Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “lytic replication”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed1985

An adenovirus cytocidal function related to the control of a cellular pH 4 endonuclease activity.

An adenovirus (Ad) interserotypic recombinant (H2cyt141) between temperature-sensitive mutant H2ts111 of Ad2 and deletion mutant H5dl313 of Ad5 was isolated and characterized. It was phenotypically ts+, dl+, hr+ and formed large plaques (or cytocidal: cyt). It contained the right 89% of Ad5 DNA and the leftmost 11% of Ad2 DNA. Genetic recombination data suggested the cytocidal mutation lay in the transforming region E1B, confirming sequence analysis. The cytocidal effect resulted in part from the breakdown of cellular DNA. Host cell and virus DNA breakdown induced by H2cyt141 appeared cell-dependent: it occurred in HeLa, KB or BHK-21 cells, but not in CV1 or 293 cells. In human cells the cyt effect was recessive and adenovirus DNA degradation was prevented by co-infection with adenovirus wild-type (H2WT), other adenovirus serotypes or simian virus 40 (SV40). In simian cells, H2cyt141 did not inhibit SV40 DNA replication, unlike H2WT. The amount of H2cyt141 DNA integrated in human cell DNA at early stages of the lytic cycle was found to be significantly lower than for H2WT. Novobiocin inhibited viral DNA breakdown in human cells. Cellular DNA extracted from H2cyt141-infected cells exhibited a repeat band pattern in gel electrophoresis reminiscent of the nuclease digestion pattern of chromatin, with monosome-size fragments as the digestion limit. The H2cyt141-induced nucleolytic effect would therefore occur in the linker regions of cell DNA and might result from the observed stimulation (by a factor of greater than 100) of an acidic (optimum pH 4.0) endonuclease activity. The nucleolytic effect also appeared to be recessive in vitro and absent in mixed samples containing extracts from H2cyt141-infected cells plus extracts from H2WT- or mock-infected cells. The virus gene product responsible for the enhancement of the acidic endonuclease was found to function stoichiometrically and not catalytically. The cytocidal and nucleolytic effects of the viral E1B region 19K protein may be mediated by a cellular inhibitor of acidic endonuclease.

Adenoviruses, Human↗
PubMed1974

Biological properties of two strains of Simian virus 40 isolated from patients with progressive multifocal leukoencephalopathy.

Biological properties of two strains of simian virus 40 (SV40) from brains of two patients with progressive multifocal leukoencephalopathy (PML) have been compared to those of a standard laboratory strain of SV40. Infectivity of both SV40-PML viruses was resistant to treatment with chloroform, low pH, and 50 C for 120 min. African green monkey kidney and BSC-1 cells were the most sensitive for viral replication, and cytopathology in these cultures was indistinguishable from that caused by SV40. Both viruses formed plaques in these cells. but, in African green monkey kidney cells, strain 1 virus produced plaques measuring 2 mm in diameter whereas strain 2 virus produced pleomorphic plaques varying from 1 to 10 mm in diameter. Hamster cells were not permissive for viral replication, and infection resulted only in viral transformation. Inoculation of human fetal glial cells resulted in a permissive lytic infection of one cell type and a persistent infection with only partial expression of the viral genome in the other. No morphological evidence of transformation was evident in the latter cells. Both strains of SV40-PML viruses were neutralized by commercial anti-SV40 serum, but in reciprocal kinetic neutralization tests differences in K values were noted when each was compared to SV40. Both viruses showed oncogenicity for hamsters, producing undifferentiated sarcomas when injected subcutaneously and choroid plexus papillomas after intracerebral inoculation. All hamster tumor cells contained intranuclear immunofluorescent tumor antigen. This was indistinguishable from SV40 T antigen in reciprocal staining reactions using hamster anti-T antibody induced by the two SV40-PML agents and SV40. These two human agents appear therefore to be new variants of simian virus 40.

Animals↗
PubMed2001

Herpes simplex virus type 1 promoter activity during latency establishment, maintenance, and reactivation in primary dorsal root neurons in vitro.

A neonatal rat dorsal root ganglion-derived neuronal culture system has been utilized to study herpes simplex virus (HSV) latency establishment, maintenance, and reactivation. We present our initial characterization of viral gene expression in neurons following infection with replication-defective HSV recombinants carrying beta-galactosidase and/or green fluorescent protein reporter genes under the control of lytic cycle- or latency-associated promoters. In this system lytic virus reporter promoter activity was detected in up to 58% of neurons 24 h after infection. Lytic cycle reporter promoters were shut down over time, and long-term survival of neurons harboring latent virus genomes was demonstrated. Latency-associated promoter-driven reporter gene expression was detected in neurons from early times postinfection and was stably maintained in up to 83% of neurons for at least 3 weeks. In latently infected cultures, silent lytic cycle promoters could be activated in up to 53% of neurons by nerve growth factor withdrawal or through inhibition of histone deacetylases by trichostatin A. We conclude that the use of recombinant viruses containing reporter genes, under the regulation of lytic and latency promoter control in neuronal cultures in which latency can be established and reactivation can be induced, is a potentially powerful system in which to study the molecular events that occur during HSV infection of neurons.

Animals↗
PubMed2006

Epstein-Barr virus protein kinase BGLF4 is a virion tegument protein that dissociates from virions in a phosphorylation-dependent process and phosphorylates the viral immediate-early protein BZLF1.

Epstein-Barr virus (EBV) BGLF4 is a viral protein kinase that is expressed in the lytic phase of infection and is packaged in virions. We report here that BGLF4 is a tegument protein that dissociates from the virion in a phosphorylation-dependent process. We also present evidence that BGLF4 interacts with and phosphorylates BZLF1, a key viral regulator of lytic infection. These conclusions are based on the following observations. (i) In in vitro tegument release assays, a significant fraction of BGLF4 was released from virions in the presence of physiological NaCl concentrations. (ii) Addition of physiological concentrations of ATP and MgCl(2) to virions enhanced BGLF4 release, but phosphatase treatment of virions significantly reduced BGLF4 release. (iii) A recombinant protein containing a domain of BZLF1 was specifically phosphorylated by purified recombinant BGLF4 in vitro, and BGLF4 altered BZLF1 posttranslational modification in vivo. (iv) BZLF1 was specifically coimmunoprecipitated with BGLF4 in 12-O-tetradecanoylphorbol-13-acetate-treated B95-8 cells and in COS-1 cells transiently expressing both of these viral proteins. (v) BGLF4 and BZLF1 were colocalized in intranuclear globular structures, resembling the viral replication compartment, in Akata cells treated with anti-human immunoglobulin G. Our results suggest that BGLF4 functions not only in lytically infected cells by phosphorylating viral and cellular targets but also immediately after viral penetration like other herpesvirus tegument proteins.

Cell Line↗
PubMed1976

Replication of type 2 herpes simplex virus in human endocervical tissue in organ culture.

The replication of type 2 herpes simplex virus in human endocervical tissue in organ culture was investigated. The temporal profile of virus replication was related to the initial virus inoculum; high input inocula induced a rapid increase in virus titre while lower multiplicities induced a more slow-rising increase in virus titre. Our evidence suggested that explants were capable of initiating and supporting virus replication for at least 2 weeks following establishment of the culture. Virus yields were optimal when explants were cultured at 37 degrees and in serum-supplemented medium. Explants also supported the replication of type 1 herpes simplex virus and a "non-human" herpes simplex virus (pseudo-rabies virus). The optimal conditions for replication of type 2 herpes simplex virus in human endocervical explants have been established and will provide a model permitting precise investigation of lytic or other virus-cervical cell interactions and their possible relationship to herpes virus-induced pre-invasive carcinoma of this organ.

Adult↗
PubMed1998

Characterization of a nerve growth factor-inducible cellular activity that enhances herpes simplex virus type 1 gene expression and replication of an ICP0 null mutant in cells of neural lineage.

Herpes simplex virus type 1 (HSV-1) ICP0 is required for efficient viral gene expression during lytic infection, especially at low multiplicities. A series of cellular activities that can substitute for ICP0 has been identified, suggesting that when the activity of ICP0 is limiting, these activities can substitute for ICP0 to activate viral gene expression. The cellular activities may be especially important during reactivation of HSV from neuronal latency when viral gene expression is initiated in the absence of prior viral protein synthesis. Consistent with this hypothesis, we have identified an inducible activity in cells of neural lineage (PC12) that can complement the low-multiplicity growth phenotype of an ICP0 null mutant, n212. Pretreatment of PC12 cells with nerve growth factor (NGF) or fibroblast growth factor (FGF) prior to infection produced a 10- to 20-fold increase in the 24-h yield of n212 but only a 2- to 4-fold increase in the yield of wild-type virus relative to mock treatment. Slot blot analysis of nuclear DNA isolated from infected cells treated or mock treated with NGF indicated that NGF treatment does not significantly affect viral entry. The NGF-induced activity in PC12 cells was expressed transiently, with peak complementing activity observed when cells were treated with NGF 12 h prior to infection. Addition of NGF 3 h after infection had little effect on virus yield. The NGF-induced cellular activity was inhibited by pretreatment of PC12 cells with kinase inhibitors that have high specificity for kinases involved in NGF/FGF-dependent signal transduction. RNase protection assays demonstrated that the NGF-inducible PC12 cell activity, like that of ICP0, functions to increase the level of viral mRNA during low-multiplicity infection. These results suggest that activation of viral transcription by ICP0 and transcriptional activation of cellular genes by NGF and FGF utilize common signal transduction pathways in PC12 cells.

Animals↗
PubMed1975

Simian virus 40 DNA replication, transcription, and antigen induction during infection with two adenovirus 2-SV40 hybrids that contain the entire SV40 genome.

The Ad2++hey hybrid virus population produces simian virus 40 (SV40) efficiently during lytic infection, whereas Ad2++ley does not, although both hybrids contain a complete SV40 genome. In this report, we demonstrate the synthesis of nonhydrid SV40 DNA in Ad2++HEY-infected Vero cells, but only early SV40 RNA is transcribed efficiently in Ad2++LEY-infected cells. Ad2++HEY induces SV40 U, T, and V antigens during lytic infection of African green monkey kidney cells, whereas Ad2++LEY induces only SV40 U and T antigens. These variations in the behavior of Ad2++HEY and Ad2++LEY regarding expression of SV40 functions probably reflect differences in the rate of SV40 excision from the hybrid genomes.

Adenoviridae↗
PubMed1998

Natural killer cells from human immunodeficiency virus (HIV)-infected individuals are an important source of CC-chemokines and suppress HIV-1 entry and replication in vitro.

Macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and RANTES (regulated on activation, normal T cell expressed and secreted), which are the natural ligands of the CC-chemokine receptor CCR5, inhibit replication of MT-2- negative strains of HIV-1 by interfering with the ability of these strains to utilize CCR5 as a coreceptor for entry in CD4(+) cells. The present study investigates the capacity of natural killer (NK) cells isolated from HIV-infected individuals to produce CC-chemokines and to suppress HIV replication in autologous, endogenously infected cells as well as to block entry of MT-2-negative HIV into the CD4(+) T cell line PM-1. NK cells freshly isolated from HIV-infected individuals had a high number of mRNA copies for MIP-1alpha and RANTES. NK cells produced significant amounts of RANTES, MIP-1alpha, and MIP-1beta constitutively, in response to stimulation with IL-2 alone and when they were performing their characteristic lytic activity (K562 killing). After CD16 cross-linking and stimulation with IL-2 or IL-15 NK cells produced CC-chemokines to levels comparable to those produced by anti-CD3-stimulated CD8(+) T cells. Furthermore, CD16 cross-linked NK cells suppressed (49-97%) viral replication in cocultures of autologous CD8/NK-depleted PBMC to a degree similar to that of PHA or anti-CD3-stimulated CD8(+) T cells. In 50% of patients tested, NK-mediated HIV suppression could be abrogated by neutralizing antibodies to MIP-1alpha, MIP-1beta and RANTES; in contrast, CD8(+) T cell-mediated suppression was not significantly overcome upon neutralization of CC-chemokines. Supernatants derived from cultures of CD16 cross-linked NK cells stimulated with IL-2 or IL-15 dramatically inhibited entry of a MT-2-negative strain of HIV, BaL, in the CD4(+)CCR5(+) PM-1 T cell line. These data suggest that activated NK cells may be an important source of CC-chemokines in vivo and may suppress HIV replication by CC-chemokine-mediated mechanisms in addition to classic NK-mediated lytic mechanisms.

CD3 Complex↗
PubMed1999

Prolonged induction of IL-8 gene expression in a human fibroblast cell line infected with reovirus serotype 1 strain Lang.

Viruses which infect mucosal surfaces commonly infect these particular anatomical sites based on both the virion structure and the interaction of the virus with a particular microenvironment. We infected a human lung epithelial cell line, a human gut epithelial cell line, and a human lung fibroblast cell line with reovirus 1/L to explore how this natural isolate of both the lung and the gut may interact with mucosal surfaces. While reovirus infection of the gut and lung epithelial cell lines was lytic, a chronic infection was established in the human lung fibroblast cell line. All three cell lines also produced interleukin-8 (IL-8) after infection with reovirus 1/L, and IL-8 production was not dependent upon viral replication. A prolonged production of IL-8 was observed in the chronically infected lung fibroblast cell line, suggesting that this mucosal population may be involved in the generation of inflammatory responses after the resolution of the initial lytic infection of the epithelium. These studies provide an in vitro model system for analyzing the interaction of reovirus 1/L with resident mucosal cell populations.

Cell Line↗
PubMed2001

Human cytomegalovirus with IE-2 (UL122) deleted fails to express early lytic genes.

Much evidence suggests that the major immediate-early (IE) transactivator of human cytomegalovirus (HCMV), IE-2, is likely to be critical for efficient viral replication; however, the lack of an IE-2 mutant HCMV has precluded an experimental test of this hypothesis. As an initial step toward characterizing an IE-2 mutant, we first cloned the HCMV Towne genome as a bacterial artificial chromosome (BAC) and analyzed the ability of transfected Towne-BAC DNA (T-BACwt) to produce plaques following introduction into permissive human fibroblasts. Like Towne viral DNA, transfected T-BACwt DNA was infectious in permissive cells, and the resulting virus stocks were indistinguishable from Towne virus. We then used homologous recombination in Escherichia coli to delete the majority of UL122, the open reading frame encoding the unique portion of IE-2, from T-BACwt. From this deleted BAC, a third BAC clone in which the deletion was repaired with wild-type UL122 was created. In numerous transfections of permissive human foreskin fibroblast cells with these three BAC DNA clones, the rescued BAC and T-BACwt consistently yielded plaques, while the UL122 mutant BAC never generated plaques, even after 4 weeks. Protein and mRNA of other IE genes were readily detected from transfected UL122 mutant BAC DNA; however, reverse transcription-PCR failed to detect mRNA expression from any of five early genes examined. The generalized failure of this mutant to express early genes is consistent with expectations from in vitro assays which have demonstrated that IE-2 transactivates most HCMV promoters. These experiments provide the first direct demonstration that IE-2 is required for successful HCMV infection and indicate that virus lacking IE-2 arrests early in the replication cycle.

Antigens, Viral↗
PubMed1988

SV40 T-antigen binding to site II is functionally separated from binding to site I.

During lytic infection SV40 T antigen binds specifically to three different regions of the SV40 DNA to initiate viral DNA replication and to regulate early and late transcription. We have used the recently described plasmids pKB1, containing a 23-bp oligonucleotide coding for site I, pdl1085 containing sites II and III together with SV40 specific flanking sequences, and as a control pATC, a plasmid which contains all three binding sites (D. Müller et al. (1987), Virology 161, 81-91) to analyze the differential binding of T antigen to these individual binding sites in the course of an SV40 infection. We found that shortly after infection the amount of bound DNA increased with the concentration of T antigen reaching a steady-state level at about 20 hr after infection. In comparison to binding at site I, binding to site II appeared with a delay of about 8-9 hr corresponding to the onset of viral DNA replication. The correlation between binding of T antigen to site II and the SV40 DNA replication could be further corroborated by using T antigen from the heat-sensitive mutant tsA58 which completely failed to bind to site II at nonpermissive temperature but exhibited a residual binding to site I. This reduced binding to site I proved insufficient for the proper functioning of autorepression. Our results support the hypothesis that distinctly different subclasses of T-antigen binding to site I or site II may exist.

Antigens, Polyomavirus Transforming↗
PubMed2000

Bacteriophage PRD1 DNA entry uses a viral membrane-associated transglycosylase activity.

Amino acid sequence analyses have indicated that the amino-terminal part of bacteriophage PRD1 structural protein P7 carries a conserved transglycosylase domain. We analysed wild-type PRD1 and different mutant particles in zymograms and found a glycolytic activity that was associated with protein P7. This is the first time a putative bacteriophage or plasmid lytic transglycosylase has been shown to have an enzymatic activity. In the absence of protein P7, the phage DNA replication and host cell lysis were delayed. Gene VII of PRD1 is known to encode proteins P7 and P14. In this investigation, the open reading frame coding for P14 was mapped to the 3' end of gene VII. Proteins P7 and P14 probably form a heteromultimeric complex, which is located at the particle vertices and is involved in the early steps of the PRD1 life cycle

Cell Membrane↗
PubMed1997

Effect of DNA synthesis inhibitors on Kaposi's sarcoma-associated herpesvirus cyclin and major capsid protein gene expression.

Epidemiological studies strongly suggest that a newly discovered herpesvirus, Kaposi's sarcoma associated-herpesvirus (KSHV/HHV8), is the likely infectious cause of Kaposi's sarcoma (KS). Identification of this agent suggests the possibility that existing anti-herpesvirus chemotherapeutics have activity against KSHV. Using KSHV/Epstein-Barr virus (EBV)-coinfected cell line BC-1 and KSHV-infected/EBV-negative cell line BC-3, the effect of DNA polymerase inhibitors in the presence of virus-inducing agents was examined. The phorbol ester TPA induced 8.2-fold EBV replication in BC-1 cells with only minimal concurrent KSHV genome replication in BC-1, but induced fourfold KSHV in BC-3 cells. TPA, however, induced transcripts encoded by the lytic cycle major capsid protein gene that were inhibited by both phosphonoacetic acid and phosphonoformic acid either in the KSHV/EBV-infected cell line or in the EBV-negative/KSHV-infected cell line. Transcripts hybridizing to a KSHV-encoded cyclin gene were unaffected by either TPA or DNA polymerase inhibitors in both cell lines. These results show in vitro activity of DNA polymerase inhibitors on KSHV lytic transcript accumulation and may provide a simple assay for evaluating the efficacy of potential anti-KSHV chemotherapeutics.

Blotting, Northern↗
PubMed2002

Characterization of Kaposi sarcoma-associated herpesvirus/human herpesvirus-8 infection of human vascular endothelial cells: early events.

Kaposi sarcoma-associated herpesvirus (KSHV)/human herpesvirus-8 (HHV-8) is causally associated with Kaposi sarcoma (KS). The absence of a cell culture system that effectively reproduces the composite mechanisms governing initiation and maintenance of HHV-8 infection (lytic and latent) in KS endothelial cells, however, has left important questions unanswered. Here, we report a culture system in which the earliest events that accompany HHV-8 infection could be surveyed in primary endothelial cells. Binding of HHV-8 to microvascular dermal endothelial cells (MVDECs) was directly compared with other primary target cells implicated in HHV-8-associated diseases. Virus attachment, fusion, internalization and transport within MVDECs was monitored by electron microscopy. Studies of genome configuration revealed that rapid circularization of the viral DNA occurred on entry, though by 72 hours after infection linear DNAs accumulated and early as well as late lytic RNAs (T1.1, K8.1) could be detected. The latency transcripts (LT1/LT2) were first detected on day 8, demonstrating that both lytic and latent infection were initiated. Although most lytic transcripts accrued until passage, open-reading frame-74 RNAs fluctuated with a fixed periodicity, suggesting that early replication after infection of MVDECs was synchronous.

Cell Culture Techniques↗
PubMed1986

Studies on the SV40-like papovavirus SV40-GBM. III. Propagation at low multiplicities of infection in various human cell lines.

At low multiplicity several human cell lines supported the lytic infection with SV40-GBM better than that with the wild type SV40. The efficiency of viral DNA replication differed in the cell lines used suggesting that specific host cell factors may determine the rate of viral DNA synthesis. Furthermore, the emergence of different DNA defects during propagation of the virus indicates that host cell factors in question might also influence the composition of the viral DNA population.

Cell Line↗
PubMed1979

The genome of human papovavirus BKV.

The complete DNA sequence of human papovavirus BKV(Dun), consisting of 5153 nucleotide pairs, is presented. We describe the segments of the genome which correspond to the replication origin, the tandem repeated sequences, the 5' and 3' ends of the mRNAs, the splice sites, the early and late viral proteins and the putative viral polypeptides. These BKV DNA sequences are compared with analogous regions in the SV40 and Py virus genomes in an attempt to localize viral functions for lytic growth and transformation.

Amino Acid Sequence↗
PubMed2000

HIV infection of megakaryocytic cell lines.

Thrombocytopenia is a common hematologic disorder in HIV infection and occurs in both asymptomatic and AIDS patients. An autoimmune mechanism has been postulated for the platelet destruction associated with some forms of thrombocytopenia. However, recent studies revealed that megakaryocytes are susceptible to HIV infection and suggested the possibility that HIV can directly impair the platelet production from megakaryocytes. This study was designed to characterize the HIV receptor expression in megakaryocytic cells and the responsiveness to HIV infection. Four different megakaryocytic cell lines at different stages of differentiation were established from the peripheral blood of different individuals with hematologic malignancies. CMK and CMY cells (differentiated cell lines) expressed CD4, but CMS and CTS cells (poorly differentiated cell lines) did not. The HIV coreceptor CXCR4 was also expressed in CMY and CMK cells. HIV-1 (HTLV-IIIB) replicated in CMY cells persistently but not in other three cell lines. CMY cells as well as CMK cells were also susceptible to the lytic infection of HIV-2 (LAV2). Pretreatment of the CMY cells with anti-CD4 antibody inhibited the infection by both HIV-1 and HIV-2. Our results indicate that mature megakaryocytic cells express CD4 along with HIV coreceptors and are susceptible to HIV infection.

CD4 Antigens↗