Virus Evolution最新文献

The Apicomplexa are a phylum of single-celled eukaryotes that can infect humans and include the mosquito-borne parasite Plasmodium, the cause of malaria. Viruses that infect non-Plasmodium spp. disease-causing protozoa affect the pathogen life cycle and disease outcomes. However, only one RNA virus (Matryoshka RNA virus 1) has been identified in Plasmodium, and none have been identified in zoonotic Plasmodium species. The rapid expansion of the known RNA virosphere via metagenomic sequencing suggests that this dearth is due to the divergent nature of RNA viruses that infect protozoa. We leveraged newly uncovered data sets to explore the virome of human-infecting Plasmodium species collected in Sabah, east (Borneo) Malaysia. From this, we identified a highly divergent RNA virus in two human-infecting P. knowlesi isolates that is related to the unclassified group 'ormycoviruses'. By characterizing 15 additional ormycoviruses identified in the transcriptomes of arthropods, we show that this group of viruses exhibits a complex ecology as noninfecting passengers at the arthropod-mammal interface. With the addition of viral diversity discovered using the artificial intelligence-based analysis of metagenomic data, we also demonstrate that the ormycoviruses are part of a diverse and unclassified viral taxon. This is the first observation of an RNA virus in a zoonotic Plasmodium species. By linking small-scale experimental data to advances in large-scale virus discovery, we characterize the diversity and confirm the putative genomic architecture of an unclassified viral taxon. This approach can be used to further explore the virome of disease-causing Apicomplexa and better understand how protozoa-infecting viruses may affect parasite fitness, pathobiology, and treatment outcomes.

The order Tymovirales currently comprises five viral families with positive-sense RNA [(+)RNA] genomes that infect plants, fungi, and insects. Virion morphologies within the order Tymovirales differ between families, with icosahedral virions in the Tymoviridae and filamentous virions in the other "flexi"viridae families. Despite their different morphologies, these viruses are placed in the same order based on phylogenetic analyses of replicase-associated polyproteins. However, one of the families in the Tymovirales, Deltaflexiviridae, is considered to be capsidless because there have been no published reports of virion isolation. Here, we report that a new "flexivirus"-related (+)RNA virus, prospectively named Fusarium oxysporum icosahedral virus 1 (FoIV1), is icosahedral and that most deltaflexiviruses may have icosahedral virions. Phylogenetic analyses based on replicase-associated polyproteins indicated that FoIV1 forms a distinct group in the Tymovirales with some viruses originally assigned to the Deltaflexiviridae. Electron microscopy, protein analysis, and protein structure predictions indicate that FoIV1 open reading frame 4 encodes a single jelly-roll (SJR)-like coat protein (CP) that constitutes the icosahedral virions. Results of clustering analyses based on amino acid sequences and predicted CP structures suggested that most of the deltaflexiviruses have icosahedral virions composed of SJR-like CPs as in FoIV1, rather than having filamentous virions or capsidless. These results challenge the conventional understanding of viruses in the order Tymovirales, with important implications for revising its taxonomic framework and providing insights into the evolutionary relationships within this diverse and broad host range group of (+)RNA viruses.

Accurately identifying mutations under beneficial selection in viral genomes is crucial for understanding their molecular evolution and pathogenicity. Traditional methods like the Ka/Ks test, which assesses non-synonymous (Ka) versus synonymous (Ks) substitution rates, assume that synonymous substitutions at synonymous sites are neutral and thus is equal to the mutation rate (µ). Yet, evidence suggests that synonymous sites in translated regions (TRs) and untranslated regions (UTRs) can be under strong beneficial selection (Ks > µ) and strongly conserved (Ks ≈ 0), leading to false predictions of adaptive mutations from codon-by-codon Ka/Ks analysis. Our previous work used a relative substitution rate test (c/µ, c: substitution rate in UTR/TR, and µ: mutation rate) to identify adaptive mutations in SARS-CoV-2 genome without the neutrality assumption of the synonymous sites. This study refines the c/µ test by optimizing µ value, leading to a smaller set of nucleotide and amino acid sites under beneficial selection in both UTR (11 sites with c/µ > 3) and TR (69 nonsynonymous sites: c/µ > 3 and Ka/Ks > 2.5; 107 synonymous sites: Ks/µ > 3). Encouragingly, the top two mutations in UTR and 70% of the top nonsynonymous mutations in TR had reported or predicted effects in the literature. Molecular modeling of top adaptive mutations for some critical proteins (S, NSP11, and NSP5) was carried out to elucidate the possible molecular mechanism of their adaptivity.

The Bronx, New York, exhibited unique peaks in the number of coronavirus disease 2019 (COVID-19) cases and hospitalizations compared to national trends. To determine which features of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus might underpin this local disease epidemiology, we conducted a comprehensive analysis of the genomic epidemiology of the four dominant strains of SARS-CoV-2 (Alpha, Iota, Delta, and Omicron) responsible for COVID-19 cases in the Bronx between March 2020 and January 2023. Genomic analysis revealed similar viral fitness for Alpha and Iota variants in the Bronx despite nationwide data showing higher cases of Alpha. However, Delta and Omicron variants had increased fitness within the borough. While the transmission dynamics of most variants in the Bronx corresponded with mutational fitness-based predictions of transmissibility, the Delta variant presented as an exception. Epidemiological modeling confirms Delta's advantages of higher transmissibility in Manhattan and Queens, but not the Bronx; wastewater analysis suggests underdetection of cases in the Bronx. The Alpha variant had slightly faster growth but a lower carrying capacity compared to Iota and Delta in all four boroughs, suggesting stronger limitations on Alpha's growth in New York City (NYC). The founder effect of Iota varied between higher vaccinated and lower vaccinated boroughs with longer delay, shorter duration, and lower fitness of the Alpha variant in lower vaccinated boroughs. Amino acid changes in T-cell and antibody epitopes revealed Delta and Iota having larger antigenic variability and antigenic profiles distant from local previously circulating lineages compared to Alpha. In concert with transmission modeling, our data suggest that the limited spread of Alpha may be due to a lack of adaptation to immunity in NYC. Overall, our study demonstrates that localized analyses and integration of orthogonal community-level datasets can provide key insights into the mechanisms of transmission and immunity patterns associated with regional COVID-19 incidence and disease severity that may be missed when analyzing broader datasets.

In response to the escalating SARS-CoV-2 pandemic, in March 2020 the COVID-19 Genomics UK (COG-UK) consortium was established to enable national-scale genomic surveillance in the UK. By the end of 2020, 49% of all SARS-CoV-2 genome sequences globally had been generated as part of the COG-UK programme, and to date, this system has generated >3 million SARS-CoV-2 genomes. Rapidly and reliably analysing this unprecedented number of genomes was an enormous challenge. To fulfil this need and to inform public health decision-making, we developed a centralized pipeline that performs quality control, alignment, and variant calling and provides the global phylogenetic context of sequences. We present this pipeline and describe how we tailored it as the pandemic progressed to scale with the increasing amounts of data and to provide the most relevant analyses on a daily basis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the coronavirus disease 2019 (COVID-19) pandemic, which is still a global public health concern. During March 2022, a rapid and confined single-source outbreak of SARS-CoV-2 was identified in a community in Nanjing municipal city. Overall, 95 individuals had laboratory-confirmed SARS-CoV-2 infection. The whole genomes of 61 viral samples were obtained, which were all members of the BA.2.2 lineage and clearly demonstrated the presence of one large clade, and all the infections could be traced back to the original index case. The most distant sequence from the index case presented a difference of 4 SNPs, and 118 intrahost single-nucleotide variants (iSNVs) at 74 genomic sites were identified. Some minor iSNVs can be transmitted and subsequently rapidly fixed in the viral population. The minor iSNVs transmission resulted in at least two nucleotide substitutions among all seven SNPs identified in the outbreak, generating genetically diverse populations. We estimated the overall transmission bottleneck size to be 3 using 11 convincing donor-recipient transmission pairs. Our study provides new insights into genomic epidemiology and viral transmission, revealing how iSNVs become fixed in local clusters, followed by viral transmission across the community, which contributes to population diversity.

Ostreid herpesvirus 1 (OsHV-1), a member of the family Malacoherpesviridae (order Herpesvirales), is a major pathogen of bivalves. However, the molecular details of the malacoherpesvirus infection cycle and its overall similarity to the replication of mammalian herpesviruses (family Orthoherpesviridae) remain obscure. Here, to gain insights into the OsHV-1 biology, we performed long-read sequencing of infected blood clams, Anadara broughtonii, which yielded over one million OsHV-1 long reads. These data enabled the annotation of the viral genome with 78 gene units and 274 transcripts, of which 67 were polycistronic mRNAs, 35 ncRNAs, and 20 natural antisense transcripts (NATs). Transcriptomics and proteomics data indicate preferential transcription and independent translation of the capsid scaffold protein as an OsHV-1 capsid maturation protease isoform. The conservation of this transcriptional architecture across Herpesvirales likely indicates its functional importance and ancient origin. Moreover, we traced RNA editing events using short-read sequencing and supported the presence of inosine nucleotides in native OsHV-1 RNA, consistent with the activity of adenosine deaminase acting on dsRNA 1 (ADAR1). Our data suggest that, whereas RNA hyper-editing is concentrated in specific regions of the OsHV-1 genome, single-nucleotide editing is more dispersed along the OsHV-1 transcripts. In conclusion, we reveal the existence of conserved pan-Herpesvirales transcriptomic architecture of the capsid maturation module and uncover a transcription-based viral counter defence mechanism, which presumably facilitates the evasion of the host ADAR antiviral system.

The experimental validation of theoretical predictions is a crucial step in demonstrating the predictive power of a model. While quantitative validations are common in infectious diseases epidemiology, experimental microbiology primarily focuses on the evaluation of a qualitative match between model predictions and experiments. In this study, we develop a method to deepen the quantitative validation process with a polymorphic viral population. We analyse the data from an experiment carried out to monitor the evolution of the temperate bacteriophage λ spreading in continuous cultures of Escherichia coli. This experimental work confirmed the influence of the epidemiological dynamics on the evolution of transmission and virulence of the virus. A variant with larger propensity to lyse bacterial cells was favoured in emerging epidemics (when the density of susceptible cells was large), but counter-selected when most cells were infected. Although this approach qualitatively validated an important theoretical prediction, no attempt was made to fit the model to the data nor to further develop the model to improve the goodness of fit. Here, we show how theoretical analysis-including calculations of the selection gradients-and model fitting can be used to estimate key parameters of the phage life cycle and yield new insights on the evolutionary epidemiology of the phage λ. First, we show that modelling explicitly the infected bacterial cells which will eventually be lysed improves the fit of the transient dynamics of the model to the data. Second, we carry out a theoretical analysis that yields useful approximations that capture at the onset and at the end of an epidemic the effects of epidemiological dynamics on selection and differentiation across distinct life stages of the virus. Finally, we estimate key phenotypic traits characterizing the two strains of the virus used in our experiment such as the rates of prophage reactivation or the probabilities of lysogenization. This study illustrates the synergy between experimental, theoretical, and statistical approaches; and especially how interpreting the temporal variation in the selection gradient and the differentiation across distinct life stages of a novel variant is a powerful tool to elucidate the evolutionary epidemiology of emerging infectious diseases.

Modern phylogenetics research is often performed within a Bayesian framework, using sampling algorithms such as Markov chain Monte Carlo (MCMC) to approximate the posterior distribution. These algorithms require careful evaluation of the quality of the generated samples. Within the field of phylogenetics, one frequently adopted diagnostic approach is to evaluate the effective sample size and to investigate trace graphs of the sampled parameters. A major limitation of these approaches is that they are developed for continuous parameters and therefore incompatible with a crucial parameter in these inferences: the tree topology. Several recent advancements have aimed at extending these diagnostics to topological space. In this reflection paper, we present two case studies-one on Ebola virus and one on HIV-illustrating how these topological diagnostics can contain information not found in standard diagnostics, and how decisions regarding which of these diagnostics to compute can impact inferences regarding MCMC convergence and mixing. Our results show the importance of running multiple replicate analyses and of carefully assessing topological convergence using the output of these replicate analyses. To this end, we illustrate different ways of assessing and visualizing the topological convergence of these replicates. Given the major importance of detecting convergence and mixing issues in Bayesian phylogenetic analyses, the lack of a unified approach to this problem warrants further action, especially now that additional tools are becoming available to researchers.

While influenza A virus (IAV) antigenic drift has been documented globally, in experimental animal infections, and in immunocompromised hosts, positive selection has generally not been detected in acute infections. This is likely due to challenges in distinguishing selected rare mutations from sequencing error, a reliance on cross-sectional sampling, and/or the lack of formal tests of selection for individual sites. Here, we sequenced IAV populations from 346 serial, daily nasal swabs from 143 individuals collected over three influenza seasons in a household cohort. Viruses were sequenced in duplicate, and intrahost single nucleotide variants (iSNVs) were identified at a 0.5% frequency threshold. Within-host populations exhibited low diversity, with >75% mutations present at <2% frequency. Children (0-5 years) had marginally higher within-host evolutionary rates than adolescents (6-18 years) and adults (>18 years, 4.4 × 10^-6 vs. 9.42 × 10^-7 and 3.45 × 10^-6, P < .001). Forty-five iSNVs had evidence of parallel evolution but were not over-represented in HA and NA. Several increased from minority to consensus level, with strong linkage among iSNVs across segments. A Wright-Fisher approximate Bayesian computational model identified positive selection at 23/256 loci (9%) in A(H3N2) specimens and 19/176 loci (11%) in A(H1N1)pdm09 specimens, and these were infrequently found in circulation. Overall, we found that within-host IAV populations were subject to genetic drift and purifying selection, with only subtle differences across seasons, subtypes, and age strata. Positive selection was rare and inconsistently detected.