Hemocyanins are used as immunomodulators in clinical applications because they induce a strong Th1‐biased cell‐mediated immunity, which has beneficial effects. They are multiligand glycosylated ...molecules with abundant and complex mannose‐rich structures. It remains unclear whether these structures influence hemocyanin‐induced immunostimulatory processes in human APCs. We have previously shown that hemocyanin glycans from Concholepas concholepas (CCH), Fissurella latimarginata (FLH), and Megathura crenulata (KLH), participate in their immune recognition and immunogenicity in mice, interacting with murine C‐type lectin receptors (CLRs). Here, we studied the interactions of these hemocyanins with two major mannose‐binding CLRs on monocyte‐derived human DCs: MR (mannose receptor) and DC‐SIGN (DC‐specific ICAM‐3–grabbing nonintegrin). Diverse analyses showed that hemocyanins are internalized by a mannose‐sensitive mechanism. This process was calcium dependent. Moreover, hemocyanins colocalized with MR and DC‐SIGN, and were partly internalized through clathrin‐mediated endocytosis. The hemocyanin‐mediated proinflammatory cytokine response was impaired when using deglycosylated FLH and KLH compared to CCH. We further showed that hemocyanins bind to human MR and DC‐SIGN in a carbohydrate‐dependent manner with affinity constants in the physiological concentration range. Overall, we showed that these three clinically valuable hemocyanins interact with human mannose‐sensitive CLRs, initiating an immune response and promoting a Th1 cell‐driving potential.
Mollusk hemocyanin bind with high affinity constants to human MR and DC‐SIGN leading to their endocytosis. The CLR‐mediated endocytosis is occurring in human monocyte derived cells and is dependent on hemocyanin glycosylation. This process leads to proinflammatory cytokine secretion by DCs, explaining partially their immunomodulator effect.
Zika virus (ZIKV) is an emerging mosquito-borne flavivirus. Recent ZIKV outbreaks have produced serious human disease, including neurodevelopmental malformations (congenital Zika syndrome) and ...Guillain-Barré syndrome. These outcomes were not associated with ZIKV infection prior to 2013, raising the possibility that viral genetic changes could contribute to new clinical manifestations. All contemporary ZIKV isolates encode an N-linked glycosylation site in the envelope (E) protein (N154), but this glycosylation site is absent in many historical ZIKV isolates. Here, we investigated the role of E protein glycosylation in ZIKV pathogenesis using two contemporary Asian-lineage strains (H/PF/2013 and PRVABC59) and the historical African-lineage strain (MR766). We found that glycosylated viruses were highly pathogenic in
mice. In contrast, nonglycosylated viruses were attenuated, producing lower viral loads in the serum and brain when inoculated subcutaneously but remaining neurovirulent when inoculated intracranially. These results suggest that E glycosylation is advantageous in the periphery but not within the brain. Accordingly, we found that glycosylation facilitated infection of cells expressing the lectins dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) or DC-SIGN-related (DC-SIGNR), suggesting that inefficient infection of lectin-expressing leukocytes could contribute to the attenuation of nonglycosylated ZIKV in mice.
It is unclear why the ability of Zika virus (ZIKV) to cause serious disease, including Guillain-Barré syndrome and birth defects, was not recognized until recent outbreaks. One contributing factor could be genetic differences between contemporary ZIKV strains and historical ZIKV strains. All isolates from recent outbreaks encode a viral envelope protein that is glycosylated, whereas many historical ZIKV strains lack this glycosylation. We generated nonglycosylated ZIKV mutants from contemporary and historical strains and evaluated their virulence in mice. We found that nonglycosylated viruses were attenuated and produced lower viral loads in serum and brains. Our studies suggest that envelope protein glycosylation contributes to ZIKV pathogenesis, possibly by facilitating attachment to and infection of lectin-expressing leukocytes.
The current spreading coronavirus SARS-CoV-2 is highly infectious and pathogenic. In this study, we screened the gene expression of three host receptors (ACE2, DC-SIGN and L-SIGN) of SARS ...coronaviruses and dendritic cells (DCs) status in bulk and single cell transcriptomic datasets of upper airway, lung or blood of COVID-19 patients and healthy controls. In COVID-19 patients, DC-SIGN gene expression was interestingly decreased in lung DCs but increased in blood DCs. Within DCs, conventional DCs (cDCs) were depleted while plasmacytoid DCs (pDCs) were augmented in the lungs of mild COVID-19. In severe cases, we identified augmented types of immature DCs (CD22+ or ANXA1+ DCs) with MHCII downregulation. In this study, our observation indicates that DCs in severe cases stimulate innate immune responses but fail to specifically present SARS-CoV-2. It provides insights into the profound modulation of DC function in severe COVID-19.
The efficient spread of SARS-CoV-2 resulted in a unique pandemic in modern history. Despite early identification of ACE2 as the receptor for viral spike protein, much remains to be understood about ...the molecular events behind viral dissemination. We evaluated the contribution of C-type lectin receptors (CLR
S
) of antigen-presenting cells, widely present in respiratory mucosa and lung tissue. DC-SIGN, L-SIGN, Langerin and MGL bind to diverse glycans of the spike using multiple interaction areas. Using pseudovirus and cells derived from monocytes or T-lymphocytes, we demonstrate that while virus capture by the CLRs examined does not allow direct cell infection, DC/L-SIGN, among these receptors, promote virus transfer to permissive ACE2
+
Vero E6 cells. A glycomimetic compound designed against DC-SIGN, enable inhibition of this process. These data have been then confirmed using authentic SARS-CoV-2 virus and human respiratory cell lines. Thus, we described a mechanism potentiating viral spreading of infection.
Glycan–lectin interactions play an essential role in different cellular processes. One of their main functions is involvement in the immune response to pathogens or inflammation. However, cancer ...cells and viruses have adapted to avail themselves of these interactions. By displaying specific glycosylation structures, they are able to bind to lectins, thus promoting pathogenesis. While glycan–lectin interactions promote tumor progression, metastasis, and/or chemoresistance in cancer, in viral infections they are important for viral entry, release, and/or immune escape. For several years now, a growing number of investigations have been devoted to clarifying the role of glycan–lectin interactions in cancer and viral infections. Various overviews have already summarized and highlighted their findings. In this review, we consider the interactions of the lectins MGL, DC-SIGN, selectins, and galectins in both cancer and viral infections together. A possible transfer of ways to target and disrupt them might lead to new therapeutic approaches in different pathological backgrounds.
Abstract
Background
Chikungunya infections range from subclinical infection to debilitating arthralgia and to chronic inflammatory rheumatism. Tumor necrosis factor (TNF) α, DC-SIGN (dendritic ...cell–specific intercellular adhesion molecule 3–grabbing nonintegrin), Toll-like receptor (TLR) 3, and blood groups have been directly or indirectly implicated in the susceptibility and pathogenesis of chikungunya.
Methods
To test the hypothesis that polymorphisms in genes coding for these molecules determine clinical outcomes of chikungunya infection, a retrospective case-control study was performed in León, Nicaragua. The study included 132 case patients and 132 controls, matched for age, sex and neighborhood. Case patients had clinical symptoms of chikungunya, which was diagnosed by means of polymerase chain reaction. Controls were individuals not reporting abrupt presentation of clinical chikungunya-like symptoms. Polymorphisms were identified by TaqMan single-nucleotide polymorphism genotyping assays.
Results
After adjustment for sociodemographic risk factors, chikungunya disease was associated with polymorphism in DC-SIGN and TLR3 genes (odds ratios, 5.2 and 3.3, respectively), and TNF-α with reduced persistent joint pain (0.24). Persistent joint pain was also associated with age, female sex and other comorbid conditions. Most interestingly, the Lewis-negative phenotype was strongly associated with both symptomatic chikungunya and immunoglobulin G seropositivity (odds ratios, 2.7, and 3.3, respectively).
Conclusion
This study identified polymorphisms in DC-SIGN, TLR3, and TNF-α genes as well as Lewis-negative phenotype as risk factors for chikungunya infection and disease progression.
Host genetic factors influence susceptibility to chikungunya infection and disease progression. Polymorphisms in DC-SIGN, Toll-like receptor 3, and Lewis blood group genes were associated with disease susceptibility, and polymorphism in tumor necrosis factor α gene with joint pain persistence.
Flaviviruses encode one, two, or no
-linked glycosylation sites on their envelope proteins. Glycosylation can impact virus interactions with cell surface attachment factors and also may impact virion ...stability and virus replication. Envelope protein glycosylation has been identified as a virulence determinant for multiple flaviviruses, but the mechanisms by which glycosylation mediates pathogenesis remain unclear. In this Gem, we summarize current knowledge on flavivirus envelope protein glycosylation and its impact on viral infection and pathogenesis.
Exosomes, nano‐sized secreted extracellular vesicles (EVs), are actively studied for their diagnostic and therapeutic potential. In particular, exosomes secreted by dendritic cells (DCs) have been ...shown to carry MHC‐peptide complexes allowing efficient activation of T lymphocytes, thus displaying potential as promoters of adaptive immune responses. DCs also secrete other types of EVs of different size, subcellular origin and protein composition, whose immune capacities have not been yet compared to those of exosomes. Here, we show that large EVs (lEVs) released by human DCs are as efficient as small EVs (sEVs), including exosomes, to induce CD4+ T‐cell activation in vitro. When released by immature DCs, however, lEVs and sEVs differ in their capacity to orient T helper (Th) cell responses, the former favouring secretion of Th2 cytokines, whereas the latter promote Th1 cytokine secretion (IFN‐γ). Upon DC maturation, however, these functional differences are abolished, and all EVs become able to induce IFN‐γ. Our results highlight the need to comprehensively compare the functionalities of EV subtypes in all patho/physiological systems where exosomes are claimed to perform critical roles.
Synopsis
Dendritic cell (DC)‐derived extracellular vesicle (EV) subtypes show functional heterogeneity depending on the DC maturation stage, thus highlighting the importance of characterizing all EV subtypes for their function.
Human primary dendritic cell (DC)‐derived EVs of different sizes, including large EVs and mixed exosomes and non‐exosomal small EVs, induce equally well activation and proliferation of allogeneic T lymphocytes.
When produced by immature DCs, large EVs induce prominent secretion of Th2‐associated cytokines, whereas medium and small EVs induce secretion of Th1‐associated cytokines.
The different qualitative activities of large and small/medium EVs are due to different ratios of EV surface‐exposed T cell‐binding proteins CD40, DC‐SIGN (abundant only on small/medium EVs) and CD80 (present on all EVs).
When produced by IFN‐γ‐matured DCs, all EVs induce prominent secretion of Th1‐associated cytokines, thus displaying similar functional activities.
Dendritic cell (DC)‐derived extracellular vesicle (EV) subtypes show functional heterogeneity depending on the DC maturation stage, thus highlighting the importance of characterizing all EV subtypes for their function.
The synthesis of new biocompatible antiviral materials to fight against the development of multidrug resistance is being widely explored. Due to their unique globular structure and excellent ...properties, 60fullerene-based antivirals are very promising bioconjugates. In this work, fullerene derivatives with different topologies and number of glycofullerene units were synthesized by using a SPAAC copper free strategy. This procedure allowed the synthesis of compounds
-
, containing from 20 to 40 mannose units, in a very efficient manner and in short reaction times under MW irradiation. The glycoderivatives were studied in an infection assay by a pseudotyped viral particle with Ebola virus GP1. The results obtained show that these glycofullerene oligomers are efficient inhibitors of EBOV infection with IC
s in the nanomolar range. In particular, compound
, with four glycofullerene moieties, presents an outstanding relative inhibitory potency (RIP). We propose that this high RIP value stems from the appropriate topological features that efficiently interact with DC-SIGN.
SARS-CoV-2 infection-which involves both cell attachment and membrane fusion-relies on the angiotensin-converting enzyme 2 (ACE2) receptor, which is paradoxically found at low levels in the ...respiratory tract
, suggesting that there may be additional mechanisms facilitating infection. Here we show that C-type lectin receptors, DC-SIGN, L-SIGN and the sialic acid-binding immunoglobulin-like lectin 1 (SIGLEC1) function as attachment receptors by enhancing ACE2-mediated infection and modulating the neutralizing activity of different classes of spike-specific antibodies. Antibodies to the amino-terminal domain or to the conserved site at the base of the receptor-binding domain, while poorly neutralizing infection of ACE2-overexpressing cells, effectively block lectin-facilitated infection. Conversely, antibodies to the receptor binding motif, while potently neutralizing infection of ACE2-overexpressing cells, poorly neutralize infection of cells expressing DC-SIGN or L-SIGN and trigger fusogenic rearrangement of the spike, promoting cell-to-cell fusion. Collectively, these findings identify a lectin-dependent pathway that enhances ACE2-dependent infection by SARS-CoV-2 and reveal distinct mechanisms of neutralization by different classes of spike-specific antibodies.
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