The results of the meetings of the International Committee on Taxonomy of Viruses, held in Madrid, September 1975, are briefly reported: rules of viral nomenclature, composition of the new Executive Committee, and a list of the names so far officially agreed. Introduction The International Committee on the Taxonomy of Viruses (ICTV), which is a committee of the Section on Virology of the International Association of Microbiological Societies (IAMS), completed a round of meetings during the Third International Congress for Virology that was held in Madrid from September 10--17, 1975. Since ICTV only meets during these conferences, which are held every four years, the meetings are important occasions for reviewing the classification and nomenclature of viruses. Decisions on new names, which encapsulate the recognition of natural "groups" of viruses, evolve slowly. Official approval for new names depends upon a series of sequential steps ; recommendations by one or more of the subcommittees of the Executive Committee of ICTV (subcommittees on Bacterial, Invertebrate, Plant and Vertebrate Viruses respectively, and for some of the larger viral groups which span several kinds of hos t s the Coordination Subcommittee), which are considered by the Executive Committee of ICTV and may finally be submitted for approval by ICTV itself. Only after this final approval does a name become "official". The results of the last five years of work by ICTV and its committees will be published early this year as a separate volume of "Intervirology", the official journal of the Section on Virology of IAMS, and additional copies will be produced for sale as separates. This "Second P~eport" will include, besides "approved" and common names of virus groups, a brief description of the properties of each

Classification and Nomenclature of Viruses

Coronaviruses (CoVs) are by far the largest group of known positive-sense RNA viruses having an extensive range of natural hosts. In the past few decades, newly evolved Coronaviruses have posed a global threat to public health. The immune response is essential to control and eliminate CoV infections, however, maladjusted immune responses may result in immunopathology and impaired pulmonary gas exchange. Gaining a deeper understanding of the interaction between Coronaviruses and the innate immune systems of the hosts may shed light on the development and persistence of inflammation in the lungs and hopefully can reduce the risk of lung inflammation caused by CoVs. In this review, we provide an update on CoV infections and relevant diseases, particularly the host defense against CoV-induced inflammation of lung tissue, as well as the role of the innate immune system in the pathogenesis and clinical treatment.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmv.25685

Coronavirus infections and immune responses.

This Review describes the type I interferonopathies — a set of Mendelian disorders associated with the upregulation of type I interferon activity. The authors explain how defects in key components of innate immune signalling pathways can lead to these diseases and discuss the immunological insights that have resulted from their study.

Aicardi–Goutières syndrome and the type I interferonopathies

Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are key sensors of virus infection, mediating the transcriptional induction of type I interferons and other genes that collectively establish an antiviral host response. Recent studies have revealed that both viral and host-derived RNAs can trigger RLR activation; this can lead to an effective antiviral response but also immunopathology if RLR activities are uncontrolled. In this Review, we discuss recent advances in our understanding of the types of RNA sensed by RLRs in the contexts of viral infection, malignancies and autoimmune diseases. We further describe how the activity of RLRs is controlled by host regulatory mechanisms, including RLR-interacting proteins, post-translational modifications and non-coding RNAs. Finally, we discuss key outstanding questions in the RLR field, including how our knowledge of RLR biology could be translated into new therapeutics.

/pdf/rig-i-like-receptors-their-regulation-and-roles-in-rna-2e64vkg5ox.pdf

RIG-I-like receptors: their regulation and roles in RNA sensing

The oligonucleotide therapeutics field has seen remarkable progress over the last few years with the approval of the first antisense drug and with promising developments in late stage clinical trials using siRNA or splice switching oligonucleotides. However, effective delivery of oligonucleotides to their intracellular sites of action remains a major issue. This review will describe the biological basis of oligonucleotide delivery including the nature of various tissue barriers and the mechanisms of cellular uptake and intracellular trafficking of oligonucleotides. It will then examine a variety of current approaches for enhancing the delivery of oligonucleotides. This includes molecular scale targeted ligand-oligonucleotide conjugates, lipid- and polymer-based nanoparticles, antibody conjugates and small molecules that improve oligonucleotide delivery. The merits and liabilities of these approaches will be discussed in the context of the underlying basic biology.

The delivery of therapeutic oligonucleotides.

Mammalian cells possess mechanisms to detect and defend themselves from invading viruses. In the cytosol, the RIG-I-like receptors (RLRs), RIG-I (retinoic acid-inducible gene I; encoded by DDX58) and MDA5 (melanoma differentiation-associated gene 5; encoded by IFIH1) sense atypical RNAs associated with virus infection. Detection triggers a signalling cascade via the adaptor MAVS that culminates in the production of type I interferons (IFN-α and β; hereafter IFN), which are key antiviral cytokines. RIG-I and MDA5 are activated by distinct viral RNA structures and much evidence indicates that RIG-I responds to RNAs bearing a triphosphate (ppp) moiety in conjunction with a blunt-ended, base-paired region at the 5'-end (reviewed in refs 1, 2, 3). Here we show that RIG-I also mediates antiviral responses to RNAs bearing 5'-diphosphates (5'pp). Genomes from mammalian reoviruses with 5'pp termini, 5'pp-RNA isolated from yeast L-A virus, and base-paired 5'pp-RNAs made by in vitro transcription or chemical synthesis, all bind to RIG-I and serve as RIG-I agonists. Furthermore, a RIG-I-dependent response to 5'pp-RNA is essential for controlling reovirus infection in cultured cells and in mice. Thus, the minimal determinant for RIG-I recognition is a base-paired RNA with 5'pp. Such RNAs are found in some viruses but not in uninfected cells, indicating that recognition of 5'pp-RNA, like that of 5'ppp-RNA, acts as a powerful means of self/non-self discrimination by the innate immune system.

/pdf/antiviral-immunity-via-rig-i-mediated-recognition-of-rna-1mcfcacaio.pdf

Antiviral immunity via RIG-I-mediated recognition of RNA bearing 5′-diphosphates

Portable encapsidation signal of the L-A double-stranded RNA virus of S. cerevisiae

Saccharomyces cerevisiae has been a key experimental organism for the study of infectious diseases, including dsRNA viruses, ssRNA viruses and prions. Studies of the mechanisms of virus and prion replication, virus structure and structure of the amyloid filaments that are the basis of yeast prions have been at the forefront of such studies in these classes of infectious entities. Yeast has been particularly useful in defining the interactions of the infectious elements with cellular components: chromosomally encoded proteins necessary for or blocking the propagation of the viruses and prions, and proteins involved in expression of viral components. Here we emphasize the L-A dsRNA virus and its killer-toxin-encoding satellites, the 20S and 23S ssRNA naked viruses, and the several infectious proteins (prions) of yeast.

/pdf/viruses-and-prions-of-saccharomyces-cerevisiae-qnt3w16h4p.pdf

Viruses and prions of Saccharomyces cerevisiae.

https://www.cell.com/cell/pdf/0092-8674(88)90225-5.pdf

Gene overlap results in a viral protein having an RNA binding domain and a major coat protein domain

DOUBLE-STRANDED RNA viruses have an RNA-dependent RNA polymerase activity associated with the viral particles which is indispensable for their replication cycle. Using the yeast L-A double-stranded RNA virus we have investigated the mechanism by which the virus encapsidates its genomic RNA and RNA polymerase. The L-A gag gene encodes the principal viral coat protein and the overlapping pol gene is expressed as a gag–pol fusion protein which is formed by a −1 ribosomal frameshift1–3. Here we show that Gag alone is sufficient for virus particle formation, but that it fails to package the viral single-stranded RNA genome. Encapsidation of the viral RNA requires only a part of the Pol region (the N-terminal quarter), which is presumably distinct from the RNA polymerase domain. Given that the Pol region has single-stranded RNA-binding activity, these results are consistent with our L-A virus encapsidation model1: the Pol region of the fusion protein binds specifically to the viral genome (+) strand, and the N-terminal gag-encoded region primes polymerization of Gag to form the capsid, thus ensuring the packaging of both the viral genome and the RNA polymerase.

Tsutomu Fujimura

Papers

Antiviral immunity via RIG-I-mediated recognition of RNA bearing 5′-diphosphates

Portable encapsidation signal of the L-A double-stranded RNA virus of S. cerevisiae

Viruses and prions of Saccharomyces cerevisiae.

Gene overlap results in a viral protein having an RNA binding domain and a major coat protein domain

Pol of gag-pol fusion protein required for encapsidation of viral RNA of yeast L-A virus.