Yīmíng Bào

Large-scale sequencing of human influenza reveals the dynamic nature of viral genome evolution

Influenza viruses are remarkably adept at surviving in the human population over a long timescale. The human influenza A virus continues to thrive even among populations with widespread access to vaccines, and continues to be a major cause of morbidity and mortality. The virus mutates from year to year, making the existing vaccines ineffective on a regular basis, and requiring that new strains be chosen for a new vaccine. Less-frequent major changes, known as antigenic shift, create new strains against which the human population has little protective immunity, thereby causing worldwide pandemics. The most recent pandemics include the 1918 ‘Spanish’ flu, one of the most deadly outbreaks in recorded history, which killed 30–50 million people worldwide, the 1957 ‘Asian’ flu, and the 1968 ‘Hong Kong’ flu. Motivated by the need for a better understanding of influenza evolution, we have developed flexible protocols that make it possible to apply large-scale sequencing techniques to the highly variable influenza genome. Here we report the results of sequencing 209 complete genomes of the human influenza A virus, encompassing a total of 2,821,103 nucleotides. In addition to increasing markedly the number of publicly available, complete influenza virus genomes, we have discovered several anomalies in these first 209 genomes that demonstrate the dynamic nature of influenza transmission and evolution. This new, large-scale sequencing effort promises to provide a more comprehensive picture of the evolution of influenza viruses and of their pattern of transmission through human and animal populations. All data from this project are being deposited, without delay, in public archives.

Taxonomy of the order Mononegavirales: update 2016

In 2016, the order Mononegavirales was emended through the addition of two new families (Mymonaviridae and Sunviridae), the elevation of the paramyxoviral subfamily Pneumovirinae to family status (Pneumoviridae), the addition of five free-floating genera (Anphevirus, Arlivirus, Chengtivirus, Crustavirus, and Wastrivirus), and several other changes at the genus and species levels. This article presents the updated taxonomy of the order Mononegavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV).

Past, present, and future of arenavirus taxonomy

Until recently, members of the monogeneric family Arenaviridae (arenaviruses) have been known to infect only muroid rodents and, in one case, possibly phyllostomid bats. The paradigm of arenaviruses exclusively infecting small mammals shifted dramatically when several groups independently published the detection and isolation of a divergent group of arenaviruses in captive alethinophidian snakes. Preliminary phylogenetic analyses suggest that these reptilian arenaviruses constitute a sister clade to mammalian arenaviruses. Here, the members of the International Committee on Taxonomy of Viruses (ICTV) Arenaviridae Study Group, together with other experts, outline the taxonomic reorganization of the family Arenaviridae to accommodate reptilian arenaviruses and other recently discovered mammalian arenaviruses and to improve compliance with the Rules of the International Code of Virus Classification and Nomenclature (ICVCN). PAirwise Sequence Comparison (PASC) of arenavirus genomes and NP amino acid pairwise distances support the modification of the present classification. As a result, the current genus Arenavirus is replaced by two genera, Mammarenavirus and Reptarenavirus, which are established to accommodate mammalian and reptilian arenaviruses, respectively, in the same family. The current species landscape among mammalian arenaviruses is upheld, with two new species added for Lunk and Merino Walk viruses and minor corrections to the spelling of some names. The published snake arenaviruses are distributed among three new separate reptarenavirus species. Finally, a non-Latinized binomial species name scheme is adopted for all arenavirus species. In addition, the current virus abbreviations have been evaluated, and some changes are introduced to unequivocally identify each virus in electronic databases, manuscripts, and oral proceedings.

Nomenclature- and database-compatible names for the two Ebola virus variants that emerged in Guinea and the Democratic Republic of the Congo in 2014.

In 2014, Ebola virus (EBOV) was identified as the etiological agent of a large and still expanding outbreak of Ebola virus disease (EVD) in West Africa and a much more confined EVD outbreak in Middle Africa. Epidemiological and evolutionary analyses confirmed that all cases of both outbreaks are connected to a single introduction each of EBOV into human populations and that both outbreaks are not directly connected. Coding-complete genomic sequence analyses of isolates revealed that the two outbreaks were caused by two novel EBOV variants, and initial clinical observations suggest that neither of them should be considered strains. Here we present consensus decisions on naming for both variants (West Africa: “Makona”, Middle Africa: “Lomela”) and provide database-compatible full, shortened, and abbreviated names that are in line with recently established filovirus sub-species nomenclatures.

Taxonomic reorganization of the family Bornaviridae

Knowledge of bornaviruses has expanded considerably during the last decade. A possible reservoir of mammalian Borna disease virus has been identified, divergent bornaviruses have been detected in birds and reptiles, and endogenous bornavirus-like elements have been discovered in the genomes of vertebrates of several species. Previous sequence comparisons and alignments have indicated that the members of the current family Bornaviridae are phylogenetically diverse and are not adequately classified in the existing bornavirus taxonomy supported by the International Committee on Taxonomy of Viruses (ICTV). We provide an update of these analyses and describe their implications for taxonomy. We propose retaining the family name Bornaviridae and the genus Bornavirus but reorganizing species classification. PAirwise Sequence Comparison (PASC) of bornavirus genomes and Basic Local Alignment Search Tool (BLAST) comparison of genomic and protein sequences, in combination with other already published phylogenetic analyses and known biological characteristics of bornaviruses, indicate that this genus should include at least five species: Mammalian 1 bornavirus (classical Borna disease virus and divergent Borna disease virus isolate No/98), Psittaciform 1 bornavirus (avian/psittacine bornaviruses 1, 2, 3, 4, 7), Passeriform 1 bornavirus (avian/canary bornaviruses C1, C2, C3, LS), Passeriform 2 bornavirus (estrildid finch bornavirus EF), and Waterbird 1 bornavirus (avian bornavirus 062CG). This classification is also in line with biological characteristics of these viruses and their vertebrate hosts. A snake bornavirus, proposed to be named Loveridge’s garter snake virus 1, should be classified as a member of an additional species (Elapid 1 bornavirus), unassigned to a genus, in the family Bornaviridae. Avian bornaviruses 5, 6, MALL, and another “reptile bornavirus” (“Gaboon viper virus”) should stay unclassified until further information becomes available. Finally, we propose new virus names and abbreviations when necessary to achieve clear differentiation and unique identification.

Historical Outbreaks of Simian Hemorrhagic Fever in Captive Macaques Were Caused by Distinct Arteriviruses

ABSTRACT Simian hemorrhagic fever (SHF) is lethal for macaques. Based on clinical presentation and serological diagnosis, all reported SHF outbreaks were thought to be caused by different strains of the same virus, simian hemorrhagic fever virus (SHFV; Arteriviridae). Here we show that the SHF outbreaks in Sukhumi in 1964 and in Alamogordo in 1989 were caused not by SHFV but by two novel divergent arteriviruses. Our results indicate that multiple divergent simian arteriviruses can cause SHF.

Taxonomy of the family Arenaviridae and the order Bunyavirales: update 2018

In 2018, the family Arenaviridae was expanded by inclusion of 1 new genus and 5 novel species. At the same time, the recently established order Bunyavirales was expanded by 3 species. This article presents the updated taxonomy of the family Arenaviridae and the order Bunyavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV) and summarizes additional taxonomic proposals that may affect the order in the near future.

Implementation of objective PASC-derived taxon demarcation criteria for official classification of filoviruses

The mononegaviral family Filoviridae has eight members assigned to three genera and seven species. Until now, genus and species demarcation were based on arbitrarily chosen filovirus genome sequence divergence values (≈50% for genera, ≈30% for species) and arbitrarily chosen phenotypic virus or virion characteristics. Here we report filovirus genome sequence-based taxon demarcation criteria using the publicly accessible PAirwise Sequencing Comparison (PASC) tool of the US National Center for Biotechnology Information (Bethesda, MD, USA). Comparison of all available filovirus genomes in GenBank using PASC revealed optimal genus demarcation at the 55–58% sequence diversity threshold range for genera and at the 23–36% sequence diversity threshold range for species. Because these thresholds do not change the current official filovirus classification, these values are now implemented as filovirus taxon demarcation criteria that may solely be used for filovirus classification in case additional data are absent. A near-complete, coding-complete, or complete filovirus genome sequence will now be required to allow official classification of any novel “filovirus.” Classification of filoviruses into existing taxa or determining the need for novel taxa is now straightforward and could even become automated using a presented algorithm/flowchart rooted in RefSeq (type) sequences.

Preliminary Classification of Novel Hemorrhagic Fever-Causing Viruses Using Sequence-Based PAirwise Sequence Comparison (PASC) Analysis

During the last decade, genome sequence-based classification of viruses has become increasingly prominent. Viruses can be even classified based on coding-complete genome sequence data alone. Nevertheless, classification remains arduous as experts are required to establish phylogenetic trees to depict the evolutionary relationships of such sequences for preliminary taxonomic placement. Pairwise sequence comparison (PASC) of genomes is one of several novel methods for establishing relationships among viruses. This method, provided by the US National Center for Biotechnology Information as an open-access tool, circumvents phylogenetics, and yet PASC results are often in agreement with those of phylogenetic analyses. Computationally inexpensive, PASC can be easily performed by non-taxonomists. Here we describe how to use the PASC tool for the preliminary classification of novel viral hemorrhagic fever-causing viruses.