PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Virus Internalization”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 145 records · Page 8Linked to original sources
PubMed1994

Identification of an immediate-early gene in the Marek's disease virus long internal repeat region which encodes a unique 14-kilodalton polypeptide.

Marek's disease virus (MDV) is an oncogenic avian herpesvirus whose genomic structure is similar to those of herpes simplex virus and varicella-zoster virus. Repeat regions of the MDV genome have been intensively investigated because of a potential relationship to MDV oncogenicity and abundant expression of immediate-early transcripts. In this study, a 1.6-kb immediate-early transcript was localized to the BamHI-I2 region by Northern (RNA) hybridization analysis. With cDNA cloning and sequencing, two cDNAs of 1.4 kb (C1) and 1.35 kb (C2) were identified. Both cDNAs are derived from spliced mRNAs spanning the BamHI-H and -I2 fragments. C1 and C2 use the same splice acceptors and 3' ends, but they differ at their 5' ends and utilize different splice donors. The upstream promoter-enhancer region of C1 cDNA has been defined as a bidirectional regulatory region shared by the MDV pp38 gene. Sequencing analysis shows two small open reading frames (ORFs) within each cDNA (ORF1a and ORF2 in C1, ORF1b and ORF2 in C2). Potential ORFs of the sequence have no significant homology with any known protein in the Swiss-Protein data base. DNA fragments encoding ORF1a and ORF1b were cloned into pGEX-3X vectors to produce glutathione S-transferase fusion proteins and induce antisera. In Western blot (immunoblot) analysis of MDV-infected-cell lysates, a 14-kDa polypeptide was identified by antisera against both ORF1a and ORF1b. This 14-kDa protein is expressed in cells which are lytically infected with MDV strains GA, Md11 passage 14 (oncogenic), and Md11 passage 83 (attenuated), as well as in the latently MDV-infected and transformed MSB-1 cell line.

Amino Acid Sequence↗
PubMed2003

The regulation of hepatitis C virus (HCV) internal ribosome-entry site-mediated translation by HCV replicons and nonstructural proteins.

Hepatitis C virus (HCV), the global leading cause of chronic liver disease, has a positive-sense, ssRNA genome that encodes a large polyprotein. HCV polyprotein translation is initiated by an internal ribosome-entry site (IRES) located at the 5' end of the viral genome, in a cap-independent manner, but the regulatory mechanism of this process remains poorly understood. In this study, we characterized the effect of HCV nonstructural proteins on HCV IRES-directed translation in both HCV replicon cells and transiently transfected human liver cells expressing HCV nonstructural proteins. Using bicistronic reporter gene constructs carrying either HCV or other viral IRES sequences, we found that the HCV IRES-mediated translation was specifically upregulated in HCV replicon cells. This enhancement of HCV IRES-mediated translation by the replicon cells was inhibited by treatment with either type I interferon or ribavirin, drugs that perturb HCV genome replication, suggesting that the enhancement is probably due to HCV-encoded protein function(s). Reduced phosphorylation levels of both eIF2alpha and eIF4E were observed in the replicon cells, which is consistent with our previous findings and indicates that the NS5A nonstructural protein may be involved in the regulatory mechanism(s). Indeed, transient expression of NS5A or NS4B in human liver cells stimulated HCV IRES activity. Interestingly, mutation in the ISDR of NS5A perturbed this stimulation of HCV IRES activity. All these results suggest, for the first time, that HCV nonstructural proteins preferentially stimulate the viral cap-independent, IRES-mediated translation.

Antiviral Agents↗
PubMed1984

Early events in the infection of human B lymphocytes by Epstein-Barr virus: the internalization process.

The early events in the infection of normal B lymphocytes and B lymphoblastoid cells by Epstein-Barr virus (EBV) were examined by electron and immunoelectron microscopy and by infectivity and inhibition studies. Purified EBV remained on the cell surface at 4 degrees and appeared as 250-nm ovoid particles in contact with the cell membrane through 50-nm envelope projections. Internalization of EBV in normal B lymphocytes into large (300-500 nm) uncoated vacuoles was initiated within 2 to 5 min at 37 degrees. At this stage approximately 1/3 of cell-associated virus was located in cellular invaginations while another 1/3 was in cell vacuoles. Direct fusion of EBV with the outer cell membrane was not observed. Instead, viral deenvelopment and nucleocapsid transit into the cytoplasm occurred from the large endocytic vesicles within 15 to 30 min at 37 degrees and did not involve lysosomal enzymes. During this time, the viral envelope became amorphous and its separation from the nucleocapsid was evident. After 60 to 90 min at 37 degrees, viral nucleocapsids were visualized in close proximity to the cell nucleus. Weak bases such as chloroquine, methylamine, and ammonium chloride retarded viral deenvelopment and fusion inside the endocytic vacuoles, resulting in abrogation of viral infectivity and accumulation of intact virions within cell vacuoles. These studies indicate that EBV enters normal B lymphocytes by a different endocytic pathway than the clathrin-receptosome-lysosome pathway utilized by many other ligands, including a number of viruses, to enter cells. In contrast to the pathway of entry into normal B lymphocytes, EBV entered B lymphoblastoid cells by direct fusion with the outer cell membrane within 2 to 5 min at 37 degrees.

B-Lymphocytes↗
PubMed1991

Effect of polyions on the early events of Sindbis virus infection of Vero cells.

To clarify the role of electrostatic interactions in the binding of Sindbis virus (SNV) to cell membrane receptors, we investigated the effect of different polyions on the initial steps of infection of Vero cells by the virus. Several polyanions (mucin, heparin, polygalacturonic acid) and polycations (polylysine, protamine, polybrene) were able to reduce the replication of SNV when present in the viral adsorption period, whereas others (chondroitin sulfate, polymyxin B sulfate, histone) were devoid of any activity. Therefore the electric charge alone is not sufficient to explain the action of compounds. The effects of polyions on receptor binding, on bound virus, and on internalized virus have been examined. All the drugs inhibited SNV infection by affecting its binding to the cellular receptor. The results indicated that heparin and mucin act directly on the virus particle while polycations bind to the cell membrane receptor for the virus, protamine being effective on both targets. Since among polyanions glycosaminoglycans showed a strong inhibiting activity, the involvement of these molecules in the virus surface receptor was assessed by enzyme digestion of cell membrane with heparinase and chondroitin ABC lyase.

Animals↗
PubMed2006

Hepatitis C virus-related internal ribosome entry sites are found in multiple genera of the family Picornaviridae.

The internal ribosome entry site (IRES) elements from porcine enterovirus 8 and simian virus 2, two members of a proposed new genus within the family Picornaviridae, were characterized. These IRES elements, in common with the porcine teschovirus 1 IRES, were found to be related functionally and structurally to the IRES element from Hepatitis C virus, a member of the family Flaviviridae. Partial secondary structure predictions were derived and functional assays demonstrated that these IRES elements continued to be active when eIF4G was cleaved and when the activity of eIF4A was blocked.

5' Untranslated Regions↗
PubMed2004

Intracellular inhibition of hepatitis C virus (HCV) internal ribosomal entry site (IRES)-dependent translation by peptide nucleic acids (PNAs) and locked nucleic acids (LNAs).

Hepatitis C virus (HCV) is the major etiological agent of non-A, non-B hepatitis. Current therapies are not effective in all patients and can result in the generation of resistant mutants, leading to a need for new therapeutic options. HCV has an RNA genome that contains a well-defined and highly conserved secondary structure within the 5'-untranslated region. This structure is known as the internal ribosomal entry site (IRES) and is necessary for translation and viral replication. Here, we test the hypothesis that antisense peptide nucleic acid (PNA) and locked nucleic acid (LNA) oligomers can bind key IRES sequences and block translation. We used lipid-mediated transfections to introduce PNAs and LNAs into cells. Our data suggest that PNAs and LNAs can invade critical sequences within the HCV IRES and inhibit translation. Seventeen base PNA or LNA oligomers targeting different regions of the HCV IRES demonstrated a sequence-specific dose-response inhibition of translation with EC(50) values of 50-150 nM. Inhibition was also achieved by PNAs ranging in length from 15 to 21 bases. IRES-directed inhibition of gene expression widens the range of mechanisms for antisense inhibition by PNAs and LNAs and may provide further therapeutic lead compounds for the treatment of HCV.

5' Untranslated Regions↗
PubMed2005

A hepatitis C virus (HCV) internal ribosome entry site (IRES) domain III-IV-targeted aptamer inhibits translation by binding to an apical loop of domain IIId.

The hepatitis C virus (HCV) has a positive single-stranded RNA genome, and translation starts within the internal ribosome entry site (IRES) in a cap-independent manner. The IRES is well conserved among HCV subtypes and has a unique structure consisting of four domains. We used an in vitro selection procedure to isolate RNA aptamers capable of binding to the IRES domains III-IV. The aptamers that were obtained shared the consensus sequence ACCCA, which is complementary to the apical loop of domain IIId that is known to be a critical region of IRES-dependent translation. This convergence suggests that domain IIId is preferentially selected in an RNA-RNA interaction. Mutation analysis showed that the aptamer binding was sequence and structure dependent. One of the aptamers inhibited translation both in vitro and in vivo. Our results indicate that domain IIId is a suitable target site for HCV blockage and that rationally designed RNA aptamers have great potential as anti-HCV drugs.

5' Untranslated Regions↗
PubMed1975

Amino acid sequence homology of mammalian type C RNA virus major internal proteins.

The NH2-terminal amino acid sequence of the major group-specific antigen, the major internal virion protein (p30; approximate molecular weight 30,000) of several mammalian type C RNA viruses was determined by the Edman degradation procedure using an automated protein sequenator. All of the proteins analyzed show a high degree of over-all sequence homology and also contain specific regions or single residues. All p30s begin with the sequence prolyl-leucylarginyl (Pro-Leu-Arg) and have an invariant, conserved region from residues 11 to 24. In this region only a single amino acid difference appears between the cat and mouse p30s. At position 17 alanine is found in the cat, and serine in all the mouse proteins. This homologous region starts at position 10 for RD-114 and baboon virus p30s, and at position 18 in the protein of the virus isolated from gibbon ape. The region extending from residue 4 to 10 shows considerable variability between p30s isolated from different mammalian species. Out of 24 residues compared, only a single amino acid difference was found between six different mouse p30s. At position 4, three have leucine, two have alanine, and one has serine. The comparative sequence data demonstrate that the viral p30s are products of related genes in the viruses from various mammalian species.

Amino Acid Sequence↗
PubMed1999

Virus-specific cell receptors are necessary, but not sufficient, to confer cell susceptibility to African swine fever virus.

The entry of African swine fever (ASF) virus into Vero cells and swine macrophages is mediated by saturable binding sites located in the plasma membrane, which have been related, as in other virus-cell systems, to the sensitivity of the cell to the virus. In order to define this correlation, we have analyzed up to 16 cell lines derived from different species for their sensitivity to virus infection, to determine the step in the virus infective cycle that was blocked in each resistant cell, the presence of saturable cell receptors and the percentage of bound and internalized virus in these cells. Specific ASF virus receptors were found in different quantities in many sensitive and resistant cell lines. The most restricted cells showed a reduced efficiency of virus binding and virus internalization, as well as a lower amount of cell receptors for the virus attachment protein p12. Other resistant cells were restricted only after early virus translation or virus DNA replication, proving that the presence of virus-specific receptors may be necessary, but not sufficient, to guarantee the cell permissiveness to the virus, and that the ASF virus infection can be arrested at different steps on the infective cycle.

African Swine Fever Virus↗
PubMed2004

Virological effects of ISIS 14803, an antisense oligonucleotide inhibitor of hepatitis C virus (HCV) internal ribosome entry site (IRES), on HCV IRES in chronic hepatitis C patients and examination of the potential role of primary and secondary HCV resistance in the outcome of treatment.

Antisense oligonucleotides represent a promising class of antiviral agents. ISIS 14803 is a 20-unit phosphorothioate oligodeoxynucleotide that inhibited hepatitis C virus (HCV) replication and protein expression in cell culture and mouse models. A Phase I dose-escalation clinical study of ISIS 14803 was performed in 24 patients with HCV genotype 1 chronic hepatitis C. The patients received 0.5, 1.0, 2.0 or 3.0 mg/kg of ISIS 14803 for 4 weeks. Two of them receiving 2.0 mg/kg, experienced a significant (>1.0 log10) viral load reduction and nine other patients experienced minor (<1.0 log10) viral load reductions that were difficult to definitively distinguish from assay or patient variations. The aims of this study were to examine the effect of ISIS 14803 on its target site and neighbouring region quasispecies evolution, and to determine whether primary and secondary HCV resistance contributed to the observed virological response rate. The HCV internal ribosome entry site (IRES), including the ISIS 14803 target site in virus specimens collected from patients at baseline and end-of-treatment, was sequenced. An extensive IRES quasispecies analysis was performed in 10 of the patients at various time points before, during and after ISIS 14803 treatment. A significant IRES genetic evolution was found in three out of 10 patients through quasispecies analysis suggesting that treatment with ISIS 14803, a drug designed to bind to HCV RNA, exerted a selective pressure on HCV IRES. However, no mutations in the ISIS 14803 target site, which would inhibit binding of the oligonucleotide to HCV RNA, were detected before (primary resistance) or after treatment (secondary resistance) with the oligonucleotide. Furthermore, no obvious nucleotide changes in the surrounding IRES region that might possibly affect oligonucleotide binding were detected.

5' Untranslated Regions↗
PubMed1997

Requirements for different components of the host cell cytoskeleton distinguish ecotropic murine leukemia virus entry via endocytosis from entry via surface fusion.

Murine ecotropic leukemia viruses use a common receptor for entry into host cells; however, the site of virus fusion appears to differ with the host cell. Entry in mouse NIH 3T3 fibroblasts is by endocytosis, whereas entry in rat XC sarcoma cells is by surface fusion. We report here the identification of a step common to both entry pathways, as well as of a step unique to the endocytic pathway. Recent demonstration of the clustering of the virus receptor on rat cells suggested a possible interaction of the receptor with the cellular cytoskeleton (M. H. Woodard, W. A. Dunn, R. O. Laine, M. Malandro, R. McMahon, O. Simell, E. R. Block, and M. S. Kilberg, Am. J. Physiol. 266:E817-E824, 1994). We tested the hypothesis that such an interaction might influence receptor function. We found that entry into NIH 3T3 and XC cells was greatly diminished by the disruption of the actin network before but not shortly after virus internalization, suggesting the actin network plays a critical role in an early step common to both entry pathways. Disruption of microtubules before and shortly after virus internalization markedly reduced entry in NIH 3T3 cells, while entry into XC cells remained efficient. These data suggest that intact microtubules are required in a postpenetration step unique to efficient virus entry via endocytosis. The physiological function of the receptor was not affected by disruption of either the actin network or the microtubules, as the uptake of cationic amino acids in NIH 3T3 and XC cells was comparable to that in control cells even when the cytoskeleton remained disrupted for as long as 3 h.

3T3 Cells↗
PubMed1994

Internalization of virus binding proteins during entry of reovirus into K562 erythroleukemia cells.

Virus overlay protein blot assays of cell membranes of mouse L929 fibroblasts have revealed multiple reovirus binding proteins with molecular masses ranging from approximately 26 to 200 kDa. To determine whether this observation is unique to L cells, membranes of human K562 erythroleukemia cells and human A431 epidermoid cells were subjected to virus overlay protein blot assays. The profiles of reovirus binding proteins of these cells are similar to that of L cells and reovirus is capable of binding to at least 30 membrane proteins. To determine the fate of reovirus binding proteins during viral entry into K562 cells which are infectible by reovirus, cell surface proteins were derivatized with biotin. During viral entry, biotinylated cell surface proteins with molecular masses of 55, 74, 78, 80, 90, 94, 98, and 115 kDa became internalized. The 90- and 115-kDa proteins also bound reovirus, indicating that they are likely to be reovirus receptors. Thus many virus binding proteins are present at the surface of host cells but very few are internalized during entry of reovirus. K562 cells also express glycophorin A which is the putative reovirus receptor on erythrocytes. However, during entry of reovirus into K562 cells, glycophorin A did not appear to become internalized. Reovirus could be shown to attach to erythrocytes but viral entry into these cells could not be demonstrated.

Animals↗
PubMed1982

Temperature-dependent internalization of virus glycoproteins in cells infected with a mutant of Semliki Forest virus.

When the ts-1 mutant of Semliki Forest virus (SFV) was grown in chick embryo or BHK 21 cells at the restrictive temperature (39 degrees C), its membrane glycoproteins were arrested in the endoplasmic reticulum, but started to migrate to the cell surface once the cultures were shifted to the permissive temperature (28 degrees C). If the temperature of infected cells was raised back to 39 degrees C, ts-1 glycoproteins disappeared from the cell surface as evidenced by loss of surface immunofluorescence and by radioimmunoassay based on the binding of 125I-labeled protein A. This phenomenon was specific for ts-1 at 39 degrees C as it was observed neither in cells infected with wild-type SFV at 39 degrees C nor with ts-1 at 28 degrees C. The disappearance of the ts-1 glycoproteins was due to internalization. The internalized proteins were digested, as shown by specific decrease of virus glycoproteins labelled with [35S]methionine at 39 degrees C before shift to 28 degrees C, and by concomitant release of acid soluble 35S-activity into the culture medium. Ts-1 infected cells were treated before shift back to 39 degrees C with Fab' fragments, prepared from IgG against the viral membrane glycoproteins. After shift back to 39 degrees C, the Fab' fragments disappeared from the cell surface. In the presence of chloroquine, they could be visualized in vesicular structures, using an anti-IgG-fluorescein isothiocyanate conjugate. The internalization of ts-1 glycoproteins was not inhibited by carbonylcyanide p-trifluoromethoxy phenylhydrazone, chloroquine, cytochalasin B, vinblastine, colcemid, or monensin.

Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone↗
PubMed1983

Ultrastructural and immunofluorescence studies of early events in adenovirus-HeLa cell interactions.

Scanning electron microscopy and immunofluorescence techniques show that the attachment of adenovirus type 5 to HeLa cells is followed by a temperature-dependent redistribution of virus particles on the cell surface. Metabolic inhibitors and cytochalasin B, a drug that impairs microfilament function, blocked this redistribution. Transmission electron microscopy studies demonstrated that inhibition of redistribution was paralleled by an inhibition of virus internalization. In further experiments virus and cells were incubated at 4 degrees C and then treated with adenovirus 'soluble' antigens to block unoccupied virus receptors. On warming these preparations to 37 degrees C, the internalization of attached virions was found to be impaired. It is proposed that energy-dependent redistribution of attached adenovirus particles on the cell surface facilitates entry by bringing virions into contact with sufficient receptors to allow internalization.

Adenoviruses, Human↗
PubMed1988

Differential ability of B cells specific for external vs. internal influenza virus proteins to respond to help from influenza virus-specific T-cell clones in vivo.

When a helper T-cell (TH) clone specific for the hemagglutinin, neuraminidase, matrix protein, or nucleoprotein of influenza strain A/PR/8/34 is adoptively transferred to athymic mice 1 day after virus infection the anti-viral antibody response of the mouse is enhanced. This response is directed predominantly to the hemagglutinin and requires associative T-cell-B-cell interactions. Delaying transfer of the TH clone has three consequences: (i) the onset of the anti-hemagglutinin antibody response is delayed; (ii) the titer of the anti-hemagglutinin response is reduced; and (iii) the titer of the antibody in the response against the internal proteins, matrix protein and nucleoprotein, is enhanced upon transfer of matrix protein- or nucleoprotein-specific, but not hemagglutinin- or neuraminidase-specific, TH clones. Thus, there is a hierarchy of help: B cells recognizing viral surface components, hemagglutinin or neuraminidase, can receive help from TH clones specific for any of the major structural viral proteins. In contrast, B cells responding to internal viral components, matrix protein or nucleoprotein, are restricted to receiving help almost exclusively from TH clones with the same protein specificity. These observations suggest that, upon B-cell surface immunoglobulin-antigen interaction and uptake of intact virus, B cells specific for viral surface proteins process and present all major structural viral antigens, enabling the B cells to interact with TH clones specific for any virion protein. B cells recognizing internal viral components, which may be accessible to interaction with B-cell immunoglobulin receptors mainly as free proteins, would present only the protein for which they are specific and, thereby, receive help only from the TH clones of the same protein specificity.

Animals↗
PubMed1998

Coxsackie B virus and its interaction with permissive host cells.

BACKGROUND: Observations in humans and the results of experiments on laboratory animals have provided evidence that coxsackieviruses of group B (CVB) are major etiologic agents of acute and chronic enterovirus myocarditis and various other virus-induced diseases. OBJECTIVE: This minireview briefly summarizes the investigations to elucidate various molecular mechanisms for the induction and maintenance of persistent CVB infections. With regard to the recent findings that CVB may use several different receptor proteins, this article focuses on virus-host cell interactions and the potential impact of these interactions for enteroviral replication. STUDY DESIGN: The interaction of CVB with specific cell surface proteins was analyzed in cultured cell lines and murine tissues at the level of virus attachment and virus internalization. As example for the interaction of CVB with intracellular proteins, the state of p21rasGTPase-activating protein (RasGAP) was investigated in mock-infected and CVB3-infected HeLa cells. RESULTS AND CONCLUSIONS: The experiments to elucidate the virus receptor interactions revealed the necessity to differentiate between CVB attachment proteins and proteins involved in virus internalization. Since more than one protein may be required to initiate the uptake of CVB into permissive host cells, a model of the putative interaction of these proteins within a multimeric receptor complex is proposed. It is further tempting to speculate that the presence of multiple attachment proteins may influence the tissue tropism of CVB as well as pathogenicity.

Animals↗