NS5B

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

Relationship between the effect of interferon therapy and the change of hepatitis C virus non-structural 5B gene.

Abstract: Background: Hepatitis C virus (HCV)-RNA titre has been regarded as a factor affecting the response to interferon (IFN) therapy of patients with chronic hepatitis C (CHC). The focus of our study is the investigation of the nucleotide sequence of HCV-RNA NS5B, which may code RNA-dependent RNA polymerase and NS5A in the sera of 33 patients with CHC prior to IFN therapy. Methods: Hepatitis C virus genotype and HCV-RNA titre were examined by polymerase chain reaction (PCR) and competitive reverse transcriptase-PCR. Results: The sequence for HCV-RNA NS5B (nt 8331–8600 in 1b and 8410–8679 in 2a) was determined by direct sequencing. The changes of the predicted amino acids in the genotype-specific sites of HCV-J, HCV-BK, HC-J4/83, HCV-JT, HCV-N, HC-J6 and HCV-K2a were examined, and the mutation was defined when changes of amino acids in sites specific to different reported genotypes were revealed. The mutations were observed in 6/19 (32%) in genotype 1b and 9/14 (64%) in 2a. In the 1b group, complete response (CR) was achieved in 5/6 of the mutant and in 2/13 of the wild type groups (P < 0.05). No relationship was observed between IFN effectiveness and HCV-RNA titre in the 1b wild type group. In the 2a group, CR was achieved in 4/9 of the mutant and in 4/5 of the wild type groups. An inverse relationship between IFN responsiveness and HCV-RNA titre was apparent in 1b mutant, 2a wild and 2a mutant. Conclusions: These data suggest the possible relationship between changes in the HCV-NS5B gene and the effect of IFN therapy in CHC patients with genotype 1b.

Drug resistance testing in hepatitis C therapy

Abstract: The first direct-acting antivirals (DAAs) have recently been approved for the treatment of chronic HCV infection. These molecules interact with different HCV proteins, including NS3/4A protease, NS5B polymerase and NS5A. Several compounds belonging to distinct drug families are in the advanced stages of clinical development. Whereas most DAAs have demonstrated a potent antiviral activity against HCV, emergence of drug resistance represents a huge challenge with almost all of these drugs. The use of combination therapy greatly increases the chances of achieving rapid and complete viral suppression, preventing selection of DAA resistance. Drug resistance mutations and pathways differ according to antiviral agents and HCV genotypes/subtypes. HCV subtype 1a displays a uniformly lower barrier to resistance than HCV subtype 1b when confronting most HCV protease inhibitors, NS5B non-nucleoside inhibitors and NS5A inhibitors. Broad cross-resistance exists between drugs belonging to the same family, except for NS5...

Correlation of the 5′untranslated region (5′UTR) and non-structural 5B (NS5B) nucleotide sequences in hepatitis C virus subtyping

Abstract: The 5′untranslated region (5′UTR) is often targeted to detect major genotypes in hepatitis C virus (HCV) but its insufficient sequence variation limits its usefulness for differentiating HCV subtypes. Subtyping has important implications to epidemiologic studies, clinical management, and vaccine development. Analysis of the nucleotide sequence of variable regions such as the non-structural 5B (NS5B) is considered the reference method for identifying HCV subtypes. We evaluated the accuracy of subtyping of HCV genotype 1 (HCV-1) samples from the Philippines by 5′UTR sequencing as compared with the NS5B sequence. A total of 30 patients infected with HCV-1 previously confirmed by PCR-RFLP and clinically diagnosed with chronic hepatitis C were analyzed. Nucleotide sequencing of the 5′UTR showed that 15 (50%) were identified as 1a and 15 (50%) were identified as 1b. Sequence analysis of the NS5B revealed that 13 (43%) belonged to subtype 1a while 17 (57%) belonged to subtype 1b. The most predominant subtype was 1b by NS5B sequencing. The predictive value of 5′UTR sequencing to subtype 1a was 73% while for subtype 1b, predictive value was 87%. Overall concordance between 5′UTR and NS5B sequencing was 80%. NS5B sequence and phylogenetic analysis is still the reference method for identifying HCV-1a and 1b subtypes.

Development of hepatitis C virus production reporter-assay systems using two different hepatoma cell lines.

Abstract: A hepatitis C virus (HCV) infection system was developed previously using the HCV JFH-1 strain (genotype 2a) and HuH-7 cells, and this cell culture is so far the only robust production system for HCV. In patients with chronic hepatitis C, the virological effects of pegylated interferon and ribavirin therapy differ depending on the HCV strain and the genetic background of the host. Recently, we reported the hepatoma-derived Li23 cell line, in which the JFH-1 life cycle is reproduced at a level almost equal to that in HuH-7-derived RSc cells. To monitor the HCV life cycle more easily, we here developed JFH-1 reporter-assay systems using both HuH-7- and Li23-derived cell lines. To identify any genetic mutations by long-term cell culture, HCV RNAs in HuH-7 cells were amplified 130 days after infection and subjected to sequence analysis to find adaptive mutation(s) for robust virus replication. We identified two mutations, H2505Q and V2995L, in the NS5B region. V2995L but not H2505Q enhanced JFH-1 RNA replication. However, we found that H2505Q but not V2995L enhanced HCV RNA replication of strain O (genotype 1b). We also selected highly permissive D7 cells by serial subcloning of Li23 cells. The expression levels of claudin-1 and Niemann-Pick C1-like 1 in D7 cells are higher than those in parental Li23 cells. In this study, we developed HCV JFH-1 reporter-assay systems using two distinct hepatoma cell lines, HuH-7 and Li23. The mutations in NS5B resulted in different effects on strains O and JFH-1 HCV RNA replication.