The adaptor protein CARD9 is essential for the activation of myeloid cells through ITAM-associated and Toll-like receptors

ABSTRACT Gingival fibroblasts produce proinflammatory cytokines in response to lipopolysaccharide (LPS) from periodontopathic bacteria. Recently it has become evident that the human homologue of DrosophilaToll can transduce intracellular signaling by LPS stimulation. Toll-like receptors (TLRs) have been identified in myeloid cells; however, their role in nonmyeloid cells such as gingival fibroblasts has not been fully elucidated. Here, we report that human gingival fibroblasts constitutively express TLR2 and TLR4 and that their levels of expression are increased by stimulation with LPS fromPorphyromonas gingivalis. Upregulated expression of interleukin-6 gene and protein in fibroblasts stimulated with LPS is inhibited by anti-TLR4 antibody. These findings suggest that TLRs may confer responsiveness to LPS in gingival fibroblasts.

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Toll-Like Receptor 3 Signaling via TRIF Contributes to a Protective Innate Immune Response to Severe Acute Respiratory Syndrome Coronavirus Infection

mBio ◽

10.1128/mbio.00638-15 ◽

2015 ◽

Vol 6 (3) ◽

Cited By ~ 143

Author(s):

Allison L. Totura ◽

Alan Whitmore ◽

Sudhakar Agnihothram ◽

Alexandra Schäfer ◽

Michael G. Katze ◽

...

Keyword(s):

Immune Response ◽

Weight Loss ◽

Severe Acute Respiratory Syndrome ◽

Innate Immune Response ◽

Adaptor Protein ◽

Innate Immune ◽

Lung Pathology ◽

Toll Like Receptors ◽

Tlr Signaling ◽

Highly Pathogenic

ABSTRACT Toll-like receptors (TLRs) are sensors that recognize molecular patterns from viruses, bacteria, and fungi to initiate innate immune responses to invading pathogens. The emergence of highly pathogenic coronaviruses severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) is a concern for global public health, as there is a lack of efficacious vaccine platforms and antiviral therapeutic strategies. Previously, it was shown that MyD88, an adaptor protein necessary for signaling by multiple TLRs, is a required component of the innate immune response to mouse-adapted SARS-CoV infection in vivo. Here, we demonstrate that TLR3−/−, TLR4−/−, and TRAM−/− mice are more susceptible to SARS-CoV than wild-type mice but experience only transient weight loss with no mortality in response to infection. In contrast, mice deficient in the TLR3/TLR4 adaptor TRIF are highly susceptible to SARS-CoV infection, showing increased weight loss, mortality, reduced lung function, increased lung pathology, and higher viral titers. Distinct alterations in inflammation were present in TRIF−/− mice infected with SARS-CoV, including excess infiltration of neutrophils and inflammatory cell types that correlate with increased pathology of other known causes of acute respiratory distress syndrome (ARDS), including influenza virus infections. Aberrant proinflammatory cytokine, chemokine, and interferon-stimulated gene (ISG) signaling programs were also noted following infection of TRIF−/− mice that were similar to those seen in human patients with poor disease outcome following SARS-CoV or MERS-CoV infection. These findings highlight the importance of TLR adaptor signaling in generating a balanced protective innate immune response to highly pathogenic coronavirus infections. IMPORTANCE Toll-like receptors are a family of sensor proteins that enable the immune system to differentiate between “self” and “non-self.” Agonists and antagonists of TLRs have been proposed to have utility as vaccine adjuvants or antiviral compounds. In the last 15 years, the emergence of highly pathogenic coronaviruses SARS-CoV and MERS-CoV has caused significant disease accompanied by high mortality rates in human populations, but no approved therapeutic treatments or vaccines currently exist. Here, we demonstrate that TLR signaling through the TRIF adaptor protein protects mice from lethal SARS-CoV disease. Our findings indicate that a balanced immune response operating through both TRIF-driven and MyD88-driven pathways likely provides the most effective host cell intrinsic antiviral defense responses to severe SARS-CoV disease, while removal of either branch of TLR signaling causes lethal SARS-CoV disease in our mouse model. These data should inform the design and use of TLR agonists and antagonists in coronavirus-specific vaccine and antiviral strategies.

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Vpx enhances innate immune responses independently of SAMHD1 during HIV-1 infection

Retrovirology ◽

10.1186/s12977-021-00548-2 ◽

2021 ◽

Vol 18 (1) ◽

Author(s):

Oya Cingöz ◽

Nicolas D. Arnow ◽

Mireia Puig Torrents ◽

Norbert Bannert

Keyword(s):

Immune Responses ◽

Cell Lines ◽

Myeloid Cells ◽

Adaptor Protein ◽

Myeloid Cell ◽

Innate Immune ◽

Innate Immune Responses ◽

Accessory Gene ◽

Monocytic Cell ◽

Hiv 1

Abstract Background The genomes of HIV-2 and some SIV strains contain the accessory gene vpx, which carries out several functions during infection, including the downregulation of SAMHD1. Vpx is also commonly used in experiments to increase HIV-1 infection efficiency in myeloid cells, particularly in studies that investigate the activation of antiviral pathways. However, the potential effects of Vpx on cellular innate immune signaling is not completely understood. We investigated whether and how Vpx affects ISG responses in monocytic cell lines and MDMs during HIV-1 infection. Results HIV-1 infection at excessively high virus doses can induce ISG activation, although at the expense of high levels of cell death. At equal infection levels, the ISG response is potentiated by the presence of Vpx and requires the initiation of reverse transcription. The interaction of Vpx with the DCAF1 adaptor protein is important for the enhanced response, implicating Vpx-mediated degradation of a host factor. Cells lacking SAMHD1 show similarly augmented responses, suggesting an effect that is independent of SAMHD1 degradation. Overcoming SAMHD1 restriction in MDMs to reach equal infection levels with viruses containing and lacking Vpx reveals a novel function of Vpx in elevating innate immune responses. Conclusions Vpx likely has as yet undefined roles in infected cells. Our results demonstrate that Vpx enhances ISG responses in myeloid cell lines and primary cells independently of its ability to degrade SAMHD1. These findings have implications for innate immunity studies in myeloid cells that use Vpx delivery with HIV-1 infection.

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Critical coordination of innate immune defense against Toxoplasma gondii by dendritic cells responding via their Toll-like receptors

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1011549108 ◽

2010 ◽

Vol 108 (1) ◽

pp. 278-283 ◽

Cited By ~ 74

Author(s):

Baidong Hou ◽

Alicia Benson ◽

Lili Kuzmich ◽

Anthony L. DeFranco ◽

Felix Yarovinsky

Keyword(s):

Dendritic Cells ◽

Toxoplasma Gondii ◽

Host Defense ◽

Adaptor Protein ◽

T Cell Response ◽

Immune Defense ◽

Innate Immune ◽

Microbial Pathogens ◽

Toll Like Receptors ◽

Inflammatory Monocytes

Toll-like receptors (TLRs) play an important role in host defense against a variety of microbial pathogens. We addressed the mechanism by which TLRs contribute to host defense against the lethal parasite Toxoplasma gondii by using mice with targeted inactivation of the TLR adaptor protein myeloid differentiation primary response gene 88 (MyD88) in different innate cell types. Lack of MyD88 in dendritic cells (DCs), but not in macrophages or neutrophils, resulted in high susceptibility to the T. gondii infection. In the mice deficient in MyD88 in DCs, the early IL-12 response by DCs was ablated, the IFN-γ response by natural killer cells was delayed, and the recruited inflammatory monocytes were incapable of killing the T. gondii parasites. The T-cell response, although attenuated in these mice, was sufficient to eradicate the parasite during the chronic stage, provided that defects in DC activation were compensated by IL-12 treatment early after infection. These results demonstrate a central role of DCs in orchestrating the innate immune response to an intracellular pathogen and establish that defects in pathogen recognition by DCs can predetermine sensitivity to infection.

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The impact of cell maturation and tissue microenvironments on the expression of endosomal Toll-like receptors in monocytes and macrophages

International Immunology ◽

10.1093/intimm/dxaa055 ◽

2020 ◽

Vol 32 (12) ◽

pp. 785-798

Author(s):

Ryota Sato ◽

Tatjana Reuter ◽

Ryosuke Hiranuma ◽

Takuma Shibata ◽

Ryutaro Fukui ◽

...

Keyword(s):

Protein Expression ◽

Kupffer Cells ◽

Myeloid Cells ◽

Myeloid Cell ◽

Toll Like Receptors ◽

Mhc Ii ◽

Monocytes And Macrophages ◽

Differentiation Status ◽

The Impact ◽

Patrolling Monocytes

Abstract Toll-like receptors (TLRs) impact myeloid cell responsiveness to environmental cues such as pathogen components and metabolites. Although TLR protein expression in monocytes and tissue macrophages is thought to be optimized for microenvironments in each tissue, a comprehensive study has not been reported. We here examined protein expression of endogenous TLRs in tissue-resident myeloid cells. Neutrophils in peripheral blood, spleen, liver and lung expressed TLR2, TLR4 and TLR5 in all tissues. Ly6C+ MHC II‒ classical monocytes mature into Ly6C‒ MHC II+ monocyte-derived dendritic cells (moDCs) or Ly6C‒ MHC II‒ patrolling monocytes. These subsets were found in all the tissues studied. TLR2 and TLR4 were displayed on all of these subsets, regardless of location. In contrast, expression of endosomal TLRs did vary with tissues and subsets. moDCs expressed TLR9, but much less TLR7. In contrast, TLR7, not TLR3 or TLR9, was highly expressed in classical and patrolling monocytes. Tissue macrophages such as red pulp macrophages in the spleen, Kupffer cells in the liver, microglia in the brain, alveolar macrophages in the lung and adipose tissue macrophages all expressed TLR2, TLR4 and TLR3. TLR7 was also expressed in these tissue macrophages except Kupffer cells in the liver. TLR9 expression in tissue macrophages was much lower or hard to detect. These results suggest that expression of endosomal TLRs in myeloid cells is influenced by their differentiation status and tissue-specific microenvironments.

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Myxoma Virus Lacking the Pyrin-Like Protein M013 Is Sensed in Human Myeloid Cells by both NLRP3 and Multiple Toll-Like Receptors, Which Independently Activate the Inflammasome and NF- B Innate Response Pathways

Journal of Virology ◽

10.1128/jvi.00410-11 ◽

2011 ◽

Vol 85 (23) ◽

pp. 12505-12517 ◽

Cited By ~ 36

Author(s):

M. M. Rahman ◽

G. McFadden

Keyword(s):

Myeloid Cells ◽

Myxoma Virus ◽

Toll Like Receptors ◽

Innate Response

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