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At least 1,567 records · Page 87Linked to original sources
PubMed1979

Lysosome stability during lytic infection by simian virus 40.

By 48 h postinfection, 40--80% of SV40-infected CV-1 cells have undergone irreversible injury as indicated by trypan blue staining. Nevertheless, at this time the lysosomes of these cells appear as discrete structures after vital staining with either acridine orange or neutral red. Lysosomes, vitally stained with neutral red at 24 h postinfection, were still intact in cells stained with trypan blue at 48 h. Acid phosphatase activity is localized in discrete cytoplasmic particles at 48 h, as indicated by histochemical staining of both fixed and unfixed cells.

Acid Phosphatase↗
PubMed1999

Characterization of Pseudomonas aeruginosa bacteriophage UNL-1, a bacterial virus with a novel UV-A-inducible DNA damage reactivation phenotype.

UNL-1, a lytic virus of Pseudomonas aeruginosa, was observed to express a novel inducible DNA damage reactivation activity in UV-A-irradiated P. aeruginosa host cells. The expression of bacteriophage reactivation was quantified in hosts exposed to either UV-C or UV-A radiation. While reactivation of UV-C-damaged UNL-1 was not inducible in UV-C-irradiated host cells, an approximately 13-fold induction was observed in UV-A-irradiated host cells. When host cells were exposed to sunlight, reactivation of damaged UNL-1 virus increased eightfold. The UV-A induction of UNL-1 DNA damage reactivation was supported in hosts lacking recA gene function. This report is the first description of a recA-independent, UV-inducible virus DNA damage repair system. Our findings suggest that a combination of both host and virus DNA repair processes contribute to the persistence and sustained replication of some bacterial viruses in aquatic environments.

Base Composition↗
PubMed1985

Association of phosphorylated simian virus 40 T-antigen with subnuclear fractions of infected and transformed cells.

To define the roles of subnuclear structure in SV40 infection, the relative distribution of T-antigen (T-ag) in various subnuclear fractions obtained from both lytically infected and transformed African green monkey kidney cells was determined. Depending on the differential sensitivity of nuclear T-ag to extraction by salt and detergent, nuclear T-ag could be separated into nucleoplasmic T-ag, salt-sensitive T-ag and matrix-bound T-ag subclasses. At least fivefold less matrix-bound T-ag was found in transformed cells than in lytically infected cells. While a cAMP-independent protein kinase was detected in the nuclear matrix, the matrix-bound T-ag (94K) could not be phosphorylated in vitro. The removal of cellular chromosomes by DNase caused changes in the interaction of T-ag with nuclear components. The results suggest that the compartmentalization of nuclear T-ag may be determined by its interaction with host chromosomes.

Animals↗
PubMed2005

Susceptibility of human and rat neural cell lines to infection by SARS-coronavirus.

Pathological characterization of autopsied tissues from patients with SARS revealed severe damage in restricted tissues, such as lung, with no apparent cell damage in other tissues, such as intestine and brain. Here, we examined the susceptibility of neural cell lines of human (OL) and rat (C6) origins to SARS-associated coronavirus. Both of the neural cell lines showed no apparent cytopathic effects (CPE) by infection but produced virus with infectivity of 10(2-5) per ml, in sharp contrast to the production by infected Vero E6 cells of >10(9) per ml that showed a lytic infection with characteristic rounding CPE. Interestingly, the infection of intestinal cell line CaCo-2 also induced no apparent CPE, with production of the virus at a slightly lower level as that of the Vero E6 cell culture. Notably, the cellular receptor for the virus, angiotensin-converting enzyme 2 was expressed at similar levels on Vero E6 and CaCo-2 cells, but at undetectable levels on OL and C6 cells.

Animals↗
PubMed2002

Gammaherpesvirus lytic gene expression as characterized by DNA array.

Gammaherpesviruses are associated with a number of diseases including lymphomas and other malignancies. Murine gammaherpesvirus 68 (MHV-68) constitutes the most amenable animal model for this family of pathogens. However experimental characterization of gammaherpesvirus gene expression, at either the protein or RNA level, lags behind that of other, better-studied alpha- and beta-herpesviruses. We have developed a cDNA array to globally characterize MHV-68 gene expression profiles, thus providing an experimental supplement to a genome that is chiefly annotated by homology. Viral genes started to be transcribed as early as 3 h postinfection (p.i.), and this was followed by a rapid escalation of gene expression that could be seen at 5 h p.i. Individual genes showed their own transcription profiles, and most genes were still being expressed at 18 h p.i. Open reading frames (ORFs) M3 (chemokine-binding protein), 52, and M9 (capsid protein) were particularly noticeable due to their very high levels of expression. Hierarchical cluster analysis of transcription profiles revealed four main groups of genes and allowed functional predictions to be made by comparing expression profiles of uncharacterized genes to those of genes of known function. Each gene was also categorized according to kinetic class by blocking de novo protein synthesis and viral DNA replication in vitro. One gene, ORF 73, was found to be expressed with alpha-kinetics, 30 genes were found to be expressed with beta-kinetics, and 42 genes were found to be expressed with gamma-kinetics. This fundamental characterization furthers the development of this model and provides an experimental basis for continued investigation of gammaherpesvirus pathology.

Animals↗
PubMed1996

Characterization of Epstein-Barr virus recombinants with deletions of the BamHI C promoter.

Epstein-Barr virus (EBV) recombinants with the BamHI C promoter (Cp) deleted were compared with wild-type Cp recombinants derived in parallel for their ability to initiate and maintain latent infection and growth transformation in primary human B lymphocytes. Cp-deleted recombinants infected, transformed, and immortalized B lymphocytes in vitro as efficiently as wild-type Cp recombinant EBV. Lymphoblastoid cell lines (LCLs) infected with the Cp-deleted recombinant were indistinguishable from wild-type recombinant-infected LCLs in latent gene expression, growth rate, morphology, and surface phenotype. Deletion of Cp did not affect episomal maintenance or spontaneous entry of the virus into lytic cycle. The effect of steroid hormones on latent and lytic gene expression on Cp-deleted recombinants was analyzed and shown to be independent of the glucocorticoid response element located 5' to Cp. The BamHI W promoter, Wp, is used to transcribe EBNA genes in Cp-deleted EBV-infected cells. Wp is sufficient for growth transformation and maintenance of the lymphoblastoid phenotype of EBV-infected lymphocytes in vitro.

Antigens, Viral↗
PubMed1972

Synthesis of viral ribonucleic acid during restricted adenovirus infection.

The mechanism by which simian virus 40 converts the abortive adenovirus type 7 infection of monkey cells into an efficient lytic infection has been investigated. Analysis of ribonucleic acid (RNA) synthesis during unenhanced and enhanced infection of monkey cells has shown that adenovirus RNA synthesized in the abortive infection contains both "early" and "late" sequences. In hybridization competition experiments, early adenovirus RNA from human cells prevented the hybridization of only 20% of the adenovirus RNA transcribed in unenhanced infection. Further, the RNA from unenhanced cells was able to completely block the hybridization of RNA synthesized during enhanced infection. Finally, virus-associated RNA, which is a late RNA transcribed in lytic adenovirus infection, is also produced in the unenhanced infection. An accompanying paper describes a marked deficiency in adenoviral capsid protein synthesis in the unenhanced infection. We conclude that RNA sequences, which are sufficient to code for the synthesis and assembly of structural proteins of adenovirus, are transcribed but are not efficiently translated in the unenhanced adenovirus infection of monkey cells.

Adenoviridae↗
PubMed1976

Two adenovirus type 2-simian virus 40 hybrid populations that contain the entire SV40 genome differ in their ability to induce SV40 transplantation immunity in hamsters but not in mice.

Ad2++ HEY and Ad2++ LEY are two adenovirus 2(Ad2)-simian virus 40 (SV40) hybrids distinguished by differences in the efficiency with which they produce SV40 progeny in lytically infected African green monkey kidney cells. These virus populations are composed of nonhybrid Ad2 and hybrid virions, the majority of which contain more than 1 unit of SV40 DNA. The Ad2++ HEY and LEY populations also differ in their ability to induce SV40 transplantation immunity in rodents. Only Ad2++ HEY induces SV40 transplantation immunity in hamsters, whereas both viruses induce significant SV40 transplantation immunity in adult BALB/c mice.

Adenoviruses, Human↗
PubMed1978

[Capacity of clones of vaccinia virus to multiply at different temperatures and pH values].

The study of the biological characteristics of ten clones, isolated from plaque, of vaccinia virus has made evident that two of these characteristics--the capacity to multiply at 40 degrees C and the type of CPE in animal cell cultures--can be used as genetic markers of neuropathogenicity, valued in relationship to the property to induce demyelinating encephalitis in mice injected intracerebrally or intravenously. The most neurovirulent clones demonstrated high capacity to multiply at 40 degrees C and lytic CPE; the clones, that did not have (or had at a very low level) encephalitogenic activity in mice, presented poor capacity to multiply at 40 degrees C and CPE of syncytial type. The variation of the pH of the cell culture medium enhances the difference of CPE induced by clones that had different levels of neuropathogenicity. The results are discussed in relation to their use in improving the smallpox vaccine.

Animals↗
PubMed1977

Temperate Bacillus subtilis bacteriophage phi 3T: chromosomal attachment site and comparison with temperate bacteriophages phi 105 and SPO2.

The temperate Bacillus subtilis bacteriophage phi 3T contains within its genome a locus, designated thyP3, that encodes for a protein with thymidylate synthetase activity. Bacteriophage phi 3T is different from the two previously characterized temperate phages, phi 105 and SPO2, in: heteroimmunity, response to bacteriophage antisera, endonuclease digestion pattern, induction in the presence of 6-(p-hydroxyphenylazo)-uracil, and effect on the lytic cycle of bacteriophage phi 1. The mean burst size of phi 3T is 56. The dose response curve with bacteriophage phi 3T DNA is linear for transfection and transformation to the Thy+ phenotype. The inserted prophage has been mapped by PBS1 transduction; it is between chromosomal markers ilvA8 and gltA in the terminus of the chromosome. Thus thyP3 maps at a site separate from, but between, the bacterial markers thyA and thyB when thyP3 is in the prophage state.

Bacillus subtilis↗
PubMed1984

Infection of mouse lymphocytes by Epstein-Barr virus. II. Stimulation of cellular DNA synthesis by EBV in the absence of EBNA induction and cell transformation.

Epstein-Barr virus (EBV) of the transforming and nontransforming strains induced transient stimulation of cellular DNA synthesis during lytic infection of normal mouse lymphocytes. In contrast to human B lymphocytes, the action of both EBV strains in mouse cells was additive. The nontransforming P3HR-1 virus had no cytotoxic effect on mouse lymphocytes. The EBV-infected, stimulated mouse lymphocytes did not express EB virus-determined nuclear antigen and do not grow into immortalized cell lines. The cells expressed EBV-determined early and virus capsid antigens. These results suggest that the stimulation of cellular DNA synthesis by EBV is independent of EBNA synthesis and cell transformation.

Animals↗
PubMed1972

A bacteriophage of Bacillus subtilis which forms plaques only at temperatures above 50 C. I. Physical and chemical characteristics of TSP-1.

Bacteriophage TSP-1 was isolated from soil in a search for phage which would form plaques on Bacillus subtilis W168 at 53 C. It forms clear plaques only at temperatures from 50 to 55 C. Approximately 95% of the free phage adsorb after 2 min at 53 C. The lytic cycle is between 55 and 60 min long with a burst size of about 55 particles per infected bacterium. The phage was shown to contain double-stranded deoxyribonucleic acid with a base composition of 44.7% guanine plus cytosine. This deoxyribonucleic acid does not contain a base analogue for thymine and has a molecular weight estimated at 56 x 10(6) daltons.

Adsorption↗
PubMed1976

Early events in the lytic infection of primary mouse kidney cell culture with polyoma virus. The effect of various input multiplicities.

Early polyoma (Py) virus-specific RNA synthesis was examined in cells infected with different concentrations of Py-virus. The effect of various multiplicities of infection (m.o.i.) on the rate of Py-RNA synthesis is different at 30 hr as compared to 65 hr. Thirty hours after infection at 27degrees, in the presence of 5-fluoro-2-deoxyuridine (FdU), an increase in input multiplicity was not associated with a quantitatively commensurate increase in the amount of virus-specific RNA synthesized. At 65 hr, the amount of viral RNA synthesized was roughly proportional to the number of infecting virus particles.

Cells, Cultured↗
PubMed1976

Isolation and characterization of poly(A)-containing polyoma "early" and "late" messenger RNAs.

During late lytic infection of mouse kidney cell cultures polyoma 16S and 19S (late 19S RNA) were isolated by oligo(dT)-cellulose chromatography. Approximately 60-80% of total cytoplasmic polyoma RNA contained tracts of poly(A) which were retained by oligo(dT)-cellulose. Early in lytic infection when viral DNA synthesis and the production of capsid protein are blocked by the addition of 5-fluorodeoxyuridine, approximately 100% of polyoma "early" 19S RNA was quantitatively retained by oligo(dT)-cellulose indicating the presence of poly(A) tracts on most 19S mRNA molecules. In addition, 2 classes polyoma RNA, synthesized after the onset of cellular RNA synthesis under conditions where DNA synthesis is inhibited with 5-fluorodeoxyuridine, were found to contain tracts of poly(A). These species sedimenting at 16S and 19S in aqueous sucrose density gradients were also quantitatively retained by oligo (dT)-cellulose.

Cell Line↗
PubMed1994

Bone marrow atrophy induced by murine cytomegalovirus infection.

Acute, sublethal infection of mice with murine cytomegalovirus (MCMV) resulted in up to 80% decreases in the number of cells recoverable from the bone marrow, and a decrease in peripheral blood leucocyte counts during the first week of infection. Depopulation of the leucopoietic areas of the marrow was evident from examination of histological sections. The severity of bone marrow atrophy in MCMV-infected mice of different strains correlated with previously described genetically determined sensitivity to MCMV disease. Although the phenomenon only occurred when mice were inoculated with infectious virus preparations, fewer than one in 10(5) marrow cells were productively infected, suggesting that atrophy was not due to lytic infection of large numbers of bone marrow cells. Interestingly, increases in serum colony-stimulating activity were observed and these were proportional to the severity of bone marrow atrophy. After MCMV infection, we observed increases in the proportions of cells expressing some B-cell and myeloid cell markers and a decrease in the proportion of cells expressing an erythroid cell marker. There was no change in the frequency of marrow cells expressing mature T-cell markers. The numbers of myeloid lineage-committed progenitor cells (GM-CFU) in the marrow decreased 10- to 20-fold in BALB/c nu/+ mice, while there was a threefold decrease in their numbers in BALB/c nu/nu mice. In addition, increases in serum colony-stimulating activity were greater in BALB/c nu/+ mice than in BALB/c nu/nu mice. Our results suggest that growth factors produced after MCMV infection may accelerate the maturation and migration of cells from the marrow to sites of virus replication and inflammation, thus accounting for the depletion in numbers of marrow cells observed soon after MCMV infection.

Animals↗
PubMed2000

Lytic Epstein-Barr virus infection in the synovial tissue of patients with rheumatoid arthritis.

OBJECTIVE: To evaluate the existence of Epstein-Barr virus (EBV) infection in the synovial tissue of patients with rheumatoid arthritis (RA). METHODS: Synovial tissues were obtained at synovectomy or arthroplasty from 32 patients with RA and 30 control patients with osteoarthritis (OA). EBV DNA was detected by Southern blot hybridization and/or polymerase chain reaction (PCR) amplification. To localize the EBV-infected cells, tissue sections were studied by RNA in situ hybridization (ISH) for the EBV-encoded small RNA 1 (EBER-1), by DNA ISH for the Bam HI W region of EBV DNA, and by immunohistochemistry for EBV lytic proteins BZLF1 and gp350/220. RESULTS: EBV DNA was detected by PCR in 15 of the 32 samples from RA patients (47%), but in none of those from the 30 OA patients (P < 0.01). Of the 15 PCR-positive samples, 9 contained >1 EBV copy/1,000 cells (referred to as EBV 2+), and 6 contained 1 copy/1,000-5,000 cells (EBV 1+). Among the 9 EBV 2+ samples, 3 were also positive for EBV DNA by Southern blot hybridization, 5 were positive for EBER-1 by RNA ISH, and 3 were positive for EBV DNA by DNA ISH. Immunohistochemical analysis showed positive signals in all samples for BZLF1 and in 7 samples for gp350/ 220. In each examination, the positive signals were detected not only in lymphocytes, but also in synovial lining cells. CONCLUSION: EBV was frequently detected in the synovial tissue of RA patients. The infected cells were both lymphocytes and synovial cells, and expressed EBV proteins associated with virus replication. These findings suggest that EBV may play a role in the pathogenesis of RA.

Adult↗
PubMed2005

Host and viral proteins in the virion of Kaposi's sarcoma-associated herpesvirus.

Infection of cultured cells with Kaposi's sarcoma associated herpesvirus (KSHV) typically establishes a latent infection, in which only a few viral genes are expressed. Recently, it has been reported that a subset of lytic genes are transiently expressed very early after viral entry but that this burst of abortive lytic gene expression is terminated with the supervention of latency (H. H. Krishnan, P. P. Naranatt, M. S. Smith, L. Zeng, C. Bloomer, and B. Chandran, J. Virol. 78:3601-3620, 2004). To identify molecules imported into cells by KSHV that might influence this gene expression program, we have examined the protein composition of the KSHV particle. Immunoblotting of virus particles demonstrated that RTA, the lytic switch protein, and RAP, a viral protein that is a transcriptional and cell cycle modulator, were both incorporated into virus particles. In a second approach, polypeptides isolated from purified virions were identified by mass-spectrometric analysis of their constituent tryptic peptides. With this approach we were able to identify 18 major virion proteins, including structural, regulatory, and signaling proteins of both viral and cellular origin.

Amino Acid Sequence↗
PubMedDate not supplied

Acute and persistent viral infections of differentiated nerve cells.

Within the nervous system the highly specialized structure and function of nerve cells renders the pathogenesis of viral infections amazingly complex. In vivo and in vitro studies reveal that viruses may display tropism for distinct types of cells such as neurons, myelin-forming cells, or astrocytes. In neurons, RNA viruses mature in the cell body and in dendrites close to synapses, from which they can spread to synaptic endings. Undefined host factors and stage of differentiation may favor defective viral assembly, which, in turn, results in persistent infections of neurons. In myelin-forming cells, lytic infection results is persistent infections of neurons. In myelin-forming cells, lytic infection results in degeneration of myelin and, consequently, in altered conduction in those axons that are ensheathed by a myelin-forming cell. In addition, breakdown of myelin may induce an autoimmune response, which then leads to further demyelination. Autoimmune demyelination may also occur when glial cells other than myelin-forming cells are infected. Astrocytes are prone to persistent infection or viral transformation.

Animals↗