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Arce-Gorvel V, Hysenaj L, de Laval B, Sieweke MH, Sarrazin S, Gorvel JP. [The dance between Brucella and hematopoietic stem cells]. Med Sci (Paris) 2023; 39:822-824. [PMID: 38018922 DOI: 10.1051/medsci/2023152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2023] Open
Affiliation(s)
- Vilma Arce-Gorvel
- Aix Marseille univ, CNRS, Inserm, Centre d'immunologie de Marseille-Luminy, Marseille, France
| | - Lisiena Hysenaj
- Aix Marseille univ, CNRS, Inserm, Centre d'immunologie de Marseille-Luminy, Marseille, France - Department of anatomy, University of California, San Francisco, États-Unis
| | - Bérengère de Laval
- Aix Marseille univ, CNRS, Inserm, Centre d'immunologie de Marseille-Luminy, Marseille, France
| | - Michael H Sieweke
- Aix Marseille univ, CNRS, Inserm, Centre d'immunologie de Marseille-Luminy, Marseille, France - Center for regenerative therapies Dresden, Technische Universität Dresden, Dresde, Allemagne
| | - Sandrine Sarrazin
- Aix Marseille univ, CNRS, Inserm, Centre d'immunologie de Marseille-Luminy, Marseille, France
| | - Jean-Pierre Gorvel
- Aix Marseille univ, CNRS, Inserm, Centre d'immunologie de Marseille-Luminy, Marseille, France
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2
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Hysenaj L, de Laval B, Arce-Gorvel V, Bosilkovski M, González-Espinoza G, Debroas G, Sieweke MH, Sarrazin S, Gorvel JP. CD150-dependent hematopoietic stem cell sensing of Brucella instructs myeloid commitment. J Exp Med 2023; 220:e20210567. [PMID: 37067792 PMCID: PMC10114919 DOI: 10.1084/jem.20210567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 01/05/2023] [Accepted: 03/13/2023] [Indexed: 04/18/2023] Open
Abstract
So far, hematopoietic stem cells (HSC) are considered the source of mature immune cells, the latter being the only ones capable of mounting an immune response. Recent evidence shows HSC can also directly sense cytokines released upon infection/inflammation and pathogen-associated molecular pattern interaction while keeping a long-term memory of previously encountered signals. Direct sensing of danger signals by HSC induces early myeloid commitment, increases myeloid effector cell numbers, and contributes to an efficient immune response. Here, by using specific genetic tools on both the host and pathogen sides, we show that HSC can directly sense B. abortus pathogenic bacteria within the bone marrow via the interaction of the cell surface protein CD150 with the bacterial outer membrane protein Omp25, inducing efficient functional commitment of HSC to the myeloid lineage. This is the first demonstration of direct recognition of a live pathogen by HSC via CD150, which attests to a very early contribution of HSC to immune response.
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Affiliation(s)
- Lisiena Hysenaj
- Aix Marseille University, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d’Immunologie de Marseille-Luminy, Marseille, France
- Department of Anatomy, University of California, San Francisco, San Francisco, CA, USA
| | - Bérengère de Laval
- Aix Marseille University, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d’Immunologie de Marseille-Luminy, Marseille, France
| | - Vilma Arce-Gorvel
- Aix Marseille University, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d’Immunologie de Marseille-Luminy, Marseille, France
| | - Mile Bosilkovski
- University Clinic for Infectious Diseases and Febrile Conditions, Skopje, Republic of North Macedonia
| | - Gabriela González-Espinoza
- Aix Marseille University, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d’Immunologie de Marseille-Luminy, Marseille, France
| | - Guilhaume Debroas
- Aix Marseille University, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d’Immunologie de Marseille-Luminy, Marseille, France
| | - Michael H. Sieweke
- Aix Marseille University, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d’Immunologie de Marseille-Luminy, Marseille, France
- Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Sandrine Sarrazin
- Aix Marseille University, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d’Immunologie de Marseille-Luminy, Marseille, France
| | - Jean-Pierre Gorvel
- Aix Marseille University, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d’Immunologie de Marseille-Luminy, Marseille, France
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3
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de Carvalho TP, da Silva LA, Castanheira TLL, de Souza TD, da Paixão TA, Lazaro-Anton L, Tsolis RM, Santos RL. Cell and Tissue Tropism of Brucella spp. Infect Immun 2023; 91:e0006223. [PMID: 37129522 PMCID: PMC10187126 DOI: 10.1128/iai.00062-23] [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] [Indexed: 05/03/2023] Open
Abstract
Brucella spp. are facultatively intracellular bacteria that can infect, survive, and multiply in various host cell types in vivo and/or in vitro. The genus Brucella has markedly expanded in recent years with the identification of novel species and hosts, which has revealed additional information about the cell and tissue tropism of these pathogens. Classically, Brucella spp. are considered to have tropism for organs that contain large populations of phagocytes such as lymph nodes, spleen, and liver, as well as for organs of the genital system, including the uterus, epididymis, testis, and placenta. However, experimental infections of several different cultured cell types indicate that Brucella may actually have a broader cell tropism than previously thought. Indeed, recent studies indicate that certain Brucella species in particular hosts may display a pantropic distribution in vivo. This review discusses the available knowledge on cell and tissue tropism of Brucella spp. in natural infections of various host species, as well as in experimental animal models and cultured cells.
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Affiliation(s)
- Thaynara Parente de Carvalho
- Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
- Department of Medical Microbiology and Immunology, University of California – Davis, Davis, California, USA
| | - Laice Alves da Silva
- Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Thaís Larissa Lourenço Castanheira
- Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
- Instituto Federal de Educação Ciência e Tecnologia do Norte de Minas Gerais, Salinas, Brazil
| | - Tayse Domingues de Souza
- Escuela de Medicina Veterinaria, Facultad de Agronomía e Ingeniería Forestal, Facultad de Ciencias Biológicas y Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Tatiane Alves da Paixão
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Leticia Lazaro-Anton
- Department of Medical Microbiology and Immunology, University of California – Davis, Davis, California, USA
| | - Renee M. Tsolis
- Department of Medical Microbiology and Immunology, University of California – Davis, Davis, California, USA
| | - Renato Lima Santos
- Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
- Department of Medical Microbiology and Immunology, University of California – Davis, Davis, California, USA
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4
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González-Espinoza G, Arce-Gorvel V, Mémet S, Gorvel JP. Brucella: Reservoirs and Niches in Animals and Humans. Pathogens 2021; 10:pathogens10020186. [PMID: 33572264 PMCID: PMC7915599 DOI: 10.3390/pathogens10020186] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 02/02/2021] [Accepted: 02/05/2021] [Indexed: 01/18/2023] Open
Abstract
Brucella is an intracellular bacterium that causes abortion, reproduction failure in livestock and leads to a debilitating flu-like illness with serious chronic complications if untreated in humans. As a successful intracellular pathogen, Brucella has developed strategies to avoid recognition by the immune system of the host and promote its survival and replication. In vivo, Brucellae reside mostly within phagocytes and other cells including trophoblasts, where they establish a preferred replicative niche inside the endoplasmic reticulum. This process is central as it gives Brucella the ability to maintain replicating-surviving cycles for long periods of time, even at low bacterial numbers, in its cellular niches. In this review, we propose that Brucella takes advantage of the environment provided by the cellular niches in which it resides to generate reservoirs and disseminate to other organs. We will discuss how the favored cellular niches for Brucella infection in the host give rise to anatomical reservoirs that may lead to chronic infections or persistence in asymptomatic subjects, and which may be considered as a threat for further contamination. A special emphasis will be put on bone marrow, lymph nodes, reproductive and for the first time adipose tissues, as well as wildlife reservoirs.
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Abstract
Brucellosis is a bacterial disease of domestic animals and humans. The pathogenic ability of Brucella organisms relies on their stealthy strategy and their capacity to replicate within host cells and to induce long-lasting infections. Brucella organisms barely induce neutrophil activation and survive within these leukocytes by resisting microbicidal mechanisms. Very few Brucella-infected neutrophils are found in the target organs, except for the bone marrow, early in infection. Still, Brucella induces a mild reactive oxygen species formation and, through its lipopolysaccharide, promotes the premature death of neutrophils, which release chemokines and express "eat me" signals. This effect drives the phagocytosis of infected neutrophils by mononuclear cells that become thoroughly susceptible to Brucella replication and vehicles for bacterial dispersion. The premature death of the infected neutrophils proceeds without NETosis, necrosis/oncosis, or classical apoptosis morphology. In the absence of neutrophils, the Th1 response exacerbates and promotes bacterial removal, indicating that Brucella-infected neutrophils dampen adaptive immunity. This modulatory effect opens a window for bacterial dispersion in host tissues before adaptive immunity becomes fully activated. However, the hyperactivation of immunity is not without a price, since neutropenic Brucella-infected animals develop cachexia in the early phases of the disease. The delay in the immunological response seems a sine qua non requirement for the development of long-lasting brucellosis. This property may be shared with other pathogenic alphaproteobacteria closely related to Brucella We propose a model in which Brucella-infected polymorphonuclear neutrophils (PMNs) function as "Trojan horse" vehicles for bacterial dispersal and as modulators of the Th1 adaptive immunity in infection.
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Degos C, Hysenaj L, Gonzalez‐Espinoza G, Arce‐Gorvel V, Gagnaire A, Papadopoulos A, Pasquevich KA, Méresse S, Cassataro J, Mémet S, Gorvel J. Omp25‐dependent engagement of SLAMF1 byBrucella abortusin dendritic cells limits acute inflammation and favours bacterial persistence in vivo. Cell Microbiol 2020; 22:e13164. [DOI: 10.1111/cmi.13164] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 12/10/2019] [Accepted: 12/16/2019] [Indexed: 12/15/2022]
Affiliation(s)
- Clara Degos
- CNRS, INSERM, CIML, Centre d'Immunologie de Marseille‐LuminyAix‐Marseille University Marseille France
| | - Lisiena Hysenaj
- CNRS, INSERM, CIML, Centre d'Immunologie de Marseille‐LuminyAix‐Marseille University Marseille France
| | | | - Vilma Arce‐Gorvel
- CNRS, INSERM, CIML, Centre d'Immunologie de Marseille‐LuminyAix‐Marseille University Marseille France
| | - Aurélie Gagnaire
- CNRS, INSERM, CIML, Centre d'Immunologie de Marseille‐LuminyAix‐Marseille University Marseille France
| | - Alexia Papadopoulos
- CNRS, INSERM, CIML, Centre d'Immunologie de Marseille‐LuminyAix‐Marseille University Marseille France
| | - Karina Alejandra Pasquevich
- Instituto de Investigaciones BiotecnológicasUniversidad Nacional de San Martín (UNSAM)‐CONICET Buenos Aires Argentina
| | - Stéphane Méresse
- CNRS, INSERM, CIML, Centre d'Immunologie de Marseille‐LuminyAix‐Marseille University Marseille France
| | - Juliana Cassataro
- Instituto de Investigaciones BiotecnológicasUniversidad Nacional de San Martín (UNSAM)‐CONICET Buenos Aires Argentina
| | - Sylvie Mémet
- CNRS, INSERM, CIML, Centre d'Immunologie de Marseille‐LuminyAix‐Marseille University Marseille France
| | - Jean‐Pierre Gorvel
- CNRS, INSERM, CIML, Centre d'Immunologie de Marseille‐LuminyAix‐Marseille University Marseille France
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7
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Reyes AWB, Vu SH, Huy TXN, Min W, Lee HJ, Chang HH, Lee JH, Kim S. Adenosine receptor Adora2b antagonism attenuates Brucella abortus 544 infection in professional phagocyte RAW 264.7 cells and BALB/c mice. Vet Microbiol 2020; 242:108586. [PMID: 32122590 DOI: 10.1016/j.vetmic.2020.108586] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/09/2020] [Accepted: 01/10/2020] [Indexed: 01/18/2023]
Abstract
Brucella as a stealthy intracellular pathogen avoids activation of innate immune response. Here we investigated the contribution of an adenosine receptor, Adora2b, during Brucella infection in professional phagocyte RAW 264.7 cells and in a murine model. Adora2b-deficient cells showed attenuated Brucella internalization and intracellular survival with enhanced release of IL-6, TNF-α, IL-12 and MCP-1. In addition, blockade of Adora2b using MRS 1754 treatment in mice resulted in increased total weight of the spleens but suppressed bacterial burden in these organs accompanied by elevated levels of IL-6, IFN-γ, TNF-α, IL-12 and MCP-1, while reduced IL-10. Overall, we proposed that the Adora2b participates in the successful phagocytic pathway and intracellular survival of Brucella in RAW 264.7 cells, and could be a potential therapeutic target for the treatment of acute brucellosis in animals.
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Affiliation(s)
| | - Son Hai Vu
- Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Republic of Korea
| | - Tran Xuan Ngoc Huy
- Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Republic of Korea
| | - WonGi Min
- Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Republic of Korea
| | - Hu Jang Lee
- Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Republic of Korea
| | - Hong Hee Chang
- Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Republic of Korea
| | - John Hwa Lee
- College of Veterinary Medicine, Chonbuk National University, Iksan, 54596, Republic of Korea
| | - Suk Kim
- Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Republic of Korea.
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Demars A, Lison A, Machelart A, Van Vyve M, Potemberg G, Vanderwinden JM, De Bolle X, Letesson JJ, Muraille E. Route of Infection Strongly Impacts the Host-Pathogen Relationship. Front Immunol 2019; 10:1589. [PMID: 31354728 PMCID: PMC6637429 DOI: 10.3389/fimmu.2019.01589] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 06/25/2019] [Indexed: 12/24/2022] Open
Abstract
Live attenuated vaccines play a key role in the control of many human and animal pathogens. Their rational development is usually helped by identification of the reservoir of infection, the lymphoid subpopulations associated with protective immunity as well as the virulence genes involved in pathogen persistence. Here, we compared the course of Brucella melitensis infection in C57BL/6 mice infected via intraperitoneal (i.p.), intranasal (i.n.) and intradermal (i.d.) route and demonstrated that the route of infection strongly impacts all of these parameters. Following i.p. and i.n. infection, most infected cells observed in the spleen or lung were F4/80+ myeloid cells. In striking contrast, infected Ly6G+ neutrophils and CD140a+ fibroblasts were also observed in the skin after i.d. infection. The virB operon encoding for the type IV secretion system is considered essential to deflecting vacuolar trafficking in phagocytic cells and allows Brucella to multiply and persist. Unexpectedly, the ΔvirB Brucella strain, which does not persist in the lung after i.n. infection, persists longer in skin tissues than the wild strain after i.d. infection. While the CD4+ T cell-mediated Th1 response is indispensable to controlling the Brucella challenge in the i.p. model, it is dispensable for the control of Brucella in the i.d. and i.n. models. Similarly, B cells are indispensable in the i.p. and i.d. models but dispensable in the i.n. model. γδ+ T cells appear able to compensate for the absence of αβ+ T cells in the i.d. model but not in the other models. Taken together, our results demonstrate the crucial importance of the route of infection for the host pathogen relationship.
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Affiliation(s)
- Aurore Demars
- Unité de Recherche en Biologie des Microorganismes, Laboratoire d'Immunologie et de Microbiologie, NARILIS, Université de Namur, Namur, Belgium
| | - Aurore Lison
- Unité de Recherche en Biologie des Microorganismes, Laboratoire d'Immunologie et de Microbiologie, NARILIS, Université de Namur, Namur, Belgium
| | - Arnaud Machelart
- Unité de Recherche en Biologie des Microorganismes, Laboratoire d'Immunologie et de Microbiologie, NARILIS, Université de Namur, Namur, Belgium
| | - Margaux Van Vyve
- Unité de Recherche en Biologie des Microorganismes, Laboratoire d'Immunologie et de Microbiologie, NARILIS, Université de Namur, Namur, Belgium
| | - Georges Potemberg
- Unité de Recherche en Biologie des Microorganismes, Laboratoire d'Immunologie et de Microbiologie, NARILIS, Université de Namur, Namur, Belgium
| | | | - Xavier De Bolle
- Unité de Recherche en Biologie des Microorganismes, Laboratoire d'Immunologie et de Microbiologie, NARILIS, Université de Namur, Namur, Belgium
| | - Jean-Jacques Letesson
- Unité de Recherche en Biologie des Microorganismes, Laboratoire d'Immunologie et de Microbiologie, NARILIS, Université de Namur, Namur, Belgium
| | - Eric Muraille
- Unité de Recherche en Biologie des Microorganismes, Laboratoire d'Immunologie et de Microbiologie, NARILIS, Université de Namur, Namur, Belgium
- Laboratoire de Parasitologie, Faculté de Médecine, Université Libre de Bruxelles, Bruxelles, Belgium
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Gutiérrez-Jiménez C, Mora-Cartín R, Altamirano-Silva P, Chacón-Díaz C, Chaves-Olarte E, Moreno E, Barquero-Calvo E. Neutrophils as Trojan Horse Vehicles for Brucella abortus Macrophage Infection. Front Immunol 2019; 10:1012. [PMID: 31134082 PMCID: PMC6514781 DOI: 10.3389/fimmu.2019.01012] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 04/23/2019] [Indexed: 01/18/2023] Open
Abstract
Brucella abortus is a stealthy intracellular bacterial pathogen of animals and humans. This bacterium promotes the premature cell death of neutrophils (PMN) and resists the killing action of these leukocytes. B. abortus-infected PMNs presented phosphatidylserine (PS) as “eat me” signal on the cell surface. This signal promoted direct contacts between PMNs and macrophages (Mϕs) and favored the phagocytosis of the infected dying PMNs. Once inside Mϕs, B. abortus replicated within Mϕs at significantly higher numbers than when Mϕs were infected with bacteria alone. The high levels of the regulatory IL-10 and the lower levels of proinflammatory TNF-α released by the B. abortus-PMN infected Mϕs, at the initial stages of the infection, suggested a non-phlogistic phagocytosis mechanism. Thereafter, the levels of proinflammatory cytokines increased in the B. abortus-PMN-infected Mϕs. Still, the efficient bacterial replication proceeded, regardless of the cytokine levels and Mϕ type. Blockage of PS with Annexin V on the surface of B. abortus-infected PMNs hindered their contact with Mϕs and hampered the association, internalization, and replication of B. abortus within these cells. We propose that B. abortus infected PMNs serve as “Trojan horse” vehicles for the efficient dispersion and replication of the bacterium within the host.
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Affiliation(s)
- Cristina Gutiérrez-Jiménez
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica
| | - Ricardo Mora-Cartín
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica
| | - Pamela Altamirano-Silva
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Carlos Chacón-Díaz
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Esteban Chaves-Olarte
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Edgardo Moreno
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica
| | - Elías Barquero-Calvo
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica
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Neutrophils Dampen Adaptive Immunity in Brucellosis. Infect Immun 2019; 87:IAI.00118-19. [PMID: 30804100 PMCID: PMC6479033 DOI: 10.1128/iai.00118-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 02/18/2019] [Indexed: 01/03/2023] Open
Abstract
Brucella organisms are intracellular stealth pathogens of animals and humans. The bacteria overcome the assault of innate immunity at early stages of an infection. Brucella organisms are intracellular stealth pathogens of animals and humans. The bacteria overcome the assault of innate immunity at early stages of an infection. Removal of polymorphonuclear neutrophils (PMNs) at the onset of adaptive immunity against Brucella abortus favored bacterial elimination in mice. This was associated with higher levels of interferon gamma (IFN-γ) and a higher proportion of cells expressing interleukin 6 (IL-6) and inducible nitric oxide synthase (iNOS), compatible with M1 macrophages, in PMN-depleted B. abortus-infected (PMNd-Br) mice. At later times in the acute infection phase, the amounts of IFN-γ fell while IL-6, IL-10, and IL-12 became the predominant cytokines in PMNd-Br mice. IL-4, IL-1β, and tumor necrosis factor alpha (TNF-α) remained at background levels at all times of the infection. Depletion of PMNs at the acute stages of infection promoted the premature resolution of spleen inflammation. The efficient removal of bacteria in the PMNd-Br mice was not due to an increase of antibodies, since the immunoglobulin isotype responses to Brucella antigens were dampened. Anti-Brucella antibodies abrogated the production of IL-6, IL-10, and IL-12 but did not affect the levels of IFN-γ at later stages of infection in PMNd-Br mice. These results demonstrate that PMNs have an active role in modulating the course of B. abortus infection after the adaptive immune response has already developed.
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