NS5B

About: NS5B is a research topic. Over the lifetime, 1314 publications have been published within this topic receiving 59534 citations.

2-芳基-3-羰基喹诺酮：新型hcv ns5b多聚酶抑制剂的设计、合成和活性评估

Abstract: Hepatitis C virus (HCV) infection is a global health problem that impacts approximately 180 million individuals. Until recently the current therapy for treating HCV infection has been regular injections of pegalated α-interferon (PEG-IFN) with daily oral administration of ribavirin (RBV). However, PEG-IFN/RBV treatment is only effective for only 50% of genotype 1 patients and associated with significant adverse effects including fatigue, hemolytic anemia, depression, and flu- like symptoms. Therefore, the search for direct acting antivirals (DAAs) that are safe and effective has become an urgent endeavor. HCV NS5B polymerase, an essential enzyme for the HCV RNA replication, has emerged as an attractive and vali- dated target for the direct HCV therapeutic intervention. Since NS5B polymerase needs a divalent metal ion as a cofactore in the active site for its catalytic function, the metal chelation motif-containing quinolone-3-carboxylic scaffold has been ex- plored as a new class of non-nucleoside NS5B inhibitors. Two groups have recently reported a preliminary structure-activity relationship (SAR) study on the 4-quinolone-3-carboxylic acids as HCV NS5B inhibitors, just focused on the N-1, C-3 and C-6/7 substitutions. Based on the binding mode revealed by the cocrystal structure of the quinolone inhibitor bound to the NS5B enzyme, for the first time we proposed to introduce a hydrophobic group at C-2 position on the quinolone ring to im- prove the anti-HCV potency. By making use of the new method to synthesize 2-substituted quinolone-3-carboxylic acid derivatives recently developed by our group, we conducted a comprehensive SAR study on the 2-aryl-3-carbonylquinolone-based non-nucleoside inhibitors of HCV NS5B polymerase. Starting from the readily accessible amides and 3-oxo-3-arylpropanoates, structurally diverse 2-substituted quinolone-3-carboxylic acid derivatives were effi- ciently furnished by a tandem addition-elimination reaction/nucleophilic aromatic substitution reaction via an imine-enamine intermediate. The anti-HCV potency and cytotoxicity were evaluated in the HCV-infected host cells Huh7.5.1 assay system. To our delight, the incorporation of a hydrophobic aryl group into 2-position of the quinolone core really enhanced the in- hibitory activity against the HCV replication in the host cells with a 2-fold selectivity over the cytotoxicity. Meanwhile, a small size hydrophobic group at N-1 position was favored for the 2-arylquinolone-derived NS5B inhibitors. Further structural variation was investigated on the C-3 and C-7 substituents, with an aromatic ester and an N-methyl piperazine being an opti-

Phylogenetic investigation of nosocomial transmission of hepatitis C virus in an oncology ward

Abstract: Nosocomial hepatitis C virus (HCV) infections have been reported from different health-care settings worldwide. Twenty patients, treated at the same oncology department, with no previous record of hepatitis C infection, tested positive for anti-HCV antibodies between November 2007 and June 2008. Twelve of the newly infected patients were found to be HCV RNA positive. The common origin of the infections was assumed. To investigate the relatedness of the detected viral strains phylogenetic analyses were performed using sequences from the NS5B and E1/E2 genome regions. A patient carrying HCV for years was also involved in the study. She was treated at the same oncology department and was considered a possible infectious source. The previous HCV carrier harbored subtype 1b, while all other patients were infected with subtype 1a. Sequences from the 12 newly infected patients formed two groups. The viral sequences within the groups were very closely related. A greater evolutionary distance was observed between the two groups; however, their relatedness could be demonstrated by sequences from both regions with high statistical support. The results indicated that nosocomial transmission occurred. The phylogenetic analyses suggested that the viruses originated from a common source, possibly a patient carrying highly divergent variants. This presumed infectious source could not be identified in the course of this study. The genotype distribution of Hungarian control sequences included in the analysis confirmed this conclusion, since HCV genotype 1a was found to be relatively uncommon.

Characterization of RNA-dependent RNA polymerase activity of CSFV NS5B proteins expressed in Escherichia coli.

Abstract: The full-length NS5B protein, and the truncated NS5B proteins of classical swine fever virus (CSFV) resulted from deletion of 24, 36, 65 or 82, amino acid residues at the C terminal were expressed in Escherichia coli cells and purified with a C-terminal hexahistidine tag. In addition to the full-length NS5B protein, those truncated NS5B proteins with deletion of 24, 36, or 65 amino acid residues were demonstrated to have RNA-dependent RNA polymerase (RdRp) activity, which was not found in the truncated NS5B proteins with deletion of 82 amino acid residues. Analysis of the template specificity of CSFV RdRp was done containing the different NS5B proteins with RdRp activity. It was shown that the template specificity of the enzyme was not strict with NS5B proteins truncated, suggesting that the C terminal of CSFV NS5B protein was involved in the template specificity of the enzyme. Site-directed mutagenesis of and prediction of the secondary structure of 3' terminal sequence of the template indicated that the cytidines at 3' terminus and the correct secondary structure of the template were essential to initiation of RNA synthesis by RdRp. Oxidation of the hydroxyl groups of the RNA template revealed that both the de novo initiation mechanism and the template-priming mechanism preference might be employed by the CSFV RdRp.

Detection of HCV-Specific IFN-γ Responses in HCV Antibody and HCV RNA Negative Injecting Drug Users.

Abstract: Background: Detectable HCV-specific cellular immune responses in HCV antibody and RNA negative people who inject drugs (PWID) raise the question of whether some are resistant to HCV infection. Immune responses from people who have been exposed to hepatitis C virus (HCV) and remain anti-HCV negative are of interest for HCV vaccine development; however, limited research addresses this area. Objectives: In a cohort of HCV antibody and RNA negative PWID, we assessed whether the presence of HCV-specific IFN-γ responses or genetic associations provide any evidence of protection from HCV infection. Patients and Methods: One hundred and ninety-eight participants were examined longitudinally for clinical, behavioral, social, environmental and genetic characteristics (IFNL3 genotype [formally IL-28B] and HLA type). Sixty-one of the 198 participants were HCV antibody and RNA negative, with 53 able to be examined longitudinally for HCV-specific IFN-γ ELISpot T cell responses. Results: Ten of the 53 HCV antibody and RNA negative participants had detectable HCV-specific IFN-γ responses at baseline (18%). The magnitude of IFN-γ responses averaged 131 +/- 96 SFC/106 PBMC and the breadth was mean 1 +/- 1 pool positive. The specificity of responses were mainly directed to E2, NS4b and NS5b. Participants with (10) and without (43) HCV-specific IFN-γ responses did not differ in behavioral, clinical or genetic characteristics (P > 0.05). There was a larger proportion sharing needles (with 70%, without 49%, P = 0.320) and a higher incidence of HCV (with 35.1 per 100 py, 95% CI 14.6, 84.4, without 16.0 per 100 py, 95% CI 7.2, 35.6, P = 0.212) in those with IFN-γ responses, although not statistically significant. Half the participants with baseline IFN-γ responses became HCV RNA positive (5/10), with one of these participants spontaneously clearing HCV. The spontaneous clearer had high magnitude and broad Th1 responses, favorable IFNL3 genotype and favorable HLA types. Conclusions: This study demonstrated the detection of HCV-specific IFN-γ responses in HCV antibody and RNA negative individuals, with a tendency for HCV-specific IFN-γ responses to be associated with HCV exposure. The potential role of HCV-specific IFN-γ responses in those who remained HCV RNA negative is of value for the development of novel HCV therapeutics.