pinecone/core-2020-05-10-deduplication huggingface dataset:
The African Swine Fever Virus Proteins p54 and p30 Are Involved in Two Distinct Steps of Virus Attachment and Both Contribute to the Antibody-Mediated Protective Immune Response

AbstractThe nature of the initial interactions of African swine fever (ASF) virus with target cells is only partially known, and to date only the ASF virus protein p12 has been identified as a viral attachment protein. More recently, antibodies to viral proteins p54 and p30 have been shown to neutralize the virus, inhibiting virus binding and internalization, respectively. Therefore, we investigated the role of these proteins in the receptor-mediated ASF virus endocytosis in swine macrophages, the natural host cells. Proteins p54 and p30, released from ASF virus particles after treatment of virions with a nonionic detergent, bound to virus-sensitive alveolar pig macrophages. Binding of these proteins was found to be specifically inhibited by neutralizing antibodies obtained from a convalescent pig or from pigs immunized with recombinant p54 or p30 proteins. The baculovirus-expressed proteins p54 and p30 retained the same biological properties as the viral proteins, since they also bound specifically to these cells, and their binding was equally inhibited by neutralizing antibodies. Binding of35S-labeled recombinant p54 and p30 proteins to macrophages was specifically competed by an excess of unlabeled p54 and p30, respectively. However, cross-binding inhibition was not observed, suggesting the existence of two different saturable binding sites for these proteins in the susceptible cells. In addition, protein p54 blocked the specific binding of virus particles to the macrophage, while protein p30 blocked virus internalization. Both proteins independently prevented virus infection and in a dose-dependent manner, suggesting that binding interactions mediated by both proteins are necessary to give rise to a productive infection. The relevance of blockade of virus–cell interactions mediated by p54 and p30 in the protective immune response against ASF virus was then investigated. Immunization of pigs with either recombinant p54 or p30 proteins induced neutralizing antibodies which, as expected, inhibited virus attachment or internalization, respectively. However, immunized pigs were not protected against lethal infection and the disease course was not modified in these animals. In contrast, immunization with a combination of p54 and p30 proteins simultaneously stimulated both virus neutralizing mechanisms and modified drastically the disease course, rendering a variable degree of protection ranging from a delay in the onset of the disease to complete protection against virus infection. In conclusion, the above results strongly suggest that proteins p54 and p30 mediate specific interactions between ASF virus and cellular receptors and that simultaneous interference with these two interactions has a complementary effect in antibody-mediated protection
Antibodies Directed to Envelope Proteins of Hepatitis C Virus Outside of Hypervariable Region 1

AbstractThe relatively high variability of the hepatitis C virus (HCV) envelope proteins E1 and E2 suggests that parts of these proteins other than the hypervariable region 1 (HVR1) might be involved in the induction of virus neutralizing antibodies. To test this hypothesis, two HCV proteins, pE1 and pE2Δ, were generated byin vitrotranslation. They represent amino acids 174–337 of E1 and 411–688 of E2, respectively, of isolate HCV-AD78; the protein pE2Δ contained no HVR1. As a control, protein pG.HVR1, which represents amino acids 384–410 of HVR1 of isolate HCV-AD78, was expressed separately. These three proteins were used in an immunoprecipitation assay to detect the presence of antiviral antibodies in sera of patients infected with the same isolate of HCV (HCV-AD78). Sera were obtained 4–8 months postinfection from patients who later resolved an acute infection or developed chronic liver disease. A high prevalence of antibodies (up to 85.7%) against pE1 and pE2Δ could be detected in both groups of patients, suggesting that these forms of the HCV envelope proteins contain B-cell epitopes. The antibody responses against proteins pE1 and pE2Δ did not differ significantly between patients with resolving or chronic infection, whereas antibodies against protein pG.HVR1 were associated with resolution of infection. Rabbit antisera raised against pE1 and pE2Δ were tested for their ability to neutralize the binding of HCV to susceptible cells in tissue cultures. The results suggested that although a few B-cell epitopes outside of HVR1 can induce virus neutralizing antibodies, these antibodies are probably not associated with the resolution of infection
Mechanisms of Replication-Deficient Vaccinia Virus/T7 RNA Polymerase Hybrid Expression: Effect of T7 RNA Polymerase Levels and α-Amanitin

AbstractComponents of the eukaryotic vaccinia virus/T7 RNA polymerase hybrid expression system were assessed using recombinant and nonrecombinant forms of modified vaccinia Ankara (MVA), a replication-deficient vaccinia virus strain. Recombinant MVA virus expressing T7 RNA polymerase (Wyatt, L. S., Moss, B., and Rozenblatt, S. (1995).Virology210, 202–205) stimulated high levels of expression from a T7 promoter–chloramphenicol acetyltransferase (CAT) reporter. Most, but not all, of the virally induced expression was T7 RNA polymerase and T7 promoter dependent, with no viral enhancement of translation of T7 transcripts. The efficacy of supplying T7 RNA polymerase expression from nonviral sources was evaluated using a self-amplifying T7 RNA polymerase autogene or an inducible T7 RNA polymerase expression vector. The latter modes yielded CAT activity dependent on T7 RNA polymerase expression; however, expression required viral factors independent of T7 RNA polymerase and did not reach that attained using the recombinant virus. In further experiments, MVA-induced T7 RNA polymerase expression was upregulated by α-amanitin, an inhibitor of eukaryotic polymerases. This indicates that MVA/T7 RNA polymerase hybrid expression may be rendered still more efficient by ameliorating transcriptional interference due to an α-amanitin-sensitive eukaryotic factor(s)
Vaccinia Virus E3L Protein Is an Inhibitor of the Interferon (IFN)-Induced 2-5A Synthetase Enzyme

AbstractInduction of apoptosis in mammalian cells by double-stranded (ds) RNA-dependent enzymes, protein kinase (PKR), and 2-5A-synthetase/RNase L (referred to as the 2-5A system) might be a mechanism mediating anticellular and antiviral actions of interferon (IFN). To counteract the effect of IFN, animal viruses have acquired genes that block specific IFN pathways. Among poxviruses, vaccinia virus (VV) encodes E3L, a dsRNA-binding protein, which inhibits activation of IFN-induced PKR. It has been proposed that E3L might also block activation of the 2-5A system, but direct proof is lacking. To establish if E3L inhibits the 2-5A system, we have developed a method to assay apoptosis induced by increased production of enzymes in the 2-5A pathway, as well as of their putative modulators. This assay is based on the use of cells derived from homozygous PKR knockout mice (Pkr−/−) infected with a VV mutant lacking E3L (ΔE3L) and transiently transfected with a luciferase reporter gene together with plasmid vectors expressing 2-5A-synthetase, RNase L, or E3L, all controlled by the same inducible promoter. We found that expression of 2-5A-synthetase inhibited luciferase activity in a dose–response manner, reaching inhibition values of 80% relative to transfections with control plasmids. Similar results were obtained by transfection with an RNase L vector, although in this case the extent of inhibition was further enhanced upon coexpression of 2-5A-synthetase and RNase L. Inhibition of protein synthesis mediated by the 2-5A system correlated well with induction of apoptosis. Transfection of cells with a plasmid vector expressing E3L together with 2-5A-synthetase completely prevented apoptosis induced by this enzyme. We conclude that VV E3L acts as an inhibitor of the IFN-induced 2-5A-synthetase enzyme
Quantitation of MoMuLV Envelope Protein on the Cell Surface

AbstractThe envelope glycoprotein (Env) of Moloney murine leukemia virus (MoMuLV) is proteolytically processed and transported to the cell surface where it can be incorporated into budding virions. Cell surface Env is frequently detected using an indirect immunofluorescence assay and fluorescence-activated cell sorting (FACS). We found that the detection of Env in this manner requires the expression of the MoMuLV receptor (ATRC-1) on the cell surface, and the level of envelope protein detected correlates with the level of receptors expressed on the cell. In addition, Env detection corresponds to the Env protein's ability to bind to its receptor and can be competed out by the addition of a truncated form of the Env protein. These data suggest that Env detected on the cell surface by the FACS assay is protein that has rebound to its receptor after being secreted or shed, rather than actual surface-expressed protein. In contrast, a combined immunoprecipitation and biotinylation assay detected equal amounts of Env on the surface of both receptor-lacking and receptor-expressing cell lines. The immunoprecipitation–biotinylation assay is therefore a more appropriate method for detecting surface expression of the MoMuLV envelope protein
Mutations in the Sindbis Virus Capsid Gene Can Partially Suppress Mutations in the Cytoplasmic Domain of the Virus E2 Glycoprotein Spike

AbstractAssembly and budding of alphaviruses are postulated to occur by protein–protein interactions between sites on the cytoplasmic domain of the transmembranal envelope E2 glycoprotein and on the surface of the nucleocapsid protein subunits. Genetic data to support this model have been obtained by isolating revertants of two slow-growth mutants of Sindbis virus and analyzing the sequences of the genes encoding their structural proteins. The slow-growth phenotypes of the mutants were previously shown to result from site-directed mutations of 2 amino acids in the sequence corresponding to the 33 amino acids at the carboxyl terminus of E2, which are localized to the cytoplasmic face of the plasma membrane. Putative revertants of these two mutants with faster growth rates were isolated by sequential passaging of virus grown on insect cells or chicken embryo fibroblasts. Sequence analysis of plaque-purified viruses that grew significantly better than the original mutant revealed that the original E2 mutation was present and that there were additional amino acid changes in the virus capsid. Two of the latter were introduced separately into the wild-type virus cDNA and into the genomes of the original mutants. The new strains of virus that contained both capsid and E2 mutations produced many more extracellular particles than those with the E2 mutations alone, indicating substantial suppression of the original E2 mutation. Both capsid mutations appear to be localized near a hydrophobic pocket of the capsid, which is postulated to be the site for docking of hydrophobic amino acids of the E2 cytoplasmic domain. This genetic study provides strong support for the current models of alphavirus assembly
The Simian T-Lymphotropic Virus STLV-PP1664 fromPan paniscusIs Distinctly Related to HTLV-2 but Differs in Genomic Organization

AbstractWe have isolated a highy divergent simian T-lymphotropic virus, STLV-PP1664, from a wild-caught bonobo (Pan paniscus). Previous phylogenetic analysis suggested that this virus represents an additional type of STLV but this has now become a matter of discussion. We have now obtained and analyzed the entire genome of STLV-PP1664. All major genes and their corresponding viral messengers were identified. Sequence comparison and phylogenetic analysis indicated that this virus, together with the closely related panp isolate, belongs to an early lineage within the PTLV-2 clade, differing from HTLV-2 by about 25%. In contrast to the HTLV-1 and HTLV-2 LTR, only two 21-bp repeats instead of three were found in the STLV-PP1664 LTR. Additional messengers, resulting from alternative splicing, potentially encode five different accessory proteins from open reading frames in the pX region: prorfI, porfII, ptorfV′, and two isoforms of Rex. The amino acid sequences of these proteins are only distinctly related to the accessory proteins from HTLV-2. These data suggest a different genomic organization of the STLV-PP1664 pX region than that of HTLV-2. We conclude that STLV-PP1664, although related to HTLV-2, has some distinct features in the LTR and the pX regions, the impact of which needs further investigation. Although arguments pro and contra a distinct classification are nearly equally balanced, we propose to classify this virus as an STLV-2, designated STLV-2PP1664
Phospholipid Interactions of a Peptide from the Fusion-Related Domain of the Glycoprotein of VHSV, a Fish Rhabdovirus

AbstractPrevious studies mapped a p2 domain (aa 82–109) which binds phosphatidylserine (PS) (Estepa and Coll, 1996a) and contains three contiguous hydrophobic amino acid heptad repeats followed by a positively charged stretch (Coll, 1995b) in the glycoprotein G of the viral hemorrhagic septicemia virus (VHSV), a fish rhabdovirus. Anti-p2 antibodies inhibited low-pH VHSV-induced fusion (Estepa and Coll, 1997) and low-pH PS binding to VHSV (Estepa and Coll, 1996a). We report here further studies on the interaction of the synthetic peptide p2 with phospholipid vesicles. The synthetic p2 peptide was able to mediate aggregation, lipid mixing, and leakage of contents only with negatively charged phospholipid vesicles and in a concentration-dependent manner. As shown by its effect on lipid phase transitions deduced from data with fluorescence polarization and differential scanning calorimetry, the p2 peptide becomes inserted into the hydrophobic negatively charged phospholipid vesicle bilayers. In addition, data based on circular dichroism showed that the p2 peptide folds as a structure with a high content of β-sheets stabilized by interaction with anionic phospholipids. These studies are potentially relevant to viral fusion in VHSV
Inhibition of ICE-like Proteases Inhibits Apoptosis and Increases Virus Production during Adenovirus Infection

AbstractInterleukin-1b converting enzyme (ICE)-related cysteine proteases are required for E1A-induced, p53-dependent apoptosis in baby rat kidney (BRK) cells. Adenovirus E1B 19K protein, which is a potent inhibitor of apoptosis, inhibits activation of these proteases in BRK cells. E1A expression induces apoptosis during infection of human cells by mutant adenoviruses which contain nonfunctional E1B 19K. The question arises as to whether ICE-related proteases are involved in E1A-induced apoptosis during mutant adenovirus infection of human cells. To test the involvement of the cysteine proteases in E1A-induced apoptosis during productive adenovirus infection of HeLa cells, we examined whether Z-VAD-FMK, an inhibitor of ICE-related proteases, can inhibit apoptosis induced by mutant adenovirus which lacks functional E1B 19K. Z-VAD-FMK inhibited E1A-induced apoptosis in adenovirus-infected Hela cells, suggesting that the ICE family proteases are involved in this apoptosis pathway. Z-VAD-FMK also inhibited cleavage of substrates such as cysteine protease CPP32 and nuclear lamins, whereas cleavage of poly(ADP-ribose) polymerase was partially inhibited during infection with an E1B 19K mutant. Inhibition of apoptosis by Z-VAD-FMK significantly enhanced production of infectious adenovirus and attenuated virus release. Thus apoptosis may be a method for the host cell to limit virus production and release at the end of the infection cycle
Isolation of a Mutant ofArabidopsis thalianaCarrying Two Simultaneous Mutations Affecting Tobacco Mosaic Virus Multiplication within a Single Cell

AbstractTobacco mosaic virus strain Cg (TMV-Cg) infectsA. thalianasystemically. In order to identify host factors involved in the multiplication of TMV-Cg, we isolated a mutant ofA. thalianafrom an M2 population mutagenized by fast neutron irradiation, in which the accumulation of the coat protein in upper systemic leaves was reduced to low levels. The phenotype of the mutant, YS241, was controlled primarily by a single nuclear recessive mutation namedtom2-1,which was distinct fromtom1, a separate mutation which also affects TMV-Cg multiplication. Thetom2-1mutation affected the accumulation of TMV-related RNAs in protoplasts in a tobamovirus-specific manner, suggesting that the wild-typeTOM2gene product is necessary for efficient amplification of TMV-related RNAs within a single cell, through specific interaction with virus-coded factors. Furthermore, we found that YS241 contained a single dominant modifier namedttm1,which increased the efficiency of multiplication of TMV-Cg and a tomato strain of TMV in atom2-1genetic background, both in plants and in protoplasts. We propose that thettm1element might be a translocated form of theTOM2gene
Analysis of Hepatitis B Virus Populations in an Interferon-α-Treated Patient Reveals Predominant Mutations in the C-Gene and Changing e-Antigenicity

AbstractIt is largely unknown whether hepatitis B virus (HBV) sequence variation during chronic infection hampers HBV immune recognition or the antiviral effect of cytokines on HBV production. Here we have analyzed which region of the HBV genome changes most drastically during an interferon-α (IFNα)-stimulated immune response. In addition, we have investigated whether the mutations affect viral replication, gene expression, and immune recognition of the mutant viral proteins. The study was performed with full-length HBV genomes taken longitudinally from a patient who transiently cleared HBV and seroconverted to anti-HBe during a long-term IFNα treatment. We found a replacement of the predominant virus population during IFNα therapy. The virus populations differed mainly by a cluster of nucleotide changes in the C-gene and a pre-S2 deletion. Most of the newly emerging mutations localized within core/HBe B-cell epitopes, changed HBe antigenicity toward mono- and polyclonal antibodies, and also influenced the reactivity of the anti-HBc/e antibodies of the patient. All genomes tested expressed less HBeAg than wild-type HBV, while replication and IFNα susceptibility were similar. These data indicate that IFNα therapy can lead to the emergence of HBV variants with mutations mainly affecting recognition of the core/HBe proteins by antibodies. Taken together, the type of core/HBe-specific B-cell immune response, the sequence of the corresponding epitopes, and the HBe expression level appear to contribute to the decision on viral clearance or persistence
Chromosomal Aberrations Induced by BK Virus T Antigen in Human Fibroblasts

AbstractHuman fibroblasts, transfected with a recombinant DNA containing theneogene and BK Virus (BKV) early region, which expresses BKV large T antigen (TAg), show cytogenetic alterations characterized by dicentric chromosomes and other structural aberrations such as deletions, duplications, translocations, and ring chromosomes. Such alterations were absent or significantly less frequent in human fibroblasts transfected with a plasmid expressing only theneogene. The chromosome damage in BKV-transfected cells was evident before the appearance of the morphologically transformed phenotype and therefore seems to be a primary effect of TAg expression in human cells. The specific pattern of chromosome aberrations suggests the prevalence of an indirect clastogenic effect, determined by the inhibition of p53 regulatory functions on genome stability by BKV TAg. Due to the widespread distribution of BKV in the human population and to the latent state of BKV DNA in many human organs, the clastogenic activity of BKV TAg may potentially participate in an oncogenic process involving BKV latently infected cells
Regeneration of the Binding Properties of Adenovirus 12 Early Region 1A Proteins after Preparation under Denaturing Conditions

AbstractAdenovirus 12 early region 1A (Ad12 E1A) was expressed inEscherichia coli.Protein was purified in good yield in the presence of 8 M urea and then renatured by dialysis against dilute NH4HCO3buffer. The affinity of this protein for pRb, C-terminal binding protein (CtBP), TATA binding protein (TBP), and SUG1 was similar to, or greater than, that of Ad12 E1A prepared by immunoaffinity chromatography under nondenaturing conditions. While the binding of the 266- and 235-amino-acid (aa) E1A components to TBP showed similar characteristics the larger E1A protein had a higher affinity for CtBP, pRb, and SUG1. Using nuclear magnetic resonance (NMR) spectroscopy it was shown that structural perturbations occurred in the 266-aa protein in the presence of Zn2+consistent with binding—no such changes were seen for the 235-aa protein. Limited proteolysis of the 266- and 235-aa E1A proteins gave rise to comparable polypeptide products, suggesting overall similarities in structure. However, the different affinities of the 266- and 235-aa proteins for the partner proteins and the differences seen in the NMR spectra from the two proteins suggested structural differences
Reduced HIV-1 Infectability of CD4+Lymphocytes from Exposed-Uninfected Individuals: Association with Low Expression of CCR5 and High Production of β-Chemokines

AbstractWe examined the human immunodeficiency virus type 1 infectability of CD4+lymphocytes isolated from CCR5 wild-type individuals, individuals heterozygous for the Δ32 allele of CCR5, and HIV-1-exposed but uninfected (EU) individuals who had CD4+lymphocytes refractory to M-tropic viral replication. None of the EU individuals were found to be heterozygous for the Δ32 allele. The CD4+lymphocytes isolated from CCR5/Δ32 and EU individuals were less infectable with an M-tropic viral isolate of HIV-1 than CCR5/CCR5 control individuals but were equally as infectable with a T-tropic viral isolate. The restriction to M-tropic viral isolate replication did not associate with any profound genotypic change in the CCR5 gene. CD4+lymphocytes from CCR5/Δ32 and CCR5/CCR5 EU individuals were more sensitive to the HIV-inhibitory effects of the recombinant β-chemokines RANTES, MIP-1α, and MIP-1β than were CD4+lymphocytes from CCR5/CCR5 control individuals. CD4+lymphocytes from EU individuals also showed increased sensitivity to recombinant β-chemokines and low surface expression of CCR5. A phenotype of low CCR5 expression and high secretion of β-chemokines is associated with reduced infectability of cells by M-tropic HIV-1. This phenotype may also be associated with protection against sexual transmission of HIV-1
Membranes of Herpes Simplex Virus Type-1-Infected Human Corneal Epithelial Cells Are Not Permeabilized to Macromolecules and Therefore Do Not Release IL-1α

AbstractNanogram amounts of the proinflammatory cytokine interleukin-1α (IL-1α) were detected in uninfected cultures of human corneal epithelial cells (HCEC). Although HSV-1 replicated >104-fold in these cells and caused extensive cytopathic effects, virus infection was not accompanied by significant extracellular release of IL-1α. Additional studies showed that release of radiolabeled cytosolic proteins from virus-infected HCEC was no greater than that released by mock-infected cells. These findings indicate that HSV-1 infection of HCEC does not result in IL-1α release because newly formed virus progeny can escape infected cells without disrupting cell membranes