Recent advances in small-molecule inhibitors targeting influenza virus RNA-dependent RNA polymerase / 药学学报

Influenza virus causes serious threat to human life and health. Due to the inherent high variability of influenza virus, clinically resistant mutant strains of currently approved anti-influenza virus drugs have emerged. Therefore, it is urgent to develop antiviral drugs with new targets or mechanisms of action. RNA-dependent RNA polymerase is directly responsible for viral RNA transcription and replication, and plays key roles in the viral life cycle, which is considered an important target of anti-influenza drug design. From the point of view of medicinal chemistry, this review summarizes current advances in diverse small-molecule inhibitors targeting influenza virus RNA-dependent RNA polymerase, hoping to provide valuable reference for development of novel antiviral drugs.

Research progress in flavivirus non-structural protein 5 / 军事医学

The non-structural protein 5(NS5)is a highly conserved protein in the Flavivirus genus,acting as both a methyltransferase(MTase)and an RNA-dependent RNA polymerase(RdRp).It has been well documented that NS5 plays a crucial role in the replication of viral RNA.Recent studies have shown that NS5 proteins from different flaviviruses interact with various proteins in host cells,aiding the virus in evading the immune system.This review summarizes the structure,subcellular localization,and function of NS5 proteins.Additionally,we outline how flavivirus NS5 proteins contribute to viral replication and immune evasion.Lastly,we present the recent developments of specific small molecule inhibitors that target NS5 proteins.

Synthesis and anti-SARS-CoV-2 activity and mechanism research of lycorine derivatives / 药学学报

We designed and synthesized eighteen lycorine derivatives with five different structural types, and evaluated their antiviral activities on a HCoV-OC43-infected H460 cell model. Structure-activity relationships suggested that the introduction of appropriate substituents on the 6N atom of lycorine was beneficial to activity. Compound 6a gave a good activity with the half effective concentration (EC50) and selectivity index (SI) values of 2.36 μmol·L-1 and 16.52, respectively. Surface plasmon resonance (SPR) result indicated that 6a might target the non-structural protein 12 (NSP12) subunit in RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 with the dissociation constant (KD) value of 1.36 μmol·L-1. Molecular docking indicated that 6a might act on nidovirus RdRp-associated nucleotidyltransferase (NiRAN) catalytic center of NSP12, distinct from the mechanism of nucleoside-like drugs such as remdesivir. This study provides scientific data for the development of lycorine derivatives into a new class of anti-SARS-CoV-2 small molecule inhibitors.

Replication priority of hepatitis C virus genotype 2a in a Chinese cohort

HCV genotypes have been documented in clinical practice. The aim of this study was to determine the replication priority of different HCV genotypes in a Chinese HCV positive cohort. Serum samples from 491 apparently healthy Chinese blood donors testing positive for HCV antibodies and naive to antiviral drug therapy were tested. Genotyping analysis showed that genotypes 1b and 2a were predominant and accounted for 77.6% of the HCV infections. Among the genotype groups, individuals infected with genotype 2a had an HCV RNA viral load (10(8) copies/mL) about 200-fold (lg, 2.3) greater than those infected with other genotypes (10(4)-10(5) copies/mL) indicating a replication priority of genotype 2a. However, there was no correlation between HCV genotype and antibody response suggesting that the amplification advantage of genotype 2a results from a favorable interaction with the host cellular environment. In conclusion, HCV genotypes 1b and 2a are the predominant genotypes in China and genotype 2a possesses a significant replication priority compared with the other genotypes. This suggests the existence of host cellular factors that may act as drug-targets for entirely clearing HCV infection in the future.

Efeitos do análogo triazólico da Ribavirina, PAR038, sobre a replicação in vitro do vírus influenza / Effects of a ribavirin triazolic analogue, PAR038, in the in vitro replication of influenza virus

Os vírus influenza representam uma das principais causas das infecções respiratórias agudas, e são de grande impacto para saúde pública devido a ocorrência de epidemias sazonais e pandemias. A variabilidade genética deste vírus e seu amplo espectro de hospedeiros dificulta o controle das infecções através da vacinação, o que torna os antivirais importantes na prevenção e tratamento. Até o presente momento, existem duas classes de antivirais disponíveis para o tratamento da infecção pelo vírus influenza, os bloqueadores de canal M2 (amandadina e rimantadina), que não são mais utilizados clinicamente pois as cepas circulantes são resistentes e os inibidores de neuraminidase (NAIs – oseltamivir e zanamivir), classe em uso clínico embora já tenham sido descritas cepas resistentes ao oseltamivir. Existe também a ribavirina, um antiviral de amplo espectro que inibe DNA/RNA polimerases virais mas é altamente citotóxico. Devido ao número limitado de drogas anti-influenza, vem sendo realizados estudos sobre a eficácia da ribavirina e sua combinação com NAIs para tratamento das infecções causadas pelo influenza. A RNA polimerase do vírus influenza vem sendo cada vez mais explorada como alvo para novas drogas, e, desta forma, o objetivo deste trabalho foi investigar o efeito antiviral do PAR038, um análogo triazólico da ribavirina como potencial inibidor da polimerase. O composto PAR038 se mostrou menos citotóxico para células MDCK e 400 vezes mais potente que a ribavirina, com CC50 > 1000 miM e IC50 = 0,07 miM. Nosso composto foi capaz de inibir a RNA polimerase do vírus influenza com EC50 igual a 1,6 +/- 0.15 miM, além de inibir a replicação viral em células A549 (IC50 = 21,2 miM) e apresentar propriedades imunomodulatórias, já que diminuiu os níveis de IL-8 e MCP-1 no sobrenadante das células A549 infectadas com o vírus influenza...

Influenza virus represents one of the main causes of acute respiratory infections, beinga major cause of mortality, morbidity and burden to public health system. The geneticvariability of influenza viruses and broad spectrum of these viruses` hosts impose difficultiesin control strategies through vaccination. Therefore, antiviral drugs have become critical in theprevention and treatment of the infections caused by influenza viruses. There are two classesof anti-influenza drugs, M2 channel blockers (amantadine and rimantadine), which are nolonger used since circulating strains are resistant to these antivirals, and neuraminidaseinhibitors (NAIs – oseltamivir and zanamivir), in clinical use. Despite that, oseltamivirresistantstrains have been described. An additional antiviral, ribavirin, is endowed with abroad spectrum activity against DNA/RNA polymerases, although high cytotoxic has beendescribed. Due to the limited number of anti-influenza drugs, studies have been carried out onthe effectiveness of ribavirin and its combination with NAIs for treating influenza infections.Thus, influenza RNA polymerase still is a valid target for development of novel antiviral.Based on that, we aimed here to investigate the antiviral effect of PAR038, a triazolicanalogue of ribavirin. PAR038 is 400-fold potent than ribavirin, with CC50 > 1000 µM andIC50 = 0,07 µM towards MDCKs cytotoxicity and influenza in vitro replication. Ourcompound inhibits influenza RNA polymerase with an EC50 of 1,6 ± 0,15 µM and alsoinhibits viral replication in an A549 cells (IC50 = 21,2 µM)...

Expression and Antibody Production of Japanese Encephalitis Virus RNA Polymerase (NS5) Protein

Japanese encephalitis virus (JEV), a member of mosquito-borne flaviviruses, is the leading cause of viral encephalitis in a large geographic area of Southeast Asia and Australia. JEV contains a single-stranded positive-sense RNA genome, which encodes its own RNA-dependent RNA polymerase (NS5) that is required for genomic RNA replication. In this study, we have described a pair of mouse antisera specific to the N- or C-terminal region of the NS5. Initially, two hydrophilic regions corresponding to the N-terminus and C-terminus of the NS5 protein were individually amplified by reverse transcription-PCR from the genomic RNA of JEV K87P39 strain. The amplified DNA fragments were cloned into a prokaryotic expression vector, pGEX-4T-1; the resulting constructs were used for the expression of GST fusion proteins, designated GST/NS5N and GST/NS5C, in E. coli BL-21 strain. Following immunization of three BALB/c mice with each of the purified GST/NS5N and GST/NS5C, we obtained two pools of the antisera, specifically recognizing the ~103-kDa NS5 and several smaller NS5-related proteins in BHK-21 and Vero cells infected with JEV K87P39 strain. Overall, we have successfully expressed the N- and C-terminal regions of JEV NS5 fused to the C-terminus of GST and generated the mouse antisera capable of recognizing the NS5 and its related proteins in JEV-infected cells. This would provide a valuable reagent for the study of JEV NS5 in the viral life cycle.

Sequence Analysis of Small Round Structured Viruses (SRSV) Isolated from a Diarrheal Patient in Wonju

No abstract available.

Norwalk-Like Viruses, A Common Cause of Sporadic Acute Gastroenteritis in korean Children

Norwalk-like virus (NLV), one of the emerging enteric pathogens in sporadic cases and outbreaks of acute gastroenteritis (AG) worldwide, are 30-35 nm in diameter and have a single stranded RNA genome, size 7.6 kb. As genomic sequence data from several isolates of NLVs are being reported, the genetic relationships among these viruses are now being described. Based on the level of sequence similarity in the RNA polymerase region of NLVs, at least three genogroups can be defined: the Norwalk virus (NV)-, the Snow Mountain agent (SMA)-, and the Sapporo-genogroups. A high prevalence of serum antibody to NV-related viruses but no antigenpositve stools (either observed to contain the NLV by immune electron microscopy or suspected of containing the NLV) has suggested that genomically different NLVs are present among Korean children. The purpose of our work therefore was to detect NLVs from Korean infants and children with AG and to characterize the partial genome (RNA-dependent RNA polymerase region) of currently circulating Korean isolates. The cDNA fragments of 110 to 470 bp corresponding to the RNA polymerase region were generated by reverase transcription-polymerase chain reaction (RT-PCR) using three primer pairs (36/35, 36/51, or 36/101) derived from the prototype NV (8FIIaNV/68/US). Of 279 stool samples tested, 25 (9%) specimens were positive by RT-PCR and the amplified productscontained GLPSG and YGDD amino acid motifs, characteristic of positive-strand RNA-dependent RNA polymerases, at the predicted distance from the primers. In 6% of the infectious episodes with diarrhea, NLVs appeared to be the sole pathogen. Double infections occurred mainly with rotavirus and triple infections occured with both rotavirus and adenovirus or with both rotavirus and astrovirus. This study indicates that NLVs are a common cause of sporadic AG in Korean infants.