Search results for "Animal"
showing 10 items of 22159 documents
Binding and internalization of human papillomavirus type 33 virus-like particles by eukaryotic cells
1995
Infection of cells by human papillomaviruses (HPVs) associated with malignant genital lesions has not been studied because of the lack of an in vitro system and the unavailability of virions. We have now used virus-like particles (VLPs) of HPV type 33 to analyze the initial events in the interaction of the HPV capsid with cell lines. Binding of VLPs to HeLa cells was observed in biochemical assays and by immunofluorescence. VLP binding was inhibited by antisera raised against VLPs but not by monoclonal antibodies recognizing either L1 or L2 epitopes accessible on VLPs. Under saturating conditions, approximately 2 x 10(4) VLPs were bound per cell, with a dissociation constant of about 100 pM…
Assembly and Translocation of Papillomavirus Capsid Proteins
2002
ABSTRACT The major and minor capsid proteins of polyomavirus are preassembled in the cytoplasm and translocated to the nucleus only as a VP1-VP2/VP3 complex. In this study, we describe independent nuclear translocation of the L1 major protein and the L2 minor capsid protein of human papillomavirus type 33 by several approaches. First, we observed that expression and nuclear translocation of L2 in natural lesions precede expression of L1. Second, using a cell culture system for coexpression, we found that accumulation of L2 in nuclear domain 10 (ND10) subnuclear structures precedes L1 by several hours. In contrast, complexes of L2 and mutants of L1 forced to assemble in the cytoplasm are tra…
Nuclear localization but not PML protein is required for incorporation of the papillomavirus minor capsid protein L2 into virus-like particles.
2004
ABSTRACT Recent reports suggest that nuclear domain(s) 10 (ND10) is the site of papillomavirus morphogenesis. The viral genome replicates in or close to ND10. In addition, the minor capsid protein, L2, accumulates in these subnuclear structures and recruits the major capsid protein, L1. We have now used cell lines deficient for promyelocytic leukemia (PML) protein, the main structural component of ND10, to study the role of this nuclear protein for L2 incorporation into virus-like particles (VLPs). L2 expressed in PML protein knockout (PML −/− ) cells accumulated in nuclear dots, which resemble L2 aggregates forming at ND10 in PML protein-containing cells. These L2 assemblies also attracted…
Generation and neutralization of pseudovirions of human papillomavirus type 33
1997
Since human papillomaviruses (HPV) cannot be propagated in cell culture, the generation of infectious virions in vitro is a highly desirable goal. Here we report that pseudovirions can be generated by the assembly of virus-like particles (VLPs) in COS-7 cells containing multiple copies of a marker plasmid. Using recombinant vaccinia viruses, we have obtained spherical VLPs of HPV type 33 (HPV-33) which fractionate into heavy and light VLPs in cesium chloride density gradients. VLPs in the heavy fraction (1.31 g/cm3) carry the plasmid in DNase-resistant form and are capable of transferring the genetic marker located on the plasmid to COS-7 cells in a DNase-resistant way (pseudoinfection). Th…
Translocation of the nuclear autoantigen La to the cell surface of herpes simplex virus type 1 infected cells.
1992
Recently we developed a procedure to translocalize one of the extractable nuclear antigens (ENAs), the La protein, to the cell surface of CV-1 cells. Here we report that herpes simplex virus type 1 infection can also induce a translocation of the autoantigen to the cell surface. On the cell surface we detected La protein assembled with large protrusions. Within these protrusions La protein colocalized with virus particles. These protrusions are known to be released from the cell after virus infections. Such complexes consisting of self and virus could provide helper determinants for an anti-self response, and therefore be important in generation of autoimmunity.
Baculovirus-mediated immediate-early gene expression and nuclear reorganization in human cells
2007
Baculovirus, Autographa californica multiple nucleopolyhedrovirus (AcMNPV), has the ability to transduce mammalian cell lines without replication. The general objective of this study was to detect the transcription and expression of viral immediate-early genes in human cells and to examine the interactions between viral components and subnuclear structures. Viral capsids were seen in large, discrete foci in nuclei of both dividing and non-dividing human cells. Concurrently, the transcription of viral immediate-early transregulator genes (ie-1, ie-2) and translation of IE-2 protein were detected. Quantitative microscopy imaging and analysis showed that virus transduction altered the size of …
The human autoantigen La/SS-B accelerates herpes simplex virus type 1 replication in transfected mouse 3T3 cells.
1998
SUMMARY Permanently transfected mouse cell lines which expressed different levels of the human autoantigen La/SS-B were infected with different strains of herpes simplex virus type 1, including the strains ANG, HSZP, 17syn+ and HFEM. During infection the localization of the human La protein was followed using an anti-La MoAb, which recognized only the human La protein but did not cross-react with either the endogenous mouse La protein or any viral encoded protein. After infection La protein was transported from the nucleus to the cytoplasm. The time course of translocation was dependent on the amount of human La protein expressed in the respective cell line. Moreover, acceleration of viral …
Papillomavirus assembly requires trimerization of the major capsid protein by disulfides between two highly conserved cysteines.
1998
ABSTRACT We have used viruslike particles (VLPs) of human papillomaviruses to study the structure and assembly of the viral capsid. We demonstrate that mutation of either of two highly conserved cysteines of the major capsid protein L1 to serine completely prevents the assembly of VLPs but not of capsomers, whereas mutation of all other cysteines leaves VLP assembly unaffected. These two cysteines form intercapsomeric disulfides yielding an L1 trimer. Trimerization comprises about half of the L1 molecules in VLPs but all L1 molecules in complete virions. We suggest that trimerization of L1 is indispensable for the stabilization of intercapsomeric contacts in papillomavirus capsids.
Rapid and sensitive detection of metapneumovirus in clinical specimens by indirect fluorescence assay using a monoclonal antibody.
2008
Human metapneumovirus, with two known genotypes named A and B, is associated with mild respiratory symptoms to severe LRTI in children, high-risk adults and the elderly. Rapid and reliable methods of hMPV detection in clinical samples are essential to implement appropriate care, to better understand the pathology of hMPV and to determine its epidemiology. Respiratory samples from 1,386 patients collected during 2 consecutive years were screened for hMPV using indirect immunofluorescence (IFA) assay with a monoclonal antibody. Forty-three patients tested positive for hMPV by the IFA method. In parallel, the samples were examined with RT-PCR on the F gene. Of these, 41 specimens were RT-PCR p…
In vitro studies on the activation of the hepatitis C virus NS3 proteinase by the NS4A cofactor.
1996
AbstractProteolytic processing of the nonstructural proteins of the hepatitis C virus (HCV) is mediated by two viral proteinases: the NS2-3 proteinase cleaving at the NS2/3 junction and the NS3 serine-type proteinase responsible for processing at the NS3/4A, NS4A/B, NS4B/5A, and NS5A/B sites. Activity of the NS3 proteinase is modulated by NS4A. In the absence of this cofactor processing at the NS3-dependent sites does not occur or, in the case of the NS5A/B junction, is poor but increased when NS4A is present. Although recent studies demonstrated that proteinase activation requires direct interaction between NS3 and NS4A, the mechanism by which NS4A exerts the activation function is not kno…