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Results for “Viral Structures”

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PubMed2003

Antibody responses of naive cattle to two inactivated bovine viral diarrhoea virus vaccines, measured by indirect and blocking ELISAS and virus neutralisation.

Two groups of naive heifers were given primary courses of two inactivated bovine viral diarrhoea (BVD) virus vaccines licensed for use in the UK. Their humoral responses in serum and milk were assayed by means of an indirect ELISA detecting antibodies to structural viral glycoproteins, a blocking ELISA specific for antibodies to the non-structural protein NS2-3 and the virus neutralisation test (VNT). For each assay, the numbers of serum or milk samples testing positive at each sample point and the mean values were determined. In both vaccine groups, serum antibody responses were detected by the indirect ELISA and the VNT, with both the numbers of seropositive animals and mean values peaking five weeks after the second vaccination. In the 23 heifers vaccinated with Bovilis BVD, the mean NS2-3-specific ELISA values remained low throughout the trial, with no serum or milk samples testing positive. In the 24 heifers vaccinated with Bovidec, the mean NS2-3 responses peaked below the level of positivity five weeks after the second vaccination, before declining again; NS2-3-specific antibodies were detected in one serum sample and one milk sample from two heifers in this group. A pooled milk sample from each vaccine group tested negative by both ELISAS 12 weeks after the second vaccination.

Animals↗

PubMed2001

Targets of a protease inhibitor, KNI-272, in HIV-1-infected cells.

The targets of a protease inhibitor, KNI-272, in the HIV-1 life cycle were investigated in this study. Neither expression of HIV-1 Gag proteins nor production of virus particles was detected in cells infected acutely with HIV-1 cultured in the presence of KNI-272. Although HIV-1 proviral DNA was detected in the cells by PCR, the inhibitor depressed the amount of the proviral DNA in a concentration dependent manner. These results indicate that one of the targets of KNI-272 occurs in the stage before the expression of viral structural proteins. No direct inhibition of reverse transcription was found with the inhibitor. To confirm the inhibition of viral protease, persistently HIV-1-infected cells were cultured in the presence of the inhibitor and examined by electron microscopy for the morphology of HIV-1 particles. Doughnut-shaped immature particles were observed in the extracellular space of the cells, and disrupted semicircular shaped particles were also seen at the higher concentration of KNI-272. A bioassay for infectivity showed that the virus particles were not infectious, and immunofluorescent assay using anti-p17 antibody, that does not react with the precursor of Gag protein, revealed that Gag precursor p55 protein in the cells was not processed. Thus, KNI-272 blocked the maturation of viral particles. Consequently, KNI-272 has at least two inhibition targets in the stages of the HIV-1 life cycle.

Anti-HIV Agents↗

PubMed2005

Prion protein: a pattern recognition receptor for viral components and uric acid responsible for the induction of innate and adaptive immunity.

Prion protein, known as Prp(c), is a GPI-anchored membrane bound glycoprotein ubiquitously expressed in the body. To date, the precise nature of its physiological role remains a mystery. The prion protein's presence on neurons and immune effector cells suggests a dual neurological and immunological function. Some consensus exists regarding the proposed involvement of Prp(c) in neurodevelopment, where it would serve to mediate interactions between the extra-cellular matrix (ECM) and the neuron. There is also evidence that Prp plays a part in immunity, although the exact nature of the role remains unclear. Interestingly, a role in both immunity and development is a functional division seen in other types of receptors, most notably the Toll Receptor. In mammals, toll-like receptors (TLRs) are partly responsible for both innate and adaptive immune activity. However, recently several TLR independent pathways have been identified that initiate such responses. Unfortunately, receptors for such pathways remain unidentified. But based upon its functional homology to Toll Receptors, its known interactions with several viruses, and its possible downstream effector proteins, it is proposed that Prp(c) represents a new type of pattern recognition receptor responsible for TLR-independent induction of myeloid dendritic cell and macrophage maturation and later T-cell activation. From what is known of the ligands for the prion protein, it is proposed that this response would be initiated via the binding of uric acid, viral RNA, or viral structural proteins to Prp(c). It will further be proposed that Prp(c)'s ability to interact with viral components stems from its evolutionary origin as a horizontally transferred gene from an early RNA virus. Finally, Prp(c)'s functional role in immunity will be related to the pathophysiology of TSEs, with observations made concerning immune response to infection and agent composition.

Animals↗

PubMed1977

Cell-free synthesis of the precursor polypeptide for avian myeloblastosis virus DNA polymerase.

High molecular weight RNA (35S) isolated from avian myeloblastosis virus directs the cell-free synthesis of two prominent polypeptides of 180,000 and 76,000 molecular weight. The latter polypeptide has previously been identified as the precursor to the group-specific antigens of the virus ("gag" proteins) [Vogt, V. M., Eisenman, R. & Diggelmann, H. (1975) J. Mol. Biol. 96, 471-493]. Two-dimensional tryptic peptide analyses of the [35S]methionine-labeled peptides demonstrate that the 180,000-dalton product is a polyprotein that can account for all the peptides of the avian myeloblastosis virus DNA polymerase (DNA nucleotidyltransferase, EC 2.7.7.7) and those of the gag viral proteins. This is direct confirmation of the genomic order of the viral structural genes, placing the polymerase gene adjacent to the 5'-proximal gag gene of the virus. Furthermore, our findings suggest that the primary polymerase gene product is the beta subunit of the enzyme. These results are discussed in relation to the proposed structural gene map for the avian retraviruses and suggest a model for the in vivo processing of the viral polymerase.

Avian Leukosis Virus↗

PubMed1996

Apoptosis mediated by HIV protease is preceded by cleavage of Bcl-2.

Expression of the human immunodeficiency virus type 1 (HIV) protease in cultured cells leads to apoptosis, preceded by cleavage of bcl-2, a key negative regulator of cell death. In contrast, a high level of bcl-2 protects cells in vitro and in vivo from the viral protease and prevents cell death following HIV infection of human lymphocytes, while reducing the yields of viral structural proteins, infectivity, and tumor necrosis factor alpha. We present a model for HIV replication in which the viral protease depletes the infected cells of bcl-2, leading to oxidative stress-dependent activation of NF kappa B, a cellular factor required for HIV transcription, and ultimately to cell death. Purified bcl-2 is cleaved by HIV protease between phenylalanine 112 and alanine 113. The results suggest a new option for HIV gene therapy; bcl-2 muteins that have noncleavable alterations surrounding the HIV protease cleavage site.

Animals↗

PubMed1980

Short-lived minus-strand polymerase for Semliki Forest virus.

Semliki Forest virus (SFV)-infected BHK-21, Vero, and HeLa cells incorporated [3H]uridine into 42S and 26S plus-strand RNA and into viral minus-strand RNA (complementary to the 42S virion RNA) early in the infectious cycle. Between 3 and 4 h postinfection, the synthesis of minus-strand RNA ceased in these cultures, although the synthesis of plus-strand RNA continued at a maximal rate. At the time of cessation of minus-strand RNA synthesis, two changes in the pattern of viral protein synthesis were detected: a decrease in the translation of nonstructural proteins and an increase in the translation of the viral structural proteins. Addition of cycloheximide and puromycin to cultures of SFV-infected BHK cells actively synthesizing both viral plus- and minus-strand RNA resulted within 15 to 30 min in the selective shutoff of minus-strand RNA synthesis. Removal of the cycloheximide-containing medium led to the resumption of minus-strand synthesis and to an increased rate of viral RNA synthesis. We conclude that the minus-strand polymerase regulates the rate of SFV plus-strand RNA synthesis by determining the number of minus-strand templates and that the synthesis of the minus-strand templates is regulated at the level of translation by a mechanism which utilizes one or more short-lived polymerase proteins.

Animals↗

PubMed1987

Anti-influenza virus cytotoxic T lymphocytes recognize the three viral polymerases and a nonstructural protein: responsiveness to individual viral antigens is major histocompatibility complex controlled.

It has recently been shown that antiviral major histocompatibility complex class I-restricted cytotoxic T lymphocytes can recognize proteins that serve as internal viral structural components (influenza A virus nucleoprotein, vesicular stomatitis virus nucleocapsid protein). To further examine the role of internal viral proteins in cytotoxic T-lymphocyte recognition, we constructed recombinant vaccinia viruses containing individual influenza A virus genes encoding three viral polymerases (PB1, PB2, PA) and a protein not incorporated into virions (NS1). We found that cells infected with each of these recombinant vaccinia viruses could be lysed by anti-influenza cytotoxic T lymphocytes. Cytotoxic T-lymphocyte responsiveness to the individual viral antigens varied greatly between mouse strains. By using congenic mouse strains, responsiveness to PB1 and PB2 was found to cosegregate with major histocompatibility complex haplotype. These findings provide further evidence that internal antigens play a critical role in cytotoxic T-lymphocyte recognition of virus-infected cells. Additionally, they suggest that the cytotoxic T-lymphocyte response to viral antigens may often be restricted to only a fraction of the major histocompatibility complex class I repertoire.

Animals↗

PubMed1988

Identification of a cis-regulatory element involved in accumulation of human T-cell leukemia virus type II genomic mRNA.

The X gene products of the human T-cell leukemia viruses type I and II are thought to be involved not only in viral replication but also in mediating the expression of certain cellular genes. These X gene products are known to be translated from doubly spliced viral mRNA, while viral structural proteins, such as the gag, pol, and env gene products, are translated from unspliced or singly spliced viral mRNA. One of the X gene products of human T-cell leukemia virus type II, tax2 protein, has been shown to be responsible for transcriptional stimulation from the viral long terminal repeat. The other X gene product(s) of human T-cell leukemia virus type II, the rex2 protein(s), is located in the nuclear fraction of virus-infected cells, but its function is not known. This article reports evidence that rex2 protein(s) enhances the accumulation of unspliced viral RNA by interacting posttranscriptionally, either directly or indirectly, with a cis-regulatory element downstream from the first splice donor site in the long terminal repeat.

Cell Line↗

PubMed1977

Comparison of the nucleotide sequence of the messenger RNA for the major structural protein of SV40 with the DNA sequence encoding the amino acids of the protein.

The 16S late mRNA from SV40 directs the synthesis of the major viral structural protein, VP1. We have compared the oligonucleotides in the 16S mRNA with those that would be present in a transcript of the portion of SV40 DNA coding for VP1. The results indicate that a segment of about 200 nucleotides of RNA transcribed from a distant part of SV40 DNA have become linked to the transcript of VP1 codons by a bond resistant to phenol extraction and denaturation in formamide.

Base Sequence↗

PubMedDate not supplied

[Effect of the inter- and intramolecular disulfide bonds on the electrophoretic properties of influenza virus proteins].

The influence of disulphide bonds on the electrophoretic patterns of proteins of various influenza virus strains was studied by one-dimensional and two-dimensional electrophoresis in polyacrylamide gel. A significant effect of inter- and intramolecular disulphide bonds in proteins on their electrophoretic mobility was revealed for some structural viral proteins. In particular, polypeptides of WSN virus neuraminidase after routine treatment of the preparations with sodium dodecylsulphate and heating at a high temperature are detected as homodimers. A small portion of hemagglutinin polypeptides of 5 influenza strains under study are found as trimers under nonreducing conditions. Some subunits of the cleaved hemagglutinin (HA1 and HA2 proteins) of the virus preparations tested are not bound to each other by disulphide bonds. The electrophoretic mobility of intact hemagglutinin under nonreducing conditions is significantly higher than after the destruction of disulphide bonds. This phenomenon appears to be associated with increased compactness of molecules in electrophoresis under nonreducing conditions. Some data indicate a possibility of spontaneous closing up and unlocking of intramolecular disulphide bonds in hemagglutinin. In electrophoresis under nonreducing conditions, nucleoprotein of various influenza viruses is detected as multiple electrophoretic forms of approximately similar mobilities. The possibility of the existence of chemically similar but structurally different forms of nucleoprotein in vivo is discussed. In all purified influenza virus preparations tested a low molecular protein, P12, was found.

Disulfides↗

PubMed1995

Incorporation of Vpr into human immunodeficiency virus type 1: role of conserved regions within the P6 domain of Pr55gag.

The 96-amino acid Vpr protein is the only virion-associated regulatory protein encoded by the human immunodeficiency virus type 1 (HIV-1). Vpr incorporation into the viral particle is most likely due to an interaction with a viral structural protein. Recent data have shown that DNA encoding for the p55 Gag precursor protein (Pr55gag) is the minimal viral genetic information necessary for Vpr incorporation. Other studies have suggested that the p6 portion of Pr55gag, which is unique to lentiviruses, is involved in Vpr incorporation. To investigate the mechanism of incorporation of Vpr into HIV-1 virions, COS-7 cells were cotransfected with ptrENV, an expression vector that encodes all of the HIV-1 regulatory proteins including Rev and Vpr, and different constructs of pIIIgagCAR, a rev-dependent Gag expression plasmid that encodes Pr55gag and the viral protease. Virions produced from gag constructs containing a premature p6 termination codon at positions Leu-1, Ser-17, Tyr-36, or Leu-44 lacked detectable Vpr. In contrast, gag constructs with double Pro-10-Pro-11 substitutions for Leu-10-Leu-11 or a premature termination codon at position Pro-49 of p6 were still able to incorporate Vpr, however, with lower efficiency than wild type. The mutations described in this study affected directly two short regions within the p6 domain, which are highly conserved among primate immunodeficiency viruses. Our results suggest that the conserved (P-T/S-A-P-P) and (L-X-S-L-F-G) motifs located near the N-terminus and C-terminus, respectively, of the p6 domain of Gag are critical for Vpr incorporation into HIV-1 virions.

Amino Acid Sequence↗

PubMed1991

Structural and functional analysis of the human immunodeficiency virus type 2 Rev protein.

The Rev proteins of the human immunodeficiency virus (HIV) are necessary for expression of viral structural gene products. Site-directed mutations were made within the HIV-2 rev gene to identify functional domains. We observed that similar to HIV-1 Rev, the HIV-2 Rev protein was phosphorylated, albeit to a much lesser extent than was HIV-1 Rev. We also found that like HIV-1 Rev, HIV-2 Rev localized to the nucleus, with a marked accumulation in the nucleolus. Mutations within a stretch of basic residues prevented both nuclear and nucleolar localization. Furthermore, mutant Rev proteins able to localize in the nucleus but unable to localize in the nucleolus were nonfunctional.

Amino Acid Sequence↗

PubMed1970

Phospholipid synthesis in Sindbis virus-infected cells.

We investigated the metabolic requirements for the decrease in phospholipid synthesis previously observed by Pfefferkorn and Hunter in primary cultures of chick embryo fibroblasts infected with Sindbis virus. The incorporation of (32)PO(4) into all classes of phospholipids was found to decline at the same rate and to the same extent; thus, incorporation of (14)C-choline into acid-precipitable form provided a convenient measure of phospholipid synthesis that was used in subsequent experiments. Experiments with temperature-sensitive mutants suggested that some viral ribonucleic acid (RNA) synthesis was essential for the inhibition of choline incorporation, but that functional viral structural proteins were not required. The reduction in phospholipid synthesis was probably a secondary effect of infection resulting from viral inhibition of the cellular RNA and protein synthesis. All three inhibitory effects required about the same amount of viral RNA synthesis; the inhibition of host RNA and protein synthesis began sooner than the decline in phospholipid synthesis; and both actinomycin D and cycloheximide inhibited (14)C-choline incorporation in uninfected cells. In contrast, incorporation of (14)C-choline into BHK-21 cells was not decreased by 10 hr of exposure to actinomycin D and declined only slowly after cycloheximide treatment. Growth of Sindbis virus in BHK cells did not cause the marked stimulation of phospholipid synthesis seen in picornavirus infections of other mammalian cells; however, inhibition was seen only late in infection.

Animals↗

PubMed1985

Cloning and sequence of DNA encoding structural proteins of the autonomous parvovirus feline panleukopenia virus.

Approximately 80% of the genome of feline panleukopenia virus was cloned into pBR322. This DNA included the transcription unit for the major viral mRNA species. The nucleotide sequence of the cloned portion of the genome was determined. Comparison of the feline panleukopenia virus sequence with the sequences of the parvoviruses minute virus of mice and H-1 revealed considerable homology between the three viruses on both the nucleic acid and protein levels. Based on this homology, a model for the generation of the two size classes of viral structural proteins (VP1 and VP2') is proposed.

Amino Acid Sequence↗

PubMed1974

Type C viral expression in primate tissues.

Nucleic acid sequences homologous to a [(3)H]DNA transcript prepared from an endogenous baboon type C virus are readily detected in both the cellular DNA and RNA of several different Old World monkeys. Competitive radioimmunoassays for the major viral protein (p30) of baboon type C viruses detect viral antigen in a normal stumptail spleen and a rhesus ovarian carcinoma. The p30 antigen from these tissues is closely related by several immunologic criteria to the p30 protein of baboon type C viruses. The results indicate that normal primate tissues transcribe endogenous viral-specific RNA and translate at least one viral structural protein.

Animals↗

PubMed1985

Intracellular transport of herpes simplex virus gD occurs more rapidly in uninfected cells than in infected cells.

A mouse L cell line which expresses the herpex simplex virus type 1 immediate-early polypeptides ICP4 and ICP47 was cotransfected with a cloned copy of the BglII L fragment of herpes simplex virus type 2, which includes the gene for gD, and the plasmid pSV2neo, which contains the aminoglycosyl 3'-phosphotransferase (agpt) gene conferring resistance to the antibiotic G418. A G418-resistant transformed cell line was isolated which expressed herpes simplex virus type 2 gD at higher levels than were found in infected cells. The intracellular transport and processing of gD was compared in transformed and infected cells. In the transformed Z4/6 cells gD was rapidly processed and transported to the cell surface; in contrast, the processing and cell surface appearance of gD in infected parental Z4 cells occurred at a much slower rate, and gD accumulated in nuclear membrane to a greater extent. Thus, the movement of HSV-2 gD to the cell surface in infected cells is retarded as viral glycoproteins accumulate in the nuclear envelope, probably because they interact with other viral structural components.

Animals↗

PubMed2005

Human cytomegalovirus tegument protein pp71 directs long-term gene expression from quiescent herpes simplex virus genomes.

The human cytomegalovirus tegument protein pp71 is important for transactivation of immediate-early (IE) gene expression and for the efficient initiation of virus replication. We have analyzed the properties of pp71 by assaying its effects on gene expression from the genome of in1312, a herpes simplex virus type 1 (HSV-1) mutant devoid of functional VP16, ICP0, and ICP4. Upon infection of human fibroblasts, in1312-derived viruses are repressed and retained in a quiescent state, but the presence of pp71 prevented the quiescent state from being attained. Reporter gene cassettes cloned into the in1312 genome, in addition to the endogenous IE promoters, remained active for at least 12 days postinfection, and infected cells were viable and morphologically normal. Cells expressing pp71 remained responsive to the HSV-1 transactivating factors VP16 and ICP4 and to trichostatin A. The C-terminal 61 amino acids, but not the LACSD motif, were required for pp71 activity. In addition to preventing attainment of quiescence, pp71 was able to disrupt the quiescent state of in1312 derivatives and promote the resumption of viral gene expression after a lag of approximately 3 days. The results extend the functional analysis of pp71 and suggest a degree of similarity with the HSV-1 IE protein ICP0. The ability to provoke slow reactivation of quiescent genomes, in conjunction with cell survival, represents a novel property for a viral structural protein.

Cytomegalovirus↗

PubMed1986

Immunoenzymatic labelling of JC papovavirus T antigen in brains of patients with progressive multifocal leukoencephalopathy.

Formalin-fixed, paraffin-embedded autopsy sections of brains from two patients with progressive multifocal leukoencephalopathy (PML) were stained by peroxidase-antiperoxidase methods for human papovavirus T antigen, a nonstructural protein expressed in cells lytically infected or transformed by JC, BK, and SV40 viruses. Adjacent sections were stained for papovavirus common structural antigen, a component of JC, BK, and SV40 virions which is synthesized in productively infected but not transformed cells. Intense immunoperoxidase labelling specific for T antigen was detected in large numbers of oligodendrocytes at the edges of demyelinated areas and in occasional oligodendrocytes within otherwise normal brain. Occasional morphologically normal astrocytic cells exhibited similar specific staining, but only rate atypical astrocytic cells contained detectable amounts of T antigen. Examination of adjacent sections stained with antisera to common structural antigen revealed an identical pattern of immunoenzymatic labelling, indicating that most of the cells expressing T antigen were also expressing viral structural proteins. The present study demonstrates that T antigen can be identified by immunoperoxidase methods in routinely processed autopsy material from cases of PML, but that detectable amounts of antigen are found almost exclusively in cells undergoing lytic infection.

Adult↗