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The changes occurring in viral quasispecies populations during infection have been monitored using diversity indices, nucleotide diversity, and several other indices to summarize the quasispecies structure in a single value. In this study, we present a method to partition quasispecies haplotypes into four fractions according to their fitness: the master haplotype, rare haplotypes at two levels (those present at 1%, but less than that of the master haplotype. We propose that by determining the changes occurring in the volume of the four quasispecies fitness fractions together with those of the Hill number profile we will be able to visualize and analyze the molecular changes in the composition of a quasispecies with time. To develop this concept, we used three data sets: a technical clone of the complete SARS-CoV-2 spike gene, a subset of data previously used in a study of rare haplotypes, and data from a clinical follow-up study of a patient chronically infected with HEV and treated with ribavirin. The viral response to ribavirin mutagenic treatment was selection of a rich set of synonymous haplotypes. The mutation spectrum was very complex at the nucleotide level, but at the protein (phenotypic/functional) level the pattern differed, showing a highly prevalent master phenotype. We discuss the putative implications of this observation in relation to mutagenic antiviral treatment., This study was partially supported by Plan Estratègic de Recerca i Innovació en Salut (PERIS)—Direcció General de Recerca i Innovació en Salut (DGRIS), Catalan Health Ministry, Generalitat de Catalunya; Centro para el Desarrollo Tecnológico Industrial (CDTI) from the Spanish Ministry of Economy and Business, grant number IDI-20200297; grant PI19/00301 from Instituto de Salud Carlos III cofinanced by the European Regional Development Fund (ERDF), and Gilead’s biomedical research project GLD21/00006. Work at CBMSO in Madrid was supported by grant PID2020-113888RB-100 from Ministerio de Ciencia e Innovación and S2018/BAA-4370 (PLATESA2 from Comunidad de Madrid/FEDER).

SARS-CoV-2; Mutacions; Quasiespècie SARS-CoV-2; Mutaciones; Cuasiespecie SARS-CoV-2; Mutations; Quasispecies A common trait among RNA viruses is their high capability to acquire genetic variability due to viral and host mechanisms. Next-generation sequencing (NGS) analysis enables the deep study of the viral quasispecies in samples from infected individuals. In this study, the viral quasispecies complexity and single nucleotide polymorphisms of the SARS-CoV-2 spike gene of coronavirus disease 2019 (COVID-19) patients with mild or severe disease were investigated using next-generation sequencing (Illumina platform). SARS-CoV-2 spike variability was higher in patients with long-lasting infection. Most substitutions found were present at frequencies lower than 1%, and had an A → G or T → C pattern, consistent with variants caused by adenosine deaminase acting on RNA-1 (ADAR1). ADAR1 affected a small fraction of replicating genomes, but produced multiple, mainly non-synonymous mutations. ADAR1 editing during replication rather than the RNA-dependent RNA polymerase (nsp12) was the predominant mechanism generating SARS-CoV-2 genetic variability. However, the mutations produced are not fixed in the infected human population, suggesting that ADAR1 may have an antiviral role, whereas nsp12-induced mutations occurring in patients with high viremia and persistent infection are the main source of new SARS-CoV-2 variants. This study was supported by the Direcció General de Recerca i Innovació en Salut (DGRIS) of the Catalan Health Ministry, Generalitat de Catalunya, through the Vall d’Hebron Institut de Recerca (VHIR); the European Regional Development Fund (ERDF) “A way to achieve Europe” by the Spanish Network for Research in Infectious Diseases [grant number REIPI RD16/0016/0003]; Instituto de Salud Carlos III [grant number FIS PI19/00301]; and Centro para el Desarrollo Tecnologico Industrial (CDTI) from the Ministry of Economic Affairs and Digital Transformation [grant number IDI-20200297].

Eva Dopico,1,2 Francisco Rodriguez-Frias,3– 5 Itziar Ubillos,6 Ariadna Rando-Segura,3 Damir Garcia-Cehic,4,7 Josep Gregori,4,7 Yolanda Rando-Matos,8,9 Luis Solsona,8,9 Jordi Niubó,1,2 Juan Ignacio Esteban,4,7 Josep Costa,4,10 Miguel J Martínez,10,11 Josep Quer4,5,7 1Microbiology Department, Laboratori Clínic Territorial Metropolitana Sud, Hospital Universitari de Bellvitge, Institut Català de la Salut (ICS), Hospitalet de Llobregat, Barcelona, Spain; 2Bellvitge Biomedical Research Institute (IDIBELL), L’Hospitalet de Llobregat, Barcelona, Spain; 3Biochemistry Department, Vall d’Hebron Institut de Recerca (VHIR), Vall d’Hebron Hospital Universitari, Vall d’Hebron Barcelona Hospital Campus, Barcelona, Spain; 4Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Madrid, Spain; 5Biochemistry and Molecular Biology Department, Universitat Autònoma de Barcelona (UAB), Bellaterra, Spain; 6Laboratory Clínic Territorial Metropolitana Sud, Institut Català de la Salut (ICS), Hospitalet de Llobregat, Barcelona, Spain; 7Liver Diseases-Viral Hepatitis, Liver Unit, Vall d’Hebron Institut de Recerca (VHIR), Vall d’Hebron Hospital Universitari, Vall d’Hebron Barcelona Hospital Campus, Barcelona, Spain; 8Equip d’Atenció Primà ria Florida Nord, Gerència d’Àmbit d’Atenció Primà ria Metropolitana Sud, Institut Català de la Salut (ICS), Hospitalet de Llobregat, Barcelona, Spain; 9Fundació Institut Universitari per a la recerca a l’Atenció Primà ria de Salut Jordi Gol i Gurina (IDIAPJGol), Barcelona, Spain; 10Microbiology Department, Hospital Clínic, University of Barcelona, Barcelona, Spain; 11ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, SpainCorrespondence: Josep Quer, Liver Diseases-Viral Hepatitis, Liver Unit, Vall d’Hebron Institut de Recerca (VHIR), Vall d’Hebron Hospital Universitari, Vall d’Hebron Barcelona Hospital Campus, Barcelona, Spain, Tel +34 934894034, Email josep.quer@vhir.org Miguel J Martínez, Microbiology Department, Hospital Clínic, University of Barcelona, Barcelona, Spain, Email MYOLDI@clinic.catBackground: Hepatitis C virus (HCV) is a major cause of chronic liver infection with 71 million people infected worldwide. Pakistan has the second highest prevalence of HCV infection and more than half (52%) of Pakistani living in Spain reside in Barcelona. The aim of this study was to analyse the seroprevalence and viraemic rate and determine the genotypes and subtypes of HCV among Pakistanis living in the southern metropolitan area of Barcelona.Methods: We included all Pakistani patients seeking primary healthcare in the southern metropolitan area of Barcelona from August 2011 to July 2014. Serum samples were screened for HCV antibodies. HCV viral load was determined by reverse transcription polymerase chain reaction and genotypes and subtypes were performed using Versant HCV Genotype and/or deep-sequencing. Screening for hepatitis B virus (HBV) was also carried out.Results: Among 5877 Pakistani patients, 565 (9.61%) were screened for anti-HCV antibodies, with 68 (12.04%) being positive. The viral load was determined in 65, with 31 presenting active infection and the viraemic rate was 47.69% (95% confidence interval 36.02– 59.62). HCV genotyping and subtyping were performed in 24 individuals. Most infections corresponded to HCV genotype 3 (91.67%), and high resolution HCV subtyping was performed in 18 samples, 16 of which presented subtype 3a. One subject presented HBV coinfection with undetectable HBV DNA. During the study period, we identified a possible case of HCV vertical transmission followed by spontaneous viraemia clearance in a chronically infected mother with a C/T IL28B genetic polymorphism.Conclusion: These results suggest that general HCV screening protocols in patients from high prevalence countries, such as Pakistan, would be helpful to identify and treat active HCV infections. This could avoid further transmission and contribute to building targeted health policies for micro-elimination of HCV infection in specific communities.Keywords: hepatitis C virus, migrants, HCV genotype, HCV subtype

Fibrosis; Hepatitis C virus; Viral load Fibrosis; Virus de la hepatitis C; Carga viral Fibrosi; Virus de l'hepatitis C; Càrrega viral Cirrhosis derived from chronic hepatitis C virus (HCV) infection is still a common indication for liver transplantation (LT). Reinfection of the engrafted liver is universal in patients with detectable viral RNA at the time of transplant and causes fast progression of cirrhosis (within 5 years) in around one-third of these patients. To prevent damage to the liver graft, effective direct-acting antiviral (DAA) therapy is required as soon as possible. However, because of post-LT clinical instability, it is difficult to determine the optimal time to start DAAs with a low risk of complications. Evaluate changes in quasispecies complexity following LT and seek a predictive index of fast liver damage progression to determine the timing of DAA initiation. HCV genomes isolated from pre-LT and 15-day post-LT serum samples of ten patients, who underwent orthotopic LT, were quantified and sequenced using a next-generation sequencing platform. Sequence alignments, phylogenetic trees, quasispecies complexity measures, biostatistics analyses, adjusted R2 values, and analysis of variance (ANOVA) were carried out. Three different patterns of reinfection were observed (viral bottlenecking, conserved pre-LT population, and mixed populations), suggesting that bottlenecking or homogenization of the viral population is not a generalized effect after liver graft reinfection. None of the quasispecies complexity measures predicted the future degree of liver damage. Higher and more uniform viral load (VL) values were observed in all pre-LT samples, but values were more dispersed in post-LT samples. However, VL increased significantly from the pre-LT to 15-day post-LT samples in patients with advanced fibrosis at 1-year post-LT, suggesting that a VL increase on day 15 may be a predictor of fast liver fibrosis progression. HCV kinetics after LT differ between patients and are not fibrosis-dependent. Higher VL at day 15 post-LT versus pre-LT samples may predict fast liver fibrosis progression. This study was supported by grants from Instituto de Salud Carlos III cofinanced by the European Regional Development Fund (ERDF) with grant numbers PI19/00533, PI19/00301, Clinical Trial Gov. Identifier: NCT01707849, and from Centro para el Desarrollo Tecnológico Industrial-CDTI of the Spanish Ministry of Economics and Competitiveness (MINECO) grant number, IDI-20200297. C.P. is supported by the Miguel Servet program of Instituto de Salud Carlos III, grant CP14/00121, cofinanced by the ERDF. Astellas Pharma Inc and Novartis Pharma also provided funding for the study, but these companies had had no role in the study design, data collection or analysis, decision to publish, or preparation of the manuscript.

Since its first identification in the United Kingdom in late 2020, the highly transmissible B.1.1.7 variant of SARS-CoV-2 has become dominant in several countries raising great concern. We developed a duplex real-time RT-qPCR assay to detect, discriminate, and quantitate SARS-CoV-2 variants containing one of its mutation signatures, the ΔHV69/70 deletion, and used it to trace the community circulation of the B.1.1.7 variant in Spain through the Spanish National SARS-CoV-2 Wastewater Surveillance System (VATar COVID-19). The B.1.1.7 variant was detected earlier than clinical epidemiological reporting by the local authorities, first in the southern city of Málaga (Andalucía) in week 20_52 (year_week), and multiple introductions during Christmas holidays were inferred in different parts of the country. Wastewater-based B.1.1.7 tracking showed a good correlation with clinical data and provided information at the local level. Data from wastewater treatment plants, which reached B.1.1.7 prevalences higher than 90% for ≥2 consecutive weeks showed that 8.1 ± 2.0 weeks were required for B.1.1.7 to become dominant. The study highlights the applicability of RT-qPCR-based strategies to track specific mutations of variants of concern as soon as they are identified by clinical sequencing and their integration into existing wastewater surveillance programs, as a cost-effective approach to complement clinical testing during the COVID-19 pandemic., This work was partially supported by the COVID-19 wastewater surveillance project (VATar COVID19), funded by the Spanish Ministry for the Ecological Transition and the Demographic Challenge and the Spanish Ministry of Health, grants from CSIC (202070E101) and MICINN cofounded by AEI FEDER, UE (AGL2017-82909), grant ED431C 2018/18 from the Consellería de Educación, Universidade e Formación Profesional, Xunta de Galicia (Spain), Direcció General de Recerca i Innovació en Salut (DGRIS) Catalan Health Ministry Generalitat de Catalunya through Vall d’Hebron Research Institute (VHIR), and Centro para el Desarrollo Tecnológico Industrial (CDTI) from the Spanish Ministry of Economy and Business, grant number IDI-20200297. P.T. is holding a Ramón y Cajal contract from the Ministerio de Ciencia e Innovación. A.M. is holding a predoctoral fellowship FI_SDUR from Generalitat de Catalunya. We gratefully acknowledge all the staff involved in the VATar COVID-19 project, working with sample collection and logistics. The authors are grateful to Promega Corporation (Madison, US) for technical advice and thank Andrea Lopez de Mota for her technical support.

Purpose To study resistance-associated substitutions using next-generation sequencing in Egyptian hepatitis C virus-infected patients failing direct-acting antiviral treatment. Methods The current study describes three cases of treatment failure in patients referred to Zagazig Viral Hepatitis Treatment Center (ZVHTC), Sharkia Governorate, Egypt. RAS were identified and characterized using deep sequencing. The first patient had breakthrough while receiving a daclatasvir (DCV)+sofosbuvir (SOF) regimen, patient 2 relapsed after treatment with DCV+SOF+ribavirin (RBV), and patient 3 relapsed after DCV+SOF therapy. A serum sample was collected from each patient at failure and sent to Vall d'Hebron Research Institute at Hospital Universitari Vall d'Hebron in Barcelona (Spain) for deep-sequencing study to identify and characterize the RAS present in the samples. Results The following were identified: L28M, L30S and L28M+L30S in patient 1, L30R in patient 2, and R155C, D168E, L28M, L30H, L30S, L28M+L30H, and L28M+L30S in patient 3. Conclusion To the best of our knowledge, this is the first report from Egypt of patients failing DAA-based therapy, describing the associated RAS. This information will be of help to understand the natural history of HCV in Egyptian patients and guide the proper choice of retreatment protocols.

Hepatitis C virus (HCV) is a highly variable infectious agent, classified into 8 genotypes and 86 subtypes. Our laboratory has implemented an in-house developed high-resolution HCV subtyping method based on next-generation sequencing (NGS) for error-free classification of the virus using phylogenetic analysis and analysis of genetic distances in sequences from patient samples compared to reference sequences. During routine diagnostic, a sample from an Equatorial Guinea patient could not be classified into any of the existing subtypes. The whole genome was analyzed to confirm that the new isolate could be classified as a new HCV subtype. In addition, naturally occurring resistance-associated substitutions (RAS) were analyzed by NGS. Whole-genome analysis based on p-distances suggests that the sample belongs to a new HCV genotype 1 subtype. Several RAS in the NS3 (S122T, D168E and I170V) and NS5A protein (Q(1b)24K, R(1b)30Q and Y93L+Y93F) were found, which could limit the use of some inhibitors for treating this subtype. RAS studies of new subtypes are of great interest for tailoring treatment, as no data on treatment efficacy are reported. In our case, the patient has not yet been treated, and the RAS report will be used to design the most effective treatment.

Background Since its first identification in the United Kingdom in late 2020, the highly transmissible B.1.1.7 variant of SARS-CoV-2, become dominant in several European countries raising great concern. Aim The aim of this study was to develop a duplex real-time RT-qPCR assay to detect, discriminate and quantitate SARS-CoV-2 variants containing one of its mutation signatures, the ΔHV69/70 deletion, to trace the community circulation of the B.1.1.7 variant in Spain through the Spanish National SARS-CoV-2 Wastewater Surveillance System (VATar COVID-19). Results B.1.1.7 variant was first detected in sewage from the Southern city of Málaga (Andalucía) in week 20_52, and multiple introductions during Christmas holidays were inferred in different parts of the country, earlier than clinical epidemiological reporting by the local authorities. Wastewater-based B.1.1.7 tracking showed a good correlation with clinical data and provided information at the local level. Data from WWTPs which reached B.1.1.7 prevalences higher than 90% for ≥ 2 consecutive weeks showed that 8.1±1.8 weeks were required for B.1.1.7 to become dominant. Conclusion The study highlights the applicability of RT-qPCR-based strategies to track specific mutations of variants of concern (VOCs) as soon as they are identified by clinical sequencing, and its integration into existing wastewater surveillance programs, as a cost-effective approach to complement clinical testing during the COVID-19 pandemic., This work was partially supported by the COVID-19 wastewater surveillance project (VATar COVID19), funded by the Spanish Ministry for the Ecological Transition and the Demographic Challenge of and the Spanish Ministry of Health; grants from CSIC (202070E101) and MICINN co-founded by AEI FEDER, UE (AGL2017-82909); grant ED431C 2018/18 from the Conselleria de Educacion, Universidade e Formacion Profesional, Xunta de Galicia (Spain); Direccio General de Recerca i Innovacio en Salut (DGRIS) Catalan Health Ministry Generalitat de Catalunya through Vall de Hebron Research Institute (VHIR), and Centro para el Desarrollo Tecnologico Industrial (CDTI) from the Spanish Ministry of Economy and Business, grant number IDI-20200297. Pilar Truchado is holding a Ramon y Cajal contract from the Ministerio de Ciencia e Innovacion. Adan Martinez is holding a predoctoral fellowship FI_SDUR from Generalitat de Catalunya. We gratefully acknowledge all the staff involved in the VATar COVID-19 project, working with sample collection and logistics. The authors are grateful to Promega Corporation (Madison, US) for technical advice, and thank Andrea Lopez de Mota for her technical support.

Wastewater based epidemiology (WBE) offers an overview of the SARS-CoV-2 variants circulating among the population thereby serving as a proper surveillance method. The variant of concern (VOC) Alpha was first identified in September 2020 in the United Kingdom, and rapidly became dominant across Europe. Our objective was to elucidate the Alpha VOC outcompetition rate and identify mutations in the spike glycoprotein (S) gene, indicative of the circulation of the Alpha VOC and/or other variants in the population through wastewater analysis. In the period covered by this study (November 2020–April 2021), forteen wastewater treatment plants (WWTPs) were weekly sampled. The total number of SARS-CoV-2 genome copies per L (GC/L) was determined with a Real-Time qPCR, targeting the N gene. Surveillance of the Alpha VOC circulation was ascertained using a duplex RT-qPCR, targeting and discriminating the S gene. Our results showed that in a period of 6 weeks the Alpha VOC was present in all the studied WWTPs, and became dominant in 11 weeks on average. The outcompetition rates of the Alpha VOC were estimated, and their relationship with different parameters statistically analyzed. The rapid spread of the Alpha VOC was influenced by its initial input and by the previous circulation of SARS-COV-2 in the population. This latter point could be explained by its higher transmissibility, particularly advantadgeous when a certain degree of herd immunity exists. Moreover, the presence of signature mutations of SARS-COV-2 variants were established by deep-sequencing of the complete S gene. The circulation of the Alpha VOC in the area under study was confirmed, and additionally two combinations of mutations in the S glycoprotein (T73A and D253N, and S477N and A522S) that could affect antibody binding were identified., Graphical abstract Image 1

[Abstract] A percentage of hepatitis C virus (HCV)-infected patients fail direct acting antiviral (DAA)-based treatment regimens, often because of drug resistance-associated substitutions (RAS). The aim of this study was to characterize the resistance profile of a large cohort of patients failing DAA-based treatments, and investigate the relationship between HCV subtype and failure, as an aid to optimizing management of these patients. A new, standardized HCV-RAS testing protocol based on deep sequencing was designed and applied to 220 previously subtyped samples from patients failing DAA treatment, collected in 39 Spanish hospitals. The majority had received DAA-based interferon (IFN) α-free regimens; 79% had failed sofosbuvir-containing therapy. Genomic regions encoding the nonstructural protein (NS) 3, NS5A, and NS5B (DAA target regions) were analyzed using subtype-specific primers. Viral subtype distribution was as follows: genotype (G) 1, 62.7%; G3a, 21.4%; G4d, 12.3%; G2, 1.8%; and mixed infections 1.8%. Overall, 88.6% of patients carried at least 1 RAS, and 19% carried RAS at frequencies below 20% in the mutant spectrum. There were no differences in RAS selection between treatments with and without ribavirin. Regardless of the treatment received, each HCV subtype showed specific types of RAS. Of note, no RAS were detected in the target proteins of 18.6% of patients failing treatment, and 30.4% of patients had RAS in proteins that were not targets of the inhibitors they received. HCV patients failing DAA therapy showed a high diversity of RAS. Ribavirin use did not influence the type or number of RAS at failure. The subtype-specific pattern of RAS emergence underscores the importance of accurate HCV subtyping. The frequency of “extra-target” RAS suggests the need for RAS screening in all three DAA target regions. Ministerio de Economía y Empresa; IDI-20151125 Ministerio de Ciencia, Innovación y Universidades; SAF SAF 2017-87846-R

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. Identification of amino acid substitutions associated with treatment failure requires analytical designs, such as subtype-specific ultra-deep 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 from 220 patients who failed therapy, which are not bona fide resistance-associated substitutions (RAS). They were present frequently in basal and post-treatment virus of patients who failed therapy to different DAA-based therapies. Contrary to several RAS, HRSs belong to the acceptable subset of substitutions according to the PAM250 replacement matrix. Coherently, 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. Also, they 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 of treatment response are discussed.

The SARS-CoV-2 spike (S) protein, the viral mediator for binding and entry into the host cell, has sparked great interest as a target for vaccine development and treatments with neutralizing antibodies. Initial data suggest that the virus has low mutation rates, but its large genome could facilitate recombination, insertions, and deletions, as has been described in other coronaviruses. Here, we deep-sequenced the complete SARS-CoV-2 S gene from 18 patients (10 with mild and 8 with severe COVID-19), and found that the virus accumulates deletions upstream and very close to the S1/S2 cleavage site, generating a frameshift with appearance of a stop codon. These deletions were found in a small percentage of the viral quasispecies (2.2%) in samples from all the mild and only half the severe COVID-19 patients. Our results suggest that the virus may generate free S1 protein released to the circulation. We propose that natural selection has favored a “Don’t burn down the house” strategy, in which free S1 protein may compete with viral particles for the ACE2 receptor, thus reducing the severity of the infection and tissue damage without losing transmission capability.

The SARS-CoV-2 spike (S) protein, the viral mediator for binding and entry into the host cell, has sparked great interest as a target for vaccine development and treatments with neutralizing antibodies. Initial data suggest that the virus has low mutation rates, but its large genome could facilitate recombination, insertions, and deletions, as has been described in other coronaviruses. Here, we deep-sequenced the complete SARS-CoV-2 S gene from 18 patients (10 with mild and 8 with severe COVID-19), and found that the virus accumulates deletions upstream and very close to the S1/S2 cleavage site (PRRAR/S), generating a frameshift with appearance of a stop codon. These deletions were found in a small percentage of the viral quasispecies (2.2%) in samples from all the mild and only half the severe COVID-19 patients. Our results suggest that the virus may generate free S1 protein released to the circulation. We suggest that natural selection has favoured a “Don’t burn down the house” strategy, in which free S1 protein may compete with viral particles for the ACE2 receptor, thus reducing the severity of the infection and tissue damage without losing transmission capability.

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., The work at CBMSO was supported by grants SAF2014-52400-R from Ministerio de Economía y Competitividad (MINECO), SAF2017-87846-R and BFU2017-91384-EXP from Ministerio de Ciencia, Innovación y Universidades (MICIU), PI18/00210 from Instituto de Salud Carlos III, S2013/ABI-2906 (PLATESA from Comunidad de Madrid/FEDER), and S2018/BAA-4370 (PLATESA2 from Comunidad de Madrid/FEDER). C.P. is supported by the Miguel Servet program of the Instituto de Salud Carlos III (CP14/00121 and CPII19/00001), cofinanced by the European Regional Development Fund (ERDF). CIBERehd (Centro de Investigación en Red de Enfermedades Hepáticas y Digestivas) is funded by Instituto de Salud Carlos III. Institutional grants from the Fundación Ramón Areces and Banco Santander to the CBMSO are also acknowledged. The team at CBMSO belongs to the Global Virus Network (GVN). The work in Barcelona was supported by Instituto de Salud Carlos III, cofinanced by the European Regional Development Fund (ERDF) grant number PI19/00301 and by the Centro para el Desarrollo Tecnológico Industrial (CDTI) from the MICIU, grant number IDI-20151125. Work at CAB was supported by MINECO grant BIO2016-79618R and PID2019-104903RB-I00 (funded by the EU under the FEDER program) and by the Spanish State research agency (AEI) through project number MDM-2017-0737 Unidad de Excelencia “María de Maeztu”-Centro de Astrobiología (CSIC-INTA). Work at IBMB was supported by MICIN grant BIO2017-83906-P (funded by the EU under the FEDER program). C.G.-C. is supported by predoctoral contract PRE2018-083422 from MICIU. B.M.-G. is supported by predoctoral contract PFIS FI19/00119 from Instituto de Salud Carlos III (Ministerio de Sanidad y Consumo), cofinanced by Fondo Social Europeo (FSE).

Previous studies documented that long-term hepatitis C virus (HCV) replication in human hepatoma Huh-7.5 cells resulted in viral fitness gain, expansion of the mutant spectrum, and several phenotypic alterations. In the present work, we show that mutational waves (changes in frequency of individual mutations) occurred continuously and became more prominent as the virus gained fitness. They were accompanied by an increasing proportion of heterogeneous genomic sites that affected 1 position in the initial HCV population and 19 and 69 positions at passages 100 and 200, respectively. Analysis of biological clones of HCV showed that these dynamic events affected infectious genomes, since part of the fluctuating mutations became incorporated into viable genomes. While 17 mutations were scored in 3 biological clones isolated from the initial population, the number reached 72 in 3 biological clones from the population at passage 200. Biological clones differed in their responses to antiviral inhibitors, indicating a phenotypic impact of viral dynamics. Thus, HCV adaptation to a specific constant environment (cell culture without external influences) broadens the mutant repertoire and does not focus the population toward a limited number of dominant genomes. A retrospective examination of mutant spectra of foot-and-mouth disease virus passaged in cell cultures suggests a parallel behavior here described for HCV. We propose that virus diversification in a constant environment has its basis in the availability of multiple alternative mutational pathways for fitness gain. This mechanism of broad diversification should also apply to other replicative systems characterized by high mutation rates and large population sizes. IMPORTANCE The study shows that extensive replication of an RNA virus in a constant biological environment does not limit exploration of sequence space and adaptive options. There was no convergence toward a restricted set of adapted genomes. Mutational waves and mutant spectrum broadening affected infectious genomes. Therefore, profound modifications of mutant spectrum composition and consensus sequence diversification are not exclusively dependent on environmental alterations or the intervention of population bottlenecks., The work at CBMSO was supported by grants SAF2014-52400-R from Ministerio de Economía y Competitividad (MINECO); SAF2017-87846-R and BFU2017-91384-EXP from Ministerio de Ciencia, Innovación y Universidades (MICIU); and S2013/ABI-2906 (PLATESA from Comunidad de Madrid [CAM]/FEDER), S2018/BAA-4370 (PLATESA2 from CAM/FEDER), and PI18/00210 from Instituto de Salud Carlos III. C.P. is supported by the Miguel Servet program of the Instituto de Salud Carlos III (CP14/00121), cofinanced by the European Regional Development Fund (ERDF). CIBERehd is funded by Instituto de Salud Carlos III. Institutional grants from the Fundación Ramón Areces and Banco Santander to the CBMSO are also acknowledged. The team at CBMSO belongs to the Global Virus Network (GVN). The work in Barcelona was supported by Instituto de Salud Carlos III, cofinanced by the European Regional Development Fund (ERDF) (grant numbers PI16/00337) and by the Centro para el Desarrollo Tecnológico Industrial (CDTI) from the Spanish Ministry of Economy and Business (grant number IDI-20151125). Work at CAB was supported by MINECO grant BIO2016-79618-R (funded by the European Union under the FEDER program) and by the Spanish State Research Agency (AEI) through project number MDM-2017-0737 Unidad de Excelencia “María de Maeztu”-Centro de Astrobiologia (CSIC-INTA).

[Background] Despite the high sustained virological response rates achieved with current directly-acting antiviral agents (DAAs) against hepatitis C virus (HCV), around 5–10% of treated patients do not respond to current antiviral therapies, and basal resistance to DAAs is increasingly detected among treatment-naïve infected individuals. Identification of amino acid substitutions (including those in minority variants) associated with treatment failure requires analytical designs that take into account the high diversification of HCV in more than 86 subtypes according to the ICTV website (June 2017)., [Methods] The methodology has involved five sequential steps: (i) to design 280 oligonucleotide primers (some including a maximum of three degenerate positions), and of which 120 were tested to amplify NS3, NS5A-, and NS5B-coding regions in a subtype-specific manner, (ii) to define a reference sequence for each subtype, (iii) to perform experimental controls to define a cut-off value for detection of minority amino acids, (iv) to establish bioinformatics’ tools to quantify amino acid replacements, and (v) to validate the procedure with patient samples., [Results] A robust ultra-deep sequencing procedure to analyze HCV circulating in serum samples from patients infected with virus that belongs to the ten most prevalent subtypes worldwide: 1a, 1b, 2a, 2b, 2c, 2j, 3a, 4d, 4e, 4f has been developed. Oligonucleotide primers are subtype-specific. A cut-off value of 1% mutant frequency has been established for individual mutations and haplotypes., [Conclusion] The methodological pipeline described here is adequate to characterize in-depth mutant spectra of HCV populations, and it provides a tool to understand HCV diversification and treatment failures. The pipeline can be periodically extended in the event of HCV diversification into new genotypes or subtypes, and provides a framework applicable to other RNA viral pathogens, with potential to couple detection of drug-resistant mutations with treatment planning., This study was supported by the Spanish Health Ministry (Plan Estratégico Nacional contra la Hepatitis C). The work in Barcelona was also funded by Instituto de Salud Carlos III; by grants PI13/00456, PI15/00829, and PI16/ 00337 cofinanced by the European Regional Development Fund (ERDF); and by CDTI (Centro para el Desarrollo Tecnológico Industrial), Spanish Ministry of Economics and Competitiveness (MINECO), IDI-20151125. C.P. is supported by the Miguel Servet program of the Instituto de Salud Carlos III (CP14/ 00121) cofinanced by the European Regional Development Fund (ERDF). CIBERehd (Centro de Investigación en Red de Enfermedades Hepáticas y Digestivas) is funded by Instituto de Salud Carlos III. The work in Madrid was supported by grants BFU2011–23604, SAF2014–52400-R, SAF2017–87846-R and S2013/ABI-2906 (PLATESA from Comunidad Autónoma de Madrid/ FEDER). Institutional grants from the Fundación Ramón Areces and Banco Santander to the CBMSO are also acknowledged.

Hepatitis C virus (HCV) is a highly divergent virus currently classified into seven major genotypes and 86 subtypes (ICTV, June 2017), which can have differing responses to therapy. Accurate genotyping/subtyping using high-resolution HCV subtyping enables confident subtype identification, identifies mixed infections and allows detection of new subtypes. During routine genotyping/subtyping, one sample from an Equatorial Guinea patient could not be classified into any of the subtypes. The complete genomic sequence was compared to reference sequences by phylogenetic and sliding window analysis. Resistance-associated substitutions (RASs) were assessed by deep sequencing. The unclassified HCV genome did not belong to any of the existing genotype 1 (G1) subtypes. Sliding window analysis along the complete genome ruled out recombination phenomena suggesting that it belongs to a new HCV G1 subtype. Two NS5A RASs (L31V+Y93H) were found to be naturally combined in the genome which could limit treatment possibilities in patients infected with this subtype.

Cholestatic hepatitis C (CHC) is a severe form of hepatitis C virus (HCV) infection recurrence that leads to high graft loss rates early after liver transplantation (LT). To investigate the pathogenic mechanisms of CHC, we analysed HCV quasispecies in CHC patients compared to a control group (mild hepatitis C recurrence) by deep pyrosequencing. At the time of LT, NS5B quasispecies complexity was similar between the two groups but, after LT, it decreased more sharply in CHC patients than in the control group. Interestingly, the major variant before LT propagated efficiently and remained as the dominant sequence after LT in 62 % of CHC patients versus 11 % of controls (P=0.031). Sequence analysis of the complete non-structural region in a limited number of patients revealed a potential 12 aa signature specific to the CHC group. These data suggest that intrinsic molecular determinants in the circulating HCV quasispecies may provide a fitness advantage, contributing to the development of CHC.

Background A huge outbreak in the men-having-sex-with-men (MSM) has hit Europe during the years 2016–2018. Outbreak control has been hampered by vaccine shortages in many countries, and to minimize their impact, reduction of antigen doses has been implemented. However, these measures may have consequences on the evolution of hepatitis A virus (HAV), leading to the emergence of antigenic variants. Cases in vaccinated MSM patients have been detected in Barcelona, opening the possibility to study HAV evolution under immune pressure. Methods We performed deep-sequencing analysis of ten overlapping fragments covering the complete capsid coding region of HAV. A total of 14578255 reads were obtained and used for the analysis of virus evolution in vaccinated versus non-vaccinated patients. We estimated maximum and minimum mutation frequencies, and Shannon entropy in the quasispecies of each patient. Non-synonymous (NSyn) mutations affecting residues exposed in the capsid surface were located, with respect to epitopes, using the recently described crystal structure of HAV, as an indication of its potential role in escaping to the effect of vaccines. Findings HAV evolution at the quasispecies level, in non-vaccinated and vaccinated patients, revealed higher diversity in epitope-coding regions of the vaccinated group. Although amino acid replacements occurring in and around the epitopes were observed in both groups, their abundance was significantly higher in the quasispecies of vaccinated patients, indicating ongoing processes of fixation. Interpretation Our data suggest positive selection of antigenic variants in some vaccinated patients, raising concerns for new vaccination polices directed to the MSM group.

One unexplored aspect of HIV-1 genetic architecture is how codon choice influences population diversity and evolvability. Here we compared the development of HIV-1 resistance to protease inhibitors (PIs) between wild-type (WT) virus and a synthetic virus (MAX) carrying a codon-pair re-engineered protease sequence including 38 (13%) synonymous mutations. WT and MAX viruses showed indistinguishable replication in MT-4 cells or PBMCs. Both viruses were subjected to serial passages in MT-4 cells with selective pressure from the PIs atazanavir (ATV) and darunavir (DRV). After 32 successive passages, both the WT and MAX viruses developed phenotypic resistance to PIs (IC5014.6 ± 5.3 and 21.2 ± 9 nM for ATV, and 5. 9 ± 1.0 and 9.3 ± 1.9 for DRV, respectively). Ultra-deep sequence clonal analysis revealed that both viruses harbored previously described resistance mutations to ATV and DRV. However, the WT and MAX virus proteases showed different resistance variant repertoires, with the G16E and V77I substitutions observed only in WT, and the L33F, S37P, G48L, Q58E/K, and L89I substitutions detected only in MAX. Remarkably, G48L and L89I are rarely foundin vivoin PI-treated patients. The MAX virus showed significantly higher nucleotide and amino acid diversity of the propagated viruses with and without PIs (P< 0.0001), suggesting higher selective pressure for change in this recoded virus. Our results indicate that HIV-1 protease position in sequence space delineates the evolution of its mutant spectra. Nevertheless, the investigated synonymously recoded variant showed mutational robustness and evolvability similar to the WT virus.IMPORTANCELarge-scale synonymous recoding of virus genomes is a new tool for exploring various aspects of virus biology. Synonymous virus genome recoding can be used to investigate how a virus’s position in sequence space defines its mutant spectrum, evolutionary trajectory, and pathogenesis. In this study, we evaluated how synonymous recoding of the human immunodeficiency virus type 1 (HIV-1) protease impacts the development of protease inhibitor (PI) resistance. HIV-1 protease is a main target of current antiretroviral therapies. Our present results demonstrate that the wild-type (WT) virus and the virus with the recoded protease exhibited different patterns of resistance mutations after PI treatment. Nevertheless, the developed PI resistance phenotype was indistinguishable between the recoded virus and the WT virus, suggesting that the synonymously recoded protease HIV-1 and the WT protease virus were equally robust and evolvable.

Background: Controversy is ongoing about whether a minority mutant present at frequencies below 15% may be clinically relevant and should be considered to guide treatment. Methods: Resistance-associated substitution (RAS) studies were performed in patients before and at failure of antiviral treatments using Next-generation hepatitis C virus (HCV) sequencing (NGS). Results: We have found two patients with genotype 1a infection having RAS in 3.5%–7.1% of the viral population at baseline that were selected during ledipasvir + sofosbuvir treatment. Co-selection of RAS located in a region not directly affected by the antiviral treatment also occurred. This observation calls into question, the recommendations to guide RAS-based direct-acting antiviral (DAA) treatment only when RAS are present in >15% of the sequences generated. Conclusion: Our results suggests that RAS study should include all three HCV DAA target proteins and minority mutants should be considered as clinically relevant., Ministerio de Sanidad, Servicios Sociales e Igualdad grant name “Plan Estratégico Nacional contra la Hepatitis C”; Instituto de Salud Carlos III cofinanced by the European Regional Development Fund (ERDF) grant number PI16/00337; and Centro para el Desarrollo Tecnológico Industrial-CDTI from the Spanish Ministry of Economics and Competitiveness (MINECO) grant number IDI-20151125. Work at CSIC-UAM supported by grants SAF2014-52400-R, SAF2017-87846-R from MINECO; S2013/ABI-2906 (PLATESA from Comunidad Autónoma de Madrid/FEDER), and institutional grants from Fundación Ramón Areces and Banco Santander

The allocation of liver grafts from hepatitis C virus (HCV)-positive donors in HCV-infected liver transplant (LT) recipients leads to infection with two different viral populations. In a previous study, we examined quasispecies dynamics during reinfection by clonal sequencing, which did not allow an accurate characterization of coexistence and competition events. To overcome this limitation, here we used deep-sequencing analysis of a fragment of the HCV NS5B gene in six HCV-infected LT recipients who received HCV-infected grafts. Successive expansions and contractions of quasispecies complexity were observed, evolving in all cases towards a more homogeneous population. The population that became dominant was the one displaying the highest mutant spectrum complexity. In four patients, coexistence of minority mutants, derived from the donor or the recipient, were detected. In conclusion, our study shows that, during reinfection with a different HCV strain in LT recipients, the viral population with the highest diversity always becomes dominant.

The unequivocal identification of hepatitis C virus (HCV) subtypes 1a/1b and genotypes 2 to 6 is required for optimizing the effectiveness of interferon-free, direct-acting antiviral therapies. We compared the performance of a new real-time HCV genotyping assay used on the Cobas 4800 system (C4800) with that of high-resolution HCV subtyping (HRCS). In total, 502 samples were used, including 184 samples from chronic HCV patients (from routine laboratory activity during April 2016), 5 stored samples with double HCV genotype infections for testing the limitations of the method, and 313 samples from a screening protocol implemented in our hospital (from May to August 2016) based on the new method to further determine its genotyping accuracy. A total of 282 samples, including 171 from April 2016 (the 13 remaining had too low of a viral load for HRCS), 5 selected with double infections, and 106 from screening, were analyzed by both methods, and 220 were analyzed only by the C4800. The C4800 correctly subtyped 125 of 126 1a/1b samples, and the 1 remaining sample was reported as genotype 1. The C4800 correctly genotyped 38 of 45 non-1a/1b samples (classified by HRCS), and it reported the remaining 7 samples as indeterminate. One hundred two of 106 non-1a/1b genotype samples that were identified using the C4800 for screening were confirmed by HRCS. In the 4 remaining samples, 3 were correctly reported as genotype 1 (without defining the subtype) and 1 was reported as indeterminate. None of the samples were misgenotyped. Four of 7 samples with double HCV infections were correctly genotyped by the C4800. Excluding the 5 selected double-infected samples, the C4800 showed 95.7% concordant results for genotyping HCVs 2 to 6 and 1a/1b subtyping, and 99.2% concordance for subtyping 1a/1b single infections in clinical samples. To improve laboratory workflow, we propose using the C4800 as a first-line test for HCV genotyping and 1a/1b classification, followed by transferring non-1a/1b samples to a center where HRCS is available, if further characterization is needed.

AIM: To develop a fast, low-cost diagnostic strategy to identify single point mutations in highly variable genomes such as hepatitis C virus (HCV). METHODS: In patients with HCV infection, resistance-associated amino acid substitutions within the viral quasispecies prior to therapy can confer decreased susceptibility to direct-acting antiviral agents and lead to treatment failure and virological relapse. One such naturally occurring mutation is the Q80K substitution in the HCV-NS3 protease gene, which confers resistance to PI inhibitors, particularly simeprevir. Low-cost, highly sensitive techniques enabling routine detection of these single point mutations would be useful to identify patients at a risk of treatment failure. LightCycler methods, based on real-time PCR with sequence-specific probe hybridization, have been implemented in most diagnostic laboratories. However, this technique cannot identify single point mutations in highly variable genetic environments, such as the HCV genome. To circumvent this problem, we developed a new method to homogenize all nucleotides present in a region except the point mutation of interest. RESULTS: Using nucleotide-specific probes Q, K, and R substitutions at position 80 were clearly identified at a sensitivity of 10% (mutations present at a frequency of at least 10% were detected). The technique was successfully applied to identify the Q80K substitution in 240 HCV G1 serum samples, with performance comparable to that of direct Sanger sequencing, the current standard procedure for this purpose. The new method was then validated in a Catalonian population of 202 HCV G1-infected individuals. Q80K was detected in 14.6% of G1a patients and 0% of G1b in our setting. CONCLUSION: A fast, low-cost diagnostic strategy based on real-time PCR and fluorescence resonance energy transfer probe melting curve analysis has been successfully developed to identify single point mutations in highly variable genomes such as hepatitis C virus. This technique can be adapted to detect any single point mutation in highly variable genomes. Sí

Objectives This study aimed to characterize the chronically infected general hepatitis C virus (HCV) population in Barcelona using a highly sensitive subtyping method that can identify the 67 recognized HCV subtypes and diagnose mixed infection by various genotypes/subtypes in a single individual. The resulting information has implications for selecting optimal direct-acting antiviral (DAA) treatment for each patient and establishing public healthcare policies in our setting. Methods Consecutive HCV patients (treatment-naive or interferon-based failures) attending Vall d'Hebron Hospital outpatient clinics from February 2015 to May 2016 ( N =1473) were included in the study. Patient samples were characterized using HCV subtyping by next-generation ultra-deep pyrosequencing. Results The following genotypes (G) were found: G1 (1126/1473 (76.4%)), G4 (145/1473 (9.8%)), G3 (135/1473 (9.2%)), G2 (51/1473 (3.5%)), and G5 (1/1473 (0.1%)). Twenty-two subtypes were seen: 1b (790/1473 (53.6%)), 1a (332/1473 (22.5%)), 3a (133/1473 (9.0%)), 4d (105/1473 (7.1%)), 4a (29/1473 (2.0%)), and 2c (25/1473 (1.7%)), with 16 low-prevalence subtypes accounting for the remaining 3.0% (44/1473). There was a worrisome 1.0% (15/1473) of mixed infections. G2 (51/1473 (3.5%)) showed a high level of heterogeneity. Analyses by age groups showed a predominance of G1b over G1a (428/506 (84.6%) vs. 24/506 (4.7%)) in patients born before 1950 ( N =506/1473), and similar percentages of these subtypes in those born between 1951 and 1975 ( N =834/1473) (315/834, 37.8% vs. 266/834, 31.9%) and after 1976 ( N =133/1473) (47/133, 35.3% vs. 42/133, 31.6%). Conclusions Subtype distribution showed a higher level of heterogeneity than was expected, particularly for G2. Prevalence of mixed infections was around 1%. HCV subtype distribution related to patient age group suggested that patients born from 1936 to 1975 in our setting should undergo screening for the infection. Next-generation sequencing enabled better classification of candidates for DAA-based treatment.

HepatitisCvirus (HCV)is classified into seven major genotypesand67 subtypes. Recent studies haveshownthat inHCVgenotype 1-infected patients, response rates to regimens containingdirect-acting antivirals(DAAs)are subtype dependent. Currently available genotypingmethods have limited subtyping accuracy.Wehave evaluated theperformanceof adeep-sequencing-basedHCVsubtyping assay, developed for the 454/GS-Junior platform, incomparisonwith thoseof twocommercial assays (VersantHCVgenotype 2.0andAbbott Real-timeHCVGenotype II)andusingdirectNS5Bsequencing as a gold standard (direct sequencing), in 114 clinical specimenspreviously tested by first-generation hybridization assay (82 genotype 1 and32 with uninterpretable results). Phylogenetic analysis of deep-sequencing reads matched subtype 1 callingbypopulation Sanger sequencing (69%1b,31%1a) in81 specimensandidentified amixed-subtype infection (1b/3a/1a) inone sample. Similarly,amongthe 32previously indeterminate specimens, identical genotypeandsubtype results were obtained by directanddeep sequencing inall but four samples with dual infection. In contrast, both VersantHCVGenotype 2.0andAbbott Real-timeHCVGenotype II failed subtype 1 calling in13 (16%)samples eachandwere unable to identify theHCVgenotype and/or subtype inmore thanhalfof the nongenotype 1 samples.Weconcluded that deep sequencing ismore efficient forHCVsubtyping than currently available methods andallows qualitative identificationofmixed infectionsandmay bemorehelpfulwith respect toinforming treatment strategies withnewDAA-containing regimens across allHCVsubtypes

All Rights Reserved. HepatitisCvirus(HCV)is classified into seven major genotypesand67 subtypes. Recent studies haveshownthat inHCVgenotype 1-infected patients, response rates to regimens containingdirect-acting antivirals(DAAs)are subtype dependent. Currently available genotypingmethods have limited subtyping accuracy.Wehave evaluated theperformanceof adeep-sequencing-basedHCVsubtyping assay, developed for the 454/GS-Junior platform, in comparisonwith thoseof two commercial assays (VersantHCVgenotype 2.0andAbbott Real-timeHCVGenotype II)andusingdirectNS5Bsequencing as a gold standard (direct sequencing), in 114 clinical specimenspreviously tested by first-generation hybridization assay (82 genotype 1and32 with uninterpretable results). Phylogenetic analysis of deep-sequencing reads matched subtype 1 callingbypopulation Sanger sequencing(69%1b,31%1a) in 81 specimensandidentified amixed-subtype infection (1b/3a/1a) in one sample. Similarly,amongthe 32previously indeterminate specimens, identical genotypeandsubtype results were obtained by directanddeep sequencing in all but four samples with dual infection. In contrast, both VersantHCVGenotype 2.0andAbbott Real-timeHCVGenotype II failed subtype 1 calling in 13 (16%) samples eachandwere unable to identify theHCVgenotype and/or subtype inmore than half of the nongenotype 1 samples.Weconcluded that deep sequencing ismore efficient forHCVsubtyping than currently available methodsandallows qualitative identificationofmixed infectionsandmay bemorehelpfulwith respect to informing treatment strategies withnewDAA-containing regimens across allHCVsubtypes., This study has been supported by CDTI (Centro para el Desarrollo Tecnológico Industrial), Spanish Ministry of Economics and Competitiveness (MINECO), IDI-20110115; MINECO projects SAF 2009-10403; and also by the Spanish Ministry of Health, Instituto de Salud Carlos III (FIS) projects PI10/01505, PI12/01893, and PI13/00456. CIBERehd is funded by the Instituto de Salud Carlos III, Madrid, Spain. Work at CBMSO was supported by grant MINECO-BFU2011-23604, FIPSE, and Fundación Ramón Areces.

To study the subtype prevalence and the phylogenetic relatedness of hepatitis C virus (HCV) sequences obtained from the Argentine general population, a large cohort of individuals was analyzed.Healthy Argentinian volunteers (n = 6251) from 12 provinces representing all geographical regions of the country were studied. All parents or legal guardians of individuals younger than 18 years provided informed written consent for participation. The corresponding written permission from all municipal authorities was obtained from each city or town where subjects were to be included. HCV RNA reverse transcription-polymerase chain reaction products were sequenced and phylogenetically analyzed. The 5' untranslated region (5'UTR) was used for RNA detection and initial genotype classification. The NS5B polymerase region, encompassing nt 8262-8610, was used for subtyping.An unexpectedly low prevalence of HCV infection in the general population (0.32%) was observed. Our data contrasted with previous studies that reported rates ranging from 1.5% to 2.5%, mainly performed in selected populations of blood donors or vulnerable groups. The latter values are in keeping with the prevalence reported by the 2007 Argentinian HCV Consensus (approximately 2%). HCV subtypes were distributed as follows: 1a (25%), 1b (25%), 2c (25%), 3a (5%), and 2j (5%). Two isolates ascribed either to genotype 1 (5%) or to genotype 3 (5%) by 5'UTR phylogenetic analysis could not be subtyped. Subtype 1a sequences comprised a highly homogeneous population and clustered with United States sequences. Genotype 1b sequences represented a heterogeneous population, suggesting that this genotype might have been introduced from different sources. Most subtype 2c sequences clustered close to the 2c reported from Italy and Southern France.HCV has a low prevalence of 0.32% in the studied general population of Argentina. The pattern of HCV introduction and transmission in Argentina appears to be a consequence of multiple events and different for each subtype.

We have investigated the reliability and reproducibility of HCV viral quasispecies quantification by ultra-deep pyrosequencing (UDPS) methods. Our study has been divided in two parts. First of all, by UDPS sequencing of clone mixes samples we have established the global noise level of UDPS and fine tuned a data treatment workflow previously optimized for HBV sequence analysis. Secondly, we have studied the reproducibility of the methodology by comparing 5 amplicons from two patient samples on three massive sequencing platforms (FLX+, FLX and Junior) after applying the error filters developed from the clonal/control study. After noise filtering the UDPS results, the three replicates showed the same 12 polymorphic sites above 0.7%, with a mean CV of 4.86%. Two polymorphic sites below 0.6% were identified by two replicates and one replicate respectively. A total of 25, 23 and 26 haplotypes were detected by GS-Junior, GS-FLX and GSFLX+. The observed CVs for the normalized Shannon entropy (Sn), the mutation frequency (Mf), and the nucleotidic diversity (Pi) were 1.46%, 3.96% and 3.78%. The mean absolute difference in the two patients (5 amplicons each), in the GS-FLX and GS-FLX+, were 1.46%, 3.96% and 3.78% for Sn, Mf and Pi. No false polymorphic site was observed above 0.5%. Our results indicate that UDPS is an optimal alternative to molecular cloning for quantitative study of HCV viral quasispecies populations, both in complexity and composition. We propose an UDPS data treatment workflow for amplicons from the RNA viral quasispecies which, at a sequencing depth of at least 10,000 reads per strand, enables to obtain sequences and frequencies of consensus haplotypes above 0.5% abundance with no erroneous mutations, with high confidence, resistant mutants as minor variants at the level of 1%, with high confidence that variants are not missed, and highly confident measures of quasispecies complexity., This study has been supported by CDTI (Centro para el Desarrollo Tecnológico Industrial), Spanish Ministry of Economics and Competitiveness (MINECO), IDI-20110115. It has also been supported by MINECO projects SAF 2009-10403, and also by the Spanish Ministry of Health Instituto de Salud Carlos III (FIS) projects PI10/01505. CIBERehd is funded by the Instituto de Salud Carlos III, Madrid. Work at CBMSO was supported by grant BFU2011-23604, FIPSE and Fundación Ramon Areces

Background: Selection of amino acid substitutions associated with resistance to nucleos(t)ide-analog (NA) therapy in the hepatitis B virus (HBV) reverse transcriptase (RT) and their combination in a single viral genome complicates treatment of chronic HBV infection and may affect the overlapping surface coding region. In this study, the variability of an overlapping polymerase-surface region, critical for NA resistance, is investigated before treatment and under antiviral therapy, with assessment of NA-resistant amino acid changes simultaneously occurring in the same genome (linkage analysis) and their influence on the surface coding region. Methodology/Principal Findings: Serum samples obtained from chronic HBV-infected patients at pre-treatment and during sequential NA treatment with lamivudine, adefovir, and entecavir were analyzed by ultra-deep pyrosequencing (UDPS) using the GS-FLX platform (454 Life Sciences-Roche). The pre-treatment HBV quasispecies was not enriched with NA-resistant substitutions. The frequencies of this type of substitutions at pre-treatment did not predict the frequencies observed during lamivudine treatment. On linkage analysis of the RT region studied, NA-resistant HBV variants (except for rtA181T) were present in combinations of amino acid substitutions that increased in complexity after viral breakthrough to entecavir, at which time the combined variant rtL180M-S202G-M204V-V207I predominated. In the overlapping surface region, NA-resistant substitutions caused selection of stop codons in a significant percentage of sequences both at pre-treatment and during sequential treatment; the rtA181T substitution, related to sW172stop, predominated during treatment with lamivudine and adefovir. A highly conserved RT residue (rtL155), even more conserved than the essential residues in the RT catalytic motif YMDD, was identified in all samples. Conclusions: UDPS methodology enabled quantification of HBV quasispecies variants, even those harboring complex combinations of amino acid changes. The high percentage of potentially defective genomes, especially in the surface region, suggests effective trans-complementation of these variants. © 2012 Rodriguez-Frías et al., Centro para el Desarrollo Tecnológico Industrial; Ministry of Economy and Competitiveness

8 páginas, 3 figuras, We show the distribution of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three genomic nomenclature systems to all sequence data from the World Health Organization European Region available until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation, compare the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2., We gratefully acknowledge the authors, originating and submitting laboratories of the sequences from GISAID’s EpiCoV Database used in the phylogenetic analysis. We gratefully acknowledge all the staff working with sample collection, sample preparation, sequencing, data analysis and data sharing in all laboratories in the WHO European Region for making this work possible.