ICTV Virus Taxonomy Profiles

The family Clavaviridae includes viruses that replicate in hyperthermophilic archaea from the genus Aeropyrum . The non-enveloped rigid virions are rod-shaped, with dimensions of about 143×16 nm, and have terminal cap structures, one of which is pointed and carries short fibres, while the other is rounded. The virion displays helical symmetry and is constructed from a single major α-helical protein, which is heavily glycosylated, and several minor capsid proteins. The 5278 bp, circular, double-stranded DNA genome of Aeropyrum pernix bacilliform virus 1 is packed inside the virion as a left-handed superhelix. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Clavaviridae, which is available at www.ictv.global/report/clavaviridae.

Megabirnaviridae is a family of non-enveloped spherical viruses with dsRNA genomes of two linear segments, each of 7.2–8.9 kbp, comprising 16.1 kbp in total. The genus Megabirnavirus includes the species Rosellinia necatrix megabirnavirus 1, the exemplar isolate of which infects the white root rot fungus (Rosellinia necatrix) to which it confers hypovirulence. Megabirnaviruses are characterized by their bisegmented genome with large 5′-untranslated regions (1.6 kb) upstream of both 5′-proximal coding strand ORFs, and large protrusions on the particle surface. This is a summary of the ICTV Report on the family Megabirnaviridae, which is available at ictv.global/report/megabirnaviridae.

This Profile is dedicated to the memory of our valued colleague Professor Said A. Ghabrial.

The family Artoviridae was created in 2018 for the established monospecific genus Peropuvirus and six new species of invertebrate viruses that had all been discovered by high-throughput sequencing. Artoviruses have negative-sense RNA genomes of about 12 kb and produce enveloped, spherical particles that are 100–130 nm in diameter. Hosts include parasitoid wasps, barnacles, pillworms, woodlice, copepods and odonates. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Artoviridae, which is available at www.ictv.global/report/artoviridae.

The family Endornaviridae includes viruses with linear, single-stranded, positive-sense RNA genomes that range from 9.7 to 17.6 kb and have been reported infecting plants, fungi and oomycetes. The family consists of two genera, Alphaendornavirus and Betaendornavirus, into which viruses are classified based on their genome size, host and presence of unique domains. Alphaendornavirus includes species whose members infect plants, fungi and oomycetes, while the genus Betaendornavirus includes species whose members infect ascomycete fungi. This is a summary of the ICTV Report on the family Endornaviridae, which is available at www.ictv.global/report/endornaviridae.

Members of the family Filoviridae produce variously shaped, often filamentous, enveloped virions containing linear non-segmented, negative-sense RNA genomes of 15–19 kb. Several filoviruses (e.g., Ebola virus) are pathogenic for humans and are highly virulent. Several filoviruses infect bats (e.g., Marburg virus), whereas the hosts of most other filoviruses are unknown. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on Filoviridae, which is available at www.ictv.global/report/filoviridae.

Polycipiviridae is a family of picorna-like viruses with non-segmented, linear, positive-sense RNA genomes of approximately 10–12 kb. Unusually for viruses within the order Picornavirales, their genomes are polycistronic, with four (or more) consecutive 5′-proximal open reading frames (ORFs) encoding structural (and possibly other) proteins and a long 3′ ORF encoding the replication polyprotein. Members of species within the family have all been detected in ants or via arthropod transcriptomic datasets. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the Polycipiviridae, which is available at www.ictv.global/report/polycipiviridae.

Tristromaviridae is a family of viruses with linear, double-stranded DNA genomes of 16–18 kbp. The flexible, filamentous virions (400±20 nm×30±3 nm) consist of an envelope and an inner core constructed from two structural units: a rod-shaped helical nucleocapsid and a nucleocapsid-encompassing matrix protein layer. Tristromaviruses are lytic and infect hyperthermophilic archaea of the order Thermoproteales . This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the Tristromaviridae, which is available at www.ictv.global/report/tristromaviridae.

The family Nodaviridae includes two genera, Alphanodavirus and Betanodavirus. The family name derives from the Japanese village of Nodamura where Nodamura virus was first isolated from Culex tritaeniorhynchus mosquitoes. Virions are non-enveloped and spherical in shape with icosahedral symmetry (T=3) and diameters ranging from 25 to 33 nm. The genome consists of two molecules of single-stranded positive-sense RNA: RNA1 and RNA2. The virion capsid consists of 180 protein subunits arranged on a T=3 surface lattice. Alphanodaviruses infect insects, whereas betanodaviruses are pathogens of fish. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Nodaviridae, which is available at www.ictv.global/report/nodaviridae.

Hepatitis delta virus, the only member of the only species in the genus Deltavirus, is a unique human pathogen. Its ~1.7 kb circular negative-sense RNA genome encodes a protein, hepatitis delta antigen, which occurs in two forms, small and large, both with unique functions. Hepatitis delta virus uses host RNA polymerase II to replicate via double rolling circle RNA synthesis. Newly synthesized linear RNAs are circularized after autocatalytic cleavage and ligation. Hepatitis delta virus requires the envelope of the helper virus, hepatitis B virus (family Hepadnaviridae), to produce infectious particles. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of Deltavirus which is available at www.ictv.global/report/deltavirus.

Members of the family Fimoviridae, order Bunyavirales are plant viruses with segmented, linear, single-stranded, negative-sense RNA genomes. They are distantly related to orthotospoviruses and orthobunyaviruses of the families Tospoviridae and Peribunyaviridae, respectively. The family Fimoviridae includes the genus Emaravirus, which comprises several species with European mountain ash ringspot-associated emaravirus as the type species. Fimoviruses are transmitted to plants by eriophyid mite vectors and induce similar characteristic cytopathologies in their host plants, including the presence of double membrane-bound bodies in the cytoplasm of the virus-infected cells. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Fimoviridae, which is available at www.ictv.global/report/fimoviridae.