key: cord-0874119-fzwt0ia2
authors: Fenner, Frank
title: The classification and nomenclature of viruses summary of results of meetings of the International Committee on Taxonomy of Viruses in Madrid, September 1975
date: 1976-06-30
journal: Virology
DOI: 10.1016/0042-6822(76)90364-0
sha: 658e6f83e1348900667f14313ff45a131cebeace
doc_id: 874119
cord_uid: fzwt0ia2

nan

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] [11] [12] [13] [14] [15] [16] [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 hosts, 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 next 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 Report" will include, besides "approved" and common names of virus groups, a brief description of the properties of each group and a listing of probable and possible members of the group. To ensure that information upon the present state of viral taxonomy is available to as many virologists as possible, as soon as possible, the following brief paper has been prepared. It includes an up-to-data version of the Rules of Nomenclature, the names of all members of the new Executive Committee of ICTV, and a summary of the present position regarding viral families, genera, and groups and their names. For the convenience of working virologists, the last part has been set out with some relation to the "host-directed' interests of most virologists, although it will be seen that in several cases viral groupings transgress such boundaries.

The official approval of names for viral groups is subject to their legitimacy in terms of several "Rules," which are set out in the First Report on the Classification and Nomenclature of Viruses (Wildy, 1971) . At the meetings in Madrid several minor and two major changes in the Rules were approved by ICTV. The latter relate to Rule 4 (previously "An effort will be made towards a latinized binomial nomenclature") and Rule 7 [New sigla (i.e., "names made up from a few or initial letters) shall not be introduced"].

Over the nine years that have elapsed since the formation of ICTV (initially known as the International Committee on the Nomenclature of Viruses), it has become clear that virologists and teachers of virology greatly value the grouping of viruses into genera and families, based primarily on their chemistry, morphology, and strategy of multiplication. Latinized names, ending in " . . . uirus" for a genus and " . . . viridae" for a family name, have been widely accepted. On the other hand, there has been no support for latinized specific names (i.e., a latinized binomial nomenclature);

virologists have preferred to use vernacular names usually accompanied by a precise description of the strain and antecedents of the virus used for the investigations described. This situation was recognized by ICTV by the deletion of the word "binomial" from Rule 4. The use of sigla (e.g., "reovirus" from respiratory enteric orphan viruses) was popular with animal virologists prior to 1966, when ICNV was established, but in the interests of achieving a uniform and international nomenclature Rule 7, introduced at the first meetings of ICNV in Moscow in 1966, forbade the use of new sigla. The Plant Virus Subcommittees of the ICNV, which worked from 1966 to 1970, took exception to this rule and devised sigla for all the viral groups for which it recommended names at the meeting of ICNV in Mexico City in 1970. Since according to the Rules they were not legal, these names could not be approved by ICNV, and were therefore published in the First Report only as suggestions made by the Plant Virus Subcommittee (Wildy, 1971) . To break the deadlock that threatened international agreement on a single system of nomenclature for all viruses, several proposals were made for the modification of Rule 7. That finally accepted at the Madrid meeting led to the replacement of old Rule 7 by the following: "Sigla may be accepted as names of viruses or virus groups, provided that they are meaningful to workers in the fields and are recommended by international virus study groups." This change allowed ICTV, at the Madrid meeting, to approve the names for plant virus groups that were first proposed in 1970, and have been widely used by plant virologists since then.

Currently, the Rules are as set out below:

Rule 1. The code of bacterial nomenclature shall not be applied to viruses.

Rule 2. Nomenclature shall be international.

Rule 3. Nomenclature shall be universally applied to all viruses.

Rule 4. An effort will be made towards a latinized nomenclature.

Rule 5. Existing latinized names shall be retained whenever feasible.

Rule 6. The law of priority shall not be observed.

Rule 7. Sigla may be accepted as names of viruses or virus groups, provided that they are meaningful to workers in the fields and are recommended by international virus study groups.

Rule 8. No person's name shall be used.

Rule 9. Names should have international meaning.

Rule 10. The rules of Orthography of names and epithets are listed in Chapter 3, Section 6, of the proposed international code of nomenclature of viruses (Appendix C; Minutes of 1966, Moscow meeting).

Rule 11. For pragmatic purposes the species is considered to be a collection of viruses with like characters.

Rule 12. Numbers, letters, or combinations thereof may be accepted in constructing the names of species.

Rule 13. These symbols may be preceded by an agreed abbreviation of the latinized name of a selected host genus or, if necessary, by the full name.

Rule 14. The genus is a group of species sharing certain common characters.

Rule 15. The ending of the name of a Because of their medical and veterinary implications, and the availability of good cell culture systems for over twenty years, the range of viruses that cause disease in man and his domestic animals (although not several individual viruses like tobacco mosaic virus and some bacterial viruses) has been more thoroughly studied than those of other hosts. The description and nomenclature of these viruses is correspondingly more advanced. However, it is clear that in several cases viruses that are taxonomically similar to those that primarily infect vertebrates are found among invertebrates and plants, although not as yet among prokaryotes. Further, many viruses that infect vertebrates (and plants) also multiply in invertebrates (especially insects and acarids). Although these invertebrates are usually regarded by vertebrate and plant virologists as "vectors," they may indeed be the primary hosts in which these viruses evolved.

In the listing that follows are set out, first, viral groups that are represented by genera or other groupings in invertebrates and/or plant hosts as well as in vertebrate hosts; then, taxa that have so far been found only among vertebrates. For brevity, only approved names and minor comments are included except where the viral group involved was not described at all in Wildy (1971) . At the Madrid meetings, most of the distinctive groups of viruses of vertebrates were designated as families, some of which remain monogeneric at this stage, but may be expected to become polygeneric as knowledge increases. Enveloped virions 90-100 nm in diameter with at least one kind of peplomer and an internal ribonucleoprotein filament 2-2.5nm wide. Single-stranded RNA, total molecular weight about 6 x lo6 probably in several segments.

Bunyouirus (Bunyamwera and serologically closely related viruses) Several other genera will probably be defined later.

As mentioned above, the Plant Virus Subcommittee that operated between 1966 and 1970 presented 12 named subgroups to ICNV in 1970, but only three names-&omouirus, Cucumouirus, and Nepouiruswere then deemed legitimate and approved by ICNV. Following the change in Rule 7, which relates to sigla, and with the assurance that the group names suggested in 1970 were now in widespread use among plant virologists, the other nine names then proposed were approved by ICTV at the Madrid meeting. In addition the Plant Virus Subcommittee defined four new groups and their names were approved. The Plant Virus Subcommittee was reluc-tant to designate groups as either "families" or "genera"; their current names accord with the rules relating to genera but they are probably equivalent taxonomitally to what vertebrate, invertebrate, and bacterial virologists regard as families. However, most virus groups that are known only as viruses of plants are relatively homogenous;

if they were designated as families most would contain only one genus, often with many species.

Plant virology is in some respects in a less advanced state than vertebrate virology, because there are far fewer workers in the field and they lack a well-developed cell culture system, hence the concentration on disease characteristics, transmissibility, and the physical characters of virions. (Wildy, 1971, p. 65 ) (carnation latent virus group) (Wildy, 1971, p. 69 ) (cauliflower mosaic virus group) (Wildy, 1971, p. 37 ) (cowpea mosaic virus group) (Wildy, 1971, p. 48 ) (cucumber mosaic virus group) (Wildy, 1971 , p. 67) (tobacco ringspot virus group) (Wildy, 1971 , p. 59) (potato virus X group) (Wildy, 1971 , p. 70) (potato virus Y group) (Wildy, 1971 , p. 68) (tobacco mosaic virus group) (Wildy, 1971 , p. 60) (tobacco rattle virus group) (Wildy, 1971 , p. 58) (tomato bushy stunt virus group) (Wildy, 1971 , p. 62) (turnip yellow mosaic virus group) (Wildy, 1971, p Wildy, 1971, p. 32) Virologists Genus Molecular biology has been based upon Baculovirus (Bombyx mori nuclear poly-the intensive study of a few bacterial vihedrosis virus group). There are proba-ruses, and more is known of the chemistry and replicative mechanisms of some of these viruses than about any other living things. However, since they are of minor economic importance, comparative studies of bacterial viruses as such have hardly begun. Work by the Bacterial Virus Subcommittee over the past four years has revealed the great variety of different kinds of bacterial viruses, few of which have been characterized adequately to permit their grouping. The Bacterial Virus Subcommittee has suggested family names for six groups defined in the First Report (Wildy, 1971 ) and has described two additional groups of bacterial viruses and suggested family names for them. However, no definitive family or generic names were proposed for approval at the Madrid meeting. It was decided that the families and names suggested for them should be exposed to working virologists to determine their usefulness. A suggestion was made in Madrid, but not discussed at length, that names of viruses of prokaryotes should contain the syllables "bacti-" before "virus" or "viridae"; thus, "Myobactiviridae," etc., as set out (for genera) in the text of the Report of the Bacteriophage Subcommittee in 1970 (Wildy, 1971, p. 13-14) .

The groups proposed so far clearly fail to include many morphological types of bacteriophages (see Ackermann and Eisenstark, 1974) .

Proposed Families (names not official) Myoviridae (T-even phage group> (Wildy 1971, p. 30) : Linear double stranded DNA, molecular weight 120 x 106, complex contractile tail.

Styloviridae (A-phage group) (Wildy, 1971, p. 35) : Linear double-stranded DNA, molecular weight 33 x 106, long tail, noncontractile.

Corticoviridae (PM2 phage group) (Wildy, 1971, p. 40) : Cyclic doublestranded DNA, molecular weight 5 x lo", isometric virion, lipid between protein shells, no tail.

Microviridae ($x 174 group) ( Wildy , 1971, p. 42) : Cyclic single-stranded DNA, molecular weight 1.7 x lo", small "knobby" isometric virion.

Inoviridae (fd phage group) (Wildy, 1971, p. 43) : Cyclic single-stranded DNA, molecular weight 1.7 x 106, long filamentous virion.

Leviviridae (f2 phage group> (Wildy, 1971, p. 66) : Linear single-stranded RNA, molecular weight 1.2 x 106, small icosahedral virion.

Proposed New Families (name not official) Pedoviridae (T7 and related phage groups): Linear double-stranded DNA, molecular weight 25-27 x 106, short tail. Probably a complex group with several genera, or requiring further subdivision.

Cystoviridae (Phage 46 group): Linear double-stranded RNA, in three pieces; total molecular weight 13 x 10". Isometric virion with lipid-containing envelope.

The present state of phage taxonomy

Family and generic names for viruses approved by the International Committee on Taxonomy of Viruses

Classification and Nomenclature of Viruses. First Report of the International Committee on Nomenclature of Viruses