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At least 37 records · Page 2Linked to original sources
PubMed1978

Biological characteristics of a stimulatory factor for viral replication detected in egg fluids.

Yolk sac and allantoic fluids and albumen from uninfected chicken eggs contain a low-molecular weight factor which, after 90 minutes of contact with cell cultures, significantly enhances viral replication. Of several viruses tested, Semliki Forest virus exhibited the highest (10(5)-fold) responsiveness to this enhancing factor. Maximal enhancement was obtained with cells subjected to low multiplicities of infection. The stimulation of viral replication was linear with the age of the cells in culture. The enhancing factor did not operate through an anti-interferon mechanism. However, it exerted a boosting effect on the low-grade cellular metabolism of ageing cell monolayers. Some of the physico-chemical features of the enhancing factor were determined and conjectures concerning its chemical makeup are discussed.

Allantois↗
PubMed1978

Type C oncornavirus isolation studies in systemic lupus erythematosus. II. Attempted detection by viral RNA-dependent DNA polymerase assay.

Isolation of type C oncornavirus was attempted from 20 tissues and cell cultures of patients with systemic lupus erythematosus. Chemical inducers, cocultivation and fusion with cells from multiple other species, prolonged subculturing, and the RNA-dependent DNA polymerase assay for virus detection were used. A type C virus was isolated, but was shown to be the endogenous rat virus. Thus the methods, although generally appropriate, were not specifically permissive for replication of a human type C virus. This agrees with the failure of other investigators to isolate a virus of undisputed human origin. Combining available evidence, a fundamental role for type C viruses in lupus erythematosus remains an attractive hypothesis.

Adolescent↗
PubMed1975

Use of electron microscopy for detection of viral and other microbial contaminants in bovine sera.

A total of 25 lots of bovine serum samples were pelleted in Beem capsules for thin sectioning and were examined by electron microscopy. These included 17 lots of fetal bovine serum pools and five lots of calf serum pools obtained from commercial sources, and three lots of adult bovine serum from local dairy farms. Virus-like particles, 50 to 300 nm in diameter, were detected in 17 of 25 (68%) of the sera. Five of 25 serum samples showed the presence of mycoplasma-like agents. Incubation of bovine serum at 35 C for 1 or 2 weeks appeared to destroy some of these agents, but in certain instances it enhanced bacteria and bacteriophage contaminants. The advantages of electron microscopy using the thin-sectioning technique for detection of microbial contamination in bovine sera are illustrated.

Animals↗
PubMed1978

[Immunofluorescence with the PI-3 virus--study of various working conditions for the detection of viral infection using immunofluorescence on various types of cell cultures].

We used the fluorescence method for the investigation of the sensitivity of several kinds of cell cultures to the infection with the parainfluenza virus 3 (PI-3). Cultures from calf kidneys were the most sensitive while we did not determine any differences between primary cultures and cultures of the first and second subpassages and/or freshly cultivated or incubated cultures over seven days at a temperature of 37 degrees C. Equal values of infection titres like on the cultures of calf kidneys were determined by immunofluorescence also on the kidney cells of lambs though the presence of the infection was not accompanied by cytopathic changes. Infection of pig kidney cells appeared only after the inoculation of 10(3) TKID50 and higher doses of the virus, the infection having a very slow course of development without detectable cytopathic changes. Fluorescent findings were identical in different tissues. Antibodies present in the culture medium stopped the spreading of the infection by neutralizing the virus released from the cells, however, not the primary infection. The increase in the content of antibodies in the medium led - by inhibiting the intercellular virus - to the slowing down of the growth of primary fluorescent lesions.

Animals↗
PubMed1979

Canine hemorrhagic enteritis: detection of viral particles by electron microscopy.

At necropsy, several dogs which died showing symptoms of hemorrhagic diarrhea, had significant lesions of the mucosa that were found especially in the duodenum and upper part of the small bowel. Study of ultrathin sections from the diseased mucosa revealed particles resembling parvoviruses in altered nuclei of cells of the intestinal crypts. Electron microscopic examination of intestinal contents by negative staining has shown the presence of many viral particles which have a diameter of 24 nm and whose profile is consistent with an icosahedral shape. These virions float at a density of 1.43 g/cm3 in cesium chloride and agglutinate rhesus monkey and swine red blood cells at 4 degrees C. A possible etiological role is discussed. This virus is compared with the minute virus of canines and the Feline Panleukopenia virus.

Animals↗
PubMed2026

Translating single-cell RNA sequencing into monocyte direct leukocyte subpopulation-transcript abundance assay ratio-based biomarkers (IFI27/PSAP or IFI27/CTSS) for clinical detection of viral infection.

A rapid method for triaging febrile patients by aetiology (e.g., viral or bacterial infection) using gene expression in peripheral blood (PB) is an intensively researched area. However, gene expression in blood represents a composite sum of gene expression of all the component cell types present in the sample. As a result, numerous genes are measured in most proposed signatures. Herein, we propose a simple ratio-based biomarker (RBB) called direct leukocyte subpopulation-transcript abundance assay (DIRECT LS-TA) that recapitulates gene expressions of a single cell type in PB (i.e., monocytes). Based on single-cell RNA sequencing (scRNAseq) data and bulk expression data, IFI27 and SIGLEC1 are found as interferon-stimulated genes (ISGs) predominantly expressed by monocytes. The DIRECT LS-TA method can use a simple ratio of two genes measured in PB as an RBB to represent the target gene expression in monocytes without the need for monocyte purification. Both scRNAseq and bulk RNA sequencing datasets were used to evaluate the correlation between ISG expression in monocytes and PB, with a particular focus on monocyte expression of IFI27. An iceberg plot of bulk transcriptome data was used to identify genes that were predominantly expressed by monocytes in PB. DIRECT LS-TA RBBs of the three genes (IFI27, IFI44L and SIGLEC1) were evaluated by group-wise comparison, receiver operating characteristic and meta-analysis. In addition, the conventional interferon (IFN) score was evaluated for comparison of diagnostic performance. In viral infection datasets, DIRECT LS-TA of IFI27 (IFI27/PSAP or IFI27/CTSS) was most intensely activated (p value by t test <1e-9) and had the best area under the curve (0.94) among the three potential monocyte ISGs analysed. DIRECT LS-TA SIGLEC1 was also another monocyte biomarker but showed a lower activation (p<9e-5). IFI27/PSAP showed better diagnostic performance than the conventional IFN score. On the other hand, IFI44L was not a predominant monocyte expression gene. DIRECT LS-TA of IFI27 (IFI27/PSAP or IFI27/CTSS) measured in PB was the best biomarker of viral infection and IFN activation among ISGs predominantly expressed by monocytes. It performed even better than the conventional IFN score which required quantification of eight genes. The results suggest that DIRECT LS-TA of IFI27 is a monocyte-informative biomarker which is easy to determine in PB without the need for cell sorting.

Humans↗
PubMed2026

Nucleic acid amplification testing and genome sequencing for WHO priority viruses in Africa: a scoping review.

Emerging viruses continue to pose serious public health threats across Africa, with recurrent outbreaks exposing gaps in diagnostics and surveillance systems. Nucleic acid amplification tests (NAATs) and genome sequencing are increasingly important for diagnostics and outbreak responses; however, their routine implementation is fragmented. This scoping review examines NAATs and genome sequencing technologies for viral detection and surveillance in Africa from 2019 to 2024, mapped to the 2024 updated WHO R&D Blueprint for Epidemics pathogen priority list. We identified 117 studies from 34 African countries reporting applications across 20 virus families, including ten designated as priorities by WHO. PCR-based assays were the most frequently reported NAATs. Illumina platforms predominated sequencing, and Oxford Nanopore Technologies were commonly used in outbreak investigations. Genome sequencing applied to priority viruses was largely reactive. NAAT-capable mobile laboratories were reported in 13 countries. Our findings underscore the need for proactive integration of NAATs into diagnostic and surveillance systems to strengthen decentralised testing, sustain genomic surveillance beyond outbreak periods, and improve early detection and preparedness for viral threats.

Journal Article↗
PubMed1976

Epstein-Barr virus in an American patient with Burkitt's lymphoma: detection of viral genome in tumor tissue and establishment of a tumor-derived cell line (NAB).

Epstein-Barr virus (EBV) DNA (17.7 genome equivalents/cell) was found in tumor tissue from an American patient with Burkitt's lymphoma who had never traveled outside the United States. A lymphoid cell line (NAB) containing the EBV genome was established from tumor tissue from this patient; characteristics of this cell line were described. Previous Burkitt's tumors found in Americans and examined by molecular hybridization were negative for EBV DNA. Our results suggested that EBV is associated with at least some American Burkitt's tumors.

Adolescent↗
PubMed1979

Regulation of simian virus 40 early and late gene transcription without viral DNA replication.

Primary cultures of African green monkey kidney cells were infected with the simian virus 40 temperature-sensitive mutant tsA58 at the nonpermissive temperature of 41 degrees C for 12 to 20 h. Under these conditions, a defective T antigen was produced and no viral DNA replication was detected. Viral transcription complexes were extracted from infected nuclei using Sarkosyl and the nascent chains of RNA elongated in vitro. Sixty to 70% of the viral RNA synthesized in vitro hybridized to late gene sequences. In contrast, 80 to 90% of the nuclear viral RNA labeled in vivo during a 15-min pulse with [3H]uridine hybridized to early gene sequences. This suggests that selective degradation of late gene transcripts occurs in vivo. The role of T antigen and viral DNA replication in regulation of simian virus 40 transcription is discussed.

DNA Replication↗
PubMed2026

Real-world pathogen spectrum, clinical actionability, and host correlates of first-time mNGS testing in hospitalized patients with hematologic diseases.

BACKGROUND: Patients with hematologic diseases are highly susceptible to infection. Conventional tests often have low sensitivity. Metagenomic next-generation sequencing (mNGS) can detect many pathogens at once, but its clinical value depends on how the results are interpreted. It is often hard to tell true infection from colonization or contamination. METHODS: We retrospectively studied hospitalized hematologic patients Only adult patients (&#x2265;18 years) who received mNGS for the first time. Detected organisms were reclassified using a clinical actionability system. We also analyzed the relationships between mNGS findings, host characteristics, and short-term outcomes. RESULTS: A total of 134 patients were included. At least one organism was detected in 87.3% of patients, but only 58.2% had highly actionable results. Bacteria were the most common findings, followed by viruses and fungi. Mixed detections were frequent. Actionable results were seen more often in respiratory specimens than in blood specimens. Viral detection was associated with immune status. Pathogen read counts were only weakly related to inflammatory markers and did not independently predict adverse outcomes. Age was the only independent risk factor for adverse outcome. CONCLUSION: mNGS had a high detection rate in hematologic patients, but not all positive findings were clinically important. Result interpretation should take specimen type and host status into account. Pathogen read counts alone were not useful for predicting short-term outcome.

Humans↗
PubMed1975

An immunofluorescent and electron microscopic study of measles skin eruptions.

Immunofluorescent study was attempted to determine whether or not virus antigen were present in the epidermis of measles eruptions. The electron microscopic observations of the same materials were also performed to detect viral localization in affected skins. The failure to detect any virus antigen in affected eipdermis throughout all eruptive stages seems to be sufficient evidence to conclude that measles rash is not a manifestation of viral replication in the epidermis. Dotted fluorescences were detected in a specimen taken at pre-eruptive day in capillary endothelium of dermis. At the same stage, microtubular structures which were probably identical with measles virus nucleocapsids occurred in capillary endothelium under the electron microscopic observations. It is concluded that measles rash is possibly caused by an antigen-antibody reaction of Arthus type. On very rare occasions, measles virus nucleocaspids were found in the cytoplasm of dermal fibroblast in the vicinity of dermal capillary. Ultrastructural features of these nucleocapsids were demonstrated to be identical to features of microtubular structures found in endothelial cells.

Antigens, Viral↗
PubMed1977

Inhibition of host cell protein synthesis by UV-inactivated poliovirus.

The ability of poliovirus that was irradiated with UV light at energies up to 2,160 ergs/mm2 to subsequently inhibit host cell protein synthesis was measured. The inactivation of the host cell shutoff function followed one-hit kinetics. Increasing irradiation did not affect the rate of inhibition until the multiplicity of infection after irradiation was reduced to approximately 1 PFU/cell. At higher functional multiplicities, the rate was unchanged, but an increasing lag before the onset of inhibition was observed with increasing irradiation. The energy levels required to inactivate virus-induced inhibition of host cell protein synthesis suggest that damage to virus RNA rather than to virus capsid proteins is responsible for the loss of function. When the inactivation of host cell shutoff was compared with the inactivation of other viral functions by UV irradiation, it correlated exactly with the loss of infectivity but not with other viral functions measured. Guanidine treatment, which prevents detectable viral RNA and protein synthesis, completely inhibited host cell shutoff by low multiplicities of unirradiated virus infection but not higher multiplicities. When a high multiplicity of virus was first reduced to a low titer by irradiation, host cell shutoff was still evident in the presence of guanidine. The results demonstrate that the complete inhibition of host cell protein synthesis can be accomplished by one infectious viral genome per cell.

Dactinomycin↗
PubMed1979

Rapid detection of dengue viral antigens by counterimmunoelectrophoresis.

Counterimmunoelectrophoresis (CIE) was applied to detect dengue viral antigen in an experimental system and in clinical situations. In the experimental system, all four types of dengue viruses (dengue 1 to 4) were detected when tested against rabbit hyperimmune sera. With homologous antibody, antigen could be detected when hemagglutinating titer was as low as 1:20. In clinical situations, 67% of the sera of patients with dengue hemorrhagic fever collected on day 4 after onset of fever were positive by CIE. Antigens could be detected most frequently from day 4 to day 7. In 11% of the cases, antigens were found to persist as long as 38 days. Validity of this detection was confirmed in some cases by immunologic methods. Virtues of CIE are its technical simplicity, rapidity, and economy.

Antigens, Viral↗
PubMed1978

Regulation of expression and chromosomal subunit conformation of avian retrovirus genomes.

We have investigated the copy number, chromosomal subunit conformation and regulation of expression of integrated avian retrovirus genomes. Our results indicate that there are approximately two copies of the endogenous viral genomes (RAV-O) per haploid cell genome in uninfected chick embryo fibroblasts (CEF) and red blood cells (RBC). The copy number and subunit conformation (as measured by DNAasel sensitivity) of the RAV-O genomes are independent of the level of expression of these viral DNA sequences. In cells isolated from embryos of the V+, gs-chf- and gs+chf+ phenotypes, approximately one of the two viral genomes is in a DNAase l-sensitive conformation. Upon infection with an exogenous Rous sarcoma virus (PR-RSV-C), one new viral genome is integrated per haploid CEF genome. The newly integrated RSV genome is completely sensitive to DNAase l, and the subunit conformation of the endogenous viral genomes is not altered by the integration of additional exogenous proviruses. Both the endogenous and newly integrated exogenous viral genomes are present in "nu-body" structures, and the selective sensitivity of these proviral DNA sequences to DNAase l is maintained in isolated nucleosomes. Our experiments revealing the DNAase l sensitivity of one of the two RAV-O genomes in gs-chf-CEF led us to reexamine the level of viral specific RNA in CEF of various GS genotypes. We find that GS/GS CEF contain approximately 100 copies of viral RNA per cell, gs/gs CEF contain no detectable viral RNA, and the heterozygote GS/gs CEF contain approximately 50 copies of viral specific RNA per cell. These results suggest that the GS gene controls production of RAV-O RNA sequences in CEF in a "cis" fashion. In RBCs, however, the expression of the RAV-O genome is independent of the GS gene, with both GS/GS and gs/gs RBCs containing roughly equivalent amounts of viral specific RNA. Our results suggest that the chromosomal structure of the endogenous viral genes is independent of the GS gene, and that the GS gene is cis-acting and tissue-specific.

Avian Leukosis Virus↗