pinecone/core-2020-05-10-deduplication huggingface dataset:
Iduronic Acid-Containing Glycosaminoglycans on Target Cells Are Required for Efficient Respiratory Syncytial Virus Infection

AbstractRespiratory syncytial virus (RSV) is an important human respiratory pathogen, particularly in infants. Glycosaminoglycans (GAGs) have been implicated in the initiation of RSV infection of cultured cells, but it is not clear what type of GAGs and GAG components are involved, whether the important GAGs are on the virus or the cell, or what the magnitude is of their contribution to infection. We constructed and rescued a recombinant green fluorescent protein (GFP)-expressing RSV (rgRSV) and used this virus to develop a sensitive system to assess and quantify infection by flow cytometry. Evaluation of a panel of mutant Chinese hamster ovary cell lines that are genetically deficient in various aspects of GAG synthesis showed that infection was reduced up to 80% depending on the type of GAG deficiency. Enzymatic removal of heparan sulfate and/or chondroitin sulfate from the surface of HEp-2 cells also reduced infection, and the removal of both reduced infection even further. Blocking experiments in which RSV was preincubated with various soluble GAGs revealed the relative blocking order of: heparin > heparan sulfate > chondroitin sulfate B. Iduronic acid is a component common to these GAGs. GAGs that do not contain iduronic acid, namely, chondroitin sulfate A and C and hyaluronic acid, did not inhibit infection. A role for iduronic acid-containing GAGs in RSV infection was confirmed by the ability of basic fibroblast growth factor to block infection, because basic fibroblast growth factor binds to GAGs containing iduronic acid. Pretreatment of cells with protamine sulfate, which binds and blocks GAGs, also reduced infection. In these examples, infection was reduced by pretreatment of the virus with soluble GAGs, pretreatment of the cells with GAG-binding molecules, pretreatment of the cells with GAG-destroying enzymes or in cells genetically deficient in GAGs. These results establish that the GAGs involved in RSV infection are present on the cell rather than on the virus particle. Thus, the presence of cell surface GAGs containing iduronic acid, like heparan sulfate and chondroitin sulfate B, is required for efficient RSV infection in cell culture
Membrane Fusion between Retroviral Particles: Host-Range Extension and Vaccine Prospects

AbstractWe have analyzed if different populations of retroviral particles carrying the viral and cellular receptors of membrane viruses, respectively, are able to specifically fuse with each other. Using the glycoprotein of human immunodeficiency virus type 1 and its cellular receptor complex, we demonstrate that interviral membrane fusion can, indeed, occur and that the resultant fused viral structures are able to infect cells and transduce a marker gene. On the one hand, these results have relevance for the development of vaccine strategies based on fusion-induced conformational epitopes on the viral glycoprotein. However, in addition to this potential practical application, the results obtained (which were extended to include analyses with the vesicular stomatitis virus G protein and its cellular receptor) have far-reaching implications for in vivo situations in which simultaneous infections with different membrane viruses can occur
Hepatitis C Virus Core Protein Promotes Immortalization of Primary Human Hepatocytes

AbstractHepatitis C virus (HCV) core protein has many intriguing properties as a viral factor and is implicated in cell growth regulation. In this study, the cell growth regulation potential of HCV core protein was investigated by introduction of the core genomic region into primary human hepatocytes, a natural host for virus replication and tropism. Core-transfected primary human hepatocytes displayed altered cell morphology resembling that of low-differentiated epithelial cells. Those cells retained an immortalized phenotype and exhibited continuous growth after more than 50 passages over 2 years. Stable hepatocyte transfectants exhibited albumin secretion and HCV core protein expression. Telomerase activity, a characteristic of immortalized or transformed cells, was evident in the transfected hepatocytes immediately after senescence. Anchorage-independent growth of the immortalized hepatocytes provided further evidence for a transformed phenotype. Results from these studies suggest that the HCV core protein promotes primary human hepatocytes to an immortalized phenotype, which may predispose cells over an extended period of time to undergo a transforming event. Thus, HCV core protein appears to contribute to virus-mediated pathogenesis in a persistently infected host
Absence of Coreceptor Switch with Disease Progression in Human Immunodeficiency Virus Infections in India

AbstractThe envelope glycoprotein of the human immunodeficiency virus (HIV) utilizes CD4 as a receptor and CCR5 and/or CXCR4 as coreceptor to gain entry into the cell. The CCR5-tropic viruses, observed early in infection, could be important in transmission and the CXCR4-tropic viruses, observed late, may play an important role in disease progression. Viruses from 40 HIV-positive, asymptomatic or symptomatic individuals in India were isolated. Of 40 isolates 39 used CCR5. Thirty-three isolates were subtype C, 3 isolates were subtype A, and 4 isolates were HIV-2. Only 1 HIV-2 isolate, from a symptomatic individual, was dualtropic. Therefore, a majority of isolates from India belonged to subtype C and all the isolates utilized CCR5 exclusively irrespective of HIV disease status
Immune Protection against HSV-2 in B-Cell-Deficient Mice

AbstractThe role of antibody in protection of the vaginal mucosa and sensory ganglia against HSV-2 infection was examined using HSV- immune, B-cell-deficient μMT mice. Significantly higher virus titers were detected in the vaginal mucosae of immune μMT mice compared to immune C57BL/6J mice 24 h after HSV-2 rechallenge. However, virus was rapidly cleared in immune μMT mice, and the infection was resolved with only a 2-day delay. Passive transfer of immune serum to immune μMT mice prior to rechallenge resulted in HSV-specific vaginal IgG levels comparable to those of immune C57BL/6J mice. Although transferred antibody failed to prevent reinfection of the majority of recipients, vaginal virus titers at 24 h and clearance kinetics were similar to those of immune C57BL/6J controls. Following vaginal rechallenge, HSV-2 did not spread to the sensory ganglia of immune C57BL/6J mice nor was the rechallenge virus detected in the ganglia of the majority of immune μMT mice. However, protection was severely compromised by T-cell depletion of immune C57BL/6J mice. These results suggest that HSV-specific antibody limits, but does not prevent, infection of the genital epithelia. Further, prevention of virus spread to the sensory ganglia in immune animals requires vigorous T-cell immune responses
Characterization of HIV-1-Specific Cytotoxic T Lymphocytes Expressing the Mucosal Lymphocyte Integrin CD103 in Rectal and Duodenal Lymphoid Tissue of HIV-1-Infected Subjects

AbstractAcute HIV-1 infection depletes CD4+ T cells in gut-associated lymphoid tissue (GALT). The failure of containment of local viral replication, and consequent CD4+ T cell depletion, might be due to delayed mobilization of effector CD8+ T cells or absence of functioning HIV-1-specific CD8+ T cell effectors within GALT. No studies have addressed human intestinal HIV-1-specific CD8+ T cell functions. We sought to determine whether functional HIV-1-specific CTL were present in GALT and whether the repertoire differed from HIV-1-specific CTL isolated from peripheral blood mononuclear cells. From three HIV-1-infected subjects, we isolated HIV-1-specific CD8+ T cells expressing the mucosal lymphocyte integrin CD103 from GALT. These antigen-specific effector cells could be expanded in vitro and lysed target cells in an MHC class I-restricted manner. HIV-1-specific CTL could be isolated from both duodenal and rectal GALT sites, indicating that CD8+ effectors were widespread through GALT tissue. The breadth and antigenic specificities of GALT CTL appeared to differ from those in peripheral blood in some cases. In summary, we found HIV-1-specific CD8+ effector T cells in GALT, despite HIV-1-induced CD4+ T cell lymphopenia. This suggests that HIV-1-specific CTL in gut tissue can be maintained with limited CD4+ T cell help
Phytoreovirus T = 1 Core Plays Critical Roles in Organizing the Outer Capsid of T = 13 Quasi-equivalence

AbstractThe structures of the double-shelled rice dwarf virus and of its single-shell core have been determined by cryoelectron microscopy and image reconstruction. The core carries a prominent density located at each of the icosahedral faces of its T = 1 lattice. These protrusions are formed by outer shell trimers, tightly inserted at the threefold positions of the core. Such configuration of the core may guide the assembly of the outer shell, aided by lateral interactions between its subunits, into a T = 13 lattice. The organization of the phytoreovirus capsid elucidates for the first time a general model for assembling two unique T numbers of quasi-equivalence
Identification and Molecular Characterization of the Choristoneura fumiferana Multicapsid Nucleopolyhedrovirus Genomic Region Encoding the Regulatory Genes pkip, p47, lef-12, and gta

AbstractChoristoneura fumiferana multicapsid nucleopolyhedrovirus (CfMNPV) is a baculovirus pathogenic to spruce budworm, the most damaging insect pest in Canadian forestry. CfMNPV is less virulent to its host insect and its replication cycle is slower than the baculovirus type species Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) but the basis of these characteristics is not known. We have now identified, localized, and determined the sequence of the region of CfMNPV carrying potentially important regulatory genes including p47, lef-12, gta, and pkip. DNA database searches revealed that this region of CfMNPV is most closely related to the homologous OpMNPV genes. Transcription analysis demonstrated that CfMNPV P47 is encoded by a 1.6-kb transcript, LEF-12 is encoded by a 2.6-kb transcript, and GTA is encoded by a 2.1-kb transcript. Transcripts for these genes were detectable at 6 h postinfection but all of them showed a burst in expression levels between 12 and 24 h postinfection corresponding to the time of initiation of CfMNPV DNA replication. A polyclonal antibody, raised against CfMNPV P47, detected a nuclear 43-kDa polypeptide from 12 to 72 h postinfection, demonstrating that the CfMNPV p47 gene product is first expressed at a time corresponding to the burst of transcriptional activity between the early and the late phases. Both AcMNPV and CfMNPV P47 translocate to the nucleus of infected cells
Specific Interaction between the Hepatitis Delta Virus RNA and Glyceraldehyde 3-Phosphate Dehydrogenase: An Enhancement on Ribozyme Catalysis

AbstractReplication of hepatitis delta virus (HDV) RNA occurs in the nuclei of infected cells. The replication is mediated by cellular factors containing an RNA polymerase II-like enzyme activity through a double rolling-circle mechanism and is regulated by delta antigens. In this study, UV cross-linking experiments were carried out to examine interactions between HDV RNA and proteins present in HeLa nuclear extract. Cellular proteins with molecular mass of 23 (p23), 36 (p36), 38 (p38), and 58 (p58) kDa bound to full-length HDV RNA of both genomic and antigenomic strands. Deletion analysis on the antigenomic strand mapped the interacting domain within a 79-nucleotide fragment but not at the ends of the rod-shaped viral RNA structure. The specificity of the RNA-protein interactions was demonstrated by competition experiments and the specific HDV RNA-binding proteins were purified through column chromatography. Electrophoresis mobility shift assay with the purified fractions demonstrated that the interaction between p36 and HDV RNA was relatively stable even in the presence of 0.5 M NaCl. Biochemical analysis including protein microsequencing identified the p36 as glyceraldehyde 3-phosphate dehydrogenase (GAPDH). RNase footprinting indicated that the UC-rich domain between nucleotides 379 and 414 of the HDV antigenomic RNA was involved in the GAPDH binding. Functional studies further demonstrated an enhancing effect of GAPDH on the ribozyme activity of HDV antigenomic RNA. In addition, in the presence of HDV RNA cellular GAPDH relocalized from the cytoplasm to the nucleus where HDV replication occurs. These results suggest that GAPDH is involved in the replication of HDV
Decreased Vaginal Disease in J-Chain-Deficient Mice Following Herpes Simplex Type 2 Genital Infection

AbstractJ-chain-deficient (Jch−/−) mice were used to study the role of polymeric IgA (pIgA) in primary disease and protective immunity following genital herpes simplex type 2 (HSV-2) infection. Vaginal IgA in the Jch−/− mice was composed primarily of monomeric IgA and was not associated with secretory component (SC). In contrast, vaginal IgA in wild-type (WT) mice was predominantly polymeric and bound to SC. Following HSV-2 genital infection, the Jch−/− mice consistently exhibited fewer vaginal symptoms (P = 0.010) and mortality (P = 0.075) than did the WT mice. The variation in disease expression could not be explained by differences in local viral replication, since titers in vaginal wash fluid were comparable. To assess the effect of J chain deficiency on protective immunity, WT and Jch−/− mice were immunized intravaginally with attenuated HSV-2, challenged intravaginally with wild-type virus 5 weeks later, and evaluated for vaginal infection and neurological disease. Although the Jch−/− mice had reduced vaginal HSV-specific IgA and IgG levels following immunization, both WT and Jch−/− mice were protected from symptoms following wild-type virus challenge. We conclude that pIgA is not required for protective immunity against genital HSV-2 disease and that J chain deficiency offers some protection against symptoms following primary HSV-2 genital infection
Varicella-Zoster Virus Infection of a Human CD4-Positive T-Cell Line

AbstractVaricella-zoster virus (VZV) is a human α-herpesvirus that causes varicella (chickenpox) at primary infection and may reactivate as herpes zoster. VZV is a T-lymphotropic virus in vivo. To investigate the T-cell tropism of VZV, we constructed a recombinant virus expressing green fluorescent protein (VZV-GFP) under the CMV IE promoter. Coculture of VZV-GFP-infected fibroblasts with II-23 cells, a CD4-positive human T-cell hybridoma, resulted in transfer of virus to II-23 cells. II-23 cells are susceptible to VZV-GFP infection as demonstrated by expression of immediate/early (IE62), early (ORF4), and late (gE) genes. Recovery of infectious virus was limited, with only 1 to 3 in 106 cells releasing infectious virus by plaque assay, indicating that transfer of virus results in a limited productive infection. In vitro infection of II-23 cells will be useful for further analysis of VZV tropism for T-lymphocytes
Identification and Phylogenetic Comparison of Salem Virus, a Novel Paramyxovirus of Horses

AbstractA virus that could not be identified as a previously known equine virus was isolated from the mononuclear cells of a horse. Electron microscopy revealed enveloped virions with nucleocapsid structures characteristic of viruses in the Paramyxoviridae family. The virus failed to hemadsorb chicken or guinea pig red blood cells and lacked neuraminidase activity. Two viral genes were isolated from a cDNA expression library. Multiple sequence alignments of one gene indicated an average identity of 45% as compared to Morbillivirus N protein sequences. A weaker relationship was found with Tupaia paramyxovirus (TPMV) and Hendra virus (HeV) N proteins. In the second gene, multiple open reading frames (ORFs) were identified, corresponding to the arrangement of the P, V, and C ORFs in the Morbillivirus and Respirovirus viruses. Short stretches in the C-terminal regions of the P and C proteins showed limited homologies to viruses in the Morbillivirus genus but no obvious relationship to viruses in other genera. The V ORF translation product contained a highly conserved, cysteine-rich domain that is common to most viruses in the Paramyxovirinae subfamily. Sequencing of P gene cDNA clones confirmed the use of a cotranscriptional editing mechanism for the regulation of P/V expression. Based on the location of its origin it has been named Salem virus (SalV)
Efficient Complementation by Chimeric Microviridae Internal Scaffolding Proteins Is a Function of the COOH-Terminus of the Encoded Protein

AbstractMicroviridae morphogenesis is dependent on two scaffolding proteins, an internal and external species. Both structural and genetic analyses suggest that the COOH-terminus of the internal protein is critical for coat protein recognition and specificity. To test this hypothesis, chimeric internal scaffolding genes between Microviridae members φX174, G4, and α3 were constructed and the proteins expressed in vivo. All of the chimeric proteins were functional in complementation assays. However, the efficient complementation was observed only when the viral coat protein and COOH-terminus of internal scaffolding were of the same origin. Genes with 5′ deletions of the φX174 internal scaffolding gene were also constructed and expressed in vivo. Proteins lacking the first 10 amino acids, which self-associate across the twofold axes of symmetry in the atomic structure, efficiently complement φX174 am(B) mutants at temperatures above 24°C. These results suggest that internal scaffolding protein self-associations across the twofold axes of symmetry are required only at lower temperatures
Entry of R5X4 and X4 Human Immunodeficiency Virus Type 1 Strains Is Mediated by Negatively Charged and Tyrosine Residues in the Amino-Terminal Domain and the Second Extracellular Loop of CXCR4

AbstractCXCR4 mediates the fusion and entry of X4 and R5X4 strains of human immunodeficiency virus type 1 (HIV-1). The residues involved in CXCR4 coreceptor function have not all yet been identified, but tyrosine and negatively charged residues in the amino-terminal domain of CCR5 were shown to be indispensable for gp120 binding and entry of R5 and R5X4 strains. We therefore evaluated the role of such residues in CXCR4 coreceptor function by replacing tyrosines (Y), aspartic acids (D), and glutamic acids (E) with alanines (A) and testing the ability of these mutants to mediate the entry of X4 and R5X4 HIV-1 isolates. Our results show that viral entry depends on YDE-rich clusters in both the amino-terminus and the second extracellular loop of CXCR4. Different viral isolates vary in their dependence on residues in one or the other domain. The determinants of CXCR4 coreceptor function are, therefore, more diffuse and isolate-dependent than those of CCR5
Characterization of a Membrane-Associated Protein Implicated in Visna Virus Binding and Infection

AbstractThe identity of the cellular receptor(s) for visna virus, an ovine lentivirus, is currently unknown; however, previous studies from our laboratory have identified membrane-associated proteins expressed selectively in susceptible cells which bind visna virus. Moreover, a polyclonal antibody (2-23), raised against a 45-kDa visna virus binding protein, bound specifically to the surface of susceptible cells in immunofluorescence assays and significantly reduced binding of visna virus to cells (S. E. Crane et al., 1991, J. Virol., 65, 6137–6143). In this report we extend our studies of this antibody (2-23), showing both that 2-23 significantly reduces visna virus infection of susceptible cells and that 2-23 immunoprecipitates a putative protein complex consisting of a prominent 30-kDa protein, as well as the 45-kDa immunogen, specifically from radiolabeled virus-susceptible sheep cells. Further, we demonstrate that the 30-kDa protein is a membrane-associated proteoglycan substituted with a chondroitin sulfate glycosaminoglycan (GAG) chain(s) and that treatment of susceptible cells with an inhibitor of GAG synthesis significantly reduces visna virus production. Collectively, these data support a role for a proteoglycan in visna virus cell binding and infection
HIV-1 Replication Is Inhibited by a Pseudo-substrate Peptide That Blocks Tat Transactivation

AbstractThe activation of the HIV-1 long terminal repeat (LTR) by the viral transcriptional transactivator Tat is an essential step in the viral replication cycle. To increase the processivity of RNA polymerase II, Tat interacts with the positive transcription elongation factor b (P-TEFb) and cyclin-dependent kinase (CDK)-activating kinase (CAK). In this study, we demonstrate that a pseudo-substrate peptide for CDK7, mC2p, inhibits HIV-1 replication as well as Tat transactivation. Specifically, mC2p blocks only the activity of CAK and not that of P-TEFb. Moreover, mC2p inhibits Tat transactivation and HIV replication. Therefore, the activation of CDK7 by Tat is considered a critical step of Tat transactivation and mC2p and related compounds represent potential candidates for novel anti-HIV therapeutics
Molecular Studies on Bromovirus Capsid Protein VI. Contributions of the N-Terminal Arginine-Rich Motif of BMV Capsid Protein to Virion Stability and RNA Packaging

AbstractSpecific interactions are likely to occur between the highly conserved N-proximal arginine-rich motif (ARM) of Brome mosaic virus (BMV) coat protein (CP) and each of three genomic RNAs and a single subgenomic RNA during in vivo encapsidation. To characterize these interactions, three independent deletions were engineered into a biologically active clone of BMV RNA3 (B3) such that the matured CP of each B3 variant precisely lacks either the entire ARM (B3/Δ919) or two consecutive arginine residues (B3/13ΔΔ14 and B3/18ΔΔ19) within the ARM. Analysis of virion RNA for each B3 variant recovered from symptomatic leaves of Chenopodium quinoa revealed that the interactions between the N-terminal ARM of BMV CP and each of three genomic RNAs is distinct. Northern blot hybridization of B3Δ919 virion RNA revealed that the deleted ARM region specifically affected the stability of virions containing RNA1. An abundant truncated RNA species recurrently found in the virions of B3Δ919 was identified to be a derivative of genomic RNA1, lacking the 5′ 943 nucleotides. Additional Northern blot analysis of virion RNAs from B3/Δ919, B3/13ΔΔ14, and B3/18ΔΔ19, and in vitro reassembly assays revealed that the N-terminal ARM region contains crucial amino acids required for RNA4 packaging, independent of genomic RNA3. The significance of these observations in relation to Bromovirus CP-RNA interactions during virion assembly is discussed
Functions of the 126- and 183-kDa Proteins of Tobacco Mosaic Virus

AbstractTobacco mosaic virus produces two proteins that contain domains similar to the methyltransferase (MT) and helicase (HEL)-like domains of the replicase-associated proteins of other RNA viruses. The more abundant 126-kDa protein contains only the MT and HEL-like domains, whereas the 183-kDa readthrough protein additionally contains the polymerase domain. We examined the functions of these proteins by constructing a bipartite system to express the 126- and 183-kDa proteins from separate RNAs. Mutants expressing the 183-kDa protein recognized promoters for negative- and positive-stranded RNA synthesis, transcribed subgenomic mRNAs, capped RNAs, synthesized proteins, moved cell to cell within the plant, and replicated defective RNAs (dRNAs). The principal function of the 126-kDa protein was to increase the rate of replication approximately tenfold. The 126-kDa protein appeared to function primarily in cis, and production of the 126-kDa protein in trans did not enhance replication of the helper virus. dRNAs producing a functional 126-kDa protein were replicated efficiently by helper viruses that produced only the 183-kDa protein but not by wild-type virus, suggesting that efficient replication required the 183-kDa protein to form a heterodimer with the 126-kDa protein already bound to the target dRNA