bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective Loss of Innate CD4+Vα24 Natural Killer T Cells in Human Immunodeficiency Virus Infection
Authors: Sandberg Johan K. , Fast Noam M. , Palacios Emil H. , Fennelly Glenn , Dobroszycki Joanna , Palumbo Paul , Wiznia Andrew , Grant Robert M. , Bhardwaj Nina , Rosenberg Michael G. , Nixon Douglas F. 
Published: July 2002

ABSTRACTVα24 natural killer T (NKT) cells are innate immune cells involved in regulation of immune tolerance, autoimmunity, and tumor immunity. However, the effect of human immunodeficiency virus type 1 (HIV-1) infection on these cells is unknown. Here, we report that the Vα24 NKT cells can be subdivided into CD4+or CD4−subsets that differ in their expression of the homing receptors CD62L and CD11a. Furthermore, both CD4+and CD4−NKT cells frequently express both CXCR4 and CCR5 HIV coreceptors. We find that the numbers of NKT cells are reduced in HIV-infected subjects with uncontrolled viremia and marked CD4+T-cell depletion. The number of CD4+NKT cells is inversely correlated with HIV load, indicating depletion of this subset. In contrast, CD4−NKT-cell numbers are unaffected in subjects with high viral loads. HIV infection experiments in vitro show preferential depletion of CD4+NKT cells relative to regular CD4+T cells, in particular with virus that uses the CCR5 coreceptor. Thus, HIV infection causes a selective loss of CD4+lymph node homing (CD62L+) NKT cells, with consequent skewing of the NKT-cell compartment to a predominantly CD4−CD62L−phenotype. These data indicate that the key immunoregulatory NKT-cell compartment is compromised in HIV-1-infected patients.
Different Effects of Nef-Mediated HLA Class I Down-Regulation on Human Immunodeficiency Virus Type 1-Specific CD8+T-Cell Cytolytic Activity and Cytokine Production
Authors: Tomiyama Hiroko , Akari Hirofumi , Adachi Akio , Takiguchi Masafumi 
Published: July 2002

ABSTRACTA previous study using a Nef-defective human immunodeficiency virus type 1 (HIV-1) mutant suggested that Nef-mediated down-regulation of HLA class I on the infected cell surface affects the cytolytic activity of HIV-1-specific cytotoxic T-lymphocyte (CTL) clones for HIV-1-infected primary CD4+T cells. We confirmed this effect by using anef-mutant HIV-1 strain (NL-M20A) that expresses a Nef protein which does not induce down-regulation of HLA class I molecules but is otherwise functional. HIV-1-specific CTL clones were not able to kill primary CD4+T cells infected with a Nef-positive HIV-1 strain (NL-432) but efficiently lysed CD4+T cells infected with NL-M20A. Interestingly, CTL clones stimulated with NL-432-infected CD4+T cells were able to produce cytokines, albeit at a lower level than when stimulated with NL-M20A-infected CD4+T cells. This indicates that Nef-mediated HLA class I down-regulation affects CTL cytokine production to a lesser extent than cytolytic activity. Replication of NL-432 was partially suppressed in a coculture of HIV-1-infected CD4+T cells and HIV-1-specific CTL clones, while replication of NL-M20A was completely suppressed. These results suggest that HIV-1-specific CD8+T cells are able to partially suppress the replication of HIV-1 through production of soluble HIV-1-suppressive factors such as chemokines and gamma interferon. These findings may account for the mechanism whereby HIV-1-specific CD8+T cells are able to partially but not completely control HIV-1 replication in vivo.
Replication of Avian Sarcoma Virus In Vivo Requires an Interaction between the Viral RNA and the TψC Loop of the tRNA
Trp
Primer
Authors: Morris Shannon , Johnson Michael , Stavnezer Ed , Leis Jonathan 
Published: July 2002

ABSTRACT

Reverse transcription in avian sarcoma virus (ASV) initiates from the 3′ end of a tRNA
Trp
primer, which anneals near the 5′ end of the RNA genome. The region around the primer-binding site (PBS) forms an elaborate stem structure composed of the U5-inverted repeat (U5-IR) stem, the U5-leader stem, and the association of the tRNA primer with the PBS. There is evidence for an additional interaction between the viral U5 RNA and the TψC loop of the tRNA
Trp
(U5-TψC). We now demonstrate that this U5-TψC interaction is necessary for efficient replication of ASV in culture. By randomizing specific biologically relevant regions of the viral RNA, thereby producing a library of mutant viruses, we are able to select, through multiple rounds of infection, those sequences imparting survival fitness to the virus. Randomizing the U5-TψC interaction region of the viral RNA results in selection of largely wild-type sequences after five rounds of infection. Also recovered are mutant viruses that maintain their ability to base pair with the TψC loop of the tRNA
Trp
. To prove this interaction is specific to the tRNA primer, we constructed a second library, in which we altered the PBS to anneal to tRNA
Pro
, while simultaneously randomizing the viral RNA U5-TψC region. After five rounds of infection, the consensus sequence 5′-GPuPuCPy-3′ emerged, which is complementary to the 5′-GGTTC-3′ sequence found in the TψC loop of tRNA
Pro
. These observations confirm the importance of the U5-TψC interaction in vivo.
Shedding and Intracage Transmission of Sin Nombre Hantavirus in the Deer Mouse (
Peromyscus maniculatus
) Model
Authors: Botten Jason , Mirowsky Katy , Ye Chunyan , Gottlieb Keith , Saavedra Melissa , Ponce Liana , Hjelle Brian 
Published: July 2002

ABSTRACT
The mechanism(s) by which Sin Nombre (SN) hantavirus is maintained in deer mouse populations is unclear. Field studies indicate that transmission occurs primarily if not exclusively via a horizontal mechanism. Using an experimental deer mouse infection model in an outdoor laboratory, we tested whether infected rodents shed SN virus in urine, feces, and saliva, whether infected mice transmit infection to naïve cage mates, and whether infected dams are able to vertically transmit virus or antibody to offspring. Using pooled samples of urine, feces, and saliva collected from mice infected 8 to 120 days postinoculation (p.i.), we found that a subset of saliva samples, collected between 15 and 90 days p.i., contained viral RNA. Parallel studies conducted on wild-caught, naturally infected deer mice showed a similar pattern of intermittent positivity, also only in saliva samples. Attempts to isolate virus through inoculation of cells or naïve deer mice with the secreta or excreta of infected mice were uniformly negative. Of 54 attempts to transmit infection by cohousing infected deer mice with seronegative cage mates, we observed only a single case of transmission, which occurred between 29 and 42 days p.i. Dams passively transferred antibodies to neonatal pups via milk, and those antibodies persisted for at least 2 months after weaning, but none transmitted infection to their pups. Compared to other hantavirus models, SN virus is shed less efficiently and transmits inefficiently among cage mates. Transmission of SN virus among reservoir rodents may require factors that are not required for other hantaviruses.
Identification and Characterization of Two Closely Related Unclassifiable Endogenous Retroviruses in Pythons (Python molurusandPython curtus)
Authors: Huder Jon B. , Böni Jürg , Hatt Jean-Michel , Soldati Guido , Lutz Hans , Schüpbach Jörg 
Published: July 2002

ABSTRACTBoid inclusion body disease (BIBD) is a fatal disorder of boid snakes that is suspected to be caused by a retrovirus. In order to identify this agent, leukocyte cultures (established fromPython molurusspecimens with symptoms of BIBD or kept together with such diseased animals) were assessed for reverse transcriptase (RT) activity. Virus from cultures exhibiting high RT activity was banded on sucrose density gradients, and the RT peak fraction was subjected to highly efficient procedures for the identification of unknown particle-associated retroviral RNA. A 7-kb full retroviral sequence was identified, cloned, and sequenced. This virus contained intact open reading frames (ORFs) forgag,pro,pol, andenv, as well as another ORF of unknown function withinpol. Phylogenetic analysis showed that the virus is distantly related to viruses from both the B and D types and the mammalian C type but cannot be classified. It is present as a highly expressed endogenous retrovirus in allP. molurusindividuals; a closely related, but much less expressed virus was found in all testedPython curtusindividuals. All other boid snakes tested, includingPython regius,Python reticulatus,Boa constrictor,Eunectes notaeus, andMorelia spilota, were virus negative, independent of whether they had BIBD or not. Virus isolated fromP. moluruscould not be transmitted to the peripheral blood mononuclear cells ofB. constrictororP. regius. Thus, there is no indication that this novel virus, which we propose to name python endogenous retrovirus (PyERV), is causally linked with BIBD.
Daxx-Mediated Accumulation of Human Cytomegalovirus Tegument Protein pp71 at ND10 Facilitates Initiation of Viral Infection at These Nuclear Domains
Authors: Ishov Alexander M. , Vladimirova Olga V. , Maul Gerd G. 
Published: July 2002

ABSTRACT

Human cytomegalovirus (HCMV) starts immediate-early transcription at nuclear domains 10 (ND10), forming a highly dynamic immediate transcript environment at this nuclear site. The reason for this spatial correlation remains enigmatic, and the mechanism for induction of transcription at ND10 is unknown. We investigated whether tegument-based transactivators are involved in the specific intranuclear location of HCMV. Here, we demonstrate that the HCMV transactivator tegument protein pp71 accumulates at ND10 before the production of immediate-early proteins. Intracellular trafficking of pp71 is facilitated through binding to a coiled-coil region of Daxx. The C-terminal domain of Daxx then interacts with SUMO-modified PML, resulting in the deposition of pp71 at ND10. In Daxx-deficient cells, pp71 does not accumulate at ND10, proving in vivo the necessity of Daxx for pp71 deposition. Also, HCMV forms immediate transcript environments at sites other than ND10 in Daxx-deficient cells, and so does the HCMV pp71 knockout mutant UL82
−/−
in normal cells. This result strongly suggests that pp71 and Daxx are essential for HCMV transcription at ND10. Lack of Daxx had the effect of reducing the infection rate. We conclude that the tegument transactivator pp71 facilitates viral genome deposition and transcription at ND10, possibly priming HCMV for more efficient productive infection.
Immunogenicity and Safety of Defective Vaccinia Virus Lister: Comparison with Modified Vaccinia Virus Ankara
Authors: Ober B. T. , Brühl P. , Schmidt M. , Wieser V. , Gritschenberger W. , Coulibaly S. , Savidis-Dacho H. , Gerencer M. , Falkner F. G. 
Published: July 2002

ABSTRACTPotent and safe vaccinia virus vectors inducing cell-mediated immunity are needed for clinical use. Replicating vaccinia viruses generally induce strong cell-mediated immunity; however, they may have severe adverse effects. As a vector for clinical use, we assessed the defective vaccinia virus system, in which deletion of an essential gene blocks viral replication, resulting in an infectious virus that does not multiply in the host. The vaccinia virus Lister/Elstree strain, used during worldwide smallpox eradication, was chosen as the parental virus. The immunogenicity and safety of the defective vaccinia virus Lister were evaluated without and with the inserted human p53 gene as a model and compared to parallel constructs based on modified vaccinia virus Ankara (MVA), the present “gold standard” of recombinant vaccinia viruses in clinical development. The defective viruses induced an efficient Th1-type immune response. Antibody and cytotoxic-T-cell responses were comparable to those induced by MVA. Safety of the defective Lister constructs could be demonstrated in vitro in cell culture as well as in vivo in immunodeficient SCID mice. Similar to MVA, the defective viruses were tolerated at doses four orders of magnitude higher than those of the wild-type Lister strain. While current nonreplicating vectors are produced mainly in primary chicken cells, defective vaccinia virus is produced in a permanent safety-tested cell line. Vaccines based on this system have the additional advantage of enhanced product safety. Therefore, a vector system was made which promises to be a valuable tool not only for immunotherapy for diseases such as cancer, human immunodeficiency virus infection, or malaria but also as a basis for a safer smallpox vaccine.
Friend Leukemia Virus Infection Enhances DNA Damage-Induced Apoptosis of Hematopoietic Cells, Causing Lethal Anemia in C3H Hosts
Authors: Kitagawa Masanobu , Yamaguchi Shuichi , Hasegawa Maki , Tanaka Kaoru , Sado Toshihiko , Hirokawa Katsuiku , Aizawa Shiro 
Published: July 2002

ABSTRACT

Exposure of hematopoietic progenitors to gamma irradiation induces
p53
-dependent apoptosis. However, host responses to DNA damage are not uniform and can be modified by various factors. Here, we report that a split low-dose total-body irradiation (TBI) (1.5 Gy twice) to the host causes prominent apoptosis in bone marrow cells of Friend leukemia virus (FLV)-infected C3H mice but not in those of FLV-infected DBA mice. In C3H mice, the apoptosis occurs rapidly and progressively in erythroid cells, leading to lethal host anemia, although treatment with FLV alone or TBI alone induced minimal apoptosis in bone marrow cells. A marked accumulation of P53 protein was demonstrated in bone marrow cells from FLV-infected C3H mice 12 h after treatment with TBI. Although a similar accumulation of P53 was also observed in bone marrow cells from FLV-infected DBA mice treated with TBI, the amount appeared to be parallel to that of mice treated with TBI alone and was much lower than that of FLV- plus TBI-treated C3H mice. To determine the association of
p53
with the prominent enhancement of apoptosis in FLV- plus TBI-treated C3H mice,
p53
knockout mice of the C3H background (C3H

p53
−/−

) were infected with FLV and treated with TBI. As expected,
p53
knockout mice exhibited a very low frequency of apoptosis in the bone marrow after treatment with FLV plus TBI. Further, C3H

p53
−/−

→ C3H

p53
+/+

bone marrow chimeric mice treated with FLV plus TBI survived even longer than the chimeras treated with FLV alone. These findings indicate that infection with FLV strongly enhances radiation-induced apoptotic cell death of hematopoietic cells in host animals and that the apoptosis occurs through a
p53
-associated signaling pathway, although the response was not uniform in different host strains.
Avian Reoviruses Cause Apoptosis in Cultured Cells: Viral Uncoating, but Not Viral Gene Expression, Is Required for Apoptosis Induction
Authors: Labrada Lucía , Bodelón Gustavo , Viñuela Juan , Benavente Javier 
Published: July 2002

ABSTRACTThe cytopathic effect evidenced by cells infected with avian reovirus S1133 suggests that this virus may induce apoptosis in primary cultures of chicken embryo fibroblasts. In this report we present evidence that avian reovirus infection of cultured cells causes activation of the intracellular apoptotic program and that this activation takes place during an early stage of the viral life cycle. The ability of avian reoviruses to induce apoptosis is not restricted to a particular virus strain or to a specific cell type, since different avian reovirus isolates were able to induce apoptosis in several avian and mammalian cell lines. Apoptosis was also provoked in ribavirin-treated avian reovirus-infected cells and in cells infected with UV-irradiated reovirions, indicating that viral mRNA synthesis and subsequent steps in viral replication are not needed for apoptosis induction in avian reovirus-infected cells and that the number of inoculated virus particles, not their infectivity, is the critical factor for apoptosis induction by avian reovirus. Our finding that apoptosis is no longer induced when intracellular viral uncoating is blocked indicates that intraendosomal virion disassembly is required for apoptosis induction and that attachment and uptake of parental reovirions are not sufficient to cause apoptosis. Taken together, our results suggest that apoptosis is triggered from within the infected cell by viral products generated after intraendosomal uncoating of parental reovirions.
Secondary Structure of the 3′ Terminus of Hepatitis C Virus Minus-Strand RNA
Authors: Schuster Catherine , Isel Catherine , Imbert Isabelle , Ehresmann Chantal , Marquet Roland , Kieny Marie Paule 
Published: July 2002

ABSTRACT
The 3′-terminal ends of both the positive and negative strands of the hepatitis C virus (HCV) RNA, the latter being the replicative intermediate, are most likely the initiation sites for replication by the viral RNA-dependent RNA polymerase, NS5B. The structural features of the very conserved 3′ plus [(+)] strand untranslated region [3′ (+) UTR] are well established (K. J. Blight and C. M. Rice, J. Virol. 71:7345-7352, 1997). However, little information is available concerning the 3′ end of the minus [(−)] strand RNA. In the present work, we used chemical and enzymatic probing to investigate the conformation of that region, which is complementary to the 5′ (+) UTR and the first 74 nucleotides of the HCV polyprotein coding sequence. By combining our experimental data with computer predictions, we have derived a secondary-structure model of this region. In our model, the last 220 nucleotides, where initiation of the (+) strand RNA synthesis presumably takes place, fold into five stable stem-loops, forming domain I. Domain I is linked to an overall less stable structure, named domain II, containing the sequences complementary to the pseudoknot of the internal ribosomal entry site in the 5′ (+) UTR. Our results show that, even though the (−) strand 3′-terminal region has the antisense sequence of the 5′ (+) UTR, it does not fold into its mirror image. Interestingly, comparison of the replication initiation sites on both strands reveals common structural features that may play key functions in the replication process.
Mutations That Affect the Tropism of DA and GDVII Strains of Theiler's Virus In Vitro Influence Sialic Acid Binding and Pathogenicity
Authors: Jnaoui Karima , Minet Muriel , Michiels Thomas 
Published: July 2002

ABSTRACT
Theiler's murine encephalomyelitis virus (TMEV) is a natural pathogen of the mouse. The different strains of TMEV are divided into two subgroups according to the pathology they provoke. The neurovirulent strains GDVII and FA induce an acute fatal encephalitis, while persistent strains, like DA and BeAn, cause a chronic demyelinating disease associated with viral persistence in the central nervous system. Different receptor usage was proposed to account for most of the phenotype difference between neurovirulent and persistent strains. Persistent but not neurovirulent strains were shown to bind sialic acid. We characterized DA and GDVII derivatives adapted to grow on CHO-K1 cells. Expression of glycosaminoglycans did not influence infection of CHO-K1 cells by parental and adapted viruses. Mutations resulting from adaptation of DA and GDVII to CHO-K1 cells notably mapped to the well-characterized VP1 CD and VP2 EF loops of the capsid. Adaptation of the DA virus to CHO-K1 cells correlated with decreased sialic acid usage for entry. In contrast, adaptation of the GDVII virus to CHO-K1 cells correlated with the appearance of a weak sialic acid usage for entry. The sialic acid binding capacity of the GDVII variant resulted from a single amino acid mutation (VP1-51, Asn→Ser) located out of the sialic acid binding region defined for virus DA. Mutations affecting tropism in vitro and sialic acid binding dramatically affected the persistence and neurovirulence of the viruses.
Molecular Architecture of Adenovirus DNA Polymerase and Location of the Protein Primer
Authors: Brenkman Arjan B. , Breure Elise C. , van der Vliet Peter C. 
Published: July 2002

ABSTRACT
Adenovirus (Ad) DNA polymerase (pol) belongs to the distinct subclass of the polα family of DNA pols that employs the precursor terminal protein (pTP) as primer. Ad pol forms a stable heterodimer with this primer, and together, they bind specifically to the core origin in order to start replication. After initiation of Ad replication, the resulting pTP-trinucleotide intermediate jumps back and pTP starts to dissociate. Compared to free Ad pol, the pTP-pol complex shows reduced polymerase and exonuclease activities, but the reason for this is not understood. Furthermore, the interaction domains between these proteins have not been defined and the contribution of each protein to origin binding is unclear. To address these questions, we used oligonucleotides with a translocation block and show here that pTP binds at the entrance of the primer binding groove of Ad pol, thereby explaining the decreased synthetic activities of the pTP-pol complex and providing insight into how pTP primes Ad replication. Employing an exonuclease-deficient mutant polymerase, we further show that the polymerase and exonuclease active sites of Ad pol are spatially distinct and that the exonuclease activity of Ad pol is located at the N-terminal part of the protein. In addition, by probing the distances between both active sites and the surface of Ad pol, we show that Ad pol binds a DNA region of 14 to 15 nucleotides. Based on these results, a model for binding of the pTP-pol complex at the origin of replication is proposed.
Transcriptional Regulation of the Interleukin-6 Gene of Human Herpesvirus 8 (Kaposi's Sarcoma-Associated Herpesvirus)
Authors: Deng Hongyu , Song Moon Jung , Chu Julia T. , Sun Ren 
Published: July 2002

ABSTRACT
Human herpesvirus 8 (HHV-8; Kaposi's sarcoma-associated herpesvirus is linked to Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD), all of which are viewed as cytokine-driven malignancies. In particular, interleukin-6 (IL-6) has been found to promote the growth and proliferation of cells from KS and PEL. HHV-8 encodes a homologue of IL-6 (viral IL-6 [vIL-6]), which functions similarly to the cellular IL-6. Therefore, vIL-6 has been proposed to play an important role in tumor progression. Several groups have reported that vIL-6 is expressed from the HHV-8 genome at higher levels in PEL and MCD lesions than in KS lesions. However, it is not clear how vIL-6 expression is regulated. We characterized the transcription at the vIL-6 gene locus by Northern blot analysis and, in contrast to previous reports, we observed two distinct transcripts from induced PEL cell lines. This observation was confirmed by primer extension, as well as 5′ and 3′ rapid amplification of cDNA ends. Two transcription initiation sites and putative TATA boxes were mapped. A luciferase reporter system was used to show that each of the two putative TATA boxes contributed to vIL-6 promoter activity. Since virally encoded transcriptional activator Rta potently activates the viral lytic gene expression cascade, we examined the role of Rta in controlling vIL-6 gene expression and found that Rta activated the vIL-6 promoter. The Rta-responsive element was further mapped through a series of deletion constructs. Electrophoretic mobility shift assays demonstrated that Rta binds directly to the vIL-6 Rta-responsive element, and the core Rta-responsive element was mapped to a 26-bp region spanning from nucleotide 18315 to 18290 on the viral genome. We propose that the existence of two vIL-6 promoters offers opportunities for differential regulation of vIL-6 gene expression in different tissue types and may account for the variable vIL-6 levels observed in KS, PEL, and MCD.