Resistance-associated variants in HCV subtypes 1a and 1b detected by Ion Torrent sequencing platform

Next Generation Sequencing Approaches to Characterize the Respiratory Tract Virome

The COVID-19 pandemic and heightened perception of the risk of emerging viral infections have boosted the efforts to better understand the virome or complete repertoire of viruses in health and disease, with a focus on infectious respiratory diseases. Next-generation sequencing (NGS) is widely used to study microorganisms, allowing the elucidation of bacteria and viruses inhabiting different body systems and identifying new pathogens. However, NGS studies suffer from a lack of standardization, in particular, due to various methodological approaches and no single format for processing the results. Here, we review the main methodological approaches and key stages for studies of the human virome, with an emphasis on virome changes during acute respiratory viral infection, with applications for clinical diagnostics and epidemiologic analyses.

Frequency distribution of HCV resistance-associated variants in infected patients treated with direct-acting antivirals

BACKGROUND

Hepatitis C virus (HCV) is a global public health problem. Second-generation direct-acting antivirals targeting non-structural regions on the viral genome are the cornerstone for treatment of chronic infection. However, resistance-associated variants (RAVs) have been reported to be associated with therapeutic failure. The aim of this study was to assess the frequency of variants, including RAVs, in the NS3, NS5A and NS5B regions at baseline in Brazilian patients with chronic hepatitis C with HCV genotypes 1a, 1b and 3a.

METHODS

Serum samples from 13 patients were used to obtain viral RNA. Massively parallel sequencing was performed using genotype-specific amplicons and a panel of Ampliseq technology for all genotypes.

RESULTS

Several non-synonymous substitutions were detected at baseline for 11 responders and pre-/post-treatment for two non-responders. HCV genotype 3a was found to have significantly more non-synonymous substitutions than HCV genotype 1 in the NS3 and NS5A regions. Analyses were conducted using quantitative and qualitative inter- and intrapatient comparisons. Variants that confer resistance to the treatment used by the patients were found in both responders and non-responders.

CONCLUSIONS

A wide frequency distribution of RAVs was found at baseline, and this did not interfere with the achievement of a sustained response. Evaluation of the presence of RAVs requires additional study in order to determine clinical relevance.

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.

Phylogenetic and Molecular Analyses of More Prevalent HCV1b Subtype in the Calabria Region, Southern Italy

Hepatitis C virus subtype 1b (HCV1b) is still the most prevalent subtype worldwide, with massive expansion due to poor health care standards, such as blood transfusion and iatrogenic procedures. Despite safe and effective new direct antiviral agents (DAA), treatment success can depend on resistance-associated substitutions (RASs) carried in target genomic regions. Herein we investigated transmission clusters and RASs among isolates from HCV1b positive subjects in the Calabria Region. Forty-one NS5B and twenty-two NS5A sequences were obtained by Sanger sequencing. Phylogenetic analysis was performed using the maximum likelihood method and resistance substitutions were analyzed with the Geno2pheno tool. Phylogenetic analysis showed sixteen statistically supported clusters, with twelve containing Italian sequences mixed with foreign HCV1b isolates and four monophyletic clusters including only sequences from Calabria. Interestingly, HCV1b spread has been maintained by sporadic infections in geographically limited areas and by dental treatment or surgical intervention in the metropolitan area. The L159F NS5B RAS was found in 15 isolates and in particular 8/15 also showed the C316N substitution. The Y93H and L31M NS5A RASs were detected in three and one isolates, respectively. The A92T NS5A RAS was found in one isolate. Overall, frequencies of detected NS5B and NS5A RASs were 36.6% and 22.7%, respectively. For the eradication of infection, improved screening policies should be considered and the prevalence of natural RASs carried on viral strains.

Hepatitis C virus genotype 1 infection: Prevalence of NS5A and NS5B resistance-associated substitutions in naïve patients from Argentina

Direct acting antiviral (DAA) therapy against hepatitis C virus (HCV) increases sustained virologic response rates. Nevertheless, drug resistance has occasionally been associated with failure to DAA. However, the information about the prevalence of NS5A and NS5B resistance-associated substitutions (RASs) in Argentina is very scarce. In this study, we determine the prevalence of NS5A and NS5B resistances to treatment in Argentinean DAA treatment-naïve patients chronically infected with genotype 1 (HCV-1). In this retrospective cross-sectional study, 108 HCV-1-infected patients were studied. RASs in NS5A and NS5B were analyzed by Sanger at baseline and phylogenetic analysis was performed. NS5A and NS5B RASs were detected in 25.8% and 6.3% of the analyzed sequences, respectively. The most frequent primary RASs for NS5A were L31M (7.5%) and Y93H (3.2%) and for NS5B was L159F (3.8%). No association between the presence of RASs and the outcome of DAA treatment was found in this study. Additionally, most of the Argentinean samples were randomly distributed among sequences around the world in the phylogenetic analysis. Only one significant Argentinean cluster was observed in both regions but without any particular RASs pattern. Baseline RASs in NS5A and NS5B were frequently observed in HCV-1-infected patients from Buenos Aires, Argentina but not related to treatment outcome. No clusters related to RASs transmission were observed in the phylogenetic analysis. The frequency of RASs detected in this study supports the need for more molecular epidemiology studies on RASs to adjust local treatment guidelines with the incorporation of autochthonous data.

Next-generation sequencing for the clinical management of hepatitis C virus infections: does one test fits all purposes?

While the prospect of viral cure is higher than ever for individuals infected with the hepatitis C virus (HCV) due to ground-breaking progress in antiviral treatment, success rates are still negatively influenced by HCV's high genetic variability. This genetic diversity is represented in the circulation of various genotypes and subtypes, mixed infections, recombinant forms and the presence of numerous drug resistant variants among infected individuals. Common misclassifications by commercial genotyping assays in combination with the limitations of currently used targeted population sequencing approaches have encouraged researchers to exploit alternative methods for the clinical management of HCV infections. Next-generation sequencing (NGS), a revolutionary and powerful tool with a variety of applications in clinical virology, can characterize viral diversity and depict viral dynamics in an ultra-wide and ultra-deep manner. The level of detail it provides makes it the method of choice for the diagnosis and clinical assessment of HCV infections. The sequence library provided by NGS is of a higher magnitude and sensitivity than data generated by conventional methods. Therefore, these technologies are helpful to guide clinical practice and at the same time highly valuable for epidemiological studies. The decreasing costs of NGS to determine genotypes, mixed infections, recombinant strains and drug resistant variants will soon make it feasible to employ NGS in clinical laboratories, to assist in the daily care of patients with HCV.

Discussion on critical points for a tailored therapy to cure hepatitis C virus infection

Hepatitis C virus (HCV) infects around 71 million people worldwide and in 2018 it is still a major health problem. Since 2011, anti-HCV therapy with availability of direct-acting antiviral drugs has revolutionized the clinical response and paved the way to eradication strategies. However, despite the high rate of sustained virological response, treatment failure may occur in a limited percentage of patients, possibly due to resistance-associated substitutions (RASs), either emergent or pre-existent even in minority viral populations. Clearly this problem may impair success of eradication strategies. With this background, several questions marks still exist around HCV treatment, including whether pan-genotypic treatments with complete effectiveness in any clinical conditions really exist outside clinical trials, the actual cost-effectiveness of genotyping testing, and utility of RAS detection in viral quasispecies by next generation sequencing approach. In this review, we describe these critical points by discussing recent literature data and our research experience.

Prevalence and Factors Related to Natural Resistance-Associated Substitutions to Direct-Acting Antivirals in Patients with Genotype 1 Hepatitis C Virus Infection

This study aimed to assess the prevalence of natural resistance-associated substitutions (RASs) to NS3, NS5A and NS5B inhibitors in 86 genotype 1 Hepatitis C Virus (HCV)-infected patients from Buenos Aires, Argentina, and to determine their effect on therapy outcome. Additionally, virological, clinical and host genetic factors were explored as predictors of the presence of baseline RASs. NS3 RASs (39.2%) were more prevalent than NS5A RASs (25%) and NS5B RASs (8.9%). In the three regions, the frequencies of RASs were significantly higher in HCV-1b than in HCV-1a. The prevalence of Y93H, L159F and Q80K were 1.3%, 6.3% and 2.5%, respectively. IFNL3 CC genotype was identified as an independent predictor of the presence of baseline RASs in NS5A and NS3 genes (p = 0.0005 and p = 0.01, respectively). Sustained virologic response was achieved by 93.3% of the patients after receiving direct-acting antivirals (DAAs), although 48.7% of them showed baseline RASs related to the DAA-regimen. Notably, the prevalence of clinically relevant RASs in the three genes was lower than that observed around the world. The baseline presence of RASs in both subtypes did not appear to affect therapy outcome. These results support the need to evaluate resistance patterns in each particular country since RASs´ prevalence significantly vary worldwide.

Pretreatment Hepatitis C Virus NS5A/NS5B Resistance-Associated Substitutions in Genotype 1 Uruguayan Infected Patients

Hepatitis C Virus (HCV) infection treatment has dramatically changed with the advent of direct-acting antiviral agents (DAAs). However, the efficacy of DAAs can be attenuated by the presence of resistance-associated substitutions (RASs) before and after treatment. Indeed, RASs detected in DAA treatment-naïve HCV-infected patients could be useful for clinical management and outcome prediction. Although the frequency of naturally occurring HCV NS5A and NS5B RASs has been addressed in many countries, there are only a few reports on their prevalence in the South American region. The aim of this study was to investigate the presence of RASs to NS5A and NS5B inhibitors in a DAA treatment naïve cohort of Uruguayan patients infected with chronic hepatitis C and compare them with reports from other South American countries. Here, we found that naturally occurring substitutions conferring resistance to NS5A and NS5B inhibitors were present in 8% and 19.2%, respectively, of treatment-naïve HCV genotype 1 infected patients. Importantly, the baseline substitutions in NS5A and NS5B herein identified differ from the studies previously reported in Brazil. Furthermore, Uruguayan strains subtype 1a clustered within all major world clades, showing that HCV variants currently circulating in this country are characterized by a remarkable genetic diversity.

Prevalence of naturally occurring amino acid substitutions associated with resistance to hepatitis C virus NS3/NS4A protease inhibitors in São Paulo state

Hepatitis C (HCV)-infected patients are treated with direct-acting antiviral agents (DAAs) in highly effective, well-tolerated, all-oral regimens. However, naturally occurring resistance-associated amino acid substitutions (RASs) may be selected during treatment. This study aimed to screen naturally occurring RASs NS3/NS4A inhibitors (PIs). Samples were obtained from DAA naïve patients, living in São Paulo state, Brazil. Screening for RASs in the HCV NS3 region was conducted in 859 samples from HCV-infected patients, of which 425 and 434 samples were subtype 1a and 1b, respectively. HCV-RNA was extracted, amplified, and sequenced. The overall prevalence of RASs to HCV PIs was 9.4%. The following RASs were observed in HCV-1a subtype infected patients: V36L (2.6%), T54S (1.6%), V55I/A (1.2% / 8.9%, respectively), Q80K (2.1%), R155K (0.5%), and D168E (0.2%); and in HCV-1b infected patients: V36L (0.7%), T54A/S (0.2% and 0.5%, respectively), V55A (0.5%), Q80K (0.2%), D168E (1.6%), and M175L (0.5%). HCV 1a infected subjects had higher serum viral load than that seen in patients infected with HCV 1b. There was no difference between the proportions of NS3 RASs with regards to geographic distribution within the investigated areas. These findings should be supported by additional studies in Brazil to help in the formation of local clinical guidelines for managing hepatitis C.

Evolution of selective-sequencing approaches for virus discovery and virome analysis

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Description of virus enrichment techniques for metagenomics based virome analysis.

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Usefulness of recently developed virome capture sequencing techniques.

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Perspective on negative and positive selection approaches for virome analysis.

Recent advances in sequencing technologies have transformed the field of virus discovery and virome analysis. Once mostly confined to the traditional Sanger sequencing based individual virus discovery, is now entirely replaced by high throughput sequencing (HTS) based virus metagenomics that can be used to characterize the nature and composition of entire viromes. To better harness the potential of HTS for the study of viromes, sample preparation methodologies use different approaches to exclude amplification of non-viral components that can overshadow low-titer viruses. These virus-sequence enrichment approaches mostly focus on the sample preparation methods, like enzymatic digestion of non-viral nucleic acids and size exclusion of non-viral constituents by column filtration, ultrafiltration or density gradient centrifugation. However, recently a new approach of virus-sequence enrichment called virome-capture sequencing, focused on the amplification or HTS library preparation stage, was developed to increase the ability of virome characterization. This new approach has the potential to further transform the field of virus discovery and virome analysis, but its technical complexity and sequence-dependence warrants further improvements. In this review we discuss the different methods, their applications and evolution, for selective sequencing based virome analysis and also propose refinements needed to harness the full potential of HTS for virome analysis.