Phenotypic analysis of mutations at residue 146 provides insights into the relationship between NS5A hyperphosphorylation and hepatitis C virus genome replication

Simultaneous Hepatitis C Virus Genotyping and Variant Detection in Patients with Thalassemia: A Single-Center Phylogenetic Study

BACKGROUND: Hepatitis C virus (HCV) genotype distribution is different in various regions. A variety of strategies could be used to detect HCV genotypes and subtypes. The aim of the present study was to introduce a genotyping method by an in-house protocol that could be used to determine HCV drug-resistant variants and phylogeny studies. METHODS: Samples from 91 patients with thalassemia were used for HCV genotyping by Cobas 4800 platform, and 50 cases of 1a, 1b, and 3a genotypes underwent amplification and sequencing of NS5A and NS5B by using consensus primers via conventional reverse transcription-polymerase chain reaction (RT-PCR) method. An ABI 3730xl system used for direct sequencing. Raw sequences were analyzed by popular bioinformatics software MEGA6 and CLC workbench 5. Phylogenetic construction was drawn using 1000 replicates bootstrap by the neighbor-joining method. Multiple sequence alignment (MSA) was performed for mutation detection. RESULTS: Sequencing results of 50 HCV isolates subtypes 1a (31/45), 3a (15/22) and 1b (4/8) NS5A and NS5B genes showed there were 72 NS5A and 105 NS5B mutations. Moreover, 8 resistant associated substitutions (RASs) were identified in nine thalassemia cases by multiple sequence alignment (MSA) protein analysis. The phylogenetic tree construct drew confirmed by the Cobas HCV genotyping results. CONCLUSION: The phylogenetic analysis could be a useful tool for HCV genotyping in case of determining the drug-resistant substitutions; however, it is time-consuming and needs expert analysis and interpretation. This preliminary study in Iranian patients with thalassemia introduces specific conventional RT-PCR to find RASs to direct acting antivirals (DAAs) and subtype determination at the same time.

Hepatitis C Viral Replication Complex

The life cycle of the hepatitis C virus (HCV) can be divided into several stages, including viral entry, protein translation, RNA replication, viral assembly, and release. HCV genomic RNA replication occurs in the replication organelles (RO) and is tightly linked to ER membrane alterations containing replication complexes (proteins NS3 to NS5B). The amplification of HCV genomic RNA could be regulated by the RO biogenesis, the viral RNA structure (i.e., cis-acting replication elements), and both viral and cellular proteins. Studies on HCV replication have led to the development of direct-acting antivirals (DAAs) targeting the replication complex. This review article summarizes the viral and cellular factors involved in regulating HCV genomic RNA replication and the DAAs that inhibit HCV replication.

HCV-2a NS5A downregulates viral translation predominantly through domain I

Hepatitis C virus (HCV) non-structural protein NS5A is a multifunctional protein with critical roles in viral replication and assembly. We previously showed that HCV-1b NS5A downregulates viral translation only in the presence of the poly(U/UC) tract in 3'UTR. As NS5A of different HCV genotypes may have different functions or carry out the same functions through genotype-specific mechanisms, we investigated the effect of HCV-2a NS5A on viral translation. We found that HCV-2a NS5A downregulates RNA translation of both HCV-2a and -1b, whereas the effect of HCV-1b NS5A is limited to HCV-1b only. In addition, individual regions of 3'UTR are not required for HCV-2a NS5A to downregulate viral RNA translation. We also found that HCV-2a NS5A inhibits capped mRNA translation. Mapping experiments showed that the translation downregulation by HCV-2a NS5A is predominantly mediated by domain I. Furthermore, we found that the integrity of serine-146 residue plays an important role in translation downregulation by NS5A. Our results increased our understanding on genotype-specific functions of HCV NS5A.