bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a Primary Tamarin Hepatocyte Culture System for GB Virus-B: a Surrogate Model for Hepatitis C Virus
Authors: Beames Burton , Chavez Deborah , Guerra Bernadette , Notvall Lena , Brasky Kathleen M. , Lanford Robert E. 
Published: July 2002

ABSTRACT

GB virus-B (GBV-B) causes an acute hepatitis in tamarins characterized by increased alanine transaminase levels that quickly return to normal as the virus is cleared. Phylogenetically, GBV-B is the closest relative to hepatitis C virus (HCV), and thus GBV-B infection of tamarins represents a powerful surrogate model system for the study of HCV. In this study, the course of infection of GBV-B in tamarins was followed using a real-time 5′ exonuclease (TaqMan) reverse transcription-PCR assay to determine the level of GBV-B in the serum. Peak viremia levels exceeded 10
9
genome equivalents/ml, followed by viral clearance within 14 to 16 weeks. Rechallenge of animals that had cleared infection resulted in viremia that was limited to 1 week, suggestive of a strong protective immune response. A robust tissue culture system for GBV-B was developed using primary cultures of tamarin hepatocytes. Hepatocytes obtained from a GBV-B-infected animal maintained high levels of cell-associated viral RNA and virion secretion for 42 days of culture. In vitro infection of normal hepatocytes resulted in rapid amplification of cell-associated viral RNA and secretion of up to 10
7
genome equivalents/ml of culture supernatant. In addition, infection could be monitored by immunofluorescence staining for GBV-B nonstructural NS3 protein. This model system overcomes many of the current obstacles to HCV research, including low levels of viral replication, lack of a small primate animal model, and lack of a reproducible tissue culture system.
Lytic but Not Latent Replication of Epstein-Barr Virus Is Associated with PML and Induces Sequential Release of Nuclear Domain 10 Proteins
Authors: Bell Peter , Lieberman Paul M. , Maul Gerd G. 
Published: July 2002

ABSTRACTNuclear domains called ND10 (nuclear domain 10) are discrete nuclear protein aggregations characterized by a set of interferon-upregulated proteins including Sp100 and PML, where papova-, adeno-, and herpesviruses begin their transcription and DNA replication. Both the alpha- and betaherpesvirus subfamilies disrupt ND10 upon infection by dispersing and/or destroying ND10-associated proteins. We studied the effect of the gammaherpesvirus Epstein-Barr virus (EBV) on ND10 and its spatial distribution in the nucleus of cells during latency and lytic reactivation. In latently infected Burkitt's lymphoma, lymphoblastoid, and D98/HR1 cells, ND10 were intact, as judged by immunofluorescence localization of PML, Sp100, NDP55, and Daxx. Fluorescent in situ hybridization revealed no association between viral episomes and ND10 during latency, implying that the maintenance replication of EBV, which depends on host cell proliferation, occurs independent of ND10. As in mitosis, the EBV genomes were attached to interphase chromosomes, suggesting that they are unable to move freely within the interchromosomal space and thus unable to associate with the interchromosomally located ND10 or other nuclear domains. Upon lytic activation, ND10 became dispersed in cells expressing lytic proteins. Redistribution of ND10 proteins occurred sequentially at different stages of the lytic cycle, with Sp100, Daxx, and NDP55 dispersed before and PML dispersed after the onset of lytic replication. ND10 remnants were retained until the early stages of lytic replication, and replicating EBV genomes were frequently found beside this nuclear domain; the number of replication domains was usually lower than the average latent virus frequency. Thus, latency does not require or induce interaction of EBV with ND10 for transcription and replication, whereas lytic replication triggers dispersion of ND10 proteins and occurs in close association with PML aggregates. The required movement of chromosome-attached latent EBV episomes to ND10 after reactivation from latency might include physical release of the chromosome-bound episomes. Only episomes contacting ND10 after such a release might be able to begin lytic replication.
Evolution of the Human Immunodeficiency Virus Type 1 Envelope during Infection Reveals Molecular Corollaries of Specificity for Coreceptor Utilization and AIDS Pathogenesis
Authors: Hu Qin-xue , Barry Ashley Perkins , Wang Zi-xuan , Connolly Shanon M. , Peiper Stephen C. , Greenberg Michael L. 
Published: July 2002

ABSTRACT

The evolution of human immunodeficiency virus type 1 infection is associated with a shift in the target cell population, driven by variability in coreceptor utilization resulting from diversity in
env
. To elucidate the potential consequences of these changes for Env-mediated fusion over the course of AIDS, we examined the biological properties of serial viral isolates and determined coreceptor utilization by the products of
env
cloned from two individuals, followed from the detection of seroconversion throughout the course of their infection. One had a typical course, and the other had an accelerated progression. Early isolates were non-syncytium inducing, and the corresponding Env exclusively utilized CCR5, whereas Env from late phases of infection showed restricted utilization of CXCR4 in both patients. Env from subject SC24, who had a standard progression, demonstrated multitropism, manifested by utilization of CCR3, CXCR4, and CCR5 in the intervening period. In contrast, Env from patient SC51, who experienced early conversion to the syncytium-inducing phenotype, developed dualtropic coreceptor utilization of CCR5 and CXCR4. Genetic analysis of
env
from each isolate revealed that those with an X4 phenotype formed a distinct subcluster within each subject. Analysis of chimeras constructed from R5 and multispecific
env
from patient SC24 demonstrated that while the V3 domain played a dominant role in determining coreceptor utilization, sequences in the V4–V5 region also contributed to the latter phenotype. Immunoprecipitation experiments confirmed that the hybrid Env proteins were expressed at similar levels. These experiments demonstrate that progression from the R5 to X4 phenotype may occur through a multi- or dual-tropic intermediate and that multiple domains contribute to this process.
Expanded Host Cell Tropism and Cytopathic Properties of Feline Immunodeficiency Virus Strain PPR Subsequent to Passage through Interleukin-2-Independent T Cells
Authors: Lerner Danica L. , Elder John H. 
Published: July 2002

ABSTRACT
A cytopathic variant of feline immunodeficiency virus (FIV) strain PPR emerged after passage of wild-type virus on an interleukin-2-independent cell line. The virus, termed FIV-PPRglial, displayed a phenotype markedly different from the parental virus, including the ability to productively infect previously refractory cell lines, induction of large syncytia, and accelerated kinetic properties. A chimeric molecular clone, FIV-PPRchim42, containing the FIV-PPRglial envelope within the backbone of FIV-PPR, exhibited all the characteristics of the FIV-PPRglial phenotype, demonstrating that the viral envelope was responsible for the acquired traits. Subsequent molecular characterization revealed that the FIV-PPRglial envelope contained five amino acid substitutions relative to wild-type FIV-PPR. Mutagenic analyses further demonstrated that the acquired phenotype was minimally attributable to a combination of three mutations, specifically, a glutamine-to-proline change within the second constant domain of the surface protein (SU); a threonine-to-proline change within the V4 loop, also in the SU; and a premature stop codon in the cytoplasmic tail of the transmembrane protein. All three changes were required to produce the FIV-PPRglial phenotype. Cotransfection studies with mutant viruses in combination with each other and with FIV-PPR indicated that the truncated cytoplasmic tail was responsible for the induction of syncytium formation. Receptor usage analyses were pursued, and distinctions were observed between FIV-PPR and FIV-PPRglial. In vitro infections with FIV-PPR, FIV-PPRglial, and FIV-34TF10 on two adherent cell lines were ablated in the presence of SDF1α, the natural ligand for CXCR4. In contrast, viral infection of T cells was not limited to CXCR4 usage, and inhibition studies indicate the potential involvement of a CC chemokine receptor.
Mutation of Predicted Virion Pit Residues Alters Binding of Theiler's Murine Encephalomyelitis Virus to BHK-21 Cells
Authors: Hertzler Shannon , Luo Ming , Lipton Howard L. 
Published: July 2002

ABSTRACT

Theiler's murine encephalomyelitis virus
(TMEV), a natural pathogen of mice, is a member of the genus
Cardiovirus
in the family
Picornaviridae
. Structural studies indicate that the cardiovirus pit, a deep depression on the surface of the virion, is involved in receptor attachment; however, this notion has never been systematically tested. Therefore, we used BeAn virus, a less virulent TMEV, to study the effect of site-specific mutation of selected pit amino acids on viral binding as well as other replicative functions of the virus. Four amino acids within the pit, V1091, P1153, A1225 and P3179, were selected for mutagenesis to evaluate their role in receptor attachment. Three amino acid replacements were made at each site, the first a conservative replacement, followed by progressively more radical amino acid changes in order to detect variable effects at each site. A total of seven viable mutant viruses were recovered and characterized for their binding properties to BHK-21 cells, capsid stability at 40°C, viral RNA replication, single- and multistep growth kinetics, and virus translation. Our data implicate three of these residues in TMEV-cell receptor attachment.
Resistance to Replication of Human Immunodeficiency Virus Challenge in SCID-Hu Mice Engrafted with Peripheral Blood Mononuclear Cells of Nonprogressors Is Mediated by CD8+T Cells and Associated with a Proliferative Response to p24 Antigen
Authors: de Quiros Juan Carlos Lopez Bernaldo , Shupert W. Lesley , McNeil Andrew C. , Gea-Banacloche Juan C. , Flanigan Mark , Savage Ann , Martino Lisa , Weiskopf Emma E. , Imamichi Hiromi , Zhang Yi-Ming , Adelsburger Joseph , Stevens Randy , Murphy Philip M. , Zimmerman Peter A. , Hallahan Claire W. , Davey Richard T. , Connors Mark 
Published: July 2002

ABSTRACTHigh levels of resistance to challenge with human immunodeficiency virus type 1 SF162 were observed in animals engrafted with peripheral blood mononuclear cells of four long-term nonprogressors (LTNPs). Resistance was abrogated by depletion of CD8+T cells in vivo and was observed only in LTNPs with proliferative responses to p24. In a subgroup of nonprogressors, CD8+T cells mediated restriction of challenge viruses, and this response was associated with strong proliferative responses to p24 antigen.
Hepatitis C Virus-Encoded Enzymatic Activities and Conserved RNA Elements in the 3′ Nontranslated Region Are Essential for Virus Replication In Vivo
Authors: Kolykhalov Alexander A. , Mihalik Kathy , Feinstone Stephen M. , Rice Charles M. 
Published: July 2002

ABSTRACT
Hepatitis C virus (HCV) infection is a widespread major human health concern. Significant obstacles in the study of this virus include the absence of a reliable tissue culture system and a small-animal model. Recently, we constructed full-length HCV cDNA clones and successfully initiated HCV infection in two chimpanzees by intrahepatic injection of in vitro-transcribed RNA (A. A. Kolykhalov et al., Science 277:570–574, 1997). In order to validate potential targets for development of anti-HCV therapeutics, we constructed six mutant derivatives of this prototype infectious clone. Four clones contained point mutations ablating the activity of the NS2-3 protease, the NS3-4A serine protease, the NS3 NTPase/helicase, and the NS5B polymerase. Two additional clones contained deletions encompassing all or part of the highly conserved 98-base sequence at the 3′ terminus of the HCV genome RNA. The RNA transcript from each of the six clones was injected intrahepatically into a chimpanzee. No signs of HCV infection were detected in the 8 months following the injection. Inoculation of the same animal with nonmutant RNA transcripts resulted in productive HCV infection, as evidenced by viremia, elevated serum alanine aminotransferase, and HCV-specific seroconversion. These data suggest that these four HCV-encoded enzymatic activities and the conserved 3′ terminal RNA element are essential for productive replication in vivo.
Sensitivity to a Nonpeptidic Compound (RPR103611) Blocking Human Immunodeficiency Virus Type 1 Env-Mediated Fusion Depends on Sequence and Accessibility of the gp41 Loop Region
Authors: Labrosse Béatrice , Treboute Carole , Alizon Marc 
Published: July 2002

ABSTRACT

The triterpene RPR103611 is an efficient inhibitor of membrane fusion mediated by the envelope proteins (Env, gp120-gp41) of CXCR4-dependent (X4) human immunodeficiency virus type 1 (HIV-1) strains, such as HIV-1
LAI
(LAI). Other X4 strains, such as HIV-1
NDK
(NDK), and CCR5-dependent (R5) HIV-1 strains, such as HIV-1
ADA
(ADA), were totally resistant to RPR103611. Analysis of chimeric LAI-NDK Env proteins identified a fragment of the NDK gp41 ectodomain determining drug resistance. A single difference at position 91, leucine in LAI and histidine in NDK, apparently accounted for their sensitivity or resistance to RPR103611. We had previously identified a mutation of isoleucine 84 to serine in a drug escape LAI variant. Both I84 and L91 are located in the “loop region” of gp41 separating the proximal and distal helix domains. Nonpolar residues in this region therefore appear to be important for the antiviral activity of RPR103611 and are possibly part of its target. However, another mechanism had to be envisaged to explain the drug resistance of ADA, since its gp41 loop region was almost identical to that of LAI. Fusion mediated by chimeric Env consisting of LAI gp120 and ADA gp41, or the reciprocal construct, was fully blocked by RPR103611. The gp120-gp41 complex of R5 strains is stable, relative to that of X4 strains, and this stability could play a role in their drug resistance. Indeed, when the postbinding steps of ADA infection were performed under mildly acidic conditions (pH 6.5 or 6.0), a treatment expected to favor dissociation of gp120, we achieved almost complete neutralization by RPR103611. The drug resistance of NDK was partially overcome by preincubating virus with soluble CD4, a gp120 ligand inducing conformational changes in the Env complex. The antiviral efficacy of RPR103611 therefore depends on the sequence of the gp41 loop and the stability of the gp120-gp41 complex, which could limit the accessibility of this target.
Erythroid Cells Rendered Erythropoietin Independent by Infection with Friend Spleen Focus-Forming Virus Show Constitutive Activation of Phosphatidylinositol 3-Kinase and Akt Kinase: Involvement of Insulin Receptor Substrate-Related Adapter Proteins
Authors: Nishigaki Kazuo , Hanson Charlotte , Ohashi Takashi , Thompson Delores , Muszynski Karen , Ruscetti Sandra 
Published: July 2002

ABSTRACT
The erythroleukemia-inducing Friend spleen focus-forming virus (SFFV) encodes a unique envelope glycoprotein which allows erythroid cells to proliferate and differentiate in the absence of erythropoietin (Epo). In an effort to understand how SFFV causes Epo independence, we have been examining erythroid cells rendered factor independent by SFFV infection for constitutive activation of signal-transducing molecules. Previous studies from our laboratory showed that various signal-transducing molecules known to be activated by Epo, including Stat proteins and components of the Raf-1/MAP kinase pathway, are constitutively activated in SFFV-infected erythroid cells in the absence of Epo. Since another signal transduction pathway involving activation of phosphatidylinositol 3-kinase (PI 3-kinase) after Epo stimulation plays an important role in erythroid cell proliferation and differentiation, we carried out studies to determine if this pathway was also activated in SFFV-infected cells in the absence of Epo. Our studies show that PI 3-kinase is constitutively activated in erythroid cells rendered factor independent by infection with SFFV and that PI 3-kinase activity, but not Epo receptor tyrosine phosphorylation, is required for the proliferation of these cells in the absence of Epo. We further show that in SFFV-infected erythroid cells grown in the absence of Epo, PI 3-kinase associates with the insulin receptor substrate (IRS)-related adapter molecules IRS-2, Gab1, and Gab2, which are constitutively tyrosine phosphorylated in SFFV-infected cells. Finally, Akt, a protein kinase that is one of the downstream effectors of PI 3-kinase, and SHIP, a lipid phosphatase that is important for Akt activation through PI 3-kinase, are both tyrosine phosphorylated in SFFV-infected cells grown in the absence of Epo. Our results indicate that induction of Epo independence by SFFV requires the activation of PI 3-kinase and suggest that constitutive activation of this kinase in SFFV-infected cells may occur primarily through interaction of PI 3-kinase with constitutively phosphorylated IRS-related adapter molecules.
Structure and Coding Content of CST (BART) Family RNAs of Epstein-Barr Virus
Authors: Smith Paul R. , de Jesus Orlando , Turner David , Hollyoake Martine , Karstegl Claudio Elgueta , Griffin Beverly E. , Karran Lorraine , Wang Yilong , Hayward S. Diane , Farrell Paul J. 
Published: July 2002

ABSTRACT
CST (BART BARF0) family viral RNAs are expressed in several types of Epstein-Barr virus (EBV) infection, including EBV-associated cancers. Many different spliced forms of these RNAs have been described; here we have clarified the structures of some of the more abundant splicing patterns. We report the first cDNAs representing a full-length CST mRNA from a clone library and further characterize the transcription start. The relative abundance of splicing patterns and genomic analysis of the open reading frames (ORFs) suggest that, in addition to the much studied BARF0 ORF, there may be important products made from some of the upstream ORFs in the CST RNAs. Potential biological functions are identified for two of these. The product of the RPMS1 ORF is shown to be a nuclear protein that can bind to the CBF1 component of Notch signal transduction. RPMS1 can inhibit the transcription activation induced through CBF1 by NotchIC or EBNA-2. The protein product of another CST ORF, A73, is shown to be a cytoplasmic protein which can interact with the cell RACK1 protein. Since RACK1 modulates signaling from protein kinase C and Src tyrosine kinases, the results suggest a possible role for CST products in growth control, perhaps consistent with the abundant transcription of CST RNAs in cancers such as nasopharyngeal carcinoma.
Bystander Sensitization to Activation-Induced Cell Death as a Mechanism of Virus-Induced Immune Suppression
Authors: Zarozinski Christopher C. , McNally James M. , Lohman Barbara L. , Daniels Keith A. , Welsh Raymond M. 
Published: July 2002

ABSTRACTViral infections which induce strong T-cell responses are often characterized by a period of transient immunodeficiency associated with the failure of host T cells to proliferate in response to mitogens or to mount memory recall responses to other antigens. During acute infections, most of the activated, proliferating virus-specific T cells are sensitized to undergo apoptosis on strong T-cell receptor (TCR) stimulation, but it has not been known why memory T cells not specific for the virus fail to proliferate on exposure to their cognate antigen. Using a lymphocytic choriomeningitis virus (LCMV) infection model in which LCMV-immune Thy 1.1+splenocytes are adoptively transferred into Thy 1.2+LCMV carrier mice, we demonstrate here that T cells clearly defined as not specific for the virus are sensitized to undergo activation-induced cell death on TCR stimulation in vitro. This bystander sensitization was in part dependent on the expression of Fas ligand (FasL) on the activated virus-specific cells and gamma interferon (IFN-γ) receptor expression on the bystander T cells. We propose that FasL from highly activated antiviral T cells may sensitize IFN-γ-conditioned T cells not specific for the virus to undergo apoptosis rather than to proliferate on encountering antigen. This may in part explain the failure of memory T cells to respond to recall antigens during acute and persistent viral infections.
Anti-Human Immunodeficiency Virus Type 1 (HIV-1) CD8+T-Lymphocyte Reactivity during Combination Antiretroviral Therapy in HIV-1-Infected Patients with Advanced Immunodeficiency
Authors: Rinaldo Charles R. , Huang Xiao-Li , Fan Zheng , Margolick Joseph B. , Borowski Luann , Hoji Aki , Kalinyak Christine , McMahon Deborah K. , Riddler Sharon A. , Hildebrand William H. , Day Richard B. , Mellors John W. 
Published: July 2002

ABSTRACTThe long-term efficacy of combination antiretroviral therapy may relate to augmentation of anti-human immunodeficiency virus type 1 (HIV-1) CD8+T-cell responses. We found that prolonged treatment of late-stage HIV-1-infected patients with a protease inhibitor and two nucleoside reverse transcriptase inhibitors failed to restore sustained, high levels of HIV-1-specific, HLA class I-restricted, cytotoxic-T-lymphocyte precursors and gamma interferon (IFN-γ) production by CD8+T cells. In some patients, particularly those initiating three-drug combination therapy simultaneously rather than sequentially, there were early, transient increases in the frequency of anti-HIV-1 CD8+T cells that correlated with decreases in HIV-1 RNA and increases in T-cell counts. In the other patients, HIV-1-specific T-cell functions either failed to increase or declined from baseline during triple-drug therapy, even though some of these patients showed suppression of plasma HIV-1 RNA. These effects of combination therapy were not unique to HIV-1 specific T-cell responses, since similar effects were noted for CD8+T cells specific for the cytomegalovirus pp65 matrix protein. The level and breadth of CD8+cell reactivity to HLA A*02 HIV-1 epitopes, as determined by IFN-γ production and HLA tetramer staining after combination therapy, were related to the corresponding responses prior to treatment. There was, however, a stable, residual population of potentially immunocompetent HIV-1-specific T cells remaining after therapy, as shown by tetramer staining of CD8+CD45RO+cells. These results indicate that new strategies will be needed to target residual, immunocompetent HIV-1-specific CD8+T cells to enhance the effectiveness of antiretroviral therapy in patients with advanced immunodeficiency.