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At least 451 records · Page 25Linked to original sources
PubMed1998

Viruses infecting marine brown algae.

Viruses infecting algal hosts possess large double-stranded DNA as genomes. We have recently identified a family of viruses specific for filamentous brown algae. In contrast to the better known Chlorella viruses with their lytic infection cycle, marine brown algal viruses latently occur in their host cells and are induced to multiply in response to a variety of external stimuli such as change in light and temperature. Here, I summarize the known properties of this family of viruses and discuss their taxonomic classification.

DNA Viruses↗
PubMed1993

Hepatitis viruses and protection against infection in children.

Molecular biology techniques are now a vital part of hepatitis virology, with a central role in studies of diagnosis, epidemiology, virology, pathogenesis, and natural history of infection. Cloning of the genome of hepatitis E virus has allowed its tentative classification as a calici- or related virus, and is the first step toward the development of a vaccine. Long-term implications of hepatitis C for groups such as children with hemophilia, thalassemia, and even leukemia can be better understood by comparison of virus load measured by molecular amplification of the plasma viral RNA with the serologic and clinical status of the respective cohorts of children. A new vaccine for hepatitis A has been licensed in several European countries, and recent experience with severe hepatitis in infants after unexpected transmission of hepatitis B from anti-hepatitis B e positive mothers reemphasizes the value of universal hepatitis B immunization programs. Mother-to-infant transmission of hepatitis C virus has now been well documented, but there are still insufficient data on the dynamics of this, particularly in the absence of passive immunoprophylaxis or a vaccine, to permit recommendations regarding the management of individual pregnancies or deliveries. There is especially too little information to suggest whether breast feeding may be an important mechanism for transmission.

Base Sequence↗
PubMed2005

International Committee on Taxonomy of Viruses and the 3,142 unassigned species.

In 2005, ICTV (International Committee on Taxonomy of Viruses), the official body of the Virology Division of the International Union of Microbiological Societies responsible for naming and classifying viruses, will publish its latest report, the state of the art in virus nomenclature and taxonomy. The book lists more than 6,000 viruses classified in 1,950 species and in more than 391 different higher taxa. However, GenBank contains a staggering additional 3,142 "species" unaccounted for by the ICTV report. This paper reviews the reasons for such a situation and suggests what might be done in the near future to remedy this problem, particularly in light of the potential for a ten-fold increase in virus sequencing in the coming years that would generate many unclassified viruses. A number of changes could be made both at ICTV and GenBank to better handle virus taxonomy and classification in the future.

Advisory Committees↗
PubMed1993

Predicting the outcomes of human immunodeficiency virus infection. How well are we doing.

An important determinant of patient outcomes is illness severity, which must be classified to guide clinical decision making and evaluate the effectiveness of diagnostic and therapeutic interventions. Currently, no widely accepted framework for grading illness severity in human immunodeficiency virus-infected patients exists. The best known classification systems for human immunodeficiency virus infection (Centers for Disease Control and Prevention; Walter Reed) are not based on illness severity, and provide stages that are not all inclusive so that a large number of persons cannot be classified (Walter Reed). Although much previous research has focused on individual prognostic factors (oral thrush, CD4 cell count, serum beta 2-microglobulin), little attention has been given to incorporating these factors into illness severity scales that are easy to use in clinical settings. In addition, despite the progressive functional disability of human immunodeficiency virus-infected individuals, few of the existing approaches to illness severity classification have examined the contribution of functional status. We urge investigators to develop clinically sensible severity scales that are easy to use. Such scales will considerably improve existing approaches that tend to rely solely on the CD4 cell count and do not take into account the known prognostic effects of other variables.

Acquired Immunodeficiency Syndrome↗
PubMed1988

The surveillance definition of the acquired immunodeficiency syndrome and the clinical classification of infection with the human immunodeficiency virus type 1.

In 1982, one year after the first cases of the acquired immunodeficiency syndrome (AIDS) were reported, a case definition of AIDS was produced by the Centers for Disease Control, Atlanta, Georgia, USA. This definition was implemented world-wide, and it allowed the standardization of the reporting of cases. The identification of the virus that is responsible for AIDS, which subsequently was named the human immunodeficiency virus type 1 (HIV-1), led to the development of laboratory test procedures to detect its presence. The use of these tests confirmed that additional clinical manifestations were associated with severe outcomes of HIV-1 infection, which resulted in an increase in the number of conditions that were encompassed by AIDS. Moreover, the diagnosis of many AIDS-defining conditions could be made presumptively in the presence of proved HIV-1 infection. Thus the case definition required revision in 1985, and again in 1987. In addition, clinical expressions other than AIDS definitively were attributed to infection with HIV-1 after the widespread use of the testing procedures. The case definition of AIDS, as revised by the Centers for Disease Control in 1987, now is the current definition that is used in Australia. The clinical classification of HIV infection, which was produced by the Centers for Disease Control in 1986, was implemented in this country in January 1988.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

[Mobility study of influenza C virus proteins in cellulose acetate electrophoresis].

Four strains of influenza C virus were studied by cellulose acetate electrophoresis. All of them were found to contain super-capsid proteins destroyed by electrophoresis apparently due to contact with sodium dodecylsulphate. According to Laver's classification, influenza C viruses may be placed with Group 3 viruses. Among major virion proteins of influenza C viruses matrix protein was found to be the most stable forming a separate protein band on cellulose acetate, and it may be readily identified and eluted from paper in preparative amounts.

Electrophoresis, Cellulose Acetate↗
PubMed1985

Markers of Venezuelan encephalitis virus which distinguish enzootic strains of subtype I-D from those of I-E.

Strains of Venezuelan encephalitis virus isolated from enzootic habitats during interepizootic periods in Middle America and northern South America can be distinguished from each other antigenically by hemagglutination inhibition. This test has provided the basis for the classification of these virus strains into subtypes I-E and I-D, respectively. Virus strains of these two subtypes have been found to differ profoundly with respect to virulence for English short hair guinea pigs. Studies are described which confirm that virus strains of the I-D subtype are guinea pig virulent, and that virulence is not the result of cocycling subpopulations of epizootic subtype I-AB or I-C virions. Two additional markers were found which distinguish subtype I-D and I-E Venezuelan encephalitis virus strains. Firstly, hydroxylapatite chromatography of intact virions at pH 6.5 showed differential elution of I-D and I-E prototype strains. Virions of subtype I-D strains eluted at 0.08 to 0.11 M phosphate, while those of subtype I-E strains eluted at 0.15 to 0.20 M phosphate. Secondly, the isoelectric points of the E1 envelope glycoproteins of the I-D and I-E prototype strains were significantly different; pH 6.85 to 7.00 and pH 7.25 to 7.30, respectively. There was no significant difference in the isoelectric points of the E2 envelope glycoproteins. These distinguishing characteristics most likely reflect a fundamental difference in virion surface structure.

Animals↗
PubMed1990

Differentiation of respiratory syncytial virus subgroups with cDNA probes in a nucleic acid hybridization assay.

A new approach to respiratory syncytial (RS) virus subgroup determination was developed by using a simple nucleic acid filter hybridization technique. By this method, virus-infected cells are bound and fixed in a single step, and the viral RNA in the fixed-cell preparation is characterized directly by its ability to hybridize to cDNA probes specific for either the A or B subgroups of RS virus. The subgroup-specific probes were constructed from cDNA clones that corresponded to a portion of the extracellular domain of the RS virus G protein of either a subgroup B RS virus (8/60) or a subgroup A RS virus (A2). The cDNA probes were labeled with 32P and used to analyze RS virus isolates collected over a period of three decades. Replicate templates of infected cell preparations were hybridized with either the subgroup A or B probe. The subgroup assignments of 40 viruses tested by nucleic acid hybridization were in agreement with the results of subgroup determinations based on their reactivities with monoclonal antibodies, which previously has been the only method available for determining the subgroup classification of RS virus isolates. The nucleic acid hybridization assay has the advantage of providing broad-based discrimination of the two subgroups on the basis of nucleic acid homology, irrespective of minor antigenic differences that are detected in assays in which monoclonal antibodies are used. The nucleic acid hybridization technique provides a reliable method for RS virus subgroup characterization.

Antibodies, Monoclonal↗
PubMed1971

Purification, morphology and partial characterization of a reovirus-like agent associated with neonatal calf diarrhea.

Studies have been conducted on a virus which has recently been implicated as an etiological agent in widely disseminated cases of calf diarrhea. The virus was isolated from feces and intestinal mucosa from experimentally infected calves and from cell cultures which had been inoculated with material from infected calves. The virus was purified by differential centrifugation, nuclease treatment, extraction with Genetron 113 and cesium chloride (CsC1) gradient. Purified and non-purified samples were studied by electron microscopy. Both types of preparations contained unenveloped particles approximately 64 nm in diameter with a hexagonal core region 36 nm in diameter. Subunits of the capsids appeared to be arranged in accordance with cubic synmetry. Essential lipids were not associated with the virus. The buoyant density of purified virus was 1.359. Viral nucleic acid was determined by chemical methods to be ribonucleic acid (RNA). The morphology and some chemical characteristics appear to be similar to those of the reovirus group. However, the exact classification of this virus and its relationship to other groups remains to be established.

Animals↗
PubMed1988

Flanders virus replication and protein synthesis.

The prototype strain of Flanders virus (61-7484) has been adapted to grow in Vero cell cultures and a plaque assay has been developed. Electron micrographs of infected cells revealed rod-shaped virions budding in clusters from the plasma membrane, consistent with the tentative classification of Flanders virus as a member of the Rhabdoviridae. Viral proteins were identified by SDS-PAGE and immunological techniques using Flanders virus-specific antibodies. Eight virus-associated proteins were detected. The relative molecular weights obtained by SDS-PAGE were 180,000, 81,000, 54,000, 43,000, 33,000, 27,000, 23,000, and 19,000. Evidence is presented that two of these proteins (43,000 and 23,000 mol wt) are in vivo cleavage products. The 81,000 mol wt protein was glycosylated and phosphorylated and did not label well with [35S]methionine or 14C-amino acids. The 54,000 and 33,000 mol wt proteins were phosphorylated. When 35S-radiolabeled virus was purified by pelleting at 90,000 g followed by isopycnic sucrose gradient centrifugation, all eight virus proteins were present in the peak fractions which contained the radiolabel and infectivity.

Animals↗
PubMed1989

Glycoprotein evolution of vesicular stomatitis virus New Jersey.

A T1 ribonuclease fingerprinting study of a large number of virus isolates had previously demonstrated that considerable genetic variability existed among natural isolates of the vesicular stomatitis virus (VSV) New Jersey (NJ) serotype [S.T. Nichol (1988) J. Virol. 62, 572-579]. Based on these results, 34 virus isolates were chosen as representing the extent of genetic diversity within the VSV NJ serotype. We report the entire glycoprotein (G) gene nucleotide sequence and the deduced amino acid sequence for each of these viruses. Up to 19.8% G gene sequence differences could be seen among NJ serotype isolates. Analysis of the distribution of nucleotide substitutions relative to nucleotide codon position revealed that third position changes were distributed randomly throughout the gene. Third base changes constituted 84% of the observed nucleotide substitutions and affected 89% of the third base positions located in the G gene. Only three short oligonucleotide stretches of complete sequence conservation were observed. The remaining nucleotide changes located in the first and second positions were not distributed randomly, indicating that most of the amino acids coded by the G gene cannot be altered without reducing the fitness of the VSV NJ serotype viruses. Despite these constraints, up to 8.5% amino acid differences were observed between virus isolates. These differences were located throughout the G protein including regions adjacent to defined major antibody neutralization epitopes. Apparent clusters of amino acid substitutions were present in the hydrophobic signal sequence, transmembrane domain, and within the cytoplasmic domain of the G protein. A maximum parsimony analysis of the G gene nucleotide sequences allowed construction of a phylogram indicating the evolutionary relationship of these viruses. The VSV NJ serotype appears to contain at least three distinct lineages or subtypes. All recent virus isolates from the United States and Mexico are within subtype I and appear to have evolved from an ancestor more closely related to the Hazelhurst historic strain than other older strains. The implications of these findings for the evolution, epizootiology, and classification of these viruses are discussed.

Amino Acid Sequence↗
PubMed1997

Evaluation of a bulk-milk ELISA test for the classification of herd-level bovine leukemia virus status.

The results of a commercial bulk-milk enzyme-linked immunosorbent assay (ELISA) test for herd-level bovine leukemia virus (BLV) status were compared to results obtained from individual agar-gel immunodiffussion (AGID) testing on sampled cattle. A positive herd was defined as a herd having one or more AGID-positive animals. The estimated true herd status was based on the sensitivity and specificity of the AGID test and the number of cattle sampled per herd. Ninety-seven herds were used, with a mean of 13 cows sampled per herd. The AGID test indicated an apparent herd prevalence of 70.1%. After accounting for the number of cows sampled and the sensitivity and specificity of the AGID test, the estimated true herd prevalence of BLV was 52.3%. The ELISA test identified 79.4% of herds as positive for BLV, and had an apparent sensitivity and specificity of 0.97 and 0.62, respectively. However, after accounting for the sensitivity and specificity of the AGID test in individual animals, the specificity of the ELISA test was 0.44. The ELISA test was useful for identifying BLV-negative herds (i.e., ruling out the presence of BLV infection in test negative herds). With the moderately low specificity, herds identified as positive by the ELISA test would require further testing at the individual or herd level to definitively establish their BLV status.

Animals↗
PubMed2025

Whole genome sequencing and phylogenetic classification accelerate the implementation of respiratory syncytial virus genomic surveillance in Canada: a pilot study.

UNLABELLED: Whole genome sequencing (WGS) has emerged as a powerful tool to facilitate the study of existing and emerging infectious diseases. WGS-based genomic surveillance provides information on the genetic diversity and tracks the evolution of important viral pathogens, including respiratory syncytial virus (RSV). Multiplex tiling polymerase chain reaction (PCR) assays have been used to facilitate sequencing of a variety of pathogens in support of genomics-based surveillance initiatives. We developed, optimized, and implemented multiplex tiling PCR assays for RSVA and RSVB capable of generating near-complete genomes in the majority of contemporaneous specimens tested. A pilot data set comprising 52 RSVA and 37 RSVB genomes derived from Canadian clinical specimens during the 2022-2023 respiratory virus season was used to perform phylogenetic analyses using both near-complete genome and glycoprotein (G) sequences. Overall, the RSV phylogenetic tree built with whole genomes showed identical lineage clusters as compared to the G gene but was more discriminatory. Moreover, the availability of complete genomes enables the identification of a broader range of mutations. For instance, mutations identified in the fusion protein among Canadian isolates tested here, including S377N, K272M, S276N, S211N, S206I, and S209Q, could affect the efficacy of current vaccines or antiviral-based therapeutics. In conclusion, our work reinforces other recent studies demonstrating the utility of multiplex tiling PCR assays to facilitate high-throughput WGS of RSV, which is capable of supporting enhanced genomic surveillance initiatives, as well as the more comprehensive genomic analyses required to inform public health strategies for the development and usage of vaccines and antiviral drugs. IMPORTANCE: We present assays to efficiently sequence genomes of RSVA and RSVB. This enables researchers and public health agencies to acquire high-quality genomic data using rapid and cost-effective approaches. Genomic data-based comparative analysis can be used to conduct surveillance and monitor circulating isolates for efficacy of vaccines and antiviral therapeutics.

Humans↗
PubMed2002

The classification of seven serotypes of equine encephalosis virus and the prevalence of homologous antibody in horses in South Africa.

Selected isolates of equine encephalosis virus were shown to have comparable viral protein profiles and to represent seven distinct serotypes, based on cross-neutralization tests. Serotype-specific virus-neutralizing antibody in serum samples from horses confirmed the widespread occurrence of infection. The distribution and prevalence of individual serotypes however, varied considerably. Localised foci with an increased seasonal seroconversion in groups of horses to a specific serotype and the detection of an ongoing low level of infection from other serotypes within the population, confirmed the independent persistence of the viruses in a maintenance cycle. The identification of donors with antibody resulting from infection with multiple serotypes indicated a low level of cross-protection in horses to natural reinfection.

Animals↗