bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Single-Cell-Level Phenotypic Assay for Residual Drug Susceptibility and Reduced Replication Capacity of Drug-Resistant Human Immunodeficiency Virus Type 1
Authors: Zhang Haili , Zhou Yan , Alcock Cecily , Kiefer Tara , Monie Daphne , Siliciano Janet , Li Quan , Pham Paul , Cofrancesco Joseph , Persaud Deborah , Siliciano Robert F. 
Published: January 2004

ABSTRACT

Human immunodeficiency virus type 1 (HIV-1)-infected individuals who develop drug-resistant virus during antiretroviral therapy may derive benefit from continued treatment for two reasons. First, drug-resistant viruses can retain partial susceptibility to the drug combination. Second, therapy selects for drug-resistant viruses that may have reduced replication capacities relative to archived, drug-sensitive viruses. We developed a novel single-cell-level phenotypic assay that allows these two effects to be distinguished and compared quantitatively. Patient-derived
gag-pol
sequences were cloned into an HIV-1 reporter virus that expresses an endoplasmic reticulum-retained Env-green fluorescent protein fusion. Flow cytometric analysis of single-round infections allowed a quantitative analysis of viral replication over a 4-log dynamic range. The assay faithfully reproduced known in vivo drug interactions occurring at the level of target cells. Simultaneous analysis of single-round infections by wild-type and resistant viruses in the presence and absence of the relevant drug combination divided the benefit of continued nonsuppressive treatment into two additive components, residual virus susceptibility to the drug combination and selection for drug-resistant variants with diminished replication capacities. In some patients with drug resistance, the dominant circulating viruses retained significant susceptibility to the combination. However, in other cases, the dominant drug-resistant viruses showed no residual susceptibility to the combination but had a reduced replication capacity relative to the wild-type virus. In this case, simplification of the regimen might still allow adequate suppression of the wild-type virus. In a third pattern, the resistant viruses had no residual susceptibility to the relevant drug regimen but nevertheless had a replication capacity equivalent to that of wild-type virus. In such cases, there is no benefit to continued treatment. Thus, the ability to simultaneously analyze residual susceptibility and reduced replication capacity of drug-resistant viruses may provide a basis for rational therapeutic decisions in the setting of treatment failure.
Low Doses of Hepadnavirus Induce Infection of the Lymphatic System That Does Not Engage the Liver
Authors: Michalak Tomasz I. , Mulrooney Patricia M. , Coffin Carla S. 
Published: January 2004

ABSTRACT

Woodchuck hepatitis virus (WHV), which is closely related to human hepatitis B virus and is considered to be principally hepatotropic, invades the host's lymphatic system and persists in lymphoid cells independently of whether the infection is symptomatic and serologically evident or concealed. In this study, we show, with the woodchuck model of hepatitis B, that hepadnavirus can establish an infection that engages the lymphatic system, but not the liver, and persists in the absence of virus serological markers, including antiviral antibodies. This primary occult infection is caused by wild-type virus invading the host at a quantity usually not greater than 10
3
virions. It is characterized by trace virus replication progressing in lymphatic organs and peripheral lymphoid cells that, with time, may also spread to the liver. The infection is transmissible to virus-naive hosts as an asymptomatic, indefinitely long, occult carriage of small amounts of biologically competent virus. In contrast to residual silent WHV persistence, which normally endures after the resolution of viral hepatitis and involves the liver, primary occult infection restricted to the lymphatic system does not protect against reinfection with a large, liver-pathogenic WHV dose; however, the occult infection is associated with a swift recovery from hepatitis caused by the superinfection. Our study documents that the lymphatic system is the primary target of WHV infection when small quantities of virions invade a susceptible host.
Perforin and Gamma Interferon-Mediated Control of Coronavirus Central Nervous System Infection by CD8 T Cells in the Absence of CD4 T Cells
Authors: Bergmann Cornelia C. , Parra Beatriz , Hinton David R. , Ramakrishna Chandran , Dowdell Konechi C. , Stohlman Stephen A. 
Published: January 2004

ABSTRACTInfection of the central nervous system (CNS) with the neurotropic JHM strain of mouse hepatitis virus produces acute and chronic demyelination. The contributions of perforin-mediated cytolysis and gamma interferon (IFN-γ) secretion by CD8+T cells to the control of infection and the induction of demyelination were examined by adoptive transfer into infected SCID recipients. Untreated SCID mice exhibited uncontrolled virus replication in all CNS cell types but had little or no demyelination. Memory CD8+T cells from syngeneic wild-type (wt), perforin-deficient, or IFN-γ-deficient (GKO) donors all trafficked into the infected CNS in the absence of CD4+T cells and localized to similar areas. Although CD8+T cells from all three donors suppressed virus replication in the CNS, GKO CD8+T cells expressed the least antiviral activity. A distinct viral antigen distribution in specific CNS cell types revealed different mechanisms of viral control. While wt CD8+T cells inhibited virus replication in all CNS cell types, cytolytic activity in the absence of IFN-γ suppressed the infection of astrocytes, but not oligodendroglia. In contrast, cells that secreted IFN-γ but lacked cytolytic activity inhibited replication in oligodendroglia, but not astrocytes. Demyelination was most severe following viral control by wt CD8+T cells but was independent of macrophage infiltration. These data demonstrate the effective control of virus replication by CD8+T cells in the absence of CD4+T cells and support the necessity for the expression of distinct effector mechanisms in the control of viral replication in distinct CNS glial cell types.
In Vivo Expansion of the Residual Tumor Antigen-Specific CD8+T Lymphocytes That Survive Negative Selection in Simian Virus 40 T-Antigen-Transgenic Mice
Authors: Schell Todd D. 
Published: January 2004

ABSTRACTMice that express the viral oncoprotein simian virus 40 (SV40) large T antigen (T-Ag) as a transgene provide useful models for the assessment of the state of the host immune response in the face of spontaneous tumor progression. Line SV11 (H2b) mice develop rapidly progressing choroid plexus tumors due to expression of full-length T-Ag from the SV40 promoter. In addition, T-Ag expression in the thymus of SV11 mice results in the deletion of CD8+T cells specific for the three H2b-restricted immunodominant epitopes of T-Ag. Whether CD8+T cells specific for the immunorecessive H2-Db-restricted epitope V of T-Ag survive negative selection in SV11 mice has not been determined. Immunization of SV11 mice with rVV-ES-V, a recombinant vaccinia virus expressing epitope V as a minigene, resulted in the induction of weak, but reproducible, epitope V-specific cytotoxic T-lymphocyte (CTL) responses. This weak lytic response corresponded with a decreased frequency of epitope V-specific CTL that could be recruited in SV11 mice. In addition, CTL lines derived from rVV-ES-V-immunized SV11 mice had reduced avidities compared to that seen with CTL derived from healthy mice. Despite this initial weak response, significant numbers of epitope V-specific CD8+T cells were detected in SV11 mice ex vivo following a priming-boosting approach and these cells demonstrated high avidity for epitope V. The results suggest that low numbers of tumor-reactive CD8+T cells with high avidity for epitope V survive negative selection in SV11 mice but can be expanded by specific boosting approaches in the tumor bearing host.
Phenotype of a Herpes Simplex Virus Type 1 Mutant That Fails To Express Immediate-Early Regulatory Protein ICP0
Authors: Everett Roger D. , Boutell Chris , Orr Anne 
Published: January 2004

ABSTRACT
Herpes simplex virus type 1 (HSV-1) immediate-early (IE) regulatory protein ICP0 is required for efficient progression of infected cells into productive lytic infection, especially in low-multiplicity infections of limited-passage human fibroblasts. We have used single-cell-based assays that allow detailed analysis of the ICP0-null phenotype in low-multiplicity infections of restrictive cell types. The major conclusions are as follows: (i) there is a threshold input multiplicity above which the mutant virus replicates normally; (ii) individual cells infected below the threshold multiplicity have a high probability of establishing a nonproductive infection; (iii) such nonproductively infected cells have a high probability of expressing IE products at 6 h postinfection; (iv) even at 24 h postinfection, IE protein-positive nonproductively infected human fibroblast cells exceed the number of cells that lead to plaque formation by up to 2 orders of magnitude; (v) expression of individual IE proteins in a proportion of the nonproductively infected cells is incompletely coordinated; (vi) the nonproductive cells can also express early gene products at low frequencies and in a stochastic manner; and (vii) significant numbers of human fibroblast cells infected at low multiplicity by an ICP0-deficient virus are lost through cell death. We propose that in the absence of ICP0 expression, HSV-1 infected human fibroblasts can undergo a great variety of fates, including quiescence, stalled infection at a variety of different stages, cell death, and, for a minor population, initiation of formation of a plaque.
Identification of a Common HLA-DP4-Restricted T-Cell Epitope in the Conserved Region of the Respiratory Syncytial Virus G Protein
Authors: de Waal L. , Yüksel S. , Brandenburg A. H. , Langedijk J. P. M. , Sintnicolaas K. , Verjans G. M. G. M. , Osterhaus A. D. M. E. , de Swart R. L. 
Published: January 2004

ABSTRACTThe cellular immune response to respiratory syncytial virus (RSV) is important in both protection and immunopathogenesis. In contrast to HLA class I, HLA class II-restricted RSV-specific T-cell epitopes have not been identified. Here, we describe the generation and characterization of two human RSV-specific CD4+-T-cell clones (TCCs) associated with type 0-like cytokine profiles. TCC 1 was specific for the matrix protein and restricted over HLA-DPB1*1601, while TCC 2 was specific for the attachment protein G and restricted over either HLA-DPB1*0401 or -0402. Interestingly, the latter epitope is conserved in both RSV type A and B viruses. Given the high allele frequencies of HLA-DPB1*0401 and -0402 worldwide, this epitope could be widely recognized and boosted by recurrent RSV infections. Indeed, peptide stimulation of peripheral blood mononuclear cells from healthy adults resulted in the detection of specific responses in 8 of 13 donors. Additional G-specific TCCs were generated from three of these cultures, which recognized the identical (n= 2) or almost identical (n= 1) HLA-DP4-restricted epitope as TCC 2. No significant differences were found between the capacities of cell lines obtained from infants with severe (n= 41) or mild (n= 46) RSV lower respiratory tract infections to function as antigen-presenting cells to the G-specific TCCs, suggesting that the severity of RSV disease is not linked to the allelic frequency of HLA-DP4. In conclusion, we have identified an RSV G-specific human T helper cell epitope restricted by the widely expressed HLA class II alleles DPB1*0401 and -0402. Its putative role in protection and/or immunopathogenesis remains to be determined.
Activation of the Early-Late Switch in Adenovirus Type 5 Major Late Transcription Unit Expression by L4 Gene Products
Authors: Farley Daniel C. , Brown Jason L. , Leppard Keith N. 
Published: January 2004

ABSTRACT

The adenovirus major late transcription unit (MLTU) encodes multiple proteins from five regions, L1 to L5, through differential splicing and polyadenylation. MLTU expression is temporally regulated; only a single product from L1 (52/55K) is expressed prior to replication, but a subsequent switch, the mechanism of which has not been defined, leads to full expression that encompasses L1 IIIa and all L2 to L5 products. Transfection of a plasmid containing the complete MLTU gave a full array of proteins in proportions similar to those in a late infection, and in a time course, the temporal pattern of expression in a natural infection was reproduced. However, a plasmid truncated after the L3 poly(A) site exclusively expressed the L1 52/55K protein and was defective in the switch to full gene expression from L1 to L3. The L4 33K protein, supplied in
trans
, was sufficient to upregulate cytoplasmic mRNA for MLTU products characteristic of the late pattern of expression to levels comparable to those produced by the full-length MLTU. There was a corresponding increase in expression of the L1 IIIa, L2, and L3 proteins, except hexon. Hexon protein expression additionally required both the L4 100K protein in
trans
and sequences downstream of the L3 poly(A) site in
cis
. These results indicate that induction of L4 protein expression is a key event in the early-late switch in MLTU expression, which we propose is precipitated by small amounts of L4 expression in a feed-forward activation mechanism.
Nuclear Factor κB-Dependent Activation of the Antiapoptoticbfl-1Gene by the Epstein-Barr Virus Latent Membrane Protein 1 and Activated CD40 Receptor
Authors: D'Souza Brendan N. , Edelstein Leonard C. , Pegman Pamela M. , Smith Sinéad M. , Loughran Sinéad T. , Clarke Ann , Mehl Anja , Rowe Martin , Gélinas Céline , Walls Dermot 
Published: January 2004

ABSTRACTSuppression of the cellular apoptotic program by the oncogenic herpesvirus Epstein-Barr virus (EBV) is central to both the establishment of latent infection and the development of EBV-associated malignancies. We have previously shown that expression of the EBV latent membrane protein 1 (LMP1) in Burkitt's lymphoma cell lines leads to increased mRNA levels from the cellular antiapoptoticbfl-1gene (also known asA1). Furthermore, ectopic expression of Bfl-1 in an EBV-positive cell line exhibiting a latency type 1 infection protects against apoptosis induced by growth factor deprivation (B. N. D'Souza, M. Rowe, and D. Walls, J. Virol.74:6652-6658, 2000). We now report that LMP1 drivesbfl-1promoter activity through interactions with components of the tumor necrosis factor receptor (TNFR)/CD40 signaling pathway. We present evidence that this process is NF-κB dependent, involves the recruitment of TNFR-associated factor 2, and is mediated to a greater extent by the carboxyl-terminal activating region 2 (CTAR2) relative to the CTAR1 domain of LMP1. Activation of CD40 receptor also led to increasedbfl-1mRNA levels and an NF-κB-dependent increase inbfl-1promoter activity in Burkitt's lymphoma-derived cell lines. We have delineated a 95-bp region of the promoter that functions as an LMP1-dependent transcriptional enhancer in this cellular context. This sequence contains a novel NF-κB-like binding motif that is essential for transactivation ofbfl-1by LMP1, CD40, and the NF-κB subunit protein p65. These findings highlight the role of LMP1 as a mediator of EBV-host cell interactions and may indicate an important route by which it exerts its cellular growth transforming properties.
A Cytomegalovirus Inhibitor of Gamma Interferon Signaling Controls Immunoproteasome Induction
Authors: Khan Selina , Zimmermann Albert , Basler Michael , Groettrup Marcus , Hengel Hartmut 
Published: January 2004

ABSTRACTBoth human and mouse cytomegaloviruses (HCMV and MCMV) avoid peptide presentation through the major histocompatibility complex (MHC) class I pathway to CD8+T cells. Within the MHC class I pathway, the vast majority of antigenic peptides are generated by the proteasome system, a multicatalytic protease complex consisting of constitutive subunits, three of which can be replaced by enzymatically active gamma interferon (IFN-γ)-inducible subunits, i.e., LMP2, LMP7, and MECL1, to form the so-called immunoproteasomes. Here, we show that steady-state levels of immunoproteasomes are readily formed in response to MCMV infection in the liver. In contrast, the incorporation of immunoproteasome subunits was prevented in MCMV-infected, as well as HCMV-infected, fibroblasts in vitro. Likewise, the expression of the IFN-γ-inducible proteasome regulator PA28αβ was also impaired in MCMV-infected cells. Both MCMV and HCMV did not alter the constitutive-subunit composition of proteasomes in infected cells. Quantitative assessment of LMP2, MECL1, and LMP7 transcripts revealed that the inhibition of immunoproteasome formation occurred at a pretranscriptional level. Remarkably, a targeted deletion of the MCMV geneM27, encoding an inhibitor of STAT2 that disrupts IFN-γ receptor signaling, largely restored transcription and protein expression of immunoproteasome subunits in infected cells. While CMV block peptide transport and MHC class I assembly by posttranslational strategies, immunoproteasome assembly, and thus the repertoire of proteasomal peptides, is controlled by pretranscriptional mechanisms. We hypothesize that the blockade of immunoproteasome formation has considerable consequences for shaping the CD8+-T-cell repertoire during the effector phase of the immune response.
Chimeric Human Immunodeficiency Virus Type 1 (HIV-1) Virions Containing HIV-2 or Simian Immunodeficiency Virus Nef Are Resistant to Cyclosporine Treatment
Authors: Khan Mahfuz , Jin Lingling , Huang Ming Bo , Miles Lesa , Bond Vincent C. , Powell Michael D. 
Published: January 2004

ABSTRACT
The viral protein Nef and the cellular factor cyclophilin A are both required for full infectivity of human immunodeficiency virus type 1 (HIV-1) virions. In contrast, HIV-2 and simian immunodeficiency virus (SIV) do not incorporate cyclophilin A into virions or need it for full infectivity. Since Nef and cyclophilin A appear to act in similar ways on postentry events, we determined whether chimeric HIV-1 virions that contained either HIV-2 or SIV Nef would have a direct effect on cyclophilin A dependence. Our results show that chimeric HIV-1 virions containing either HIV-2 or SIV Nef are resistant to treatment by cyclosporine and enhance the infectivity of virions with mutations in the cyclophilin A binding loop of Gag. Amino acids at the C terminus of HIV-2 and SIV are necessary for inducing cyclosporine resistance. However, transferring these amino acids to the C terminus of HIV-1 Nef is insufficient to induce cyclosporine resistance in HIV-1. These results suggest that HIV-2 and SIV Nef are able to compensate for the need for cyclophilin A for full infectivity and that amino acids present at the C termini of these proteins are important for this function.
African Swine Fever Virus Multigene Family 360 and 530 Genes Affect Host Interferon Response
Authors: Afonso C. L. , Piccone M. E. , Zaffuto K. M. , Neilan J. , Kutish G. F. , Lu Z. , Balinsky C. A. , Gibb T. R. , Bean T. J. , Zsak L. , Rock D. L. 
Published: January 2004

ABSTRACTAfrican swine fever virus (ASFV) multigene family 360 and 530 (MGF360/530) genes affect viral growth in macrophage cell cultures and virulence in pigs (L. Zsak, Z. Lu, T. G. Burrage, J. G. Neilan, G. F. Kutish, D. M. Moore, and D. L. Rock, J. Virol.75:3066-3076, 2001). The mechanism by which these novel genes affect virus-host interactions is unknown. To define MGF360/530 gene function, we compared macrophage transcriptional responses following infection with parental ASFV (Pr4) and an MGF360/530 deletion mutant (Pr4Δ35). A swine cDNA microarray containing 7,712 macrophage cDNA clones was used to compare the transcriptional profiles of swine macrophages infected with Pr4 and Pr4Δ35 at 3 and 6 h postinfection (hpi). While at 3 hpi most (7,564) of the genes had similar expression levels in cells infected with either virus, 38 genes had significantly increased (>2.0-fold,P< 0.05) mRNA levels in Pr4Δ35-infected macrophages. Similar up-regulation of these genes was observed at 6 hpi. Viral infection was required for this induced transcriptional response. Most Pr4Δ35 up-regulated genes were part of a type I interferon (IFN) response or were genes that are normally induced by double-stranded RNA and/or viral infection. These included monocyte chemoattractant protein, transmembrane protein 3, tetratricopeptide repeat protein 1, a ubiquitin-like 17-kDa protein, ubiquitin-specific protease ISG43, an RNA helicase DEAD box protein, GTP-binding MX protein, the cytokine IP-10, and the PKR activator PACT. Differential expression of IFN early-response genes in Pr4Δ35 relative to Pr4 was confirmed by Northern blot analysis and real-time PCR. Analysis of IFN-α mRNA and secreted IFN-α levels at 3, 8, and 24 hpi revealed undetectable IFN-α in mock- and Pr4-infected macrophages but significant IFN-α levels at 24 hpi in Pr4Δ35-infected macrophages. The absence of IFN-α in Pr4-infected macrophages suggests that MGF360/530 genes either directly or indirectly suppress a type I IFN response. An inability to suppress host type I IFN responses may account for the growth defect of Pr4Δ35 in macrophages and its attenuation in swine.
Glycine Decarboxylase Mediates a Postbinding Step in Duck Hepatitis B Virus Infection
Authors: Li Jisu , Tong Shuping , Lee Hong Bock , Perdigoto Ana Luisa , Spangenberg Hans Christian , Wands Jack R. 
Published: January 2004

ABSTRACT

Envelope protein precursors of many viruses are processed by a basic endopeptidase to generate two molecules, one for receptor binding and the other for membrane fusion. Such a cleavage event has not been demonstrated for the hepatitis B virus family. Two binding partners for duck hepatitis B virus (DHBV) pre-S envelope protein have been identified. Duck carboxypeptidase D (DCPD) interacts with the full-length pre-S protein and is the DHBV docking receptor, while duck glycine decarboxylase (DGD) has the potential to bind several deletion constructs of the pre-S protein in vitro. Interestingly, DGD but not DCPD expression was diminished following prolonged culture of primary duck hepatocytes (PDH), which impaired productive DHBV infection. Introduction of exogenous DGD promoted formation of protein-free viral genome, suggesting restoration of several early events in viral life cycle. Conversely, blocking DGD expression in fresh PDH by antisense RNA abolished DHBV infection. Moreover, addition of DGD antibodies soon after virus binding reduced endogenous DGD protein levels and impaired production of covalently closed circular DNA, the template for DHBV gene expression and genome replication. Our findings implicate this second pre-S binding protein as a critical cellular factor for productive DHBV infection. We hypothesize that DCPD, a molecule cycling between the cell surface and the
trans
-Golgi network, targets DHBV particles to the secretary pathway for proteolytic cleavage of viral envelope protein. DGD represents the functional equivalent of other virus receptors in its interaction with processed viral particles.