1,721,080 research outputs found
Trafficking to the plasma membrane of the seven-transmembrane protein encoded by human herpesvirus 6 U51 gene involves a cell-specific function present in T lymphocytes
No full textThe sequence of human herpesvirus 6 (HHV-6) U51 open reading frame predicts a
protein of 301 amino acid residues with seven transmembrane domains. To identify
and characterize U51, we derived antipeptide polyclonal antibodies and developed
a transient expression assay. We ascertained that U51 was synthesized in cord
blood mononuclear cells infected with either variant A- or variant B-HHV-6 and
was transported to the surface of productively infected cells. When synthesized
in transient expression systems, U51 intracellular trafficking was regulated in a
cell-type-dependent fashion. In human monolayer HEK-293 and 143tk- cells, U51
accumulated predominantly in the endoplasmic reticulum and failed to be
transported to the cell surface. In contrast, in T-lymphocytic cell lines J-Jhan,
Molt-3, and Jurkat, U51 was successfully transported to the plasma membrane. We
infer that transport of U51 to the cell surface requires a cell-specific function
present in activated T lymphocytes and T-cell lines
The ectodomain of a novel member of the immunoglobulin subfamily related to the poliovirus receptor has the attributes of a bona fide receptor for herpes simplex virus types 1 and 2 in human cells
No full textWe report on the functional cloning of a hitherto unknown member of the
immunoglobulin (Ig) superfamily selected for its ability to confer susceptibility
to herpes simplex virus (HSV) infection on a highly resistant cell line (J1.1-2
cells), derived by exposure of BHKtk- cells to a recombinant HSV-1 expressing
tumor necrosis factor alpha (TNF-alpha). The sequence of herpesvirus Ig-like
receptor (HIgR) predicts a transmembrane protein with an ectodomain consisting of
three cysteine-bracketed domains, one V-like and two C-like. HIgR shares its
ectodomain with and appears to be an alternative splice variant of the previously
described protein PRR-1 (poliovirus receptor-related protein). Both HIgR and
PRR-1 conferred on J1.1-2 cells susceptibility to HSV-1, HSV-2, and bovine
herpesvirus 1. The viral ligand of HIgR and PRR-1 is glycoprotein D, a
constituent of the virion envelope long known to mediate viral entry into cells
through interaction with cellular receptor molecules. Recently, PRR-1, renamed
HveC (herpesvirus entry mediator C), and the related PRR-2, renamed HveB, were
reported to mediate the entry of HSV-1, HSV-2, and bovine herpesvirus 1, and the
homologous poliovirus receptor was reported to mediate the entry of pseudorabies
virus (R. J. Geraghty, C. Krummenacher, G. H. Cohen, R. J. Eisenberg, and P. G.
Spear, Science 280:1618-1620, 1998; M. S. Warner, R. J. Geraghty, W. M. Martinez,
R. I. Montgomery, J. C. Whitbeck, R. Xu, R. J. Eisenberg, G. H. Cohen, and P. G.
Spear, Virology 246:179-189, 1998). Here we further show that HIgR or PRR-1
proteins detected by using a monoclonal antibody to PRR-1 are widely distributed
among human cell lines susceptible to HSV infection and commonly used for HSV
studies. The monoclonal antibody neutralized virion infectivity in cells
transfected with HIgR or PRR-1 cDNA, as well as in the human cell lines,
indicating a direct interaction of virions with the receptor molecule, and
preliminarily mapping this function to the ectodomain of HIgR and PRR-1. Northern
blot analysis showed that HIgR or PRR-1 mRNAs were expressed in human tissues,
with the highest expression being detected in nervous system samples. HIgR adds a
novel member to the cluster of Ig superfamily members able to mediate the entry
of alphaherpesviruses into cells. The wide distribution of HIgR or PRR-1 proteins
among human cell lines susceptible to HSV infection, coupled with the
neutralizing activity of the antibody in the same cells, provides direct
demonstration of the actual use of this cluster of molecules as HSV-1 and HSV-2
entry receptors in human cell lines. The high level of expression in samples from
nervous system makes the use of these proteins in human tissues very likely. This
cluster of molecules may therefore be considered to constitute bona fide
receptors for HSV-1 and HSV-2
Herpes simplex virus glycoprotein K, but not its syncytial allele, inhibits cell-cell fusion mediated by the four fusogenic glycoproteins, gD, gB, gH, and gL
No full textA Myc epitope was inserted at residue 283 of herpes simplex virus type 1 (HSV-1) glycoprotein K (gK), a position previously shown not to interfere with gK activity. The Myc-tagged gK localized predominantly to the endoplasmic reticulum, both in uninfected and in HSV-infected cells. gK, coexpressed with the four HSV fusogenic glycoproteins, gD, gB, gH, and gL, inhibited cell-cell fusion. The effect was partially dose dependent and was observed both in baby hamster kidney (BHK) and in Vero cells, indicating that the antifusion activity of gK may be cell line independent. The antifusion activity of gK did not require viral proteins other than the four fusogenic glycoproteins. A syncytial (syn) allele of gK (syn-gK) carrying the A40V substitution present in HSV-1(MP) did not block fusion to the extent seen with the wild-type (wt) gK, indicating that the syn mutation ablated, at least in part, the antifusogenic activity of wt gK. We conclude that gK is part of the mechanism whereby HSV negatively regulates its own fusion activity. Its effect accounts for the notion that cells infected with wt HSV do not fuse with adjacent, uninfected cells into multinucleated giant cells or syncytia. gK may also function to preclude fusion between virion envelope and the virion-encasing vesicles during virus transport to the extracellular compartment, thus preventing nucleocapsid de-envelopment in the cytoplasm
Human Herpesvirus 6: An Emerging Pathogen
No full textInfections with human herpesvirus 6 (HHV-6), a ß-herpesvirus of which two variant groups (A and B) are recognized, is very common, approaching 100% in seroprevalence. Primary infection with HHV-6B causes roseola infantum or exanthem subitum, a common childhood disease that resolves spontaneously. After primary infection, the virus replicates in the salivary glands and is shed in saliva, the recognized route of transmission for variant B strains; it remains latent in lymphocytes and monocytes and persists at low levels in cells and tissues. Not usually associated with disease in the immunocompetent, HHV-6 infection is a major cause of opportunistic viral infections in the immunosuppressed, typically AIDS patients and transplant recipients, in whom HHV-6 infection/reactivation may culminate in rejection of transplanted organs and death. Other opportunistic viruses, human cytomegalovirus and HHV-7, also infect or reactivate in persons at risk. Another disease whose pathogenesis may be correlated with HHV-6 is multiple sclerosis. Data in favor of and against the correlation are discussed
The biology and natural history of two emerging pathogens: Human herpesviruses 6 and 7
No full textHuman herpesvirus 6, the causative agent of exanthem subitum, is emerging as an opportunistic pathogen in the growing population of immunosuppressed individuals, mainly affecting transplant recipients and AIDS patients. Human herpesvirus 6 has been associated with acute episodes of relapsing-remitting multiple sclerosis, with controversial reports from different research groups. Human herpesvirus 7, which is occasionally the causative agent of exanthem subitum, or fever without rash, appears to be of lower pathogenicity, but is also emerging as a possible agent of opportunistic infections. The genomes of both viruses are now fully sequenced and show an overlapping organization. The sequences will provide a basis for our understanding, at the molecular level, of the behaviour of the viruses in humans, and for the development of recombinant diagnostic reagents
Inibizione della replicazione del virus SV40 in cellule bsc-1 ad opera di un inibitore endogeno della proliferazione delle cellule renali (calone renale)
No full textConservation of the architecture of the Golgi apparatus related to a differential organization of microtubules in polykaryocytes induced by syn- mutants of herpes simplex virus 1
No full textInfection of Vero and HEp-2 but not of 143TK- cells with herpes simplex virus 1 results in fragmentation and dispersal of the Golgi apparatus. Concurrently, in all three infected cell lines the microtubular network is disrupted, suggesting that the disruption of microtubules is essential but not sufficient to induce the fragmentation of the Golgi apparatus. We now report the following: (i) In polykaryocytes formed in Vero cells infected with HSV-1 syn- mutant viruses, intact Golgi stacks were readily detected by electron microscopy. These aggregated in the center of large polykaryocytes. (ii) The distribution of viral glycoprotein D, examined in both fixed and nonfixed cells, appeared to match the distribution of the Golgi stacks, suggesting that the aggregated Golgi stacks funnel vital glycoproteins and viral particles to a limited region of the plasma membrane of the polykaryocytes rather than directing exocytic flow in a more dispersed fashion as seen in syn+ virus-infected cells exhibiting fragmented and dispersed Golgi. (iii) In most polykaryocytes, the microtubules formed parallel bundles extending along the axis of recruitment of new cells. (iv) Fragmentation of the microtubules at the periphery of the cell near the plasma membrane was observed in untreated or cycloheximide-treated cells 2 h after infection with syn- virus HSV-1(MP) or syn+ HSV-1 (mP) but not in mock-infected cells. These observations suggest that peripheral depolymerization is initiated at the time of infection and that a factor which determines the syn- or syn+ phenotype is whether the microtubular network regenerates concomitant with cell fusion or reorganizes to form a collapsed network surrounding nuclei of syn+ infected cells
The novel receptors that mediate the entry of herpes simplex viruses and animal alphaherpesviruses into cells
No full textAn extended array of cell surface molecules serve as receptors for HSV entry into cells. In addition to the heparan sulphate glycosaminoglycans, which mediate the attachment of virion to cells, HSV requires an entry receptor. The repertoire of entry receptors into human cells includes molecules from three structurally unrelated molecular families. They are (i) HveA (herpesvirus entry mediator A), (ii) members of the nectin family, (iii) 3-O-sulphated heparan sulphate. The molecules have different attributes and play potentially different roles in HSV infection and spread to human tissues. All the human entry receptors interact physically with the virion envelope glycoprotein D (gD). (i) HveA is a member of the TNF-receptor family. It mediates entry of a restricted range of HSV strains. Its expression is restricted to few lineages (e.g. T-lymphocytes). (ii) The human nectin1α (HIgR), nectin1δ (PRR1-HveC), and the nectin2α (PRR2α-HveB) and nectin2δ (PRR2δ) belong to the immunoglobulin superfamily. They are homologues of the poliovirus receptor (CD155), with which they share the overall structure of the ectodomain. The human nectin1α-δ are broadly expressed in cell lines of different lineages, are expressed in human tissue targets of HSV infection, serve as receptors for all HSV-1 and HSV-2 strains tested and mediate entry not only of free virions, but also cell-to-cell spread of virus. (iii) The 3-O-sulphated heparan sulphate is expressed in some selected human cell lines (e.g. endothelial and mast cells) and human tissues, and mediates entry of HSV-1, but not HSV-2. The human nectin2α and nectin2δ serve as receptors for a narrow range of viruses. A characteristic of the human nectin1α-δ is the promiscuous species non-specific receptor activity towards the animal alphaherpesviruses, pseudorabies virus (PrV) and bovine herpesvirus 1 (BHV-1). By contrast with the human nectin1δ, its murine homologue (mNectin1δ) does not bind gD at detectable level, yet it mediates entry of HSV, as well as of PrV and BHV-1. This provides the first example of a mediator of HSV entry independent of a detectable interaction with gD. Copyright (C) 2000 John Wiley and Sons, Ltd
Mapping of herpes simplex virus 1 genes with mutations which overcome host restrictions to infection
No full textEarlier studies have shown that the thymidine kinase-negative baby hamster kidney (BHKTK-) cell lines expressing constitutively the herpes simplex virus 1 (HSV-1) glycoprotein D (gD), designated BJ, restrict infection by HSV-1 at the level of virus entry. U10, a HSV-1 mutant not restricted by the BJ cells, carried the substitution of proline for Leu25 in the gD gene, suggesting that gD encodes a specialized domain which precludes virus entry into cells expressing gD. Analyses of a new series of 36 unrestricted viral mutants showed the following. (i) Only two mutants contained mutations at a site which did not overlap with the previously reported mutation. A representative of a previously mapped mutant and one of the two new mutants were examined in detail. Thus, in the gD of mutant U30 Ala185 was replaced by threonine, whereas in gD of U21, Ala185 and Leu25 were replaced with threonine and proline, respectively. U30 and U21 multiplied better than the wild-type parent virus in the parental BHKTK- cells. (ii) Transfer of the gD gene from U21 or U30 to wild-type parent virus or to the gD- virus FgDβ yielded recombinants which, while capable of infecting BJ cells, were considerably less efficient than the parent unrestricted mutants, suggesting that the latter contained additional mutations which were responsible in part for the unrestricted phenotype. Conversely, marker rescue of mutant viruses with wild-type gD reduced but did not abrogate entirely the unrestricted phenotype. (iii) Mutations in gD which conferred the unrestricted phenotype were not random. (iv) gD plays a role in the restriction, inasmuch as preincubation of cells expressing gD with antibodies to gD abolished restriction. (v) In mutant R5000, the gD substitution Ser140 to Asn was capable of overcoming a restriction of a BHKTK- clonal line which does not express gD but conferred very low ability to replicate on BJ cells. We conclude that (a) uncloned stocks of BHKTK- cells exhibit a low level restriction to infection with wild-type virus, (b) clonal lines of BHKTK- cells which vary with respect to the stringency of restriction express either allelic genes differing in the properties of their products or products of different genes, and (c) both the restricted and unrestricted phenotypes reflect the interactions of gD with these cellular products. The implications of these conclusions with respect to the restriction imposed on BHK cells by the expression of gD are discussed
Characterization of a herpes simplex virus type 1 mutant resistant to benzhydrazone, a selective inhibitor of herpesvirus glycosylation
No full textBenzhydrazone [BH; 1H-benz[f]indene-1,3(2H)-dionebis(amidinohydrazone)] significantly inhibits glycosylation of proteins, but only in cells infected with herpes simplex virus. We report on a herpes simplex virus type 1 (HSV-1) mutant resistant to BH. A syncytium-inducing mutant designated HSV-1(13)S11 was found to be biochemically resistant to BH in that [14C]glucosamine incorporation was not inhibited in infected HEp-2 cells exposed to the drug. Intertypic recombinants were obtained which showed that BH resistance is encoded in the DNA of the mutant virus and may be transferred into the genome of BH-sensitive HSV. In the recombinants the biochemical resistance marker segregated from the syncytial marker, suggesting that the two markers probably map in different loci. The BH-resistant mutant did not complement wild-type BH-sensitive HSV-1 and -2. Furthermore, resistance was apparent in HEp-2 but not in Vero cells. The paper discusses the hypothesis that inhibition of glycosylation of HSV proteins is the consequence of modification or selective transport of BH involving a HSV gene product
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