VIRUSES (Latin. virus poison) — the noncellular life forms possessing own genome and capable to reproduction only in cells of more high-organized beings. Two forms of existence in general are characteristic of V.: extracellular, or based, and intracellular, breeding (reproduced), or vegetative. Synonyms of the first name are also the terms «virus particle», «virus corpuscles», «virion», synonyms of the second — «a complex a virus — a cell».
Exist in the nature century, being transferred from one owner to another. V.'s reproduction can occur only intracellularly in this connection V. are obligate intracellular parasites of animals, plants, insects, bacteria, mushrooms and other classes of living beings. Intracellular parasitism of V. is caused by that circumstance that they owing to extreme simplicity of the organization use for the reproduction the cellular synthetic device (ribosomes, membranes), enzymes and the power generating systems. Communication between two forms of existence of V. is carried out through nucleinic to - that virion, edges induces virusospetsifichesky sinteza and, eventually, formation of affiliated virus particles in the infected cell. Different types of V. at an extracellular stage of existence are characterized by rather big variability of the sizes (from 15 — 18 to 3000 — 3500 nanometers). The largest difficult arranged V. from a sort of poks-viruses (Poxvirus), belong to Krom causative agents of smallpox and V. of a variolovaccine, are distinguishable in a usual light microscope, but the most part of V. has the submicroscopic sizes and is distinguishable only in a supermicroscope.
- 1 Chemical composition of virions and property of virus components
- 2 The structure of virus particles
- 3 Serological properties of viruses
- 4 The complex a virus — a cell and the main patterns of a reproduction of viruses
- 5 Classification and the nomenclature of viruses
- 6 A morphogenesis of viruses
- 7 Genetics of viruses of vertebrata
- 8 Viruses of invertebrates
- 9 Viruses of plants
- 10 Table. CLASSIFICATION of VIRUSES according to 1975
- 11 CLASSIFICATION of VIRUSES of the PERSON AND ANIMALS (according to the International committee on taxonomy of viruses, 1982)
Chemical composition of virions and property of virus components
Virus particles are characterized by simplicity of the chemical structure though between various representatives of a kingdom of viruses there are significant differences. On this sign of V. in general are divided into two big groups: simple and difficult. In a typical case the first V. consist only of protein and nucleinic to - you whereas V. difficult along with these components contain in the structure lipids and carbohydrates, as a rule, in the form of glycoproteins.
In turn within these two groups there are also gradation. So, within the first group B. it is possible to allocate two subgroups differing on degree of complexity of the proteinaceous component. One subgroup is formed by V. which protein consists of one type of peptide chains. The most part of V. of plants concerns to those, and in particular V. of a tobacco mosaic (sort Tobamovirus), protein to-rogo consists of 2320 identical polypeptides formed by 158 amino acids. The second subgroup includes V. which protein is formed by several types of polypeptide chains. Various representatives of this subgroup in turn differ by quantity and a type of polypeptide chains. The most just organized V. of animals belonging to the sort Parvovirus contain three types of polypeptide chains, napr, adenosatellitny V., latent V. Kilkhem, etc. Difficult arranged V. like variolovaccine (sort Poxvirus) in virion have about 20 various proteins, including own enzymes. As a rule, complexity of composition of protein correlates with complexity of the structural organization of virion.
Thus, in a typical case virions represent nucleoproteids, i.e. a complex of protein and nucleinic to - you. An exception of this rule are various defective mutants of V., both natural, and artificially received which are not capable to synthesize own protein at all or synthesize the defective protein incapable to form a normal cover of a virus particle. It is possible to carry options B. of a pogremkovost of tobacco, some strains of V. of a tobacco mosaic which under natural conditions in the infected cells exist in the form of a complex with cellular proteins to such defective V.' number, and also the defective options B. of sarcoma of Raus incapable to synthesize the outside cover, formation a cut it is provided with a virus assistant (V. of a bird's leukosis).
Century contrary to cellular life forms contain in composition of virions only one of two types nucleinic to - you: RNA or DNA representing a genome of a virus particle. Thus, RNA, for a cut were fixed in a cell only functions structural and metabolic, at V. can carry out, as well as DNA, functions genetic.
A big variety of forms of nucleic acids, including existence of such RNA and DNA forms which are absent at cellular life forms is characteristic of V.
At the same time primary structure of RNA and other V.' DNA does not find any anomalies in comparison with cellular forms nucleinic to - t. However at many
V. containing DNA the last is presented not by the linear, but covalent closed ring molecule. Such DNA form is found in representatives of childbirth of polioma-viruses (Polyomavirus), papillomaviruses (Papillomavirus) and lipovirus (Lipovirus).
From the anomalies connected with secondary structure of nucleic acids B. and which are not found among cellular nucleic acids it is interesting to note existence of one-filamentous DNA and two-spiral RNA. The first is found in representatives of the sorts Bullavirus and Inovirus, and also among parvoviruses is (Parvovirus): small V. of mice, latent V. of rats of Kilkhem and adenosatellitny Century. Two-spiral RNA is present at reoviruses (sort Reovirus) and V. of wound tumors of plants, dwarfism of rice and a cytoplasma poliedroz which patrimonial accessory is definitely not established so far.
Nucleic acids practically of all just organized V. have infectivity. At infection of sensitive owners with deproteined drugs DNA or RNA of these V. the typical infectious process which is coming to an end with formation of mature virions of posterity is observed. The range of the owners and cells infected with drugs of infectious nucleic acids are wider in comparison with a natural host range of this V. since in this case there are no restrictions imposed by specific interaction of receptors of V. and a cell. Infectivity is absent at the drugs RNA emitted from difficult V. (mikso-, paramikso-, Rhabdoviruses).
Some V. incapable to synthesize proteins of the cover, can exist even under natural conditions in the form of free RNA. The found etiological agents who are causing a veretenovidnost of tubers of potatoes and an ekzokortisny disease of a citrus and received the special name «viroida» represent the free low-molecular RNA similar by the sizes to TRNK or 5sPHK. Infection of plants of potatoes and a citrus with drugs of this RNA causes a typical picture of diseases and replication of viroidny RNA.
The lipidic component B. is investigated rather well only at orthomyxoviruses, paramyxoviruses and an arbovirus (childbirth of Orthomyxovirus, Paramyxovirus, Fiavivirus and Alphavirus). Source of an origin of lipids in this case is the cellular membrane from where V. in the course of maturing borrows the lipidic component. Glycoproteins are a part of superficial formations of virus particles, e.g. hemagglutinins at myxoviruses and paramyxoviruses. Ways of their synthesis are not studied yet.
The structure of virus particles
Protein of virions performs double function. First, it forms the outside cover (capsid) protecting nucleinic to - that a virus particle. Nucleinic to - that with the protein surrounding it is designated by the term «nucleocapsid», or «nucleoid». The last term is usually applied by morphologists to designation of the internal textural features containing nucleinic to - that at the vertebrata who are difficult arranged to V. At just organized V. the terms «nucleocapsid» and «virion» are in essence identical, but many difficult arranged V. along with a proteinaceous capsid have one more or several external covers, most often lipidic or proteinaceous for which designation use the term «supercapsid». So, V. of flu have internal threadlike nucleoproteid (nucleocapsid) known under the name of internal antigen, or S-antigen concluded in a proteinaceous basal membrane and an external lipoprotein cover (supercapsid).
For performance of the protective functions V.'s capsid shall have rather high stability, especially in relation to such factors of the intracellular environment as destructive enzymes. In this regard the native unimpaired virions are steady against high concentration of proteolytic enzymes. The exception of this rule is made only by the little, difficult arranged V. as, e.g., an arbovirus of group B (sort Flavivirus). This stability is caused by the high-arranged tertiary and quarternary structure of proteinaceous subunits (capsomeres) as a part of a capsid thanks to what the peptide bonds sensitive to proteases are sterically unavailable to effect of enzymes. After a partial denaturation or degradation the proteinaceous capsid of V. is easily hydrolyzed by proteases.
The second function of a capsid consists in ensuring adsorption of V. only on those cells where there can be their reproduction. Such specificity of interaction of V. with a limited host range is provided with existence on the surface of virions of specific receptors which correspond to certain receptors on a surface of cells. When V. are deprived of specialized receptors as, e.g., V. of plants, their hit in cells of natural owners is caused by certain carriers.
All V. representing a «naked» nucleocapsid though their cover can consist of several types of polypeptide chains are among simple. In this case the structure of virus particles submits to strict rules of symmetry (see. Symmetry ). At difficult arranged V. having highly - the differentiated structure and supercapsids, symmetry, as a rule, becomes more difficult.
Serological properties of viruses
As V. contain proteins, and in some cases glycoproteins and lipoproteids, virions bear the certain antigenic determinants causing formation of specific antibodies both at natural forms of an infection and in experiments on immunization of laboratory animals. Just arranged V. containing one type of protein cause formation of one type of antibodies, difficult arranged V. containing different types of proteins and different structural-morphological components bear several types of antigens.
Extracellular V. at contact with antibodies against outside antigens lose the infectivity (are neutralized), but from a noninfectious complex a virus — an antibody it is possible to receive infectious virions again after dissociation of such complex at influence of acid pH, temperature and high ionic strength. Century antiserums, intracellular to neutralized action, are steady, and such reception is quite often used for studying of adsorption and V.'s penetration into cells.
On a role of antibodies in immunity to viral infections there is no uniform point of view that, apparently, is connected with distinctions in different V.' biology, ways of their distribution and circulation in an organism, places of synthesis, availability to antibodies, etc. (see. virus-induced immunity ).
The complex a virus — a cell and the main patterns of a reproduction of viruses
in general is characteristic Of V. the so-called disjunctus disjunctive (Latin separated) the way of a reproduction meaning that in the course of V.'s replication parent virion per se disappears.
In the infected cell presence of virus particles is not found neither by means of serological, nor by means of elektronnomikroskopichesky methods up to late stages of an infection when the first affiliated virions appear (so-called stage of latency of an infection, pre-trial detention centers of a nimama to-rogo are the terms «eklips-period», «period of masking», a phase of change of information — «si-phase»).
V.'s penetration into a cell happens on the mechanism close to to a pinocytic (see), but the net result remains to same (fig. 1). In this case the infecting virion after adsorption on cellular receptors is taken a cellular membrane, edges vpyachivatsya in a cell, forming a vacuole. In the course of interaction of virion with a cellular membrane its capsid undergoes destructive changes and gains sensitivity to cellular proteases which destroy virus protein, releasing virus nucleinic to - that. At difficult arranged V. from the sorts Poxvirus, Paramyxovirus, Orthomyxovirus and Rhabdovirus the course of this process is complicated by the fact that removal of a supercapsid and capsid of nucleoid is separated in time and passes in two stages. At the same time nucleinic to - that can be transcribed directly as a part of the nucleocapsid or nucleoid exempted from a supercapsid. Process of a transcription in this case is carried out by means of the virus RNA polymerases which are a part of nucleoid (see. Transcription ).
The following feature of a disjunctive way of a reproduction of V. consists that synthesis of elements virus a corpuscle is carried out in the form of pools (exchange collections) which are separated both in space, and in time. Nucleinic to - that a virus can be replicated, e.g., in a kernel or a kernel, protein can be synthesized in cytoplasm, and assembly of the whole virions or nucleocapsids can happen on an inner surface of a cytoplasmic membrane. At last, the difficult lipoprotein supercapsid can be got by V. in the course of an otpochkovaniye.
The subsequent stage of a reproduction (after penetration virus nucleinic to - you in a cell) is synthesis of the virusospetsifichesky enzymes and proteins necessary for V.'s replication (the so-called early proteins which are not a part of virions). Details of this process at different V. differ depending on what type nucleinic to - you are a part of virions. At the most part of V. which contain one-filamentous RNA the last is capable to carry out at the same time both functions of a genetic determinant, and function of own information RNA — so-called (+) chains. These parent (+) chains of RNA directly contact ribosomes and are broadcast, i.e. direct in them synthesis of virusospetsifichesky proteins. In this case broadcasting virus (+) matrixes will be the first act of virusospetsifichesky sintez in the infected cell. V. containing DNA both the one-filamentous, and two-filamentous, and also one-filamentous RNA incapable of broadcasting (—) of a chain, or two-filamentous RNA, the first synthetic act shall have a formation of a complementary polynucleotide chain, i.e. synthesis of virusospetsifichesky early information RNA.
It is natural that this process shall be carried out by means of virus or cellular RNA polymerases. If in a cell there are DNA-dependent RNA polymerases capable to transcribe virus DNA, then there is no RNA-dependent of RNA polymerases in a normal cell. In this regard the last enzyme for implementation of primary act of a transcription of RNA shall get into a cell together with the infecting virus RNA, as a rule, as a part of nucleoid or a nucleocapsid. Further, after broadcast of infectious RNA in the infected cell there are also affiliated, i.e. again synthesized RNA-dependent of a RNA polymerase.
At the third stage of a virus reproduction there is a replication virus nucleinic to - you, edges in case of two-spiral nucleic acids is carried out on the known symmetric semi-conservative mechanism, and in case of one-filamentous nucleic acids — on the asymmetric semi-conservative mechanism, through a stage of replikativny (Russian Federation) and replikativny intermediate (RPF) of forms. Apparently from the scheme submitted in fig. 2, on a matrix parent (+) chains it is synthesized complementary by it (—) a chain therefore there is the two-spiral Russian Federation.
Then on a matrix (—) or (+) chains simultaneous synthesis of several (+) or (—) polynucleotide chains, respectively begins and there is RPF.
The fourth stage of a reproduction is a synthesis of the information RNA coding late proteins, to-rymi the constitutive proteins which are a part of virions are. At the same time also formation of virions begins.
As showed G. Schramm and H. Fraenkel-Conrat's works, individual polypeptide chains of such simple V. as V. of a tobacco mosaic, at neutral or subacidic pH values are capable to aggregate spontaneously in solution, forming virus-like particles (proteinaceous capsids). In the presence in solution nucleinic to - you these V. occur the automatic assembly of infectious virus particles proceeding as purely physical. - chemical reaction of aggregation and not demanding participation of accessory factors. Similarly there is also an assembly of virions in the infected cells after concentration of virus RNA and protein in the corresponding pools reaches a critical level. At difficult arranged V. the principles of self-assembly remain only at the level of separate components of virus particles whereas assembly of these components in a whole demands participation of many accessory factors and enzymes which in itself mature virions are not included. Such morfopoetichesky factors of V. are synthesized at this stage of an infection together with the constitutional virus proteins. (See below Morphogenesis of viruses .)
The final stage of a viral infection which is closed with formation of mature virions comes to an end with release of affiliated virus particles on Wednesday. Depending on the structural organization and complexity of virions, and also this V.'s biology and its relationship with a cell of the owner this process can be carried out differently at different groups B. Viruses can or lyse one way or another cells, causing a cytopathic effect (pathogenic, or lytic, viruses), or to be released from a cell, without destroying it (an asymptomatic infection). At lytic, pathogenic V. of vertebrata and invertebrates destruction of a cell is reached or due to activation of lysosomes, or by intensive damage of cellular membranes in the course of an otpochkovaniye.
Many virus strains and even types have this or that genetic defect and are capable to be reproduced only in the presence of other V. — assistants. Classical examples are: Bryan V. strain of sarcoma Rausa which is replicated only in the presence of V. of a bird's leukosis; the adenosatellitny V. capable to breed in the presence of full-fledged adenovirus, the small satellite V. of a necrosis of tobacco needing for a successful reproduction in the presence of coarse particles of V. of a necrosis of tobacco. Adenosatellitny V.'s DNA and RNA B. of a necrosis of tobacco contain information for synthesis of own core protein and do not contain the complete information for replication in a cell.
Along with it there is as well very a RNA-containing B. big group of plants with the fragmented genome which is distributed among several types of the particles forming infectious drug only in the presence of all components.
So, infectious drug B. of a mosaic of cow peas consists of three types of virions with coefficients of sedimentation 58S, 95S and 115S, V. of a mosaic of a lucerne — of five various components with coefficients of sedimentation 99S, 83S, 76S, 68S, 61S and 53S. Multi-component systems are also V. of a mosaic of a fire, V. of a streak of tobacco and some other. Each of these V.' components with the fragmented genome in itself not infektsionen also contains only a certain part of the genetic information necessary for successful functioning of all system in general.
Relationship between viruses and cells differs in big complexity and is defined both by type of a virus, and a genome of a cell and it fiziol, a state.
The virus genome in the infected cell can enter certain genetic relations with a genome of a cell. On this sign of V. it is possible to divide into two big groups: with autonomous replication of genomes (infectious viruses) and V. capable to interact in one way or another with a cellular genome (integration viruses). The last group includes oncogenic V., nucleinic to - that which it is capable to be built in (to be integrated) in one way or another a cellular chromosome in the form of a pro-virus, causing transformation of cells (see. Transformation ). Borders between these groups are very conditional, and the same V. depending on a type of cells can behave either as infectious or as integration. Century with autonomous replication of genomes in turn can be in relation to one owners pathogenic, and in relation to other owners neutral. All integration V. to some extent enter the symbiotic relations with a cell of the owner.
Lytic, or pathogenic, the way of development of an infection is defined by the fact that cells where there is V.'s reproduction, eventually perish.
The lethal outcome of an infection for a cell can be caused by a number of the independent reasons: 1) specific and irreversible blocking of activity of a cellular genome at early stages of an infection; 2) nonspecific damages of a cellular genome in the course of an infection; 3) switching of metabolic resources of a cell to virusospetsifichesky sinteza; 4) the specific lysis of a cell connected with need of release of affiliated virus particles on Wednesday; 5) disturbance of structure of cellular membranes as a result of an intensive exit of virus particles on Wednesday, especially in the course of an otpochkovaniye, and some other.
Apparently from this list, only the first and third reasons are connected with the specific cytotoxic or cytopathic action programmed in a virus genome and which is implemented in the course of an infection. Other of the listed reasons leading to death of cells strictly are not determined and caused generally by intensity of virusospetsifichesky sintez. Therefore at some restrictions in the speed of synthesis and release of mature virus particles on Wednesday the cell can keep the viability and a long time to produce virus particles. It is undoubted that such neutral type of relationship which is the cornerstone of asymptomatic infections, certainly, is favorable to V. as a look and represents the smallest evil for the owner.
At last, between V. and cells there can be also quite symbiotic relations when undoubted benefits are received by both partners of a complex. Examples such can be found at oncogenous V. It is known that transformation of cells by oncogenous V. creates also hindrances for superinfection in the form of an interference phenomenon (see the Interference of viruses).
Benefits which gain V. at such integration way developments of an infection are also undoubted. First of all replication nucleinic to - you is entirely provided to V. with cells as the pro-virus is a part of a cellular chromosome. Therefore each daughter cell formed as a result of division of a parent cell bears in itself a pro-virus that provides vertical transfer of V. and its distribution within this type of owners.
Classification and the nomenclature of viruses
In 1966 on the IX International congress of microbiologists in Moscow the International committee on the nomenclature of viruses (MKNV) which was renamed into the International committee on taxonomy of viruses (MKTV) later was created. MKTV is body virusol. sections of the International association of microbiologists also consists of representatives of national societies. At MKTV subcommittees according to
V. of vertebrata, invertebrates, plants and bacteria which incorporate so-called groups of studying of separate sections are formed; e.g., in V.'s subcommittee of vertebrata there are groups of studying of enteroviruses, reoviruses, arbovirus, etc.
Collection of information about V. and its systematization are carried out according to V.'s characteristic on the following main indicators: a) nucleinic to - those, to proteins, lipids, carbohydrates, morphology and physical. - to chemical properties; b) replications; c) to phenomena of genetic interactions; d) to a host range; e) pathogenicity; e) to geographical distribution; g) to a way of transfer; h) to antigenic properties. The importance of each of indicators in creation of hierarchical system is still not up to the end defined, but, apparently, the first will form a basis of formation of large taxonomical groups (family above).
The community of an antigenic structure is an obligatory sign at identification of species.
In modern classification V. (table) are considered as uniform system, irrespective of a circle of the main owners (vertebrata, invertebrates, plants, bacteria). Creation of the full hierarchical system similar to the classification of animals including such taxonomical groups as a look, a sort, family, an order, a class, and, perhaps, higher categories is supposed. It was not succeeded to reach accurate definition of the concepts «look» and «sort» yet. Understand group B. with identical properties under a look, and the sort represents group B., the general properties, similar on a row.
The binomial nomenclature is applied to V., according to a cut the name of a look consists of patrimonial and specific names. Owing to the developed habits in V.'s nomenclature already existing names, including alphabetic and digital generally remain if they are obshcheupotrebitelna. New names are created by rules of word formation in Latin and Greek languages. The name of orders terminates on «-ales», families — on «-idae», the generic name includes the word «virus». The name of families and childbirth is written from a capital letter, specific — with lower case. The coded record in the form of the cryptogram (the text made signs) is applied to some defining properties B. that facilitates perception of properties of each V. or separate groups and their comparison among themselves.
The cryptogram consists of four couples of symbols divided by a colon, having the following value:
1. Type nucleinic to - you / number of threads.
2. Molecular weight nucleinic to - you / percentage in virion.
3. External outlines of a virion / outline of a nucleocapsid.
For expression of properties of the first couple use the following symbols: RNA — R, DNA — D, one-filamentous — 1, two-filamentous — 2.
Molecular weight is expressed in millions dalton. If nucleinic to - that is fragmented and consists of several pieces, then in case various pieces are together in one type of particles, specify the general pier. weight with a sign 2. If fragments nucleinic to - you are in various particles, then structure and a pier. weight in everyone are listed separately.
The form of virion and a nucleocapsid is designated: S — spherical; E — oblong with the parallel parties, the ends are not rounded off; U — oblong with the parallel parties and the rounded-off end (Amy); X \complex structure.
For designation of the owner use: And — actinomycetes; In — bacteria; F — mushrooms; I \invertebrates; P — pteridofita (Pteridophyte), sporous plants; S — spermaphytes; V \vertebrata; for designation of a carrier: The expert — mites and mites (Acarina, Arachnida); Al — whiteflies (Aleyrodidae, Hemiptera, Insecta); Ap — plant louses (Aphididae, Hemiptera, Insecta); Au — cycads (Auchenorrhyncha, Hemiptera); Cc — a flour scale (Coccidae, Hemiptera); Cl — bugs (Colleoptera, Insecta); Di — flies and mosquitoes (Diptera, Insecta); Fu — mushrooms (Chytridiales and Plasmodiophorales, Fungi); Gy — Merida, a piyezma, the lace maker (Gymnocerata, Hemiptera); Ne — nematodes (Nematoda); Ps — leaf hoppers (Psillidae, Hemiptera); Si — fleas (Siphonaptera, Insecta); Th — thrips (Thysanop-tera, Insecta); Ve — a carrier is unknown; About — extends without carriers; * — properties are unknown. In brackets put this doubtful or unconfirmed.
For an example we provide the cryptogram of the sort Rhabdovirus, R/1: 4/2: U/U:V,I, S/O, Ac, Ap, Di, edges is deciphered so: one-filamentous RNA-viruliferous, pier. the weight of RNA — 4 million dalton that makes 2% of weight of virion. Outside outlines of V. and a nucleocapsid — oblong with the rounded-off end. For different representatives owners are vertebrata, invertebrates, spermaphytes. Extend through the environment, and also by means of carriers of mites, plant louses, flies.
Formation of separate taxonomical groups goes depending on completeness of information and so far is on a mode of formation of childbirth and families. Offers on education of taxonomical groups and their nomenclatures proceeding from officially created groups of studying or certain scientists are considered by the relevant subcommittees and gain validity only after the statement of MKTV.
A morphogenesis of viruses
V. pass a difficult ontogenetic development cycle, strictly specific to each group B. The morphogenesis, or morfopoez, V. represents the main and most important stage of its ontogenetic development cycle which consists of a complex of the consecutive formoobrazovatelny (morphogenetic) processes leading to formation of virion — a final form of development of Century. Process of an ontogeny and V.'s reproduction is controlled by its autonomous genetic system — macromolecular DNA or RNA. The elementary V.' genome consists of 1 — 2 genes, a genome of complex DNA-containing B. — of 100 and more genes. Assembly of virions — the final stage of a morphogenesis of V., represents process of the arranged aggregation of structural virus components (macromolecules of nucleic acids, structural proteins etc.). Assembly of virions of difficult V. is regulated by so-called morphogenetic genes. The elementary V.' virions (e.g., V. of a tobacco mosaic) or separate components of complex virions form as a result of self-assembly, edges are represented by process of the spontaneous arranged molecular aggregation and is defined generally by structure of proteinaceous subunits. There is a certain dependence between degree of complexity of architecture of virions and complexity of their morphogenesis, i.e. the organization of virion is more complex, the bigger way of a differentiation passes V. in an ontogenetic development cycle and the bigger number of morphogenetic genes controls this process.
The structure of virion is a specific character of each group B. (fig. 3). - and the RNA-containing viruses or to their separate components two main types of symmetry can be inherent in DNA virions: spiral (screw — fig. 4,2 — 4) and cubic (fig. 4,2 and 5 and fig. 5 1—3). The combined type of symmetry is found in some difficult organized virions (fig. 4, 6 and 7 and fig. 5, 4 and b).
Spiral laying of macromolecules is characterized by a step of a spiral, size of screw shift, length of a spiral cylindrical particle, and also number of subunits on one turn of a spiral. If the form of proteinaceous subunits approaches the sphere, then at their spiral laying along an axis of a spiral the cavity (channel) is formed. All nucleocapsids and ribonukleoproteidny tyazh with spiral symmetry have the similar organization.
Virions with cubic type of symmetry are found in many V. of the person, animals, plants and bacteria. These virions are characterized by the size, a symmetry group, number and type of axes of rotation, number and morphology of capsomeres. The most part of virions with cubic type of symmetry is constructed as an icosahedron (icosahedron) which has axes of symmetry of the second, third and fifth orders. The cubic type of symmetry is characteristic or of all virion, or of an internal component of complex virions.
In 1967 — 1970 it was shown (A. A. Avakyan and A. F. Bykovsky) that the development cycle of each V. consists of five stages, the Crimea five forms of existence of V. correspond
Thus, the development cycle of V. can be presented as follows. Got into a sensory cell vironukleon induces formation of a polygenomic viroplast who represents a complex of the structures providing replication nucleinic to - you are V., synthesis of specific antigens, and also accumulations of these components. Viroplasta are found in a development cycle of all DNA - and many RNA-containing B. of the person and animals.
Some of them are localized in cytoplasm (V. of group of smallpox, reoviruses, enteroviruses), others — in a kernel of the infected cell (V. of group of herpes, Papova viruses, etc.). Final stage of a differentiation of a polygenomic viroplast — formation of monogenomic viroplast, each of which is an initial stage of ontogenesis of new generation of V. and includes V.'s genome, a set of specific enzymes and structural proteins. Development of a monogenomic viroplast comes to the end with synthesis (formation) of de novo of a cover V. Zatem V. (pro-virion) separates from a viroplast, and the subsequent differentiation of its structure goes in morphologically isolated from external environment (organoids of a cell) of a cavity. At the same time the strict sequence and succession of morphogenetic processes is observed.
As a result of assembly and self-assembly there is not only an increase in mass of structural components of pro-virion up to V., defined (strictly constant for each look) sizes, but also consecutive alternation of growth and a differentiation of structures to V. Po-vidimy, the end of formation of a number of structures is observed (e.g., primary cover of V. of smallpox) is the peculiar signal including the following stage of a differentiation of pro-virion. As a result of these dynamic morphogenetic processes virion — the sporous form B. providing preservation of a genome, therefore, and a type of Century is formed. After release of a genome of V. from virion the new development cycle V.
Morfogenez of the elementary RNA-containing B. begins it is possible to describe as process of self-assembly. It is characteristic not only of such simple V. as the satellite B. of a tobacco necrosis, a genome to-rogo — molecule RNA — has a pier. weight apprx. 400 000 dalton can also code only one protein, but also for V. of a tobacco mosaic, the genome to-rogo consists of 5 — 6 genes. The morphogenesis at RNA-containing B. of animals and the person which virions, except a nucleocapsid, have an external cover is more difficult (myxoviruses, oncornaviruses, an arbovirus and so forth).
Such V.' genome is polycisthrone and programs synthesis not of one-two, but many proteins, including and those which are not included into structure of virion. Synthesis of RNA of some of these V. happens in cytoplasm, others — in a kernel of a cell; synthesis of virus proteins goes only in cytoplasm on polyribosomes in a zone of a viroplast. Separate components of these V., napr, ribonukleoproteidny tyazh of myxoviruses, form in the course of self-assembly, however the composition of virion demands more complex morphogenetic processes in which submicroscopic morphology a number of consecutive stages comes to light: penetration into a cell, an intracellular morphogenesis and allocation from a cell (fig. 6 — 8).
In the course of a morphogenesis of togavirus, myxoviruses, oncornaviruses, rhabdoviruses components of membrane cellular structures (a cytoplasmatic cover, an endoplasmic reticulum, a nuclear envelope, Golgi's complex, membranes of the mitochondrions) modified in the course of an infection are a part of virions.
The morphogenesis of DNA-containing B. is also very various at different groups of these V. and depends on complexity of architecture of virion (fig. 9 and 10).
V.'s morphogenesis as well as the structure of virion, is a specific character of each group B.
Genetics of viruses of vertebrata
V.'s Gene of vertebrata can be presented by various forms of nucleic acids (see above).
In structure of a genome of V. of vertebrata, as well as other live organisms, distinguish certain sites: genes, cistrons, mutons, recons. In V.'s genomes of vertebrata it can be coded from 6 — 8 (picornaviruses) to several hundred (poksvirusa) of proteins. Attempts to construct genetic maps of V. of vertebrata did not yield positive takes yet. Only in experiences with a poliomyelitis virus it was succeeded to establish that on 51 ends of RNA genetic information on core proteins of virion is had and to define the sequence of the cistrons coding these proteins [D. Rekosh].
The properties B. which are descended are called genetic signs. Set of all hereditary information of V. defines it genotype (see). As a result of interaction of a genotype and the environment the phenotype forms, under the Crimea set of all genetic signs shown in specific conditions is understood. Among genetic signs of V. of vertebrata most often study virulence, character and the size of the plaques formed by V. on culture of fabric under an agar, character and the amount of defeats on a horionallantoisny membrane of chicken embryos, ability to breed at the changed temperature. Study also such genetic signs as the nature of cytopathic changes, productive capacity in different types of cells, ability to induce formation of interferon and sensitivity to it, ability to form plaques under special conditions (the changed concentration of soda, in the presence of a dextran and so forth), reproduction in the presence of a number of inhibitors and so forth. Study also genetic signs reflecting features of virion, napr, morphology of virion, its sedimentation constant, stability of infectivity or others biol, properties of virion to temperature, ultraviolet rays, etc., ability to adsorption on biol and chemical substances (erythrocytes, DEAE-cellulose and so forth) etc. It is supposed that the separate genetic sign of V. is connected with function of any one virusospetsifichesky protein. It is necessary to consider, however, that mutational damages to one site of a genome quite often lead to change of several genetic signs having various phenotypical display (pleiotropia). At the same time at the heart of change of the genetic sign having the same phenotypical expression (e.g., ability to breed at an elevated temperature), mutational damages of various genes can lie.
Century, as well as other organisms, are capable to change the properties as under natural conditions reproduction, and in an experiment. Two processes can be the cornerstone of hereditary change of properties B.: 1) mutation (see), i.e. the change of the sequence or structure of nucleotides in a certain site of a genome of V. conducting to phenotypical to the shown change of property; 2) recombination (see), i.e. exchange of genetic material between two relatives, but differing on hereditary properties B. As virologists investigate properties not of separate virus particles, but virus population in general, the second process — selection, i.e. emergence of conditions at which there is a preferential reproduction of virus particles to the changed heredity therefore all virus population will consist of such virions is necessary for manifestation of change of heredity of V. Frequency of mutational damages of separate genes of V. under natural conditions can vary considerably. So, the frequency of change of a u-sign (the nature of defeats on chorion-allantoisnoy to a membrane of chicken embryos) V. of smallpox of cows can reach 1: 10 2 — 1: 10 3 , while mutations on a ts-sign (temperaturochuvstvitelnost) arise very seldom (1:10 7 ). A well-known example of change of hereditary properties in the course of reproduction under natural conditions is V. of flu. It should be noted, however, that this V.'s variability is connected also with a possibility of formation under natural conditions of V.'s recombinants of flu of the person and animals recently [Webster, Leu beliefs (R. Webster, W. Laver, 1973)]. Changes of hereditary properties B. in an experiment are carried out by induction of mutations at V.'s processing by mutagens, way of a recombination, and also by means of special passages. At induction of mutations by means of mutagens use as direct processing by native V.'s mutagen or virus nucleinic to - you are in vitro, and addition of a mutagen in system, in a cut V. Chastota of emergence of mutations at V.'s processing by mutagens widely breeds varies. Changes of hereditary properties B. by special passages (long passages at usual conditions of cultivation, passages at the changed temperature, in the presence of inhibitors and so forth) as if imitate process of variability of V. under natural conditions, leading to selection of mutants, fittest to reproduction in the used conditions of passages. Cases when V.'s reproduction in a certain sensitive system leads to change of some properties B. are known, however at the subsequent reproduction of V. in other system these changes very quickly disappear. Such variability (modification) is not hereditary and is caused by inclusion in virion of some components of a host cell.
A large number of mutants of viruses of vertebrata, i.e. viruses at which as a result of mutational damage of the site of a genome a certain hereditary property changed is received. In recent years the special attention is drawn by conditionally lethal mutants which use allowed to study a number of important features of a structure of a genome and to reveal some new stages of a reproduction. Conditionally lethal mutants — mutants at which the vital protein as a result of mutational damage loses ability to function under a certain not allowing conditions, but normally carries out the function in usual conditions of a reproduction. At V. of vertebrata two types of conditionally lethal mutants are known: 1) the temperaturochuvstvitelny (ts) mutants, incapable, unlike ts + strains (wild), in the conditions of elevated temperature to form infectious virus particles, and 2) the hd-mutants, dependent on the owner, which lost ability to breed on some types of cells. Temperature-sensitive mutants are received in experiences with picornaviruses, togavirusa, myxoviruses, rhabdoviruses, retroviruses, reoviruses, Papova viruses, adenoviruses and V. of group of smallpox; hd-mutants are found in picornaviruses, V. of smallpox and a virus of herpes.
In the course of simultaneous reproduction of several virus particles in one cell between these particles there can be genetic interactions and exchange of genetic material. Several types of genetic interactions of V. of vertebrata are known. Multiple reactivation — process which takes place at infection of cells of V., partially inactivated ultraviolet rays, at plurality of an infection more than one virus a particle on a cell. As at uv radiation there is a destruction only of certain sites of a genome, the recombination of the sites of genetic material of several virus particles which got into a cell which kept a nativnost with formation of a full-fledged genome is the cornerstone of a phenomenon of multiple reactivation. Such phenomenon managed to be observed in experiences with V. of flu and V. of group of smallpox. Recombination — exchange of genetic material between the virus particles breeding in one cell differing on a nek-eye to ancestral features. Recombinants (hybrids) having a part of properties of one, and a part of properties of other parent strain are as a result formed (see. Recombination ). V.'s recombinants of vertebrata manage to be received only during the crossing of the relatives on properties B. belonging to one group. Frequency of emergence of recombinants widely varies and significantly depends on the used system (cells, a virus), and also on what hereditary property is aimed to be recombined. The recombination is with high frequency observed at RNA-containing B. (orthomyxoviruses, reoviruses, oncornaviruses) and at all DNA-containing B. which genome is presented to two-filamentous DNA. Cross-peактивация (rescue of a marker) — the phenomenon similar to a recombination, however one of the participating V. use in a native look, and inactivate another by partial destruction of genetic material (uv radiation, weak heating). By means of cross-reactivation it was succeeded to receive recombinants at V.'s crossing of flu and V. of smallpox. Heterozygosity — the phenomenon which is that at simultaneous reproduction in a cell of several particles of V. differing on hereditary properties the virions containing a full genome of one parent strain and, besides, a part of a genome (or a full genome) other V. (diploid or polyploid virions) can be formed. Though such association of genetic material in one virus particle is not inherited, it allows such virion to give posterity, in Krom a part of virus particles with properties of one, and a part — other parent will contain. The virus particles giving the described phenomenon received the name of heterozygotes, unlike usual homozygous particles which all posterity has identical properties. The phenomenon of heterozygosity is found in experiences with V. of flu and V. of the Newcastle disease. Transkapsidation — a phenomenon, at Krom a part of the alien genetic material concluded in other unrelated V.'s capsid is capable to be had in a stable form to cells, sensitive to the main V. It is observed at simultaneous cultivation in cells of adenovirus and the monkey SV40 virus, in process to-rogo a part of genetic material of the SV40 virus covalently contacts DNA of adenovirus and at the subsequent penetration of such particle into cells this site of a genome of the SV40 virus is capable to induce formation of the transforming antigen.
Viruses of invertebrates
make big group B., the striking hl. obr. representatives of a class of insects (Insecta). Recently also viral diseases of pseudoscientific mites (class Arachnoidea) and Crustacea (class Crustacea) became known. The amoeba has messages on existence of virus-like particles and parameciums (Protozoa).
Pass a complete cycle of the development in an organism of insects of V. According to uniform classification of V. of insects form seven groups, two of which have the status of a sort (Baculovirus and Iridovirus). The most extensive sort is the sort Baculovirus; virions have a bacillary form and the sizes 250 — 400 X X 40 — 70 nanometers, internal and external membranes and contain two-filamentous DNA about a pier. it is powerful apprx. 80Х10^6. V. of poliedroz forming the crystal proteinaceous inclusions, polyhedrons containing several tens of virions in cells of tissues of sick insect belong to subgroup «And» this sort. The viruses of granulez forming the granules or capsules containing one more rare two virions belong to subgroup «In». Average sizes of polyhedrons of 2 — 4 microns, average sizes of granules of 200 — 400 nanometers. Representatives of the sort Baculovirus strike the greatest number of insects from group of Lepidoptera (Lepidoptera), it is less than hymenopterous (Hymenoptera) and other groups of insects. The typical representative of this sort is V. of a poliedroz of a silkworm (Bombyx mori) leading to death of caterpillars on industrial vykorma. Idiosyncrasy of this V. is education in kernels of the struck cells of numerous hexagon polyhedrons of 3 in size — 4 microns steady against dissolution in water, to solvents of lipids, bacterial decomposition. Polyhedrons are dissolved in alkalis and acids. Symptoms of a disease: slackness of caterpillars, yellowing of covers, distension of a body, muddy and milk hemolymph. The hypoderma, an adipose body, a tracheal matrix, a hemolymph are surprised. Death of caterpillars occurs on 7 — the 8th day after infection with a lysis of all fabrics. As the representative V. of granulez V. of a granulez of a hvoyevertka, Choristoneura murinana can serve. Its idiosyncrasy is formation of numerous granules in cytoplasm of the struck cells. Symptoms of a disease and the struck fabrics are similar to poliedroza. The sort Iridovirus is presented by the «iridescent» V. which are characterized by formation of an iridescent luminescence of green-blue, violet or orange tones in the struck insect. The effect of iridescence depends on diffraction of visible light extremely correct, paracrystal packaging of virus particles. It is localized in cytoplasm of cells of an adipose body century. Virions have spherical shape with dia. 130 nanometers and the external cover consisting of 1500 capsomeres. 15% of two-filamentous DNA about a pier are a part of virions. it is powerful apprx. 140Х10 6 .
The group B. of a cytoplasma poliedroz belongs to this. Reoviridae. Virions with dia. 60 nanometers are presented by icosahedrons and contain 21 — 23% of two-filamentous RNA. They are imprisoned in large polyhedrons and are localized in cytoplasm of cells of an average gut of the struck insect. Insects from group of Lepidoptera and Neuroptera (Neuroptera) are surprised. Corpses of the died caterpillars harden, intestines get a whitish shade. The typical representative — V. of a cytoplasma poliedroz of a silkworm. This V.'s RNA has a pier. weight 12,7 — 21 X 10 6 also consists of two fragments — 12S and 15S.
To this. Poxviridae belong «entomopoksvirusa». They contain DNA, are localized in cytoplasm and have oval virions of 300 in size — 400 nanometers. Virions are put into spindle-shaped or ovoid inclusions (to 15 microns). The ridge surface of virions is characteristic. The typical representative — V. of a May cockchafer (Melolontha melolontha).
V. of a densonukleoz, or a disease of dense kernels — Densonucleosis virus Galleria is carried to the sort Parvovirus. Forms isometric particles, ikosaedralny symmetry with dia century. 21 — 23 nanometers also contain 30% of one-filamentous DNA about a pier. weighing 4 — 5Х10^6. It is described at a big bee moth (Galleria melonella), at a cut it causes paralysis and death. Formation of dense feylgenpolozhitelny masses in strongly hypertrophied kernels of an adipose body is characteristic. It is highly specific century.
One of groups B. of insects is close on properties to enteroviruses. The representative of this group is V. of acute paralysis of bees. Virions — isometric spherical particles with dia. 20 — 30 nanometers, contain one-filamentous RNA and are localized in cytoplasm of cells of an adipose body. Paralysis and death of bees come in 2 — 4 days after infection.
Century sigma of a drosophila represents group B., close to V. of vesicular stomatitis. Virions of a bacillary form with a curve on one end with dia. 70X140 nanometers, presumably RNA type. It is characterized by sensitivity of the flies struck with V., their larvae and dolls to carbonic acid. At 20 — 40% of concentration of carbonic acid in the atmosphere there comes paralysis and the death of flies. It is transovarialno transmitted century, and also through sperm.
Century of insects are eurysynusic in the nature. From 300 V. of insects apprx. 200 the others belong to V. of poliedroz and granulez — to V. which are not forming inclusions. A latent carriage of virus is characteristic. Latent V.'s activation under the influence of various stress factors leads to an epizooty among harmful and useful insects, reducing their number. Hl are surprised. obr. larval stages of insects. Infection occurs through food, the damaged covers, transovarialno. As infectious material serve corpses of the died caterpillars, the food contaminated by them, excrements, a hemolymph. Can extend sick caterpillars, wind, water, through the soil, birds century. The incubation interval depends on V.'s dose, age of caterpillars and external factors (especially temperatures). In the struck V.'s insect collects in number of 10 — 30% of the weight of fabrics. Group specificity is more often observed: one V. strikes usually close types, but some V. can strike different types, childbirth and even groups of insects. So, iridescent V. is experimentally transferred by Tipula to 7 species of flies (Diptera), And species of Lepidoptera (Lepidoptera) and 3 types of coleoptera (Coleoptera).
Thanks to considerable accumulation of V. in a body of caterpillars, formation of an epizooty and harmlessness for the person and animal V. of invertebrates are used in biol, fight against harmful insects. They are used also as extremely convenient models for a research of questions of the general virology.
Viruses of plants
On morphology of virions B. of plants concern to four groups: 1. The spiral rhabdoid V. having a rigid structure, e.g. VTM (300X18 nanometers), V. of a streated mosaic of barley (130X19 nanometers). 2. The spiral threadlike V. differing in the considerable length and elasticity of virions, e.g. H-virus of potatoes (520 X X12 of nanometer), V. of jaundice of sugar beet (1250X 10 nanometers), V. of a mosaic of a ryegrass (1725X18 nanometers). 3. Spherical or ikosaedrichesky V., e.g. V. of a necrosis of tobacco (20 nanometers), yellow mosaic of a turnip (30 nanometers). 4. The Batsillovidny or bullet V. containing membranes and an internal nucleocapsid, e.g. V. of dwarfism of corn (240X48 nanometers), yellow dwarfism of potatoes (380X75 nanometers), a mosaic of winter wheat (260X60 nanometers). The structure of rigid sticks is known only at V. of plants, the threadlike forms bearing RNA are also found only at V. of plants, spherical virions are known at bacteriophages and V. of animals, batsillovidny — at V. of animals.
The representative of the first group — VTM — has virion in the form of the rigid cylinder with sizes of 300 X 18 nanometers and a pier. weighing 39 X 106 dalton. The wall of the cylinder is formed spiralno by the laid identical proteinaceous molecules — subunits which number makes apprx. 2130. Pier. the weight of subunit apprx. 18 000 dalton. Spiral turns densely adjoin to each other and each of them includes 161/3 subunits.
Tyazh virus RNA, the pier consisting approximately of 6400 nucleotides and having. weight 2Х10 6 dalton, passes between ranks of proteinaceous subunits, following their spiral arrangement, at distance of 4 nanometers from the center of cross-section of a particle. At such arrangement one proteinaceous subunit is the share of each three nucleotides of a tyazh of RNA. In the cylinder, on all its length, there passes the cavity with dia. 4 nanometers. Virus RNA is protected by protein from action of cellular nucleases, but low-molecular substances, including mutagens, can get into the area of localization of RNA, having on it the inactivating or mutagen effect. In experimental conditions some rhabdoid and spherical V.' virions of plants managed to be disaggregated on proteinaceous subunits and RNA with preservation of their native state and then again to cause aggregation of these components with recovery of structure, infectivity and other properties of virions.
At V.'s most of plants the genome is presented to odnotyazhny RNA, but V. of wound tumors of plants and dwarfism of rice have dvutyazhny RNA. DNA is found only at a spherical virus of a mosaic of a cauliflower so far. V. of plants which RNA genome is fragmented are known, each of fragments bears a part of genetic information and is put into a separate capsid. Only the joint action of all fragments provides functions of a full genome. Activators of a pogremkovost of tobacco, a mosaic of a lucerne, etc. belong to such V. of plants. At some V. of plants the genome is so small that does not provide replication of virus RNA. So, at the satellite B. of a necrosis of tobacco a pier. the weight of RNA makes only 0,4х10^6 dalton, he induces synthesis of own shell protein, but has no cistron of a sintetaza and parasitizes at the expense of unrelated V. of a necrosis of tobacco, using its sintetaza.
Century of plants get into cells of plants in the way pinocytic (see) at the damages baring sites of a plasma membrane. In the nature they extend hl. obr. the sucking insects, mites, nematodes and zoospores of some lowest mushrooms — root parasites. V. of plants breeding in an organism of insects carriers are known, part of them is transmitted to posterity of carriers through egg. Some V. extend seeds of sick plants. Vegetative reproduction of plants especially promotes distribution of Century.
Intracellular development of V. of plants follows the same patterns what are known for a reproduction of RNA-containing B. in general. Many V. of plants form in cells the crystal inclusions consisting of virions, and the amorphous, containing V. and components of cytoplasm. The diseases of plants caused by V. chronic, recovery does not occur. Intensive reproduction of V. happens in the growing leaves and other bodies. In a meristem of an apical point of V. it is a little, in its apical part it can be absent, reception of sterile cultivation of healthy plants from pieces of a meristem is based on it. Some V. are inactivated in the infected plants at thermal treatment. The chemotherapy against V. of plants is not developed.
One V. strike plants of many types, others are narrowly specialized. VTM, e.g., in pilot conditions is capable to infect plants of many types like floral, several types of type pteroid, he infects protoplasts of yeast, and its RNA is replicated and in vitro even in the fraction of mitochondrions isolated from cells of a liver of a rat is broadcast.
Table. CLASSIFICATION of VIRUSES according to 1975
CLASSIFICATION of VIRUSES of the PERSON AND ANIMALS (according to the International committee on taxonomy of viruses, 1982)
(From additional materials)
Due to the emergence of new data on structural, biological and other properties of viruses also nek-ry ideas of their classification changed. Fundamental properties of virions — type of nucleic acid (see) a genome, morphology, antigenic properties, a way of replication (see) a genome, etc. are the basis for the carried-out classification. The way of replication is determined by V.'s ability to induce formation of polymerases in a cell or on the maintenance of polymerases as a part of virion. Small RNA-genomic picornaviruses (see. Intestinal viruses) and togavirusa (see) induce formation of RNA RNA-dependent - poly-meraz; reoviruses (see), orthomyxoviruses (see), paramyxoviruses (see), rhabdoviruses (see), arenovirusa (see), bunjyavirusa (see t. 25, additional materials) and coronaviruses (see) contain P N K - for in is and m at yu RNA - on l Yim Ra z at.
Idiosyncrasy of retroviruses is existence RNK-za-visimoy of a DNA polymerase (reverta-za). DNA-genomic parvoviruses (see), Papova viruses (see), adenoviruses (see) and viruses of herpes (see Herpes viruses) induce a DNA-dependent DNA polymerase. Poksvirusa (see) induce a DNA-dependent DNA polymerase and bear as a part of DNA-dependent virion of the RNK-polimera-zu.
Taxonomical groups of viruses are united in families. Creation of higher degrees of hierarchy (classes, groups, types) is interfered by a lack of knowledge of evolution of viruses. Phylogenetic bonds are traced at the level of childbirth, sometimes families, data on bonds between families are absent.
The international committee on taxonomy of viruses made the decision to stop use of cryptograms for the coded record of the defining properties of viruses in 1978. Binomial names of types of distribution did not receive since for viruses accurate criteria of the concept «look» are not elaborated yet.
17 families DNK-genom-nykh of viruses and 42 families RNK-ge-nomnykh of viruses are known. 6 DNA-genomic families of viruses and 12 RNA-genomic families of viruses are presented in the table, to-rye include the viruses of vertebrata important in medicine and veterinary science. Further improvement of classification assumes division of nek-ry families. So, e.g., allocation of the sort Flavivirus from this is prepared. Togaviridae in independent this. Flaviviridae with the standard sort Flavivirus and type-species — a virus of a dengue of the 2nd type (see the Dengue). Many viruses, important for pathology of the person, remain not classified. Among them there is a virus of hepatitis B, to-ry together with similar
viruses of animals (viruses of forest groundhogs, Beijing ducks and cape ground squirrels) is included in group of Hepadna-viruses. Special family, apparently, viruses will make Marburg (see Tserkopitekovaya hemorrhagic fever) and Ebola (see Ebola hemorrhagic fever). Not clearly systematic position of agents fasten (diseases of sheep), activators the Kura (see) and Kreyttsfeldt's diseases — Jacoba (see Kreytts-feljdt — Jacoba a disease), a virus of a disease of Bourne of horses, the agent of a rozeolezny disease of teenagers.
CLASSIFICATION of VIRUSES of the PERSON AND ANIMALS (according to the International committee on taxonomy of viruses, 1982)
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T. I. Tikhonenko; A. P. Bykovsky (morphogenesis), S. Ya. Gaydamovich (classification), BB. 3. Gendonum (geneticist V. of vertebrata), T. S. Sukhov (V. of plants), L. M. Tarasevich (V. of invertebrates), S. Ya. Gaydamovich.