Enterococcus faecalis Capsular Polysaccharide Serotypes C and D and Their Contributions to Host Innate Immune Evasion

ABSTRACT It has become increasingly difficult to treat infections caused by Enterococcus faecalis due to its high levels of intrinsic and acquired antibiotic resistance. However, few studies have explored the mechanisms that E. faecalis employs to circumvent the host innate immune response and establish infection. Capsular polysaccharides are important virulence factors that are associated with innate immune evasion. We demonstrate, using cultured macrophages (RAW 264.7), that capsule-producing E. faecalis strains of either serotype C or D are more resistant to complement-mediated opsonophagocytosis than unencapsulated strains. We show that differences in opsonophagocytosis are not due to variations in C3 deposition but are due to the ability of capsule to mask bound C3 from detection on the surface of E. faecalis. Similarly, E. faecalis capsule masks lipoteichoic acid from detection, which correlates with decreased tumor necrosis factor alpha production by cultured macrophages in the presence of encapsulated strains compared to that in the presence of unencapsulated strains. Our studies confirm the important role of the capsule as a virulence factor of E. faecalis and provide several mechanisms by which the presence of the capsule influences evasion of the innate immune response and suggest that the capsule could be a potential target for developing alternative therapies to treat E. faecalis infections.

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Vaccinia virus immune evasion: mechanisms, virulence and immunogenicity

Journal of General Virology ◽

10.1099/vir.0.055921-0 ◽

2013 ◽

Vol 94 (11) ◽

pp. 2367-2392 ◽

Cited By ~ 185

Author(s):

Geoffrey L. Smith ◽

Camilla T. O. Benfield ◽

Carlos Maluquer de Motes ◽

Michela Mazzon ◽

Stuart W. J. Ember ◽

...

Keyword(s):

Immune Response ◽

Vaccinia Virus ◽

Innate Immune Response ◽

Immune Evasion ◽

Mammalian Cells ◽

Innate Immune ◽

Gene Encoding ◽

Cytokines And Chemokines ◽

Host Innate Immune Response ◽

New Hosts

Virus infection of mammalian cells is sensed by pattern recognition receptors and leads to an innate immune response that restricts virus replication and induces adaptive immunity. In response, viruses have evolved many countermeasures that enable them to replicate and be transmitted to new hosts, despite the host innate immune response. Poxviruses, such as vaccinia virus (VACV), have large DNA genomes and encode many proteins that are dedicated to host immune evasion. Some of these proteins are secreted from the infected cell, where they bind and neutralize complement factors, interferons, cytokines and chemokines. Other VACV proteins function inside cells to inhibit apoptosis or signalling pathways that lead to the production of interferons and pro-inflammatory cytokines and chemokines. In this review, these VACV immunomodulatory proteins are described and the potential to create more immunogenic VACV strains by manipulation of the gene encoding these proteins is discussed.

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Bacterial lipids: powerful modifiers of the innate immune response

F1000Research ◽

10.12688/f1000research.11388.1 ◽

2017 ◽

Vol 6 ◽

pp. 1334 ◽

Cited By ~ 32

Author(s):

Courtney E. Chandler ◽

Robert K. Ernst

Keyword(s):

Immune Response ◽

Immune System ◽

Innate Immune Response ◽

Lipoteichoic Acid ◽

Innate Immune ◽

Microbial Pathogens ◽

Host Immune System ◽

Receptor Proteins ◽

Bacterial Membranes ◽

Host Innate Immune Response

The innate immune system serves as a first line of defense against microbial pathogens. The host innate immune response can be triggered by recognition of conserved non-self-microbial signature molecules by specific host receptor proteins called Toll-like receptors. For bacteria, many of these molecular triggers reside on or are embedded in the bacterial membrane, the interface exposed to the host environment. Lipids are the most abundant component of membranes, and bacteria possess a unique set of lipids that can initiate or modify the host innate immune response. Bacterial lipoproteins, peptidoglycan, and outer membrane molecules lipoteichoic acid and lipopolysaccharide are key modulators of the host immune system. This review article will highlight some of the research emerging at the crossroads of bacterial membranes and innate immunity.

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Host Innate Immune Response and Viral Immune Evasion During Alphaherpesvirus Infection

Current Issues in Molecular Biology ◽

10.21775/cimb.042.635 ◽

2022 ◽

pp. 635-686

Author(s):

Krystal K. Lum ◽

Ileana M. Cristea

Keyword(s):

Immune Response ◽

Innate Immune Response ◽

Immune Evasion ◽

Innate Immune ◽

Viral Immune Evasion ◽

Host Innate Immune Response

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Viral Infection: An Evolving Insight into the Signal Transduction Pathways Responsible for the Innate Immune Response

Advances in Virology ◽

10.1155/2012/131457 ◽

2012 ◽

Vol 2012 ◽

pp. 1-11 ◽

Cited By ~ 5

Author(s):

Girish J. Kotwal ◽

Steven Hatch ◽

William L. Marshall

Keyword(s):

Signal Transduction ◽

Immune Response ◽

Innate Immunity ◽

Viral Infection ◽

Innate Immune Response ◽

Immune Evasion ◽

Viral Infections ◽

Innate Immune ◽

Innate Immune Evasion ◽

Insight Into

The innate immune response is initiated by the interaction of stereotypical pathogen components with genetically conserved receptors for extracytosolic pathogen-associated molecular patterns (PAMPs) or intracytosolic nucleic acids. In multicellular organisms, this interaction typically clusters signal transduction molecules and leads to their activations, thereby initiating signals that activate innate immune effector mechanisms to protect the host. In some cases programmed cell death—a fundamental form of innate immunity—is initiated in response to genotoxic or biochemical stress that is associated with viral infection. In this paper we will summarize innate immune mechanisms that are relevant to viral pathogenesis and outline the continuing evolution of viral mechanisms that suppress the innate immunity in mammalian hosts. These mechanisms of viral innate immune evasion provide significant insight into the pathways of the antiviral innate immune response of many organisms. Examples of relevant mammalian innate immune defenses host defenses include signaling to interferon and cytokine response pathways as well as signaling to the inflammasome. Understanding which viral innate immune evasion mechanisms are linked to pathogenesis may translate into therapies and vaccines that are truly effective in eliminating the morbidity and mortality associated with viral infections in individuals.

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