Release of Viral Glycoproteins during Ebola Virus Infection

AbstractMaturation and release of the Ebola virus glycoprotein GP were studied in cells infected with either Ebola or recombinant vaccinia viruses. Significant amounts of GP were found in the culture medium in nonvirion forms. The major form represented the large subunit GP1that was shed after release of its disulfide linkage to the smaller transmembrane subunit GP2. The minor form were intact GP1,2complexes incorporated into virosomes. Vector-expressed GP formed spikes morphologically indistinguishable from spikes on virus particles, indicating that spike assembly is independent of other viral proteins. Analysis of a truncation mutant revealed an early and almost complete release of GP1,2molecules, showing that membrane anchoring is mediated by the carboxy-terminal hydrophobic domain of GP2. We have also compared wild-type virus which requires transcriptional editing for synthesis of full-length GP with a variant that does not depend on editing. Both viruses released comparable amounts of GP1, but the variant expressed only minute amounts of the small, soluble GP which is the expression product of nonedited mRNA species of the GP gene. The abundant shedding of soluble GP1may play an important role in the immunopathology of Ebola hemorrhagic fever in experimentally and naturally infected hosts

Proposal for a revised taxonomy of the family Filoviridae: classification, names of taxa and viruses, and virus abbreviations

The taxonomy of the family Filoviridae (marburgviruses and ebolaviruses) has changed several times since the discovery of its members, resulting in a plethora of species and virus names and abbreviations. The current taxonomy has only been partially accepted by most laboratory virologists. Confusion likely arose for several reasons: species names that consist of several words or which (should) contain diacritical marks, the current orthographic identity of species and virus names, and the similar pronunciation of several virus abbreviations in the absence of guidance for the correct use of vernacular names. To rectify this problem, we suggest (1) to retain the current species names Reston ebolavirus, Sudan ebolavirus, and Zaire ebolavirus, but to replace the name Cote d'Ivoire ebolavirus [sic] with Taï Forest ebolavirus and Lake Victoria marburgvirus with Marburg marburgvirus; (2) to revert the virus names of the type marburgviruses and ebolaviruses to those used for decades in the field (Marburg virus instead of Lake Victoria marburgvirus and Ebola virus instead of Zaire ebolavirus); (3) to introduce names for the remaining viruses reminiscent of jargon used by laboratory virologists but nevertheless different from species names (Reston virus, Sudan virus, Taï Forest virus), and (4) to introduce distinct abbreviations for the individual viruses (RESTV for Reston virus, SUDV for Sudan virus, and TAFV for Taï Forest virus), while retaining that for Marburg virus (MARV) and reintroducing that used over decades for Ebola virus (EBOV). Paying tribute to developments in the field, we propose (a) to create a new ebolavirus species (Bundibugyo ebolavirus) for one member virus (Bundibugyo virus, BDBV); (b) to assign a second virus to the species Marburg marburgvirus (Ravn virus, RAVV) for better reflection of now available high-resolution phylogeny; and (c) to create a new tentative genus (Cuevavirus) with one tentative species (Lloviu cuevavirus) for the recently discovered Lloviu virus (LLOV). Furthermore, we explain the etymological derivation of individual names, their pronunciation, and their correct use, and we elaborate on demarcation criteria for each taxon and virus.S

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)

Filovirus RefSeq Entries: Evaluation and Selection of Filovirus Type Variants, Type Sequences, and Names

Sequence determination of complete or coding-complete genomes of viruses is becoming common practice for supporting the work of epidemiologists, ecologists, virologists, and taxonomists. Sequencing duration and costs are rapidly decreasing, sequencing hardware is under modification for use by non-experts, and software is constantly being improved to simplify sequence data management and analysis. Thus, analysis of virus disease outbreaks on the molecular level is now feasible, including characterization of the evolution of individual virus populations in single patients over time. The increasing accumulation of sequencing data creates a management problem for the curators of commonly used sequence databases and an entry retrieval problem for end users. Therefore, utilizing the data to their fullest potential will require setting nomenclature and annotation standards for virus isolates and associated genomic sequences. The National Center for Biotechnology Information’s (NCBI’s) RefSeq is a non-redundant, curated database for reference (or type) nucleotide sequence records that supplies source data to numerous other databases. Building on recently proposed templates for filovirus variant naming [ ()////-], we report consensus decisions from a majority of past and currently active filovirus experts on the eight filovirus type variants and isolates to be represented in RefSeq, their final designations, and their associated sequences

Virus nomenclature below the species level : a standardized nomenclature for laboratory animal-adapted strains and variants of viruses assigned to the family Filoviridae

The International Committee on Taxonomy of Viruses (ICTV) organizes the classification of viruses into taxa, but is not responsible for the nomenclature for taxa members. International experts groups, such as the ICTV Study Groups, recommend the classification and naming of viruses and their strains, variants, and isolates. The ICTV Filoviridae Study Group has recently introduced an updated classification and nomenclature for filoviruses. Subsequently, and together with numerous other filovirus experts, a consistent nomenclature for their natural genetic variants and isolates was developed that aims at simplifying the retrieval of sequence data from electronic databases. This is a first important step toward a viral genome annotation standard as sought by the US National Center for Biotechnology Information (NCBI). Here, this work is extended to include filoviruses obtained in the laboratory by artificial selection through passage in laboratory hosts. The previously developed template for natural filovirus genetic variant naming ( //<year of sampling>/-) is retained, but it is proposed to adapt the type of information added to each field for laboratory animal-adapted variants. For instance, the full-length designation of an Ebola virus Mayinga variant adapted at the State Research Center for Virology and Biotechnology “Vector” to cause disease in guinea pigs after seven passages would be akin to “Ebola virus VECTOR/C.porcellus-lab/COD/1976/Mayinga- GPA-P7”. As was proposed for the names of natural filovirus variants, we suggest using the fulllength designation in databases, as well as in the method section of publications. Shortened designations (such as “EBOV VECTOR/C.por/COD/76/May-GPA-P7”) and abbreviations (such as “EBOV/May-GPA-P7”) could be used in the remainder of the text depending on how critical it is to convey information contained in the full-length name. “EBOV” would suffice if only one EBOV strain/variant/isolate is addressed.This work was funded in part by the Joint Science and Technology Office for Chem Bio Defense (proposal #TMTI0048_09_RD_T to SB).http://www.springerlink.com/content/0304-8608/hb2013ab201

Virus nomenclature below the species level : a standardized nomenclature for filovirus strains and variants rescued from cDNA

Specific alterations (mutations, deletions, insertions) of virus genomes are crucial for the functional characterization of their regulatory elements and their expression products, as well as a prerequisite for the creation of attenuated viruses that could serve as vaccine candidates. Virus genome tailoring can be performed either by using traditionally cloned genomes as starting materials, followed by site-directed mutagenesis, or by de novo synthesis of modified virus genomes or parts thereof. A systematic nomenclature for such recombinant viruses is necessary to set them apart from wild-type and laboratoryadapted viruses, and to improve communication and collaborations among researchers who may want to use recombinant viruses or create novel viruses based on them. A large group of filovirus experts has recently proposed nomenclatures for natural and laboratory animal-adapted filoviruses that aim to simplify the retrieval of sequence data from electronic databases. Here, this work is extended to include nomenclature for filoviruses obtained in the laboratory via reverse genetics systems. The previously developed template for natural filovirus genetic variant naming,\virus name[(\strain[/)\isolation host-suffix[/ \country of sampling[/\year of sampling[/\genetic variant designation[-\isolate designation[, is retained, but we propose to adapt the type of information added to each field for cDNA clone-derived filoviruses. For instance, the full-length designation of an Ebola virus Kikwit variant rescued from a plasmid developed at the US Centers for Disease Control and Prevention could be akin to ‘‘Ebola virus H.sapiens-rec/COD/1995/Kikwit-abc1’’ (with the suffix ‘‘rec’’ identifying the recombinant nature of the virus and ‘‘abc1’’ being a placeholder for any meaningful isolate designator). Such a full-length designation should be used in databases and the methods section of publications. Shortened designations (such as ‘‘EBOV H.sap/COD/95/ Kik-abc1’’) and abbreviations (such as ‘‘EBOV/Kik-abc1’’) could be used in the remainder of the text, depending on how critical it is to convey information contained in the full-length name. ‘‘EBOV’’ would suffice if only one EBOV strain/variant/isolate is addressed.http://link.springer.com/journal/705hb201

Taxonomy of the order Mononegavirales: update 2017.

In 2017, the order Mononegavirales was expanded by the inclusion of a total of 69 novel species. Five new rhabdovirus genera and one new nyamivirus genus were established to harbor 41 of these species, whereas the remaining new species were assigned to already established genera. Furthermore, non-Latinized binomial species names replaced all paramyxovirus and pneumovirus species names, thereby accomplishing application of binomial species names throughout the entire order. This article presents the updated taxonomy of the order Mononegavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV)

Characterization of a Novel Neutralizing Monoclonal Antibody Against Ebola Virus GP

Ebola virus is the etiological agent of a severe hemorrhagic fever with a high mortality rate. As the only protein exposed on the surface of viral particles, the spike glycoprotein GP is the unique target for neutralizing mono-clonal antibodies. In this study, we demonstrate the strong neutralization capacity of the monoclonal antibody #3327 and characterize its activity. GP residues that are required for recognition and neutralization were found to be located both in the internal fusion loop and in the receptor-binding domain. Analysis of Ebola virus entry in the presence of #3327 allows us to hypothesize that this antibody binds to the virus particle before internal-ization and endosomal processing of GP and likely prevents the final viral fusion step. Importantly, #3327 is able to block entry of virions bearing GP that contain the Q508 escape mutation common to a number of virus-neutralizing antibodies, and therefore provides future perspectives for treatment strategies against Ebola virus infection. Keywords. Ebola virus; glycoprotein GP; virus neutralizing antibody; filovirus. Ebola virus (EBOV) causes a severe form of hemorrhagic fever in humans and nonhuman primates [1–3]. EBOV is member of the family Filoviridae, a group of en-veloped, nonsegmented, negative-strand RNA viruse

Entry of Ebola Virus is an Asynchronous Process

International audienceEbola virus (EBOV) is responsible for a severe fever with a high mortality rate. The diverse nature of the attachment of the virus to the cell surface, the initial step of virus entry, raises questions concerning the kinetics of the virus internalization process. We investigated EBOV entry kinetics using the activity of a particular monoclonal antibody that neutralizes virus infectivity. We demonstrate that inoculation of cells with EBOV results in an asynchronous entry process, as revealed by the ability of the virus to remain in a cell-bound state for an extended period of time before it is internalized