinflammatory responses, and mechanisms by which these microbes attach to and enter cells or those molecules that trigger the host responses. To illustrate these principles, this review will focus on two common rickettsial agents that occur globally, Rickettsia species and Anaplasma phagocytophilum.
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Affiliation(s)
- Andrés F. Londoño
- The Henry M. Jackson Foundation for Advancement in Military Medicine, Bethesda, MD, United States
- Department of Pathology, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Diana G. Scorpio
- Host-Pathogen Interactions Program, Texas Biomedical Research Institute, San Antonio, TX, United States
| | - J. Stephen Dumler
- Department of Pathology, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
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Underwood J, Harvey C, Lohstroh E, Pierce B, Chambers C, Guzman Valencia S, Oliva Chávez AS. Anaplasma phagocytophilum Transmission Activates Immune Pathways While Repressing Wound Healing in the Skin. LIFE (BASEL, SWITZERLAND) 2022; 12:life12121965. [PMID: 36556330 PMCID: PMC9781593 DOI: 10.3390/life12121965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 11/18/2022] [Accepted: 11/21/2022] [Indexed: 11/25/2022]
Abstract
Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis (HGA), is an obligate intracellular bacterium transmitted by the bite of black-legged ticks, Ixodes scapularis. The main host cells in vertebrates are neutrophils. However, the first site of entry is in the skin during tick feeding. Given that the initial responses within skin are a crucial determinant of disease outcome in vector-borne diseases, we used a non-biased approach to characterize the transcriptional changes that take place at the bite during I. scapularis feeding and A. phagocytophilum transmission. Experimentally infected ticks were allowed to feed for 3 days on C57BL/6J mice to allow bacterial transmission and establishment. Skin biopsies were taken from the attachment site of uninfected ticks and A. phagocytophilum-infected ticks. Skin without ticks (intact skin) was used as baseline. RNA was isolated and sequenced using next-generation sequencing (NGS). The differentially expressed genes were used to identify over-represented pathways by gene ontology (GO) and pathway enrichment (PE). Anaplasma phagocytophilum transmission resulted in the activation of interferon signaling and neutrophil chemotaxis pathways in the skin. Interestingly, it also led to the downregulation of genes encoding extracellular matrix (ECM) components, and upregulation of metalloproteinases, suggesting that A. phagocytophilum delays wound healing responses and may increase vascular permeability at the bite site.
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Affiliation(s)
- Jacob Underwood
- Department of Entomology, Texas A&M University, College Station, TX 77845, USA
- Navy Entomology Center of Excellence, United States Navy, Jacksonville, FL 32212, USA
| | - Cristina Harvey
- Department of Entomology, Texas A&M University, College Station, TX 77845, USA
| | - Elizabeth Lohstroh
- Department of Entomology, Texas A&M University, College Station, TX 77845, USA
| | - Branden Pierce
- Department of Entomology, Texas A&M University, College Station, TX 77845, USA
| | - Cross Chambers
- Department of Entomology, Texas A&M University, College Station, TX 77845, USA
| | | | - Adela S. Oliva Chávez
- Department of Entomology, Texas A&M University, College Station, TX 77845, USA
- Correspondence: ; Tel.: +1-979-845-1946
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Dumler JS, Lichay M, Chen WH, Rennoll-Bankert KE, Park JH. Anaplasma phagocytophilum Activates NF-κB Signaling via Redundant Pathways. Front Public Health 2020; 8:558283. [PMID: 33194960 PMCID: PMC7661751 DOI: 10.3389/fpubh.2020.558283] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 09/22/2020] [Indexed: 11/28/2022] Open
Abstract
Anaplasma phagocytophilum subverts neutrophil function permitting intracellular survival, propagation and transmission. Sustained pro-inflammatory response, recruitment of new host cells for population expansion, and delayed apoptosis are associated with prolonged nuclear presence of NF-κB. We investigated NF-κB signaling and transcriptional activity with A. phagocytophilum infection using inhibitors of NF-κB signaling pathways, and through silencing of signaling pathway genes. How inhibitors or silencing affected A. phagocytophilum growth, inflammatory response (transcription of the κB-enhanced genes CXCL8 and MMP9), and NF-κB signaling pathway gene expression were tested. Among A. phagocytophilum-infected HL-60 cells, nuclear NF-κB p50, p65, and p52 were detected by immunoblots or iTRAQ proteomics. A. phagocytophilum growth was affected most by the IKKαβ inhibitor wedelolactone (reductions of 96 to 99%) as compared with SC-514 that selectively inhibits IKKβ, illustrating a role for the non-canonical pathway. Wedelolactone inhibited transcription of both CXCL8 (p = 0.001) and MMP9 (p = 0.002) in infected cells. Compared to uninfected THP-1 cells, A. phagocytophilum infection led to >2-fold down regulation of 64 of 92 NF-κB signaling pathway genes, and >2-fold increased expression in only 4. Wedelolactone and SC-514 reversed downregulation in all 64 and 45, respectively, of the genes down-regulated by infection, but decreased expression in 1 gene with SC-514 only. Silencing of 20 NF-κB signal pathway genes increased bacterial growth in 12 (IRAK1, MAP3K1, NFKB1B, MAP3K7, TICAM2, TLR3, TRADD, TRAF3, CHUK, IRAK2, LTBR, and MALT1). Most findings support canonical pathway activation; however, the presence of NFKB2 in infected cell nuclei, selective non-canonical pathway inhibitors that dampen CXCL8 and MMP9 transcription with infection, upregulation of non-canonical pathway target genes CCL13 and CCL19, enhanced bacterial growth with TRAF3 and LTBR silencing provide evidence for non-canonical pathway signaling. Whether this impacts distinct inflammatory processes that underlie disease, and whether and how A. phagocytophilum subverts NF-κB signaling via these pathways, need to be investigated.
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Affiliation(s)
- J Stephen Dumler
- Department of Pathology, F. Edward Hébert School of Medicine, Uniformed Services University for the Health Sciences, Bethesda, MD, United States.,Division of Medical Microbiology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Marguerite Lichay
- Division of Medical Microbiology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Wan-Hsin Chen
- Division of Medical Microbiology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Kristen E Rennoll-Bankert
- Division of Medical Microbiology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Jin-Ho Park
- Division of Medical Microbiology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
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López V, Alberdi P, Fuente JDL. Common Strategies, Different Mechanisms to Infect the Host: Anaplasma and Mycobacterium. Tuberculosis (Edinb) 2018. [DOI: 10.5772/intechopen.71535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Scorpio DG, Choi KS, Dumler JS. Anaplasma phagocytophilum-Related Defects in CD8, NKT, and NK Lymphocyte Cytotoxicity. Front Immunol 2018; 9:710. [PMID: 29686681 PMCID: PMC5900440 DOI: 10.3389/fimmu.2018.00710] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 03/22/2018] [Indexed: 12/19/2022] Open
Abstract
Human granulocytic anaplasmosis, caused by the tick-transmitted Anaplasma phagocytophilum, is not controlled by innate immunity, and induces a proinflammatory disease state with innate immune cell activation. In A. phagocytophilum murine infection models, hepatic injury occurs with production of IFNγ thought to be derived from NK, NKT cells, and CD8 T lymphocytes. Specific A. phagocytophilum ligands that drive inflammation and disease are not known, but suggest a clinical and pathophysiologic basis strikingly like macrophage activation syndrome (MAS) and hemophagocytic syndrome (HPS). We studied in vivo responses of NK, NKT, and CD8 T lymphocytes from infected animals for correlates of lymphocyte-mediated cytotoxicity and examined in vitro interactions with A. phagocytophilum-loaded antigen-presenting cells (APCs). Murine splenocytes were examined and found deficient in cytotoxicity as determined by CD107a expression in vitro for specific CTL effector subsets as determined by flow cytometry. Moreover, A. phagocytophilum-loaded APCs did not lead to IFNγ production among CTLs in vitro. These findings support the concept of impaired cytotoxicity with A. phagocytophilum presentation by APCs that express MHC class I and that interact with innate and adaptive immune cells with or after infection. The findings strengthen the concept of an enhanced proinflammatory phenotype, such as MAS and HPS disease states as the basis of disease and severity with A. phagocytophilum infection, and perhaps by other obligate intracellular bacteria.
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Affiliation(s)
- Diana G Scorpio
- Vaccine Research Center, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Kyoung-Seong Choi
- College of Ecology and Environmental Science, Kyungpook National University, Sangju, South Korea
| | - J Stephen Dumler
- Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
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Lee SH, Park SY, Jang MJ, Choi KJ, Lee HK, Cho YU, Lee YS, Kim SH, Hwang SD. Clinical Isolation of Anaplasma phagocytophilum in South Korea. Am J Trop Med Hyg 2017; 97:1686-1690. [PMID: 29141715 PMCID: PMC5805025 DOI: 10.4269/ajtmh.16-0529] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 05/01/2017] [Indexed: 01/21/2023] Open
Abstract
We report the first isolation of Anaplasma phagocytophilum in South Korea. A 61-year-old woman presented with a 6-day history of fever, headache, and myalgia. Initial investigation showed neutropenia and thrombocytopenia. We diagnosed human granulocytic anaplasmosis by microscopic examination and serologic testing. The patient recovered fully without antibiotic therapy. The isolate was obtained from the patient's blood by cell culture and mouse inoculation. Its identity was confirmed by an immunofluorescence assay, sequencing of the 16S rRNA gene, msp2 (p44), and ankA genes, and staining and electron microscopy of morulae of A. phagocytophilum in cultured human promyelocytic leukemia HL-60 cells.
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Affiliation(s)
- Seung Hun Lee
- Division of Zoonoses, Center for Immunology and Pathology, Korea National Institute of Health, Korea Centers for Disease Control and Prevention, Chungcheongbuk-do, Republic of Korea
| | - Se Yoon Park
- Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
- Division of Infectious Diseases, Department of Internal Medicine, Soonchunhyang University Seoul Hospital, Soonchunhyang University College of Medicine, Seoul, Republic of Korea
| | - Mi Jin Jang
- Division of Zoonoses, Center for Immunology and Pathology, Korea National Institute of Health, Korea Centers for Disease Control and Prevention, Chungcheongbuk-do, Republic of Korea
| | - Ki Ju Choi
- Division of Biosafety Evaluation and Control, Korea National Institute of Health, Korea Centers for Disease Control and Prevention, Chungcheongbuk-do, Republic of Korea
| | - Hae Kyung Lee
- Division of Zoonoses, Center for Immunology and Pathology, Korea National Institute of Health, Korea Centers for Disease Control and Prevention, Chungcheongbuk-do, Republic of Korea
| | - Young-Uk Cho
- Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Yeong Seon Lee
- Division of Zoonoses, Center for Immunology and Pathology, Korea National Institute of Health, Korea Centers for Disease Control and Prevention, Chungcheongbuk-do, Republic of Korea
| | - Sung-Han Kim
- Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Seon Do Hwang
- Division of Zoonoses, Center for Immunology and Pathology, Korea National Institute of Health, Korea Centers for Disease Control and Prevention, Chungcheongbuk-do, Republic of Korea
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Johns JL, Discipulo ML, Koehne AL, Moorhead KA, Nagamine CM. Influence of Genetic Background on Hematologic and Histopathologic Alterations during Acute Granulocytic Anaplasmosis in 129/SvEv and C57BL/6J Mice Lacking Type I and Type II Interferon Signaling. Comp Med 2017; 67:127-137. [PMID: 28381313 PMCID: PMC5402732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 09/22/2016] [Accepted: 11/16/2016] [Indexed: 06/07/2023]
Abstract
The role of host type I IFN signaling and its interaction with other immune pathways during bacterial infections is incompletely understood. Type II IFN signaling plays a key role during numerous bacterial infections including granulocytic anaplasmosis (GA) caused by Anaplasma phagocytophilum infection. The function of combined type I and type II IFN signaling and their potential synergism during GA and similar tick-borne diseases is a topic of current research investigation. The goal of this study was to evaluate 2 mouse models of absent type I/type II IFN signaling in experimental A. phagocytophilum infection to determine the effects of background strain. Mice lacking both type I and type II IFN receptor signaling (IFNAR-/-/IFNGR-/-) on either the 129/SvEv or C57BL/6J genetic background were evaluated at days 0, 6, 8, and 12 of infection. Pathogen burden in multiple organs was largely similar between strains of infected mice, with few significant differences. Background strain influenced the immune response to infection. Mice of the 129/SvEv strain developed more severe hematologic abnormalities, particularly more severe leukocytosis with marked neutrophilia and lymphocytosis, throughout acute infection. Histopathologic changes occurred in infected mice of both strains and varied in severity by organ. 129/SvEv mice developed more severe pathologic changes in spleen and bone marrow, whereas C57BL/6J mice developed more severe renal pathology. This work highlights the importance of mouse background strain in dictating pathophysiologic response to infection and informs future work regarding the loss of type I and type II IFN signaling on the immune response during GA.
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Affiliation(s)
- Jennifer L Johns
- Department of Biomedical Sciences, Oregon State University College of Veterinary Medicine, Corvallis, Oregon;,
| | - Marielle L Discipulo
- Departments of Comparative Medicine, Stanford University School of Medicine, Stanford, California
| | - Amanda L Koehne
- Departments of Pediatrics, Stanford University School of Medicine, Stanford, California
| | - Kaitlin A Moorhead
- Departments of Comparative Medicine, Stanford University School of Medicine, Stanford, California
| | - Claude M Nagamine
- Departments of Comparative Medicine, Stanford University School of Medicine, Stanford, California
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Tsiodras S, Spanakis N, Spanakos G, Pervanidou D, Georgakopoulou T, Campos E, Petra T, Kanellopoulos P, Georgiadis G, Antalis E, Kontos V, Giannopoulos LA, Tselentis Y, Papa A, Tsakris A, Saroglou G. Fatal human anaplasmosis associated with macrophage activation syndrome in Greece and the Public Health response. J Infect Public Health 2017; 10:819-823. [PMID: 28189511 DOI: 10.1016/j.jiph.2017.01.002] [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: 07/05/2016] [Revised: 11/22/2016] [Accepted: 01/07/2017] [Indexed: 01/28/2023] Open
Abstract
Human granulocytic anaplasmosis (HGA) is a tick-borne disease caused by Anaplasma phagocytophilum that has the potential to spread in new geographical areas. The first fatal case of HGA in Greece is presented. Fever of unknown origin, renal and respiratory insufficiency and development of macrophage activation syndrome characterized the clinical presentation. Amplification and sequencing of a fragment of the groEL gene revealed the presence of A. phagocytophilum. The epidemiological and clinical features were collected during an epidemiological investigation. Public health measures were instituted by the Hellenic Centre for Disease Control and Prevention. The Public Health intervention required the collaboration of epidemiologists, veterinarians and microbiologists. Emphasis was given to communication activities and misconceptions concerning canines and their role in the disease. The emergence of human anaplasmosis in a new geographical area highlights the importance of disease awareness and of the need for continued support for tick and tick-borne disease surveillance networks.
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Affiliation(s)
- Sotirios Tsiodras
- 4th Department of Internal Medicine, University General Hospital "Attikon", National & Kapodistrian University of Athens Medical School, Athens, Greece; The Hellenic Centre for Disease Control and Prevention, Athens, Greece.
| | - Nikos Spanakis
- Department of Microbiology, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Gregory Spanakos
- The Hellenic Centre for Disease Control and Prevention, Athens, Greece
| | - Danai Pervanidou
- The Hellenic Centre for Disease Control and Prevention, Athens, Greece
| | | | | | | | | | | | - Emmanouil Antalis
- 4th Department of Internal Medicine, University General Hospital "Attikon", National & Kapodistrian University of Athens Medical School, Athens, Greece
| | - Vassileios Kontos
- Department of Parasitology, Entomology and Tropical Diseases, National School of Public Health, Athens, Greece
| | | | - Yiannis Tselentis
- Laboratory of Clinical Bacteriology, Parasitology, Zoonoses and Geographic Medicine, WHO Collaborating Center for Mediterranean Zoonoses, University of Crete, Heraklion, Crete, Greece
| | - Anna Papa
- Department of Microbiology, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Athanassios Tsakris
- Department of Microbiology, National and Kapodistrian University of Athens Medical School, Athens, Greece
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Choi KS, Scorpio DG, Dumler JS. Stat1 negatively regulates immune-mediated injury with Anaplasma phagocytophilum infection. THE JOURNAL OF IMMUNOLOGY 2014; 193:5088-98. [PMID: 25305312 DOI: 10.4049/jimmunol.1401381] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Human granulocytic anaplasmosis (HGA) is caused by the obligate intracellular bacterium Anaplasma phagocytophilum. Our data previously demonstrated that A. phagocytophilum induces an immunopathologic response by activating IFN-γ production through the Stat1 signaling pathway. In this study, we investigated the broader role of Stat1 signaling in the host response to infection with A. phagocytophilum. In Stat1 knockout (KO) compared with wild-type mice, A. phagocytophilum infection was more highly pathogenic as characterized by the unanticipated development of clinical signs in mice including markedly increased splenomegaly, more severe inflammatory splenic and hepatic histopathology, >100-fold higher blood and splenic bacterial loads, and more elevated proinflammatory cytokine/chemokine responses in serum. CD4(+) and CD8(+) T lymphocyte populations were significantly expanded in spleens of A. phagocytophilum-infected Stat1 KO mice compared with wild-type mice. The leukocyte infiltrates in the livers and spleens of A. phagocytophilum-infected Stat1 KO mice also contained expansions in neutrophil and monocyte/macrophage populations. Importantly, A. phagocytophilum-infected Stat1 KO mice did not demonstrate induction of inducible NO synthase in splenocytes. These results show that Stat1 plays an important role in controlling bacterial loads but also by unexpectedly providing an undefined mechanism for dampening of the immunopathologic response observed with A. phagocytophilum infection.
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Affiliation(s)
- Kyoung-Seong Choi
- Department of Animal Biotechnology, College of Animal Science, Kyungpook National University, Sangju 742-711, Republic of Korea; Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Diana G Scorpio
- Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205; Department of Biomedical Sciences, Ross University School of Veterinary Medicine, St. Kitts and Nevis, West Indies
| | - J Stephen Dumler
- Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205; Department of Pathology, University of Maryland, Baltimore, MD 21201; and Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201
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