ICTV Virus Taxonomy Profile: Filoviridae 2024

Abstract Filoviridae is a family of negative-sense RNA viruses with genomes of about 13.1–20.9 kb that infect fish, mammals and reptiles. The filovirid genome is a linear, non-segmented RNA with five canonical open reading frames (ORFs) that encode a nucleoprotein (NP), a polymerase cofactor (VP35), a glycoprotein (GP1,2), a transcriptional activator (VP30) and a large protein (L) containing an RNA-directed RNA polymerase (RdRP) domain. All filovirid genomes encode additional proteins that vary among genera. Several filovirids (e.g., Ebola virus, Marburg virus) are pathogenic for humans and highly virulent. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Filoviridae, which is available at www.ictv.global/report/filoviridae.


Abstract
Filoviridae is a family of negative-sense RNA viruses with genomes of about 13.1-20.9kb that infect fish, mammals and reptiles.The filovirid genome is a linear, non-segmented RNA with five canonical open reading frames (ORFs) that encode a nucleoprotein (NP), a polymerase cofactor (VP35), a glycoprotein (GP 1,2 ), a transcriptional activator (VP30) and a large protein (L) containing an RNA-directed RNA polymerase (RdRP) domain.All filovirid genomes encode additional proteins that vary among genera.Several filovirids (e.g., Ebola virus, Marburg virus) are pathogenic for humans and highly virulent.This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Filoviridae, which is available at www.ictv.global/report/filoviridae.

GENOME
Filovirid genomes (Fig. 2) are about 13.1-20.9kb and lack a 5′-cap or 3′-poly(A) tail.Terminal leader and trailer sequences contain the replication and transcription promoters.Six to ten ORFs are flanked by 3′-and 5′-terminal non-coding regions that contain transcription initiation and termination sites.Five ORFs are shared among all filovirids and encode homologous structural proteins (NP, VP35, GP 1,2 , VP30, L).

REPLICATION
Filovirions attach to cell surface receptors or attachment factors and enter endosomes in which they engage intracellular receptors.pH-dependent fusion with late endosomes releases virion RNP complexes into the cytoplasm.The virus RNP directs both RNA genome replication and gene transcription.Virus proteins are translated from mRNAs that are synthesized by successive, polar transcription from RNP complexes containing genomic RNA.Replication occurs in the cytoplasm through the synthesis of RNP complexes containing antigenomes that are templates for genomic RNA production.Replication and transcription enzymes include L and VP35.VP30 serves as a transcription enhancer and acts at different gene start sites.Whereas orthoebolaviral and cuevaviral VP30 mediates transcription initiation at the NP gene start site, orthomarburgviral VP30 mediates transcription reinitiation at the GP gene start site.VP30's function for other filovirids is less defined.In the case of mammalian filovirids, virion assembly, including acquisition of the lipid envelope containing GP 1,2 , occurs by VP40-mediated budding at the plasma membrane [1][2][3][4].
Funding informationThis work was supported in part through the Laulima Government Solutions, LLC, prime contract with the US National Institute of Allergy and Infectious Diseases under contract no.HHSN272201800013C.J.H.K. performed this work as an employee of Tunnell Government Services, a subcontractor of Laulima Government Solutions, LLC, under contract no.HHSN272201800013C.This work was funded under Agreement No. HSHQDC-15-C-00064 awarded to Battelle National Biodefense Institute by the Department of Homeland Security Science and Technology Directorate for the management and operation of the National Biodefense Analysis and Countermeasures Center, a Federally Funded Research and Development Center (V.W.).The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the US Government or its departments or of the institutions and companies affiliated with the authors, nor does mention of trade names, commercial products, or organizations imply endorsement by the US Government.The full disclaimer is on the Authors page of the full Report.

Table 1 .
Characteristics of members of the family