乙型肝炎病毒隐匿性感染的临床意义

隐匿性HBV感染是一种常见的、长期的急性肝炎消退后出现一种隐匿性感染。这种形式的残余感染是称为二次隐匿感染（SOI）。HBV感染土拨鼠模型的样本数据表明,

Management of occult hepatitis B virus infection:An update for the clinician

Occult hepatitis B virus(HBV) infection(OBI) is defined by the presence of HBV DNA in the liver tissue of individuals who test negative for hepatitis B surface antigen(HBsAg).Patients who have recovered from acute hepatitis B can carry HBV genomes for a long time and show histological patterns of mild necro-inflammation,even fibrosis,years after the resolution of acute hepatitis,without showing any clinical or biochemical evidence of liver disease.At least in conditions of immunocompetence,OBI is inoffensive itself,but when other relevant causes of liver damage are present it might make the course of the liver disease worse.The risk of HBV transmission through transfusion is related to blood donations negative for HBsAg that have been collected during the pre-seroconversion period or during chronic OBI.Use of HBV nucleic acid amplification testing and multivalent anti-HBs antibodies in the HBsAg assays is recommended for detection of true and false OBI,respectively.It is not known if prior hepatitis B immunization with an optimal anti-HBs response in cases of HBV transmission through organ transplantation can effectively modulate or abort the infection.Use of anti-viral agents as prophylaxis in patients with serological evidence of past HBV infection prevents reactivation of OBI after transplantation in most cases.Reactivation of OBI has been observed in other conditions that cause immunosuppression,in which antiviral therapy could be delayed until the HBV DNA or HBsAg becomes detectable.OBI might contribute to the progression of liver fibrosis and hepatocellular carcinoma development in patients with chronic liver disease.

Pathogenesis of occult chronic hepatitis B virus infection

Occult hepatitis B infection(OBI) is characterized by hepatitis B virus(HBV) DNA in serum in the absence of hepatitis B surface antigen(HBsAg) presenting HBsAg-negative and anti-HBc positive serological patterns.Occult HBV status is associated in some cases with mutant viruses undetectable by HBsAg assays;but more frequently it is due to a strong suppression of viral replication and gene expression.OBI is an entity with world-wide diffusion.The failure to detect HBsAg,despite the persistence of the viral DNA,is due in most cases to the strong suppression of viral replication and gene expression that characterizes this"occult"HBV infection;although the mechanisms responsible for suppression of HBV are not well understood.The majority of OBI cases are secondary to overt HBV infection and represent a residual low viremia level suppressed by a strong immune response together with histological derangements which occurred during acute or chronic HBV infection.Much evidence suggests that it can favour the progression of liver fibrosis and the development of hepatocellular carcinoma.

Risk of hepatitis B reactivation in patients treated with direct-acting antivirals for hepatitis C

The recent introduction of direct-acting antiviral drugs(DAAs) for treatment of the hepatitis C virus(HCV) has greatly improved the management of HCV for infected patients. These viral protein inhibitors act rapidly, allowing HCV clearance and increasing the sustained virological response rates. However, hepatitis B virus(HBV) reactivation has been reported in HCV/HBV co-infected patients. Hepatitis B reactivation refers to an abrupt increase in the HBV and is welldocumented in patients with previously undetected HBV DNA due to inactive or resolved HBV infection. Reactivation can occur spontaneously, but in most cases, it is triggered by various factors. Reactivation can be transient, without clinical symptoms; however, it usually causes a hepatitis flare. HBV reactivation may occur regardless of HCV genotype and type of DAA regimen. HBV screening is strongly recommended for co-infected HCV/HBV patients before initiation and during DAA therapy regardless of HBV status, HCV genotype and class of DAAs used. HBV reactivation can be prevented with pretreatment screening and prophylactic treatment when necessary. Additional data are required to evaluate the underlying mechanisms of HBV reactivation in this setting.

The Flavivirus Protease As a Target for Drug Discovery

Many flaviviruses are significant human pathogens causing considerable disease burdens,including encephalitis and hemorrhagic fever,in the regions in which they are endemic.A paucity of treatments for flaviviral infections has driven interest in drug development targeting proteins essential to flavivirus replication,such as the viral protease.During viral replication,the flavivirus genome is translated as a single polyprotein precursor,which must be cleaved into individual proteins by a complex of the viral protease,NS3,and its cofactor,NS2B.Because this cleavage is an obligate step of the viral life-cycle,the flavivirus protease is an attractive target for antiviral drug development.In this review,we will survey recent drug development studies targeting the NS3 active site,as well as studies targeting an NS2B/NS3interaction site determined from flavivirus protease crystal structures.

Mutagenesis of D80-82 and G83 Residues in West Nile Virus NS2B: Effects on NS2B-NS3 Activity and Viral Replication

Flaviviral NS2B is a required cofactor for NS3 serine protease activity and plays an important role in promoting functional NS2B-NS3 protease configuration and maintaining critical interactions with protease catalysis substrates. The residues D80DDG in West Nile virus (WNV) NS2B are important for protease activity. To investigate the effects of D80DDG in NS2B on protease activity and viral replication, the negatively charged region D80DD and the conserved residue G83 of NS2B were mutated (D80DD/E80EE, D80DD/K80KK, D80DD/A80AA, G83F, G83S, G83D, G83K, and G83A), and NS3 D75A was designated as the negative control. The effects of the mutations on NS2B-NS3 activity, viral translation, and viral RNA replication were analyzed using kinetic analysis of site-directed enzymes and a transient replicon assay. All substitutions resulted in significantly decreased enzyme activity and blocked RNA replication. The negative charge of D80DD is not important for maintaining NS2B function, but side chain changes in G83 have dramatic effects on protease activity and RNA replication. These results demonstrate that NS2B is important for viral replication and that D80DD and G83 substitutions prevent replication; they will be useful for understanding the relationship between NS2B and NS3.

DNA-dependent activator of interferon-regulatory factors inhibits hepatitis B virus replication

AIM： To investigate whether DNA-dependent activator of interferon-regulatory factors （DAI） inhibits hepatitis B virus （HBV） replication and what the mechanism is. METHODS： After the human hepatoma cell line Huh7 was cotransfected with DAI and HBV expressing plas- mid, viral protein （HBV surface antigen and HBV e an- tigen） secretion was detected by enzyme-linked immu- nosorbent assay, and HBV RNA was analyzed by real- time polymerase chain reaction and Northern blotting, and viral DNA replicative intermediates were examined by Southern blotting. Interferon regulatory factor 3 （IRF3） phosphorylation and nuclear translocation were analyzed via Western blotting and immunofluorescence staining respectively. Nuclear factor-KB （NF-KB） activity induced by DAI was detected by immunofluorescence staining of P65 and dual luciferase reporter assay. Tran- swell co-culture experiment was performed in order to investigate whether the antiviral effects of DAI were dependent on the secreted cytokines. RESULTS： Viral protein secretion was significantly re- duced by 57% （P 〈 0.05）, and the level of total HBV RNA was reduced by 67% （P 〈 0.05）. The viral core particle-associated DNA was also dramatically down- regulated in DAI-expressing Huh7 cells. Analysis of involved signaling pathways revealed that activation of NF-KB signaling was essential for DAI to elicit antivi- ral response in Huh7 cells. When the NF-KB signaling pathway was blocked by a NF-KB signaling suppressor （I~：B^-SR）, the anti-HBV activity of DAI was remarkably abrogated. The inhibitory effect of DAI was indepen- dent of IRF3 signaling and secreted cytokines. CONCLUSION： This study demonstrates that DAI can inhibit HBV replication and the inhibitory effect is asso- ciated with activation of NF-KB but independent of IRF3 and secreted cytokines.

Chaetocin reactivates the lytic replication of Epstein-Barr virus from latency via reactive oxygen species

Oxidative stress, regarded as a negative effect of free radicals in vivo, takes place when organisms suffer from harmful stimuli. Some viruses can induce the release of reactive oxygen species （ROS） in infected cells, which may be closely related with their pathogenicity. In this report, chaetocin, a fimgal metabolite reported to have antimicrobial and cytostatic activity, was studied for its effect on the activation of latent Epstein-Barr virus （EBV） in B95-8 cells. We found that chaetocin remarkably up-regulated EBV lytic transcription and DNA replication at a low concentration （50 nmol L-l）. The activation of latent EBV was accompanied by an increased cellular ROS level. N-acetyl-L-cysteine （NAC）, an ROS inhibitor, suppressed chaetocin-induced EBV activation. Chaetocin had little effect on histone H3K9 methylation, while NAC also significantly reduced H3K9 methylation. These results suggested that chaetocin reactivates latent EBV primarily via ROS pathways.