Role of ISGF3 in modulating the anti-hepatitis B virus activity of interferon-alpha in vitro

Role of ISG15 post-translational modification in immunity against Mycobacterium tuberculosis infection

ISG15 encoded by a type I interferon (IFN) inducible gene mediates an important cellular process called ISGylation. ISGylation emerges as a powerful host tactic against intracellular pathogens like Mycobacterium tuberculosis (Mtb). However, the exact role of ISGylation in immunity remains elusive. To shed light on how ISGylation, which is both interesting and complex, participates in immunity against Mtb, this manuscript summarized the current knowledge about the structural characteristics and targets of ISG15 and how ISGylation cross-talks with other host post-translational modifications to exert its effect.

Interferon-α inhibits cell migration and invasion and induces the expression of antiviral proteins in Huh-7 cells transfected with hepatitis B virus X gene-expressing lentivirus

Hepatitis B virus (HBV) X protein (HBx) serves an important role in HBV infection and the development of HBV-related liver cancer. Interferon-α (IFN-α) is used to treat patients with HBV; however, the role of IFN-α in the development of HBV-related liver cancer remains unclear. The present study established a new HBV-related liver cancer model (Huh-7-HBx) by transfecting the hepatoma cell line Huh-7, with HBx-expressing lentivirus. Following IFN-α treatment, cell viability, migration and invasion, as well as the expression of antiviral proteins in Huh-7-HBx, were subsequently determined. The results demonstrated that HBx-expressing lentivirus had no significant effect on cell viability but promoted the migration and invasion of Huh-7 cells. The expression of the antiviral genes IFN α and β receptor subunit 1 (IFNAR1), IFNAR2, IFN-stimulated gene factor 3, double-stranded RNA-activated protein kinase and ribonuclease L, was also increased. Following treatment of Huh-7-HBx cells with IFN-α, the expression of antiviral genes was increased at the level of transcription and translation, whereas cell migration and invasion was decreased. The present study suggests that IFN-α may attenuate the development of HBV-related liver cancer by reducing cell migration and invasion and promoting the expression of antiviral proteins.

Combination antiretroviral therapy (cART) restores HIV-1 infection-mediated impairment of JAK-STAT signaling pathway

JAK-STAT signaling pathway has a crucial role in host innate immunity against viral infections, including HIV-1. We therefore examined the impact of HIV-1 infection and combination antiretroviral therapy (cART) on JAK-STAT signaling pathway. Compared to age-matched healthy donors (n = 18), HIV-1-infected subjects (n = 18) prior to cART had significantly lower expression of toll-like receptors (TLR-1/4/6/7/8/9), the IFN regulatory factors (IRF-3/7/9), and the antiviral factors (OAS-1, MxA, A3G, PKR, and Tetherin). Three months’ cART partially restores the impaired functions of JAK-STAT-mediated antiviral immunity. We also found most factors had significantly positive correlations (p < 0.05) between each two factors in JAK-STAT pathway in healthy donors (98.25%, 168/171), but such significant positive associations were only found in small part of HIV-1-infected subjects (43.86%, 75/171), and stably increased during the cART (57.31%, 98/171 after 6 months’ cART). With regard to the restoration of some HIV-1 restriction factors, HIV-1-infected subjects who had CD4+ T cell counts > 350//μl responded better to cART than those with the counts < 350/μl. These findings indicate that the impairment of JAK-STAT pathway may play a role in the immunopathogenesis of HIV-1 disease.

Interferon-stimulated gene factor 3 complex is required for the induction of sterile α motif and HD domain-containing protein 1 expression by interferon-α in SMMC-7721 cells

Sterile α motif and HD domain-containing protein 1 (SAMHD1) is a novel intrinsic restriction factor that inhibits the replication of certain retroviruses and DNA viruses through its deoxynucleoside triphosphate triphosphohydrolase activity. A previous study by our group showed that SAMHD1 restrained hepatitis B virus replication and interferon (IFN)‑α induced SAMHD1 expression in liver cells. However the mechanisms of SAMHD1 upregulation by IFN‑α in liver cells have remained elusive. The present study demonstrated that IFN‑α treatment increased SAMHD1 mRNA levels in SMMC‑7721 cells in a time‑dependent manner. Knockdown of STAT1 inhibited the induction of SAMHD1 expression by IFN‑α in SMMC‑7721 cells. STAT2 silencing also suppressed the induction of SAMHD1 expression by IFN‑α in SMMC‑7721 cells. Furthermore, the induction of SAMHD1 expression in SMMC‑7721 cells by IFN‑α was found to be dependent on IFN‑regulatory factor 9 (IRF9). In conclusion, these results suggested that the interferon‑stimulated gene factor 3 complex, which consists of STAT1, STAT2 and IRF9, is required for the induction of SAMHD1 expression by IFN-α in SMMC-7721 cells.

Plants Consumption and Liver Health

The liver is a very important organ with a lot of functions for the host to survive. Dietary components are essential for and can be beneficial or detrimental to the healthy or diseased liver. Plants food is an essential part of the human diet and comprises various compounds which are closely related to liver health. Selected food plants can provide nutritional and medicinal support for liver disease. At the present, the knowledge of the effects of plants on the liver is still incomplete. The most urgent task at the present time is to find the best dietary and medicinal plants for liver health in an endless list of candidates. This review article updates the knowledge about the effects of plants consumption on the health of the liver, putting particular emphasis on the potential beneficial and harmful impact of dietary and medicinal plants on liver function.

IFN-CSP inhibiting hepatitis B virus in HepG2.2.15 cells involves JAK-STAT signal pathway

Frequent and high-dose administration of interferon to patients with viral hepatitis results in various side effects. In our previous study, a novel liver-targeting interferon (IFN-CSP) combining Plasmodium region I peptide with IFNα2b was successfully designed and expressed in the Escherichia coli expression systems. This targeting would target the IFNα2b specifically to the liver, thus reducing the adverse events. In the present study, we further investigated the anti-HBV effects and molecular mechanisms of recombinant IFN-CSP in HepG2.2.15 cell line. Hepatitis B surface antigen (HBsAg) and HBe antigen (HBeAg) in the culture supernatants were analyzed by enzyme-linked immunosorbent assay (ELISA). HBV-DNA was measured by real-time quantitative PCR. HBV core protein was assayed by immunofluorescent and western blot analysis. The expressions of signal transducers and transactivator 1 (STAT1), STAT2, IFN regulatory factor 9 (IRF-9), and 2'-5'-oligoadenylate synthetase 1 (OAS1) were investigated by the reverse transcription PCR and western blot analysis. Results indicate IFN-CSP efficiently inhibited HBsAg and HBeAg secretion, HBV-DNA replication, and HBV core protein expression in HepG2.2.15 cells. The anti-HBV mechanisms involve activation of JAK-STAT signaling and increase of the anti-HBV protein OAS expression. IFN-CSP could be a good substitute for IFNα2b for anti-HBV treatment.

Control of hepatitis B virus replication by interferons and Toll-like receptor signaling pathways

Hepatitis B virus (HBV) infection is one of the major causes of liver diseases, affecting more than 350 million people worldwide. The interferon (IFN)-mediated innate immune responses could restrict HBV replication at the different steps of viral life cycle. Indeed, IFN-α has been successfully used for treatment of patients with chronic hepatitis B. However, the role of the innate immune response in HBV replication and the mechanism of the anti-HBV effect of IFN-α are not completely explored. In this review, we summarized the currently available knowledge about the IFN-mediated anti-HBV effect in the HBV life cycle and the possible effectors downstream the IFN signaling pathway. The antiviral effect of Toll-like receptors (TLRs) in HBV replication is briefly discussed. The strategies exploited by HBV to evade the IFN- and TLR-mediated antiviral actions are summarized.

Suppression of interferon-mediated antiviral immunity by hepatitis B virus: an overview of research progress

Interferon (IFN)-α is an indispensable drug for hepatitis B treatment in clinical settings. However, hepatitis B virus (HBV) can attenuate IFN-mediated antiviral responses to avoid being inhibited or cleared. Much progress has been made in exploring how the IFN-induced anti-HBV effect is inhibited. This review examines and summarizes new advances regarding the molecular mechanism underlying the HBV-induced suppression of type I IFN-mediated antiviral immunity.

Inhibition of alpha interferon (IFN-α)-induced microRNA-122 negatively affects the anti-hepatitis B virus efficiency of IFN-α

Alpha interferon (IFN-α)-based therapy can effectively treat chronic hepatitis B virus (HBV) infection, which causes life-threatening complications. Responses to IFN-α therapy vary greatly in chronic hepatitis B (CHB) patients, but underlying mechanisms are almost unknown. In this study, we found that IFN-α treatment induced a marked decrease of microRNA-122 (miR-122) expression in hepatocytes. We next showed that IFN-α-induced miR-122 downregulation was only partly due to transcriptional suppression. One IFN-stimulated gene (ISG), NT5C3, which was identified as a miR-122 target, efficiently inhibited miR-122 by binding and sequestering miR-122 with its mRNA 3'-untranslated region (3'-UTR), indicating that this ISG is involved in IFN-α-mediated miR-122 suppression. Notably, the inhibitory effect of IFN-α on miR-122 was completely abolished by blocking IFN-α-induced upregulation of NT5C3 mRNA expression by RNA interference (RNAi). Meanwhile, we observed that miR-122 dramatically inhibited HBV expression and replication. Finally, we showed that IFN-α-mediated HBV-inhibitory effects could be enhanced significantly by blocking IFN-α-induced downregulation of miR-122. We therefore concluded that IFN-α-induced inhibition of miR-122 may negatively affect the anti-HBV function of IFN-α. These data provide valuable insights for a better understanding of the antiviral mechanism of IFN-α and raise further potential interest in enhancing its anti-HBV efficacy.

Functional Characterization of Interferon Regulation Element of Hepatitis B virus Genome In Vivo

The roles of interferon regulatory element (IRE) in Hepatitis B virus (HBV) genome on inhibitory effect of interferon against HBV are controversial in vitro. This study aimed to determine the functional characterization of HBV-IRE sequence in vivo. Wild-type or IRE-mutant HBV replication-competent mice were firstly established, and mice were subquently treated with polyinosinic-polytidylin acid (polyI.C) or phosphate-buffered saline via intraperitoneal. Results showed that PolyI.C inhibited viral replication, and increased the level of 2',5'-oligoadenylate synthase mRNA transcripts, a marker of INF-α/β induction. Between wild-type and IRE-mutant HBV replication-competent mice, the levels of HBV-RNA and HBV-DNA replication intermediates were similar. After PolyI.C treatment, the decreasing of HBV-RNA was similar between two groups, but HBV-DNA replication intermediates decreased significantly less in IRE-mutant than wild-type HBV replication-competent mice. These findings suggested that IRE mutant reduced the inhibitory effect of interferon on HBV replication, which played a role in antiviral effect of interferon against HBV.

Advance in molecular mechanism of interferon to treat chronic hepatitis B

The antiviral efficacy of interferon-α (IFN-α) therapy for chronic hepatitis B (CHB) is not only related to DNA load and genetype of HBV before treatment, gene mutation of HBV and polymorphism of type II HLA in the host, but also depends on the immunity of CHB patients. Researchers pay more and more attention to the mutant strain of virus and phenotypes of genes. However, the mechanism of interferon to resist HBV and the escape mechanism of HBV against the IFN therapy have not been clarified yet. This paper reviews the mechanism of IFN therapy and the influencing factors at molecular and genetic levels.

Proteome responses to stable hepatitis B virus transfection and following interferon alpha treatment in human liver cell line HepG2

Hepatitis B virus (HBV) infection is a worldwide health problem and may develop to liver fibrosis, cirrhosis, and even hepatocellular carcinoma. To investigate the global proteome responses of liver-derived cells to HBV infection and IFNalpha treatment, 2-DE and MS-based analysis were performed to compare the proteome changes between HBV stably transfected cell line HepG2.2.15 and its parental cell line HepG2, as well as HepG2.2.15 before and after IFNalpha treatment (5000 IU/mL for 72 h). Compared to HepG2, 12 of 18 down-regulated and 27 of 32 up-regulated proteins were identified in HepG2.2.15. After IFNalpha treatment, 6 of 7 down-regulated and 11 of 14 up-regulated proteins were identified. Differentially expressed proteins caused by HBV infection were involved with cytoskeletal matrix, heat shock stress, kinases/signal transduction, protease/proteasome components, etc. Prohibitin showed a dose-dependent up-regulation during IFNalpha treatment and might play a potent role in anti-HBV activities of IFNalpha by enhancing the crossbinding p53 expression to achieve the apoptosis of HBV infected liver cells. Down-regulation of interferon-stimulated gene 15 (ISG15) in HepG2.2.15 and recovery by IFNalpha suggested its relationship with IFNalpha's anti-HBV effect.