To generate a new murine model for virus, DC-SIGN gene in murine was humanized. In this study, we successfully generated a humanized C57BL/6N mouse model expressing human DC-SIGN (hDC-SIGN) using ...CRISPR/Cas9 technology, and evaluated its characters and susceptibility to virus. The humanized mice could survival as usual, and with normal physiological index just like the wild-type mice. Whereas, we found significant differences in the intestinal flora and metabolic profiles between wild-type mice and humanized mice. Following intranasal infection with SARS-CoV-2, hDC-SIGN mice exhibited significantly increased viral loads in the lungs and nasal turbinates, along with more severe lung damage. This phenomenon may be associated with differential lipid metabolism and Fcγ receptor-mediated phagocytosis in two mouse models. This study provides a useful tool for investigating the mechanisms of coronavirus infection and potential drug therapies against novel coronavirus.
Despite mounting evidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) engagement with immune cells, most express little, if any, of the canonical receptor of SARS-CoV-2, ...angiotensin-converting enzyme 2 (ACE2). Here, using a myeloid cell receptor-focused ectopic expression screen, we identified several C-type lectins (DC-SIGN, L-SIGN, LSECtin, ASGR1, and CLEC10A) and Tweety family member 2 (TTYH2) as glycan-dependent binding partners of the SARS-CoV-2 spike. Except for TTYH2, these molecules primarily interacted with spike via regions outside of the receptor-binding domain. Single-cell RNA sequencing analysis of pulmonary cells from individuals with coronavirus disease 2019 (COVID-19) indicated predominant expression of these molecules on myeloid cells. Although these receptors do not support active replication of SARS-CoV-2, their engagement with the virus induced robust proinflammatory responses in myeloid cells that correlated with COVID-19 severity. We also generated a bispecific anti-spike nanobody that not only blocked ACE2-mediated infection but also the myeloid receptor-mediated proinflammatory responses. Our findings suggest that SARS-CoV-2-myeloid receptor interactions promote immune hyperactivation, which represents potential targets for COVID-19 therapy.
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•C-type lectins and TTYH2 are myeloid cell-interacting partners of SARS-CoV-2 spike•C-type lectins interact with spike largely through regions outside of the RBD•Myeloid receptors promote SARS-CoV-2 proinflammatory responses but not infection•A bispecific nanobody blocked SARS-CoV-2 infection and inflammatory responses
Most immune cells express little, if any, of the canonical SARS-CoV-2 receptor, ACE2. Lu et al. report that C-type lectins and TTYH2 act as SARS-CoV-2 myeloid cell-interacting partners that trigger immune hyperactivation but not infection. These findings raise the possibility that these virus-myeloid cell interactions are directly involved in COVID-19 immunopathogenesis and could be targeted for COVID-19 therapy.
The Front Cover shows a blueprint for the design of a multivalent ligand of the C‐type lectin receptor DC‐SIGN. The compound features a tetravalent rigid scaffold that enables for the multivalent ...presentation of glycomimetics in a spatially defined fashion. This molecular architecture achieves strong binding avidity towards DC‐SIGN and increased selectivity over the C‐type lectin langerin, which is characterized by a distinct spatial arrangement of the carbohydrate recognition domains. Cover design by Mr. Francesco Frullini. More information can be found in the Research Article by F. Fieschi, A. Bernardi et al.
The reinvigoration of anti-tumor T cells in response to immune checkpoint blockade (ICB) therapy is well established. Whether and how ICB therapy manipulates antibody-mediated immune response in ...cancer environments, however, remains elusive. Using tandem mass spectrometric analysis of modification of immunoglobulin G (IgG) from hepatoma tissues, we identified a role of ICB therapy in catalyzing IgG sialylation in the Fc region. Effector T cells triggered sialylation of IgG via an interferon (IFN)-γ-ST6Gal-I-dependent pathway. DC-SIGN+ macrophages represented the main target cells of sialylated IgG. Upon interacting with sialylated IgG, DC-SIGN stimulated Raf-1-elicited elevation of ATF3, which inactivated cGAS-STING pathway and eliminated subsequent type-I-IFN-triggered antitumorigenic immunity. Although enhanced IgG sialylation in tumors predicted improved therapeutic outcomes for patients receiving ICB therapy, impeding IgG sialylation augmented antitumorigenic T cell immunity after ICB therapy. Thus, targeting antibody-based negative feedback action of ICB therapy has potential for improving efficacy of cancer immunotherapies.
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•ICB therapy catalyzes IgG sialylation in HCC that predicts an improved outcome•Effector T cells trigger sialylated IgG via IFN-γ-ST6Gal-I-dependent pathways•Sialylated IgG binding to DC-SIGN abrogates macrophage type I IFN production•Impeding IgG sialylation enhances antitumorigenic T cell immunity during ICB therapy
Although immune checkpoint blockade (ICB) influence on T cells is well known, its impact on antibodies is less understood. Wu et al. show how ICB-elicited sialylation of IgG suppresses DC-SIGN-expressing macrophages in human hepatocellular carcinoma. Impeding IgG sialylation augments macrophage IFN-I responses and antitumorigenic T cell immunity during immunotherapy.
This paper reviews the past ten years of our research in the field of glycomimetics synthesis and design. The structure‐based design of mono‐ and polyvalent lectin ligands is one of the three main ...areas that we have explored in this period. We summarize here our work on ligands targeted against the dendritic cell receptor DC‐SIGN. A second direction we have followed involves the discovery of lectin antagonists by screening of glycomimetic libraries. This approach has led to interesting hits against cholera toxin and related bacterial enterotoxins, as well as, in a different campaign, against the human C‐type lectin dectin‐2. Underlying both approaches, the development of robust synthetic methodologies for the rapid and selective synthesis of unnatural glycoconjugates has been our attempt to contribute to the diversification and enrichment of the chemical toolbox of glycoscience.
With the aim of interfering with the information (sugar code) exchanged between glycans and their protein receptors, we have been developing carbohydrate mimics (glycomimetics) which are more efficient and more selective than naturally occurring saccharides. Here we outline our efforts over the past decade.
Human milk oligosaccharides (HMOS) are a complex mixture of bioactive components supporting the immune development of breastfed‐infants. Dendritic cells (DCs) play a central role in the regulation of ...immune responses, being specialized in antigen presentation and driving T‐cell priming as well as differentiation. However, little is known about the direct effects of HMOS on human DC phenotypes and functions. Here, we report that HMOS mixture isolated from pooled human milk, induced semi‐maturation of human monocytes‐derived DCs (moDCs), and elevated levels of IL‐10, IL‐27 and IL‐6 but not IL‐12p70 and TNF‐α. Consistently, HMOS‐conditioned human moDCs promoted Treg generation from naïve CD4+ T cells. Interestingly, HMOS limited LPS‐induced maturation of human moDCs, while maintained IL‐10 and IL‐27 secretion and reduced LPS‐induced production of IL‐12p70, IL‐6 and TNF‐α. Furthermore, HMOS+LPS‐stimulated DCs induced a higher frequency of Tregs and increased IL‐10 production, while a reduction in Tbet+Th1 frequency and IFN‐γ production was detected as compared to LPS‐DCs. The regulatory effects of HMOS seemed to be mediated by interactions of HMOS with receptors, including but not limited to TLR4 and DC‐SIGN on human moDCs. In conclusion, HMOS contain tolerogenic factors influencing human moDCs and thereby modulating the development of the neonatal immune system.
Breastfeeding is essential in programming immune development. Human milk oligosaccharides (HMOS) isolated from human milk, equip moDCs with a regulatory phenotype and function, subsequently inducing Tregs. LPS‐ induced moDCs maturation is attenuated by HMOS, reducing pro‐inflammatory while maintaining regulatory responses. HMOS seem to regulate early life immunity through DCs.
Summary
Background
Worldwide, dengue is the most prevalent human arbovirus disease. Dengue infection may cause a range of clinical manifestations from self‐limiting febrile illness through to a ...life‐threatening syndrome accompanied by both bleeding and shock. Thrombocytopenia is frequently observed in mild and severe disease; however, the mechanisms involved in DENV‐induced platelet activation and thrombocytopenia are incompletely understood.
Patients and methods
Freshly isolated platelets from patients with dengue were evaluated for markers of activation, mitochondrial alteration and activation of cell death pathways. In parallel, we examined direct DENV‐induced activation and apoptosis of platelets obtained from healthy subjects.
Results
We found that platelets from DENV‐infected patients exhibited increased activation by comparison to control subjects. Moreover, platelets from DENV‐infected patients exhibited classic signs of the intrinsic pathway of apoptosis that include increased surface phosphatidylserine exposure, mitochondrial depolarization and activation of caspase‐9 and ‐3. Indeed, thrombocytopenia was shown to strongly associate with enhanced platelet activation and cell death in DENV‐infected patients. Platelet activation, mitochondrial dysfunction and caspase‐dependent phosphatidylserine exposure on platelets were also observed when platelets from healthy subjects were directly exposed to DENV in vitro. DENV‐induced platelet activation was shown to occur through mechanisms largely dependent on DC‐SIGN.
Conclusions
Together our results demonstrate that platelets from patients with dengue present signs of activation, mitochondrial dysfunction and activation of the apoptosis caspase cascade, which may contribute to the development of thrombocytopenia in patients with dengue. Our results also suggest the involvement of DC‐SIGN as a critical receptor in DENV‐dependent platelet activation.
Abstract
Glycans are carbohydrate modifications typically found on proteins or lipids, and can act as ligands for glycan-binding proteins called lectins. Glycans and lectins play crucial roles in the ...function of cells and organs, and in the immune system of animals and humans. Viral pathogens use glycans and lectins that are encoded by their own or the host genome for their replication and spread. Recent advances in glycobiological research indicate that glycans and lectins mediate key interactions at the virus-host interface, controlling viral spread and/or activation of the immune system. This review reflects on glycan–lectin interactions in the context of viral infection and antiviral immunity. A short introduction illustrates the nature of glycans and lectins, and conveys the basic principles of their interactions. Subsequently, examples are discussed highlighting specific glycan–lectin interactions and how they affect the progress of viral infections, either benefiting the host or the virus. Moreover, glycan and lectin variability and their potential biological consequences are discussed. Finally, the review outlines how recent advances in the glycan–lectin field might be transformed into promising new approaches to antiviral therapy.
Glycans and lectins cover crucial roles in virus biology and their interplay often shapes the virus-host interaction. This review reflects on glycan-lectin interactions in the context of viral infection and anti-viral immunity, and explores potential targets for antiviral strategies.
The Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is related with the COVID-19 pandemic. Recent spike protein variations have had an effect on the transmission of the virus. In ...addition to ACE-2, spike proteins can employ DC-SIGN and its analogous receptor, DC-SIGNR, for host evasion. Spike variations in the DC-SIGN interaction region and role of DC-SIGN in immune evasion have not been well defined. To understand the spike protein variations and their binding mode, phylogenetic analysis of the complete GISAID (Global Initiative for Sharing Avian Influenza Data) data of the SARS-CoV-2 spike protein was considered. In addition, an in silico knockout network evaluation of the SARS-CoV-2 single-cell transcriptome was conducted to determine the key role of DC-SIGN/R in immunological dysregulation. Within the DC-SIGN-interacting region of the SARS-CoV spike protein, the spike protein of SARS-CoV-2 displayed remarkable similarity to the SARS-CoV spike protein. Surprisingly, the phylogenetic analysis revealed that the SARS-CoV-2’s spike exhibited significantly diverse variants in the DC-SIGN interaction domain, which altered the frequency of these variants. The variation within the DC-SIGN-interacting domain of spike proteins affected the binding of a limited number of variants with DC-SIGN and DC-SIGNR and affected their evolution. MMGBSA binding free energies evaluation differed for variants from those of the wild type, suggesting the influence of substitution mutations on the interaction pattern. In silico knockout network analysis of the single-cell transcriptome of Bronchoalveolar Lavage and peripheral blood mononuclear cells revealed that SARS-CoV-2 altered DC-SIGN/R signaling. Early surveillance of diverse SARS-CoV-2 strains could preclude a worsening of the pandemic and facilitate the development of an optimum vaccine against variations. The spike Receptor Binding Domain genetic variants are thought to boost SARS CoV-2 immune evasion, resulting in its higher longevity.
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