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Dahmani M, Zhu JC, Cook JH, Riley SP. Anaphylatoxin signaling activates macrophages to control intracellular Rickettsia proliferation. Microbiol Spectr 2023; 11:e0253823. [PMID: 37855623 PMCID: PMC10714731 DOI: 10.1128/spectrum.02538-23] [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] [Received: 06/20/2023] [Accepted: 09/11/2023] [Indexed: 10/20/2023] Open
Abstract
IMPORTANCE Pathogenic Rickettsia species are extremely dangerous bacteria that grow within the cytoplasm of host mammalian cells. In most cases, these bacteria are able to overpower the host cell and grow within the protected environment of the cytoplasm. However, a dramatic conflict occurs when Rickettsia encounter innate immune cells; the bacteria can "win" by taking over the host, or the bacteria can "lose" if the host cell efficiently fights the infection. This manuscript examines how the immune complement system is able to detect the presence of Rickettsia and alert nearby cells. Byproducts of complement activation called anaphylatoxins are signals that "activate" innate immune cells to mount an aggressive defensive strategy. This study enhances our collective understanding of the innate immune reaction to intracellular bacteria and will contribute to future efforts at controlling these dangerous infections.
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Affiliation(s)
- Mustapha Dahmani
- Department of Veterinary Medicine, University of Maryland-College Park, College Park, Maryland, USA
| | - Jinyi C. Zhu
- Department of Veterinary Medicine, University of Maryland-College Park, College Park, Maryland, USA
| | - Jack H. Cook
- Department of Veterinary Medicine, University of Maryland-College Park, College Park, Maryland, USA
| | - Sean P. Riley
- Department of Veterinary Medicine, University of Maryland-College Park, College Park, Maryland, USA
- Virginia-Maryland College of Veterinary Medicine, College Park, Maryland, USA
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Rana VS, Kitsou C, Dumler JS, Pal U. Immune evasion strategies of major tick-transmitted bacterial pathogens. Trends Microbiol 2023; 31:62-75. [PMID: 36055896 PMCID: PMC9772108 DOI: 10.1016/j.tim.2022.08.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 07/28/2022] [Accepted: 08/01/2022] [Indexed: 12/30/2022]
Abstract
Tick-transmitted bacterial pathogens thrive in enzootic infection cycles, colonizing disparate vertebrate and arthropod tissues, often establishing persistent infections. Therefore, the evolution of robust immune evasion strategies is central to their successful persistence or transmission between hosts. To survive in nature, these pathogens must counteract a broad range of microbicidal host responses that can be localized, tissue-specific, or systemic, including a mix of these responses at the host-vector interface. Herein, we review microbial immune evasion strategies focusing on Lyme disease spirochetes and rickettsial or tularemia agents as models for extracellular and intracellular tick-borne pathogens, respectively. A better understanding of these adaptive strategies could enrich our knowledge of the infection biology of relevant tick-borne diseases, contributing to the development of future preventions.
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Affiliation(s)
- Vipin Singh Rana
- Department of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Chrysoula Kitsou
- Department of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - J Stephen Dumler
- Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Utpal Pal
- Department of Veterinary Medicine, University of Maryland, College Park, MD, USA.
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Huang D, Luo J, OuYang X, Song L. Subversion of host cell signaling: The arsenal of Rickettsial species. Front Cell Infect Microbiol 2022; 12:995933. [PMID: 36389139 PMCID: PMC9659576 DOI: 10.3389/fcimb.2022.995933] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Accepted: 10/04/2022] [Indexed: 10/10/2023] Open
Abstract
Rickettsia is a genus of nonmotile, Gram-negative, non-spore-forming, highly pleomorphic bacteria that cause severe epidemic rickettsioses. The spotted fever group and typhi group are major members of the genus Rickettsia. Rickettsial species from the two groups subvert diverse host cellular processes, including membrane dynamics, actin cytoskeleton dynamics, phosphoinositide metabolism, intracellular trafficking, and immune defense, to promote their host colonization and intercellular transmission through secreted effectors (virulence factors). However, lineage-specific rickettsiae have exploited divergent strategies to accomplish such challenging tasks and these elaborated strategies focus on distinct host cell processes. In the present review, we summarized current understandings of how different rickettsial species employ their effectors' arsenal to affect host cellular processes in order to promote their own replication or to avoid destruction.
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Affiliation(s)
- Dan Huang
- Department of Respiratory Medicine, Center of Pathogen Biology and Infectious Disease, Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China
| | - Jingjing Luo
- Department of Respiratory Medicine, Center of Pathogen Biology and Infectious Disease, Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China
| | - Xuan OuYang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Lei Song
- Department of Respiratory Medicine, Center of Pathogen Biology and Infectious Disease, Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China
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Dahmani M, Cook JH, Zhu JC, Riley SP. Contribution of classical complement activation and IgM to the control of Rickettsia infection. Mol Microbiol 2021; 116:1476-1488. [PMID: 34725868 PMCID: PMC8955150 DOI: 10.1111/mmi.14839] [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: 10/05/2021] [Revised: 10/28/2021] [Accepted: 10/29/2021] [Indexed: 01/02/2023]
Abstract
Pathogenic Rickettsia are obligate intracellular bacteria and the etiologic agents of many life‐threatening infectious diseases. Due to the serious nature of these infections, it is imperative to both identify the responsive immune sensory pathways and understand the associated immune mechanisms that restrict Rickettsia proliferation. Previous studies have demonstrated that the mammalian complement system is both activated during Rickettsia infection and contributes to the immune response to infection. To further define this component of the mammalian anti‐Rickettsia immune response, we sought to identify the mechanism(s) of complement activation during Rickettsia infection. We have employed a series of in vitro and in vivo models of infection to investigate the role of the classical complement activation pathway during Rickettsia infection. Depletion or elimination of complement activity demonstrates that both C1q and pre‐existing IgM contribute to complement activation; thus implicating the classical complement system in Rickettsia‐mediated complement activation. Elimination of the classical complement pathway from mice increases susceptibility to R. australis infection with both increased bacterial loads in multiple tissues and decreased immune activation markers. This study highlights the role of the classical complement pathway in immunity against Rickettsia and implicates resident Rickettsia‐responsive IgM in the response to infection.
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Affiliation(s)
- Mustapha Dahmani
- Department of Veterinary Medicine, University of Maryland-College Park, College Park, Maryland, USA.,Virginia-Maryland College of Veterinary Medicine, College Park, Maryland, USA
| | - Jack H Cook
- Department of Veterinary Medicine, University of Maryland-College Park, College Park, Maryland, USA.,Virginia-Maryland College of Veterinary Medicine, College Park, Maryland, USA
| | - Jinyi C Zhu
- Department of Veterinary Medicine, University of Maryland-College Park, College Park, Maryland, USA.,Virginia-Maryland College of Veterinary Medicine, College Park, Maryland, USA
| | - Sean P Riley
- Department of Veterinary Medicine, University of Maryland-College Park, College Park, Maryland, USA.,Virginia-Maryland College of Veterinary Medicine, College Park, Maryland, USA
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Vaccine Design and Vaccination Strategies against Rickettsiae. Vaccines (Basel) 2021; 9:vaccines9080896. [PMID: 34452021 PMCID: PMC8402588 DOI: 10.3390/vaccines9080896] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 08/10/2021] [Accepted: 08/11/2021] [Indexed: 12/30/2022] Open
Abstract
Rickettsioses are febrile, potentially lethal infectious diseases that are a serious health threat, especially in poor income countries. The causative agents are small obligate intracellular bacteria, rickettsiae. Rickettsial infections are emerging worldwide with increasing incidence and geographic distribution. Nonetheless, these infections are clearly underdiagnosed because methods of diagnosis are still limited and often not available. Another problem is that the bacteria respond to only a few antibiotics, so delayed or wrong antibiotic treatment often leads to a more severe outcome of the disease. In addition to that, the development of antibiotic resistance is a serious threat because alternative antibiotics are missing. For these reasons, prophylactic vaccines against rickettsiae are urgently needed. In the past years, knowledge about protective immunity against rickettsiae and immunogenic determinants has been increasing and provides a basis for vaccine development against these bacterial pathogens. This review provides an overview of experimental vaccination approaches against rickettsial infections and perspectives on vaccination strategies.
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Abstract
Over the last decades, rickettsioses are emerging worldwide. These diseases are caused by intracellular bacteria. Although rickettsioses can be treated with antibiotics, a vaccine against rickettsiae is highly desired for several reasons. Rickettsioses are highly prevalent, especially in poor countries, and there are indications of the development of antibiotic resistance. In addition, some rickettsiae can persist and cause recurrent disease. The development of a vaccine requires the understanding of the immune mechanisms that are involved in protection as well as in immunopathology. Knowledge about these immune responses is accumulating, and efforts have been undertaken to identify antigenic components of rickettsiae that may be useful as a vaccine. This review provides an overview on current knowledge of adaptive immunity against rickettsiae, which is essential for defense, rickettsial antigens that have been identified so far, and on vaccination strategies that have been used in animal models of rickettsial infections.
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Immunity against the Obligate Intracellular Bacterial Pathogen Rickettsia australis Requires a Functional Complement System. Infect Immun 2018; 86:IAI.00139-18. [PMID: 29581196 PMCID: PMC5964522 DOI: 10.1128/iai.00139-18] [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: 02/21/2018] [Accepted: 03/21/2018] [Indexed: 11/23/2022] Open
Abstract
The complement system has a well-defined role in deterring blood-borne infections. However, complement is not entirely efficacious, as several bacterial pathogens, including some obligate intracellular pathogens, have evolved mechanisms for resistance. It is presumed that obligate intracellular bacteria evade complement attack by residing within a host cell; however, recent studies have challenged this presumption. Here, we demonstrate that the complement system is activated during infection with the obligate intracellular bacterium Rickettsia australis and that genetic ablation of complement increases susceptibility to infection. Interaction of Rickettsia australis with serum-borne complement leads to activation of the complement cascade, producing three effector mechanisms that could negatively influence R. australis. The C9-dependent membrane attack complex can lead to deposition of a bacteriolytic membrane pore on the bacteria, but this system does not contribute to control of rickettsial infection. Similarly, complement receptor (CR1/2)-dependent opsonophagocytosis may lead to engulfment and killing of the bacteria, but this system is also dispensable for immunity. Nevertheless, intact complement is essential for naturally acquired and antibody-mediated immunity to Rickettsia infection. Comparison of infection in mice lacking the central complement protein C3 with infection in their wild-type counterparts demonstrated decreases in gamma interferon (IFN-γ) production, IgG secretion, and spleen hyperplasia in animals lacking complement. The correlation between loss of secondary immune functions and loss of complement indicates that the proinflammatory signaling components of the complement system, and not membrane attack complex or opsonophagocytosis, contribute to the immune response to this pathogen.
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Garza DA, Riley SP, Martinez JJ. Expression of Rickettsia Adr2 protein in E. coli is sufficient to promote resistance to complement-mediated killing, but not adherence to mammalian cells. PLoS One 2017; 12:e0179544. [PMID: 28662039 PMCID: PMC5491016 DOI: 10.1371/journal.pone.0179544] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 05/31/2017] [Indexed: 01/20/2023] Open
Abstract
Bacteria exposed to host serum are subject to the antibacterial effects to the complement system. However, pathogenic microorganisms have evolved mechanisms of evading this immune attack. We have previously demonstrated that at least two R. conorii antigens, RC1281/Adr1 and OmpB β-peptide, contribute to the evasion of complement-mediated killing by binding the complement regulatory proteins vitronectin and factor H. RC1282/Adr2, a protein related to Adr1, is predicted to share similar structural features, suggesting that this protein may also contribute to evasion of complement-mediated killing. Interestingly, the R. prowazekii Adr1 and Adr2(RP828) proteins were originally found to interact with host cell surface proteins, suggesting their putative roles as adhesins in this pathogenic rickettsial species. In this study, we expressed both R. conorii and R. prowazekii Adr2 on the surface of a non-adherent, serum-sensitive strain of E. coli to examine the potential role of this protein to mediate evasion of complement-mediated killing and adherence to host cells. We demonstrate that, similar to R. conorii Adr1, R. conorii and R. prowazekii Adr2 are sufficient to mediate serum resistance and to promote interaction with the host complement regulator vitronectin. Furthermore, we demonstrate that expression of Adr2 in a non-adherent strain of E. coli is insufficient to mediate adherence to cultured mammalian endothelial cells. Together, our data demonstrate that the R. conorii and R. prowazekii Adr2 protein does not participate in the interactions with mammalian cells, but rather, participates in the evasion of killing by complement.
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Affiliation(s)
- Daniel A. Garza
- Vector-Borne Diseases Laboratories, Department of Pathobiological Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, United States of America
| | - Sean P. Riley
- Vector-Borne Diseases Laboratories, Department of Pathobiological Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, United States of America
| | - Juan J. Martinez
- Vector-Borne Diseases Laboratories, Department of Pathobiological Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, United States of America
- * E-mail:
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