Type-I-IFN-Stimulated Gene TRIM5γ Inhibits HBV Replication by Promoting HBx Degradation

To understand the molecular mechanisms that mediate the anti-hepatitis B virus (HBV) effect of interferon (IFN) therapy, we conduct highthroughput bimolecular fluorescence complementation screening to identify potential physical interactions between the HBx protein and 145 IFNstimulated genes (ISGs). Seven HBx-interacting ISGs have consistent and significant inhibitory effects on HBV replication, among which TRIM5g suppresses HBV replication by promoting K48-linked ubiquitination and degradation of the HBx protein on the K95 ubiquitin site. The B-Box domain of TRIM5g under overexpression conditions is sufficient to trigger HBx degradation and is responsible both for interacting with HBx and recruiting TRIM31, which is an ubiquitin ligase that triggers HBx ubiquitination. High expression levels of TRIM5g in IFN-a-treated HBV patients might indicate a better therapeutic effect. Thus, our studies identify a crucial role for TRIM5g and TRIM31 in promoting HBx degradation, which may facilitate the development of therapeutic agents for the treatment of patients with IFN-resistant HBV infection

Characterization of species-specific genes regulated by E2-2 in human plasmacytoid dendritic cells

Dendritic cells (DCs) are sentinels of the immune system and comprise two distinct subsets: conventional DCs (cDCs) and plasmacytoid DCs (pDCs). Human pDCs are distinguished from mouse pDCs phenotypically and functionally. Basic helix-loop-helix protein E2-2 is defined as an essential transcription factor for mouse pDC development, cell fate maintenance and gene programe. It is unknown whether E2-2 regulation contributes to this species-specific difference. Here we investigated the function of E2-2 in human pDCs and screened human-specific genes regulated by E2-2. Reduced E2-2 expression in human pDC cell line GEN2.2 resulted in diminished IFN-α production in response to CpG but elevated antigen presentation capacity. Gene expression profiling showed that E2-2 silence down-regulated pDC signature genes but up-regulated cDC signature genes. Thirty human-specific genes regulated by E2-2 knockdown were identified. Among these genes, we confirmed that expression of Siglec-6 was inhibited by E2-2. Further more, Siglec-6 was expressed at a higher level on a human pDC subset with drastically lower expression of E2-2. Collectively, these results highlight that E2-2 modulates pDC function in a species-specific manner, which may provide insights for pDC development and functions

CD24-p53 axis suppresses diethylnitrosamine-induced hepatocellular carcinogenesis by sustaining intrahepatic macrophages

It is generally assumed that inflammation following diethylnitrosamine (DEN) treatment promotes development of hepatocellular carcinoma (HCC) through the activity of intrahepatic macrophages. However, the tumor-promoting function of macrophages in the model has not been confirmed by either macrophage depletion or selective gene depletion in macrophages. Here we show that targeted mutation of Cd24 dramatically increased HCC burden while reducing intrahepatic macrophages and DEN-induced hepatocyte apoptosis. Depletion of macrophages also increased HCC burden and reduced hepatocyte apoptosis, thus establishing macrophages as an innate effector recognizing DEN-induced damaged hepatocytes. Mechanistically, Cd24 deficiency increased the levels of p53 in macrophages, resulting in their depletion in Cd24 -/- mice following DEN treatment. These data demonstrate that the Cd24-p53 axis maintains intrahepatic macrophages, which can remove hepatocytes with DNA damage. Our data establish a critical role for macrophages in suppressing HCC development and call for an appraisal of the current dogma that intrahepatic macrophages promote HCC development

Hyper-IL-15 suppresses metastatic and autochthonous liver cancer by promoting tumour-specific CD8+ T cell responses

Liver cancer has a very dismal prognosis due to lack of effective therapy. Here, we studied the therapeutic effects of hyper-interleukin15 (hyper-IL-15), which is composed of IL-15 and the sushi domain of the IL-15 receptor α chain, on metastatic and autochthonous liver cancers

SCARB2/LIMP-2 Regulates IFN Production of Plasmacytoid Dendritic Cells by Mediating Endosomal Translocation of TLR9 and Nuclear Translocation of IRF7

Scavenger receptor class B, member 2 (SCARB2) is essential for endosome biogenesis and reorganization and serves as a receptor for both β-glucocerebrosidase and enterovirus 71. However, little is known about its function in innate immune cells. In this study, we show that, among human peripheral blood cells, SCARB2 is most highly expressed in plasmacytoid dendritic cells (pDCs), and its expression is further upregulated by CpG oligodeoxynucleotide stimulation. Knockdown of SCARB2 in pDC cell line GEN2.2 dramatically reduces CpG-induced type I IFN production. Detailed studies reveal that SCARB2 localizes in late endosome/lysosome of pDCs, and knockdown of SCARB2 does not affect CpG oligodeoxynucleotide uptake but results in the retention of TLR9 in the endoplasmic reticulum and an impaired nuclear translocation of IFN regulatory factor 7. The IFN-I production by TLR7 ligand stimulation is also impaired by SCARB2 knockdown. However, SCARB2 is not essential for influenza virus or HSV-induced IFN-I production. These findings suggest that SCARB2 regulates TLR9-dependent IFN-I production of pDCs by mediating endosomal translocation of TLR9 and nuclear translocation of IFN regulatory factor 7

Interferon-Inducible Cholesterol-25-Hydroxylase Inhibits Hepatitis C Virus Replication via Distinct Mechanisms

Cholesterol 25-hydroxylase (CH25H) as an interferon-stimulated gene (ISG) has recently been shown to exert broad antiviral activity through the production of 25-hydroxycholesterol (25HC), which is believed to inhibit the virus-cell membrane fusion during viral entry. However, little is known about the function of CH25H on HCV infection and replication and whether antiviral function of CH25H is exclusively mediated by 25HC. In the present study, we have found that although 25HC produced by CH25H can inhibit HCV replication, CH25H mutants lacking the hydroxylase activity still carry the antiviral activity against HCV but not other viruses such as MHV-68. Further studies have revealed that CH25H can interact with the NS5A protein of HCV and inhibit its dimer formation, which is essential for HCV replication. Thus, our work has uncovered a novel mechanism by which CH25H restricts HCV replication, suggesting that CH25H inhibits viral infection through both 25HC-dependent and independent events

Interleukin-6 Induces Gr-1+CD11b+ Myeloid Cells to Suppress CD8+ T Cell-Mediated Liver Injury in Mice

Agonist antibodies against CD137 (4-1BB) on T lymphocytes are used to increase host anti-tumor immunity, but often leading to severe liver injury in treated mice or in patients during clinical trials. Interleukin-6 (IL-6) has been reported to protect hepatocyte death, but the role of IL-6 in protecting chronic T cell-induced liver diseases is not clearly defined due to lack of relevant animal models. We aimed to define the role of IL-6 in CD8+ T cell-mediated liver injury induced by a CD137 agonistic mAb (clone 2A) in mice.We expressed IL-6 in the liver by hydrodynamic gene delivery in mice treated with 2A or control mAb and studied how IL-6 treatment affected host immunity and T cell-mediated liver injury. We found that ectopic IL-6 expression in the liver elevated intrahepatic leukocyte infiltration but prevented CD8+ T cell-mediated liver injury. In IL-6 treated mice, CD8+ T cells proliferation and IFN-γ expression were inhibited in the liver. We discovered that IL-6 increased accumulation of Gr-1+CD11b+ myeloid derived suppressor cells (MDSCs) in the liver and spleen. These MDSCs had the ability to inhibit T cells proliferation and activation. Finally, we showed that the MDSCs were sufficient and essential for IL-6-mediated protection of anti-CD137 mAb-induced liver injury.We concluded that IL-6 induced Gr-1+CD11b+ MDSCs in the liver to inhibit T cell-mediated liver injury. The findings have defined a novel mechanism of IL-6 in protecting liver from CD8+ T cell-mediated injury

Efficient Isolation of Mouse Liver NKT Cells by Perfusion

Background: NKT cell is a population of unconventional T cells that mediate both innate and adaptive T cell responses. Since NKT cells are most abundant in the liver, much of NKT biology has been learnt from studies of NKT cells isolated from liver. This is a cumbersome procedure with variations in cell yield. Results: Based on recent evidence that NKT cells reside in liver vascular compartment, we developed a simple method to isolate NKT cells by perfusion with PBS-containing 10 mM of EDTA. The number and cell surface phenotype of liver NKT cells recovered by perfusion and by the traditional method were comparable. The yield of other lymphocytes was also comparable. Conclusion/Significance: Our data demonstrated that liver lymphocytes can be efficiently isolated by simple perfusion. These data provide a convenient method to isolate liver lymphocyte while preserving liver tissue for other analysis

CLISAR-Net: A Deformation-Robust ISAR Image Classification Network Using Contrastive Learning

The inherent unknown deformations of inverse synthetic aperture radar (ISAR) images, such as translation, scaling, and rotation, pose great challenges to space target classification. To achieve high-precision classification for ISAR images, a deformation-robust ISAR image classification network using contrastive learning (CL), i.e., CLISAR-Net, is proposed for deformation ISAR image classification. Unlike traditional supervised learning methods, CLISAR-Net develops a new unsupervised pretraining phase, which means that the method uses a two-phase training strategy to achieve classification. In the unsupervised pretraining phase, combined with data augmentation, positive and negative sample pairs are constructed using unlabeled ISAR images, and then the encoder is trained to learn discriminative deep representations of deformation ISAR images by means of CL. In the fine-tuning phase, based on the deep representations obtained from pretraining, a classifier is fine-tuned using a small number of labeled ISAR images, and finally, the deformation ISAR image classification is realized. In the experimental analysis, CLISAR-Net achieves higher classification accuracy than supervised learning methods for unknown scaled, rotated, and combined deformations. It implies that CLISAR-Net learned more robust deep features of deformation ISAR images through CL, which ensures the performance of the subsequent classification