bluuebunny/crossref_metadata_2025_split huggingface dataset:
Herpes Simplex Virus Type 1 ICP0 Protein Does Not Accumulate in the Nucleus of Primary Neurons in Culture
Authors: Chen Xiao-Ping , Li Jia , Mata Marina , Goss James , Wolfe Darren , Glorioso Joseph C. , Fink David J. 
Published: July 2002

ABSTRACT
Infected-cell protein 0 (ICP0), the product of the herpes simplex virus (HSV) immediate-early (IE) α0 gene, is a promiscuous transactivator of viral early (E) and late (L) gene expression. HSV mutants lacking ICP0 function are severely deficient in viral growth and protein synthesis, particularly at low multiplicities of infection. Early in the infectious process in vitro, ICP0 protein accumulates in distinct domains within the nucleus to form characteristic structures active in the transcription of viral genes. However, following infection of primary trigeminal ganglion cells in vitro with a recombinant HSV mutant that expresses only ICP0, we observed that ICP0 protein accumulated in the characteristic intranuclear distribution only in the nuclei of Schwann cells; neurons in the culture did not accumulate ICP0 despite expression of ICP0 RNA in those cells. The same phenomenon was observed in PC12 cells differentiated to assume a neuronal phenotype. In primary neurons in culture, the amount of ICP0 protein could be increased by pharmacologic inhibition of calcium-activated protease (calpain) activity or by inhibition of protein phosphatase 2B (calcineurin). The failure of ICP0 protein to accumulate in the nucleus of neurons suggests that one mechanism which may impair efficient replication of the virus in neurons, and thus favor the establishment of viral latency in those cells, may be found in the cell-specific processing of that IE gene product.
Incorporation of HLA-DR into the Envelope of Human Immunodeficiency Virus Type 1 In Vivo: Correlation with Stage of Disease and Presence of Opportunistic Infection
Authors: Lawn Stephen D. , Butera Salvatore T. 
Published: July 2002

ABSTRACTHuman immunodeficiency virus type 1 (HIV-1) bearing HLA-DR in its envelope was detected in plasma from all patients with chronic HIV-1 infection (n= 16) and was present at higher levels in patients with active tuberculosis coinfection (n= 6). Intriguingly, however, HLA-DR was not detectable in HIV-1 from patients during primary viremia (n= 6), suggesting the possibility of virus replication in less-activated cells.
RNA Binding Properties of Bunyamwera Virus Nucleocapsid Protein and Selective Binding to an Element in the 5′ Terminus of the Negative-Sense S Segment
Authors: Osborne Jane C. , Elliott Richard M. 
Published: July 2002

ABSTRACTThe genome ofBunyamwera virus(BUN) (familyBunyaviridae, genusBunyavirus) comprises three negative-sense RNA segments which act as transcriptional templates for the viral polymerase only when encapsidated by the nucleocapsid protein (N). Previous studies have suggested that the encapsidation signal may reside within the 5′ terminus of each segment. The BUN N protein was expressed as a 6-histidine-tagged fusion protein inEscherichia coliand purified by metal chelate chromatography. An RNA probe containing the 5′-terminal 32 and 3′-terminal 33 bases of the BUN S (small) genome segment was used to investigate binding by the N protein in vitro using gel mobility shift and filter binding assays. On acrylamide gels a number of discrete RNA-N complexes were resolved, and analysis of filter binding data indicated a degree of cooperativity in N protein binding. RNA-N complexes were resistant to digestion with up to 1 μg of RNase A per ml. Competition assays with a variety of viral and nonviral RNAs identified a region within the 5′ terminus of the BUN S segment for which N had a high preference for binding. This site may constitute the signal for initiation of encapsidation by N.
Importance of Membrane Fusion Mediated by Human Immunodeficiency Virus Envelope Glycoproteins for Lysis of Primary CD4-Positive T Cells
Authors: LaBonte Jason A. , Patel Trushar , Hofmann Wolfgang , Sodroski Joseph 
Published: July 2002

ABSTRACTIn established T-cell lines, the membrane-fusing capacity of the human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins mediates cytopathic effects, both syncytium formation and single-cell lysis. Furthermore, changes in the HIV-1 envelope glycoproteins are responsible for the increased CD4+T-cell-depleting ability observed in infected monkeys upon in vivo passage of simian-human immunodeficiency virus (SHIV) chimeras. In this study, a panel of SHIV envelope glycoproteins and their mutant counterparts defective in membrane-fusing capacity were expressed in primary human CD4+T cells. Compared with controls, all of the functional HIV-1 envelope glycoproteins induced cell death in primary CD4+T-cell cultures, whereas the membrane fusion-defective mutants did not. Death occurred almost exclusively in envelope glycoprotein-expressing cells and not in bystander cells. Under standard culture conditions, most dying cells underwent lysis as single cells. When the cells were cultured at high density to promote syncytium formation, the envelope glycoproteins of the passaged, pathogenic SHIVs induced more syncytia than those of the respective parental SHIV. These results demonstrate that the HIV-1 envelope glycoproteins induce the death of primary CD4+T lymphocytes by membrane fusion-dependent processes.
DNA-Dependent Protein Kinase Is Not Required for Efficient Lentivirus Integration
Authors: Baekelandt Veerle , Claeys Anje , Cherepanov Peter , De Clercq Erik , De Strooper Bart , Nuttin Bart , Debyser Zeger 
Published: July 2002

ABSTRACT

How DNA is repaired after retrovirus integration is not well understood. DNA-dependent protein kinase (DNA-PK) is known to play a central role in the repair of double-stranded DNA breaks. Recently, a role for DNA-PK in retroviral DNA integration has been proposed (R. Daniel, R. A. Katz, and A. M. Skalka, Science 284:644–647, 1999). Reduced transduction efficiency and increased cell death by apoptosis were observed upon retrovirus infection of cultured
scid
cells. We have used a human immunodeficiency virus (HIV) type 1 (HIV-1)-derived lentivirus vector system to further investigate the role of DNA-PK during integration. We measured lentivirus transduction of
scid
mouse embryonic fibroblasts (MEF) and xrs-5 or xrs-6 cells. These cells are deficient in the catalytic subunit of DNA-PK and in Ku, the DNA-binding subunit of DNA-PK, respectively. At low vector titers, efficient and stable lentivirus transduction was obtained, excluding an essential role for DNA-PK in lentivirus integration. Likewise, the efficiency of transduction of HIV-derived vectors in
scid
mouse brain was as efficient as that in control mice, without evidence of apoptosis. We observed increased cell death in
scid
MEF and xrs-5 or xrs-6 cells, but only after transduction with high vector titers (multiplicity of infection [MOI], >1 transducing unit [TU]/cell) and subsequent passage of the transduced cells. At an MOI of <1 TU/cell, however, transduction efficiency was even higher in DNA-PK-deficient cells than in control cells. Taken together, the data suggest a protective role of DNA-PK against cellular toxicity induced by high levels of retrovirus integrase or integration. Another candidate cellular enzyme that has been claimed to play an important role during retrovirus integration is poly(ADP-ribose) polymerase (PARP). However, no inhibition of lentivirus vector-mediated transduction or HIV-1 replication by 3-methoxybenzamide, a known PARP inhibitor, was observed. In conclusion, DNA-PK and PARP are not essential for lentivirus integration.
Memory in Viral Quasispecies
Authors: Ruiz-Jarabo Carmen M. , Arias Armando , Baranowski Eric , Escarmís Cristina , Domingo Esteban 
Published: July 2002

ABSTRACT
Biological adaptive systems share some common features: variation among their constituent elements and continuity of core information. Some of them, such as the immune system, are endowed with memory of past events. In this study we provide direct evidence that evolving viral quasispecies possess a molecular memory in the form of minority components that populate their mutant spectra. The experiments have involved foot-and-mouth disease virus populations with known evolutionary histories. The composition and behavior of the viral population in response to a selective constraint were influenced by past evolutionary history in a way that could not be predicted from examination of consensus nucleotide sequences of the viral populations. The molecular memory of the viral quasispecies influenced both the nature and the intensity of the response of the virus to a selective constraint.
Envelope Glycoprotein Determinants of Increased Fusogenicity in a Pathogenic Simian-Human Immunodeficiency Virus (SHIV-KB9) Passaged In Vivo
Authors: Etemad-Moghadam Bijan , Sun Ying , Nicholson Emma K. , Fernandes Mark , Liou Kwa , Gomila Raul , Lee Juliette , Sodroski Joseph 
Published: July 2002

ABSTRACT
Changes in the envelope glycoprotein ectodomains of a nonpathogenic simian-human immunodeficiency virus (SHIV-89.6) that was serially passaged in vivo have been shown to be responsible for the increased pathogenicity of the resulting virus, SHIV-KB9 (G. B. Karlsson, et al., J. Exp. Med. 188:1159–1171, 1998). The 12 amino acid changes in the envelope glycoprotein ectodomains resulted in increased chemokine receptor-binding and syncytium-forming abilities. Here we identify the envelope glycoprotein determinants of these properties. A single amino acid change in the gp120 third variable (V3) loop was both necessary and sufficient for the observed increase in the binding of the SHIV-KB9 gp120 glycoprotein to the CCR5 chemokine receptor. The increased syncytium-forming ability of SHIV-KB9 involved, in addition to the V3 loop change, changes in the second conserved (C2) region of gp120 (residue 225) and in the gp41 ectodomain (residues 564 and 567). The C2 and gp41 ectodomain changes influenced syncytium formation in a cooperative manner. Changes in the V1/V2 gp120 variable loops exerted a negative effect on syncytium formation and chemokine receptor binding, supporting a previously described role of these changes in immune evasion. The definition of the passage-associated changes that determine the efficiency of chemokine receptor binding and membrane fusogenicity will allow evaluation of the contribution of these properties to in vivo CD4-positive lymphocyte depletion.
Envelope Protein-Mediated Down-Regulation of Hepatitis B Virus Receptor in Infected Hepatocytes
Authors: Breiner Klaus M. , Urban Stephan , Glass Bärbel , Schaller Heinz 
Published: July 2002

ABSTRACT
Entry of duck hepatitis B virus (DHBV) is initiated by specific interaction of its large envelope protein (L) with a cellular entry receptor, recently identified as carboxypeptidase D (CPD; historically gp180). In this report, we present evidence demonstrating that this receptor is down-regulated as a result of DHBV infection: (i) receptor levels determined by Western blot were much reduced in DHBV-infected duck livers and undetectable by immunostaining in infected cultured hepatocytes; (ii) results from metabolic labeling experiments indicate enhanced receptor protein turnover; (iii) the kinetics of receptor loss from newly infected cells correlated with the accumulation of newly synthesized viral protein; (iv) expression of DHBV L protein, transduced from a recombinant adenovirus, was sufficient to eliminate gp180/CPD from the Golgi compartment, its normal predominant location; (v) gp180/CPD remained absent from the Golgi compartment in infected hepatocytes, even after overexpression from a recombinant adenovirus, while residual amounts subsequently became detectable in a perinuclear compartment, containing DHBV L protein; (vi) expression of DHBV L protein in a HepG2 cell line, stably expressing gp180/CPD, leads to incomplete receptor maturation and induces its degradation. Taken together, these data are consistent with a model in which the virus receptor interacts early in the biosynthetic pathway with the viral L protein, leading to its retention in a pre-Golgi compartment and to subsequent degradation, thus preventing receptor interference with the export of DHBV via the secretory pathway which it shares with its receptor. Accordingly, and analogously with receptor down-regulation in retroviral systems, DHBV receptor down-modulation may account for the much-reduced efficiency of DHBV superinfection of preinfected hepatocytes.
Integrin αvβ1 Is an Adenovirus Coreceptor
Authors: Li Erguang , Brown Swati L. , Stupack Dwayne G. , Puente Xose S. , Cheresh David A. , Nemerow Glen R. 
Published: July 2002

ABSTRACT
The human embryonic kidney (HEK293) cell line, commonly used for recombinant adenovirus (Ad) propagation, does not express the Ad coreceptor αvβ3 or αvβ5 integrins, yet these cells are efficiently infected by Ad vectors. Here we demonstrate that Ad binds to HEK293 cells via the fiber receptor CAR and is subsequently internalized via interaction with integrin αvβ1. Function-blocking antibodies directed against αv or β1, but not β3, β5, or α5, integrin subunits block Ad infection and viral endocytosis. Therefore, αvβ1 serves as a coreceptor for Ad infection, and the lack of β3 and/or β5 but the relatively high expression of αvβ1 integrins on certain tumor cell types may explain why these cells are readily transduced by Ad vectors.
Axonal Damage Is T Cell Mediated and Occurs Concomitantly with Demyelination in Mice Infected with a Neurotropic Coronavirus
Authors: Dandekar Ajai A. , Wu Gregory F. , Pewe Lecia , Perlman Stanley 
Published: July 2002

ABSTRACT
Mice infected with mouse hepatitis virus (MHV) strain JHM develop primary demyelination. Herein we show that axonal damage occurred in areas of demyelination and also in adjacent areas devoid of myelin damage. Immunodeficient MHV-infected RAG1−/− mice (mice defective in recombinase activating gene 1 expression) do not develop demyelination unless they receive splenocytes from a mouse previously immunized against MHV (G. F. Wu, A. Dandekar, L. Pewe, and S. Perlman, J. Immunol. 165:2278–2286, 2000). In the present study, we show that adoptive transfer of T cells was also required for the majority of the axonal injury observed in these animals. Both demyelination and axonal damage were apparent by 7 days posttransfer. Recent data suggest that axonal injury is a major factor in the long-term disability observed in patients with multiple sclerosis. Our data demonstrate that immune system-mediated damage to axons is also a common feature in mice with MHV-induced demyelination. Remarkably, there appeared to be a minimal, if any, interval of time between the appearance of demyelination and that of axonal injury.
Nef from Human Immunodeficiency Virus Type 1
F12
Inhibits Viral Production and Infectivity
Authors: Fackler Oliver T. , d'Aloja Paola , Baur Andreas S. , Federico Maurizio , Peterlin B. Matija 
Published: July 2002

ABSTRACT

Human immunodeficiency virus type 1
F12
(HIV-1
F12
) interferes with the replication of other strains of HIV. Its accessory protein, Nef, is sufficient for this phenotype, where the production and infectivity of HIV are impaired significantly. The analysis of three rare mutations in this Nef protein revealed that these effects could be separated genetically. Moreover, the defect in virus production correlated with the lack of processing of the p55
Gag
precursor in the presence of Nef from HIV-1
F12
. Importantly, the introduction of one of these mutations (E177G) into Nef from HIV-1
NL4-3
also created a dominant-negative Nef protein. Effects of Nef from HIV-1
F12
on virus production and Gag processing correlated with its altered subcellular distribution. Moreover, the association with two new cellular proteins with molecular masses of 74 and 75 kDa, which do not interact with other Nef proteins, correlated with the decreased virion infectivity. The identification of a dominant-negative protein for the production and infectivity of HIV suggests that Nef plays an active role at this stage of the viral replicative cycle.
OX40 Stimulation by gp34/OX40 Ligand Enhances Productive Human Immunodeficiency Virus Type 1 Infection
Authors: Takahashi Yoshiaki , Tanaka Yuetsu , Yamashita Atsuya , Koyanagi Yoshio , Nakamura Masataka , Yamamoto Naoki 
Published: July 2002

ABSTRACTOX40 is a member of the tumor necrosis factor (TNF) receptor superfamily and known to be an important costimulatory molecule expressed on activated T cells. To investigate the role of costimulation of OX40 in human immunodeficiency virus type 1 (HIV-1) infection by its natural ligand, gp34, the OX40-transfected ACH-2 cell line, ACH-2/OX40, chronically infected with HIV-1, was cocultured with paraformaldehyde (PFA)-fixed gp34-transfected mouse cell line, SV-T2/gp34. The results showed that HIV-1 production was strongly induced. This was followed by apparent apoptosis, and both processes were specifically inhibited by the gp34-specific neutralizing monoclonal antibody 5A8. Endogenous TNF alpha (TNF-α) and TNF-β production were not involved in the enhanced HIV-1 production. Furthermore, enhanced HIV-1 transcription in gp34-stimulated ACH-2/OX40 cells was dependent on the κB site of the HIV-1 long terminal repeat, and the OX40-gp34 interaction activated NF-κB consisting of p50 and p65 subunits. When primary activated CD4+T cells acutely infected with HIV-1NL4-3(CXCR4-using T-cell-line-tropic) were cocultured with PFA-fixed gp34+human T-cell leukemia virus type 1-bearing MT-2 cells or SV-T2/gp34 cells, HIV-1 production was also markedly enhanced. The enhancement was again significantly inhibited by 5A8. The present study first shows that OX40-gp34 interaction stimulates HIV-1 expression and suggests that OX40 triggering by gp34 may play an important role in enhancing HIV-1 production in both acutely and latently infected CD4+T cells in vivo.
The Vaccinia Virus Superoxide Dismutase-Like Protein (A45R) Is a Virion Component That Is Nonessential for Virus Replication
Authors: Almazán Fernando , Tscharke David C. , Smith Geoffrey L. 
Published: July 2002

ABSTRACTA characterization of the A45R gene from vaccinia virus (VV) strain Western Reserve is presented. The open reading frame is predicted to encode a 125-amino-acid protein (Mr, of 13,600) with 39% amino acid identity to copper-zinc superoxide dismutase (Cu-Zn SOD). Sequencing of the A45R gene from other orthopoxviruses, here and by others, showed that the protein is highly conserved in all viruses sequenced, including 16 strains of VV, 2 strains of cowpox virus, camelpox virus, and 4 strains of variola virus. In all cases the protein lacks key residues involved in metal ion binding that are important for the catalytic activity. The A45R protein was expressed inEscherichia coli, purified, and tested for SOD activity, but neither enzymatic nor inhibitory SOD activity was detected. Additionally, no virus-encoded SOD activity was detected in infected cells or purified virions. A monoclonal antibody raised against the A45R protein expressed inE. coliidentified the A45R gene product as a 13.5-kDa protein that is expressed late during VV infection. Confocal microscopy of VV-infected cells indicated that the A45R protein accumulated predominantly in cytoplasmic viral factories. Electron microscopy and biochemical analyses showed that the A45R protein is incorporated into the virion core. A deletion mutant lacking the majority of the A45R gene and a revertant virus in which the deleted gene was restored were constructed and characterized. The growth properties of the deletion mutant virus were indistinguishable from those of wild-type and revertant viruses in all cell lines tested, including macrophages. Additionally, the virulence and pathogenicity of the three viruses were also comparable in murine and rabbit models of infection. A45R is unusual in being the first VV core protein described that affects neither virus replication nor virulence.
Hydrophobic Amino Acids in the Human Immunodeficiency Virus Type 1 p2 and Nucleocapsid Proteins Can Contribute to the Rescue of Deleted Viral RNA Packaging Signals
Authors: Rong Liwei , Russell Rodney S. , Hu Jing , Guan Yongjun , Kleiman Lawrence , Liang Chen , Wainberg Mark A. 
Published: July 2002

ABSTRACT

An RNA fragment of 75 nucleotides, which is located between the primer binding site and the 5′ major splice donor site in human immunodeficiency virus type 1, has been shown to participate in specific encapsidation of viral RNA. Compensation studies have identified two second-site mutations, namely, MP2 (a T12I substitution in p2) and MNC (a T24I substitution in the nucleocapsid [NC] protein) that were involved in the rescue of various deletions in the aforementioned RNA region (i.e., BH-D1, BH-D2, and BH-LD3). To study whether the MP2 and MNC point mutations exert their compensatory effects in a
cis
manner, production of Gag proteins was blocked by insertion of stop codons into LD3, LD3-MP2-MNC, and wild-type BH10 such that the constructs generated, i.e., LD3-DG, LD3-MP2-MNC-DG, and BH-DG, only provided RNA transcripts for packaging. The results of cotransfection experiments showed that the LD3-MP2-MNC-DG viral RNA was packaged as inefficiently as LD3-DG; in contrast, BH-DG was efficiently packaged. Therefore, nucleotide substitutions in MP2 and MNC did not act in a
cis
manner to correct the packaging deficits in LD3. Next, we deliberately changed the T12 in p2 or the T24 in the NC to each of 19 other amino acids. We found that amino acids with long hydrophobic side chains, i.e., V, L, I, and M, were favored at either position 12 in p2 or at position 24 in NC to compensate for the above-mentioned deletions. Further studies showed that only a few amino acids could not be used at these two sites by the wild-type virus due to decreased RNA levels in the virion or abnormal Gag protein processing. In this case, W, D, and E could not substitute for T12 in p2, and S, D, and N could not substitute for T24 in NC, without affecting viral infectivity. Therefore, the long hydrophobic side chains of V, L, I, and M are necessary for these amino acids to rescue the BH-D1, BH-D2, and BH-LD3 mutated viruses.
Feline Leukemia Virus DNA Vaccine Efficacy Is Enhanced by Coadministration with Interleukin-12 (IL-12) and IL-18 Expression Vectors
Authors: Hanlon Linda , Argyle David , Bain Derek , Nicolson Lesley , Dunham Stephen , Golder Matthew C. , McDonald Michael , McGillivray Christine , Jarrett Oswald , Neil James C. , Onions David E. 
Published: July 2002

ABSTRACTThe expectation that cell-mediated immunity is important in the control of feline leukemia virus (FeLV) infection led us to test a DNA vaccine administered alone or with cytokines that favored the development of a Th1 immune response. The vaccine consisted of two plasmids, one expressing thegag/polgenes and the other expressing theenvgene of FeLV-A/Glasgow-1. The genetic adjuvants were plasmids encoding the feline cytokines interleukin-12 (IL-12), IL-18, or gamma interferon (IFN-γ). Kittens were immunized by three intramuscular inoculations of the FeLV DNA vaccine alone or in combination with plasmids expressing IFN-γ, IL-12, or both IL-12 and IL-18. Control kittens were inoculated with empty plasmid. Following immunization, anti-FeLV antibodies were not detected in any kitten. Three weeks after the final immunization, the kittens were challenged by the intraperitoneal inoculation of FeLV-A/Glasgow-1 and were then monitored for a further 15 weeks for the presence of virus in plasma and, at the end of the trial, for latent virus in bone marrow. The vaccine consisting of FeLV DNA with the IL-12 and IL-18 genes conferred significant immunity, protecting completely against transient and persistent viremia, and in five of six kittens protecting against latent infection. None of the other vaccines provided significant protection.