SEARCH · PubMed Health

Results for “Viral Structures”

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 865 records · Page 48Linked to original sources

PubMed1989

Inhibition of human immunodeficiency virus type 1-mediated cytopathic effects by poly(L-lysine)-conjugated synthetic antisense oligodeoxyribonucleotides.

The ability of poly(L-lysine)-conjugated and methylphosphonate-modified synthetic human immunodeficiency virus type 1 (HIV-1) antisense oligodeoxyribonucleotides to protect susceptible host cells from the cytopathic effects of HIV-1 infection was studied. The abundance of viral antigens in oligomer-treated cultures indicated that the oligomers did not significantly affect viral infectivity. Similarly, no significant effects on relative viral RNA accumulation were apparent. The presence of poly(L-lysine)-modified oligomer complementary to the HIV-1 splice donor site resulted in a significant reduction in the production of viral structural proteins and virus titre in infected cultures. In addition, these cells were protected from HIV-1-mediated cytopathic effects while the other cultures rapidly succumbed to the cytotoxic effects of HIV-1 infection. The presence of poly(L-lysine)-conjugated oligomer resulted in the establishment of a persistent HIV-1 infection characterized by a highly productive virus infection in the absence of cell death while treatment of persistently infected cells with phorbol ester resulted in renewed cytopathicity. These results demonstrate the ability of synthetic antisense oligonucleotides to protect susceptible host cells from the cytopathic effects of HIV-1 infection.

Blotting, Northern↗

PubMed1993

Expression of the Bunyamwera virus M genome segment and intracellular localization of NSm.

Bunyamwera (BUN) virus is the prototype of the family Bunyaviridae and contains a trisegmented, single-stranded RNA genome of negative polarity. The medium (M) RNA segment encodes the two virion glycoproteins, G1 and G2, and a nonstructural protein, NSm, in the form of a polyprotein precursor which is cotranslationally cleaved. The gene order of the M segment is 5' G2-NSm-G1 3'. We have raised a monospecific antiserum in rabbits to a branched chain synthetic peptide to a region of the NSm protein which specifically immunoprecipitates NSm from BUN-infected cells. Indirect immunofluorescence experiments on BUN-infected cells using this antiserum gave a perinuclear staining pattern, suggesting that like the viral structural proteins, NSm localizes to the Golgi complex. An essentially full-length M segment cDNA was cloned into a recombinant vaccinia virus under control of bacteriophage T7 promoter and terminator sequences and expressed in cells co-infected with a second recombinant vaccinia virus which synthesizes T7 RNA polymerase. G1, G2, and NSm were detected in cells dually infected with the recombinant vaccina viruses, indicating that processing of the M segment-encoded precursor does not require other BUN proteins. Immunofluorescence experiments showed that the BUN glycoproteins expressed from this recombinant vaccinia virus system localized to the Golgi complex like authentic BUN proteins.

Amino Acid Sequence↗

PubMed2006

The cytoplasmic tail of the severe acute respiratory syndrome coronavirus spike protein contains a novel endoplasmic reticulum retrieval signal that binds COPI and promotes interaction with membrane protein.

Like other coronaviruses, severe acute respiratory syndrome coronavirus (SARS CoV) assembles at and buds into the lumen of the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC). Accumulation of the viral envelope proteins at this compartment is a prerequisite for virus assembly. Previously, we reported the identification of a dibasic motif (KxHxx) in the cytoplasmic tail of the SARS CoV spike (S) protein that was similar to a canonical dilysine ER retrieval signal. Here we demonstrate that this motif is a novel and functional ER retrieval signal which reduced the rate of traffic of the full-length S protein through the Golgi complex. The KxHxx motif also partially retained two different reporter proteins in the ERGIC region and reduced their rates of trafficking, although the motif was less potent than the canonical dilysine signal. The dibasic motif bound the coatomer complex I (COPI) in an in vitro binding assay, suggesting that ER retrieval may contribute to the accumulation of SARS CoV S protein near the virus assembly site for interaction with other viral structural proteins. In support of this, we found that the dibasic motif on the SARS S protein was required for its localization to the ERGIC/Golgi region when coexpressed with SARS membrane (M) protein. Thus, the cycling of SARS S through the ER-Golgi system may be required for its incorporation into assembling virions in the ERGIC.

Amino Acid Motifs↗

PubMed2006

African swine fever virus pB119L protein is a flavin adenine dinucleotide-linked sulfhydryl oxidase.

Protein pB119L of African swine fever virus belongs to the Erv1p/Alrp family of sulfhydryl oxidases and has been described as a late nonstructural protein required for correct virus assembly. To further our knowledge of the function of protein pB119L during the virus life cycle, we have investigated whether this protein possesses sulfhydryl oxidase activity, using a purified recombinant protein. We show that the purified protein contains bound flavin adenine dinucleotide and is capable of catalyzing the formation of disulfide bonds both in a protein substrate and in the small molecule dithiothreitol, the catalytic activity being comparable to that of the Erv1p protein. Furthermore, protein pB119L contains the cysteines of its active-site motif CXXC, predominantly in an oxidized state, and forms noncovalently bound dimers in infected cells. We also show in coimmunoprecipitation experiments that protein pB119L interacts with the viral protein pA151R, which contains a CXXC motif similar to that present in thioredoxins. Protein pA151R, in turn, was found to interact with the viral structural protein pE248R, which contains disulfide bridges and belongs to a class of myristoylated proteins related to vaccinia virus L1R, one of the substrates of the redox pathway encoded by this virus. These results suggest the existence in African swine fever virus of a system for the formation of disulfide bonds constituted at least by proteins pB119L and pA151R and identify protein pE248R as a possible final substrate of this pathway.

African Swine Fever Virus↗

PubMed1989

Identification of L2 open reading frame gene products of bovine papillomavirus type 1 using monoclonal antibodies.

Four hybridoma cell lines producing monoclonal antibodies (MAbs) to bovine papillomavirus type 1 (BPV-1) L2 open reading frame (ORF) gene products have been established from mice immunized with a BPV-1 L2-beta-galactosidase fusion protein. Hybridomas were selected and cloned (from over 700 hybridomas) on the basis of specific reactivity of supernatant fluids with BPV-1 L2 epitopes on disrupted BPV-1 particles and L2-beta-galactosidase fusion proteins by ELISA and Western blotting, and with acetone-fixed frozen sections of BPV-1-induced fibropapillomas by immunofluorescence. These MAbs were not reactive with intact BPV-1 particles or BPV-1 L1-beta-galactosidase fusion proteins by ELISA or with beta-galactosidase by ELISA and Western blotting. The four MAbs detected viral structural proteins of Mr 76K, 68K and possibly 55K in purified BPV-1 preparations by Western blotting. Two of the four MAbs were cross-reactive with BPV-2-induced fibropapillomas. These findings suggest that (i) the BPV-1 L2 ORF encodes the minor capsid protein(s), (ii) the gene products of the BPV-1 L2 ORF have Mr values of 76K, 68K and possibly 55K, (iii) minor capsid epitopes are internal to the BPV-1 particle, and (iv) MAbs reactive with genetically engineered truncated BPV-1 L2 ORF gene products can distinguish between BPV-1 and BPV-2 productive infections.

Animals↗

PubMed1992

T lymphocyte responses of sheep to bovine leukaemia virus infection.

Sheep were experimentally infected with bovine leukaemia virus (BLV) by inoculation of peripheral blood lymphocytes (PBL) from BLV infected sheep. Monoclonal antibodies were used to monitor changes in lymphocyte subpopulations in the first few weeks after inoculation. The polymerase chain reaction (PCR) detected BLV DNA in PBL of infected sheep 11-15 days after inoculation, that is, before antibodies to viral structural proteins were detected at 15-39 days post-inoculation. A rise in the number of both B and T lymphocytes coincided with detection of infection by PCR. At this time, an increase in the number of circulation CD8+ lymphocytes resulted in a low CD4: CD8 ratio. It appears that in BLV infection there is a host specific cell-mediated immune response to infected lymphocytes rather than a general immune response to foreign antigens. This response, which is characterized by an increase in the number of circulating CD8+ lymphocytes, precedes seroconversion. There is considerable variation between animals in this cytotoxic T lymphocyte response.

Animals↗

PubMed1986

An aberration in gamma-ray-enhanced reactivation of irradiated adenovirus in ataxia telangiectasia fibroblasts.

Ataxia telangiectasia (AT) is a rare human genetic disorder, whose numerous clinical hallmarks include a predisposition to lymphoreticular cancers and a hypersensitivity to conventional radiotherapy. Furthermore, AT cells in vitro exhibit a hypersensitivity to ionising radiation that appears to be correlated with an increased frequency of chromosomal aberrations, a resistance of de novo DNA synthesis to inhibition by radiation-induced DNA damage, a reduced mitotic delay and possible defects in DNA repair. In this study, a sensitive viral assay has been used to investigate the capacity of gamma-irradiated AT cells to support the replication of undamaged virus, as well as the extent to which the survival of radiation-damaged virus was affected by gamma-irradiation of these host cells prior to infection. The expression of such enhanced reactivation (ER) of both u.v.-irradiated (u.v. dose = 1.2 X 10(3) J/m2) and gamma-irradiated (dose = 2 Mrad) adenovirus type 2 (Ad2) was examined in a variety of normal and AT human fibroblast strains. Unirradiated and gamma-irradiated fibroblasts were infected with unirradiated or irradiated Ad2, either immediately or at different times after cell monolayer irradiation, and at 48 h after infection cultures were examined by indirect immunofluorescence to determine the number of cells in which Ad2 viral structural antigen (Vag) was expressed. For immediate infection of normal human fibroblasts, both a decrease in unirradiated virus expression and an increase in ER were observed with increasing gamma-ray dose to the cells. In contrast, AT fibroblasts were found to be deficient in gamma-ray ER of irradiated Ad2, and this defect appeared to be related to a marked relative radioresistance of unirradiated virus expression in AT compared to normal cells. The potential significance of these results is discussed in the context of mammalian ER, which is believed to be, at least in part, an expression of a mutagen-inducible (and possibly error-prone) DNA repair mechanism.

Adenoviruses, Human↗

PubMed1990

Vectors, promoters, and expression of genes in chick embryos.

Transgenic chickens were produced by injecting the Day-1 egg with 10(5) infectious particles of a replication-competent virus based on the Schmidt-Ruppin A strain of Rous sarcoma virus. The chickens were resistant to transforming subgroup A virus containing the src gene but not the corresponding subgroup B virus. Transgenic chickens producing bovine growth hormone (bGH) were generated using a modified virus containing the Bryan high titre polymerase gene. The virus was constructed with the bGH gene and the mouse metallothionein promoter in the reverse orientation relative to the viral structural genes. Two male chickens produced serum concentrations of approximately 100 ng bGH/ml; the birds were larger than controls and matured more rapidly. Transgenic mice required for the analysis of skeletal muscle-specific expression in vivo were produced using 5'-flanking regions of the chicken alpha-skeletal actin promoter linked to a luciferase reporter gene to determine the region essential for tissue-specific expression. The defined promoter sequences are to be used in experiments designed to direct expression of growth-promoting genes in skeletal muscle of chickens.

Animals↗

PubMed1974

Expression of the major internal viral polypeptide in cells transformed by wild-type and temperature-sensitive murine sarcoma virus.

Phenotypic expression of the murine intraspecies and interspecies antigenic determinants of the major type C viral structural 30,000-dalton polypeptide, p30, was measured by radioimmunoassay inhibition in cell lines from different species. Uninfected normal rat kidney (NRK) cells did not contain detectable levels of murine intraspecies and interspecies p30 antigen, whereas rat cells transformed by and producing murine sarcoma virus (MSV)-Moloney leukemia virus (M-MSV-MuLV) contained high levels of both murine intraspecies and interspecies p30 antigen. Significant amounts of murine intraspecies and interspecies p30 antigen were detected in wild-type MSV-transformed nonproducer NRK cells. The control of p30 antigen expression was examined in temperature-sensitive MSV-transformed nonproducer cells [NRK(MSV-1b)] which are cold sensitive for maintenance of the transformed phenotype. Both murine intraspecies and interspecies p30 antigens were detected in NRK(MSV-1b) cells when grown at the permissive (39 C) or nonpermissive (33 C) temperature, suggesting that p30 antigen expression is not correlated with maintenance of the transformed phenotype. The results demonstrate that previously undetectable p30 antigens are expressed in MSV-transformed nonproducer NRK cells, and suggest that the expression of p30 antigen may be a useful marker for viral gene expression in mammalian cells.

Animals↗

PubMed1988

RNA recombination of murine coronaviruses: recombination between fusion-positive mouse hepatitis virus A59 and fusion-negative mouse hepatitis virus 2.

It has previously been shown that the murine coronavirus mouse hepatitis virus (MHV) undergoes RNA recombination at a relatively high frequency in both tissue culture and infected animals. Thus far, all of the recombination sites had been localized at the 5' half of the RNA genome. We have now performed a cross between MHV-2, a fusion-negative murine coronavirus, and a temperature-sensitive mutant of the A59 strain of MHV, which is fusion positive at the permissive temperature. By selecting fusion-positive viruses at the nonpermissive temperature, we isolated several recombinants containing multiple crossovers in a single genome. Some of the recombinants became fusion negative during the plaque purification. The fusion ability of the recombinants parallels the presence or absence of the A59 genomic sequences encoding peplomers. Several of the recombinants have crossovers within 3' end genes which encode viral structural proteins, N and E1. These recombination sites were not specifically selected with the selection markers used. This finding, together with results of previous recombination studies, indicates that RNA recombination can occur almost anywhere from the 5' end to the 3' end along the entire genome. The data also show that the replacement of A59 genetic sequences at the 5' end of gene C, which encodes the peplomer protein, with the fusion-negative MHV-2 sequences do not affect the fusion ability of the recombinant viruses. Thus, the crucial determinant for the fusion-inducing capability appears to reside in the more carboxyl portion of the peplomer protein.

Base Sequence↗

PubMed2006

Diverse effects of cyclosporine on hepatitis C virus strain replication.

Recently, a production system for infectious particles of hepatitis C virus (HCV) utilizing the genotype 2a JFH1 strain has been developed. This strain has a high capacity for replication in the cells. Cyclosporine (CsA) has a suppressive effect on HCV replication. In this report, we characterize the anti-HCV effect of CsA. We observe that the presence of viral structural proteins does not influence the anti-HCV activity of CsA. Among HCV strains, the replication of genotype 1b replicons was strongly suppressed by treatment with CsA. In contrast, JFH1 replication was less sensitive to CsA and its analog, NIM811. Replication of JFH1 did not require the cellular replication cofactor, cyclophilin B (CyPB). CyPB stimulated the RNA binding activity of NS5B in the genotype 1b replicon but not the genotype 2a JFH1 strain. These findings provide an insight into the mechanisms of diversity governing virus-cell interactions and in the sensitivity of these strains to antiviral agents.

Amino Acid Sequence↗

PubMed2005

Capsid-targeted viral inactivation can destroy dengue 2 virus from within in vitro.

Capsid-targeted viral inactivation (CTVI) has emerged as a conceptually powerful antiviral strategy that exploits viral structural proteins to target a destructive enzyme specifically into progeny virions. We have recently demonstrated the principle of CTVI against dengue virus infection and observed a modest therapeutic effect in vitro (Arch Virol 2005, 150: 659-669). Here we tested a prophylactic model of CTVI, in which mammalian cells stably expressing the dengue 2 virus capsid protein fused to a nuclease were infected with dengue virus and determined the effects on progeny virion infectivity. CTVI efficiently destroyed dengue 2 virus from within and decreased the infectious titers by 10(3)- to 10(4)-fold, suggesting that CTVI has potential in the prophylactic application for dengue virus infection.

Animals↗

PubMed1970

Transcription in vitro by reovirus-associated ribonucleic acid-dependent polymerase.

Digestion of purified reovirus type 3 with chymotrypsin degrades 70% of the viral protein and converts the virions to subviral particles (SVP). The SVP contain 3 of the 6 viral structural proteins and all 10 double-stranded ribonucleic acid (RNA) genome segments but not adenine-rich, single-stranded RNA. An RNA polymerase which is structurally associated with SVP transcribes one strand of each genome segment by a conservative mechanism in vitro. The single-stranded products include large (1.2 x 10(6) daltons), medium (0.7 x 10(6) daltons), and small (0.4 x 10(6) daltons) molecules which hybridize exclusively with the corresponding genome segments. The enzyme obtained by heating virions at 60 C synthesizes similar products. Kinetic and pulse-chase studies indicate that the different-sized products are synthesized simultaneously but at rates which are in the order: small > medium > large.

Acrylates↗

PubMed1997

The human T-cell leukemia virus type 1 Rex regulatory protein exhibits an impaired functionality in human lymphoblastoid Jurkat T cells.

The Rex protein of human T-cell leukemia virus type 1 (HTLV-1) intervenes in the posttranscriptional regulation of proviral gene expression. Its binding to the Rex response element (XRE) present in the 3' long terminal repeat ensures the coordinate cytoplasmic accumulation of spliced and unspliced forms of viral messengers. Consequently, synthesis of viral structural and enzymatic proteins is strictly dependent on the Rex posttranscriptional activity. Here we report that synthesis of HTLV-1 envelope glycoproteins by Jurkat T cells could be detected only when they were regulated in a Rex-independent manner. Indeed, Jurkat T cells transfected with a Rex-dependent env expression vector (encompassing both the env and pX open reading frames) do not produce significant levels of envelope glycoproteins despite the production of significant amounts of Rex protein. The analysis of levels and distribution patterns of the unspliced env and of the singly spliced tax/rex transcripts suggests that the failure in envelope glycoprotein synthesis may be ascribed to a deficiency of Rex in mediating the nucleocytoplasmic transport of unspliced env RNAs in these cells. Furthermore, despite the synthesis of regulatory proteins, HTLV-1 structural proteins were not detected in Jurkat T cells transfected with an HTLV-1 infectious provirus. Conversely, and as expected, structural proteins were produced by Jurkat cells transfected by a human immunodeficiency virus type 1 (HIV-1) infectious provirus. This phenotype appeared to be linked to a specific dysfunction of Rex, since the functionally equivalent Rev protein of HIV-1 was shown to be fully efficient in promoting the synthesis of HTLV-1 envelope glycoproteins in Jurkat cells. Therefore, it seems likely that the block to Rex function in these lymphoblastoid T cells is determined by inefficient Rex-XRE interactions. These observations suggest that the acquisition of this Rex-deficient phenotype by in vivo-infected HTLV-1 T cells may represent a critical event in the lymphoproliferation induced by this human retrovirus, leading to leukemia.

Gene Expression Regulation, Viral↗

PubMed1985

Frequent transmission of HTLV-III among spouses of patients with AIDS-related complex and AIDS.

Seven cases of acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC) associated with human T-cell leukemia (lymphotropic) virus (HTLV)-III infection were documented in married males whose family members consented to medical evaluation. Five spouses also had evidence of HTLV-III infection documented by isolation of virus and by detection of serum antibody directed against viral structural proteins. Three of the five HTLV-positive spouses also had clinical evidence of ARC. The remaining four spouses were clinically healthy. Eleven children (between 14 months and 13 years of age) were also evaluated for evidence of disease and exposure to HTLV-III. Only one 14-month-old child was seropositive for antibody to HTLV-III. These data support the opinion that close household contact to patients with ARC or AIDS is not an efficient mechanism for virus transmission, while demonstrating that HTLV-III can be transmitted by repeated heterosexual contact.

Acquired Immunodeficiency Syndrome↗

PubMed2000

Development of an enzyme-linked immunosorbent assay for the detection of antibody to epizootic hemorrhagic disease of deer virus.

An enzyme-linked immunosorbent assay has been developed to detect antibodies to epizootic hemorrhagic disease of deer virus (EHDV). The assay incorporates a monoclonal antibody to EHDV serotype 2 (EHDV-2) that demonstrates specificity for the viral structural protein, VP7. The assay was evaluated with sequential sera collected from cattle experimentally infected with EHDV serotype 1 (EHDV-1) and EHDV-2, as well as the four serotypes of bluetongue virus (BTV), BTV-10, BTV-11, BTV-13, and BTV-17, that currently circulate in the US. A competitive and a blocking format as well as the use of antigen produced from both EHDV-1- and EHDV-2-infected cells were evaluated. The assay was able to detect specific antibody as early as 7 days after infection and could differentiate animals experimentally infected with EHDV from those experimentally infected with BTV. The diagnostic potential of this assay was demonstrated with field-collected serum samples from cattle, deer, and buffalo.

Animals↗

PubMed1991

HIV-specific humoral and cellular immunity in rabbits vaccinated with recombinant human immunodeficiency virus-like gag-env particles.

Recombinant human immunodeficiency virus type-1 (HIV-1)-like gag-env particles produced in mammalian cells were inoculated into two New Zealand white rabbits. In parallel, two control rabbits were inoculated with the homologous HIV-1 virions inactivated by ultra violet light (uv) and psoralen treatments. The humoral and cellular immune responses to HIV-1 were evaluated for both groups of animals. Recombinant particles elicited humoral immunity that was specific for all the viral structural proteins. The antibodies recognized both denatured and nondenatured proteins. Moreover, the sera neutralized the in vitro infectivity of the homologous virus in CEM cells. Importantly, the recombinant particles also generated a T helper response by priming with the HIV proteins. Similar results were observed with inactivated virus immunization. Therefore, our results suggest that the recombinant HIV-like particles elicit functional humoral immunity as well as cellular immunity and represent a novel vaccine candidate for AIDS.

Animals↗

PubMed1986

Transcriptional map of the measles virus genome.

We have constructed a recombinant DNA library of the measles virus genome and identified gene-specific clones containing sequences coding for portions of each of the six viral structural proteins, as well as clones coding for intercistronic sequences. By Northern blotting, we could order the clones according to the pattern of individual gene-specific and readthrough mRNAs. Clones corresponding to the N, P/C and M genes were identified by correlation of the mRNAs with their in vitro translation products; clones corresponding to the H, F and L genes were identified by indirect evidence. The results indicated that the gene order in measles virus is that of a typical paramyxovirus (3'-N,P/C,M,F,H,L-5'), but that the M and F transcripts each contain 1.5 times the coding capacity needed for synthesis of these proteins in vivo.

Cloning, Molecular↗