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At least 55 records · Page 3Linked to original sources
PubMed1963

A CLASSIFICATION OF VIRUS PARTICLES BASED ON MORPHOLOGY.

Recent improvements in electron microscope techniques which allow the study of virus fine structure have permitted the grouping of many viruses on a purely morphological basis. Briefly the techniques used in electron microscopy for the study of viruses are reviewed and the symmetry properties of virus particles as revealed by negative staining are discussed somewhat more fully.Finally, virus particles are grouped on two bases, firstly the site of formation of the virus within the cell as seen by thin sectioning techniques, and secondly the symmetry property of the virus as seen by negative staining. Consideration of the groupings obtained in this way reveals that the biochemical and physical properties of a virus can be deduced from the readily established morphological characteristics.

Classification↗
PubMed1995

Identification and classification of viruses that have not been propagated.

Microorganisms that cannot be grown in the laboratory can now be tentatively identified, by cloning and sequencing particular nucleic acid segments and then carrying out a comparative sequence analysis with an appropriate database. For bacteria, a few universally distributed genes and gene products have enabled comparative sequence analysis to be used for tentative identification and classification of uncultured bacteria. For viruses, there is no universally distributed viral gene or gene product. However, in a few cases, viruses that could not be propagated in the laboratory have been identified and classified. In these cases, either the entire viral genome sequence was determined or partial sequence information was supplemented with additional data. The Executive Committee of the International Committee on Taxonomy of Viruses (ICTV) has reviewed the issue of identification and classification of viruses that have not been propagated. Under the ICTV system, formal review of any taxonomic proposal is carried out by the relevant ICTV Subcommittee or Study Group. The few examples of unpropagated viruses that have arisen thus far have been readily accommodated within existing viral taxonomy, with the international group of experts comprising each Subcommittee and Study Group determining the necessary and sufficient amount of information needed for classification of an unpropagated virus on a case-by-case basis.

Bacteria↗
PubMed1996

Present status of classification of viruses of vertebrates.

The VIth Report of the International Committee on Taxonomy of Viruses (ICTV) was published in 1995. We have briefly characterized its contents and discussed the most important changes that have been made in the classification of viruses of vertebrates. The present line up of families and genera of viruses of vertebrates, and subviral agents and unassigned viruses is also provided. We propose an allocation of families of viruses of vertebrates according to a conjectural evolutional connection between the type and class of genomic nucleic acid. Finally the directions and intentions of the ICTV have been reviewed from the Virology Division News in Archives of Virology (1994/1995). These will be considered in the VIIth Report of the ICTV scheduled for publication after the XIth International Congress of Virology in Sydney in 1999.

Animals↗
PubMedDate not supplied

[Design of an algorithm for the numerical classification of viruses].

The data are presented dealing with the construction of algorithm of numerical classification of RNA- and DNA-containing viruses of vertebrates. The possibility of using of a limited number of parameters with certain coefficients was demonstrated. Suitable parameters for this purpose were elucidated and coefficients (weights) for them determined.

Computers↗
PubMed1995

Relationships between serotypes and genotypes of hepatitis B virus: genetic classification of HBV by use of surface genes.

Hepatitis B virus (HBV) surface antigen (HBsAg), which is encoded by the HBV S gene, is conventionally classified into 4 serological subtypes, adw, adr, ayw and ayr. To determine the relationship between the HBsAg seroreactivity and the nucleotide sequence diversity of the HBV S gene, the nucleotide sequences of S genes for HBV isolates reported so far were aligned with each other. The numbers of nucleotide substitutions were then estimated by the 6-parameter method, and a phylogenetic tree was constructed by the unweighted paired grouping method with arithmetic mean (UPGMA) and the neighboring-joining (NJ) method. The phylogenetic trees constructed showed that all isolates were grouped into 4 genotypes (gyw, gdw-1, gdw-2, and gdr). More importantly, the genotypes did not necessarily correspond to the conventional serotypes. In particular, serotype 'adw' can be any of genotypes gdw-1, gdw-2, or gdr. Thus, genotyping by S genes gives more accurate information about genetic variation of HBV.

Amino Acid Sequence↗
PubMed1997

Genotype of GB virus C/hepatitis G virus by molecular evolutionary analysis.

GB virus C/hepatitis G virus is a newly described virus. Classification of GB virus C/hepatitis G virus into genotypes has not been established. We analyzed nucleotide sequences within the 5' untranslated region of GB virus C/hepatitis G virus isolates and segregated these isolates into genotypes. Twenty serum samples with GB virus C/hepatitis G virus RNA from Australia, Cameroon, the Congo, Japan, Mongolia, and Bangladesh were studied. Reverse transcription and polymerase chain reaction were used to obtain GB virus C/hepatitis G virus RNA. After nucleotide sequences from the 5' untranslated region were determined, 68 nucleotide sequences, including 48 previously reported sequences, were analyzed by molecular evolutionary methods. The phylogenetic tree of the 5' untranslated region showed that all strains could be divided into three major genotypes, GB type (type 1), HG type (type 2), and Asian type (type 3). Bootstrap analysis indicated that the strains could be divided into three major genotypes but could not be further subdivided. Moreover, frequency histograms of pairwise distances between nucleotide sequences demonstrated only one peak. These result indicated that GB virus C/hepatitis G virus can be classified into three major genotypes, GB type (type 1), HG type (type 2), and Asian type (type 3), and should not be divided into minor subtypes.

Base Sequence↗
PubMed1992

[Classification and virus expression of primary cerebral lymphomas].

Fourty-three primary cerebral lymphomas (PCL) were histologically classified and examined for genome expression of Epstein Barr Virus (EBV) and human herpes virus 6 (HHV6) using dot blotting, polymerase chain reaction, and Southern blotting. Only 20 tumors (16 high grade and 4 low grade lymphomas) could be suitably placed into a category of the Updated Kiel Classification, whereas the non-classified 23 tumors were highly malignant B-lymphomas and referred to as small-cell (SC) or large-cell (LC) blastic PCL. Most of the LC PCL showed a tumor-like infiltration pattern with high cellular density and little remaining parenchyma, whereas the SC PCL more often showed an inflammation-like pattern characterized by loose arrangement of tumor cells and marked astrocytic, microglial and T-lymphocytic reaction. EBV genome was found in 3/3 AIDS cases, but in none of 40 immunocompetent cases, while HHV6 was detected in 2 tumors of immunocompetent patients. We conclude that (1) the Updated Kiel Classification is not applicable to a majority of PCL, and (2) EBV and HHV6 do not appear to play a major role in the pathogenesis of PCL in immunocompetent subjects.

Autopsy↗
PubMed1975

A classification of virus groups based on the size of the particle in relation to genome size.

For 59 different viruses, when the amount of nucleic acid in the particle is related either to the dry weight of the particle or to the particle volume, two classes of virus groups emerge--those with enveloped or those with geometrical particles. The enveloped viruses have particles with the following properties: (i) about 40 X 10-6 daltons of anhydrous weight per 10-6 daltons of nucleic acid; (ii) a particle volume of about 2 X 10-5 nm3 per 10-6 daltons of nucleic acid; (iii) a limiting lipoprotein membrane. These properties are qualitatively and quantitatively close to those of prokaryotic cells. The geometric viruses have particles with roughly one-tenth the anhydrous mass per unit of nucleic acid and one twenty-fifth the particle volume per unit of nucleic acid. They do not possess a limiting lipoprotein membrane.

Classification↗
PubMed2003

The classification of viruses infecting the respiratory tract.

Following the boom in respiratory virology in the 1960s, species of rhinoviruses, coronaviruses, enteroviruses, adenoviruses, parainfluenza viruses and respiratory syncytial virus were added to influenza and measles viruses as causes of respiratory tract infection. In restricted patient groups, such as the immunocompromised, members of the family of herpesviruses including herpes simplex, cytomegalovirus, varicella-zoster virus, Epstein-Barr virus and human herpes virus 6 have also been associated with respiratory disease. This list of pathogens was extended last year with the discovery of a novel virus, the human metapneumovirus. More than 200 antigenically distinct viruses have been documented as causes of sporadic or epidemic respiratory infections in infants, children and adults. However, this varied and diverse group can be divided among six distinct families. Understanding some of the basic biology of these families gives an insight into possible strategies for diagnosis, control and therapy.

Adenoviridae↗