bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of Human Immunodeficiency Virus Type 1 Replication prior to Reverse Transcription by Influenza Virus Stimulation
Authors: Pinto Ligia A. , Blazevic Vesna , Patterson Bruce K. , Mac Trubey C. , Dolan Matthew J. , Shearer Gene M. 
Published: July 2002

ABSTRACTIt is now recognized that, in addition to drug-mediated therapies against human immunodeficiency virus type 1 (HIV-1), the immune system can exert antiviral effects via CD8+T-cell-generated anti-HIV factors. This study demonstrates that (i) supernatants from peripheral blood mononuclear cells (PBMC) stimulated with influenza A virus inhibit replication of CCR5- and CXCR4-tropic HIV-1 isolates prior to reverse transcription; (ii) the HIV-suppressive supernatants can be generated by CD4- or CD8-depleted PBMC; (iii) this anti-HIV activity is partially due to alpha interferon (IFN-α), but not to IFN-γ, IFN-β, the β-chemokines MIP-1α, MIP-1β, and RANTES, or interleukin-16; (iv) the anti-HIV activity is generated equally well by PBMC cultured with either infectious or UV-inactivated influenza A virus; and (v) the antiviral activity can be generated by influenza A-stimulated PBMC from HIV-infected individuals. These findings represent a novel mechanism for inhibition of HIV-1 replication that differs from the previously described CD8 anti-HIV factors (MIP-1α, MIP-1β, RANTES, and CD8 antiviral factor).
Replicase Complex Genes of Semliki Forest Virus Confer Lethal Neurovirulence
Authors: Tuittila Minna T. , Santagati Maria G. , Röyttä Matias , Määttä Jorma A. , Hinkkanen Ari E. 
Published: July 2002

ABSTRACTSemliki Forest virus (SFV) is a mosquito-transmitted pathogen of small rodents, and infection of adult mice with SFV4, a neurovirulent strain of SFV, leads to lethal encephalitis in a few days, whereas mice infected with the avirulent A7(74) strain remain asymptomatic. In adult neurons, A7(74) is unable to form virions and hence does not reach a critical threshold of neuronal damage. To elucidate the molecular mechanisms of neurovirulence, we have cloned and sequenced the entire 11,758-nucleotide genome of A7(74) and compared it to the highly neurovirulent SFV4 virus. We found several sequence differences and sought to localize determinants conferring the neuropathogenicity by using a panel of chimeras between SFV4 and a cloned recombinant, rA774. We first localized virulence determinants in the nonstructural region by showing that rA774 structural genes combined with the SFV4 nonstructural genome produced a highly virulent virus, while a reciprocal recombinant was asymptomatic. In addition to several amino acid mutations in the nonstructural region, thensp3gene of rA774 displayed an opal termination codon and an in-frame 21-nucleotide deletion close to thensp4junction. Replacement in rA774 of the entirensp3gene with that of SFV4 reconstituted the virulent phenotype, whereas an arginine at the opal position significantly increased virulence, leading to clinical symptoms in mice. Completion of thensp3deletion in rA774 did not increase virulence. We conclude that the opal codon and amino acid mutations other than the deleted residues are mainly responsible for the attenuation of A7(74) and that the attenuating determinants reside entirely in the nonstructural region.
Activation of Transcription Factors NF-κB and NF-IL-6 by Human Immunodeficiency Virus Type 1 Protein R (Vpr) Induces Interleukin-8 Expression
Authors: Roux Philippe , Alfieri Caroline , Hrimech Mohammed , Cohen Eric A. , Tanner Jerome E. 
Published: July 2002

ABSTRACTHuman immunodeficiency virus (HIV)-positive individuals express elevated levels of interleukin-8 (IL-8), which is believed to be responsible for some of the clinical manifestations occurring during AIDS. We report here that virion-derived HIV type 1 (HIV-1) protein R (Vpr) increased IL-8 expression in primary T cells and macrophages, as well as in the T-cell line Jurkat, the monocytic cell line U937, and the epithelial cell line A549. Vpr appeared to increase IL-8 expression and IL-8 promoter activity by activating transcription factors NF-κB and NF-IL-6. Elevated Vpr was also shown to increase transcription of the NF-κB and NF-IL-6 enhancer-containing viral promoters for HIV, cytomegalovirus, and simian virus 40, as well as increase the expression of IL-6 and IL-10 in primary macrophages and in A549 cells, tumor necrosis factor alpha expression in primary T cells, and IL-6 and gamma interferon expression in U937 cells. These results suggest a new role for Vpr in the pathogenesis of HIV infection, namely, the activation of transcription factors NF-IL-6 and NF-κB.
Functional Differences between Human and Bovine Immunodeficiency Virus Tat Transcription Factors
Authors: Bogerd Hal P. , Wiegand Heather L. , Bieniasz Paul D. , Cullen Bryan R. 
Published: July 2002

ABSTRACT
Transcriptional transactivation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) promoter element by the essential viral Tat protein requires recruitment of positive transcription elongation factor b (P-TEFb) to the viral TAR RNA target. The recruitment of P-TEFb, which has been proposed to be necessary and sufficient for activation of viral gene expression, is mediated by the highly cooperative interaction of Tat and cyclin T1, an essential component of P-TEFb, with the HIV-1 TAR element. Species, such as rodents, that encode cyclin T1 variants that are unable to support TAR binding by the Tat-cyclin T1 heterodimer are also unable to support HIV-1 Tat function. In contrast, we here demonstrate that the bovine immunodeficiency virus (BIV) Tat protein is fully able to bind to BIV TAR both in vivo and in vitro in the absence of any cellular cofactor. Nevertheless, BIV Tat can specifically recruit cyclin T1 to the BIV TAR element, and this recruitment is as essential for BIV Tat function as it is for HIV-1 Tat activity. However, because the cyclin T1 protein does not contribute to TAR binding, BIV Tat is able to function effectively in cells from several species that do not support HIV-1 Tat function. Thus, BIV Tat, while apparently dependent on the same cellular cofactor as the Tat proteins encoded by other lentiviruses, is nevertheless unique in terms of the mechanism used to recruit the BIV Tat-cyclin T1 complex to the viral LTR promoter.
The cHS4 Insulator Increases the Probability of Retroviral Expression at Random Chromosomal Integration Sites
Authors: Rivella Stefano , Callegari John A. , May Chad , Tan Cui Wen , Sadelain Michel 
Published: July 2002

ABSTRACT

Retroviruses are highly susceptible to transcriptional silencing and position effects imparted by chromosomal sequences at their integration site. These phenomena hamper the use of recombinant retroviruses as stable gene delivery vectors. As insulators are able to block promoter-enhancer interactions and reduce position effects in some transgenic animals, we examined the effect of an insulator on the expression and structure of randomly integrated recombinant retroviruses. We used the cHS4 element, an insulator from the chicken β-like globin gene cluster, which has been shown to reduce position effects in transgenic
Drosophila
. A large panel of mouse erythroleukemia cells that bear a single copy of integrated recombinant retroviruses was generated without using drug selection. We show that the cHS4 increases the probability that integrated proviruses will express and dramatically decreases the level of de novo methylation of the 5′ long terminal repeat. These findings support a primary role of methylation in the silencing of retroviruses and suggest that cHS4 could be useful in gene therapy applications to overcome silencing of retroviral vectors.
Cell-Specific Modulation of Papovavirus Replication by Tumor Suppressor Protein p53
Authors: Lepik Dina , Ustav Mart 
Published: July 2002

ABSTRACT
Small DNA tumor viruses like human papillomaviruses, simian virus 40, and adenoviruses modulate the activity of cellular tumor suppressor proteins p53 and/or pRB. These viruses replicate as nuclear multicopy extrachromosomal elements during the S phase of the cell cycle, and it has been suggested that inactivation of p53 and pRb is necessary for directing the cells to the S phase. Mouse polyomavirus (Py), however, modulates only the pRB protein activity without any obvious interference with the action of p53. We show here that Py replication was not suppressed by the p53 protein indeed in all tested different mouse cell lines. In addition, E1- and E2-dependent papillomavirus origin replication was insensitive to the action of p53 in mouse cells. We show that in hamster (Chinese hamster ovary) or human (osteosarcoma 143) cell lines the replication of both Py and papillomavirus origins was efficiently blocked by p53. The block of Py replication in human and hamster cells is not caused by the downregulation of large T-antigen expression. The deletion analysis of the p53 protein shows that the RPA binding, proline-rich regulatory, DNA-binding, and oligomerization domains are necessary for p53 action in both replication systems. These results indicate that in mouse cells the p53 protein could be inactive for the suppression of papovavirus replication.
An Adenovirus Inhibitor of Tumor Necrosis Factor Alpha-Induced Apoptosis Complexes with Dynein and a Small GTPase
Authors: Lukashok Sophie A. , Tarassishin Leonid , Li Yongan , Horwitz Marshall S. 
Published: July 2002

ABSTRACTAdenoviruses (Ad) code for immunoregulatory and cytokine regulatory proteins, one of which is the early region 3, 14.7-kDa protein (Ad E3-14.7K), which has been shown to inhibit tumor necrosis factor alpha-induced apoptosis. In an effort to understand the mechanism of action of Ad E3-14.7K, we previously searched for cell proteins with which it interacted. Three Ad E3-14.7K-interacting proteins (FIP-1, -2, and -3) were isolated. FIP-1 is a small GTPase which was used in this report as bait in the yeast two-hybrid system to find other interacting cell targets. The search resulted in the isolation of a protein, which we called GIP-1 (GTPase-interacting protein) that subsequently was shown to be identical to one of the light-chain components of human dynein (TCTEL1). FIP-1 was able to bind both TCTEL1 and Ad E3-14.7K simultaneously and was necessary to form a complex in which the viral protein was associated with a microtubule-binding motor protein. The functional significance of these interactions is discussed with respect to the steps of the Ad life cycle which are microtubule associated.
Modulation of Dengue Virus Infection in Human Cells by Alpha, Beta, and Gamma Interferons
Authors: Diamond Michael S. , Roberts T. Guy , Edgil Dianna , Lu Betty , Ernst Joel , Harris Eva 
Published: July 2002

ABSTRACTA role for interferon (IFN) in modulating infection by dengue virus (DV) has been suggested by studies in DV-infected patients and IFN receptor-deficient mice. To address how IFN modulates DV type 2 infection, we have assayed IFN-α, -β, and -γ for the ability to enhance or diminish antibody-independent and antibody-dependent cell infection using a competitive, asymmetric reverse transcriptase-mediated PCR (RT-PCR) assay that quantitates positive and negative strands of viral RNA, a flow cytometric assay that measures viral antigen, and a plaque assay that analyzes virion production. Our data suggest that IFN-α and -β protect cells against DV infection in vitro. Treatment of hepatoma cells with IFN-α or -β decreases viral RNA levels greater than 1,000-fold, the percentage of cells infected 90 to 95%, and the amount of infectious virus secreted 150- to 100,000-fold. These results have been reproduced with several cell types and viral strains, including low-passage isolates. In contrast, IFN-γ has a more variable effect depending on the cell type and pathway of infection. Quantitative RT-PCR experiments indicate that IFN inhibits DV infection by preventing the accumulation of negative-strand viral RNA.
Induction of CD4+T-Cell-Independent Immunoglobulin Responses by Inactivated Influenza Virus
Authors: Sha Zhiyi , Compans Richard W. 
Published: July 2002

ABSTRACTThrough cognate interaction between antigen-specific B-cell and CD4+αβ T cells, the CD4+αβ T cells secrete cytokines that initiate immunoglobulin (Ig) class switching from IgM to IgG. In this study, we show that formalin-inactivated influenza PR8 virus induces virus-specific IgM and IgG responses in the absence of CD4+T cells and that all four subclasses of IgG are produced. The immunized CD4-deficient mice were also found to be completely protected against lethal infection with live, pathogenic influenza virus. The ability of CD4+T-cell-deficient mice to generate these IgG responses was not found to be impaired when these mice were depleted of CD8+T cells with an anti-CD8 monoclonal antibody. In contrast, αβ T-cell-deficient mice (TCRβ−/−) were not found to produce significant amounts of IgG upon immunization with formalin-inactivated PR8 virus. These results suggest that CD4−CD8−double-negative αβ T cells are playing a role in regulating Ig class switching in the absence of CD4+T cells.
Epstein-Barr Virus Nuclear Antigen 3C Activates the Latent Membrane Protein 1 Promoter in the Presence of Epstein-Barr Virus Nuclear Antigen 2 through Sequences Encompassing an Spi-1/Spi-B Binding Site
Authors: Zhao Bo , Sample Clare E. 
Published: July 2002

ABSTRACTThe Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA-3C) protein is a transcriptional regulator of viral and cellular genes that is essential for EBV-mediated immortalization of B lymphocytes in vitro. EBNA-3C can inhibit transcription through an association with the cellular DNA-binding protein Jκ, a function shared by EBNA-3A and EBNA-3B. Here, we report a mechanism by which EBNA-3C can activate transcription from the EBV latent membrane protein 1 (LMP-1) promoter in conjunction with EBNA-2. Jκ DNA-binding sites were not required for this activation, and a mutant EBNA-3C protein unable to bind Jκ activated transcription as efficiently as wild-type EBNA-3C, indicating that EBNA-3C can regulate transcription through a mechanism that is independent of Jκ. Furthermore, activation of the LMP-1 promoter is a unique function of EBNA-3C, not shared by EBNA-3A and EBNA-3B. The DNA element through which EBNA-3C activates the LMP-1 promoter includes a Spi-1/Spi-B binding site, previously characterized as an important EBNA-2 response element. Although this element has considerable homology to mouse immunoglobulin light chain promoter sequences to which the mouse homologue of Spi-1 binds with its dimerization partner IRF4, we demonstrate that the IRF4-like binding sites in the LMP-1 promoter do not play a role in EBNA-3C-mediated activation. Both EBNA-2 and EBNA-3C were required for transcription mediated through a 41-bp region of the LMP-1 promoter encompassing the Spi binding site. However, EBNA-3C had no effect on transcription mediated in conjunction with the EBNA-2 activation domain fused to the GAL4 DNA-binding domain, suggesting that it does not function as an adapter between EBNA-2 and the cellular transcriptional machinery. Like EBNA-2, EBNA-3C bound directly to both Spi-1 and Spi-B in vitro. This interaction was mediated by a region of EBNA-3C encompassing a likely basic leucine zipper (bZIP) domain and the ets domain of Spi-1 or Spi-B, reminiscent of interactions between bZIP and ets domains of other transcription factors that result in their targeting to DNA. There are many examples of regulation of the hematopoietic-specific Spi transcription factors through protein-protein interactions, and a similar regulation by EBNA-3C, in conjunction with EBNA-2, is likely to be an important and unique contribution of EBNA-3C to EBV-mediated immortalization.
Molecular Epidemiology of Hepatitis B Virus Variants in Nonhuman Primates
Authors: Grethe Stefanie , Heckel Jens-Ove , Rietschel Wolfram , Hufert Frank T. 
Published: July 2002

ABSTRACT

We characterized hepatitis B virus (HBV) isolates from sera of 21 hepatitis B virus surface antigen-positive apes, members of the families
Pongidae
and
Hylobatidae
(19 gibbon spp., 1 chimpanzee, and 1 gorilla). Sera originate from German, French, Thai, and Vietnamese primate-keeping institutions. To estimate the phylogenetic relationships, we sequenced two genomic regions, one located within the pre-S1/pre-S2 region and one including parts of the polymerase and the X protein open reading frames. By comparison with published human and ape HBV isolates, the sequences could be classified into six genomic groups. Four of these represented new genomic groups of gibbon HBV variants. The gorilla HBV isolate was distantly related to the chimpanzee isolate described previously. To confirm these findings, the complete HBV genome from representatives of each genomic group was sequenced. The HBV isolates from gibbons living in different regions of Thailand and Vietnam could be classified into four different phylogenetically distinct genomic groups. The same genomic groups were found in animals from European zoos. Therefore, the HBV infections of these apes might have been introduced into European primate-keeping facilities by direct import of already infected animals from different regions in Thailand. Taken together, our data suggest that HBV infections are indigenous in the different apes. One event involving transmission between human and nonhuman primates in the Old World of a common ancestor of human HBV genotypes A to E and the ape HBV variants might have occurred.
Adeno-Associated Virus Type 5 (AAV5) but Not AAV2 Binds to the Apical Surfaces of Airway Epithelia and Facilitates Gene Transfer
Authors: Zabner Joseph , Seiler Michael , Walters Robert , Kotin Robert M. , Fulgeras Wendy , Davidson Beverly L. , Chiorini John A. 
Published: July 2002

ABSTRACT
In the genetic disease cystic fibrosis, recombinant adeno-associated virus type 2 (AAV2) is being investigated as a vector to transfer CFTR cDNA to airway epithelia. However, earlier work has shown that the apical surface of human airway epithelia is resistant to infection by AAV2, presumably as a result of a lack of heparan sulfate proteoglycans on the apical surface. This inefficiency can be overcome by increasing the amount of vector or by increasing the incubation time. However, these interventions are not very practical for translation into a therapeutic airway-directed vector. Therefore, we examined the efficiency of other AAV serotypes at infecting human airway epithelia. When applied at low multiplicity of infection to the apical surface of differentiated airway epithelia we found that a recombinant AAV5 bound and mediated gene transfer 50-fold more efficiently than AAV2. Furthermore, in contrast to AAV2, AAV5-mediated gene transfer was not inhibited by soluble heparin. Recombinant AAV5 was also more efficient than AAV2 in transferring β-galactosidase cDNA to murine airway and alveolar epithelia in vivo. These data suggest that AAV5-derived vectors bind and mediate gene transfer to human and murine airway epithelia, and the tropism of AAV5 may be useful to target cells that are not permissive for AAV2.
Human Cytomegalovirus Up-Regulates the Phosphatidylinositol 3-Kinase (PI3-K) Pathway: Inhibition of PI3-K Activity Inhibits Viral Replication and Virus-Induced Signaling
Authors: Johnson Robert A. , Wang Xin , Ma Xiu-Li , Huong Shu-Mei , Huang Eng-Shang 
Published: July 2002

ABSTRACTInfection of quiescent fibroblasts with human cytomegalovirus (HCMV) was found to cause a rapid activation of cellular phosphatidylinositol 3-kinase (PI3-K). Maximum PI3-K activation occurred from 15 to 30 min postinfection. This activation was transient, and by 2 h postinfection (hpi), PI3-K activity had declined to preinfection levels. However, at 4 hpi, a second tier of PI3-K activation was detected, and PI3-K activity remained elevated relative to that of mock-infected cells for the remainder of infection. The cellular kinases Akt and p70S6K and the transcription factor NF-κB were activated in a PI3-K-dependent manner at similar times following HCMV infection. Analysis using UV-irradiated virus indicated that no viral protein synthesis was necessary for the first phase of PI3-K activation, but viral protein expression was required for the second tier of PI3-K activation. Treatment of infected fibroblasts with LY294002, a potent and specific inhibitor of PI3-K kinase activity, caused a 4-log decrease in viral titers. LY294002 did not inhibit viral entry, but it did decrease viral immediate-early gene expression. In addition, the protein levels of two viral early genes required for DNA replication, UL84 and UL44, were significantly lower in the presence of LY294002. Furthermore, viral DNA replication was strongly inhibited by LY294002 treatment. This inhibition of viral DNA replication could be reversed by adding back the products of PI3-K activity (PI-3,4-P2and PI-3,4,5-P3), demonstrating that the effect of LY294002 on the viral life cycle was specifically due to the inhibition of PI3-K activity. These results are the first to suggest that PI3-K mediates HCMV-induced activation of host cell mitogenic pathways. They also provide strong evidence that PI3-K activation is important for initiation of viral DNA replication and completion of the viral lytic life cycle.
Decay Kinetics of Human Immunodeficiency Virus-Specific CD8+T Cells in Peripheral Blood after Initiation of Highly Active Antiretroviral Therapy
Authors: Casazza Joseph P. , Betts Michael R. , Picker Louis J. , Koup Richard A. 
Published: July 2002

ABSTRACTWe measured the longitudinal responses to 95 HLA class I-restricted human immunodeficiency virus (HIV) epitopes and an immunodominant HLA A2-restricted cytomegalovirus (CMV) epitope in eight treatment-naive HIV-infected individuals, using intracellular cytokine staining. Patients were treated with highly active antiretroviral therapy (HAART) for a median of 78 weeks (range, 34 to 121 weeks). Seven of eight patients maintained an undetectable viral load for the duration of therapy. A rapid decline in HIV-specific CD8+T-cell response was observed at initiation of therapy. After an undetectable viral load was achieved, a slower decrease in HIV-specific CD8+T-cell response was observed that was well described by first-order kinetics. The median half-life for the rate of decay was 38.8 (20.3 to 68.0) weeks when data were expressed as percentage of peripheral CD8+T cells. In most cases, data were similar when expressed as the number of responding CD8+T cells per microliter of blood. In subjects who responded to more than one HIV epitope, rates of decline in response to the different epitopes were similar and varied by a factor of 2.2 or less. Discontinuation of treatment resulted in a rapid increase in HIV-specific CD8+T cells. Responses to CMV increased 1.6- and 2.8-fold within 16 weeks of initiation of HAART in two of three patients with a measurable CMV response. These data suggest that HAART quickly starts to restore CD8+T-cell responses to other chronic viral infections and leads to a slow decrease in HIV-specific CD8+T-cell response in HIV-infected patients. The slow decrease in the rate of CD8+T-cell response and rapid increase in response to recurrent viral replication suggest that the decrease in CD8+T-cell response observed represents a normal memory response to withdrawal of antigen.