SARS-CoV-2 exacerbates proinflammatory responses in myeloid cells through C-type lectin receptors and Tweety family member 2.

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.

Antibody-Decorated Nanoplatform to Reprogram Macrophage and Block Immune Checkpoint LSECtin for Effective Cancer Immunotherapy.

Repolarizing tumor-associated macrophages (TAMs) into tumor-inhibiting M1 macrophages has been considered a promising strategy for enhanced cancer immunotherapy. However, several immunosuppressive ligands (e.g., LSECtin) can still be highly expressed on M1 macrophages, inducing unsatisfactory therapeutic outcomes. We herein developed an antibody-decorated nanoplatform composed of PEGylated iron oxide nanoparticles (IONPs) and LSECtin antibody conjugated onto the surface of IONPs via the hydrazone bond for enhanced cancer immunotherapy. After intravenous administration, the tumor microenvironment (TME) pH could trigger the hydrazone bond breakage and induce the disassociation of the nanoplatform into free LSECtin antibodies and IONPs. Consequently, the IONPs could repolarize TAMs into M1 macrophages to remodel immunosuppressive TME and provide an additional anticancer effect via secreting tumoricidal factors (e.g., interlukin-12). Meanwhile, the LSECtin antibody could further block the activity of LSECtin expressed on M1 macrophages and relieve its immunosuppressive effect on CD8+ T cells, ultimately leading to significant inhibition of tumor growth.

Cirrhosis-downregulated LSECtin can be retrieved by cytokines, shifts the TLR-induced LSECs secretome and correlates with the hepatic Th response.

BACKGROUND AND AIMS: We evaluated tolerogenic C-type lectin LSECtin loss in cirrhosis and its potential regulation by cytokines. METHODS: Liver tissue from patients with cirrhosis and healthy controls, immortalised and generated LSECtin-CRISPR immortalised LSECs, and murine primary LSECs from the CCl4 model were handled. RESULTS: LSECtin expression was reduced in liver tissue from cirrhotic patients, and it decreased from compensated to decompensated disease. Increased phosphorylation of MAPK, Akt and NFkB was observed upon LSECtin stimulation in LSEC murine cell line, showing a pattern of inflammatory and chemotactic cytokines either restrained (IL-10, CCL4) or unrestrained (TNF-α, IL-1ß, IL-6, CCL2). CD44 attenuated whereas LAG-3 increased all substrates phosphorylation in combination with TLR4 and TLR2 ligands except for NFkB. TNF-α, IL-1 ß, IL-6 and CCL2 were restrained by LSECtin crosslinking on TLRs studied. Conversely, IL-10 and CCL4 were upregulated, suggesting a LSECtin-TLRs synergistic effect. Also, LSECtin was significantly induced after IL-13 stimulation or combined with anti-inflammatory cytokines in cirrhotic and immortalised LSECs. Th17 and regulatory T cells were progressively increased in the hepatic tissue from compensated to decompensated patients. A significant inverse correlation was present between gene expression levels of CLEC4G/LSECtin and RORγT and FOXP3 in liver tissues. CONCLUSION: LSECtin restrains TLR proinflammatory secretome induced on LSECs by interfering immune response control, survival and MAPKs signalling pathways. The cytokine-dependent induction of LSECtin and the association between LSECtin loss and Th17 cell subset expansion in the liver, provides a solid background for exploring LSECtin retrieval as a mechanism to reprogram LSEC homeostatic function hampered during cirrhosis.

Molecular Events in Immune Responses to Sublingual Influenza Vaccine with Hemagglutinin Antigen and Poly(I:C) Adjuvant in Nonhuman Primates, Cynomolgus Macaques.

Sublingual vaccines offer the benefits of inducing mucosal immunity to protect against respiratory viruses, including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and influenza, while also enabling needle-free self-administration. In a previous study, a sublingual SARS-CoV-2 vaccination was created by combining a recombinafigureCoV-2 spike protein receptor-binding domain antigen with a double strand RNA Poly(I:C) adjuvant. This vaccine was tested on nonhuman primates, Cynomolgus macaques. This study examined the immune and inflammatory responses elicited by the sublingual influenza vaccine containing hemagglutinin (HA) antigen and Poly(I:C) adjuvants, and assessed the safety of this vaccine in nonhuman primates. The Poly(I:C)-adjuvanted sublingual vaccine induced both mucosal and systemic immunities. Specifically, the sublingual vaccine produced HA-specific secretory IgA antibodies in saliva and nasal washings, and HA-specific IgA and IgG were detected in the blood. This vaccine appeared to be safe, as judged from the results of blood tests and plasma C-reactive protein levels. Notably, sublingual vaccination neither increased the production of inflammation-associated cytokines-IFN-alpha, IFN-gamma, and IL-17-in the blood, nor upregulated the gene expression of proinflammatory cytokines-IL12A, IL12B, IFNA1, IFNB1, CD69, and granzyme B-in white blood cells. Moreover, DNA microarray analyses revealed that sublingual vaccination evoked both enhancing and suppressing expression changes in genes associated with immune-related responses in cynomolgus monkeys. Therefore, the sublingual vaccine with the Poly(I:C) adjuvant is safe, and creates a balanced state of enhancing and suppressing the immune-related response.

CXCL8 Up-Regulated LSECtin through AKT Signal and Correlates with the Immune Microenvironment Modulation in Colon Cancer.

BACKGROUND: The role of CXCL8 and LSECtin in colon cancer liver metastasis and immune checkpoint inhibitors (ICIs) treatment effect were widely recognized. However, the regulatory role of CXCL8 on LSECtin is still unclear. METHODS: The expression of CXCL8 or LSECtin was analyzed by TCGA database, and verified by GES110225 and clinical samples. The relationship between the expression of CXCL8 or LSECtin and immune cells infiltration, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, Gene Ontology (GO) items, stromal score, Estimation of STromal and Immune cells in MAlignant Tumours (ESTIMAT) immune score, tumor mutation burden (TMB), mismatch repair gene and immune checkpoints expression were analyzed by Spearman. The effects of CXCL8 on LSECtin expression, proliferation, and invasion ability were clarified by recombinant CXCL8 or CXCL8 interfering RNA. RESULTS: In colon cancer, the expression of CXCL8 was higher, but LSECtin was lower than that in normal mucosa. The expression of CXCL8 or LSECtin was significantly positively correlated with immune cells infiltration, stromal score, ESTIMATE immune score, TMB, and immune checkpoints expression. The expression of LSECtin was closely related to the cytokine-cytokine receptor interaction pathway and response of chemokine function, such as CXCL8/CXCR1/2 pathway. There was a significant positive correlation between the expression of CXCL8 and LSECtin in colon cancer. CXCL8 up-regulated LSECtin through AKT signal and promoted the proliferation and invasion ability of colon cancer. CONCLUSIONS: CXCL8 up-regulated LSECtin by activating AKT signal and correlated with the immune microenvironment modulation in colon cancer.

Clinical significance of LSECtin and its association with PVR in non-small-cell lung cancer patients.

BACKGROUND: Liver and lymph node sinusoidal endothelial cell C-type lectin (LSECtin) is one of the new generation immune checkpoint ligand molecules and plays an important role in the immune environment. Poliovirus receptor (PVR), as another immunosuppression-related molecule, is upregulated in various malignant tumors. However, the clinical value of LSECtin and the correlation of LSECtin with PVR in non-small-cell lung cancer (NSCLC) remain to be elucidated. In this study, a retrospective study was performed to address these issues. METHODS: This retrospective study included 98 patients with NSCLC. Immunohistochemistry (IHC) was used to detect the expression of LSECtin and PVR in the paraffin-embedded tumor tissue specimens. LSECtin was analyzed for associations with the survival rate and overall survival (OS) of the subjects. The mRNA expression of LSECtin and PVR was assessed using the expression data from The Cancer Genome Atlas (TCGA) database. Clinical characteristics, prognosis, and the expression of LSECtin and PVR were included in the statistical analysis. RESULTS: High positive rates of LSECtin were found in the patients with NSCLC who were nonsmokers, at advanced stages, or had lung adenocarcinoma. Patients with positive LSECtin expression had a significantly lower survival rate (P=0.008) and shorter OS (P=0.017) than those with negative LSECtin. Significant correlation was found between the LSECtin and PVR expression in the patients with NSCLC (P<0.001). CONCLUSIONS: The increased expression of LSECtin was related to the poor prognosis of patients with NSCLC after tumor resection and has the potential value for predicting the prognosis of these patients. The positive correlation between LSECtin and PVR in NSCLC provides a theoretical basis for the future combination therapy of immune checkpoints.

C-type Lectin CD209L/L-SIGN and CD209/DC-SIGN: Cell Adhesion Molecules Turned to Pathogen Recognition Receptors.

C-type lectin CD209/DC-SIGN and CD209L/L-SIGN proteins are distinct cell adhesion and pathogen recognition receptors that mediate cellular interactions and recognize a wide range of pathogens, including viruses such as SARS, SARS-CoV-2, bacteria, fungi and parasites. Pathogens exploit CD209 family proteins to promote infection and evade the immune recognition system. CD209L and CD209 are widely expressed in SARS-CoV-2 target organs and can contribute to infection and pathogenesis. CD209 family receptors are highly susceptible to alternative splicing and genomic polymorphism, which may influence virus tropism and transmission in vivo. The carbohydrate recognition domain (CRD) and the neck/repeat region represent the key features of CD209 family proteins that are also central to facilitating cellular ligand interactions and pathogen recognition. While the neck/repeat region is involved in oligomeric dimerization, the CRD recognizes the mannose-containing structures present on specific glycoproteins such as those found on the SARS-CoV-2 spike protein. Considering the role of CD209L and related proteins in diverse pathogen recognition, this review article discusses the recent advances in the cellular and biochemical characterization of CD209 and CD209L and their roles in viral uptake, which has important implications in understanding the host-pathogen interaction, the viral pathobiology and driving vaccine development of SARS-CoV-2.