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.

Genetic variation of hepatitis B virus and its significance forpathogenesis

Hepatitis B virus(HBV)has a worldwide distribution and is endemic in many populations.Due to its unique life cycle which requires an error-prone reverse transcriptase for replication,it constantly evolves,resulting in tremendous genetic variation in the form of genotypes,sub-genotypes,and mutations.In recent years,there has been considerable research on the relationship between HBV genetic variation and HBV-related pathogenesis,which has profound implications in the natural history of HBV infection,viral detection,immune prevention,drug treatment and prognosis.In this review,we attempted to provide a brief account of the influence of HBV genotype on the pathogenesis of HBV infection and summarize our current knowledge on the effects of HBV mutations in different regions on HBV-associated pathogenesis,with an emphasis on mutations in the pre S/S proteins in immune evasion,occult HBV infection and hepatocellular carcinoma(HCC),mutations in polymerase in relation to drug resistance,mutations in HBV core and e antigen in immune evasion,chronicalization of infection and hepatitis B-related acute-on-chronic liver failure,and finally mutations in HBV x proteins in HCC.

Hepatitis B virus infection:defective surface antigen expression and pathogenesis

Hepatitis B virus(HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understanding HBV-related pathogenesis is of particular importance for prevention and clinical intervention. HBV surface antigens are indispensable for HBV virion formation and are useful viral markers for diagnosis and clinical assessment. During chronic HBV infection, HBV genomes may acquire and accumulate mutations and deletions, leading to the expression of defective HBV surface antigens. These defective HBV surface antigens have been found to play important roles in the progression of HBV-associated liver diseases. In this review, we focus our discussion on the nature of defective HBV surface antigen mutations and their contribution to the pathogenesis of fulminant hepatitis B. The relationship between defective surface antigens and occult HBV infection are also discussed.

Zoonotic origins of human coronavirus 2019(HCoV-19/SARS-CoV-2):why is this work important?

The ongoing pandemic of coronavirus disease 2019 (COVID-19), caused by infection with human coronavirus 2019 (HCoV-19/SARS-CoV-2/2019-nCoV), is a global threat to the human population. Here, we briefly summarize the available data for the zoonotic origins of HCoV-19, with reference to the other two epidemics of highly virulent coronaviruses, SARSCoV and MERS-CoV, which cause severe pneumonia in humans. We propose to intensify future efforts for tracing the origins of HCoV-19, which is a very important scientific question for the control and prevention of the pandemic.

Novel Evidence Suggests Hepatitis B Virus Surface Proteins Participate in Regulation of HBV Genome Replication

Naturally occurring mutations in surface proteins of Hepatitis B virus(HBV) usually result in altered hepatitis B surface antigen(HBsAg) secretion efficiency.In the present study,we reported two conserved residues,M75 and M103 with respect to HBsAg,mutations of which not only attenuated HBsAg secretion(M75 only),but also suppressed HBV genome replication without compromising the overlapping p-gene product.We also found M75 and M103 can initiate truncated surface protein(TSPs) synthesis upon over-expression of full-length surface proteins,which may possibly contribute to HBV genome replication.However,attempts to rescue replicationdefective HBV mutant by co-expression of TSPs initiated from M75 or M103 were unsuccessful,which indicated surface proteins rather than the putative TSPs were involved in regulation of HBV genome replication.

The Protamine-like DNA-binding Protein P6.9 Epigenetically Up-regulates Autographa californica Multiple Nucleopolyhedrovirus Gene Transcription in the Late Infection Phase

Protamines are a group of highly basic proteins first discovered in spermatozoon that allow for denser packaging of DNA than histones and will result in down-regulation of gene transcription[1]. It is well recognized that the Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) encodes P6.9, a protamine-like protein that forms the viral subnucleosome through binding to the viral genome[29]. Previous research demonstrates that P6.9 is essential for viral nucleocapsid assembly, while it has no influence on viral genome replication[31]. In the present study, the role of P6.9 in viral gene transcription regulation is characterized. In contrast to protamines or other protamine-like proteins that usually down-regulate gene transcription, P6.9 appears to up-regulate viral gene transcription at 12-24 hours post infection (hpi), whereas it is non-essential for the basal level of viral gene transcription. Fluorescence microscopy reveals the P6.9's co-localization with DNA is temporally and spatially synchronized with P6.9's impact on viral gene transcription, indicating the P6.9-DNA association contributes to transcription regulation. Chromatin fractionation assay further reveals an unexpected co-existence of P6.9 and host RNA polymerase II in the same transcriptionally active chromatin fraction at 24 hpi, which may probably contribute to viral gene transcription up-regulation in the late infection phase.

Baculovirus per os Infectivity Factors Are Involved in HearNPV ODVs Infection of HzAM1 Cells in vitro

Baculoviruses produce two viral phenotypes, the budded virus (BV) and the occlusion-derived virus (ODV). ODVs are released from occlusion bodies in the midgut where they initiate a primary infection. Due to the lack of an in vitro system, the molecular mechanism of ODV infection is still unclear. Here we present data demonstrating that Helicoverpa armigera nucleopolyhedrovirus (HearNPV) ODV infected cultured Hz-AM1 cells in a pH dependent manner. The optimal pH for ODV infection was 8.5, which is same to that in the microvilli of midgut epithelial cells, the ODV native infection sites. Antibodies neutralization analysis indicated that four HearNPV oral infection essential genes p74, pif-1, pif-2 and pif-3 are also essential for HearNPV ODV infection in vitro. Thus, HearNPV-HzAM1 system can be used to analyze the mechanism of ODV entry.

Putative Phosphorylation Sites On WCA Domain of HA2 Is Essential For Helicoverpa armigera Single Nucleopolyhedrovirus Replication

Protein phosphorylation is one of the most common post-translational modification processes that play an essential role in regulating protein functionality.The Helicoverpa armigera single nucleopolyhedrovirus (HearNPV) orf2-encoded nucleocapsid protein HA2 participates in orchestration of virus-induced actin polymerization through its WCA domain,in which phosphorylation status are supposed to be critical in respect to actin polymerization.In the present study,two putative phosphorylation sites (232Thr and 250Ser) and a highly conserved Serine (245Ser) on the WCA domain of HA2 were mutated,and their phenotypes were characterized by reintroducing the mutated HA2 into the HearNPV genome.Viral infectivity assays demonstrated that only the recombinant HearNPV bearing HA2 mutation at 245Ser can produce infectious virions,both 232Thr and 250Ser mutations were lethal to the virus.However,actin polymerization assay demonstrated that all the three viruses bearing HA2 mutations were still capable of initiating actin polymerization in the host nucleus,which indicated the putative phosphorylation sites on HA2 may contribute to HearNPV replication through another unidentified pathway.

Combinational benefit of antihistamines and remdesivir for reducing SARS-CoV-2 replication and alleviating inflammation-induced lung injury in mice

COVID-19 is an immune-mediated inflammatory disease caused by SARS-CoV-2 infection,the combination of anti-inflammatory and antiviral therapy is predicted to provide clinical benefits.We recently demonstrated that mast cells(MCs)are an essential mediator of SARS-CoV-2-initiated hyperinflammation.We also showed that spike protein-induced MC degranulation initiates alveolar epithelial inflammation for barrier disruption and suggested an off-label use of antihistamines as MC stabilizers to block degranulation and consequently suppress inflammation and prevent lung injury.In this study,we emphasized the essential role of MCs in SARS-CoV-2-induced lung lesions in vivo,and demonstrated the benefits of co-administration of antihistamines and antiviral drug remdesivir in SARS-CoV-2-infected mice.Specifically,SARSCoV-2 spike protein-induced MC degranulation resulted in alveolar-capillary injury,while pretreatment of pulmonary microvascular endothelial cells with antihistamines prevented adhesion junction disruption;predictably,the combination of antiviral drug remdesivir with the antihistamine loratadine,a histamine receptor 1(HR1)antagonist,dampened viral replication and inflammation,thereby greatly reducing lung injury.Our findings emphasize the crucial role of MCs in SARS-CoV-2-induced inflammation and lung injury and provide a feasible combination antiviral and anti-inflammatory therapy for COVID-19 treatment.

Washed microbiota transplantation reduces serum uric acid levels in patients with hyperuricaemia

BACKGROUND Previous studies have found that hyperuricaemia(HUA)is closely related to intestinal flora imbalance.AIM The current study investigated the effects and safety of washed microbiota transplantation(WMT)on serum uric acid(SUA)levels in different populations.METHODS A total of 144 patients who received WMT from July 2016 to April 2020 in the First Affiliated Hospital of Guangdong Pharmaceutical University and had SUA data before treatment were selected.Changes in SUA levels before and after treatment were retrospectively reviewed based on short-term and mid-term effects of WMT regimens.SUA levels measured in the last test within 3 mo after the first WMT represented the short-term effect,and SUA levels measured in the last test within 3-6 mo after the first WMT represented the mid-term effect.The patients were divided into an HUA group(SUA>416μM)and a normal uric acid(NUA)group(SUA≥202μM to≤416μM)based on pretreatment SUA levels.RESULTS Average short-term SUA levels in the HUA group decreased after WMT(481.00±99.85 vs 546.81±109.64μM,n=32,P<0.05)in 25/32 patients and returned to normal in 10/32 patients.The shortterm level of SUA reduction after treatment moderately correlated with SUA levels before treatment(r=0.549,R²=0.300,P<0.05).Average SUA levels decreased after the first and second courses of WMT(469.74±97.68 vs 540.00±107.16μM,n=35,and 465.57±88.88 vs 513.19±78.14μM,n=21,P<0.05).Short-term and mid-term SUA levels after WMT and SUA levels after the first,second and third courses of WMT were similar to the levels before WMT in the NUA group(P>0.05).Only 1/144 patients developed mild diarrhea after WMT.CONCLUSION WMT reduces short-term SUA levels in patients with HUA with mild side effects but has no obvious effect on SUA levels in patients with NUA.

Histone deacetylase 3 promotes innate antiviral immunity through deacetylation of TBK1

TANK-binding kinase 1(TBK1),a core kinase of antiviral pathways,activates the production of interferons(IFNs).It has been reported that deacetylation activates TBK1;however,the precise mechanism still remains to be uncovered.We show here that during the early stage of viral infection,the acetylation of TBK1 was increased,and the acetylation of TBK1 at Lys241 enhanced the recruitment of IRF3 to TBK1.HDAC3 directly deacety-lated TBK1 at Lys241 and Lys692,which resulted in the activation of TBK1.Deacetylation at Lys241 and Lys692 was critical for the kinase activity and dimerization of TBK1 respectively.Using knockout cell lines and transgenic mice,we confirmed that a HDAC3 null mutant exhibited enhanced susceptibility to viral challenge via impaired production of type I IFNs.Furthermore,activated TBK1 phosphorylated HDAC3,which promoted the deacetylation activity of HDAC3 and formed a feedback loop.In this study,we illustrated the roles the acetylated and deacetylated forms of TBK1 play in antiviral innate responses and clarified the post-trans-lational modulations involved in the interaction between TBK1 and HDAC3.

SARS-CoV-2-triggered mast cell rapid degranulation induces alveolar epithelial inflammation and lung injury

SARS-CoV-2 infection-induced hyper-inflammation links to the acute lung injury and COVID-19 severity.Identifying the primary mediators that initiate the uncontrolled hypercytokinemia is essential for treatments.Mast cells(MCs)are strategically located at the mucosa and beneficially or detrimentally regulate immune inflammations.In this study,we showed that SARS-CoV-2-triggered MC degranulation initiated alveolar epithelial inflammation and lung injury.SARS-CoV-2 challenge induced MC degranulation in ACE-2 humanized mice and rhesus macaques,and a rapid MC degranulation could be recapitulated with Spike-RBD binding to ACE2 in cells;MC degranulation altered various signaling pathways in alveolar epithelial cells,particularly,the induction of pro-inflammatory factors and consequential disruption of tight junctions.Importantly,the administration of clinical MC stabilizers for blocking degranulation dampened SARS-CoV-2-induced production of pro-inflammatory factors and prevented lung injury.These findings uncover a novel mechanism for SARS-CoV-2 initiating lung inflammation,and suggest an off-label use of MC stabilizer as immunomodulators for COVID-19 treatments.