Hepatitis C virus drug resistance-associated substitutions: State of the art summary

An Increase in the Prevalence of Clinically Relevant Resistance-Associated Substitutions in Four Direct-Acting Antiviral Regimens: A Study Using GenBank HCV Sequences

Direct-acting antivirals (DAAs) revolutionized the therapeutics of chronic hepatitis C. The emergence and transmission of HCV variants with resistance-associated substitutions (RASs) can undermine HCV treatment. This study aimed to assess the prevalence and temporal trends of RASs in HCV, with a particular focus on clinically relevant RASs (cr-RASs). Near-complete HCV GenBank sequences archived in the Los Alamos HCV Database were analyzed. The study period was divided into two phases: before 2011 and from 2011 onward. Identification of RASs across three DAA classes (NS3, NS5A, and NS5B inhibitors) was based on the 2020 EASL guidelines. The AASLD-IDSA recommendations were used to identify cr-RASs for three HCV genotypes/subtypes (1a, 1b, and 3) and four DAA regimens: ledipasvir/sofosbuvir; elbasvir/grazoprevir; sofosbuvir/velpatasvir; and glecaprevir/pibrentasvir. The final HCV dataset comprised 3443 sequences, and the prevalence of RASs was 50.4%, 60.2%, and 25.3% in NS3, NS5A, and NS5B, respectively. In subtype 1a, resistance to ledipasvir/sofosbuvir was 32.8%, while resistance to elbasvir/grazoprevir was 33.0%. For genotype 3, resistance to sofosbuvir/velpatasvir and glecaprevir/pibrentasvir was 4.2% and 24.9%, respectively. A significant increase in cr-RASs was observed across the two study phases as follows: for ledipasvir/sofosbuvir in subtype 1a, cr-RASs increased from 30.2% to 35.8% (p = 0.019); for elbasvir/grazoprevir in subtype 1a, cr-RASs increased from 30.4% to 36.1% (p = 0.018); In subtype 1b, neither ledipasvir/sofosbuvir nor elbasvir/grazoprevir showed any cr-RASs in the first phase, but both were present at a prevalence of 6.5% in the second phase (p < 0.001); for sofosbuvir/velpatasvir in genotype 3, cr-RASs increased from 0.9% to 5.2% (p = 0.006); and for glecaprevir/pibrentasvir, cr-RASs increased from 12.0% to 29.1% (p < 0.001). The rising prevalence of HCV RASs and cr-RASs was discernible. This highlights the necessity for ongoing surveillance and adaptation of novel therapeutics to manage HCV resistance effectively. Updating the clinical guidelines and treatment regimens is recommended to counteract the evolving HCV resistance to DAAs.

Molecular characterization of the nonstructural 5A (NS5A) region of hepatitis C virus in Thai blood donors

Direct acting antivirals (DAAs) have been developed for hepatitis C virus (HCV) therapy, and they are usually effective, however resistance to DAA regimens has also been reported to have a significant impact. Resistance associated substitutions (RASs) in the NS5A region are known to be correlated with failure of DAA therapy. HCV genotypes 3a and 1 are the most prevalent genotypes in Thailand. This study analyzed the type and frequency of RASs associated with DAA failure, focusing on the NS5A region. Serum samples of HCV genotype 3a, 1a, and 1b infection from Thai blood donors were selected. The NS5A region was amplified using reverse transcription-polymerase chain reaction (RT-PCR). A phylogenetic tree was constructed to identify the genotypes of HCV. Nucleotide sequencing and amino acid sequencing were conducted to determine the prevalence of RASs. Construction of the phylogenetic tree indicated that 29 samples were genotype 3a, 11 samples were genotype 1a, and 9 were genotype 1b. Both HCV genotypes 1a and 3a can be categorized into two subclades. Results showed that the NS5A substitutions A30V/K, A62T/V/I/M/P/S/L, and S98G were present in HCV genotype 3a. In HCV genotype 1a, only NS5A RASs H54Y was detected. NS5A amino acid substitutions Q54H and P58L were found in HCV genotype 1b. In conclusion, NS5A RASs at amino acid positions 30, 62, 54, 58, and 98 are present within HCV genotypes 3a and 1. While keeping in mind that additional information was not available on the anonymous blood donors tested in this study, these findings can contribute to understand the NS5A mutation. Further study with known patients under drug treatment is recommended.

Structure-based virtual screening of natural compounds as inhibitors of HCV using molecular docking and molecular dynamics simulation studies

The hepatitis C virus (HCV), which causes hepatitis C, is a viral infection that damages the liver and causes inflammation in the liver. New potentially effective antiviral drugs are required for its treatment owing to various issues associated with the existing medications, including moderate to severe adverse effects, higher costs, and the emergence of drug-resistant strains. The objective of the current study was to utilize computational techniques to assess the anti-HCV efficacy of certain phytochemicals against tetraspanin (CD81) and claudin 1 (CLDN1) entry proteins. A 200-nanosecond molecular dynamics (MD) simulation was employed to examine the stability of the lead-protein complexes. Free binding energy and molecular docking calculations were conducted utilizing MM/GBSA method, and the selectivity of hit compounds for CD81 and CLDN1 was determined. Five significant CD81 and CLDN1 inhibitors were identified: Petasiphenone, Silibinin, Tanshinone IIA, Taxifolin, and Topaquinone. The MM/GBSA analysis of the compounds revealed high free binding energies. All the identified compounds were stable within the CD81 and CLDN1 binding pockets. This study indicated the promising inhibitory potential of the identified compounds against CD81 and CLDN1 receptors and might develop into potential viral entry inhibitors. However, to validate the chemotherapeutic capabilities of the discovered leads extensive preclinical research is required.Communicated by Ramaswamy H. Sarma.

Study of drug resistance-associated genetic mutations, and phylo-genetic analysis of HCV in the Province of Sindh, Pakistan

Current management of HCV infection is based on Direct-Acting Antiviral Drugs (DAAs). However, resistance-associated mutations, especially in the NS3 and NS5B regions are gradually decreasing the efficacy of DAAs. The aim of the current study was to identify such mutations in the NS3, and NS5B genes in DAAs treatment-naïve Pakistani chronic HCV 3a patients. Peripheral blood samples were collected from 233 chronic HCV 3a patients at different tertiary care hospitals in Karachi, Pakistan, between August 2020 to September 2021. PCR-amplified target regions of the NS3/NS5B gene were subjected to Sanger sequencing to identify resistance-associated mutations. Phylogenetic analysis of the identified amino acid sequences was performed using HCV3a sequences of the global population in the virus pathogen resource (VIPR) database. Sequence analysis identified five amino acid mutations, Leu36Pro, Gln41His, Gln80Lys/Arg, Ala156Tyr, and Gln168Arg in the NS3 region, and two mutations Leu159Phe and Cys316Arg in the NS5B region. Phylogenetic analysis revealed a high genetic diversity in the studied isolates. Overall, the prevalence of resistance-associated substitutions was almost similar to other geographic regions worldwide. This data could be helpful in selecting the most effective treatment regimen for HCV chronically infected people in Pakistan.

Fitness-Dependent, Mild Mutagenic Activity of Sofosbuvir for Hepatitis C Virus

The concept of a mild mutagen was coined to describe a minor mutagenic activity exhibited by some nucleoside analogues that potentiated their efficacy as antiretroviral agents. In the present study, we report the mild mutagen activity of sofosbuvir (SOF) for hepatitis C virus (HCV). Serial passages of HCV in human hepatoma cells, in the presence of SOF at a concentration well below its cytotoxic concentration 50 (CC50) led to pre-extinction populations whose mutant spectra exhibited a significant increase of C→U transitions, relative to populations passaged in the absence of SOF. This was reflected in an increase in several diversity indices that were used to characterize viral quasispecies. The mild mutagenic activity of SOF was largely absent when it was tested with isogenic HCV populations that displayed high replicative fitness. Thus, SOF can act as a mild mutagen for HCV, depending on HCV fitness. Possible mechanisms by which the SOF mutagenic activity may contribute to its antiviral efficacy are discussed.

Investigation of novel HCV therapies: Boscia angustifalia &Boscia senegalensis extracts loaded on galactosylated chitosan nanoparticles synthesized by eco-friendly method for HCV treatment

Hepatitis C virus (HCV) is a major causative agent of chronic liver diseases including chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma worldwide. Treatment of HCV has evolved from early interferon monotherapy to the current all-oral regimens using direct-acting antivirals. However, antiviral resistance has become a critical issue in the treatment of chronic hepatitis C after receiving therapy with direct-acting antivirals (DAA) with a 0.5 % chance of the hepatitis C virus recurrence, similar to other chronic viral infections. So, retreatment options following treatment failure have become crucial issues. Hence, this study aims to investigate a new promising therapy for HCV. In the field of nanomedicine, chitosan nanoparticles are well-known delivery systems that are frequently used as polymeric carriers. Galactosylated chitosan nanoparticles have been widely applied in HCV treatment. In this study, we have modified galactosylation by an eco-friendly method using l-ascorbic instead of hazardous reagents and we have loaded it with newly tested two Boscia extracts each in three different concentrations. The synthesized chitosan nanoparticles showed two dispersion peaks, at 196 ± 29 nm and 1.33 ± 0.36 μm, with a zeta potential of +3.3 ± 0.4mV with high stability in a range of 40.7 mV. The percentage of encapsulation of Boscia angustifalia extract was found to be 46.58 ± 1.33 % and for Boscia senegalensis extract was 9.77 ± 0.33 %. The release of Boscia angustifalia extract from the nanoparticles was about 40 % in acidic media after 180 min and about 60 % in normal pH. However, the release of Boscia senegalensis extract was 20 % in acidic media and 56 % in normal media after 24 h. Testing of these two newly developed composites against HCV was carried out using an in vitro system for the production of hepatitis C virus (HCV) which was established by infection of human hepatoma cells. Evidence for persistent virus production was monitored by the ELISA technique using an anti-HCV-specific antibody. Results obtained showed that all samples had an anti-HCV activity that increased by increasing concentration, and Boscia angustifalia had remarkable anti-HCV activity compared to Boscia senegalensis.

Looking at the Molecular Target of NS5A Inhibitors throughout a Population Highly Affected with Hepatitis C Virus

Hepatitis C virus (HCV) is associated with liver damage and an increased progression rate to cirrhosis and hepatocellular carcinoma. In Portugal, it is prevalent in vulnerable populations such as injection drug users (IDU). HCV is characterized by a high intra-host variability, and the selecting driving forces could select variants containing resistance-associated substitutions (RAS) that reduce treatment effectiveness. The main goal of this study was to analyze the sequence variation of NS5A in treatment-naïve IDU. The epidemiological and clinical status of hepatitis C were analyzed, and samples were sequenced by Sanger and Next-Generation sequencing (NGS) to assess RAS and confirm HCV subtypes. Phylogenetic classification was concordant: 1a, 52.4%; 1b, 10.7%; 3a, 20.2%; 4a, 8.3%; 4d, 7.1%; and one 2k/1b recombinant. A 1a/3a mixed infection was detected by NGS. RAS were found in 34.5% (29/84) of samples using Sanger sequencing, while in 42.9% (36/84) using NGS. In sequences from subtypes 1a and 1b, RAS K24R, M28V, Q30H/R, H58D/P/Q/R, and RAS L31M and P58S were detected, respectively. In subtype 3a, RAS A30S/T, Y93H and polymorphisms in position 62 were identified. Additionally, RAS P58L was detected in genotype 4. The strategy used for the molecular survey of baseline HCV resistance is of particular importance to achieve treatment effectiveness and contribute to the elimination of hepatitis C.

Transmissible SARS-CoV-2 variants with resistance to clinical protease inhibitors

Vaccines and drugs have helped reduce disease severity and blunt the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, ongoing virus transmission, continuous evolution, and increasing selective pressures have the potential to yield viral variants capable of resisting these interventions. Here, we investigate the susceptibility of natural variants of the main protease [Mpro; 3C-like protease (3CLpro)] of SARS-CoV-2 to protease inhibitors. Multiple single amino acid changes in Mpro confer resistance to nirmatrelvir (the active component of Paxlovid). An additional clinical-stage inhibitor, ensitrelvir (Xocova), shows a different resistance mutation profile. Importantly, phylogenetic analyses indicate that several of these resistant variants have pre-existed the introduction of these drugs into the human population and are capable of spreading. These results encourage the monitoring of resistance variants and the development of additional protease inhibitors and other antiviral drugs with different mechanisms of action and resistance profiles for combinatorial therapy.

High-Resolution Genomic Profiling of a Genotype 3b Hepatitis C Virus from a Flare of an Occult Hepatitis Patient with Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is defined as a syndrome of acutely decompensated cirrhosis in patients with chronic liver disease (CLD). Here we report an ACLF case caused by a flare of occult hepatitis C infection. This patient was infected with hepatitis C virus (HCV) more than a decade ago and hospitalized due to alcohol-associated CLD. Upon admission, the HCV RNA in the serum was negative and the anti-HCV antibody was positive, whereas the viral RNA in the plasma dramatically increased during hospitalization, which suggests an occult hepatitis C infection. Overlapped fragments encompassing the nearly whole HCV viral genome were amplified, cloned, and sequenced. Phylogenetic analysis indicated an HCV genotype 3b strain. Sanger sequencing to 10-fold coverage of the 9.4-kb nearly whole genome reveals high diversity of viral quasispecies, an indicator of chronic infection. Inherent resistance-associated substitutions (RASs) in the NS3 and NS5A but not in the NS5B regions were identified. The patient developed liver failure and accepted liver transplantation, followed by direct-acting antiviral (DAA) treatment. The hepatitis C was cured by the DAA treatment despite the existence of RASs. Thus, care should be taken for occult hepatitis C in patients with alcoholic cirrhosis. The analysis of viral genetic diversity may help to identify an occult hepatitis C virus infection and predict the efficacy of anti-viral treatment.

Transmissible SARS-CoV-2 variants with resistance to clinical protease inhibitors

Vaccines and drugs have helped reduce disease severity and blunt the spread of SARS-CoV-2. However, ongoing virus transmission, continuous evolution, and increasing selective pressures have the potential to yield viral variants capable of resisting these interventions. Here, we investigate the susceptibility of natural variants of the main protease (Mpro/3CLpro) of SARS-CoV-2 to protease inhibitors. Multiple single amino acid changes in Mpro confer resistance to nirmatrelvir (the active component of Paxlovid). An additional clinical-stage inhibitor, ensitrelvir (Xocova), shows a different resistance mutation profile. Importantly, phylogenetic analyses indicate that several of these resistant variants have pre-existed the introduction of these drugs into the human population and are capable of spreading. These results encourage the monitoring of resistance variants and the development of additional protease inhibitors and other antiviral drugs with different mechanisms of action and resistance profiles for combinatorial therapy.

Partial nonstructural 3 region analysis of hepatitis C virus genotype 3a

BACKGROUND

The hepatitis C virus (HCV) is a major cause of illness around the world. HCV genotype 3a is the most prevalent genotype in Thailand. Direct-acting antiviral (DAA) drugs are available for treatment, and these drugs target the NS3, NS5A, and NS5b proteins of HCV. However, HCV variants that are resistant to NS3 protease inhibitors have been found during treatment. This resistance can be naturally occurring or in response to treatment. The purpose of this study is to analyze the codon positions of the main mutation of the partial NS3 gene region of HCV genotype 3a.

METHODS

In order to detect mutations and confirm the genotype of HCV genotype 3a, the nucleotide sequencing and amino acid portion of NS3 were analyzed.

RESULTS

Twenty-six samples were successfully sequenced and clustered within two sub-clades defined as 3a-1 and 3a-2. Through amino acid mutation analysis, the variations were detected at codon positions 122 (3.8%), 132 (84.6%), 168 (100%), 170 (92.3%), 174 (100%), and 175 (100%).

CONCLUSIONS

In conclusion, mutations at positions 168, 170, 174, and 175 of the NS3 region are common within the HCV genotype 3a. This information should be useful in the development of effective anti-viral drugs that can successfully treat HCV infection.

Efficacy decrease of antiviral agents when administered to ongoing hepatitis C virus infections in cell culture

We report a quantification of the decrease of effectiveness of antiviral agents directed to hepatitis C virus, when the agents are added during an ongoing infection in cell culture vs. when they are added at the beginning of the infection. Major determinants of the decrease of inhibitory activity are the time post-infection of inhibitor administration and viral replicative fitness. The efficacy decrease has been documented with antiviral assays involving the combination of the direct-acting antiviral agents, daclatasvir and sofosbuvir, and with the combination of the lethal mutagens, favipiravir and ribavirin. The results suggest that strict antiviral effectiveness assays in preclinical trials may involve the use of high fitness viral populations and the delayed administration of the agents, relative to infection onset.

Identification of NS5B Resistance against SOFOSBUVIR in Hepatitis C Virus Genotype 3a, naive and treated Patients

AIMS

Pakistan has the second highest prevalence of HCV with genotype 3a (GT-3a) being the most frequently circulating genotype. Currently resistance associated substitutions (RASs) are a major challenge in HCV treatment with direct acting antivirals (DAAs). Sofosbuvir (SOF) is an FDA-approved NS5B nucleotide inhibitor. The aim of this study was to identify these RASs in the NS5B gene in naive and treated Pakistani HCV 3a isolates against SOF.

METHODS AND RESULTS

Blood samples were collected from anti-HCV positive patients, followed by HCV RNA isolation and real time PCR quantification. HCV positive patients were processed for HCV RNA genotyping, Patients with genotype 3a were processed for NS5B gene amplification and sequencing. GT-3a was the most prevalent genotype (62.2%). S282T was identified in 2 (8.7%) patients, C316Y/G/R in 3 (13%), V321A, and L320P in 1 (4.3%) each in SOF/RBV resistant patients. Variants of S282 were detected in 3 (13%) of SOF/RBV treated patients. While INF/RBV associated mutations were also analyzed, D244N, A333R, and A334E were identified in 2 (9.5%), 3 (14.2%), and 7 (33.3%) in treatment-naive and 15 (65.2%), 7 (30.4%), and 5 (21.7%) treated patients respectively. Q309R was observed only in one treatment experienced patients. Some substitutions were present at higher frequency in both groups like N307G, K304R, A272D and R345H, considered that they do not have any role in Sofosbuvir resistance.

CONCLUSION

It was concluded that Sofosbuvir RASs are present in Pakistani HCV GT-3a isolates, and they should be monitored carefully, especially in treatment-experienced patients, for further selection of treatment regimens.

SIGNIFICANCE AND IMPACT OF STUDY

HCV RASs have been studied very well across the world but there is scarcity of data regarding this topic in Pakistani population, this study provides data regarding prevalence of these RASs in Pakistani HCV isolates emphasizing the fact that these RASs must be carefully monitored before starting HCV treatment especially in treatment failure patients.

Characterisation of a Hepatitis C Virus Subtype 2a Cluster in Scottish PWID with a Suboptimal Response to Glecaprevir/Pibrentasvir Treatment

Direct-acting antivirals (DAAs) have revolutionised the treatment of Hepatitis C virus (HCV), allowing the World Health Organisation (WHO) to set a target of eliminating HCV by 2030. In this study we aimed to investigate glecaprevir and pibrentasvir (GP) treatment outcomes in a cohort of patients with genotype 2a infection.

METHODS

Clinical data and plasma samples were collected in NHS Greater Glasgow & Clyde. Next generation whole genome sequencing and replicon assays were carried out at the MRC-University of Glasgow Centre for Virus Research.

RESULTS

132 cases infected with genotype 2a HCV were identified. The SVR rate for this group was 91% (112/123) following treatment with GP. An NS5A polymorphism, L31M, was detected in all cases of g2a infection, and L31M+R353K in individuals that failed treatment. The results showed that R353K was present in 90% of individuals in the Glasgow genotype 2a phylogenetic cluster but in less than 5% of all HCV subtype 2a published sequences. In vitro efficacy of pibrentasvir against sub-genomic replicon constructs containing these mutations showed a 2-fold increase in IC₅₀ compared to wildtype.

CONCLUSION

This study describes a cluster of HCV genotype 2a infection associated with a lower-than-expected SVR rate following GP treatment in association with the NS5A mutations L31M+R353K.

Small molecule NS5B RdRp non-nucleoside inhibitors for the treatment of HCV infection: A medicinal chemistry perspective

Hepatitis C virus (HCV) infection has become a global health problem with enormous risks. Nonstructural protein 5B (NS5B) RNA-dependent RNA polymerase (RdRp) is a component of HCV, which can promote the formation of the viral RNA replication complex and is also an essential part of the replication complex itself. It plays a vital role in the synthesis of the positive and negative strands of HCV RNA. Therefore, the development of small-molecule inhibitors targeting NS5B RdRp is of great value for treating HCV infection-related diseases. Compared with NS5B RdRp nucleoside inhibitors, non-nucleoside inhibitors have more flexible structures, simpler mechanisms of action, and more predictable efficacy and safety of drugs in humans. Technological advances over the past decade have led to remarkable achievements in developing NS5B RdRp inhibitors. This review will summarize the non-nucleoside inhibitors targeting NS5B RdRp developed in the past decade and describe their structure optimization process and structure-activity relationship.

The role of IFNL4 in liver inflammation and progression of fibrosis

The discovery that genetic variation within the interferon lambda locus has a profound effect on the outcome of hepatitis C virus (HCV) treatment and spontaneous clearance of HCV is one of the great triumphs of genomic medicine. Subsequently, the IFNL4 gene was discovered and proposed as the causal gene underlying this association. However, there has been a lively debate within the field concerning the causality, which has been further complicated by a change in naming. This review summarizes the genetic data available for the IFNL3/IFNl4 loci and provides an in-depth discussion of causality. We also discuss a new series of interesting data suggesting that the genetic variation at the IFNL4 loci influences the evolution of the HCV virus and the implication this relationship between our genetic makeup and virus evolution has upon our understanding of the IFNL4 system. Finally, new data support an influence of the IFNL4 gene upon liver inflammation and fibrosis that is independent of etiology, thereby linking the IFNL4 gene to some of the major liver diseases of today.

Efficacy and safety of direct-acting antiviral therapies and baseline predictors for treatment outcomes in hepatitis C patients: a multi-center, real-world study in Guangdong, China

 : The data on direct acting antivirals (DAA) in chronic hepatitis C (CHC) patients in southern China with multiple genotypes circulating are limited. This study aims to evaluate the efficacy and safety of DAA regimens among CHC patients in Guangdong, China. A total of 220 patients receiving a variety of DAA were enrolled. The primary outcome was sustained virologic response (SVR) at 12 weeks. Resistance associated substations (RAS) were evaluated by deep sequencing. The overall SVR rate was 96.4%, and was 97.7% for genotype 1, 100% for genotype 2, 91.9% for genotype 3, 95.7% for genotype 6, and 100% for untyped. The overall incidence of adverse events (AEs) was 8.2% (18/220) and all the AEs were mild. Nonstructural protein 5A RAS, 30K/31M and Y93H, were most prevalent at baseline and the end of treatment in non-SVR patients, respectively. Logistics regression showed that elevated ALT and AST at baseline were specifically associated with non-SVR in patients with genotype 3 and 6 infections (P = 0.029 and P = 0.017) but not genotype 1 infection (P = 0.746 and P = 0.971), and baseline AST was the best predictor for SVR in genotype 3 and 6 patients (area under curve = 0.890). CONCLUSION: All DAA regimens achieved ideal SVR and were well tolerated. NS5A RAS were prevalent in non-SVR patients. ALT and AST as baseline predictors for non-SVR in genotype 3 and 6 infections warrant further research in a larger cohort. This article is protected by copyright. All rights reserved.

Assessing in vivo mutation frequencies and creating a high-resolution genome-wide map of fitness costs of Hepatitis C virus

Like many viruses, Hepatitis C Virus (HCV) has a high mutation rate, which helps the virus adapt quickly, but mutations come with fitness costs. Fitness costs can be studied by different approaches, such as experimental or frequency-based approaches. The frequency-based approach is particularly useful to estimate in vivo fitness costs, but this approach works best with deep sequencing data from many hosts are. In this study, we applied the frequency-based approach to a large dataset of 195 patients and estimated the fitness costs of mutations at 7957 sites along the HCV genome. We used beta regression and random forest models to better understand how different factors influenced fitness costs. Our results revealed that costs of nonsynonymous mutations were three times higher than those of synonymous mutations, and mutations at nucleotides A or T had higher costs than those at C or G. Genome location had a modest effect, with lower costs for mutations in HVR1 and higher costs for mutations in Core and NS5B. Resistance mutations were, on average, costlier than other mutations. Our results show that in vivo fitness costs of mutations can be site and virus specific, reinforcing the utility of constructing in vivo fitness cost maps of viral genomes.

Emergence and Persistence of Resistance-Associated Substitutions in HCV GT3 Patients Failing Direct-Acting Antivirals

Background: The hepatitis C virus has a high mutation rate, which results in the emergence of resistance-associated substitutions (RASs). Despite direct-acting antivirals (DAAs) efforts to treat chronically infected HCV genotype 3 (GT3) patients, there are concerns about the emergence and persistence of RASs in DAA failures. The objective of this study was to determine the prevalence of clinically relevant RASs in HCV NS5A and NS5B regions before and after treatment to better understand the role of RASs in treatment failures. Methods: Viral RNA was extracted before and after treatment from serum samples. NS5A and NS5B regions of HCV were amplified by nested PCR, followed by Sanger sequencing. The nucleotide sequences were aligned against HCV GT3 reference sequences, and amino acid substitutions were analyzed using the geno2pheno [hcv] webserver. Results: A total of 76 patients failing DAA therapy were stratified from the cohort of 1388. RASs were detected at the baseline in 15/76 patients and at relapse in 20/76 patients with cirrhosis and previously treated with interferons. The most prevalent NS5A RAS was Y93H found in all treatment-failing patients (14/54 in DCV vs. 6/22 in VEL), followed by A62S/T and A30K. No RASs were identified in NS5B. RASs that were present at the baseline persisted through the 24-week follow-up period and were enriched with emerging RASs during the treatment. The presence of RASs may be one of the causes of treatment failures in 26.3% of patients. Amino acid substitutions were present at the baseline in most of the patients with RASs against NS5A inhibitors. Patients with the baseline Y93H and/or A30K relapse more frequently than patients harboring A62S/T. Conclusion: Treatment-failing patients harbored NS5A RASs, and the most frequent were A30K (5/20), A62S/T (20/20), and Y93H (20/20). Direct resistance testing is recommended for optimizing re-treatment strategies in treatment-failing patients.

Enhanced fitness of hepatitis C virus increases resistance to direct-acting antivirals

Drug resistance mutations of hepatitis C virus (HCV) negatively impact viral replicative fitness. RNA viruses are known to change their replication behaviour when subjected to suboptimal selection pressure. Here, we assess whether mutation supply in HCV is sufficiently large to allow the selection of its variants during dual or triple direct-acting antiviral (DAA) treatment associated with augmented virus fitness or impairment. We engineered randomly mutagenized full-genome libraries to create a highly diverse population of replication-competent HCV variants in cell culture. These variants exhibited escape when treated with NS5A/NS5B inhibitors (daclatasvir/sofosbuvir), and relapse on treatment with a combination of NS3/NS5A/NS5B inhibitors (simeprevir or paritaprevir/daclatasvir/sofosbuvir). Analysis of the relationship between virus fitness and drug resistance of JFH1-derived NS5A-5B variants showed a significant positive correlation (P=0.003). At the earliest time points, intracellular RNA levels remain unchanged in both the subgenomic replicon and infection assays, whereas extracellular RNA levels increased upto ten-fold compared to wild-type JFH1. Beneficial substitutions hyperstimulated phosphatidylinositol 4-phosphate during DAA treatment, and showed decreased dependence on cyclophilins during cyclosporine A treatment, indicating an interplay of virus-host molecular mechanisms in beneficial substitution selection that may necessitate infectious virus production. This comprehensive study demonstrates a possible role for HCV fitness of overcoming drug-mediated selection pressure.

Synthesis and structure-activity relationship study of new biaryl amide derivatives and their inhibitory effects against hepatitis C virus

A series of novel biaryl amide derivatives were synthesized and evaluated for anti-HCV virus activity. Some significant SARs were uncovered. The intensive structural modifications led to fifteen novel compounds with more potent inhibitory activity compared to the hit compounds IMB 26 and IMB1f. Among them, compound 80 was the most active, with EC₅₀ values almost equivalent to the clinical drug telaprevir (EC₅₀ = 15 nM). Furthermore, it also had a good safety and in vitro and oral pharmacokinetic (oral bioavailability in rats: 34%) profile, suggesting a highly drug-like nature. Compound 80represents a more promising scaffold for anti-HCV virus activity for further study.

Simultaneous determination of HCV genotype and NS5B resistance associated substitutions using dried serum spots from São Paulo state, Brazil

Hepatitis C virus (HCV) is responsible for more than 180 million infections worldwide, and about 80 % of infections are reported in Low and Middle-income countries (LMICs). Therapy is based on the administration of interferon (INF), ribavirin (RBV) or more recently Direct-Acting Antivirals (DAAs). However, amino acid substitutions associated with resistance (RAS) have been extensively described and can contribute to treatment failure, and diagnosis of RAS requires considerable infrastructure, not always locally available. Dried serum spots (DSS) sampling is an alternative specimen collection method, which embeds drops of serum onto filter paper to be transported by posting to a centralized laboratory. Here, we assessed feasibility of genotypic analysis of HCV from DSS in a cohort of 80 patients from São Paulo state Brazil. HCV RNA was detected on DSS specimens in 83 % of samples of HCV infected patients. HCV genotypes 1a, 1b, 2a, 2c and 3a were determined using the sequence of the palm domain of NS5B region, and RAS C316N/Y, Q309R and V321I were identified in HCV 1b samples. Concerning therapy outcome, 75 % of the patients who used INF +RBV as a previous protocol of treatment did not respond to DAAs, and 25 % were end-of-treatment responders. It suggests that therapy with INF plus RBV may contribute for non-response to a second therapeutic protocol with DAAs. One patient that presented RAS (V321I) was classified as non-responder, and combination of RAS C316N and Q309R does not necessarily imply in resistance to treatment in this cohort of patients. Data presented herein highlights the relevance of studying circulating variants for a better understanding of HCV variability and resistance to the therapy. Furthermore, the feasibility of carrying out genotyping and RAS phenotyping analysis by using DSS card for the potential of informing future treatment interventions could be relevant to overcome the limitations of processing samples in several location worldwide, especially in LMICs.

The Role of RASs /RVs in the Current Management of HCV

The approval of combination therapies with direct-acting antiviral (DAA) regimens has led to significant progress in the field of hepatitis C virus (HCV) treatment. Although most patients treated with these agents achieve a virological cure, resistance to DAAs is a major issue. The rapid emergence of resistance-associated substitutions (RASs), in particular in the context of incomplete drug pressure, has an impact on sustained virological response (SVR) rates. Several RASs in NS3, NS5A and NS5B have been linked with reduced susceptibility to DAAs. RAS vary based on HCV characteristics and the different drug classes. DAA-resistant HCV variant haplotypes (RVs) are dominant in cases of virological failure. Viruses with resistance to NS3-4A protease inhibitors are only detected in the peripheral blood in a time frame ranging from weeks to months following completion of treatment, whereas NS5A inhibitor-resistant viruses may persist for years. Novel agents have been developed that demonstrate promising results in DAA-experienced patients. The recent approval of broad-spectrum drug combinations with a high genetic barrier to resistance and antiviral potency may overcome the problem of resistance.

Resistance-associated substitutions after sofosbuvir/velpatasvir/voxilaprevir triple therapy failure

Direct-acting antivirals (DAAs) resolve chronic HCV infection in >95% of patients, but a small percentage do not respond to DAA-based therapy. These may be difficult to treat because of resistance-associated substitutions (RAS) emerging after treatment failure. Triple therapy with sofosbuvir (SOF)/velpatasvir (VEL)/voxilaprevir (VOX) is the recommended retreatment after DAA-based failure. However, in rare cases, failure to triple therapy occurs, and there is little information characterizing the viruses that relapse. To determine the RAS profile after failing SOF/VEL/VOX, and seek suitable alternatives for retreatment, samples from 5 patients were analysed using MiSeq Illumina deep sequencing before and after triple therapy. All patients were men, aged 59-78 years, 2 HCV genotype (G) 1b and 3 G3a. The most prevalent NS3 substitutions after SOF/VEL/VOX failure were Y56F and A166T. Four patients had the NS5A RAS, Y93H, after triple failure, and Y93H was observed in both G1b patients before retreatment and after SOF/ledipasvir failure. In 2 G3a patients, Y93H appeared at triple failure, and on the other G3a, A30K persisted in 100% of viral genomes. Finally, G1b patients showed C316N in NS5B, associated with SOF failure, but G3a patients had no known NS5B substitutions. HCV RAS analysis identified the following substitutions present at higher rates after triple failure: Y56F in NS3 (G1b), A166T in NS3 (G3a), A30K or Y93H in NS5A, and C316N in NS5B (G1b). A RAS-based salvage treatment (SOF + glecaprevir/pibrentasvir + RBV) was successfully used in one G3a patient.

World-wide Prevalence of Substitutions in HCV Genome Associated With Resistance to Direct-Acting Antiviral Agents

BACKGROUND & AIMS

The efficacy of direct-acting antiviral agents against hepatitis C virus (HCV) infection can be compromised by substitutions in the HCV genome that occur before treatment (resistance-associated substitutions [RASs]). We performed a meta-analysis to determine the prevalence of RASs and their effects.

METHODS

We searched publication databases for studies of HCV RNA substitutions that mediate resistance to direct-acting antiviral agents. Findings from 50 studies of the prevalence of RAS in HCV, from 32 countries, were used in a meta-analysis. We retrieved the HCV RNA sequence from the Los Alamos HCV sequence database to estimate the prevalence of the RASs. The degree of resistance to treatment conferred by each RAS was determined based on fold-change in the 50% effective concentration of the drugs.

RESULTS

Our final analysis included data from 49,744 patients with HCV infection and 12,612 HCV sequences. We estimated the prevalence of 56 RASs that encoded amino acids and 114 specific RASs. The average prevalence of RASs was highest in HCV genotype (GT) 6, followed by HCV GT1a, GT2, GT1b, GT3, and GT4. The highest prevalence of RASs observed encoded Q80K in NS3 to NS4A of HCV GT1a, Y93T in NS5A of GT1a, and C316N in NS5B of GT1b. The greatest number of RASs were observed at D168 in NS3 to NS4A, at Y93 in NS5A, and at C316 in NS5B. The prevalence of RASs and mutation burdens were high in Japan, the United States, Germany, Thailand, and the United Kingdom; low in Russia, Brazil, Egypt, and India; and intermediate in China, Canada, Australia, Spain, and France.

CONCLUSIONS

In a meta-analysis, we found evidence for 114 RASs in HCV of different genotypes. Patients with HCV infection should be tested for RASs before treatment is selected, especially in regions with a high prevalence of RASs.

Validation of a Genotype-Independent Hepatitis C Virus Near-Whole Genome Sequencing Assay

Despite the effectiveness of direct-acting antiviral agents in treating hepatitis C virus (HCV), cases of treatment failure have been associated with the emergence of resistance-associated substitutions. To better guide clinical decision-making, we developed and validated a near-whole-genome HCV genotype-independent next-generation sequencing strategy. HCV genotype 1-6 samples from direct-acting antiviral agent treatment-naïve and -treated HCV-infected individuals were included. Viral RNA was extracted using a NucliSens easyMAG and amplified using nested reverse transcription-polymerase chain reaction. Libraries were prepared using Nextera XT and sequenced on the Illumina MiSeq sequencing platform. Data were processed by an in-house pipeline (MiCall). Nucleotide consensus sequences were aligned to reference strain sequences for resistance-associated substitution identification and compared to NS3, NS5a, and NS5b sequence data obtained from a validated in-house assay optimized for HCV genotype 1. Sequencing success rates (defined as achieving >100-fold read coverage) approaching 90% were observed for most genotypes in samples with a viral load >5 log₁₀ IU/mL. This genotype-independent sequencing method resulted in >99.8% nucleotide concordance with the genotype 1-optimized method, and 100% agreement in genotype assignment with paired line probe assay-based genotypes. The assay demonstrated high intra-run repeatability and inter-run reproducibility at detecting substitutions above 2% prevalence. This study highlights the performance of a freely available laboratory and bioinformatic approach for reliable HCV genotyping and resistance-associated substitution detection regardless of genotype.

Compartmentalization of Resistance-Associated Substitutions in HIV/HCV-Infected Patients: Possible Correlation with Infecting HCV Genotype

Resistance-associated substitutions (RASs) may exist prior to treatment and contribute to the failure of treatment with direct-acting antivirals (DAAs). As the major site of HCV replication, naturally occurring variants with RASs may segregate into the liver. In the present study, we performed viral population sequencing to retrospectively investigate the NS3 and NS5A RAS profiles in 34 HIV/HCV coinfected patients naïve to anti-HCV treatment who underwent diagnostic liver biopsy between 2000 and 2006 and had liver and plasma samples available. Sixteen were infected by HCV genotype (GT) 1a, 11 by GT3a, and 7 by GT4d. The analysis of the NS3 domain in GT1a showed a difference in strain between the liver and plasma in three cases, with a preponderance of specific RASs in the liver compartment. In GT4d samples, 6/7 coupled liver and plasma samples were concordant with no RASs. Sequence analysis of the NS5A domain showed the presence of RASs in the livers of 2/16 patients harboring GT1a but not in the corresponding plasma. In GT4d, NS5A RASs were detected in 7/7 liver tissues and 5/7 plasma samples. NS3 domain and NS5A domain were found to be conserved in plasma and livers of patients infected with GT3a. Thus, RASs within GT1a and GT4d more likely segregate into the liver and may explain the emergence of resistant strains during DAA treatment.

Dynamic changes of HCV genomes under selective pressure from DAAs therapy in relapsed patients

Currently, direct-acting antiviral drugs (DAAs) are widely used as therapeutic methods for hepatitis C virus (HCV)-positive patients, however, patients may experience treatment failure, and the dynamic changes of HCV genomes in these patients are unknown. In this study, three real-world DAAs cohorts were enrolled to observe clinical efficacy. In addition, serum samples from treatment failure patients at baseline and relapse were used to analyze changes of the HCV genomes at near full-length genome level, including resistance-associated variants (RAVs), viral quasispecies diversity and selection analysis. Next-generation sequencing was used as the detection method. The overall sustained virological response at 12 w after the end of treatment was achieved in 91.9% (57/62) of HCV patients, and 3 paired samples obtained from relapsed patients. All the 3 patients harbored baseline NS5A RAVs, the frequency of NS5A RAVs increased in 2 patients and a new NS5A RAV emerged in 1 patient at relapse, and almost all the viral strains existed with NS5A RAVs at relapse. The results of the viral quasispecies diversity analysis revealed that viral quasispecies diversity decreased at relapse compared to baseline, and the results of selection analysis indicated that the virus population experienced a bottleneck phenomenon, recent selective sweep and population expansion or was under purification selection after DAAs treatment. This study indicated that the clinical efficacy was excellent in real-world DAAs cohorts, and the viral strains existed at relapse were selective by DAAs therapy.

Deciphering Complex Mechanisms of Resistance and Loss of Potency through Coupled Molecular Dynamics and Machine Learning

Drug resistance threatens many critical therapeutics through mutations in the drug target. The molecular mechanisms by which combinations of mutations, especially those remote from the active site, alter drug binding to confer resistance are poorly understood and thus difficult to counteract. A machine learning strategy was developed that coupled parallel molecular dynamics simulations with experimental potency to identify specific conserved mechanisms underlying resistance. Physical features were extracted from the simulations, analyzed, and integrated into one consistent and interpretable elastic network model. To rigorously test this strategy, HIV-1 protease variants with diverse mutations were used, with potencies ranging from picomolar to micromolar to the drug darunavir. Feature reduction resulted in a model with four specific features that predicts for both the training and test sets inhibitor binding free energy within 1 kcal/mol of the experimental value over this entire range of potency. These predictive features are physically interpretable, as they vary specifically with affinity and diagonally transverse across the protease homodimer. This physics-based strategy of parallel molecular dynamics and machine learning captures mechanisms by which complex combinations of mutations confer resistance and identify critical features that serve as bellwethers of affinity, which will be critical in future drug design.

Comparative Analysis of Within-Host Mutation Patterns and Diversity of Hepatitis C Virus Subtypes 1a, 1b, and 3a

Understanding within-host evolution is critical for predicting viral evolutionary outcomes, yet such studies are currently lacking due to difficulty involving human subjects. Hepatitis C virus (HCV) is an RNA virus with high mutation rates. Its complex evolutionary dynamics and extensive genetic diversity are demonstrated in over 67 known subtypes. In this study, we analyzed within-host mutation frequency patterns of three HCV subtypes, using a large number of samples obtained from treatment-naïve participants by next-generation sequencing. We report that overall mutation frequency patterns are similar among subtypes, yet subtype 3a consistently had lower mutation frequencies and nucleotide diversity, while subtype 1a had the highest. We found that about 50% of genomic sites are highly conserved across subtypes, which are likely under strong purifying selection. We also compared within-host and between-host selective pressures, which revealed that Hyper Variable Region 1 within hosts was under positive selection, but was under slightly negative selection between hosts, which indicates that many mutations created within hosts are removed during the transmission bottleneck. Examining the natural prevalence of known resistance-associated variants showed their consistent existence in the treatment-naïve participants. These results provide insights into the differences and similarities among HCV subtypes that may be used to develop and improve HCV therapies.

HCV Diagnosis and Sequencing Using Dried Blood Spots from Patients in Kinshasa (DRC): A Tool to Achieve WHO 2030 Targets

The World Health Organization has established an elimination plan for hepatitis C virus (HCV) by 2030. In Sub-Saharan Africa (SSA) access to diagnostic tools is limited, and a number of genotype 4 subtypes have been shown to be resistant to some direct-acting antivirals (DAAs). This study aims to analyze diagnostic assays for HCV based on dried blood spots (DBS) specimens collected in Kinshasa and to characterize genetic diversity of the virus within a group of mainly HIV positive patients. HCV antibody detection was performed on 107 DBS samples with Vidas® anti-HCV and Elecsys anti-HCV II, and on 31 samples with INNO-LIA HCV. Twenty-six samples were subjected to molecular detection. NS3, NS5A, and NS5B regions from 11 HCV viremic patients were sequenced. HCV seroprevalence was 12.2% (72% with detectable HCV RNA). Both Elecsys Anti-HCV and INNO-LIA HCV were highly sensitive and specific, whereas Vidas® anti-HCV lacked full sensitivity and specificity when DBS sample was used. NS5B/NS5A/NS3 sequencing revealed exclusively GT4 isolates (50% subtype 4r, 30% 4c and 20% 4k). All 4r strains harbored NS5A resistance-associated substitutions (RAS) at positions 28, 30, and 31, but no NS3 RAS was detected. Elecsys Anti-HCV and INNO-LIA HCV are reliable methods to detect HCV antibodies using DBS. HCV subtype 4r was the most prevalent among our patients. RASs found in subtype 4r in NS5A region confer unknown susceptibility to DAA.

Medicinal chemistry strategies for discovering antivirals effective against drug-resistant viruses

During the last forty years we have witnessed impressive advances in the field of antiviral drug discovery culminating with the introduction of therapies able to stop human immunodeficiency virus (HIV) replication, or cure hepatitis C virus infections in people suffering from liver disease. However, there are important viral diseases without effective treatments, and the emergence of drug resistance threatens the efficacy of successful therapies used today. In this review, we discuss strategies to discover antiviral compounds specifically designed to combat drug resistance. Currently, efforts in this field are focused on targeted proteins (e.g. multi-target drug design strategies), but also on drug conformation (either improving drug positioning in the binding pocket or introducing conformational constraints), in the introduction or exploitation of new binding sites, or in strengthening interaction forces through the introduction of multiple hydrogen bonds, covalent binding, halogen bonds, additional van der Waals forces or multivalent binding. Among the new developments, proteolysis targeting chimeras (PROTACs) have emerged as a valid approach taking advantage of intracellular mechanisms involving protein degradation by the ubiquitin-proteasome system. Finally, several molecules targeting host factors (e.g. human dihydroorotate dehydrogenase and DEAD-box polypeptide 3) have been identified as broad-spectrum antiviral compounds. Implementation of herein described medicinal chemistry strategies are expected to contribute to the discovery of new drugs effective against current and future threats due to emerging and re-emerging viral pandemics.

Epidemiological data analysis of viral quasispecies in the next-generation sequencing era

The unprecedented coverage offered by next-generation sequencing (NGS) technology has facilitated the assessment of the population complexity of intra-host RNA viral populations at an unprecedented level of detail. Consequently, analysis of NGS datasets could be used to extract and infer crucial epidemiological and biomedical information on the levels of both infected individuals and susceptible populations, thus enabling the development of more effective prevention strategies and antiviral therapeutics. Such information includes drug resistance, infection stage, transmission clusters and structures of transmission networks. However, NGS data require sophisticated analysis dealing with millions of error-prone short reads per patient. Prior to the NGS era, epidemiological and phylogenetic analyses were geared toward Sanger sequencing technology; now, they must be redesigned to handle the large-scale NGS datasets and properly model the evolution of heterogeneous rapidly mutating viral populations. Additionally, dedicated epidemiological surveillance systems require big data analytics to handle millions of reads obtained from thousands of patients for rapid outbreak investigation and management. We survey bioinformatics tools analyzing NGS data for (i) characterization of intra-host viral population complexity including single nucleotide variant and haplotype calling; (ii) downstream epidemiological analysis and inference of drug-resistant mutations, age of infection and linkage between patients; and (iii) data collection and analytics in surveillance systems for fast response and control of outbreaks.

Treatment outcomes and costs of a simplified antiviral treatment strategy for hepatitis C among monoinfected and HIV and/or hepatitis B virus-co-infected patients in Myanmar

Access to hepatitis C virus (HCV) testing and treatment is limited in Myanmar. We assessed an integrated HIV and viral hepatitis testing and HCV treatment strategy. Sofosbuvir/velpatasvir (SOF/VEL) ± weight-based ribavirin for 12 weeks was provided at three treatment sites in Myanmar and sustained virologic response (SVR) assessed at 12 weeks after treatment. Participants co-infected with HBV were treated concurrently with tenofovir. Cost estimates in 2018 USD were made at Yangon and Mandalay using standard micro-costing methods. 803 participants initiated SOF/VEL; 4.8% were lost to follow-up. SVR was achieved in 680/803 (84.6%) by intention-to-treat analysis. SVR amongst people who inject drugs (PWID) was 79.7% (381/497), but 92.5% among PWID on opioid substitution therapy (OST) (74/80), and 97.4% among non-PWID (298/306). Utilizing data from 492 participants, of whom 93% achieved SVR, the estimated average cost of treatment per patient initiated was $1030 (of which 54% were medication costs), with a production cost per successful outcome (SVR) of $1109 and real-world estimate of $1250. High SVR rates were achieved for non-PWID and PWID on OST. However, the estimated average cost of the intervention (under the assumption of no genotype testing and reduced real-world effectiveness) of $1250/patient is unaffordable for a national elimination strategy. Reductions in the cost of antivirals and linkage to social and behavioural health services including substance use disorder treatment to increase retention and adherence to treatment are critical to HCV elimination in this population.

Direct-acting antiviral agents in the treatment of chronic hepatitis C-Real-life experience from clinical practices in Pakistan

This study aims to evaluate the clinical effectiveness in terms of sustained virological response (SVR), predictors of SVR and safety of available second-generation generic direct-acting antivirals in Pakistani chronic hepatitis C patients. This is a retrospective study conducted in multiple centers of Pakistan from January 2015 to January 2019. The samples include patients infected with chronic hepatitis C virus, regardless of virus genotype, cirrhosis, or prior treatment. A total of 993 patients were included in the present study, with the majority receiving sofosbuvir with daclatasvir (95%), sofosbuvir with daclatasvir and ribavirin (4%), and sofosbuvir with ribavirin (1%). There were 96% cases of chronic hepatitis, 3% cases compensated cirrhosis, and 1% cases of decompensated cirrhosis. Genotype 3 (99.6%) was the most common genotype. Overall SVR after 12 weeks was 98% for all treatment regimens. High SVR12 was observed with sofosbuvir in combination with daclatasvir (98.5%), then sofosbuvir in combination with daclatasvir and ribavirin (90.2%) and sofosbuvir in combination with ribavirin (75%). SVR rates were high in chronic hepatitis C patients (98.2%) as compared with cirrhotic patients (92.1%) and it was high in treatment-naive (98.8%) then interferon experienced patients (90.1%). In multivariate binary logistic regression analysis, patients' education status, treatment strategy, viral load, and alanine aminotransferase had a statistically significant association with SVR at 12 weeks. No major adverse events occurred which required treatment discontinuation. Generic oral direct acting antiviralss (sofosbuvir with daclatasvir) achieved higher SVR12 rates and were well tolerated in this large real-world cohort of genotype 3 infected patients.

Phylodynamic Analysis and Implication of HCV Genotype 4 Variability on Antiviral Drug Response and T-Cell Recognition

Therapies for HCV care could change the prevalence and the geographic distribution of genotypes due to differences in Sustained Virologic Response (SVR). In this scenario, uncommon genotypes/subtypes, such as genotype 4, could spread from high-risk groups, replacing genotypes eradicated by antiviral drugs. Genotype eradication is also strongly influenced by the CD8+ T cell response. In this study, the genetic variability in HCV genotype 4 strains obtained from a cohort of 67 patients naïve to DAA therapy was evaluated. We found that the presence of resistance-associated substitutions (RAS) was able to affect drug responses. Next, using a prediction tool, viral mutations were identified by their ability, or lack thereof, to reduce the binding affinity with HLA, which affects T cell recognition. The Bayesian coalescent analysis suggested two different circulation clusters, one in risk groups (IDUs and MSM) and the other due to migration flows, dated to 1940 and 1915, respectively. Most of the RAS overlapped with HLA and a lack of binding mutations was observed in 96% of strains. This study describes the introduction of HCV genotype 4 in a region of the Mediterranean basin and evaluates how HCV genotype 4's genetic variability could affect the response of antiviral drugs and CD8+ T cell recognition.

Amino Acid Substitutions Associated with Treatment Failure for Hepatitis C Virus Infection

Despite the high virological response rates achieved with current directly acting antiviral agents (DAAs) against hepatitis C virus (HCV), around 2% to 5% of treated patients do not achieve a sustained viral response. The identification of amino acid substitutions associated with treatment failure requires analytical designs, such as subtype-specific ultradeep sequencing (UDS) methods, for HCV characterization and patient management. Using this procedure, we have identified six highly represented amino acid substitutions (HRSs) in NS5A and NS5B of HCV, which are not bona fide resistance-associated substitutions (RAS), from 220 patients who failed therapy. They were present frequently in basal and posttreatment virus of patients who failed different DAA-based therapies. Contrary to several RAS, HRSs belong to the acceptable subset of substitutions according to the PAM250 replacement matrix. Their mutant frequency, measured by the number of deep sequencing reads within the HCV quasispecies that encode the relevant substitutions, ranged between 90% and 100% in most cases. They also have limited predicted disruptive effects on the three-dimensional structures of the proteins harboring them. Possible mechanisms of HRS origin and dominance, as well as their potential predictive value for treatment response, are discussed.

Predominance of positive epistasis among drug resistance-associated mutations in HIV-1 protease

Drug-resistant mutations often have deleterious impacts on replication fitness, posing a fitness cost that can only be overcome by compensatory mutations. However, the role of fitness cost in the evolution of drug resistance has often been overlooked in clinical studies or in vitro selection experiments, as these observations only capture the outcome of drug selection. In this study, we systematically profile the fitness landscape of resistance-associated sites in HIV-1 protease using deep mutational scanning. We construct a mutant library covering combinations of mutations at 11 sites in HIV-1 protease, all of which are associated with resistance to protease inhibitors in clinic. Using deep sequencing, we quantify the fitness of thousands of HIV-1 protease mutants after multiple cycles of replication in human T cells. Although the majority of resistance-associated mutations have deleterious effects on viral replication, we find that epistasis among resistance-associated mutations is predominantly positive. Furthermore, our fitness data are consistent with genetic interactions inferred directly from HIV sequence data of patients. Fitness valleys formed by strong positive epistasis reduce the likelihood of reversal of drug resistance mutations. Overall, our results support the view that strong compensatory effects are involved in the emergence of clinically observed resistance mutations and provide insights to understanding fitness barriers in the evolution and reversion of drug resistance.

Efficacy and Safety of Generic Sofosbuvir Plus Daclatasvir and Sofosbuvir/Velpatasvir in HCV Genotype 3-Infected Patients: Real-World Outcomes From Pakistan

BACKGROUND

Direct-acting antivirals (DAAs) therapeutic regimens are highly effective against chronic hepatitis C virus (HCV) infection. However, HCV patients with genotype 3 (GT3) respond in a suboptimal way. This study aims to identify which of the DAAs-based therapeutic regimens are the best option for GT3.

METHODS

Multiple governments and private tertiary care hospitals were involved in this real-life study of HCV-GT3 patients treated with DAAs. The efficacy and safety of generic sofosbuvir+daclatasvir±ribavirin (SOF+DCV±RBV) and sofosbuvir/velpatasvir±ribavirin (SOF/VEL±RBV) were assessed under the National Hepatitis C Program of Pakistan.

RESULTS

Out of 1,388 participants, 70% of patients received SOF+DCV in government tertiary care hospitals and 30% received SOF/VEL in private tertiary care hospitals. The overall sustained virological responses (SVR) was 95.5%. The SVR rates at 12 weeks were comparable between SOF+DCV (94.4%) and SOF/VEL (94.7%) in chronic HCV patients. However, The SVR rates at 24 weeks were high in cirrhotic patients treated with SOF/VEL+RBV (88%) then SOF+DCV+RBV (83%). Non-responders were high in SOF-DCV than SOF-VEL (4.1 vs 3.8%, P = 0.05) regimen. In multivariate models, the significant predictors of non-SVR were age >60 years (odds ratio [OR] 4.46; 95% CI, 2.35-8.46, P = <0.001) and cirrhosis (OR 53.91; 95% CI, 26.49-109.6, P = <0.001). Skin rash (51 vs 44%) and oral ulcers (45 vs 40%) were high in patients receiving SOF-DCV then SOF-VEL.

CONCLUSIONS

Overall, the generic SOF+DCV ±RBV and SOF/VEL ± RBV achieved equally high SVR12 rates. However, SOF/VEL+RBV achieved a high SVR rate in cirrhotic patients then SOF+DCV+RBV. Old age and cirrhosis were significant predictors of reduced odds of SVR regardless of the regimen. Furthermore, the regimens were well tolerated in chronic HCV patients.

Value of IFNL3 genetic polymorphism in the prediction of HCV treatment response to direct-acting antiviral drugs versus interferon therapy

Background: Despite the outstanding results of direct-acting antiviral therapies (DAAs) of Hepatitis C infection (HCV), non-responders had to be more defined. Aim: assess the outcome of DAAs in linkage with Interferon lambda 3 (IFNL3) in HCV patients. Methods: This case-control-study was conducted on 495 chronic-HCV (genotype-4a), previously treated Egyptians by either DAAs (responders 195, 120 relapsers) or interferon/ribavirin (IFN/RBV) (140 responders, 60 relapsers), and 98 healthy controls. IFNL3 distribution, clinical and laboratory data were assessed. Results: CT was the most predominant genotype in Egyptians (51%). All genotypes were sensitive to DAAs mainly CT genotype (60%), even TT genotype (resistant to IFN/RBV 40%) had 29.2% sensitivity. CT genotype was predominant in sofosbuvir/Daclatasvir responders (67.6%) (OR = 0.66), while non-CT prevailed in relapsers (56.7%). TT genotype may respond to SOF/Ledi better than other regimens (66.7%). In IFN/RBV relapsers; CT genotype was commoner (50%) than others, while CC genotype predominated in responders (54.3%). The c allele was the commonest in responders to IFN/RBV (71.4%), while the T allele was resistant to treatment (65% in relapsers). Addition of RBV to SOF/DCV reported higher resistance with CT genotype (42.2%-50%) and TT genotype (17.8%-27.8%). Conclusion: This study recommended IFNL3 genotyping to be a prerequisite before stratifying treatment for HCV-4a Egyptians.

Effectiveness of direct-acting antivirals for hepatitis C virus infection in hepatitis C/HIV coinfected individuals: A multicenter study

In a hepatitis C virus (HCV)/HIV-positive Brazilian cohort, evaluate the safety and efficacy of HCV DAAs, the frequency of resistance substitutions in the HCV NS5A and NS5B genes and identify predictors of treatment failure.Retrospective multicenter study of HCV/HIV patients treated with sofosbuvir (SOF)-based regimens at 10 reference centers in Brazil.Clinical and virological data were collected. Genetic diversity in the NS5A and NS5B genes was assessed by direct nucleotide sequencing. The primary outcome was sustained virological response (SVR) 12 weeks after DAA completion.Of 643 HCV/HIV patients analyzed, 74.7% were male, median CD4+ T cell count was 617 cells/mm, 90% had an undetectable HIV viral load. HCV genotype 1 was detected in 80.2%, and 60% were taking at least 1 medication other than antiretroviral drugs during their DAA therapy. Cirrhosis was present in 42%. An SOF/daclatasvir (DCV) regimen was used in most patients (98%). The frequency of NS5A polymorphisms associated with clinically relevant resistance to DCV was 2%; no relevant NS5B variants were identified. The SVR12 rate was 92.8% in an intention to treat (ITT) analysis and 96% in a modified ITT (m-ITT) analysis. AE occurred in 1.6% of patients. By multivariate analysis, therapeutic failure was associated, in the m-ITT analysis, with concomitant use of anticonvulsant drugs (P = .001), age (P = .04), and female gender (P = .04).SOF/DCV regimens were associated with a high SVR rate in an HCV/HIV population. The use of concurrent anticonvulsant drugs and DAAs decreases the chances of achieving an SVR.

Molecular characterization of hepatitis C virus for subtype determination and resistance-associated substitutions detection among Chinese voluntary blood donors

BACKGROUND

The high prevalence of hepatitis C virus (HCV) infection and the resulting burden of the disease are significant issues to public health worldwide. Although direct-acting antiviral drugs (DAAs) with good tolerance and bioavailability are available, resistance-associated substitutions (RASs) often jeopardize the successful sustainment of virological responses in HCV treatment. High-frequency baseline RASs in treatment-naïve patients can lead to failures in DAA treatment. Clinical data on HCV RASs in patients from China are limited and require investigations.

METHODS

262 HCV RNA positive plasma from Chinese blood donors were genotyped and amplified with subtype-specific primers for NS3 and NS5A regions. RASs were analyzed using Geno2pheno. The codon usage of each resistance-associated substitution was calculated for genetic barrier analysis.

RESULTS

The two main subtypes in mainland China were 1b and 2a, followed by subtype 6a, 3b, 3a, and 1a. In NS3 region of 1b subtype, substitutions (T54S, V55A, Y56F, Q80 K/L, S122 G/T, R117 H/C, V170I and S174A) were present in 89.7% (96/107) of the samples. Other RASs (M28L, R30Q, P58 L/S and Y93H) were observed in 22.1% (25/113) of the samples in NS5A region. A crucial RAS, Q80K, and two other mutations (S122G + V170I) was identified in the same sequence, which reduced its susceptibility to protease inhibitor ASV and resulted in resistance to SMV. In NS5A, Y93H was detected in 9.7% (11/113) of the 1b samples, leading to medium-to-high level resistance to all six commercialized NS5A inhibitors. S122G-NS3 and Y93H-NS5A occurred simultaneously in 38.1% (7/22) of the samples with mutations in both two regions. Moreover, codon usage of S122G-NS3 and Y93H-NS5A revealed that both variants had the lowest genetic barrier and required only one transition to confer resistance.

CONCLUSIONS

Low genetic barriers facilitated the generation of resistance mutants and threated the efficacy of DAA regimens. The baseline RASs posed a great challenge to real-world DAA application.

Quadruple Therapy Offers High SVR Rates in Patients with HCV Genotype 4 with Previous Treatment Failure

BACKGROUND AND AIMS

Direct-acting antivirals (DAAs) have made a revolution in hepatitis C virus (HCV) treatment with promising reduction of HCV infection and disease morbidities. However, unfortunately, treatment failure still occurs in about 5-15% of patients treated with DAA-based combination regimens. The primary aim of the study was to assess the efficacy and safety of a quadruple regimen of (sofosbuvir, daclatasvir, and simeprevir with a weight-based ribavirin) in chronic HCV DAAs-experienced patients.

METHODS

This observational, open-label prospective study was carried out on 103 genotype 4 hepatitis C virus-infected patients who failed to achieve SVR12 after sofosbuvir-daclatasvir with or without ribavirin. Patients were treated for three months with sofosbuvir (400 mg), daclatasvir (60 mg), and simeprevir (150 mg) with a weight-based ribavirin dosage (1000-1200 mg/d). Response to treatment was determined by quantitative PCR for HCV at 3 months after the end of treatment (SVR12), and adverse events during the treatment were recorded.

RESULTS

SVR was achieved in 100 patients (97.1%) at week 12 after treatment. No dangerous or life-threatening adverse events were recorded.

CONCLUSIONS

Retreatment of HCV genotype 4 patients with quadruple therapy is a good therapeutic option and achieves high response rates with minimal side effects.

Detection of low-level HCV variants in DAA treated patients: comparison amongst three different NGS data analysis protocols

BACKGROUND

Notwithstanding the efforts of direct-acting antivirals (DAAs) for the treatment of chronically infected hepatitis C virus (HCV) patients, concerns exist regarding the emergence of resistance-associated substitutions (RAS) related to therapy failure. Sanger sequencing is still the reference technique used for the detection of RAS and it detects viral variants present up to 15%, meaning that minority variants are undetectable, using this technique. To date, many studies are focused on the analysis of the impact of HCV low variants using next-generation sequencing (NGS) techniques, but the importance of these minority variants is still debated, and importantly, a common data analysis method is still not defined.

METHODS

Serum samples from four patients failing DAAs therapy were collected at baseline and failure, and amplification of NS3, NS5A and NS5B genes was performed on each sample. The genes amplified were sequenced using Sanger and NGS Illumina sequencing and the data generated were analyzed with different approaches. Three different NGS data analysis methods, two homemade in silico pipeline and one commercially available certified user-friendly software, were used to detect low-level variants.

RESULTS

The NGS approach allowed to infer also very-low level virus variants. Moreover, data processing allowed to generate high accuracy data which results in reduction in the error rates for each single sequence polymorphism. The results improved the detection of low-level viral variants in the HCV quasispecies of the analyzed patients, and in one patient a low-level RAS related to treatment failure was identified. Importantly, the results obtained from only two out of the three data analysis strategies were in complete agreement in terms of both detection and frequency of RAS.

CONCLUSIONS

These results highlight the need to find a robust NGS data analysis method to standardize NGS results for a better comprehension of the clinical role of low-level HCV variants. Based on the extreme importance of data analysis approaches for wet-data interpretation, a detailed description of the used pipelines and further standardization of the in silico analysis could allow increasing diagnostic laboratory networking to unleash true potentials of NGS.

HCV Replicon Systems: Workhorses of Drug Discovery and Resistance

The development of direct-acting antivirals (DAAs) has revolutionized the state-of-the art treatment of HCV infections, with sustained virologic response rates above 90%. However, viral variants harboring substitutions referred to as resistance-associated substitutions (RASs) may be present in baseline levels and confer resistance to DAAs, thereby posing a major challenge for HCV treatment. HCV replicons have been the primary tools for discovering and evaluating the inhibitory activity of DAAs against viral replication. Interest in replicon systems has further grown as they have become indispensable for discovering genotype-specific and cross-genotype RASs. Here, we review functional replicon systems for HCV, how these replicon systems have contributed to the development of DAAs, and the characteristics and distribution of RASs for DAAs.

Pre-treatment antiviral resistance in Australians with chronic hepatitis C: prevalence of NS3 and NS5A resistance data in the state of New South Wales

BACKGROUND

Direct-acting antivirals (DAAs) have revolutionized HCV treatment, but the impact of antiviral resistance at a population level is still not clear. The majority of patients who fail DAA therapy develop resistance-associated substitutions (RASs), which can impact re-treatment. There is potential for resistance prevalence to rise in the community with treatment scale up, due to transmission of resistant virus. Monitoring for increasing antiviral resistance requires a reliable baseline, yet there are few published data on the prevalence of HCV resistance in Australia. The aim of this study was to determine the prevalence of RASs among untreated Australians with HCV genotype-1a infection, to inform ongoing surveillance.

METHODS

A cross-sectional study was performed at a single large university hospital pathology laboratory in Australia. Archived blood samples referred for HCV genotype testing were analysed. All patients were naive to DAAs. The prevalence of RASs in the HCV NS3 and NS5A regions was determined using Sanger based population sequencing.

RESULTS

Of 379 samples tested, 34% contained DAA-resistant virus: 24% had resistance to NS3 protease inhibitors, 12% had NS5A inhibitor resistance and 4% of patients had resistance to both drug classes. Clinically relevant RASs conferring resistance against NS5A inhibitors ledipasvir, daclatasvir and elbasvir were detected in 5.8% of samples.

CONCLUSIONS

This is the largest study of HCV antiviral drug resistance in Australia, which differs from resistance prevalence in the USA. The results provide valuable data on the baseline prevalence of HCV resistance, which can be used in the future to monitor for increasing antiviral resistance.

Features of resistance-associated substitutions after failure of multiple direct-acting antiviral regimens for hepatitis C

Background & Aims

We aimed to clarify the features of resistance-associated substitutions (RASs) after failure of multiple interferon (IFN)-free regimens in HCV genotype 1b infections.

Methods

A total of 1,193 patients with HCV for whom direct-acting antiviral (DAA) treatment had failed were enrolled from 67 institutions in Japan. The RASs in non-structural protein (NS)3, NS5A, and NS5B were determined by population sequencing.

Results

Failure of 1, 2, and 3 regimens was observed in 1,101; 80; and 12 patients, respectively. Among patients with failure of 1 regimen, Y56H and D168V in NS3 were more frequently detected after failure of paritaprevir, whereas D168E was more frequently detected after failure of regimens including asunaprevir. R30H and L31-RAS in NS5A were frequently detected after failure of regimens including daclatasvir. The prevalence of Y93-RAS was high irrespective of the regimen. S282T RAS in NS5B was detected in 3.9% of ledipasvir/sofosbuvir failures. The prevalence of D168-RAS increased significantly according to the number of failed regimens (p <0.01), which was similar to that seen with L31-RAS and Y93-RAS. The prevalence of patients with RASs in either NS3 or NS5A, or in both, increased significantly with increasing numbers of failed regimens. The P32del, which is unique to patients for whom DAA had failed, was linked to the absence of Y93H, the presence of L31F, and previous exposure to IFN plus protease inhibitor regimens.

Conclusions

Failure of multiple DAA regimens can lead to the generation of multiple RASs in the NS3 and NS5A regions of the HCV 1b genome. These mutations contribute to viral resistance to multiple treatment regimens and, therefore, should be considered during decision making for treatment of chronic HCV.

Lay summary

Resistance-associated substitutions (RAS) in the genome of the hepatitis C virus are 1 of the major causes for failed treatment. We investigated RASs after failure of various treatments for chronic hepatitis C, and found that more complicated RASs accumulated in the viral genome with successive failed treatments. The highly resistant P32del RAS at NS5A region was uniquely found in patients for whom DAA treatments had failed, and was linked to the presence and absence of specific RASs.

NS5A resistance - associated substitutions in chronic hepatitis C patients with direct acting antiviral treatment failure in Turkey

OBJECTIVES

Chronic hepatitis C (CHC) is now a more curable disease with new direct acting antivirals (DAA). Although high sustained virologic response rates, failures still occur in DAA regimens. Our objective in this study was to characterize the real-life presence of clinically relevant resistance - associated substitutions (RASs) in the HCV NS5A gene in CHC patients whose DAA regimen has failed.

METHODS

The study enrolled 53 CHC patients who experienced failure with DAA regimen as the prospective longitudinal cohort between 2017-2019. Genotypic resistance testing was performed via the viral population sequencing method and The Geno2pheno HCV tool was used for RAS analysis.

RESULTS

The most frequent failure category was relapse (88%) followed by non-responder (12%). For a total of 36% of patients, RASs was detected in NS5A, Y93H was the most detected RAS in GT1b infected patients (89%).

CONCLUSIONS

This study establishes an HCV failure registry for Turkey in which samples were combined with clinical, virologic and molecular data of adult patients whose DAA therapy failed. RASs can occur in CHC patients with DAA treatment failures. Evaluation of RAS after DAA failure is very important before re-treatment is initiated to prevent virologic failure.