Comparison of Nanopore and Synthesis-Based Next-Generation Sequencing Platforms for SARS-CoV-2 Variant Monitoring in Wastewater.

Shortly after the beginning of the SARS-CoV-2 pandemic, many countries implemented sewage sentinel systems to monitor the circulation of the virus in the population. A fundamental part of these surveillance programs is the variant tracking through sequencing approaches to monitor and identify new variants or mutations that may be of importance. Two of the main sequencing platforms are Illumina and Oxford Nanopore Technologies. Here, we compare the performance of MiSeq (Illumina) and MinION (Oxford Nanopore Technologies), as well as two different data processing pipelines, to determine the effect they may have on the results. MiSeq showed higher sequencing coverage, lower error rate, and better capacity to detect and accurately estimate variant abundances than MinION R9.4.1 flow cell data. The use of different variant callers (LoFreq and iVar) and approaches to calculate the variant proportions had a remarkable impact on the results generated from wastewater samples. Freyja, coupled with iVar, may be more sensitive and accurate than LoFreq, especially with MinION data, but it comes at the cost of having a higher error rate. The analysis of MinION R10.4.1 flow cell data using Freyja combined with iVar narrows the gap with MiSeq performance in terms of read quality, accuracy, sensitivity, and number of detected mutations. Although MiSeq should still be considered as the standard method for SARS-CoV-2 variant tracking, MinION's versatility and rapid turnaround time may represent a clear advantage during the ongoing pandemic.

In-Host HEV Quasispecies Evolution Shows the Limits of Mutagenic Antiviral Treatments.

Here, we report the in-host hepatitis E virus (HEV) quasispecies evolution in a chronically infected patient who was treated with three different regimens of ribavirin (RBV) for nearly 6 years. Sequential plasma samples were collected at different time points and subjected to RNA extraction and deep sequencing using the MiSeq Illumina platforms. Specifically, we RT-PCR amplified a single amplicon from the core region located in the open-reading frame 2 (ORF2). At the nucleotide level (genotype), our analysis showed an increase in the number of rare haplotypes and a drastic reduction in the frequency of the master (most represented) sequence during the period when the virus was found to be insensitive to RBV treatment. Contrarily, at the amino acid level (phenotype), our study revealed conservation of the amino acids, which is represented by a high prevalence of the master sequence. Our findings suggest that using mutagenic antivirals concomitant with high viral loads can lead to the selection and proliferation of a rich set of synonymous haplotypes that express the same phenotype. This can also lead to the selection and proliferation of conservative substitutions that express fitness-enhanced phenotypes. These results have important clinical implications, as they suggest that using mutagenic agents as a monotherapy treatment regimen in the absence of sufficiently effective viral inhibitors can result in diversification and proliferation of a highly diverse quasispecies resistant to further treatment. Therefore, such approaches should be avoided whenever possible.

Dynamics of SARS-CoV-2 Alpha (B.1.1.7) variant spread: The wastewater surveillance approach.

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.

Quasispecies Fitness Partition to Characterize the Molecular Status of a Viral Population. Negative Effect of Early Ribavirin Discontinuation in a Chronically Infected HEV Patient.

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 <0.1%, and those at 0.1−1%), and a fourth fraction that we term emerging haplotypes, present at frequencies >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.

Broad and Dynamic Diversification of Infectious Hepatitis C Virus in a Cell Culture Environment.

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.

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

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

Monitoring Emergence of the SARS-CoV-2 B.1.1.7 Variant through the Spanish National SARS-CoV-2 Wastewater Surveillance System (VATar COVID-19).

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.

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

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

Hepatitis C virus intrinsic molecular determinants may contribute to the development of cholestatic hepatitis after liver transplantation.

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.

HIV-1 Protease Evolvability Is Affected by Synonymous Nucleotide Recoding.

One unexplored aspect of HIV-1 genetic architecture is how codon choice influences population diversity and evolvability. Here we compared the levels of development of HIV-1 resistance to protease inhibitors (PIs) between wild-type (WT) virus and a synthetic virus (MAX) carrying a codon-pair-reengineered protease sequence including 38 (13%) synonymous mutations. The WT and MAX viruses showed indistinguishable replication in MT-4 cells or peripheral blood mononuclear cells (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 (50% inhibitory concentrations [IC50s] of 14.6 ± 5.3 and 21.2 ± 9 nM, respectively, for ATV and 5.9 ± 1.0 and 9.3 ± 1.9, respectively, for DRV). Ultradeep sequence clonal analysis revealed that both viruses harbored previously described mutations conferring resistance 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 the WT and the L33F, S37P, G48L, Q58E/K, and L89I substitutions detected only in the MAX virus. Remarkably, the G48L and L89I substitutions are rarely found in vivo in 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 a higher selective pressure for change in this recoded virus. Our results indicate that the HIV-1 protease position in sequence space delineates the evolution of its mutant spectrum. Nevertheless, the investigated synonymously recoded variant showed mutational robustness and evolvability similar to those of the WT virus.IMPORTANCE Large-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 affects 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 a virus with recoded protease exhibited different patterns of resistance mutations after PI treatment. Nevertheless, the developed PI resistance phenotypes were indistinguishable between the recoded virus and the WT virus, suggesting that the HIV-1 strain with synonymously recoded protease and the WT virus are equally robust and evolvable.

New hepatitis C virus genotype 1 subtype naturally harbouring resistance-associated mutations to NS5A inhibitors.

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.

Pipeline for specific subtype amplification and drug resistance detection in hepatitis C virus.

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.

Assessment of a Novel Automatic Real-Time PCR Assay on the Cobas 4800 Analyzer as a Screening Platform for Hepatitis C Virus Genotyping in Clinical Practice: Comparison with Massive Sequencing.

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.

Quasispecies dynamics in hepatitis C liver transplant recipients receiving grafts from hepatitis C virus infected donors.

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.

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.

Identification of host and viral factors involved in a dissimilar resolution of a hepatitis C virus infection.

BACKGROUND & AIMS: Hepatitis C virus (HCV) transmission from a chronic patient to a susceptible individual is a good opportunity to study viral and host factors that may influence the natural course of hepatitis C infection towards either spontaneous recovery or chronicity. To compare a documented case of a bottleneck event in the sexual transmission of HCV from a chronically infected patient to a recipient host that cleared infection. METHODS: Host genetic components such as Class I and II HLA and IL28B polymorphism (rs12979860 SNPs) were identified by direct sequencing and LightMix analysis, respectively. Deep nucleotide sequence analysis of quasispecies complexity was performed using massive pyrosequencing platform (454 GS-FLX), and the CD4 specific immune response was characterized by ELISPOT. RESULTS AND CONCLUSIONS: Sequencing analysis and CD4 response highlighted several NS3-helicase domains in which an interplay between amino acid variability and CD4 immune response might have contributed either to chronicity in the donor patient or to viral clearance in the receptor (newly infected) patient.

In-Host Flat-like Quasispecies: Characterization Methods and Clinical Implications.

The repeated failure to treat patients chronically infected with hepatitis E (HEV) and C (HCV) viruses, despite the absence of resistance-associated substitutions (RAS), particularly in response to prolonged treatments with the mutagenic agents of HEV, suggests that quasispecies structure may play a crucial role beyond single point mutations. Quasispecies structured in a flat-like manner (referred to as flat-like) are considered to possess high average fitness, occupy a significant fraction of the functional genetic space of the virus, and exhibit a high capacity to evade specific or mutagenic treatments. In this paper, we studied HEV and HCV samples using high-depth next-generation sequencing (NGS), with indices scoring the different properties describing flat-like quasispecies. The significance of these indices was demonstrated by comparing the values obtained from these samples with those from acute infections caused by respiratory viruses (betacoronaviruses, enterovirus, respiratory syncytial viruses, and metapneumovirus). Our results revealed that flat-like quasispecies in HEV and HCV chronic infections without RAS are characterized by numerous low-frequency haplotypes with no dominant one. Surprisingly, these low-frequency haplotypes (at the nucleotide level) exhibited a high level of synonymity, resulting in much lower diversity at the phenotypic level. Currently, clinical approaches for managing flat-like quasispecies are lacking. Here, we propose methods to identifying flat-like quasispecies, which represents an essential initial step towards exploring alternative treatment protocols for viruses resistant to conventional therapies.

Complete Genome Sequences of Four Mycobacteriophages Involved in Directed Evolution against Undisputed Mycobacterium abscessus Clinical Strains.

Phage therapy is still in its infancy, but it is increasingly promising as a future alternative for treating antibiotic-resistant bacteria. To investigate the effect of phages on Mycobacterium abscessus complex (MABC), we isolated 113 environmental phages, grown them to high titres, and assayed them on MABC clinical strains through the spot test. Of all the phages, only 16 showed killing activity. Their activity was so temperate to MABC that they could not generate any plaque-forming units (PFUs). The Appelmans method of directed evolution was carried out to evolve these 16 phages into more lytic ones. After only 11 of 30 rounds of evolution, every single clinical strain in our collection, including those that were unsusceptible up to this point, could be lysed by at least one phage. The evolved phages were able to form PFUs on the clinical strains tested. Still, they are temperate at best and require further training. The genomes of one random parental phage and three random evolved phages from Round 13 were sequenced, revealing a diversity of clusters and genes of a variety of evolutionary origins, mostly of unknown function. These complete annotated genomes will be key for future molecular characterisations.

Bioinformatic Tools for NGS-Based Metagenomics to Improve the Clinical Diagnosis of Emerging, Re-Emerging and New Viruses.

Epidemics and pandemics have occurred since the beginning of time, resulting in millions of deaths. Many such disease outbreaks are caused by viruses. Some viruses, particularly RNA viruses, are characterized by their high genetic variability, and this can affect certain phenotypic features: tropism, antigenicity, and susceptibility to antiviral drugs, vaccines, and the host immune response. The best strategy to face the emergence of new infectious genomes is prompt identification. However, currently available diagnostic tests are often limited for detecting new agents. High-throughput next-generation sequencing technologies based on metagenomics may be the solution to detect new infectious genomes and properly diagnose certain diseases. Metagenomic techniques enable the identification and characterization of disease-causing agents, but they require a large amount of genetic material and involve complex bioinformatic analyses. A wide variety of analytical tools can be used in the quality control and pre-processing of metagenomic data, filtering of untargeted sequences, assembly and quality control of reads, and taxonomic profiling of sequences to identify new viruses and ones that have been sequenced and uploaded to dedicated databases. Although there have been huge advances in the field of metagenomics, there is still a lack of consensus about which of the various approaches should be used for specific data analysis tasks. In this review, we provide some background on the study of viral infections, describe the contribution of metagenomics to this field, and place special emphasis on the bioinformatic tools (with their capabilities and limitations) available for use in metagenomic analyses of viral pathogens.

Next-Generation Sequencing for Confronting Virus Pandemics.

Virus pandemics have happened, are happening and will happen again. In recent decades, the rate of zoonotic viral spillover into humans has accelerated, mirroring the expansion of our global footprint and travel network, including the expansion of viral vectors and the destruction of natural spaces, bringing humans closer to wild animals. Once viral cross-species transmission to humans occurs, transmission cannot be stopped by cement walls but by developing barriers based on knowledge that can prevent or reduce the effects of any pandemic. Controlling a local transmission affecting few individuals is more efficient that confronting a community outbreak in which infections cannot be traced. Genetic detection, identification, and characterization of infectious agents using next-generation sequencing (NGS) has been proven to be a powerful tool allowing for the development of fast PCR-based molecular assays, the rapid development of vaccines based on mRNA and DNA, the identification of outbreaks, transmission dynamics and spill-over events, the detection of new variants and treatment of vaccine resistance mutations, the development of direct-acting antiviral drugs, the discovery of relevant minority variants to improve knowledge of the viral life cycle, strengths and weaknesses, the potential for becoming dominant to take appropriate preventive measures, and the discovery of new routes of viral transmission.