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At least 109 records · Page 6Linked to original sources
PubMed1995

Determination of three-dimensional low-resolution viral structure from solution x-ray scattering data.

The capsid is modeled as a region of constant electron density located between inner and outer envelopes that exhibit icosahedral symmetry. For computational purposes the envelopes are represented as truncated sums of weighted icosahedral harmonics. Methods are described for estimating the weights from x-ray solution scattering patterns based on nonlinear least squares, and two examples of the procedure, for viruses with known atomic-resolution structures, are given.

Biophysical Phenomena↗
PubMed2003

Prevalence of human erythrovirus B19 DNA in healthy Belgian blood donors and correlation with specific antibodies against structural and non-structural viral proteins.

BACKGROUND AND OBJECTIVES: Human parvovirus (erythrovirus) B19 is recognized as a major contaminant of blood and blood products. To reduce the risk of contamination, plasma-pool screening and exclusion of highly viraemic donations are recommended. The objectives of this study were to estimate the prevalence of B19 DNA in our blood-donor population, to determine the appropriate pool size to be tested (taking into account parameters such as prevalence, viral load, test sensitivity, and the efficacy of inactivation procedures), and to correlate viral loads with the serological status of donors as regards antibodies against different viral proteins. MATERIALS AND METHODS: Pools of different sizes were tested for B19, using a sensitive nested polymerase chain reaction (PCR) as well as an simple, un-nested, less sensitive PCR. Positive pools were resolved to the level of individual donations, and the viral load and serological markers were determined. RESULTS: Of 16,859 donations, 27 (one of 625) were found to be B19 DNA positive, with viral loads ranging from 10(2) to > 10(7) IU/ml. Twenty-five of the positive donations were tested for VP-specific anti-B19 antibodies, and eight (32%) were negative for both immunoglobulin (Ig)M and IgG. They were probably collected in the preseroconversion window period or from chronic carriers without detectable antibodies. We regarded the seven (28%) IgM-positive donors as being in the early phase of infection. The remaining 10 (40%) IgM-negative, IgG-positive donors were probably carriers of persistent infection (i.e. PCR positive despite the presence of IgG antibodies), as suggested by their low viral loads (< 10(4) IU/ml). Fifteen out of 36 major pools contained one or more contaminated donations. Among these, 12 tested positive by nested PCR and only three by un-nested PCR, this reflecting a viral load of > 10(4) IU/ml. CONCLUSIONS: By testing all donations as pools of 480 by un-nested PCR, and resolving positive pools to identify the responsible donations, it is possible to ensure that the viral load in fractionation pools (5000 donations) remains < 10(3) IU/ml, compatible with the efficacy of inactivation procedures and complying with Food and Drug Administration (FDA) recommendations.

Algorithms↗
PubMed1991

[Effect of viral structure and replication characteristics on the pathogenesis of infectious bursal disease].

Infectious bursal disease (IBD) is a highly contagious disease of young chickens, which occurs world-wide, and is responsible for severe losses in poultry industries. In birds surviving an acute infection, lymphoid cells in the bursa of Fabricius are destroyed, resulting in B-cell-dependent immunodeficiency. This causes increased susceptibility to diseases by otherwise harmless agents. The decisive role in the pathogenesis of IBD is played by the bursa, representing the target organ of the aetiological agent, infectious bursal disease virus (IBDV). By adaptation of IBDV to chicken embryo cells, we obtained several variants of a pathogenic wild type strain. These variants had altered abilities for replication in actively dividing B lymphocytes and, consequently, had altered pathogenic properties. An IBDV isolate from turkeys, non-pathogenic for chickens, was used to create reassortant virus strains. The virological and the biological characterization of these IBDV variants is reported.

Animals↗
PubMed1998

Effect of major deletions in the V1 and V2 loops of a macrophage-tropic HIV type 1 isolate on viral envelope structure, cell entry, and replication.

Two HIV-1 envelope mutant proteins were generated by introducing deletions in the first and second hypervariable gp120 regions (V1 and V2 loops, respectively) of a macrophage-tropic primary HIV-1 isolate, SF162, to study the effect of the deleted sequences on envelope structure, viral entry, and replication potentials. The first mutant lacked 17 amino acids of the V1 loop and the latter 30 amino acids of the V2 loop. A comparison of the immunochemical structure of the wild-type and mutant monomeric and virion-associated gp120 molecules revealed that the V1 and V2 loop deletions differentially altered the structure of the V3 loop, the CD4-binding site, and epitopes within conserved regions of gp120. Regardless of differences in structure, both mutated envelope proteins supported viral replication into peripheral blood mononuclear cells to levels comparable to those of the wild-type SF162 virus. However, they decreased the viral replication potential in macrophages, even though they did not alter the coreceptor usage of the viruses. These studies support and extend previous observations that a complex structural interaction between the V1, V2, and V3 loops and elements of the CD4-binding site of gp120 controls entry of virus into cells. The present studies, however, suggest that the effect of the V1 and V2 loops in viral entry is cell dependent.

Amino Acid Sequence↗
PubMed1989

Modification of foot-and-mouth disease virus after serial passages in the presence of antiviral polyclonal sera.

Foot-and-mouth disease virus (FMDV) shows a remarkable antigenic variability. Like other RNA viruses, this virus has a high rate of mutation. It has been proposed that selection exerted by the host's antibodies could play a major role in the rapid evolution of FMDV. The present work reports the selection of FMDV antibody-resistant populations (Nr), after serial passages of cloned FMDV A24 Cruzeiro strain on secondary monolayers of bovine fetal kidney cells in the presence of subneutralizing antiviral polyclonal sera (APS). After a limited number of passages under selective pressure, the virus population showed the following characteristics: (1) increased resistance to neutralization by APS; (2) altered electrophoretic mobility of structural viral proteins (VP1); (3) remarkable plaque size reduction, (4) a pronounced thermosensitivity (ts); and (5) decreased pathogenicity for mice, in both uncloned and cloned small plaque size populations. This indicates that FMDV populations under antibody pressure in vitro, have acquired, in addition to expected characteristics of natural FMDV variants (resistance to neutralization and altered viral structural proteins), phenotypic markers which correspond to attenuated, less virulent variants.

Antibodies, Viral↗
PubMed1987

Purification of papillomavirus structural polypeptides from papillomas by immunoaffinity chromatography.

A broadly cross-reactive monoclonal antibody directed against papillomavirus, coupled to immunoaffinity columns, was used to isolate bovine papillomavirus type 1 (BPV-1) and human papillomavirus type 1 (HPV-1) structural polypeptides from homogenates of productively infected cells. One of the polypeptides isolated from bovine fibropapillomas appeared to be the BPV-1 major capsid protein since it had a mol. wt. of 54K and was reactive by Western blots with papillomavirus genus- and BPV-1 type-specific rabbit antibodies as well as monoclonal antibodies cross-reactive with BPV-1/BPV-2 and BPV-1/deer PV. A polypeptide from human plantar warts similarly appeared to be the major capsid component since it also had a mass of 54K to 55K and reacted with papillomavirus genus- and HPV type-specific rabbit antibodies. By using this technique structural viral polypeptides from papillomavirus-induced lesions containing readily detectable viral structural antigens but relatively few virus particles, such as seen with mucosotropic HPVs can now be isolated for mapping of virus-specific epitopes.

Animals↗