pinecone/core-2020-05-10-deduplication huggingface dataset:
Role of the Myxoma Virus Soluble CC-Chemokine Inhibitor Glycoprotein, M-T1, during Myxoma Virus Pathogenesis

AbstractMyxoma virus is a poxvirus that causes a virulent systemic disease called myxomatosis in European rabbits. Like many poxviruses, myxoma virus encodes a variety of secreted proteins that subvert the antiviral activities of host cytokines. It was recently demonstrated that the myxoma virus M-T1 glycoprotein is a member of a large poxvirus family of secreted proteins that bind CC-chemokines and inhibit their chemoattractant activities in vitro. To determine the biological role of M-T1 in contributing to myxoma virus virulence, we constructed a recombinant M-T1-deletion mutant virus that was defective in M-T1 expression. Here, we demonstrate that M-T1 is expressed continuously during the course of myxoma virus infection as a highly stable 43-kDa glycoprotein and is dispensable for virus replication in vitro. Deletion of M-T1 had no significant effects on disease progression or in the overall mortality rate of infected European rabbits but heightened the localized cellular inflammation in primary tissue sites during the initial 2 to 3 days of infection. In the absence of M-T1 expression, deep dermal tissues surrounding the primary site of virus inoculation showed a dramatic increase in infiltrating leukocytes, particularly monocytes/macrophages, but these phagocytes remained relatively ineffective at clearing virus infection, likely due to the concerted properties of other secreted myxoma virus proteins. We conclude that M-T1 inhibits the chemotactic signals required for the influx of monocytes/macrophages during the acute-phase response of myxoma virus infection in vivo, as predicted by its ability to bind and inhibit CC-chemokines in vitro
Regulatable Expression of the Interferon-Induced Double-Stranded RNA Dependent Protein Kinase PKR Induces Apoptosis and Fas Receptor Expression

AbstractPKR is an interferon-induced dsRNA-dependent protein kinase involved in the antiviral response as well as in cell growth and differentiation. Studies using a transdominant negative mutant of PKR also have implicated the kinase in tumor suppression and apoptosis. However, functional studies of PKR have been hampered by the lack of a suitable expression system. In this study, we used a tetracycline-regulated inducible system in NIH3T3 cells to investigate the involvement of PKR in programmed cell death (apoptosis). We show that expression of wild-type PKR causes apoptosis and correlates with increased mRNA levels for the Fas receptor, a member of the tumor necrosis family of proteins. Expression of an inactive form of PKR (K296R) or the vector alone did not induce apoptosis or elevate Fas mRNA levels. Our results clearly demonstrate that expression of an active form of PKR triggers apoptosis, possibly through upregulation of the Fas receptor
Detection of Epstein–Barr Virus (EBV) in Hepatocellular Carcinoma Tissue: A Novel EBV Latency Characterized by the Absence of EBV-Encoded Small RNA Expression

AbstractIn this study, we investigated the presence of Epstein–Barr virus (EBV) in liver tissue from 35 patients with hepatocellular carcinoma (HCC). EBV DNA was detected in 13 patients (37%) by Southern blot hybridization. In 10 of these patients, EBV DNA was present in tumor tissue only, whereas in the other 3, it was detected in both tumor and nontumor tissues. The quantity of EBV DNA detected was equivalent to 1–10 viral DNA molecules/100 cells. EBV-determined nuclear antigen was detected in 7–13% of the carcinoma cells in three tumor tissue samples that contained approximately one copy of the EBV genome/10 cells. A single terminal fragment of EBV DNA was identified in these tissues, suggesting that the EBV-infected cells in HCC represent clonal proliferation. Western blotting and reverse transcription–polymerase chain reaction analyses demonstrated that these three tumor tissue specimens were positive for EBV-determined nuclear antigen 1 and BamHI A transcripts but were negative for the other latent EBV products, including EBV-encoded small RNA. The results indicated that there is a high EBV load in HCC tissue and that all of the HCC tissue examined showed a novel pattern of EBV latency characterized by absence of EBV-encoded small RNA expression
Bovine Herpesvirus 1-Induced Apoptotic Cell Death: Role of Glycoprotein D

AbstractBovine herpesvirus 1 (BHV-1) induces apoptotic cell death in peripheral blood mononuclear cells and in bovine B lymphoma (BL-3) cells. Attachment but not penetration of BHV-1 is necessary to induce apoptosis in target cells, suggesting that one or more BHV-1 envelope glycoproteins could be involved in the activation of the apoptotic process. In the present study, we demonstrate that, although BHV-1 virions devoid of glycoprotein D (BHV-1 gD−/−) still bind to BL-3 cells, they are no longer able to induce apoptosis. In contrast, virions that contain glycoprotein D (gD) in the viral envelope but do not genetically encode gD (BHV-1 gD−/+) induce a level of apoptosis comparable to that produced by wild-type (wt) BHV-1. In addition, monoclonal antibodies directed against gD, but not against gB or gC, strongly reduced the high levels of apoptosis induced by BHV-1. These observations demonstrate that the induction of apoptosis is directly due to BHV-1 viral particles harboring gD in the viral envelope. Interestingly, binding of affinity-purified gD to BL-3 cells did not induce apoptosis but inhibited the ability of wt BHV-1 to induce apoptosis. Altogether, these results provide evidence for the direct or indirect involvement of gD in the mechanism by which BHV-1 induces apoptosis
Transduction ofAedes aegyptiMosquitoes with Vectors Derived fromAedesDensovirus

AbstractAedesdensovirus (AeDNV)-based constructs that express green fluorescent protein (GFP) from either the P7 or the P61 promoter were made. The construct in which GFP protein was expressed as a fusion protein to the C-terminus of NS1 (NS1–GFP) showed the highest level of GFP expression. This hybrid NS1–GFP protein preserved the biological functions of the parental proteins: it showed GFP fluorescence, it stimulated expression from the virus promoters, and it facilitated rescue and replication of the cloned AeDNV genome. Similar to NS1, the hybrid NS1–GFP localized in the nucleus predominantly in a punctate pattern. Transducing virus particles carrying the NS1–GFP gene infected mosquito larvae. Expression of GFP was detected as early as 48 h postinfection and in larval and pupal stages. Midgut, hindgut, and Malpighian tubule cells expressed GFP soon after transduction. However, the anal papillae were the most commonly infected organ system. The anal papillae are syncytia and regulate ion concentration in the hemolymph of mosquito larvae, and they might be a novel route of mosquito larvae infection with densoviruses
Packaging of AeDNV–GFP Transducing Virus by Expression of Densovirus Structural Proteins from a Sindbis Virus Expression System

AbstractGenetic recombination resulting in the production of wild-type infectious virus is an obstacle in the current system for producing densovirus transducing particles. In order to eliminate this problem, a double subgenomic Sindbis virus (TE/3′2J/VP) was engineered that expresses the structural proteins (VPs) ofAedesdensonucleosis virus (AeDNV) from the second subgenomic promoter. Expression of AeDNV VPs from TE/3′2J/VP was confirmed by Northern analysis of RNA from infected C6/36 (Aedes albopictus) cells and by indirect immunofluorescence in infected C6/36 cells and BHK-21 cells. TE/3′2J/VP was used to infect C6/36 cells transfected with p7NS1–GFP, a plasmid expressing the nonstructural genes of AeDNV and green fluorescent protein (GFP) as a reporter gene. This infection resulted in the production of AeDNV–GFP transducing virus, which is infectious to C6/36 cells andAedes aegyptilarvae, as determined by GFP expression. The TE/3′2J/VP packaging system produced titers of transducing virus comparable to those produced by the standard two-plasmid method. The possibility of recombination resulting in wild-type infectious virus in transducing densovirus stocks was eliminated by employing an RNA virus expression system to supply AeDNV structural proteins
Transcription of the Genome of the Filamentous Bacteriophage cf from Both Plus and Minus DNA Strands

AbstractThe filamentous bacteriophage cf infects the bacterium Xanthomonas campestris pv. citri. Northern blot analysis with probes derived from various restriction fragments of cf replicative form (RF) DNA has revealed the presence of five major phage-specific transcripts in infected cells. Four of these transcripts were shown to be derived from the region of the cf genome extending from gene II to gene VIII and are consistent with the cascade model of transcription proposed for Ff coliphages. These transcripts overlap with each other and terminate upstream of an efficient Rho-independent transcription terminator. Unlike the well-characterized Ff phages, in which only the minus strand of viral DNA serves as a transcription template, both strands of the RF DNA of phage cf appeared to be transcribed. Thus one of the five major cf transcripts was shown to be derived from a region of the viral minus strand that contains an open reading frame encoding a putative polypeptide of 165 amino acids. Primer extension analysis mapped the transcriptional initiation site of this RNA to a cytosine residue at position 870. A partial transcription map of phage cf revealed two independent regions of transcriptional activity. The region with the highest activity coincides with that encoding the polypeptides required in the largest amounts during the cf infection cycle
Membrane Fusion by Surrogate Receptor-Bound Influenza Haemagglutinin

AbstractIn influenza infections, haemagglutinin (HA) mediates the fusion of virus and cellular membranes at endosomal pH, between pH 5 and 6.In vitro, when reconstituted into virosomes, efficient fusion requires target membranes to contain sialic acid receptors or receptor analogues. In the experiments reported, lipid-associated anti-HA monoclonal Fab′ fragments were used as surrogate receptors to investigate the fusion capacity of receptor-bound HA compared with unbound HA. The conclusions are drawn, in contrast to those from previous studies, that bound HA can mediate fusion and that fusion mainly involves bound HA when the liposome targets are densely packed with surrogate receptors
Transcription Mapping and Characterization of 284R and 121R Proteins Produced from Early Region 3 of Bovine Adenovirus Type 3

AbstractWe established the transcription map of early region (E) 3 of bovine adenovirus 3 (BAV-3) by Northern blot, S1 nuclease protection assays, cDNA sequencing, and RT-PCR analysis. Five major classes of mRNAs were identified, which shared the 3′ ends. Four classes of mRNAs transcribed from the E3 promoter also shared the 5′ end, while one major class of mRNA transcribed from the major late promoter contained a tripartite leader sequence at the 5′ end. These five transcripts have the potential to encode four proteins, namely 284R, 121R, 86R, and 82R. To identify the proteins, rabbit antiserum was prepared using a bacterial fusion protein encoding 284R or 121R protein. Serum against 284R immunoprecipitated protein of 26–32 kDa in in vitro translated and transcribed mRNA and three proteins of 48, 67, and 125 kDa from BAV-3-infected cells. Western blots and enzymatic digestions confirmed that the 284R protein is a glycoprotein, which contains only N-linked oligosaccharides, both high mannose (48 kDa) and complex types (67 kDa). Serum against 121R immunoprecipitated a protein of 14.5 kDa from in vitro translated and transcribed mRNA and BAV-3-infected cells. Although 121R protein shows limited sequence similarity to a 14.7-kDa protein of human adenovirus 5, the 284R protein appears to be unique to BAV-3. Since proteins encoded by the E3 region appear to influence adenovirus pathogenesis, the 284R protein may contribute to the unique pathogenic properties of BAV-3
Hyaluronan Synthesis in Virus PBCV-1-Infected Chlorella-like Green Algae

AbstractWe previously reported that the chlorella virus PBCV-1 genome encodes an authentic, membrane-associated glycosyltransferase, hyaluronan synthase (HAS). Hyaluronan, a linear polysaccharide chain composed of alternating β1,4-glucuronic acid and β1,3-N-acetylglucosamine groups, is present in vertebrates as well as a few pathogenic bacteria. Studies of infected cells show that the transcription of the PBCV-1hasgene begins within 10 min of virus infection and ends at 60–90 min postinfection. The hyaluronan polysaccharide begins to accumulate as hyaluronan-lyase sensitive, hair-like fibers on the outside of the chlorella cell wall by 15–30 min postinfection; by 240 min postinfection, the infected cells are coated with a dense fibrous network. This hyaluronan slightly reduces attachment of a second chlorella virus to the infected algae. An analysis of 41 additional chlorella viruses indicates that many, but not all, produce hyaluronan during infection
Strict Conservation of the Retroviral Nucleocapsid Protein Zinc Finger Is Strongly Influenced by Its Role in Viral Infection Processes: Characterization of HIV-1 Particles Containing Mutant Nucleocapsid Zinc-Coordinating Sequences

AbstractThe retroviral nucleocapsid (NC) protein contains highly conserved amino acid sequences (-Cys-X2-Cys-X4-His-X4-Cys-) designated retroviral (CCHC) Zn2+fingers. The NC protein of murine leukemia viruses contains one NC Zn2+finger and mutants that were competent in metal binding (CCCC and CCHH) packaged wild-type levels of full-length viral RNA but were not infectious. These studies were extended to human immunodeficiency virus type 1 (HIV-1), a virus with two NC Zn2+fingers. Viruses with combinations of CCHC, CCCC, and CCHH Zn2+fingers in each position of HIV-1 NC were characterized. Mutant particles contained the normal complement of processed viral proteins. Four mutants packaged roughly wild-type levels of genomic RNA, whereas the remaining mutants packaged reduced levels. Virions with mutated C-terminal position NC fingers were replication competent. One interesting mutant, containing a CCCC Zn2+finger in the N-terminal position of NC, packaged wild-type levels of viral RNA and showed ∼5% wild-type levels of infectivity when examined in CD4-expressing HeLa cells containing an HIV-1 LTR/β-galactosidase construct. However, this particular mutant was replication defective in H9 cells; all other mutants were replication defective over the 8-week course of the assay. Two long terminal repeat viral DNA species could be detected in the CCCC mutant but not in any of the other replication-defective mutants. These studies show that the N-terminal Zn2+finger position is more sensitive to alterations than the C-terminal position with respect to replication. Additionally, the retroviral (CCHC) NC Zn2+finger is required for early infection processes. The evolutionary pressure to maintain CCHC NC Zn2+fingers depends mainly on its function in infection processes, in addition to its function in genome packaging
Enhancer-like Properties of an RNA Element That Modulates Tombusvirus RNA Accumulation

AbstractPrototypical defective interfering (DI) RNAs of the plus-strand RNA virus tomato bushy stunt virus contain four noncontiguous segments (regions I–IV) derived from the viral genome. Region I corresponds to 5′-noncoding sequence, regions II and III are derived from internal positions, and region IV represents a 3′-terminal segment. We analyzed the internally located region III in a prototypical DI RNA to understand better its role in DI RNA accumulation. Our results indicate that (1) region III is not essential for DI RNA accumulation, but molecules that lack it accumulate at significantly reduced levels (∼10-fold lower), (2) region III is able to function at different positions and in opposite orientations, (3) a single copy of region III is favored over multiple copies, (4) the stimulatory effect observed on DI RNA accumulation is not due to region III-mediated RNA stabilization, (5) DI RNAs lacking region III permit the efficient accumulation of head-to-tail dimers and are less effective at suppressing helper RNA accumulation, and (6) negative-strand accumulation is also significantly depressed for DI RNAs lacking region III. Collectively, these results support a role for region III as an enhancer-like element that facilitates DI RNA replication. A scanning-type mutagenesis strategy was used to define portions of region III important for its stimulatory effect on DI RNA accumulation. Interestingly, the results revealed several differences in the requirements for activity when region III was in the forward versus the reverse orientation. In the context of the viral genome, region III was found to be essential for biological activity. This latter finding defines a critical role for this element in the reproductive cycle of the virus
A GroEL Homologue from Endosymbiotic Bacteria of the WhiteflyBemisia tabaciIs Implicated in the Circulative Transmission of Tomato Yellow Leaf Curl Virus

AbstractEvidence for the involvement of aBemisia tabaciGroEL homologue in the transmission of tomato yellow leaf curl geminivirus (TYLCV) is presented. A ∼63-kDa protein was identified inB. tabaciwhole-body extracts using an antiserum raised against aphidBuchneraGroEL. The GroEL homologue was immunolocalized to a coccoid-shaped whitefly endosymbiont. The 30 N-terminal amino acids of the whitefly GroEL homologue showed 80% homology with that from different aphid species and GroEL fromEscherichia coli. Purified GroEL fromB. tabaciexhibited ultrastructural similarities to that of the endosymbiont from aphids andE. coli.In vitroligand assays showed that tomato yellow leaf curl virus (TYLCV) particles displayed a specific affinity for theB. tabaci63-kDa GroEL homologue. Feeding whiteflies anti-BuchneraGroEL antiserum before the acquisition of virions reduced TYLCV transmission to tomato test plants by >80%. In the haemolymph of these whiteflies, TYLCV DNA was reduced to amounts below the threshold of detection by Southern blot hybridization. Active antibodies were recovered from the insect haemolymph suggesting that by complexing the GoEL homologue, the antibody disturbed interaction with TYLCV, leading to degradation of the virus. We propose that GroEL ofB. tabaciprotects the virus from destruction during its passage through the haemolymph
Viral Burden and Disease Progression in Rhesus Monkeys Infected with Chimeric Simian–Human Immunodeficiency Viruses

AbstractTo determine the role of viral burden in simian–human immunodeficiency virus (SHIV)-induced disease, cellular provirus and plasma viral RNA levels were measured after inoculation of rhesus monkeys with four different SHIVs. These SHIVs included SHIV-HXBc2 and SHIV-89.6, constructed withenv, tat, rev,andvpuderived from either cell line-passaged or primary patient isolates of human immunodeficiency virus type 1; the viral quasispecies SHIV-89.6P derived afterin vivopassage of SHIV-89.6; and a molecular clone, SHIV-KB9, derived from SHIV-89.6P. SHIV-HXBc2 and SHIV-89.6 are nonpathogenic in rhesus monkeys; SHIV-89.6P and SHIV-KB9 cause rapid CD4+T cell depletion and an immunodeficiency syndrome. Relative SHIV provirus levels were highest during primary infection in monkeys infected with SHIV-89.6P, the virus that caused the most rapid and dramatic CD4+T cell depletion. However, by 10 weeks postinoculation, provirus levels were similar in monkeys infected with the pathogenic and nonpathogenic chimeric viruses. The virus infections that resulted in the highest peak and chronic viral RNA levels were the pathogenic viruses SHIV-89.6P and SHIV-KB9. SHIV-89.6P uniformly caused rapid and profound CD4+T cell depletion and immunodeficiency. Infection with the SHIV-KB9 resulted in very low CD4+T cell counts without seroconversion in some monkeys and a substantial but less profound CD4+T cell depletion and rapid seroconversion in others. Surprisingly, the level of plasma viremia did not differ between SHIV-KB9-infected animals exhibiting these contrasting outcomes, suggesting that host factors may play an important role in AIDS virus pathogenesis
Analysis of the Steps Involved in Dengue Virus Entry into Host Cells

AbstractThe initial steps of dengue viral entry have been divided into adsorption and penetration using acid glycine treatment to inactivate extracellular virus after attachment to baby hamster kidney (BHK) cells but prior to penetration. First, we showed that virus infection was accomplished within 2 h after adsorption. Second, the assay was used to examine the properties of dengue envelope E protein-specific monoclonal antibodies (MAbs), lectins, and heparin. We found that three MAbs, 17-2, 46-9, and 51-3, may neutralize dengue 2 virus (DEN-2) through inhibition of not only viral attachment but also of penetration. However, one MAb, 56-3.1, interfered specifically with attachment. Therefore, the functional domains of E protein involved in attachment and penetration may be different. Moreover, studies with lectins indicated that carbohydrates, especially α-mannose residues, present on the virion glycoproteins may contribute to binding and penetration of the virus into BHK and mosquito C6/36 cells. Finally, virus infectivity was inhibited by heparin through its blocking effects at both virus attachment and penetration. This suggests that cell surface heparan sulfate functions in both viral attachment and penetration of DEN-2 virus. In conclusion, our results further elucidated some aspects of the dengue virus entry process
Sites of Simian Foamy Virus Persistence in Naturally Infected African Green Monkeys: Latent Provirus Is Ubiquitous, Whereas Viral Replication Is Restricted to the Oral Mucosa

AbstractFoamy viruses (FV), retroviruses of the genus Spumavirus, are able to infect a wide variety of animal species and replicate in nearly all types of cultured cells. To identify the cells targeted by FV in the natural host and define the sites of viral replication, multiple organs of four African green monkeys naturally infected with simian FV type 3 were investigated for the presence of FV proviral DNA and viral transcripts. All organs contained significant amounts of FV proviral DNA. In addition to proviruses containing the complete transactivator genetaf,proviral genomes carrying a specific 295-bp deletion in thetafgene were detected in all monkeys. As in the case of human foamy virus the deletion leads to the formation of thebetgene that is regarded to be instrumental in the regulation of viral persistence. FV RNA was detected by RT-PCR andin situhybridization only in the oral mucosa of one monkey. No other samples contained detectable levels of viral transcripts. Histopathological changes were not observed in any of the tissue samples analyzed. Our results show that the natural history of FV is characterized by latent infection in all organs of the host and by minimal levels of harmless viral replication in the oral mucosa. The broad host cell rangein vivofurther encourages the development of FV-derived vectors for therapeutic gene delivery