Mechanisms of antiviral treatment efficacy and failure in chronic hepatitis C

Hepatitis C Virus Genotype 5 Variability in Treatment-Naïve Patients in South Africa

INTRODUCTION

Hepatitis C virus (HCV) genotype 5 was originally identified in South Africa, where it represents 35-60% of all HCV infections. There are limited data on resistance-associated variants (RAVs) in South Africa. Thus, we investigated variability within the NS3/NS4A, NS5A, and NS5B genes of treatment-naïve individuals with HCV genotype 5 infection at the Dr. George Mukhari Academic Hospital (DGMAH) in Pretoria, South Africa.

METHODS

Nested PCR was performed to amplify the NS3/4A, NS5A, and NS5B genes. RAVs were evaluated using the Geno2pheno tool.

RESULTS

In the NS3/4A gene, F56S and T122A were detected in one sample each. The D168E mutation was detected in 7 samples. Within the NS5A gene, the T62M mutation was detected in 2 individuals. In the NS5B gene, 8 of 12 individuals (67%) had the A421V mutation, while all 12 individuals (100%) had the S486A mutation.

DISCUSSION

RAVs were detected frequently among treatment-naïve individuals with HCV genotype 5 infection in South Africa. Thus, resistance testing may be prudent when initiating treatment of patients with genotype 5 infection. Additional population-based studies are needed to understand the prevalence of these RAVs during HCV genotype 5 infection.

Inhibitors of Nucleotide Biosynthesis as Candidates for a Wide Spectrum of Antiviral Chemotherapy

Emerging and re-emerging viruses have been a challenge in public health in recent decades. Host-targeted antivirals (HTA) directed at cellular molecules or pathways involved in virus multiplication represent an interesting strategy to combat viruses presently lacking effective chemotherapy. HTA could provide a wide range of agents with inhibitory activity against current and future viruses that share similar host requirements and reduce the possible selection of antiviral-resistant variants. Nucleotide metabolism is one of the more exploited host metabolic pathways as a potential antiviral target for several human viruses. This review focuses on the antiviral properties of the inhibitors of pyrimidine and purine nucleotide biosynthesis, with an emphasis on the rate-limiting enzymes dihydroorotate dehydrogenase (DHODH) and inosine monophosphate dehydrogenase (IMPDH) for which there are old and new drugs active against a broad spectrum of pathogenic viruses.

Hepatitis C virus treatment failure: Clinical utility for testing resistance-associated substitutions

The hepatitis C virus has a high mutation capacity that leads to the emergence of resistance-associated substitutions (RAS). However, the consequence of resistance selection during new direct-acting antiviral drug (DAA) treatment is not necessarily the therapeutic failure. In fact, DAA treatment has shown a high rate (> 95%) of sustained virological response even when high baseline RAS prevalence has been reported. In the context of RAS emergence and high rates of sustained viral response, the clinical relevance of variants harboring RAS is still controversial. Therefore, in order to summarize the data available in international guidelines, we have reviewed the clinical utility of testing RAS in the era of new pangenotypic DAA drugs.

Diversity of the hepatitis C virus NS5B gene during HIV co-infection

Viral diversity is an important feature of hepatitis C virus (HCV) infection and an important predictor of disease progression and treatment response. HIV/HCV co-infection is associated with enhanced HCV replication, increased fibrosis, and the development of liver disease. HIV also increases quasispecies diversity of HCV structural genes, although limited data are available regarding the impact of HIV on non-structural genes of HCV, particularly in the absence of direct-acting therapies. The genetic diversity and presence of drug resistance mutations within the RNA-dependent RNA polymerase (NS5B) gene were examined in 3 groups of women with HCV genotype 1a infection, including those with HCV mono-infection, antiretroviral (ART)-naïve women with HIV/HCV co-infection and CD4 cell count <350 cells/mm3, and ART-naïve women with HIV/HCV co-infection and CD4 cell count ≥350 cells/mm3. None had ever been treated for HCV infection. There was evidence of significant diversity across the entire NS5B gene in all women. There were several nucleotides and amino acids with distinct distributions across the three study groups, although no obvious clustering of NS5B sequences was observed based on HIV co-infection or CD4 cell count. Polymorphisms at amino acid positions associated with resistance to dasabuvir and sofosbuvir were limited, although the Q309R variant associated with ribavirin resistance was present in 12 individuals with HCV mono-infection, 8 HIV/HCV co-infected individuals with CD4 <350 cells/mm3, and 12 HIV/HCV co-infected individuals with CD4 ≥350 cells/mm3. Previously reported fitness altering mutations were rare. CD8+ T cell responses against the human leukocyte antigen (HLA) B57-restricted epitopes NS5B2629-2637 and NS5B2936-2944 are critical for HCV control and were completely conserved in 44 (51.8%) and 70 (82.4%) study participants. These data demonstrate extensive variation across the NS5B gene. Genotypic variation may have a profound impact on HCV replication and pathogenesis and deserves careful evaluation.

IL-15 and IFN-γ signal through the ERK pathway to inhibit HCV replication, independent of type I IFN signaling

Despite effective new treatments for Hepatitis C virus (HCV) infection, development of drug resistance, safety concerns and cost are remaining challenges. More importantly, there is no vaccine available against hepatitis C infection. Recent data suggest that there is a strong correlation between spontaneous HCV clearance and human NK cell function, particularly IFN-γ production. Further, IL-15 has innate antiviral activity and is also one of the main factors that activates NK cells to produce IFN-γ. To examine whether IL-15 and IFN-γ have direct antiviral activity against HCV, Huh7.5 cells were treated with either IFN-γ or IL-15 prior to HCV infection. Our data demonstrate that IFN-γ and IL-15 block HCV replication in vitro. Additionally, we show that IL-15 and IFN-γ do not induce anti-HCV effects through the type I interferon signaling pathway or nitric oxide (NO) production. Instead, IL-15 and IFN-γ provide protection against HCV via the ERK pathway. Treatment of Huh7.5 cells with a MEK/ERK inhibitor abrogated the anti-HCV effects of IL-15 and IFN-γ and overexpression of ERK1 prevented HCV replication compared to control transfection. Our in vitro data support the hypothesis that early production of IL-15 and activation of NK cells in the liver lead to control of HCV replication.

Global dynamics of a viral infection model with full logistic terms and antivirus treatments

In this paper, mathematical analysis of the global dynamics of a viral infection model in vivo is carried out. Though the model is originally to study hepatitis C virus (HCV) dynamics in patients with high baseline viral loads or advanced liver disease, similar models still hold significance for other viral infection, such as hepatitis B virus (HBV) or human immunodeficiency virus (HIV) infection. By means of Volterra-type Lyapunov functions, we know that the basic reproduction number [Formula: see text] is a sharp threshold para-meter for the outcomes of viral infections. If [Formula: see text], the virus-free equilibrium is globally asymptotically stable. If [Formula: see text], the system is uniformly persistent, the unique endemic equilibrium appears and is globally asymptotically stable under a sufficient condition. Other than that, for the global stability of the unique endemic equilibrium, another sufficient condition is obtained by Li–Muldowney global-stability criterion. Using numerical simulation techniques, we further find that sustained oscillations can exist and different maximum de novo hepatocyte influx rate can induce different global dynamics along with the change of overall drug effectiveness. Finally, some biological implications of our findings are given.

Mutagenic Effects of Ribavirin on Hepatitis E Virus-Viral Extinction versus Selection of Fitness-Enhancing Mutations

Hepatitis E virus (HEV), an important agent of viral hepatitis worldwide, can cause severe courses of infection in pregnant women and immunosuppressed patients. To date, HEV infections can only be treated with ribavirin (RBV). Major drawbacks of this therapy are that RBV is not approved for administration to pregnant women and that the virus can acquire mutations, which render the intra-host population less sensitive or even resistant to RBV. One of the proposed modes of action of RBV is a direct mutagenic effect on viral genomes, inducing mismatches and subsequent nucleotide substitutions. These transition events can drive the already error-prone viral replication beyond an error threshold, causing viral population extinction. In contrast, the expanded heterogeneous viral population can facilitate selection of mutant viruses with enhanced replication fitness. Emergence of these mutant viruses can lead to therapeutic failure. Consequently, the onset of RBV treatment in chronically HEV-infected individuals can result in two divergent outcomes: viral extinction versus selection of fitness-enhanced viruses. Following an overview of RNA viruses treated with RBV in clinics and a summary of the different antiviral modes of action of this drug, we focus on the mutagenic effect of RBV on HEV intrahost populations, and how HEV is able to overcome lethal mutagenesis.

Hepatitis C Genotype Prevalence in Monastir Region, Tunisia: Correlation between 5' Untranslated Region (5'UTR), Non-structural 5B (NS5B), and Core Sequences in HCV Subtyping

Hepatitis C virus (HCV) is a causative agent of chronic liver disease, cirrhosis, and hepatocellular carcinoma. It constitutes a major public health around the world. There is no vaccine available against HCV, and current therapies are effective in only small percentage of patients. HCV has wide population-specific genotype variability. Genotype knowledge and viral load assessment are equally important for designing therapeutic strategies. Taking into account that the molecular epidemiology of HCV variants circulating in Tunisia is not yet well elucidated, and that, at present, little is known about the distribution pattern of HCV in Monastir region (Tunisia), we aimed, herein, to evaluate the prevalence of HCV genotypes in Monastir and to identify risk-related factors. For this purpose, 50 anti-HCV antibody-positive cases were diagnosed and subjected to viral RNA extraction, amplification, genotyping, and viral load quantification. Molecular epidemiology was studied by 5' untranslated region (5' UTR) sequencing as compared with the non-structural 5B (NS5B) and core region sequences. Overall concordance between 5' UTR, core, and NS5B sequencing was 100 %. The highest prevalent genotype was 1b (50 %) followed by genotypes 1a (16 %), 4a (12 %), 2a (10 %), 2c (8 %), and 3a (4 %). Interestingly, the subtype 1b had a statistically significant higher viral load than the other genotypes followed by subtype 1a. Based on these data, this study revealed a high prevalence of HCV genotype 1 (subtypes 1b and 1a) compared to other genotypes. A continued monitoring of HCV and knowledge of circulating genotypes could impact on future vaccine formulations.

The role of HCV proteins on treatment outcomes

For many years, the standard of treatment for hepatitis C virus (HCV) infection was a combination of pegylated interferon alpha (Peg-IFN-α) and ribavirin for 24–48 weeks. This treatment regimen results in a sustained virologic response (SVR) rate in about 50 % of cases. The failure of IFN-α-based therapy to eliminate HCV is a result of multiple factors including a suboptimal treatment regimen, severity of HCV-related diseases, host factors and viral factors. In recent years, advances in HCV cell culture have contributed to a better understanding of the viral life cycle, which has led to the development of a number of direct-acting antiviral agents (DAAs) that target specific key components of viral replication, such as HCV NS3/4A, HCV NS5A, and HCV NS5B proteins. To date, several new drugs have been approved for the treatment of HCV infection. Application of DAAs with IFN-based or IFN-free regimens has increased the SVR rate up to >90 % and has allowed treatment duration to be shortened to 12–24 weeks. The impact of HCV proteins in response to IFN-based and IFN-free therapies has been described in many reports. This review summarizes and updates knowledge on molecular mechanisms of HCV proteins involved in anti-IFN activity as well as examining amino acid variations and mutations in several regions of HCV proteins associated with the response to IFN-based therapy and pattern of resistance associated amino acid variants (RAV) to antiviral agents.

Los alamos hepatitis C immunology database

The Los Alamos Hepatitis C Virus (HCV) Sequence Database (http://hcv.lanl.gov or http://hcv-db.org) was officially launched in September 2003. The sister HCV Immunology Database was made public in September 2004. The HCV Immunology Database is based on the Human Immunodeficiency Virus (HIV) Immunology Database. The HCV Immunology Database contains a curated inventory of immunological epitopes in HCV and their interaction with the immune system, with associated retrieval and analysis tools. This article describes in detail the types of data and services that the new database offers, the tools provided and the database framework. The data and some of the HCV database tools are available for download for non-commercial use.

Correlation Study Between HCV Genotypes Distribution Pattern and Viral Load in a Tertiary Care Hospital in Kolkata, India

BACKGROUND

Hepatitis C virus infection is a leading cause for chronic liver disease. It has wide population specific genotype variability. Genotype knowledge and viral load assessment are equally important for designing therapeutic strategies and as predictors of treatment outcome among hepatitis C (HCV) infected patients.

MATERIALS AND METHODS

Between June 2012 and 2013 an observational study was conducted among 350 chronic hepatitis patients visiting Calcutta National Medical College, Kolkata, India. Among them, 110 anti-HCV antibody positive cases were diagnosed and subjected to viral RNA extraction, viral genotyping and viral load quantification using polymerase chain reaction (PCR) based techniques.

STATISTICAL ANALYSIS

Statistical analysis was done with IBM SPSS Statistics software, version 20. p-value <0.05 was regarded as statically significant.

RESULTS

Among 66 HCV RNA positive cases, genotypes 1a, 3a and 3b were observed among 18 (27%), 44(67%) and 4(6%) cases respectively. Genotype 3a had higher viral load than patients infected with genotypes 1and 3b. However, no statistical significance was observed for viral load among the various HCV RNA genotypes.

CONCLUSION

Genotype 3a accounted for the highest number of cases with positive HCV RNA. However, no statistically significant difference existed for viral load among the various HCV RNA genotypes in this study.

Oxidative stress response in patients infected by diverse hepatitis C virus genotypes

BACKGROUND

The molecular mechanism of hepatitis C-virus (HCV) genome-specific pathogenesis remains unclear. Oxidative stress is an important pathophysiological mechanism in chronic HCV infection, but its relation to HCV genotypes has not been thoroughly examined.

OBJECTIVES

In the present case-control study, the effect of diverse HCV genotypes on oxidative status changes was investigated.

PATIENTS AND METHODS

From 310 patients examined by enzyme immunoassay and PCR, 160 patients with positive results for HCV with previously determined genotypes were chosen. For the control group, 160 first time blood donors referred to the Regional Blood Transfusion organization of the West Azerbaijan province, northwestern Iran were selected. Oxidative stress markers such as total antioxidant status (TAS), serum levels of reduced (GSH) and oxidized (GSSG) glutathione, Gamma-glutamyl transferase (GGT) and malondialdehyde (MDA) were evaluated in patients infected with diverse HCV genotypes and those in the control group.

RESULTS

In the patient and control groups, the mean ± SE of TAS, GSH, GSSG, GGT and MDA were 1.04 ± 0.35 vs. 2.68 ± 0.77, 1.25 ± 0.37 vs. 3.12 ± 0.58, 0.20 ± 0.05 vs. 0.08 ± 0.04, 26.82 ± 5.62 vs 8.28 ± 2.03 and 2.56 ± 0.60 vs. 0.93 ± 0.34. All markers had statistical difference between the two groups (P <0.05). Obvious differences were found in oxidant/antioxidant balance among diverse HCV genotypes with an ascending trend in antioxidant levels among patients infected with genotypes 1a/b, 4, 2a/c, 2b, 3a and healthy controls and a vice versa trend in measures of oxidative markers except for malondialdehyde with a variable pattern.

CONCLUSIONS

More serious disease in HCV genetic subtype 1a/1b might be associated with more severe oxidative stress. Milder damage in subtypes 4, 2a/c, 2b and 3a could be related to lower oxidative response, respectively. A combination of antiviral and antioxidative therapies may enhance the overall response rate of patients with HCV infection, especially with more destructive genotypes.

Geographic distribution of hepatitis C virus genotypes in pakistan

BACKGROUND

Distribution of Hepatitis C Virus (HCV) genotypes may be changed over time. Epidemiological Studies on distribution patterns of HCV genotypes in Pakistani population might assist for better treatment options and preventive strategies.

OBJECTIVES

This study was conducted to determine distribution patterns of HCV genotypes in different geographical regions of Pakistan.

PATIENTS AND METHODS

In this cross-sectional study, 1818 randomly selected patients from different geographical regions of Pakistan, diagnosed with HCV infection by the third generation Enzyme Linked Immunosorbent Assay (ELISA), were included between April 2011 and December 2013. HCV RNA was detected in serum samples of patients by Reverse Transcription Polymerase Chain Reaction (RT- PCR) of the core region. Qualitative PCR was performed to determine viral load. HCV genotyping was performed by RT-nested PCR using type-specific primers of the core region. Frequency of different genotypes among patients was assessed according to gender, age and geographical region at the time of sampling.

RESULTS

Of 1818 HCV RNA positive samples, HCV genotypes PCR fragments were detected in 1552 (85.5%) samples. HCV genotype 3a was the predominant genotype (39.4%) followed by genotype 2a (24.93%). HCV genotype 3 was the predominant genotype in Punjab and Sindh regions, while genotype 2 was the most predominant genotype in Khyber Pakhtunkhwa region and the second predominant genotype after genotype 3 in Sindh region. The incidence of genotype 2a is increasing in our country with decrease in the incidence of genotype 3a. A higher incidence of HCV various genotypes were observed among male patients and those younger than 45 years.

CONCLUSIONS

This study may facilitate treatment options and preventive strategies in Pakistan.

Characterization of hepatitis C virus genotypes by direct sequencing of HCV 5'UTR region of isolates from Saudi Arabia

The current study was designed to determine the Hepatitis C Virus (HCV) genotypes in a representative sample of HCV chronically infected patients in Saudi Arabia. All HCV isolates were genotyped by sequencing of the 5′UTR region and newly identified HCV isolates were identified. Specific universal primers targeting 5′UTR region were used for both amplification and sequencing of all isolates that resulted in 244 bp fragment which represent about 80% of 5′UTR region. Most of HCV isolates in this study were genotype 4 (76.4%) where only few isolates were recognized as genotype 1 (19.6%). All results were compared to HCV reference sequences from LOS ALAMOS HCV database, considering only the complete full genomes for the main phylogenetic analysis. Sequences that showed maximum identity (98% –100%) were selected. Most isolates were identical with HCV genotype 4 references. Some isolates were similar to different subtypes of HCV genotypes 4, 1 and 6. Phylogenetic analysis showed resemblance of most isolates to similar ones from the Far East, North America and Egypt. Using sequence Weblogo, Alignment analysis of isolated HCV genotypes 4 and 1 showed 92% and 95.5% nucleotide conservation, respectively. There was no predominant nucleotide in the varied sites, in both genotypes. All isolated sequences were submitted to GenBank database.

Low IL10 serum levels as key factor for predicting the sustained virological response to IFNα/ribavirin in Brazilian patients with HCV carrying IL28B CT/TT genotype

PROPOSE

IL28B polymorphisms rs12979860 CC genotype was associated to protection of HCV infection and sustained virological response (SVR) in HCV infected patients treated with pegIFNα/ribavirin (IFNα/RIB), however, this polymorphism frequency varies depending on genetic components. Studies with larger number of Brazilian individuals, determining IL28B polymorphisms is lacking. Regarding to treatment response, the levels of IL10 seem to influence response to IFNα/RIB therapy. Thus, the IL28B polymorphism frequency was investigated in health controls and infected HCV patients, as well as, in patients who reach SVR vs Non-SVR. Also, to gain insight into the interplay between IL28B genotypes, IL10 levels and therapy response, a subgroup of genotyped HCV patients SVR and Non-SVR were analyzed regarding the IL10 production.

METHODS

It was enrolled 487 HCV infected patients and 234 healthy individuals. Patients with response to IFNα/RIB were classified as SVR (n = 81) and Non-SVR (n = 123). TAQMAN probes were used for genotyping the SNP rs12979860, resulting in CC, CT or TT genotypes. In one hundred one patients, the levels IL10 were measured at week 4 of IFNα/RIB.

RESULTS

CC genotype was associated to SVR (p = 0.029) and its frequency was higher in healthy individuals vs patients (p = 0.02). Patients carrying CT/TT with IL10<10 pg/mL, had a chance of 2.72 to achieve SVR in multivariate model (p = 0.043).

CONCLUSION

CC genotype was associated to SVR and protection to HCV infection. Moreover, IL28B genotyping and IL10 serum levels could be further explored as a useful algorithm for identify the CT/TT SVR patients.

HCV genome-wide genetic analyses in context of disease progression and hepatocellular carcinoma

Hepatitis C virus (HCV) is a major cause of hepatitis and hepatocellular carcinoma (HCC) world-wide. Most HCV patients have relatively stable disease, but approximately 25% have progressive disease that often terminates in liver failure or HCC. HCV is highly variable genetically, with seven genotypes and multiple subtypes per genotype. This variation affects HCV's sensitivity to antiviral therapy and has been implicated to contribute to differences in disease. We sequenced the complete viral coding capacity for 107 HCV genotype 1 isolates to determine whether genetic variation between independent HCV isolates is associated with the rate of disease progression or development of HCC. Consensus sequences were determined by sequencing RT-PCR products from serum or plasma. Positions of amino acid conservation, amino acid diversity patterns, selection pressures, and genome-wide patterns of amino acid covariance were assessed in context of the clinical phenotypes. A few positions were found where the amino acid distributions or degree of positive selection differed between in the HCC and cirrhotic sequences. All other assessments of viral genetic variation and HCC failed to yield significant associations. Sequences from patients with slow disease progression were under a greater degree of positive selection than sequences from rapid progressors, but all other analyses comparing HCV from rapid and slow disease progressors were statistically insignificant. The failure to observe distinct sequence differences associated with disease progression or HCC employing methods that previously revealed strong associations with the outcome of interferon α-based therapy implies that variable ability of HCV to modulate interferon responses is not a dominant cause for differential pathology among HCV patients. This lack of significant associations also implies that host and/or environmental factors are the major causes of differential disease presentation in HCV patients.

Genotyping of HCV RNA reveals that 3a is the most prevalent genotype in mardan, pakistan

The clinical outcomes of patients infected with hepatitis C virus (HCV) range from acute resolving hepatitis to chronic liver diseases such as liver cirrhosis or hepatocellular carcinoma. Identification of the infecting virus genotype is indispensable for the exploration of many aspects of HCV infection, including epidemiology, pathogenesis, and response to antiviral therapy. 1419 individuals were screened for anti-HCV in this study, of which 166 (11.7%) were found reactive by ICT (Immunochromatographic test). These 166 anti-HCV positive and 26 normal individuals were further analyzed. RNA was extracted from serum and reverse-transcribed to cDNA and the core region of HCV genome was targeted and amplified by multiplex PCR. HCV RNA was detected in 121 individuals, of which 87 were male and 34 were female. Genotype 3a was the most prevalent among all the genotypes observed followed by 3b. Genotypes 1a, 2a, and 2b were found in 10.89%, 13.22%, and 6.61% patients, respectively. 25.41% of the HCV RNA positive samples were not typed. 6.05% of patients were found having mixed genotypes. These findings will not only help the physicians to prescribe more appropriate treatment for the HCV infection but will also draw the attention of health-related policy makers to devise strategies to curb the disease more effectively.

New approaches to rapidly control foot-and-mouth disease outbreaks

Economically, foot-and-mouth disease is the most important viral-induced livestock disease worldwide. The disease is highly contagious and foot-and-mouth disease virus replicates and spreads extremely rapidly. Recent outbreaks in previously foot-and-mouth disease-free countries and the potential use of foot-and-mouth disease virus by terrorist groups have demonstrated the vulnerability of countries and the need to develop control strategies that can rapidly inhibit or limit spread of the disease. The current vaccine, an inactivated whole-virus preparation, has a number of limitations for use in outbreaks in disease-free countries. This review discusses the potential of the antiviral agent, Type I interferon, to produce rapid protection and proposes a combination strategy of an antiviral agent and a foot-and-mouth disease vaccine to induce both immediate and long-lasting protective responses.

Chutes and ladders in hepatitis C nucleoside drug development

Chutes and Ladders is an exciting up-and-down-again game in which players race to be the first to the top of the board. Along the way, they will find ladders to help them advance, and chutes that will cause them to move backwards. The development of nucleoside analogs for clinical treatment of hepatitis C presents a similar scenario in which taking shortcuts may help quickly advance a program, but there is always a tremendous risk of being sent backwards as one competes for the finish line. In recent years the treatment options for chronic hepatitis C virus (HCV) infection have expand due to the development of a replicon based in vitro evaluation system, allowing for the identification of multiple drugable viral targets along with a concerted and substantial drug discovery effort. Three major drug targets have reached clinical study for chronic HCV infection: the NS3/4A serine protease, the large phosphoprotein NS5A, and the NS5B RNA-dependent RNA polymerase. Recently, two oral HCV protease inhibitors were approved by the FDA and were the first direct acting anti-HCV agents to result from the substantial research in this area. There are currently many new chemical entities from several different target classes that are being evaluated worldwide in clinical trials for their effectiveness at achieving a sustained virologic response (SVR) (Pham et al., 2004; Radkowski et al., 2005). Clearly the goal is to develop therapies leading to a cure that are safe, widely accessible and available, and effective against all HCV genotypes (GT), and all stages of the disease. Nucleoside analogs that target the HCV NS5B polymerase that have reached human clinical trials is the focus of this review as they have demonstrated significant advantages in the clinic with broader activity against the various HCV GT and a higher barrier to the development of resistant viruses when compared to all other classes of HCV inhibitors.

The role of chemokines in acute and chronic hepatitis C infection

Hepatitis C imposes a significant burden on global healthcare. Chronic infection is associated with progressive inflammation of the liver which typically manifests in cirrhosis, organ failure and cancer. By virtue of elaborate evasion strategies, hepatitis C virus (HCV) succeeds as a persistent human virus. It has an extraordinary capacity to subvert the immune response enabling it to establish chronic infections and associated liver disease. Chemokines are low molecular weight chemotactic peptides that mediate the recruitment of inflammatory cells into tissues and back into the lymphatics and peripheral blood. Thus, they are central to the temporal and spatial distribution of effector and regulatory immune cells. The interactions between chemokines and their cognate receptors help shape the immune response and therefore, have a major influence on the outcome of infection. However, chemokines represent a target for modulation by viruses including the HCV. HCV is known to modulate chemokine expression in vitro and may therefore enable its survival by subverting the immune response in vivo through altered leukocyte chemotaxis resulting in impaired viral clearance and the establishment of chronic low-grade inflammation. In this review, the roles of chemokines in acute and chronic HCV infection are described with a particular emphasis placed on chemokine modulation as a means of immune subversion. We provide an in depth discussion of the part played by chemokines in mediating hepatic fibrosis while addressing the potential applications for these chemoattractants in prognostic medicine.

Analysis of HCV quasispecies dynamic under selective pressure of combined therapy

Background

The quasispecies composition of Hepatitis C virus (HCV) could have important implications with regard to viral persistence and response to interferon-based therapy. The complete NS5A was analyzed to evaluate whether the composition of NS5A quasispecies of HCV 1a/1b is related to responsiveness to combined interferon pegylated (PEG-IFN) and ribavirin therapy.

Methods

Viral RNA was isolated from serum samples collected before, during and after treatment from virological sustained responder (SVR), non-responder (NR) and the end-of-treatment responder patients (ETR). NS5A region was amplified, cloned and sequenced. Six hundred and ninety full-length NS5A sequences were analyzed.

Results

This study provides evidence that lower nucleotide diversity of the NS5A region pre-therapy is associated with viral clearance. Analysis of samples of NRs and the ETRs time points showed that genetic diversity of populations tend to decrease over time. Post-therapy population of ETRs presented higher genetic distance from baseline probably due to the bottleneck phenomenon observed for those patients in the end of treatment. The viral effective population of those patients also showed a strong decrease after therapy. Otherwise, NRs demonstrated a continuous variation or stability of effective populations and genetic diversity over time that did not seem to be related to therapy. Phylogenetic relationships concerning complete NS5A sequences obtained from patients did not demonstrate clustering associated with specific response patterns. However, distinctive clustering of pre/post-therapy sequences was observed. In addition, the evolution of quasispecies over time was subjected to purifying or relaxed purifying selection. Codons 157 (P03), 182 and 440 (P42), 62 and 404 (P44) were found to be under positive selective pressure but it failed to be related to the therapy.

Conclusion

These results confirm the hypothesis that a relationship exists between NS5A heterogeneity and response to therapy in patients infected with chronic hepatitis C.

Diversity of Hepatitis C virus in Southern India Based on 5'UTR Sequence

Hepatitis C virus (HCV) exhibits genotype-specific variations in geographical distribution as a consequence of drug and immune induced evolution. Present study was aimed at discerning the distribution and prevalence of the various genotypes and subtypes of HCV in southern India. The HCV positive patient's serum was collected from different hospitals and blood banks from the states of Kerala, Tamil Nadu, Andhra Pradesh and Karnataka. Among 114 HCV positive samples, we could find only 44 isolates that are found both positive in ELISA and RT-PCR. From these samples 5' untranslated region (5'UTR) were amplified, sequenced and sub typed. Analysis of 5'UTR region of the 44 isolates shows that, genotypes 1, 3, 4 and 6 are present with genotype 3 being the most frequent. The present study shows that HCV genotype 3 subtype B was the most prevalent, forming 47.7 % among the population in southern India. The present study urges for discovering novel therapeutic agents that should be specific to genotype 3 subtype B, for the management of HCV in southern India.

Hepatitis C virus genotype diversity in Shanghai, China

We studied 67 hepatitis C virus (HCV) isolates from 64 hospitalized patients in Shanghai, China. Genotype 1 was prevalent, and genotypes 2, 3, 6 were found for the first time in Shanghai. A rare mixed infection with three subtypes (1a, 1b, 2a) was found. The complete genome sequence of a subtype 3b isolate was determined and analyzed.

Distribution and molecular characterization of hepatitis C virus (HCV) genotypes in patients with chronic infection from Pernambuco State, Brazil

Hepatitis C virus (HCV) is a public health problem throughout the world and 3% of the world population is infected with this virus. It is estimated that 3-4 millions individuals are being infected every year. It has been estimated that around 1.5% of Brazilian population is anti-HCV positive and the Northeast region showed the highest prevalence in Brazil. The aim of this study was to characterize HCV genotypes circulating in Pernambuco State (PE), Brazil, located in the Northeast region of the country. This study included 85 anti-HCV positive patients followed up between 2004 and 2011. For genotyping, a 380bp fragment of HCV RNA in the NS5B region was amplified by nested PCR. Phylogenetic analysis was conducted using Bayesian Markov chain Monte Carlo simulation (MCMC) using BEAST v.1.5.3. From 85 samples, 63 (74.1%) positive to NS5B fragment were successfully sequenced. Subtype 1b was the most prevalent in this population (42-66.7%), followed by 3a (16-25.4%), 1a (4-6.3%) and 2b (1-1.6%). Twelve (63.1%) and seven (36.9%) patients with HCV and schistosomiasis were infected with subtypes 1b and 3a, respectively. Brazil is a large country with many different population backgrounds; a large variation in the frequencies of HCV genotypes is predictable throughout its territory. This study reports HCV genotypes from Pernambuco State where subtype 1b was found to be the most prevalent. Phylogenetic analysis suggests the presence of the different HCV strains circulating within this population.

Hepatitis C virus NS5A disrupts STAT1 phosphorylation and suppresses type I interferon signaling

Responses to alpha interferon (IFN-α)-based treatment are dependent on both host and viral factors and vary markedly among patients infected with different hepatitis C virus (HCV) genotypes (GTs). Patients infected with GT3 viruses consistently respond better to IFN treatment than do patients infected with GT1 viruses. The mechanisms underlying this difference are not well understood. In this study, we sought to determine the effects of HCV NS5A proteins from different genotypes on IFN signaling. We found that the overexpression of either GT1 or GT3 NS5A proteins significantly inhibited IFN-induced IFN-stimulated response element (ISRE) signaling, phosphorylated STAT1 (P-STAT1) levels, and IFN-stimulated gene (ISG) expression compared to controls. GT1 NS5A protein expression exhibited stronger inhibitory effects on IFN signaling than did GT3 NS5A protein expression. Furthermore, GT1 NS5A bound to STAT1 with a higher affinity than did GT3 NS5A. Domain mapping revealed that the C-terminal region of NS5A conferred these inhibitory effects on IFN signaling. The overexpression of HCV NS5A increased HCV replication levels in JFH1-infected cells through the further reduction of levels of P-STAT1, ISRE signaling, and downstream ISG responses. We demonstrated that the overexpression of GT1 NS5A proteins resulted in less IFN responsiveness than did the expression of GT3 NS5A proteins through stronger binding to STAT1. We confirmed that GT1 NS5A proteins exerted stronger IFN signaling inhibition than did GT3 NS5A proteins in an infectious recombinant JFH1 virus. The potent antiviral NS5A inhibitor BMS-790052 did not block NS5A-mediated IFN signaling suppression in an overexpression model, suggesting that NS5A's contributions to replication are independent of its subversive action on IFN. We propose a model in which the binding of the C-terminal region of NS5A to STAT1 leads to decreased levels of P-STAT1, ISRE signaling, and ISG transcription and, ultimately, to preferential GT1 resistance to IFN treatment.

Determination of HCV genotypes and viral loads in chronic HCV infected patients of Hazara Pakistan

Hepatitis C Virus (HCV) genotype and viral load are two significant predictive variables knowledge of which might persuade treatment decisions. The objective of the present study was to identify the distribution of different HCV genotypes circulating in the study area and to estimate viral load in chronically HCV infected patients. Out of total 305 HCV positive patients, 177 (58%) were males and 128 (42%) were females. Frequency breakup of the HCV positive patients was 169, 69, 38 and 29 from Abbottabad, Mansehra, Haripur and Battagram districts respectively. Out of the total 305 tested serum samples, 255 (83.06%) were successfully genotyped whereas 50 (16.4%) samples were found with unclassified genotypes. Among typable genotypes, 1a accounted for 21 (6.8%) 1b for 14 (4.6%), 2a for 4 (1.31%) 3a for 166 (54.42%) and genotype 3b for (8.19%). Twenty five (8.19%) patients were infected with mixed HCV genotypes. Viral load distribution was classified into three categories based on its viral load levels such as low (< 60, 0000 IU/mL), intermediate (60,0000-80,0000 IU/mL) and high (> 80,0000 IU/mL). The baseline HCV RNA Viral load in HCV genotype 3 infected patients was 50 (26.17%), 46 (24.08%) and 95 (49.73%) for low, intermediate and high categories respectively. For genotypes other than 3, these values for low, intermediate and high viral load categories were 50 (43.85), 35 (30.70) and 29 (25.43) respectively. Pre-treatment viral load in patients with untypable genotype was 19 (38.00%), 5 (20.00%) and 11 (44.00%) for low, intermediate and high viral load categories. Viral load distribution was also categorized sex wise; for males it was 58 (32.76%), 26 (14.68%) and 93 (52.54%) whereas for females it was 40 (31.25%), 34 (26.56%) and 54 (42.18%) for low, intermediate and high viral load respectively. In conclusion HCV genotype 3a is the most prevalent genotype circulating in Hazara Division like other parts of pakistan. Pre-treatment viral load is significantly high (p 0.014) in patients infected with HCV genotype 3 as compared to other genotypes.

Longevity in the 21st Century

The main objective of this paper is to offer a detailed analysis of mortality change in the United Kingdom at the beginning the 21st century. Starting from an exploration of 20th century mortality trends, focusing in particular on the 1990s, underlying forces driving trends in longevity are discussed. These include the ‘cohort effect’ and the ‘ageing of mortality improvement’. International mortality statistics and trends are also analysed. The pace of medical advances is discussed, with specific focus on research into the ageing process and a potential treatment for cardiovascular disease. The paper also discusses the potential threat from infectious diseases.

The analysis of underlying trends suggests that life expectancy in retirement in the U.K. is likely to increase rapidly in the early part of the 21st century. Some scientists are also claiming that we will be seeing the fruits of anti-ageing research within just a few decades.

A core theme of the paper is that future projections should be grounded in as good an understanding of the past as possible. Different methods for projecting future rates of mortality are discussed, and it is noted that emphasis should be placed on the uncertainty surrounding projections.

The financial impact of using different assumptions for future mortality is explored. Significant differences in the cost of an annuity or pension arise from the use of the various projection bases.

Life assurance companies have already declared significant losses as a result of strengthening reserves on annuity portfolios. Taken together, future increases in life expectancy, increasing awareness of the risk of providing longevity insurance, changes in legislation and shortages in market capacity and capital, may well lead to worsening annuity rates.

It is difficult to assess the precise impact of future changes in life expectancy on final salary pension schemes. There is a lack of readily available information on the mortality assumptions being used in practice. It is therefore suggested that more disclosure in this area would be helpful. Employers sponsoring final salary schemes are making promises to their employees that extend up to 70 or 80 years into the future. Actuaries should be clear in spelling out to employers and trustees the nature of the risks behind the promises they are making. Future scheme design should reflect the possibility of substantial increases in life expectancy.

An over-riding implication of the anticipated increases in life expectancy is that people will remain in work for longer in the future. The age at which people retire will inevitably have to increase, and this trend will necessarily drive changes in all aspects of our society. As actuaries we have a vital role in helping to inform the wider debate.

Evidence for extensive genotypic diversity and recombination of GB virus C (GBV-C) in Germany

Multiple genotypes of GB virus C (GBV-C)-a non-pathogenic flavivirus-have been identified to date, although they are not uniformly distributed worldwide. It has also been suggested that GBV-C genotype may play a role in modulating HIV disease; however, the prevalence and genotype distribution of GBV-C has not been adequately studied in most countries. Among 408 HIV positive subjects in Germany, 97 (23.8%) had detectable GBV-C RNA. Based on sequencing of the 5' untranslated region (5'-UTR), the GBV-C genotypes were 1 (n=8; 8.2%), 2 (n=81; 83.5%), and 3 (n=2; 2.1%), as well as a unique genotype not previously reported (n=6; 6.2%). Among 17 samples also sequenced in the envelope 2 (E2) region, 14 had concordant genotype results when comparing the 5'-UTR and E2, while evidence of intergenotypic recombination was observed among E2 sequences from 3 individuals. These results suggest that genotypic diversity and viral recombination contribute to the overall genetic variability of GBV-C.

Distribution of hepatitis c virus (hcv) genotypes in patients with chronic infection from Rondônia, Brazil

Background

Hepatitis C virus (HCV) is an important human pathogen affecting around 3% of the human population. In Brazil, it is estimated that there are approximately 2 to 3 million HCV chronic carriers. There are few reports of HCV prevalence in Rondônia State (RO), but it was estimated in 9.7% from 1999 to 2005. The aim of this study was to characterize HCV genotypes in 58 chronic HCV infected patients from Porto Velho, Rondônia (RO), Brazil.

Methods

A fragment of 380 bp of NS5B region was amplified by nested PCR for genotyping analysis. Viral sequences were characterized by phylogenetic analysis using reference sequences obtained from the GenBank (n = 173). Sequences were aligned using Muscle software and edited in the SE-AL software. Phylogenetic analyses were conducted using Bayesian Markov chain Monte Carlo simulation (MCMC) to obtain the MCC tree using BEAST v.1.5.3.

Results

From 58 anti-HCV positive samples, 22 were positive to the NS5B fragment and successfully sequenced. Genotype 1b was the most prevalent in this population (50%), followed by 1a (27.2%), 2b (13.6%) and 3a (9.0%).

Conclusions

This study is the first report of HCV genotypes from Rondônia State and subtype 1b was found to be the most prevalent. This subtype is mostly found among people who have a previous history of blood transfusion but more detailed studies with a larger number of patients are necessary to understand the HCV dynamics in the population of Rondônia State, Brazil.

Correlation between mutations in the core and NS5A genes of hepatitis C virus genotypes 1a, 1b, 3a, 3b, 6f and the response to pegylated interferon and ribavirin combination therapy

Several studies have reported correlation between mutations in core and NS5A proteins of hepatitis C virus (HCV) and response to interferon (IFN) therapy. In particular, mutations in NS5A protein have been shown to correlate with responsiveness to IFN treatment of HCV-1b in Japanese patients. This study investigated whether amino acid (aa) mutations in the core and NS5A proteins of HCV-1a, 1b, 3a, 3b and 6f correlated with the response to pegylated interferon (Peg-IFN) plus ribavirin (RBV) therapy in Thai patients. The entire sequences of core and NS5A of HCV from 76 HCV-infected patients were analysed in comparison with corresponding reference sequences. The data revealed that the number of aa mutations in full-length NS5A, its C-terminus, IFN sensitivity-determining region, variable region 3 (V3) and V3 plus flanking region of HCV-1b NS5A protein were significantly higher in responders than in the treatment failure group (P = 0.010, 0.031, 0.046, 0.020 and 0.006, respectively). Similar results were found in a putative protein kinase R binding domain region in HCV-6f NS5A protein (P = 0.022). Moreover, specific aa substitutions in NS5A that appeared to be associated with responders or the treatment failure group were observed at positions 78 and 305 for HCV-1b (P = 0.028), 64 and 52 for HCV-1a (P = 0.033) and 6f (P = 0.045). Nevertheless, analysis of aa sequences of core protein revealed highly conserved sequences among HCV genotypes and no significant differences between the viruses from responders and the treatment failure group. Our findings indicate that mutations in aa residues of NS5A of HCV-1a, 1b and 6f correlated well with responsiveness to Peg-IFN and RBV combination therapy.

Advances in nucleoside monophosphate prodrugs as anti-HCV agents

Nucleoside monophosphate prodrugs that are eventually bioconverted to the active nucleoside triphosphate (NTP) offer the potential to deliver increased intracellular NTP levels and/or organ-specific NTP enhancement. There are several classes of monophosphate prodrugs that have been applied to HCV drug discovery, and some of these approaches are currently being evaluated in humans. This review discusses recent advances in monophosphate prodrug approaches to improve oral absorption, stability and pharmacokinetic profile, including their advantages and potential pitfalls.

Molecular characterization, distribution, and dynamics of hepatitis C virus genotypes in blood donors in Colombia

Hepatitis C virus (HCV) is a frequent cause of acute and chronic hepatitis and a leading cause for cirrhosis of the liver and hepatocellular carcinoma. HCV is classified in six major genotypes and more than 70 subtypes. In Colombian blood banks, serum samples were tested for anti-HCV antibodies using a third-generation ELISA. The aim of this study was to characterize the viral sequences in plasma of 184 volunteer blood donors who attended the "Banco Nacional de Sangre de la Cruz Roja Colombiana," Bogotá, Colombia. Three different HCV genomic regions were amplified by nested PCR. The first of these was a segment of 180 bp of the 5'UTR region to confirm the previous diagnosis by ELISA. From those that were positive to the 5'UTR region, two further segments were amplified for genotyping and subtyping by phylogenetic analysis: a segment of 380 bp from the NS5B region; and a segment of 391 bp from the E1 region. The distribution of HCV subtypes was: 1b (82.8%), 1a (5.7%), 2a (5.7%), 2b (2.8%), and 3a (2.8%). By applying Bayesian Markov chain Monte Carlo simulation, it was estimated that HCV-1b was introduced into Bogotá around 1950. Also, this subtype spread at an exponential rate between about 1970 to about 1990, after which transmission of HCV was reduced by anti-HCV testing of this population. Among Colombian blood donors, HCV genotype 1b is the most frequent genotype, especially in large urban conglomerates such as Bogotá, as is the case in other South American countries.

Synthesis and an antiviral activity evaluation of nucleoside 5´-O-(N-acyl) phosphoramidates

BACKGROUND

pyrimidine nucleoside analogues represent an established class of clinically useful antiviral agents. Once inside the cell, they are activated by a series of intracellular phosphorylation steps to produce 5´-triphosphate derivatives. In many cases, nucleoside analogues are poor substrates for the cellular kinases needed for their activation. It is clear that intracellular introduction of nucleoside analogues as phosphorylated metabolites (so called pronucleotides) could circumvent difficulties associated with the use of non-phosphorylated nucleoside analogues.

METHODS

among the current diverse pronucleotide approaches, nucleoside phosphoramidate derivatives appear to be an interesting class of potential antiviral agents because of the known relatively low stability of the P-N bond in cellular media. On the basis of oxathiaphospholane chemistry, a series of novel conjugates of 5´-O-phosphorylated zidovudine (AZT) and stavudine (d4T) with amino acids carboxamidates were obtained. The synthesis was performed using N-(2-thiono-1,3,2-oxathiaphospholane) derivatives of amino acids carboxamides as precursors.

RESULTS

all synthesized compounds were studied against DNA and RNA viruses. Specific antiviral activities were only detected against HIV type-1 and HIV type-2 in MT-4 cell cultures at compound concentrations that were equally active or slightly inferior to the activity of their parent drugs (2- to 20-fold for the AZT prodrugs and 6- to 40-fold for the d4T prodrugs). The compounds were also evaluated for their anti-HIV activity in CEM and in CEM thymidine-kinase-deficient (CEM/TK(-)) cell cultures.

CONCLUSIONS

loss of compound antiviral potency in the CEM/TK(-) cells suggested an eventual conversion of the test compounds to the free nucleosides prior to further phosphorylation to the active 5´-triphosphate metabolite.

Mutant spectra in virus behavior

RNA viruses replicate as complex mutant spectra, also termed ‘mutant clouds’, known as viral quasispecies. While this is a widely observed viral population structure, it is less known that a number of biologically relevant features of this important group of viral pathogens depend on (or are strongly influenced by) the complexity and composition of mutant spectra. Among them, fitness increase or decrease depending on intrapopulation complementation or interference, selection triggered by memory genomes, pathogenic potential of viruses, disease evolution and the response to antiviral treatments. Quasispecies represent the recognition of complex behavior in viruses, and it is an oversimplification to equate such a population structure with the classic polymorphism of population biology. Darwinian principles acting on genome collectivities that replicate with high error rates provide a unique population structure prone to flexible and largely unpredictable behavior.

Intracellular expression of IRF9 Stat fusion protein overcomes the defective Jak-Stat signaling and inhibits HCV RNA replication

Interferon alpha (IFN-α) binds to a cell surface receptor that activates the Jak-Stat signaling pathway. A critical component of this pathway is the translocation of interferon stimulated gene factor 3 (a complex of three proteins Stat1, Stat2 and IRF9) to the nucleus to activate antiviral genes. A stable sub-genomic replicon cell line resistant to IFN-α was developed in which the nuclear translocation of Stat1 and Stat2 proteins was prevented due to the lack of phosphorylation; whereas the nuclear translocation of IRF9 protein was not affected. In this study, we sought to overcome defective Jak-Stat signaling and to induce an antiviral state in the IFN-α resistant replicon cell line by developing a chimera IRF9 protein fused with the trans activating domain (TAD) of either a Stat1 (IRF9-S1C) or Stat2 (IRF9-S2C) protein. We show here that intracellular expression of fusion proteins using the plasmid constructs of either IRF9-S1C or IRF9-S2C, in the IFN-α resistant cells, resulted in an increase in Interferon Stimulated Response Element (ISRE) luciferase promoter activity and significantly induced HLA-1 surface expression. Moreover, we show that transient transfection of IRF9-S1C or IRF9-S2C plasmid constructs into IFN-α resistant replicon cells containing sub-genomic HCV1b and HCV2a viruses resulted in an inhibition of viral replication and viral protein expression independent of IFN-α treatment. The results of this study indicate that the recombinant fusion proteins of IRF9-S1C, IRF9-S2C alone, or in combination, have potent antiviral properties against the HCV in an IFN-α resistant cell line with a defective Jak-Stat signaling.

Persistent growth of a human plasma-derived hepatitis C virus genotype 1b isolate in cell culture

HCV (hepatitis C virus) research, including therapeutics and vaccine development, has been hampered by the lack of suitable tissue culture models. Development of cell culture systems for the growth of the most drug-resistant HCV genotype (1b) as well as natural isolates has remained a challenge. Transfection of cultured cells with adenovirus-associated RNA(I) (VA RNA(I)), a known interferon (IFN) antagonist and inhibitor of dsRNA-mediated antiviral pathways, enhanced the growth of plasma-derived HCV genotype 1b. Furthermore, persistent viral growth was achieved after passaging through IFN-alpha/beta-deficient VeroE6 cells for 2 years. Persistently infected cells were maintained in culture for an additional 4 years, and the virus rescued from these cells induced strong cytopathic effect (CPE). Using a CPE-based assay, we measured inhibition of viral production by anti-HCV specific inhibitors, including 2'-C-Methyl-D-Adenosine, demonstrating its utility for the evaluation of HCV antivirals. This virus constitutes a novel tool for the study of one of the most relevant strains of HCV, genotype 1b, which will now be available for HCV life cycle research and useful for the development of new therapeutics.

Silibinin and related compounds are direct inhibitors of hepatitis C virus RNA-dependent RNA polymerase

BACKGROUND & AIMS

Silymarin is a mixture of flavonolignans extracted from the milk thistle. Silymarin contains several molecules, including silibinin A, silibinin B, isosilibinin A, isosilibinin B, silicristin, and silidianin. Intravenous infusion of silibinin induces dose-dependent reduction of hepatitis C virus (HCV) RNA levels. The aim of this study was to test the principal isomers contained in silymarin preparations for their ability to inhibit HCV enzymatic functions and replication in different models.

METHODS

The inhibitory activity of silymarin components was tested in HCV RNA-dependent RNA polymerase and NS3/4A protease enzyme assays. Their ability to inhibit replication of an HCV genotype 1b replicon model and the JFH1 infectious HCV model in cell culture was also studied.

RESULTS

Silibinin A, silibinin B, their water-soluble dihydrogen succinate forms and Legalon SIL, a commercially available intravenous preparation of silibinin, inhibited HCV RNA-dependent RNA polymerase function, with inhibitory concentrations 50% of the order of 75-100 microM. Silibinin A and silibinin B also inhibited HCV genotype 1b replicon replication and HCV genotype 2a strain JFH1 replication in cell culture. None of these compounds inhibited HCV protease function.

CONCLUSIONS

Silibinin A and silibinin B, as well as Legalon SIL, inhibit HCV replicon and JFH1 replication in cell culture. This effect is at least partly explained by the ability of these compounds to inhibit HCV RNA-dependent RNA polymerase activity. Our results provide a basis for the optimization and subsequent development of members of the Flavonoid family as specific HCV antivirals.

Targeting viral infection by microRNA inhibition

An inhibitor of microRNA-122 reduces viral load in chimpanzees that are chronically infected with hepatitis C virus, suggesting that such an approach might have therapeutic potential in humans.

Diversity of hepatitis B and C viruses in Chile

Although there is a low prevalence rate (around 1% of the population) of infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) in Chile, little is known about the diversity and molecular characteristics of the circulating viruses. In the present study, 40 HBV and 57 HCV samples from Santiago City, Chile, were examined. The phylogenetic analysis of HBV samples showed the autochthonous genotype F as the most represented genotype in the study (67.5%), while genotypes A, B, C, and D were less frequent (7.5%, 5%, 7.5%, and 12.5%, respectively). The frequency of circulation of HBV genotypes observed is in accordance with the genetic background of the Chilean population. Most of the HCV samples tested belonged to subtype 1b (82%). The coalescent analysis conducted for both the NS5A and NS5B regions of the HCV strains showed similar population growth rates, with a most recent common ancestor estimated to date between 1893 and 1901. This result may indicate that genotype 1b strains circulating in Chile have epidemiological features similar to those described for HCV genotype 1b in Brazil and the United States. However, the most recent common ancestor for Chile is older than that reported recently for genotype 1b in Argentina.

Anti-hepatitis C virus activity of novel beta-d-2'-C-methyl-4'-azido pyrimidine nucleoside phosphoramidate prodrugs

BACKGROUND

2'-C-methyl and 4'-azido nucleosides have previously demonstrated inhibition of hepatitis C virus (HCV) replication by targeting the RNA-dependent RNA polymerase NS5B. In an effort to discover new and more potent anti-HCV agents, we envisioned synthesizing nucleoside analogues by combining the 2'-C-methyl-moiety with the 4'-azido-moiety into one molecule.

METHODS

2'-C-methyl-4'-azido pyrimidine nucleosides were synthesized by first converting 2'-C-methyl ribonucleosides to the corresponding 4'-exocyclic methylene nucleosides. Treatment with iodine azide, benzoylation of the 2'- and 3'-hydroxy groups, oxidative displacement of the 5'-iodo group with meta-chloroperoxybenzoic acid, and debenzoylation gave the desired 2'-C-methyl-4'-azido uridine and thymidine analogues in good yield. Standard conversion of uridine to cytidine via the 4-triazole yielded 2'-C-methyl-4'-azido cytidine. In addition, 5'-phosphoramidate derivatives of 2'-C-methyl-4'-azido uridine and cytidine were synthesized to bypass the initial phosphorylation step.

RESULTS

The prepared nucleosides and their 5'-monophosphate prodrugs were evaluated for their ability to inhibit replication of the hepatitis C virus in a subgenomic replicon cell based assay. Cytotoxicity in Huh7 cells was determined simultaneously with anti-HCV activity by extraction and amplification of both HCV RNA and ribosomal RNA. Among the newly synthesized compounds, only the 5'-monophosphate nucleoside prodrugs had modest and selective anti-HCV activity. All prepared pyrimidine nucleosides and 5'-monophosphate nucleoside prodrugs displayed no evidence of cytotoxicity at high concentrations.

CONCLUSIONS

This work is the first example of both inactive uridine and cytidine analogues of a nucleoside being converted to active anti-HCV nucleosides via 5'-monophosphate prodrugs.

Lethal mutagenesis in a structured environment

We analyze how lethal mutagenesis operates in a compartmentalized host. We assume that different compartments receive different amounts of mutagen and that virions can migrate among compartments. We address two main questions: (1) To what extent can refugia, i.e., compartments that receive little mutagen, prevent extinction? (2) Does migration among compartments limit the effectiveness of refugia? We find that if there is little migration, extinction has to be achieved separately in all compartments. In this case, the total dose of mutagen administered to the host needs to be so high that the mutagen is effective even in the refugia. By contrast, if migration is extensive, then lethal mutagenesis is effective as long as the average growth in all compartments is reduced to below replacement levels. The effectiveness of migration is governed by the ratio of virion replication and death rates, R(0). The smaller R(0), the less migration is necessary to neutralize refugia and the less mutagen is necessary to achieve extinction at high migration rates.

A novel diagnostic target in the hepatitis C virus genome

BACKGROUND

Detection and quantification of hepatitis C virus (HCV) RNA is integral to diagnostic and therapeutic regimens. All molecular assays target the viral 5'-noncoding region (5'-NCR), and all show genotype-dependent variation of sensitivities and viral load results. Non-western HCV genotypes have been under-represented in evaluation studies. An alternative diagnostic target region within the HCV genome could facilitate a new generation of assays.

METHODS AND FINDINGS

In this study we determined by de novo sequencing that the 3'-X-tail element, characterized significantly later than the rest of the genome, is highly conserved across genotypes. To prove its clinical utility as a molecular diagnostic target, a prototype qualitative and quantitative test was developed and evaluated multicentrically on a large and complete panel of 725 clinical plasma samples, covering HCV genotypes 1-6, from four continents (Germany, UK, Brazil, South Africa, Singapore). To our knowledge, this is the most diversified and comprehensive panel of clinical and genotype specimens used in HCV nucleic acid testing (NAT) validation to date. The lower limit of detection (LOD) was 18.4 IU/ml (95% confidence interval, 15.3-24.1 IU/ml), suggesting applicability in donor blood screening. The upper LOD exceeded 10(-9) IU/ml, facilitating viral load monitoring within a wide dynamic range. In 598 genotyped samples, quantified by Bayer VERSANT 3.0 branched DNA (bDNA), X-tail-based viral loads were highly concordant with bDNA for all genotypes. Correlation coefficients between bDNA and X-tail NAT, for genotypes 1-6, were: 0.92, 0.85, 0.95, 0.91, 0.95, and 0.96, respectively; X-tail-based viral loads deviated by more than 0.5 log10 from 5'-NCR-based viral loads in only 12% of samples (maximum deviation, 0.85 log10). The successful introduction of X-tail NAT in a Brazilian laboratory confirmed the practical stability and robustness of the X-tail-based protocol. The assay was implemented at low reaction costs (US$8.70 per sample), short turnover times (2.5 h for up to 96 samples), and without technical difficulties.

CONCLUSION

This study indicates a way to fundamentally improve HCV viral load monitoring and infection screening. Our prototype assay can serve as a template for a new generation of viral load assays. Additionally, to our knowledge this study provides the first open protocol to permit industry-grade HCV detection and quantification in resource-limited settings.

Retracted: Genetic diversity in hepatitis C virus (HCV): A brief review

The following article from Reviews in Medical Virology, Genetic diversity in hepatitis C virus (HCV) a brief review, by M Irshad, published online on December 16 2008 in Wiley InterScience (www.interscience.wiley.com) has been retracted by agreement between the author, the journal Editor in Chief, P.D. Griffiths, and the publisher Wiley Blackwell. The retraction has been agreed due to overlap with the following article by P Simmonds, Genetic diversity and evolution of hepatitis C virus fifteen years on, published in Journal of General Virology, 2004, 85, 3173-3178.