As health care providers, we find ourselves on the verge of a new era in the treatment of chronic hepatitis C virus (HCV) infection. A number of directly acting antiviral agents are now in the latter stages of clinical development. The more promising candidates include direct inhibitors of the HCV nonstructural 3 protease, as well as both nucleoside and non-nucleoside inhibitors of the NS5B RNA-dependent RNA polymerase. Although these agents have demonstrated potent antiviral effect, monotherapy has been complicated by rapid virological breakthrough due to the selection of drug-resistant mutants. As for HIV and HBV, combination therapy will therefore be necessary. This brief review summarizes the current literature concerning resistance and directly acting antiviral agents, and identifies key challenges facing this emerging field.
"In humans, induction of TLR2 signalling leads to an antihuman cytomegalovirus (HCMV) effect in ectocervical tissues via the induction of IFNβ (Harwani et al., 2007). It has also been shown that TLR2 ligands induce antiviral response against hepatitis B virus in vitro (Thompson and McHutchison, 2009; Zhang et al., 2012). In mice, TLR2 activation also significantly contributes to the control of murine cytomegalovirus infection in vivo in an NK cell-dependent way (Szomolanyi-Tsuda et al., 2006). "
[Show abstract][Hide abstract] ABSTRACT: Lipoteichoic acid (LTA) is one of the pathogen associated molecular patterns (PAMPs) that activate toll-like receptor (TLR)2-cluster of differentiation (CD)14 signalling pathway. This recognition elicits antiviral responses that has been recorded against viruses of mammals although such responses have not been characterized adequately against avian viruses. In this investigation, we characterized the LTA induced antiviral responses against infectious laryntotracheitis virus (ILTV) infection in vitro and in vivo. We found that LTA is capable of up regulating mRNA expression of innate proteins in macrophages such as MyD88, iNOS and IL-1β and reduces the ILTV plaques in vitro. Similarly, we found that LTA treatment of embryonic day 18 (ED18) eggs can lead to the antiviral response against pre-hatch ILTV infection in vivo and is associated with expansion of macrophage populations and expression of IL-1β and MyD88 in the lung. The data highlight that LTA can be a potential innate immune stimulant that can be used against ILTV infection in chickens.
"Telaprevir and boceprevir, as peptidomimetic inhibitors of the HCV NS3/4A protease, have been approved for hepatitis C patients by US FDA. But these drugs have proved to cause drug-resistance in clinic –. Hence, discovery and development of novel anti-HCV agents continues to be an urgent need. "
[Show abstract][Hide abstract] ABSTRACT: The lack of small animal models for hepatitis C virus has impeded the discovery and development of anti-HCV drugs. HCV-IRES plays an important role in HCV gene expression, and is an attractive target for antiviral therapy. In this study, we report a zebrafish model with a biscistron expression construct that can co-transcribe GFP and HCV-core genes by human hepatic lipase promoter and zebrafish liver fatty acid binding protein enhancer. HCV core translation was designed mediated by HCV-IRES sequence and gfp was by a canonical cap-dependent mechanism. Results of fluorescence image and hybridization indicate that expression of HCV core and GFP is liver-specific; RT-PCR and Western blotting show that both core and gfp expression are elevated in a time-dependent manner for both transcription and translation. It means that the HCV-IRES exerted its role in this zebrafish model. Furthermore, the liver-pathological impact associated with HCV-infection was detected by examination of gene markers and some of them were elevated, such as adiponectin receptor, heparanase, TGF-β, PDGF-α, etc. The model was used to evaluate three clinical drugs, ribavirin, IFNα-2b and vitamin B12. The results show that vitamin B12 inhibited core expression in mRNA and protein levels in dose-dependent manner, but failed to impact gfp expression. Also VB12 down-regulated some gene transcriptions involved in fat liver, liver fibrosis and HCV-associated pathological process in the larvae. It reveals that HCV-IRES responds to vitamin B12 sensitively in the zebrafish model. Ribavirin did not disturb core expression, hinting that HCV-IRES is not a target site of ribavirin. IFNα-2b was not active, which maybe resulted from its degradation in vivo for the long time. These findings demonstrate the feasibility of the zebrafish model for screening of anti-HCV drugs targeting to HCV-IRES. The zebrafish system provides a novel evidence of using zebrafish as a HCV model organism.
PLoS ONE 03/2013; 8(3):e56985. DOI:10.1371/journal.pone.0056985 · 3.23 Impact Factor
"The high HCV replication rate and lack of a proof-reading mechanism determine a natural variability, which promotes the rapid emergence of drug-resistant variants . Natural aa changes in NS3 associated with reduced drug susceptibility have been observed in treatment naïve patients [10,16,17]. "
[Show abstract][Hide abstract] ABSTRACT: Background
Protease inhibitors (PIs) to treat hepatitis C (HCV) virus infection have been approved and others are under development.
The aims of this study were to illustrate natural polymorphisms in the HCV protease and measure the frequency of PI resistance mutations in different HCV genotypes from PI-naïve patients.
Direct sequencing of HCV NS3/4A protease was performed in 156 HCV patients naïve to PIs who were infected with genotype 1a (n = 31), 1b (n = 39), 2 (n = 30), 3 (n = 33) and 4 (n = 23).
Amino acid (aa) substitutions associated with HCV PI resistance were found in 17/156 (10.8%) sequences. Mutations V36L, T54S, V55A/I, and Q80K/L were observed in 29% of patients with genotype 1a, and V55F, Q80L/N and M175L in 10% of patients with genotype 1b. The mutation V158M was found in 3% of patients with genotype 2, D168Q was present in 100% of patients with genotype 3 and D168E was observed in 13% of patients with genotype 4. In addition, multiple aa polymorphisms not associated with PI resistance were detected in patients with genotypes 1a, 1b and 4.
Although major PI resistance mutations were not detected, other resistance mutations conferring low level resistance to PIs together with a number of natural polymorphisms were observed in proteases of PI naïve HCV patients. A more extensive analysis is needed to better evaluate the impact of baseline resistance and compensatory mutations in the efficacy of HCV PI treatment.
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