Genetic recombination of the hepatitis C virus: clinical implications

Mixed Infections Unravel Novel HCV Inter-Genotypic Recombinant Forms within the Conserved IRES Region

Hepatitis C virus (HCV) remains a significant global health challenge, affecting millions of people worldwide, with chronic infection a persistent threat. Despite the advent of direct-acting antivirals (DAAs), challenges in diagnosis and treatment remain, compounded by the lack of an effective vaccine. The HCV genome, characterized by high genetic variability, consists of eight distinct genotypes and over ninety subtypes, underscoring the complex dynamics of the virus within infected individuals. This study delves into the intriguing realm of HCV genetic diversity, specifically exploring the phenomenon of mixed infections and the subsequent detection of recombinant forms within the conserved internal ribosome entry site (IRES) region. Previous studies have identified recombination as a rare event in HCV. However, our findings challenge this notion by providing the first evidence of 1a/3a (and vice versa) inter-genotypic recombination within the conserved IRES region. Utilizing advanced sequencing methods, such as deep sequencing and molecular cloning, our study reveals mixed infections involving genotypes 1a and 3a. This comprehensive approach not only confirmed the presence of mixed infections, but also identified the existence of recombinant forms not previously seen in the IRES region. The recombinant sequences, although present as low-frequency variants, open new avenues for understanding HCV evolution and adaptation.

Molecular characterization and genotyping of hepatitis C virus from Sudanese end-stage renal disease patients on haemodialysis

Background

Hepatitis C virus (HCV) is a global public health problem, with ~ 11 million people in Africa infected. There is incomplete information on HCV in Sudan, particularly in haemodialysis patients, who have a higher prevalence compared to the general population. Thus, our objectives were to genotype and molecularly characterize HCV isolated from end-stage renal disease haemodialysis patients.

Methods

A total of 541 patients were recruited from eight haemodialysis centres in Khartoum and screened for anti-HCV. Viral loads were determined using in-house real-time PCR in seropositive patients. HCV was genotyped and subtyped using sequencing of amplicons of 5′ untranslated (UTR) and non-structural protein 5B (NS5B) regions, followed by phylogenetic analysis of corresponding sequences.

Results

The HCV seroprevalence in the study was 17% (93/541), with HCV RNA-positive viremic rate of 7% (40/541). A low HCV load, with a mean of 2.85 × 104 IU/ml and a range of 2.95 × 103 to 4.78 × 106 IU/ml, was detected. Phylogenetic analyses showed the presence of genotypes 1, 3, 4, and 5 with subtypes 1a, 1b, 1 g, 3a, 4a, 4 l, 4 m, 4 s, and 4t. Sequences of HCV from the same haemodialysis units, clustered in similar genotypes and subtypes intimating nosocomial infection.

Conclusion

HCV infection is highly prevalent in haemodialysis patients from Sudan, with phylogenetic analysis intimating nosocomial infection. HCV genotyping is useful to locate potential transmission chains and to enable individualized treatment using highly effective direct-acting antivirals (DAAs).

The genotype analysis of the hepatitis C virus in Heilongjiang Province, China

Introduction: Hepatitis C virus (HCV) infection is a major public health issue. HCV genotype identification is clinically important to tailor the dosage and duration of treatment, and recombination in intra-patient populations of HCV may lead to the generation of escape mutants, as previously observed for other RNA viruses. Up to now, there is no study assessing HCV genotypes and subtypes in Heilongjiang Province, China.Methods: To determine genotype and phylogenetic analysis of HCV in Heilongjiang Province is crucial. In this study, we amplified 3 genome regions (5'UTR, E1, and NS5B) of 30 HCV patients in Heilongjiang Province, amplified products were analyzed by bioinformatics.Results: We found that 23 specimens had concordant subtypes in the 3 gene regions (2a and 1b), 7 HCV patients were considered the recombinants, the recombination pattern of the 7 HCV patients in the 5'UTR, E1, and NS5B region as followed: 1b/2a/1b, 2a/2a/1b, 1b/2a/2a, 1b/2a/1b, 1b/2a/1b, 1b/2a/1b, 2a/2a/1b.Conclusions: The findings in the present study showed that a higher recombination rate (23%) than other researches, and the recombination of 2a/1b in the 5'UTR, E1, and NS5B region was only found in the present study up to now.

Detection of circulating HCV recombinant form RF1_2k/1b in blood serum of patients by real-time RT-PCR

Globally, about 70 million people are infected with the hepatitis C virus (HCV), and about 400 thousand people die annually from chronic hepatitis C complications. The management of patients with chronic hepatitis C may require HCV genotyping, since the efficiency of some widely used antiviral drugs strongly depend on the viral genotype and/or subtype. The most prevalent HCV circulating recombinant form, RF1_2k/1b, is misclassified as genotype 2 by many commercial HCV genotyping kits, based on the RT-PCR analysis of the 5' untranslated region of the HCV genome. This leads to inappropriate patient treatment, since the accepted treatment schemes for HCV genotype 2 are ineffective for the RF1_2k/1b. Here we describe a method for detecting the RNA HCV RF1_2k/1b in blood samples by RT-PCR analysis of two regions in HCV genome (5'UTR and NS5b). The method was tested on 240 blood serum samples from HCV infected patients, in which HCV genotype was defined as 2 or mixed (2+1 or 2+3) by the two commercial genotyping kits "OT-Hepatogen-C genotype" ("DNA-Technology", Moscow) and "RealBest RNA HCV-1/2/3" ("Vector- Best ", Novosibirsk). 50 (20.8%) RF1_2k/1b cases were revealed, including three mixed infections: RF1_2k/1b + 1a, RF1_2k/1b + 3a, RF1_2k/1b + 1b. In all cases, the accuracy of HCV typing by the proposed method was confirmed by Sanger sequencing and phylogenetic analysis. The method is easy to implement into clinical practice and may be used in clinical settings equipped for RT-PCR analysis to correctly identify the recombinant variant RF1_2k/1b.

Hospitalization and mortality associated with SARS-CoV-2 viral clades in COVID-19

The COVID-19 epidemic of 2019-20 is due to the novel coronavirus SARS-CoV-2. Following first case description in December, 2019 this virus has infected over 10 million individuals and resulted in at least 500,000 deaths world-wide. The virus is undergoing rapid mutation, with two major clades of sequence variants emerging. This study sought to determine whether SARS-CoV-2 sequence variants are associated with differing outcomes among COVID-19 patients in a single medical system. Whole genome SARS-CoV-2 RNA sequence was obtained from isolates collected from patients registered in the University of Washington Medicine health system between March 1 and April 15, 2020. Demographic and baseline clinical characteristics of patients and their outcome data including their hospitalization and death were collected. Statistical and machine learning models were applied to determine if viral genetic variants were associated with specific outcomes of hospitalization or death. Full length SARS-CoV-2 sequence was obtained 190 subjects with clinical outcome data. 35 (18.4%) were hospitalized and 14 (7.4%) died from complications of infection. A total of 289 single nucleotide variants were identified. Clustering methods demonstrated two major viral clades, which could be readily distinguished by 12 polymorphisms in 5 genes. A trend toward higher rates of hospitalization of patients with Clade 2 infections was observed (p = 0.06, Fisher's exact). Machine learning models utilizing patient demographics and co-morbidities achieved area-under-the-curve (AUC) values of 0.93 for predicting hospitalization. Addition of viral clade or sequence information did not significantly improve models for outcome prediction. In summary, SARS-CoV-2 shows substantial sequence diversity in a community-based sample. Two dominant clades of virus are in circulation. Among patients sufficiently ill to warrant testing for virus, no significant difference in outcomes of hospitalization or death could be discerned between clades in this sample. Major risk factors for hospitalization and death for either major clade of virus include patient age and comorbid conditions.

Assessment of treatment options for patients with hepatitis C virus recombinant form 2k/1b

AIM

Hepatitis C virus (HCV) intergenotype recombinant form (RF) 2k/1b has been actively circulating in HCV-infected patients, and the prevalence of this RF virus in the Republic of Georgia is one of the highest reported worldwide. The aim of this study was to define the optimal treatment regimen for patients with RF_2k/1b.

METHODS

We analyzed the data of 2735 patients who started treatment at the Medical Center Mrcheveli within Georgia's hepatitis C elimination program from May 2015 through December 2019. The patients were treated with sofosbuvir (SOF)-based regimens. For identification of RF_2k/1b variants, refinement of standard (INNO-LiPA) genotyping results for all patient samples assigned the unspecific HCV genotypes (GT) 2a/2c was carried out by sequencing of core and non-structural protein 5B genes.

RESULTS

Overall, 444 patients, representing 66% of GT2 and 16% of the total samples, were RF_2k/1b. Treatment of patients with RF_2k/1b with SOF/ledipasvir and SOF/velpatasvir was highly effective and viral cure rates did not differ among genotypes treated with the same regimen: RF_2k/1b, 99% (343/346); GT1, 99% (876/885); GT2, 96% (156/162); and GT3, 99% (545/552). A separate comparison analysis of sustained virologic response rate, treated with SOF plus ribavirin, showed significantly higher sustained virologic response (96%) in patients with confirmed GT2 (by sequencing) compared to unspecified GT2 (by INNO-LiPA) (79%) (P < 0.05).

CONCLUSION

Sofosbuvir-based regimens are highly effective for treatment of RF 2k/1b patients, and with availability of new pan-genotypic direct-acting antivirals, genotyping to identify RF 2k/1b patients might not be necessary.

Outcomes associated with SARS-CoV-2 viral clades in COVID-19

Background The COVID-19 epidemic of 2019-20 is due to the novel coronavirus SARS-CoV-2. Following first case description in December, 2019 this virus has infected over 10 million individuals and resulted in at least 500,000 deaths world-wide. The virus is undergoing rapid mutation, with two major clades of sequence variants emerging. This study sought to determine whether SARS-CoV-2 sequence variants are associated with differing outcomes among COVID-19 patients in a single medical system. Methods Whole genome SARS-CoV-2 RNA sequence was obtained from isolates collected from patients registered in the University of Washington Medicine health system between March 1 and April 15, 2020. Demographic and baseline medical data along with outcomes of hospitalization and death were collected. Statistical and machine learning models were applied to determine if viral genetic variants were associated with specific outcomes of hospitalization or death. Findings Full length SARS-CoV-2 sequence was obtained 190 subjects with clinical outcome data. 35 (18.4%) were hospitalized and 14 (7.4%) died from complications of infection. A total of 289 single nucleotide variants were identified. Clustering methods demonstrated two major viral clades, which could be readily distinguished by 12 polymorphisms in 5 genes. A trend toward higher rates of hospitalization of patients with Clade 2 was observed (p=0.06). Machine learning models utilizing patient demographics and co-morbidities achieved area-under-the-curve (AUC) values of 0.93 for predicting hospitalization. Addition of viral clade or sequence information did not significantly improve models for outcome prediction. Conclusion SARS-CoV-2 shows substantial sequence diversity in a community-based sample. Two dominant clades of virus are in circulation. Among patients sufficiently ill to warrant testing for virus, no significant difference in outcomes of hospitalization or death could be discerned between clades in this sample. Major risk factors for hospitalization and death for either major clade of virus include patient age and comorbid conditions.

Hepatitis C virus genotyping based on Core and NS5B regions in Cameroonian patients

Background

Current HCV treatments are genotype specific although potential pan-genotype treatments have recently been described. Therefore, genotyping is an essential tool for the therapeutic management of HCV infection and a variety of technologies have been developed for HCV genotypes determination. Sequences analysis of HCV sub-genomic regions is considered as gold standard and is widely used for HCV genotyping. Here, we compared HCV genotyping using core and NS5B regions in routine practice in HCV-positive Cameroonian patients.

Methods

All plasma samples received at Centre Pasteur of Cameroon (CPC) in 2016 for HCV genotyping were included. Viral loads were determined using the Abbott Real Time assay. Further, genotyping was based on the amplification and sequencing of core and NS5B regions following by phylogenetic analysis of corresponding sequences.

Results

A total of 369 samples were received during the study period with high viral load values (median: 930,952 IU/ml; IQR: 281,833-2,861,179). Positive amplification was obtained in at least one genomic region (core or NS5B) for all the samples with similar amplification rate in the two genomic regions (p = 0.34). Phylogenetic analysis showed that among the 369 samples, 146 (39.6%) were classified as genotype 4, 132 (35.8%) as genotype 1, 89 (24.1%) as genotype 2, in both core and NS5B regions. Interestingly, for two samples (0.54%) discordant genotypes were obtained in both regions with the core region classified as genotype 4 while the NS5B was identified as genotype 1 indicating the presence of putative HCV recombinant virus or multiple infections in these samples. Discrimination of HCV subtypes was most likely possible with NS5B compared to core region.

Conclusions

We found high amplification rates of HCV in both core and NS5B regions, and a good concordance was obtained at genotype level using both regions except for two samples where putative 1–4 recombinants/multiple infections were detected. Therefore, HCV genotyping based on at least two genomic regions could help to identify putative recombinants and improve therapeutic management of HCV infection.

Heterogeneity and coexistence of oncogenic mechanisms involved in HCV-associated B-cell lymphomas

The association of HCV-infection with B-lymphomas is supported by the regression of most indolent/low-grade lymphomas following anti-viral therapy. Studies on direct and indirect oncogenic mechanisms have elucidated the pathogenesis of HCV-associated B-lymphoma subtypes. These include B-lymphocyte proliferation and sustained clonal expansion by HCV-envelope protein stimulation of B-cell receptors, and prolonged HCV-infected B-cell growth by overexpression of an anti-apoptotic BCL-2 oncogene caused by the increased frequency of t(14;18) chromosomal translocations in follicular lymphomas. HCV has been implicated in lymphomagenesis by a "hit-and-run" mechanism, inducing enhanced mutation rate in immunoglobulins and anti-oncogenes favoring immune escape, due to permanent genetic damage by double-strand DNA-breaks. More direct oncogenic mechanisms have been identified in cytokines and chemokines in relation to NS3 and Core expression, particularly in diffuse large B-cell lymphoma. By reviewing genetic alterations and disrupted signaling pathways, we intend to highlight how mutually non-contrasting mechanisms cooperate with environmental factors toward progression of HCV-lymphoma.

Superinfection and cure of infected cells as mechanisms for hepatitis C virus adaptation and persistence

RNA viruses exist as a genetically diverse quasispecies with extraordinary ability to adapt to abrupt changes in the host environment. However, the molecular mechanisms that contribute to their rapid adaptation and persistence in vivo are not well studied. Here, we probe hepatitis C virus (HCV) persistence by analyzing clinical samples taken from subjects who were treated with a second-generation HCV protease inhibitor. Frequent longitudinal viral load determinations and large-scale single-genome sequence analyses revealed rapid antiviral resistance development, and surprisingly, dynamic turnover of dominant drug-resistant mutant populations long after treatment cessation. We fitted mathematical models to both the viral load and the viral sequencing data, and the results provided strong support for the critical roles that superinfection and cure of infected cells play in facilitating the rapid turnover and persistence of viral populations. More broadly, our results highlight the importance of considering viral dynamics and competition at the intracellular level in understanding rapid viral adaptation. Thus, we propose a theoretical framework integrating viral and molecular mechanisms to explain rapid viral evolution, resistance, and persistence despite antiviral treatment and host immune responses.

5' UTR and NS5B-based genotyping of hepatitis C virus in patients from Damietta governorate, Egypt

Chronic hepatitis C virus (HCV) infection is a main health problem in Egypt causing high rates of mortalities. Egypt has the highest HCV prevalence in the world, with specific HCV subtypes epidemic and circulating extensively in the country. Different antiviral therapy protocols have been implemented for treating Egyptian HCV patients. Due to the limited data about HCV in Egypt, this study aimed to genotype HCV strains circulating in the Nile Delta Damietta governorate and to investigate the variation in the nonstructural 5B (NS5B) region targeted by the newly approved antiviral drugs. Thirty HCV samples from treatment-naïve patients were genotyped by restriction fragment length polymorphism. Some samples were genotyped by direct sequencing of their 5' untranslated region (UTR) and NS5B regions. Phylogenetic analysis was also performed on the sequences of their NS5B regions. Fourteen new sequences have been deposited in the GenBank database. Results showed that subtype 4a was prevalent in addition to subtype 1g. None of the previously reported NS5B substitutions were detected in the sequenced isolates from treatment-naïve patients, which may be a good predictor for efficient treatment of HCV Egyptian patients with Sofosbuvir. Further studies on Sofosbuvir treated-HCV Egyptian patients are required to investigate whether any NS5B substitutions can confer resistance to treatment.

Identification of hepatitis C virus 2k/1b intergenotypic recombinants in Georgia

BACKGROUND AND AIMS

This study aimed to evaluate the prevalence of the hepatitis C virus intergenotype recombinant strain RF1_2k/1b in Georgia, confirm viral recombination by full genome sequencing, and determine a genetic relationship with previously described recombinant hepatitis C viruses.

METHODS

We retrospectively analysed data from 1421 Georgian patients with chronic hepatitis C. Genotyping was performed with the INNO-LiPA VERSANT HCV Genotype 2.0 Assay.

RESULTS

Virus isolates were assigned to nonspecific hepatitis C genotypes 2a/2c (n = 387) as performed by sequencing of core and NS5B genes. Subsequently, sequencing results classified the core region as genotype 2k and the NS5B region as genotype 1b for 72% (n = 280) of genotype 2 patients, corresponding to 19.7% of hepatitis C patients in Georgia. Eight samples were randomly selected for full genome sequencing which was successful in 7 of 8 samples. Analysis of the generated consensus sequences confirmed that all 7 viruses were 2k/1b recombinants, with the recombination breakpoint located within 73-77 amino acids before the NS2-NS3 junction, similar to the previously described RF1_2k/1b virus. Phylogenetic analysis revealed clustering of the Georgian 2k/1b viruses and RF1_2k/1b, suggesting that they are genetically related.

CONCLUSIONS

The 19.7% prevalence of RF1_2k/1b in Georgia patients is far higher than has generally been reported to date worldwide. Identification of recombinants in low income countries with a high prevalence of HCV infection might be reasonable for choosing the most cost-effective treatment regimens.

Misidentification of recombinant hepatitis C virus leading to treatment failure with direct acting antivirals

The use of new Direct Acting Antivirals, specific of HCV, has greatly improved the HCV treatment. Most of the DAA are specific of HCV genotypes. Genotyping methods may target different regions of the HCV genome, though only the whole genome sequencing could confirm the correct genotype. The present study describes the virological investigation of a treatment failure due to the false identification of an unusual 2k/1b recombinant HCV form. It describes the sequencing methods, and the similarity analysis of the sequences to different genotype query sequences, to identify the recombination breakpoint.

Impact of inter-genotypic recombination and probe cross-reactivity on the performance of the Abbott RealTime HCV Genotype II assay for hepatitis C genotyping

The Abbott RealTime HCV Genotype II assay (Abbott-RT-HCV assay) is a real-time PCR based genotyping method for hepatitis C virus (HCV). This study measured the impact of inter-genotypic recombination and probe cross-reactivity on the performance of the Abbott-RT-HCV assay. 517 samples were genotyped using the Abbott-RT-HCV assay over a one-year period, 34 (6.6%) were identified as HCV genotype 1 without further subtype designation raising the possibility of inaccurate genotyping. These samples were subjected to confirmatory sequencing. 27 of these 34 (79%) samples were genotype 1b while five (15%) were genotype 6. One HCV isolate was an inter-genotypic 1a/4o recombinant. This is a novel natural HCV recombinant that has never been reported. Inter-genotypic recombination and probe cross-reactivity can affect the accuracy of the Abbott-RT-HCV assay, both of which have significant implications on antiviral regimen choice. Confirmatory sequencing of ambiguous results is crucial for accurate genotyping.

Baseline and Breakthrough Resistance Mutations in HCV Patients Failing DAAs

Sustained virologic response rates have increased dramatically following direct acting antiviral (DAA) therapy in chronic HCV infection. However, resistance-associated substitutions (RASs) may occur either prior to DAA or following drug exposure. The aim of this study was to determine RASs in DAA treatment-failing patients and the role of RASs in failure treatment. Six hundred and twenty HCV patients were evaluated. Direct sequencing of HCV genes was performed at breakthrough in all 31 patients failing DAAs, and in 19 baseline patients. Deep sequencing analysis was performed in 15/19 baseline patients. RASs were detected at breakthrough in 17/31 patients and at baseline in 11/19 patients, although, only 8/19 patients carried RASs associated with the prescribed regimen. Deep sequencing analysis showed RASs at baseline in 10/15 treatment-failing patients. No significant difference was observed with the Sanger sequencing. Treatment failure in the 14/31 patients without RASs was associated with suboptimal treatment. In 54.8% of treatment-failing patients one of the causes of failure might be the presence of RASs. In the majority of patients with RASs, mutations were present at baseline. Direct resistance test is advocated before treatment and at breakthrough in order to optimize retreatment regimens.

Causes of treatment failure for hepatitis C in the era of direct-acting antiviral therapy

Hepatitis C therapy in the era of the newer direct-acting antiviral agents has radically changed our treatment schemes by achieving very high rates of sustained virological response. However, treatment with direct antiviral agents fails in a subgroup of patients. This group of so-called difficult-to-treat individuals is the subject of this paper, which reviews the causes of virological failure, their clinical implications, and some final recommendations.

The 5BSL3.2 Functional RNA Domain Connects Distant Regions in the Hepatitis C Virus Genome

Viral genomes are complexly folded entities that carry all the information required for the infective cycle. The nucleotide sequence of the RNA virus genome encodes proteins and functional information contained in discrete, highly conserved structural units. These so-called functional RNA domains play essential roles in the progression of infection, which requires their preservation from one generation to the next. Numerous functional RNA domains exist in the genome of the hepatitis C virus (HCV). Among them, the 5BSL3.2 domain in the cis-acting replication element (CRE) at the 3' end of the viral open reading frame has become of particular interest given its role in HCV RNA replication and as a regulator of viral protein synthesis. These functionalities are achieved via the establishment of a complex network of long-distance RNA-RNA contacts involving (at least as known to date) the highly conserved 3'X tail, the apical loop of domain IIId in the internal ribosome entry site, and/or the so-called Alt region upstream of the CRE. Changing contacts promotes the execution of different stages of the viral cycle. The 5BSL3.2 domain thus operates at the core of a system that governs the progression of HCV infection. This review summarizes our knowledge of the long-range RNA-RNA interaction network in the HCV genome, with special attention paid to the structural and functional consequences derived from the establishment of different contacts. The potential implications of such interactions in switching between the different stages of the viral cycle are discussed.

Natural non-homologous recombination led to the emergence of a duplicated V3-NS5A region in HCV-1b strains associated with hepatocellular carcinoma

BACKGROUND

The emergence of new strains in RNA viruses is mainly due to mutations or intra and inter-genotype homologous recombination. Non-homologous recombinations may be deleterious and are rarely detected. In previous studies, we identified HCV-1b strains bearing two tandemly repeated V3 regions in the NS5A gene without ORF disruption. This polymorphism may be associated with an unfavorable course of liver disease and possibly involved in liver carcinogenesis. Here we aimed at characterizing the origin of these mutant strains and identifying the evolutionary mechanism on which the V3 duplication relies.

METHODS

Direct sequencing of the entire NS5A and E1 genes was performed on 27 mutant strains. Quasispecies analyses in consecutive samples were also performed by cloning and sequencing the NS5A gene for all mutant and wild strains. We analyzed the mutant and wild-type sequence polymorphisms using Bayesian methods to infer the evolutionary history of and the molecular mechanism leading to the duplication-like event.

RESULTS

Quasispecies were entirely composed of exclusively mutant or wild-type strains respectively. Mutant quasispecies were found to have been present since contamination and had persisted for at least 10 years. This V3 duplication-like event appears to have resulted from non-homologous recombination between HCV-1b wild-type strains around 100 years ago. The association between increased liver disease severity and these HCV-1b mutants may explain their persistence in chronically infected patients.

CONCLUSIONS

These results emphasize the possible consequences of non-homologous recombination in the emergence and severity of new viral diseases.

A Simple and Reliable Strategy for BK Virus Subtyping and Subgrouping

BK virus (BKV)-associated diseases in transplant recipients are an emerging issue. However, identification of the various BK virus subtypes/subgroups is a long and delicate process on the basis of currently available data. Therefore, we wanted to define a simple and effective one-step strategy for characterizing all BK virus strains from the VP1 gene sequence. Based on the analysis of 199 available complete DNA VP1 sequences, phylogenetic trees, alignments, and isolated polymorphisms were used to define an effective strategy for distinguishing the 12 different BK virus subtypes/subgroups. Based on the 12 subtypes identified from the 199 complete BKV VP1 sequences (1,089 bp), 60 mutations that can be used to differentiate these various subtypes/subgroups were identified. Some genomic areas were more variable and comprised mutational hot spots. From a subregion of only 100 bp in the VP1 region (1977 through 2076), we therefore constructed an algorithm that enabled rapid determination of all BKV subtypes/subgroups with 99% agreement (197/199) relative to the complete VP1 sequence. We called this domain of the BK viral genome the BK typing and grouping region (BKTGR). Finally, we validated our viral subtype identification process in a population of 100 transplant recipients with 100% efficiency. The new simpler method of BKV subtyping/subgrouping reported here constitutes a useful tool for future studies that will help us to more clearly understand the impact of BKV subtypes/subgroups on diagnosis, infection, and BK virus-associated diseases.

HCV intergenotype 2k/1b recombinant detected in a DAA-treated patient in Italy

Direct-acting antiviral (DAA) combinations are potent and effective drugs currently recommended for treatment of chronic HCV infection. Difficult to treat genotypes are the most important predictors of treatment failure. We report a case of DAA treatment failure in an HCV-infected patient carrying a recombinant genotype 2k/1b. This strain, first isolated from a Russian patient in 2002, has now been observed for the first time in Italy.

Recombination in hepatitis C virus is not uncommon among people who inject drugs in Kolkata, India

Recombination in RNA virus is a rare event in the survival and evolution to evade host immune system. This is increasing within high risk group population (HRG) due to super infection that occurs by continuous sharing of common drug equipment by HCV infected or HIV-HCV co-infected recurrent drug users. Recombination causes impediment to vaccine development and therapeutic intervention as standard HCV treatment is still genotype specific. Blood samples of 194 people who inject drugs (PWID) were collected from an Opioid Substitution Therapy Centre in Kolkata, India. HCV sero-reactivity was checked by ELISA. Detection of HCV RNA by nested RT-PCR and genotyping by DNA sequencing were done. Phylogenetic analysis, Simplot, Bootscan plot, Recombination Detection Program were used for recombinant strain identification. Out of 80 HCV sero-reactive samples, 77 were RNA positive (96.25%). Out of 74 HIV mono-infected individuals, 12 HCV sero-nonreactive samples were HCV RNA positive. Out of total 89 RNA positive samples, 64 paired partial core and NS5B region (71.9%) were sequenced by Sanger's method. Two major genotypes (1 and 3), four subtypes and an inter-genotype recombinant strain (3a/1a) with a novel breakpoint in the NS4B coding region were found.

Is Predominant Clonal Evolution a Common Evolutionary Adaptation to Parasitism in Pathogenic Parasitic Protozoa, Fungi, Bacteria, and Viruses?

We propose that predominant clonal evolution (PCE) in microbial pathogens be defined as restrained recombination on an evolutionary scale, with genetic exchange scarce enough to not break the prevalent pattern of clonal population structure. The main features of PCE are (1) strong linkage disequilibrium, (2) the widespread occurrence of stable genetic clusters blurred by occasional bouts of genetic exchange ('near-clades'), (3) the existence of a "clonality threshold", beyond which recombination is efficiently countered by PCE, and near-clades irreversibly diverge. We hypothesize that the PCE features are not mainly due to natural selection but also chiefly originate from in-built genetic properties of pathogens. We show that the PCE model obtains even in microbes that have been considered as 'highly recombining', such as Neisseria meningitidis, and that some clonality features are observed even in Plasmodium, which has been long described as panmictic. Lastly, we provide evidence that PCE features are also observed in viruses, taking into account their extremely fast genetic turnover. The PCE model provides a convenient population genetic framework for any kind of micropathogen. It makes it possible to describe convenient units of analysis (clones and near-clades) for all applied studies. Due to PCE features, these units of analysis are stable in space and time, and clearly delimited. The PCE model opens up the possibility of revisiting the problem of species definition in these organisms. We hypothesize that PCE constitutes a major evolutionary strategy for protozoa, fungi, bacteria, and viruses to adapt to parasitism.

Characterization of NS5A polymorphisms and their impact on response rates in patients with HCV genotype 2 treated with daclatasvir-based regimens

OBJECTIVE

Daclatasvir (DCV) is a pan-genotypic non-structural protein 5A (NS5A) inhibitor that is approved for treatment of hepatitis C virus (HCV) genotype (GT)1 and GT3 in the USA and GT1, GT3 and GT4 in Europe. We set out to examine the impact of daclatasvir-based regimens on the sustained virologic response (SVR) in patients with GT2 infection with respect to GT2 subtype and NS5A polymorphisms at amino acid positions associated with daclatasvir resistance.

METHODS

Analyses were performed on 283 GT2 NS5A sequences from five daclatasvir regimen-based clinical trials (ClinicalTrials.gov: NCT-01257204, NCT-01359644, NCT-02032875, NCT-02032888 and NCT-01616524) and 143 NS5A sequences from the Los Alamos HCV database. Susceptibility analyses of substitutions at amino acid positions associated with daclatasvir resistance and patient-derived NS5A sequences were performed using an in vitro HCV replication assay.

RESULTS

Of 13 GT2 subtypes identified from 426 NS5A sequences, the most prevalent were GT2a (32%), GT2b (48%) and GT2c (10%). The most prevalent NS5A polymorphism was L31M (GT2a = 88%; GT2b = 59%; GT2c = 10%). Substitutions identified in 96% of GT2 NS5A sequences exhibited daclatasvir EC₅₀ values ranging from 0.005 to 20 nM when tested in vitro. A similar range in daclatasvir EC₅₀ values was observed for 16 diverse GT2 patient-derived NS5A sequences (EC₅₀ = 0.005-60 nM). Depending on the daclatasvir-based regimen studied (daclatasvir/interferon-based or daclatasvir/sofosbuvir-based), SVR rates ranged from 90% to 100% in GT2 patients with the most prevalent baseline NS5A-L31M polymorphism, compared with from 96% to 100% without this polymorphism.

CONCLUSIONS

High SVR rates were achieved in patients infected with GT2 treated with daclatasvir-based regimens irrespective of GT2 subtype or baseline NS5A polymorphisms.

Heads or Tails: Genotyping of Hepatitis C Virus Concerning the 2k/1b Circulating Recombinant Form

As different hepatitis C virus (HCV) genotypes respond differently to initiated therapy, correct HCV genotyping is essential. A potential risk for misclassification of the intergenotypic HCV circulating recombinant form (CRF) 2k/1b strains exists, depending on the genotyping method used. The aim was to investigate the differences in HCV genotyping methods with regard to CRF 2k/1b and to gain insight in the prevalence of the CRF 2k/1b. Genotyping results by Versant HCV Genotype Assay were compared with nonstructural protein 5B (NS5B) sequencing. In total, from November 2001 until March 2015, 3296 serum samples were analyzed by Versant HCV Genotype Assay. As misclassified CRF is harbored among HCV genotype 2, we further focused our search on 142 (4.3%) samples positive for HCV genotype 2. On 116 (81.7%) retrieved samples, the NS5B sequencing was performed. Twelve out of the 116 retrieved samples (10.3%) were classified as CRF 2k/1b by sequencing of the NS5B region. Ten of these 12 samples were originally misclassified as genotype 2a or 2c, while 2 of them were misclassified as genotype 2. Our results show that the current prevalence of CRF 2k/1b is underestimated. The importance of correct HCV genotyping is emphasized, considering the tailored choice of treatment regimen and overall prognosis.

Hepatitis C virus: Promising discoveries and new treatments

Despite advances in therapy, hepatitis C virus (HCV) infection remains an important global health issue. It is estimated that a significant part of the world population is chronically infected with the virus, and many of those affected may develop cirrhosis or liver cancer. The virus shows considerable variability, a characteristic that directly interferes with disease treatment. The response to treatment varies according to HCV genotype and subtype. The continuous generation of variants (quasispecies) allows the virus to escape control by antivirals. Historically, the combination of ribavirin and interferon therapy has represented the only treatment option for the disease. Currently, several new treatment options are emerging and are available to a large part of the affected population. In addition, the search for new substances with antiviral activity against HCV continues, promising future improvements in treatment. Researchers should consider the mutation capacity of the virus and the other variables that affect treatment success.

Antiviral drug resistance as an adaptive process

Antiviral drug resistance is a matter of great clinical importance that, historically, has been investigated mostly from a virological perspective. Although the proximate mechanisms of resistance can be readily uncovered using these methods, larger evolutionary trends often remain elusive. Recent interest by population geneticists in studies of antiviral resistance has spurred new metrics for evaluating mutation and recombination rates, demographic histories of transmission and compartmentalization, and selective forces incurred during viral adaptation to antiviral drug treatment. We present up-to-date summaries on antiviral resistance for a range of drugs and viral types, and review recent advances for studying their evolutionary histories. We conclude that information imparted by demographic and selective histories, as revealed through population genomic inference, is integral to assessing the evolution of antiviral resistance as it pertains to human health.

Synonymous and nonsynonymous distances help untangle convergent evolution and recombination

When estimating a phylogeny from a multiple sequence alignment, researchers often assume the absence of recombination. However, if recombination is present, then tree estimation and all downstream analyses will be impacted, because different segments of the sequence alignment support different phylogenies. Similarly, convergent selective pressures at the molecular level can also lead to phylogenetic tree incongruence across the sequence alignment. Current methods for detection of phylogenetic incongruence are not equipped to distinguish between these two different mechanisms and assume that the incongruence is a result of recombination or other horizontal transfer of genetic information. We propose a new recombination detection method that can make this distinction, based on synonymous codon substitution distances. Although some power is lost by discarding the information contained in the nonsynonymous substitutions, our new method has lower false positive probabilities than the comparable recombination detection method when the phylogenetic incongruence signal is due to convergent evolution. We apply our method to three empirical examples, where we analyze: (1) sequences from a transmission network of the human immunodeficiency virus, (2) tlpB gene sequences from a geographically diverse set of 38 Helicobacter pylori strains, and (3) hepatitis C virus sequences sampled longitudinally from one patient.

Genome Sequence Analysis of New Isolates of the Winona Strain of Plum pox virus and the First Definitive Evidence of Intrastrain Recombination Events

Plum pox virus (PPV) is genetically diverse with nine different strains identified. Mutations, indel events, and interstrain recombination events are known to contribute to the genetic diversity of PPV. This is the first report of intrastrain recombination events that contribute to PPV's genetic diversity. Fourteen isolates of the PPV strain Winona (W) were analyzed including nine new strain W isolates sequenced completely in this study. Isolates of other strains of PPV with more than one isolate with the complete genome sequence available in GenBank were included also in this study for comparison and analysis. Five intrastrain recombination events were detected among the PPV W isolates, one among PPV C strain isolates, and one among PPV M strain isolates. Four (29%) of the PPV W isolates analyzed are recombinants; one of which (P2-1) is a mosaic, with three recombination events identified. A new interstrain recombinant event was identified between a strain M isolate and a strain Rec isolate, a known recombinant. In silico recombination studies and pairwise distance analyses of PPV strain D isolates indicate that a threshold of genetic diversity exists for the detectability of recombination events, in the range of approximately 0.78×10(-2) to 1.33×10(-2) mean pairwise distance. RDP4 analyses indicate that in the case of PPV Rec isolates there may be a recombinant breakpoint distinct from the obvious transition point of strain sequences. Evidence was obtained that indicates that the frequency of PPV recombination is underestimated, which may be true for other RNA viruses where low genetic diversity exists.

Amplification and pyrosequencing of near-full-length hepatitis C virus for typing and monitoring antiviral resistant strains

Directly acting antiviral drugs have contributed considerable progress to hepatitis C virus (HCV) treatment, but they show variable activity depending on virus genotypes and subtypes. Therefore, accurate genotyping including recombinant form detection is still of major importance, as is the detection of resistance-associated mutations in case of therapeutic failure. To meet these goals, an approach to amplify the HCV near-complete genome with a single long-range PCR and sequence it with Roche GS Junior was developed. After optimization, the overall amplification success rate was 73% for usual genotypes (i.e. HCV 1a, 1b, 3a and 4a, 16/22) and 45% for recombinant forms RF_2k/1b (5/11). After pyrosequencing and subsequent de novo assembly, a near-full-length genomic consensus sequence was obtained for 19 of 21 samples. The genotype and subtype were confirmed by phylogenetic analysis for every sample, including the suspected recombinant forms. Resistance-associated mutations were detected in seven of 13 samples at baseline, in the NS3 (n = 3) or NS5A (n = 4) region. Of these samples, the treatment of one patient included daclatasvir, and that patient experienced a relapse. Virus sequences from pre- and posttreatment samples of four patients who experienced relapse after sofosbuvir-based therapy were compared: the selected variants seem too far from the NS5B catalytic site to be held responsible. Although tested on a limited set of samples and with technical improvements still necessary, this assay has proven to be successful for both genotyping and resistance-associated variant detection on several HCV types.

High incidence of the hepatitis C virus recombinant 2k/1b in Georgia: Recommendations for testing and treatment

AIM

The first hepatitis C virus (HCV) recombinant, RF2k/1b, was initially described from Russia and has since then been identified from patients in Ireland, Estonia, Uzbekistan and Cyprus. Many of these patients originated from Georgia; however, there is no information on its prevalence in Georgia or its susceptibility to antiviral treatment.

METHODS

We retrospectively sequenced the non-structural region 5B (NS5B) of the HCV genome in samples from 72 Georgian patients, 36 of whom had been treated with pegylated interferon and ribavirin.

RESULTS

The HCV genotype was determined using the Versant HCV Genotype v2 kit. Based on this typing, 32 patients (44.4%) were infected with genotype 1, 21 (29.1%) genotype 2 and 19 (26.3%) genotype 3. Partial NS5B of these strains was sequenced and analyzed for type, with concordant genotype results for all type 1 and 3 strains. Discrepant results were observed for genotyped 2 strains, with 16 (76%) having NS5B of subtype 1b. On phylogenetic analysis, 15 NS5B sequences of these strains were found in a clade formed by recombinant RF2k/1b strains. The remaining discordant sequence was found within a clade formed by 1b strains.

CONCLUSION

Our findings show that the RF2k/1b recombinant strain is common among Georgian patients previously assumed to be infected with genotype 2. Because genotyping is mainly performed to decide treatment strategies, there is a need to determine the genotype by analysis of at least two genomic regions in strains from Georgian patients considered infected with genotype 2 based on standard HCV genotyping methods.

Phylogenetic analysis of a circulating hepatitis C virus recombinant strain 1b/1a isolated in a French hospital centre

Genetic recombination is now a well-established feature of the hepatitis C virus (HCV) variability and evolution, with the recent identification of circulating recombinant forms. In Amiens University Hospital Centre (France), a discrepancy of genotyping results was observed for 9 samples, between their 5' untranslated region assigned to genotype 1b and their NS5B region assigned to genotype 1a, suggesting the existence of a recombinant strain. In the present study, clinical and phylogenetic analyses of these isolates were conducted and a putative relationship with previously identified HCV 1b/1a recombinants was investigated. The results revealed that all 9 strains displayed a breakpoint within the beginning of the core protein, were closely related between each other and with the H23 strain identified in Uruguay (Moreno et al., 2009). Then, the clinical characteristics of the 9 unlinked individuals infected with this 1b/1a genotype were analysed. This is the first report on the circulation, in a French population, of a HCV recombinant strain 1b/1a. The identification of this genotype in other patients and in other geographical zones would allow to further investigate its prevalence in the population and to better understand its molecular epidemiology.

Characterization of Hepatitis C Virus Recombination in Cameroon by Use of Nonspecific Next-Generation Sequencing

The importance of recombination in the evolution and genetic diversity of the hepatitis C virus (HCV) is currently uncertain. Only a small number of intergenotypic recombinants have been identified so far, and each has core and envelope genes classified as belonging to genotype 2. Here, we investigated two putative genotype 4/1 recombinants from southern Cameroon using a number of approaches, including standard Sanger sequencing, genotype-specific PCR amplification, and non-HCV-specific Illumina RNA sequencing (RNA-seq). Recombination between genotypes 1 and 4 was confirmed in both samples, and the parental lineages of each recombinant belong to HCV subtypes that are cocirculating at a high prevalence in Cameroon. Using the RNA-seq approach, we obtained a complete genome for one sample, which contained a recombination breakpoint at the E2/P7 gene junction. We developed and applied a new method, called Deep SimPlot, which can be used to visualize and identify viral recombination directly from the short sequence reads created by next-generation sequencing in conjunction with a consensus sequence.

Identification of a duplicated V3 domain in NS5A associated with cirrhosis and hepatocellular carcinoma in HCV-1b patients

BACKGROUND

The NS5A protein of the hepatitis C virus has been shown to be involved in the development of hepatocellular carcinoma.

OBJECTIVES

In a French multicenter study, we investigated the clinical and epidemiological features of a new HCV genotype 1b strain bearing a wide insertion into the V3 domain.

STUDY DESIGN

We studied NS5A gene sequences in 821 French patients infected with genotype 1b HCV.

RESULTS

We identified an uncharacterized V3 insertion without ORF disruption in 3.05% of the HCV sequences. The insertion comprised 31 amino-acids for the majority of patients; 3 patients had 27 amino-acids insertions and 1 had a 12 amino-acids insertion. Sequence identity between the 31 amino-acids insertions and the V3 domain ranged from 48 to 96% with E-values above 4e(-5), thus illustrating sequence homology and a partial gene duplication event that to our knowledge has never been reported in HCV. Moreover we showed the presence of the duplication at the time of infection and its persistence at least during 12 years in the entire quasispecies. No association was found with extrahepatic diseases. Conversely, patients with cirrhosis were two times more likely to have HCV with this genetic characteristic (p=0.04). Moreover, its prevalence increased with liver disease severity (from 3.0% in patients without cirrhosis to 9.4% in patients with both cirrhosis and HCC, p for trend=0.045).

CONCLUSIONS

We identified a duplicated V3 domain in the HCV-1b NS5A protein for the first time. The duplication may be associated with unfavorable evolution of liver disease including a possible involvement in liver carcinogenesis.

Hepatitis C virus genetic variability and evolution

Hepatitis C virus (HCV) has infected over 170 million people worldwide and creates a huge disease burden due to chronic, progressive liver disease. HCV is a single-stranded, positive sense, RNA virus, member of the Flaviviridae family. The high error rate of RNA-dependent RNA polymerase and the pressure exerted by the host immune system, has driven the evolution of HCV into 7 different genotypes and more than 67 subtypes. HCV evolves by means of different mechanisms of genetic variation. On the one hand, its high mutation rates generate the production of a large number of different but closely related viral variants during infection, usually referred to as a quasispecies. The great quasispecies variability of HCV has also therapeutic implications since the continuous generation and selection of resistant or fitter variants within the quasispecies spectrum might allow viruses to escape control by antiviral drugs. On the other hand HCV exploits recombination to ensure its survival. This enormous viral diversity together with some host factors has made it difficult to control viral dispersal. Current treatment options involve pegylated interferon-α and ribavirin as dual therapy or in combination with a direct-acting antiviral drug, depending on the country. Despite all the efforts put into antiviral therapy studies, eradication of the virus or the development of a preventive vaccine has been unsuccessful so far. This review focuses on current available data reported to date on the genetic mechanisms driving the molecular evolution of HCV populations and its relation with the antiviral therapies designed to control HCV infection.

Genotype- and Subtype-Independent Full-Genome Sequencing Assay for Hepatitis C Virus

Hepatitis C virus (HCV) exhibits a high genetic diversity and is classified into 6 genotypes, which are further divided into 66 subtypes. Current sequencing strategies require prior knowledge of the HCV genotype and subtype for efficient amplification, making it difficult to sequence samples with a rare or unknown genotype and/or subtype. Here, we describe a subtype-independent full-genome sequencing assay based on a random amplification strategy coupled with next-generation sequencing. HCV genomes from 17 patient samples with both common subtypes (1a, 1b, 2a, 2b, and 3a) and rare subtypes (2c, 2j, 3i, 4a, 4d, 5a, 6a, 6e, and 6j) were successfully sequenced. On average, 3.7 million reads were generated per sample, with 15% showing HCV specificity. The assembled consensus sequences covered 99.3% to 100% of the HCV coding region, and the average coverage was 6,070 reads/position. The accuracy of the generated consensus sequence was estimated to be >99% based on results from in vitro HCV replicon amplification, with the same extrapolated amount of input RNA molecules as that for the patient samples. Taken together, the HCV genomes from 17 patient samples were successfully sequenced, including samples with subtypes that have limited sequence information. This method has the potential to sequence any HCV patient sample, independent of genotype or subtype. It may be especially useful in confounding cases, like those with rare subtypes, intergenotypic recombination, or multiple genotype infections, and may allow greater insight into HCV evolution, its genetic diversity, and drug resistance development.

Mutations of the SL2 dimerization sequence of the hepatitis C genome abrogate viral replication

Stem-loop SL2 is a self-interacting palindromic sequence that has been identified within the hepatitis C virus genome (HCV). While, RNA dimerization of the HCV genome has been observed in vitro with short RNA sequences, the role of a putative RNA dimerization during viral replication has not been elucidated. To determine the effect of genomic dimerization on viral replication, we introduced mutations into SL2 predicted to disrupt genomic dimerization. Using surface plasmon resonance, we show that mutations within the SL2 bulge impact dimerization in vitro. Transfection of Huh7 cells with luciferase-encoding full-length genomes containing SL2 mutations abolishes viral replication. Luciferase expression indicates that viral translation is not or slightly affected and that the viral RNA is properly encapsidated. However, RT-qPCR analysis demonstrates that viral RNA synthesis is drastically decreased. In vitro synthesis experiments using the viral recombinant polymerase show that modifications of intra-molecular interactions have no effect on RNA synthesis, while impairing inter-molecular interactions decreases polymerase activity. This confirms that dimeric templates are preferentially replicated by the viral polymerase. Altogether, these results indicate that the dimerization of the HCV genomic RNA is a crucial step for the viral life cycle especially for RNA replication. RNA dimerization could explain the existence of HCV recombinants in cell culture and patients reported recently in other studies.

Characterization of hepatitis C virus intergenotypic recombinant strains and associated virological response to sofosbuvir/ribavirin

To date, intergenotypic recombinant hepatitis C viruses (HCVs) and their treatment outcomes have not been well characterized. This study characterized 12 novel HCV recombinant strains and their response to sofosbuvir in combination with ribavirin (SOF/RBV) treatment. Across the phase II/III studies of SOF, HCV samples were genotyped using both the Siemens VERSANT HCV Genotype INNO-LiPA 2.0 Assay (Innogenetics, Ghent, Belgium) and nonstructural (NS)5B sequencing. Among these patient samples, genotype assignment discordance between the two methods was found in 0.5% of all cases (12 of 2,363), of which all were identified as genotype 2 by INNO-LiPA (12 of 487; 2.5%). HCV full-genome sequences were obtained for these 12 samples by a sequence-independent amplification method coupled with next-generation sequencing. HCV full-genome sequencing revealed that these viruses were recombinant HCV strains, with the 5' part corresponding to genotype 2 and the 3' part corresponding to genotype 1. The recombination breakpoint between genotypes 2 and 1 was consistently located within 80 amino acids of the NS2/NS3 junction. Interestingly, one of the recombinant viruses had a 34-amino-acid duplication at the location of the recombination breakpoint. Eleven of these twelve patients were treated with a regimen for genotype 2 HCV infection, but responded as if they had genotype 1 infection; 1 patient had received placebo.

CONCLUSION

Twelve new HCV intergenotypic recombinant genotype 2/1 viruses have been characterized. The antiviral response to a 12- to 16-week course of SOF/RBV treatment in these patients was more similar to responses among genotype 1 patients than genotype 2 patients, consistent with their genotype 1 NS5B gene.

High-resolution hepatitis C virus subtyping using NS5B deep sequencing and phylogeny, an alternative to current methods

Hepatitis C virus (HCV) is classified into seven major genotypes and 67 subtypes. Recent studies have shown that in HCV genotype 1-infected patients, response rates to regimens containing direct-acting antivirals (DAAs) are subtype dependent. Currently available genotyping methods have limited subtyping accuracy. We have evaluated the performance of a deep-sequencing-based HCV subtyping assay, developed for the 454/GS-Junior platform, in comparison with those of two commercial assays (Versant HCV genotype 2.0 and Abbott Real-time HCV Genotype II) and using direct NS5B sequencing as a gold standard (direct sequencing), in 114 clinical specimens previously tested by first-generation hybridization assay (82 genotype 1 and 32 with uninterpretable results). Phylogenetic analysis of deep-sequencing reads matched subtype 1 calling by population Sanger sequencing (69% 1b, 31% 1a) in 81 specimens and identified a mixed-subtype infection (1b/3a/1a) in one sample. Similarly, among the 32 previously indeterminate specimens, identical genotype and subtype results were obtained by direct and deep sequencing in all but four samples with dual infection. In contrast, both Versant HCV Genotype 2.0 and Abbott Real-time HCV Genotype II failed subtype 1 calling in 13 (16%) samples each and were unable to identify the HCV genotype and/or subtype in more than half of the non-genotype 1 samples. We concluded that deep sequencing is more efficient for HCV subtyping than currently available methods and allows qualitative identification of mixed infections and may be more helpful with respect to informing treatment strategies with new DAA-containing regimens across all HCV subtypes.

Analysis of the evolution and structure of a complex intrahost viral population in chronic hepatitis C virus mapped by ultradeep pyrosequencing

Hepatitis C virus (HCV) causes chronic infection in up to 50% to 80% of infected individuals. Hypervariable region 1 (HVR1) variability is frequently studied to gain an insight into the mechanisms of HCV adaptation during chronic infection, but the changes to and persistence of HCV subpopulations during intrahost evolution are poorly understood. In this study, we used ultradeep pyrosequencing (UDPS) to map the viral heterogeneity of a single patient over 9.6 years of chronic HCV genotype 4a infection. Informed error correction of the raw UDPS data was performed using a temporally matched clonal data set. The resultant data set reported the detection of low-frequency recombinants throughout the study period, implying that recombination is an active mechanism through which HCV can explore novel sequence space. The data indicate that polyvirus infection of hepatocytes has occurred but that the fitness quotients of recombinant daughter virions are too low for the daughter virions to compete against the parental genomes. The subpopulations of parental genomes contributing to the recombination events highlighted a dynamic virome where subpopulations of variants are in competition. In addition, we provide direct evidence that demonstrates the growth of subdominant populations to dominance in the absence of a detectable humoral response.

IMPORTANCE

Analysis of ultradeep pyrosequencing data sets derived from virus amplicons frequently relies on software tools that are not optimized for amplicon analysis, assume random incorporation of sequencing errors, and are focused on achieving higher specificity at the expense of sensitivity. Such analysis is further complicated by the presence of hypervariable regions. In this study, we made use of a temporally matched reference sequence data set to inform error correction algorithms. Using this methodology, we were able to (i) detect multiple instances of hepatitis C virus intrasubtype recombination at the E1/E2 junction (a phenomenon rarely reported in the literature) and (ii) interrogate the longitudinal quasispecies complexity of the virome. Parallel to the UDPS, isolation of IgG-bound virions was found to coincide with the collapse of specific viral subpopulations.

Evaluation of the Abbott realtime HCV genotype II RUO (GT II) assay with reference to 5'UTR, core and NS5B sequencing

BACKGROUND

HCV genotyping is a critical tool for guiding initiation of therapy and selecting the most appropriate treatment regimen.

OBJECTIVE

To evaluate the concordance between the Abbott GT II assay and genotyping by sequencing subregions of the HCV 5'UTR, core and NS5B.

STUDY DESIGN

The Abbott assay was used to genotype 127 routine patient specimens and 35 patient specimens with unusual subtypes and mixed infection. Abbott results were compared to genotyping by 5'UTR, core and NS5B sequencing. Sequences were genotyped using the NCBI non-redundant database and the online genotyping tool COMET.

RESULTS

Among routine specimens, core/NS5B sequencing identified 93 genotype 1s, 13 genotype 2s, 15 genotype 3s, three genotype 4s, two genotype 6s and one recombinant specimen. Genotype calls by 5'UTR, core, NS5B sequencing and the Abbott assay were 97.6% concordant. Core/NS5B sequencing identified two discrepant samples as genotype 6 (subtypes 6l and 6u) while Abbott and 5'UTR sequencing identified these samples as genotype 1 with no subtype. The Abbott assay subtyped 91.4% of genotype 1 specimens. Among the 35 rare specimens, the Abbott assay inaccurately genotyped 3k, 6e, 6o, 6q and one genotype 4 variant; gave indeterminate results for 3g, 3h, 4r, 6m, 6n, and 6q specimens; and agreed with core/NS5B sequencing for mixed specimens.

CONCLUSIONS

The Abbott assay is an automated HCV genotyping method with improved accuracy over 5'UTR sequencing. Samples identified by the Abbott assay as genotype 1 with no subtype may be rare subtypes of other genotypes and thus require confirmation by another method.

Phylogenetic and molecular characterization of chicken anemia virus in southern China from 2011 to 2012

Chicken anemia virus (CAV) is an important pathogen that causes severe immunosuppression in young chickens. We have characterized 13 CAVs isolated from different commercial farms in southern China between 2011 and 2012. We discovered 92 variable residues compared to 37 other CAV complete genome sequences from other parts of the world listed in GenBank; these residues have not been previously observed. All of the Chinese CAV genomes that were characterized in this study had a glutamine at position 394, a hallmark of highly pathogenic CAVs. We also discovered that intra-group genetic recombination plays a role in generating genetic diversity in natural populations of CAV. The GD-J-12 isolate was a possible recombinant between GD-C-12 and GD-M-12 in the genomic region that encompassed both the coding and non-coding regions.

Phylogeny and molecular evolution of the hepatitis C virus

The hepatitis C virus (HCV) is a globally prevalent human pathogen that causes persistent liver infections in most infected individuals. HCV is classified into seven phylogenetically distinct genotypes, which have different geographical distributions and levels of genetic diversity. Some of these genotypes are endemic and highly divergent, whereas others disseminate rapidly on an epidemic scale but display lower variability. HCV phylogeny has an important impact on disease epidemiology and clinical practice because the viral genotype may determine the pathogenesis and severity of the resultant chronic liver disease. In addition, there is a clear association between the HCV genotype and its susceptibility to antiviral treatment. Similarly to other RNA viruses, in a single host, HCV exists as a combination of related but genetically different variants. The whole formation is the actual target of selection exerted by a host organism and antiviral therapeutics. The genetic structure of the viral population is largely shaped by mutations that are constantly introduced during an error-prone replication. However, it appears that genetic recombination may also contribute to this process. This heterogeneous collection of variants has a significant ability to evolve towards the fitness optimum. Interestingly, negative selection, which restricts diversity, emerges as an essential force that drives HCV evolution. It is becoming clear that HCV evolves to become stably adapted to the host environment. In this article we review the HCV phylogeny and molecular evolution in the context of host-virus interactions.

Whole genome pyrosequencing of rare hepatitis C virus genotypes enhances subtype classification and identification of naturally occurring drug resistance variants

BACKGROUND

 Infection with hepatitis C virus (HCV) is a burgeoning worldwide public health problem, with 170 million infected individuals and an estimated 20 million deaths in the coming decades. While 6 main genotypes generally distinguish the global geographic diversity of HCV, a multitude of closely related subtypes within these genotypes are poorly defined and may influence clinical outcome and treatment options. Unfortunately, the paucity of genetic data from many of these subtypes makes time-consuming primer walking the limiting step for sequencing understudied subtypes.

METHODS

 Here we combined long-range polymerase chain reaction amplification with pyrosequencing for a rapid approach to generate the complete viral coding region of 31 samples representing poorly defined HCV subtypes.

RESULTS

 Phylogenetic classification based on full genome sequences validated previously identified HCV subtypes, identified a recombinant sequence, and identified a new distinct subtype of genotype 4. Unlike conventional sequencing methods, use of deep sequencing also facilitated characterization of minor drug resistance variants within these uncommon or, in some cases, previously uncharacterized HCV subtypes.

CONCLUSIONS

 These data aid in the classification of uncommon HCV subtypes while also providing a high-resolution view of viral diversity within infected patients, which may be relevant to the development of therapeutic regimens to minimize drug resistance.

Sequencing assays for failed genotyping with the versant hepatitis C virus genotype assay (LiPA), version 2.0

For optimal antiviral therapy, the hepatitis C virus (HCV) genotype needs to be determined, as it remains a strong predictor of sustained viral response. In this study, we assessed the number of HCV genotyping results that could not be determined using the commercially available line probe assay (LiPA) (Versant hepatitis C virus genotype 2.0 assay) in a large international panel of samples from 9,874 HCV-positive patients. In-house sequencing assays targeting the 5' untranslated region (UTR), core region, NS3 region, and NS5B region of the HCV genome and phylogenetic analyses were used to resolve these LiPA failures. Among all cases, the genotypes of 51 samples (0.52%) could not be determined with the LiPA. These undetermined results were observed more frequently among samples from non-European regions (mainly the Arabian Peninsula). The use of sequencing assays coupled with phylogenetic analysis provided reliable genotype results for 86% of the LiPA failures, which exhibited higher rates of genotypes 4, 5, and 6 than did LiPA-resolved genotypes. As expected, the 5' UTR was not sufficiently variable for clear discrimination between genotypes 1 and 6, but it also resulted in errors in classification of some genotype 3 and 4 cases using well-known Web-based BLAST programs. This study demonstrates the low frequency of genotyping failures with the Versant hepatitis C virus genotype 2.0 assay (LiPA) and also underlines the need for a complex combination of sequences and phylogenetic analyses in order to genotype these particular HCV strains correctly.

Productive homologous and non-homologous recombination of hepatitis C virus in cell culture

Genetic recombination is an important mechanism for increasing diversity of RNA viruses, and constitutes a viral escape mechanism to host immune responses and to treatment with antiviral compounds. Although rare, epidemiologically important hepatitis C virus (HCV) recombinants have been reported. In addition, recombination is an important regulatory mechanism of cytopathogenicity for the related pestiviruses. Here we describe recombination of HCV RNA in cell culture leading to production of infectious virus. Initially, hepatoma cells were co-transfected with a replicating JFH1ΔE1E2 genome (genotype 2a) lacking functional envelope genes and strain J6 (2a), which has functional envelope genes but does not replicate in culture. After an initial decrease in the number of HCV positive cells, infection spread after 13–36 days. Sequencing of recovered viruses revealed non-homologous recombinants with J6 sequence from the 5′ end to the NS2–NS3 region followed by JFH1 sequence from Core to the 3′ end. These recombinants carried duplicated sequence of up to 2400 nucleotides. HCV replication was not required for recombination, as recombinants were observed in most experiments even when two replication incompetent genomes were co-transfected. Reverse genetic studies verified the viability of representative recombinants. After serial passage, subsequent recombination events reducing or eliminating the duplicated region were observed for some but not all recombinants. Furthermore, we found that inter-genotypic recombination could occur, but at a lower frequency than intra-genotypic recombination. Productive recombination of attenuated HCV genomes depended on expression of all HCV proteins and tolerated duplicated sequence. In general, no strong site specificity was observed. Non-homologous recombination was observed in most cases, while few homologous events were identified. A better understanding of HCV recombination could help identification of natural recombinants and thereby lead to improved therapy. Our findings suggest mechanisms for occurrence of recombinants observed in patients.

Genetic recombination is the alternative joining of nucleic acids leading to novel combinations of genetic information. While DNA recombination in cells is of importance for evolution and adaptive immunity, RNA recombination often has only transient effects. However, RNA viruses are rapidly evolving and recombination can be an important evolutionary step in addition to mutations introduced by the viral polymerase. Recombination can allow escape from the host immune system and from antiviral treatment, and recombination of live attenuated viral vaccines has led to re-emergence of disease. Hepatitis C virus (HCV) is an important human pathogen that chronically infects more than 130 million worldwide and leads to serious liver disease. For HCV, naturally occurring recombinants are rare but clinically important. HCV recombination constitutes a challenge to antiviral treatment and can potentially provide an escape mechanism for the virus. In this study, we established an assay for HCV RNA recombination and characterized the emerging homologous and non-homologous recombinant viruses. Interestingly, recombination did not depend on viral replication, occurred most efficiently between isolates of the same genotype and did not occur with strong site-specificity. Better diagnosis of clinically important recombinants and an increased knowledge on viral recombination could strengthen antiviral and vaccine development.

Natural selection of adaptive mutations in non-structural genes increases trans-encapsidation of hepatitis C virus replicons lacking envelope protein genes

A trans-packaging system for hepatitis C virus (HCV) replicons lacking envelope glycoproteins was developed. The replicons were efficiently encapsidated into infectious particles after expression in trans of homologous HCV envelope proteins under the control of an adenoviral vector. Interestingly, expression in trans of core or core, p7 and NS2 with envelope proteins did not enhance trans-encapsidation. Expression of heterologous envelope proteins, in the presence or absence of heterologous core, p7 and NS2, did not rescue single-round infectious particle production. To increase the titre of homologous, single-round infectious particles in our system, successive cycles of trans-encapsidation and infection were performed. Four cycles resulted in a 100-fold increase in the yield of particles. Sequence analysis revealed a total of 16 potential adaptive mutations in two independent experiments. Except for a core mutation in one experiment, all the mutations were located in non-structural regions mainly in NS5A (four in domain III and two near the junction with the NS5B gene). Reverse genetics studies suggested that D2437A and S2443T adaptive mutations, which are located at the NS5A-B cleavage site did not affect viral replication, but enhanced the single-round infectious particles assembly only in trans-encapsidation model. In conclusion, our trans-encapsidation system enables the production of HCV single-round infectious particles. This system is adaptable and can positively select variants. The adapted variants promote trans-encapsidation and should constitute a valuable tool in the development of replicon-based HCV vaccines.

Insertion and recombination events at hypervariable region 1 over 9.6 years of hepatitis C virus chronic infection

Hepatitis C virus (HCV) exists as a quasispecies within an infected individual. We have previously reported an in-frame 3 bp insertion event at the N-terminal region of the E2 glycoprotein from a genotype 4a HCV isolate giving rise to an atypical 28 aa hypervariable region (HVR) 1. To further explore quasispecies evolution at the HVR1, serum samples collected over 9.6 years from the same chronically infected, treatment naïve individual were subjected to retrospective clonal analysis. Uniquely, we observed that isolates containing this atypical HVR1 not only persisted for 7.6 years, but dominated the quasispecies swarm. Just as striking was the collapse of this population of variants towards the end of the sampling period in synchrony with variants containing a classical HVR1 from the same lineage. The replication space was subsequently occupied by a second minor lineage, which itself was only intermittently detectable at earlier sampling points. In conjunction with the observed genetic shift, the coexistence of two distinct HVR1 populations facilitated the detection of putative intra-subtype recombinants, which included the identification of the likely ancestral parental donors. Juxtaposed to the considerable plasticity of the HVR1, we also document a degree of mutational inflexibility as each of the HVR1 subpopulations within our dataset exhibited overall genetic conservation and convergence. Finally, we raise the issue of genetic analysis in the context of mixed lineage infections.