Biology subjects

Holmes, E. C.

Publications and source records attributed to Holmes, E. C..

At least 109 records · Page 6Linked to original sources

bioRxiv2020

Host evolutionary history and ecology shape virome composition in fishes

Revealing the determinants of virome composition is central to placing disease emergence in a broader evolutionary context. Fish are the most species-rich group of vertebrates and so provide an ideal model system to study the factors that shape virome compositions and their evolution. We characterised the viromes of 19 wild-caught species of marine fish using total RNA sequencing (meta-transcriptomics) combined with analyses of sequence and protein structural homology to identify divergent viruses that often evade characterisation. From this, we identified 25 new vertebrate-associated viruses and a further 22 viruses likely associated with fish diet or their microbiomes. The vertebrate-associated viruses identified here included the first fish virus in the Matonaviridae (single-strand, negative-sense RNA virus). Other viruses fell within the Astroviridae, Picornaviridae, Arenaviridae, Reoviridae, Hepadnaviridae, Paramyxoviridae, Rhabdoviridae, Hantaviridae, Filoviridae and Flaviviridae and were sometimes phylogenetically distinct from known fish viruses. We also show how key metrics of virome composition - viral richness, abundance and diversity - can be analysed along with host ecological and biological factors as a means to understand virus ecology. Accordingly, these data suggest that that the vertebrate-associated viromes of the fish sampled here are predominantly shaped by the phylogenetic history (i.e. taxonomic order) of their hosts, along with several biological factors including water temperature, habitat depth, community diversity and swimming behaviour. No such correlations were found for viruses associated with porifera, molluscs, arthropods, fungi and algae, that are unlikely to replicate in fish hosts. Overall, these data indicate that fish harbour particularly large and complex viromes and the vast majority of fish viromes are undescribed.

microbiology↗

bioRxiv2020

Circumpolar diversification of the Ixodes uriae tick virome

Ticks (order: Ixodida) are a highly diverse and ecologically important group of ectoparasitic blood-feeding organisms. One such species, the seabird tick (Ixodes uriae), is widely distributed around the circumpolar regions of the northern and southern hemispheres. It has been suggested that Ix. uriae spread from the southern to the northern circumpolar region millions of years ago and has remained isolated in these regions ever since. Such a profound biographic subdivision provides a unique opportunity to determine whether viruses associated with ticks exhibit the same evolutionary patterns as their hosts. To test this, we collected Ix. uriae specimens near a Gentoo penguin (Pygoscelis papua) colony at Neko harbour, Antarctica, and from migratory birds - the Razorbill (Alca torda) and the Common murre (Uria aalge) - on Bonden island, northern Sweden. Through meta-transcriptomic next- generation sequencing we identified 16 RNA viruses, seven of which were novel. Notably, we detected the same species, Ronne virus, and two closely related species, Bonden virus and Piguzov virus, in both hemispheres indicating that there have been at least two cross- circumpolar dispersal events. Similarly, we identified viruses discovered previously in other locations several decades ago, including Gadgets Gully virus, Taggert virus and Okhotskiy virus. By identifying the same or closely related viruses in geographically disjunct sampling locations we therefore provide evidence for virus dispersal within and between the circumpolar regions. In marked contrast, our phylogenetic analysis revealed no movement of the Ix. uriae hosts between the same locations. Combined, these data suggest that migratory birds are responsible for the movement of viruses at both the local and global scales. Author summary/ImportanceAs host populations diverge, so may those microorganisms, including viruses, that are dependent on those hosts. To examine this key issue in host-microbial evolution we compared the co-phylogenies of the seabird tick, Ixodes uriae, and their RNA viruses sampled from the far northern and southern hemispheres. Despite the huge geographic distance between them, phylogeographic analysis reveals that the same viruses were found both within and between the northern and southern circumpolar regions, most likely reflecting transfer by virus-infected migratory birds. In contrast, genomic data suggested that the Ix. uriae populations were phylogenetically distinct between the northern and southern hemispheres. This work emphasises the importance of migratory birds and ticks as vectors and sources of virus dispersal and introduction at both the local and global scales.

microbiology↗

bioRxiv2020

REVEALING COVID-19 TRANSMISSION BY SARS-CoV-2 GENOME SEQUENCING AND AGENT BASED MODELLING

Community transmission of the new coronavirus SARS-CoV-2 is a major public health concern that remains difficult to assess. We present a genomic survey of SARS-CoV-2 from a during the first 10 weeks of COVID-19 activity in New South Wales, Australia. Transmission events were monitored prospectively during the critical period of implementation of national control measures. SARS-CoV-2 genomes were sequenced from 209 patients diagnosed with COVID-19 infection between January and March 2020. Only a quarter of cases appeared to be locally acquired and genomic-based estimates of local transmission rates were concordant with predictions from a computational agent-based model. This convergent assessment indicates that genome sequencing provides key information to inform public health action and has improved our understanding of the COVID-19 evolution from outbreak to epidemic.

microbiology↗

bioRxiv2020

A dynamic nomenclature proposal for SARS-CoV-2 to assist genomic epidemiology

The ongoing pandemic spread of a novel human coronavirus, SARS-COV-2, associated with severe pneumonia disease (COVID-19), has resulted in the generation of thousands of virus genome sequences. The rate of genome generation is unprecedented, yet there is currently no coherent nor accepted scheme for naming the expanding phylogenetic diversity of SARS-CoV-2. We present a rational and dynamic virus nomenclature that uses a phylogenetic framework to identify those lineages that contribute most to active spread. Our system is made tractable by constraining the number and depth of hierarchical lineage labels and by flagging and declassifying virus lineages that become unobserved and hence are likely inactive. By focusing on active virus lineages and those spreading to new locations this nomenclature will assist in tracking and understanding the patterns and determinants of the global spread of SARS-CoV-2.

microbiology↗

bioRxiv2020

An emergent clade of SARS-CoV-2 linked to returned travellers from Iran

The SARS-CoV-2 epidemic has rapidly spread outside China with major outbreaks occurring in Italy, South Korea and Iran. Phylogenetic analyses of whole genome sequencing data identified a distinct SARS-CoV-2 clade linked to travellers returning from Iran to Australia and New Zealand. This study highlights potential viral diversity driving the epidemic in Iran, and underscores the power of rapid genome sequencing and public data sharing to improve the detection and management of emerging infectious diseases.

microbiology↗

bioRxiv2020

The short-term effect of residential home energy retrofits on indoor air quality and microbial exposure: a case-control study

Weatherization of residential homes is a popular retrofit procedure to improve the energy efficiency of older homes by reducing building leakage. It is a vital tool in the fight against climate change. Several studies have evaluated the effect of weatherization on indoor pollutants such as formaldehyde and radon, but few studies have evaluated the effect of weatherization on indoor particulates and microbial exposure. In this study, we compared the effect of change in building leakage on indoor pollutants and bacterial communities in weatherized compared to non-weatherized single-family residential homes in New York State. Nine weatherized and eleven non-weatherized single-family homes in Tompkins County, New York were sampled twice: before and after the weatherization procedures for case homes, and at least 3 months apart for control homes that were not weatherized. We found a significant increase in both indoor-outdoor temperature ratio and living-area- and basement-radon levels of weatherized homes compared to control homes. The indoor-outdoor relative humidity ratio significantly decreased in weatherized compared to control homes. The indoor microbiome also became less similar to the outdoor community after weatherization. Compared to the changes in ventilation rate, temperature, relative humidity, and occupancy, the change in season was a more predictive measure of indoor bacterial concentration. Ventilation rate reduction from weatherization procedures led to an increase in indoor radon levels, as well as a warmer and less humid indoor environment. However, it did not affect indoor particulate mass concentration or indoor airborne bacteria load, and did only marginally affect the microbiome composition of residential homes. Finally, we found that changes in airborne bacterial load are more sensitive to shifts in season, whereas radon levels are more sensitive to ventilation rate.

microbiology↗

bioRxiv2020

Meta-transcriptomic analysis of virus diversity in urban wild birds with paretic disease

Wild birds are major natural reservoirs and potential dispersers of a variety of infectious diseases. As such, it is important to determine the diversity of viruses they carry and use this information to help understand the potential risks of spill-over to humans, domestic animals, and other wildlife. We investigated the potential viral causes of paresis in long-standing, but undiagnosed disease syndromes in wild Australian birds. RNA from diseased birds was extracted and pooled based on tissue type, host species and clinical manifestation for metagenomic sequencing. Using a bulk and unbiased meta-transcriptomic approach, combined with careful clinical investigation and histopathology, we identified a number of novel viruses from the families Astroviridae, Picornaviridae, Polyomaviridae, Paramyxoviridae, Parvoviridae, Flaviviridae, and Circoviridae in common urban wild birds including Australian magpies, magpie lark, pied currawongs, Australian ravens, and rainbow lorikeets. In each case the presence of the virus was confirmed by RT-PCR. These data revealed a number of candidate viral pathogens that may contribute to coronary, skeletal muscle, vascular and neuropathology in birds of the Corvidae and Artamidae families, and neuropathology in members of the Psittaculidae. The existence of such a diverse virome in urban avian species highlights the importance and challenges in elucidating the etiology and ecology of wildlife pathogens in urban environments. This information will be increasingly important for managing disease risks and conducting surveillance for potential viral threats to wildlife, livestock and human health. More broadly, our work shows how meta-transcriptomics brings a new utility to pathogen discovery in wildlife diseases. ImportanceWildlife naturally harbor a diverse array of infectious microorganisms and can be a source of novel diseases in domestic animals and human populations. Using unbiased RNA sequencing we identified highly diverse viruses in native birds in Australian urban environments presenting with paresis. This investigation included the clinical investigation and description of poorly understood recurring syndromes of unknown etiology: clenched claw syndrome, and black and white bird disease. As well as identifying a range of potentially disease-causing viral pathogens, this study describes methods that can effectively and efficiently characterize emergent disease syndromes in free ranging wildlife, and promotes further surveillance for specific potential pathogens of potential conservation and zoonotic concern.

microbiology↗

bioRxiv2020

A novel bat coronavirus reveals natural insertions at the S1/S2 cleavage site of the Spike protein and a possible recombinant origin of HCoV-19

The unprecedented epidemic of pneumonia caused by a novel coronavirus, HCoV-19, in China and beyond has caused public health concern at a global scale. Although bats are regarded as the most likely natural hosts for HCoV-191,2, the origins of the virus remain unclear. Here, we report a novel bat-derived coronavirus, denoted RmYN02, identified from a metagenomics analysis of samples from 227 bats collected from Yunnan Province in China between May and October, 2019. RmYN02 shared 93.3% nucleotide identity with HCoV-19 at the scale of the complete virus genome and 97.2% identity in the 1ab gene in which it was the closest relative of HCoV-19. In contrast, RmYN02 showed low sequence identity (61.3%) to HCoV-19 in the receptor binding domain (RBD) and might not bind to angiotensin-converting enzyme 2 (ACE2). Critically, however, and in a similar manner to HCoV-19, RmYN02 was characterized by the insertion of multiple amino acids at the junction site of the S1 and S2 subunits of the Spike (S) protein. This provides strong evidence that such insertion events can occur in nature. Together, these data suggest that HCoV-19 originated from multiple naturally occurring recombination events among those viruses present in bats and other wildlife species.

microbiology↗

bioRxiv2020

Influenza A viruses serially passaged in different MDCK cell lines exhibit limited sequence variation across their genomes, with the exception of the hemagglutinin gene

New methods for deep sequence analysis provide an opportunity to follow the emergence and dynamics of virus mutations in real time. Although viruses are commonly grown in cell culture for research and for vaccine development, the cells used to grow the virus are often not derived from the same tissue or even the same host that the virus naturally replicates in. The selective pressures of culturing virus in vitro are still only partially understood. MDCK cells are the standard cell for growing influenza viruses yet are derived from the epithelium of the canine kidney and are also heterogenous. We passaged human H3N2, H1N1 pandemic, and canine H3N2 influenza A viruses (IAV) in different lineages of MDCK cells, as well as lines engineered to express variant Sia receptors, including 2,3- and 2,6-linkages or N-glycolylneuraminic acid (Neu5Gc) or N-acetylneuraminic acid (Neu5Ac) forms. MDCK-Type II cells had lower infection efficiency and virus production, and infection appeared more dependent on protease activation of the virus. When viruses were passaged in the different cells, they exhibited only small numbers of consensus-level mutations, and most were within the HA gene. Both human IAVs showed selection for single nucleotide minority variants in the HA stem across cell types, as well as low frequency variants in the HA receptor binding site of virus passaged in cells expressing Neu5Gc. Canine H3N2 also showed minority variants near the receptor-binding site in cells expressing Neu5Gc and also in those expressing 2,6-linkages. IMPORTANCEThe genetic variation and adaptability of viruses are fundamental properties that allow their evolutionary success in the face of differing host environments and immune responses. The growth of viruses in cell culture is widely used for their study and for preparing vaccines. However, the selection pressures that cell passaging imposes on viruses are often poorly understood. We used deep sequence analysis to define, in detail, how three different influenza A viruses respond to passaging in different lineages of canine MDCK cells that are commonly used for their growth, as well as in variant cells engineered to express different forms of their cell surface receptor, sialic acid. This analysis revealed that most mutations occur in the HA gene and few sequence changes in the virus population reached high proportions. This is relevant for understanding the selective pressures of virus growth in cell culture and how it shapes evolutionary patterns.

microbiology↗

bioRxiv2020

Identification of 2019-nCoV related coronaviruses in Malayan pangolins in southern China

The ongoing outbreak of viral pneumonia in China and beyond is associated with a novel coronavirus, provisionally termed 2019-nCoV. This outbreak has been tentatively associated with a seafood market in Wuhan, China, where the sale of wild animals may be the source of zoonotic infection. Although bats are likely reservoir hosts for 2019-nCoV, the identity of any intermediate host facilitating transfer to humans is unknown. Here, we report the identification of 2019-nCoV related coronaviruses in pangolins (Manis javanica) seized in anti-smuggling operations in southern China. Metagenomic sequencing identified pangolin associated CoVs that belong to two sub-lineages of 2019-nCoV related coronaviruses, including one very closely related to 2019-nCoV in the receptor-binding domain. The discovery of multiple lineages of pangolin coronavirus and their similarity to 2019-nCoV suggests that pangolins should be considered as possible intermediate hosts for this novel human virus and should be removed from wet markets to prevent zoonotic transmission.

microbiology↗

bioRxiv2020

Complete genome characterisation of a novel coronavirus associated with severe human respiratory disease in Wuhan, China

Emerging and re-emerging infectious diseases, such as SARS, MERS, Zika and highly pathogenic influenza present a major threat to public health1-3. Despite intense research effort, how, when and where novel diseases appear are still the source of considerable uncertainly. A severe respiratory disease was recently reported in the city of Wuhan, Hubei province, China. At the time of writing, at least 62 suspected cases have been reported since the first patient was hospitalized on December 12nd 2019. Epidemiological investigation by the local Center for Disease Control and Prevention (CDC) suggested that the outbreak was associated with a sea food market in Wuhan. We studied seven patients who were workers at the market, and collected bronchoalveolar lavage fluid (BALF) from one patient who exhibited a severe respiratory syndrome including fever, dizziness and cough, and who was admitted to Wuhan Central Hospital on December 26th 2019. Next generation metagenomic RNA sequencing4 identified a novel RNA virus from the family Coronaviridae designed WH-Human-1 coronavirus (WHCV). Phylogenetic analysis of the complete viral genome (29,903 nucleotides) revealed that WHCV was most closely related (89.1% nucleotide similarity similarity) to a group of Severe Acute Respiratory Syndrome (SARS)-like coronaviruses (genus Betacoronavirus, subgenus Sarbecovirus) previously sampled from bats in China and that have a history of genomic recombination. This outbreak highlights the ongoing capacity of viral spill-over from animals to cause severe disease in humans.

pathology↗

bioRxiv2019

Sustained virome diversity in Antarctic penguins and their ticks: geographical connectedness and no evidence for low pathogen pressure

Despite its isolation and extreme climate, Antarctica is home to diverse fauna and associated microorganisms. It has been proposed that the most iconic Antarctic animal, the penguin, experiences low pathogen pressure, accounting for their disease susceptibility in foreign environments. However, there is a limited understanding of virome diversity in Antarctic species, the extent of in situ virus evolution, or how it relates to that in other geographic regions. To test the idea that penguins have limited microbial diversity we determined the viromes of three species of penguins and their ticks sampled on the Antarctic peninsula. Using total RNA-Sequencing we identified 107 viral species, comprising likely penguin associated viruses (n = 13), penguin diet and microbiome associated viruses (n = 82) and tick viruses (n = 8), two of which may have the potential to infect penguins. Notably, the level of virome diversity revealed in penguins is comparable to that seen in Australian waterbirds, including many of the same viral families. These data therefore reject the theory that penguins are subject to lower pathogen pressure. The repeated detection of specific viruses in Antarctic penguins also suggests that rather than being simply spill-over hosts, these animals may act as key virus reservoirs.

microbiology↗

bioRxiv2019

Limited overlap in RNA virome composition among rabbits and their ectoparasites reveals barriers to virus transmission

Ectoparasites play an important role in virus transmission among vertebrates. However, little is known about the extent and composition of viruses that pass between invertebrates and vertebrates. In Australia, flies and fleas support the mechanical transmission of viral biological controls against wild rabbits - rabbit haemorrhagic disease virus (RHDV) and myxoma virus. We compared virome structure and composition in rabbits and these associated ectoparasites, sequencing total RNA from multiple tissues and gut contents of wild rabbits, fleas collected from these rabbits, and flies trapped sympatrically. Meta-transcriptomic analyses identified 50 novel viruses from multiple RNA virus families. Rabbits and their ectoparasites were characterised by markedly different viromes: although viral contigs from six virus families/groups were found in both rabbits and ectoparasites, none were vertebrate-associated. A novel calicivirus and picornavirus detected in rabbit caecal content were vertebrate-specific: the newly detected calicivirus was distinct from known rabbit caliciviruses, while the novel picornavirus clustered with the Sapeloviruses. Several Picobirnaviridae were also identified, falling in diverse phylogenetic positions suggestive of an association with co-infecting bacteria. The remaining viruses found in rabbits, and all those from ectoparasites, were likely associated with invertebrates, plants and co-infecting endosymbionts. While no full genomes of vertebrate-associated viruses were detected in ectoparasites, suggestive of major barriers to biological transmission with active replication, small numbers of reads from rabbit astrovirus, RHDV and other lagoviruses were present in flies. This supports the role of flies in the mechanical transmission of RHDV and implies that they may assist the spread of astroviruses.

microbiology↗

bioRxiv2019

Metagenomic discovery and co-infection of diverse wobbly possum disease viruses and novel hepaciviruses in Australian brushtail possums

BackgroundAustralian brushtail possums (Trichosurus vulpecula) are an introduced pest species in New Zealand, but native to Australia where they are protected for biodiversity conservation. Wobbly possum disease (WPD) is a fatal neurological disease of Australian brushtail possums described in New Zealand populations that has been associated with infection by the arterivirus (Arteriviridae) wobbly possum disease virus (WPDV-NZ). Clinically, WPD-infected possums present with chronic meningoencephalitis, choroiditis and multifocal neurological symptoms including ataxia, incoordination, and abnormal gait. MethodsWe conducted a retrospective investigation to characterise WPD in native Australian brushtail possums, and used a bulk meta-transcriptomic approach (i.e. total RNA-sequencing) to investigate its potential viral aetiology. PCR assays were developed for case diagnosis and full genome recovery in the face of extensive genetic variation. ResultsWe identified a distinct lineage of arteriviruses from archival tissues of WPD-infected possums in Australia, termed wobbly possum disease virus AU1 and AU2. Phylogenetically, WPDV-AU1 and WPDV-AU2 shared only [~]70% nucleotide similarity to each other and the WPDV-NZ strain, suggestive of a relatively ancient divergence. Notably, we identified a novel and divergent hepacivirus (Flaviviridae) - the first in a marsupial - in both WPD-infected and uninfected possums, indicative of virus co-infection. ConclusionsWe have identified a distinctive marsupial-specific lineage of arteriviruses in mainland Australia that is genetically distinct from that in New Zealand, in some cases co-infecting animals with a novel hepacivirus. Our study provides new insight into the hidden genetic diversity of arteriviruses, the capacity for virus co-infection, and highlights the utility of meta-transcriptomics for disease investigation and surveillance in a One Health context.

pathology↗

bioRxiv2019

Comparative analysis reveals adaptive evolution of bat IFITMs and a novel antiviral determinant

Host interferon-induced transmembrane proteins (IFITMs) are broad-spectrum antiviral restriction factors. Of these, IFITM3 potently inhibits viruses that enter cells through acidic endosomes, many of which are zoonotic and emerging viruses with bats (order Chiroptera) as natural hosts. We previously demonstrated that microbat IFITM3 is antiviral. Here we show that bat IFITMs are characterized by strong adaptive evolution and identify a highly variable and functionally important site - codon 70 - within the conserved CD225 domain of IFITMs. Mutation of this residue in microbat IFITM3 impairs restriction of four different virus families that enter cells via endosomes. This mutant shows altered subcellular localization and reduced S-palmitoylation, a phenotype copied by mutation of conserved cysteine residues in microbat IFITM3. Furthermore, we show that microbat IFITM3 is S-palmitoylated on cysteine residues C71, C72 and C105, mutation of each cysteine residue individually impairs virus restriction, and a triple C71-C72-C105 mutant loses all restriction, concomitant with subcellular re-localization of microbat IFITM3 to Golgi-associated sites. Thus, we propose that S-palmitoylation is critical for Chiropteran IFITM3 function and identify a key molecular determinant of IFITM3 S-palmitoylation.

immunology↗

bioRxiv2019

Meta-transcriptomic comparison of the RNA viromes of the mosquito vectors Culex pipiens and Culex torrentium in northern Europe

There is mounting evidence that mosquitoes harbour an extensive diversity of insect-specific RNA viruses in addition to those important to human and animal health. However, because most studies of the mosquito virome have been conducted at lower latitudes there is a major knowledge gap on the genetic diversity, evolutionary history, and spread of RNA viruses sampled from mosquitoes in northern latitudes. Here, we determined and compared the RNA virome of two common northern Culex mosquito species, Cx. pipiens and Cx. torrentium, known vectors of West Nile virus and Sindbis virus, respectively, collected in south-central Sweden. Following bulk RNA-sequencing (meta-transcriptomics) of 12 libraries, comprising 120 specimens of Cx. pipiens and 150 specimens of Cx. torrentium, we identified 40 viruses (representing 14 virus families) of which 28 were novel based on phylogenetic analysis of the RNA-dependent RNA polymerase (RdRp) protein. Hence, we found similar levels of virome diversity as in mosquitoes sampled from the more biodiverse lower latitudes. Four libraries, all from Cx. torrentium, had a significantly higher abundance of viral reads, spanning [~]7- 36% of the total amount of reads. Many of these viruses were also related to those sampled on other continents, indicative of widespread global movement and/or long host-virus co-evolution. Importantly, although the two mosquito species investigated have overlapping geographical distributions and share many viruses, approximately one quarter of the viruses were only found at a specific location, such that geography must play an important role in shaping the diversity of RNA viruses in Culex mosquitoes.\n\nImportanceRNA viruses are found in all domains of life and all global habitats. However, the factors that determine virome composition and structure within and between organisms are largely unknown. Herein, we characterised RNA virus diversity in two common mosquito vector species, Culex pipiens and Culex torrentium, sampled from northern Europe. Our analysis revealed extensive viral diversity, including 28 novel viruses, and was comparable to the levels of diversity found in other temperate and tropical regions globally. Importantly, as well as harbouring RNA viruses that are closely related to other mosquito-derived viruses sampled in diverse global locations, we also described a number of viruses that are unique to specific sampling locations in Sweden. Hence, these data showed that geographical factors can play an important role in shaping virome structure even at local scales.

evolutionary biology↗

bioRxiv2019

Limited intra-host diversity and background evolution accompany 40 years of canine parvovirus host adaptation and spread

Canine parvovirus (CPV) is a highly successful pathogen that has sustained pandemic circulation in dogs for more than 40 years. Here, integrating full-genome and deep sequencing analyses, structural information, and in vitro experimentation, we describe the macro- and micro-scale features that have accompanied CPVs evolutionary success. Despite 40 years of viral evolution, all CPV variants are >[~]99% identical in nucleotide sequence, with only a limited number (<40) of mutations becoming fixed or widespread during this time. Notably, most changes in the major capsid protein (VP2) are nonsynonymous and fall within, or adjacent to, the overlapping receptor footprint or antigenic regions, suggesting competitive selective pressures have played a key role in CPV evolution and likely constrained its evolutionary trajectory. Moreover, among the limited number of variable sites, CPV genomes exhibit complex patterns of variation that likely include parallel evolution, reversion, and recombination, making phylogenetic inference difficult. Additionally, deep sequencing of viral DNA in original clinical samples collected from dogs and other host species sampled between 1978 and 2018 revealed few sub-consensus single nucleotide variants (SNVs) above [~]0.5%, and experimental passages demonstrate that substantial pre-existing genetic variation is not necessarily required for rapid host receptor driven adaptation. Together, these findings suggest that although CPV is capable of rapid host adaptation, relatively low mutation rate, pleiotropy, and/or a lack of selective challenges since its initial emergence have reduced the long-term genetic diversity accumulation and evolutionary rate. Hence, continuously high levels of inter- and intra-host diversity are not intrinsic to highly adaptable viruses.\n\nIMPORTANCERapid mutation rates and correspondingly high levels of standing intra-host diversity and accumulated inter-host diversity over epidemic scales are often cited as key features of viruses with the capacity for emergence and sustained transmission in a new host species. However, most of this information comes from studies of RNA viruses, with relatively little being known about that evolutionary processes that occur for viruses with DNA genomes. Here we provide a unique model of virus evolution, integrating both long-term global-scale and short-term intra-host evolutionary processes of a virus in a new host animal. Our analysis reveals that successful host jumping and sustained onward transmission does not necessarily depend on a high level of intra-host diversity or result in the continued accumulation of high levels of long-term evolution change. These findings indicate that all aspects of a viruss biology and ecology are relevant when considering their adaptability.

evolutionary biology↗

bioRxiv2019

Influenza Viruses in Mice: Deep Sequencing Analysis of Serial Passage and Effects of Sialic Acid Structural Variation

Influenza A viruses have regularly jumped to new hosts to cause epidemics or pandemics, an evolutionary process that involves variation in the viral traits necessary to overcome host barriers and facilitate transmission. Mice are not a natural host for influenza virus, but are frequently used as models in studies of pathogenesis, often after multiple passages to achieve higher viral titers that result in clinical disease such as weight loss or death. Here we examine the processes of influenza A virus infection and evolution in mice by comparing deep sequence variation of a human H1N1 pandemic virus, a seasonal H3N2 virus, and a H3N2 canine influenza virus during experimental passage. We also compared replication and sequence variation in wild-type mice expressing N-glycolylneuraminic acid (Neu5Gc) with that seen in mice expressing only N-acetylneuraminic acid (Neu5Ac). Viruses derived from plasmids were propagated in MDCK cells and then passaged in mice up to four times. Full genome deep sequencing of the plasmids, cultured viruses, and viruses from mice at various passages revealed only small numbers of mutational changes. The H3N2 canine influenza virus showed increases in frequency of sporadic mutations in the PB2, PA, and NA segments. The H1N1 pandemic virus grew well in mice, and while it exhibited the maintenance of some minority mutations, there was no clear adaptive evolution. The H3N2 seasonal virus did not establish in the mice. Finally, there were no clear sequence differences associated with the presence or absence of Neu5Gc.\n\nSIGNIFICANCEMice are commonly used as a model to study the growth and virulence of influenza A viruses in mammals, but are not a natural host and have distinct sialic acid receptor profiles compared to humans. Using experimental infections with different subtypes of influenza A virus derived from different hosts we found that evolution of influenza A virus in mice did not necessarily proceed through the linear accumulation of host-adaptive mutations, that there was variation in the patterns of mutations detected in each repetition, and the mutation dynamics depended on the virus examined. In addition, variation in the viral receptor, sialic acid, did not effect influenza evolution in this model. Overall this shows that mice provide a useful animal model for influenza, but that host passage evolution will vary depending on the virus being tested.

microbiology↗