bluuebunny/crossref_metadata_2025_split huggingface dataset:
P74 Mediates Specific Binding of
Autographa californica
M Nucleopolyhedrovirus Occlusion-Derived Virus to Primary Cellular Targets in the Midgut Epithelia of
Heliothis virescens
Larvae
Authors: Haas-Stapleton Eric J. , Washburn Jan O. , Volkman Loy E. 
Published: June 2004

ABSTRACT

P74, an envelope protein of the occlusion-derived virus (ODV) of
Autographa californica
M nucleopolyhedrovirus (AcMNPV), is critical for oral infection of
Trichoplusia ni
larvae. The role of P74 during primary infection, however, is unknown. Here we provide evidence that P74 facilitates binding of AcMNPV ODV to a specific receptor within the larval midgut epithelia of another host species,
Heliothis virescens
. We adapted a fluorescence dequenching assay to compare binding, fusion, and competition of wild-type AcMNPV ODV in vivo with itself and with the ODV of a
p74
-deficient AcMNPV mutant. We found that relative to wild-type ODV, binding and fusion of ODV deficient in P74 were both qualitatively and quantitatively different. Unlike wild-type ODV, an excess of P74-deficient ODV failed to compete effectively with wild-type ODV binding, and the overall binding level of the mutant ODV was one-third that of the wild type. These results implicated P74 as an ODV attachment protein that binds to a specific receptor on primary target cells within the midgut.
Prion Infection of Skeletal Muscle Cells and Papillae in the Tongue
Authors: Mulcahy Ellyn R. , Bartz Jason C. , Kincaid Anthony E. , Bessen Richard A. 
Published: June 2004

ABSTRACT

The presence of the prion agent in skeletal muscle is thought to be due to the infection of nerve fibers located within the muscle. We report here that the pathological isoform of the prion protein, PrP
Sc
, accumulates within skeletal muscle cells, in addition to axons, in the tongue of hamsters following intralingual and intracerebral inoculation of the HY strain of the transmissible mink encephalopathy agent. Localization of PrP
Sc
to the neuromuscular junction suggests that this synapse is a site for prion agent spread between motor axon terminals and muscle cells. Following intracerebral inoculation, the majority of PrP
Sc
in the tongue was found in the lamina propria, where it was associated with sensory nerve fibers in the core of the lingual papillae. PrP
Sc
staining was also identified in the stratified squamous epithelium of the lingual mucosa. These findings indicate that prion infection of skeletal muscle cells and the epithelial layer in the tongue can be established following the spread of the prion agent from nerve terminals and/or axons that innervate the tongue. Our data suggest that ingestion of meat products containing prion-infected tongue could result in human exposure to the prion agent, while sloughing of prion-infected epithelial cells at the mucosal surface of the tongue could be a mechanism for prion agent shedding and subsequent prion transmission in animals.
Human Immunodeficiency Virus Type 1 Tat Increases the Expression of Cleavage and Polyadenylation Specificity Factor 73-Kilodalton Subunit Modulating Cellular and Viral Expression
Authors: Calzado Marco A. , Sancho Rocío , Muñoz Eduardo 
Published: June 2004

ABSTRACTThe human immunodeficiency virus type 1 (HIV-1) Tat protein, which is essential for HIV gene expression and viral replication, is known to mediate pleiotropic effects on various cell functions. For instance, Tat protein is able to regulate the rate of transcription of host cellular genes and to interact with the signaling machinery, leading to cellular dysfunction. To study the effect that HIV-1 Tat exerts on the host cell, we identified several genes that were up- or down-regulated intat-expressing cell lines by using the differential display method. HIV-1 Tat specifically increases the expression of the cleavage and polyadenylation specificity factor (CPSF) 73-kDa subunit (CPSF3) without affecting the expression of the 160- and 100-kDa subunits of the CPSF complex. This complex comprises four subunits and has a key function in the 3′-end processing of pre-mRNAs by a coordinated interaction with other factors. CPSF3 overexpression experiments and knockdown of the endogenous CPSF3 by mRNA interference have shown that this subunit of the complex is an important regulatory protein for both viral and cellular gene expression. In addition to the known CPSF3 function in RNA polyadenylation, we also present evidence that this protein exerts transcriptional activities by repressing themdm2gene promoter. Thus, HIV-1-Tat up-regulation of CPSF3 could represent a novel mechanism by which this virus increases mRNA processing, causing an increase in both cell and viral gene expression.
Vaccinia Virus G1 Protein, a Predicted Metalloprotease, Is Essential for Morphogenesis of Infectious Virions but Not for Cleavage of Major Core Proteins
Authors: Ansarah-Sobrinho Camilo , Moss Bernard 
Published: June 2004

ABSTRACT

Genes encoding orthologs of the vaccinia virus G1 protein are present in all poxviruses for which sequence information is available, yet neither the role of the protein nor its requirement for virus replication is known. G1 was predicted to be involved in the cleavage of core proteins, based on a transfection study and the presence of an HXXEH motif found in a subset of metallopeptidases. In the present study, we engineered a recombinant vaccinia virus containing a single copy of the G1L gene with a C-terminal epitope tag that is stringently regulated by the
Escherichia coli lac
repressor. In the absence of inducer, expression of G1 was repressed and virus replication was inhibited. Rescue of infectious virus was achieved by expression of wild-type G1 in
trans
, but not when the putative protease active site residues histidine-41, glutamate-44, or histidine-45 were mutated. Nevertheless, the synthesis and proteolytic processing of major core and membrane proteins appeared unaffected under nonpermissive conditions, distinguishing the phenotype of the G1L mutant from one in which the gene encoding the I7 protease was repressed. Noninfectious virus particles, assembled in the absence of inducer, did not attain the oval shape or characteristic core structure of mature virions. The polypeptide composition of these particles, however, closely resembled that of wild-type virus. Full-length and shorter forms of the G1 protein were found in the core fraction of virus particles assembled in the presence of inducer, suggesting that G1 is processed by self-cleavage or by another protease.
Nef Proteins from Simian Immunodeficiency Virus-Infected Chimpanzees Interact with p21-Activated Kinase 2 and Modulate Cell Surface Expression of Various Human Receptors
Authors: Kirchhoff Frank , Schindler Michael , Bailer Nicola , Renkema G. Herma , Saksela Kalle , Knoop Volker , Müller-Trutwin Michaela C. , Santiago Mario L. , Bibollet-Ruche Frederic , Dittmar Matthias T. , Heeney Jonathan L. , Hahn Beatrice H. , Münch Jan 
Published: June 2004

ABSTRACTThe accessory Nef protein allows human immunodeficiency virus type 1 (HIV-1) to persist at high levels and to cause AIDS in infected humans. The function of HIV-1 group M subtype Bnefalleles has been extensively studied, and a variety of in vitro activities believed to be important for viral pathogenesis have been established. However, the function ofnefalleles derived from naturally simian immunodeficiency virus (SIV)-infected chimpanzees, the original host of HIV-1, or from the HIV-1 N and O groups resulting from independent zoonotic transmissions remains to be investigated. In the present study we demonstrate that SIVcpz and HIV-1 group N or Onefalleles down-modulate CD4, CD28, and class I or II MHC molecules and up-regulate surface expression of the invariant chain (Ii) associated with immature major histocompatibility complex (MHC) class II. Furthermore, the ability of Nef to interact with the p21-activated kinase 2 was generally conserved. The functional activity of HIV-1 group N and Onefgenes did not differ significantly from group Mnefalleles. However, SIVcpznefgenes as a group showed a 1.8- and 2.0-fold-higher activity in modulating CD28 (P= 0.0002) and Ii (P= 0.016) surface expression, respectively, but were 1.7-fold less active in down-regulating MHC class II molecules (P= 0.006) compared to HIV-1 Mnefgenes. Our finding that primary SIVcpznefalleles derived from naturally infected chimpanzees modulate the surface expression of various human cellular receptors involved in T-cell activation and antigen presentation suggests that functionalnefgenes helped the chimpanzee virus to persist efficiently in infected humans immediately after zoonotic transmission.
RNA Interference Targeting VP1 Inhibits Foot-and-Mouth Disease Virus Replication in BHK-21 Cells and Suckling Mice
Authors: Chen Weizao , Yan Weiyao , Du Qingyun , Fei Liang , Liu Mingqiu , Ni Zheng , Sheng Zutian , Zheng Zhaoxin 
Published: June 2004

ABSTRACT
RNA interference (RNAi) is a powerful tool to silence gene expression posttranscriptionally. In this study, we evaluated the antiviral potential of small interfering RNA (siRNA) targeting VP1 of foot-and-mouth disease virus (FMDV), which is essential during the life cycle of the virus and plays a key role in virus attachment to susceptible cells. We investigated in vivo the inhibitory effect of VP1-specific siRNAs on FMDV replication in BHK-21 cells and suckling mice, a commonly used small animal model. The results showed that transfection of siRNA-expressing plasmids gave an 80 to 90% reduction in the expression of FMDV VP1 in BHK-21 cells. Moreover, BHK-21 cells transiently transfected with siRNA-expressing plasmids were specifically resistant to FMDV infection when exposed to 100 50% tissue culture infective doses of virus, and the antiviral effects extended to almost 48 h postinfection. Furthermore, subcutaneous injection of siRNA-expressing plasmids in the neck made suckling mice significantly less susceptible to FMDV. In conclusion, our data suggests that RNAi may provide a viable therapeutic approach to treat FMDV infection.
The Two Major Human Metapneumovirus Genetic Lineages Are Highly Related Antigenically, and the Fusion (F) Protein Is a Major Contributor to This Antigenic Relatedness
Authors: Skiadopoulos Mario H. , Biacchesi Stéphane , Buchholz Ursula J. , Riggs Jeffrey M. , Surman Sonja R. , Amaro-Carambot Emerito , McAuliffe Josephine M. , Elkins William R. , St. Claire Marisa , Collins Peter L. , Murphy Brian R. 
Published: June 2004

ABSTRACT

The growth properties and antigenic relatedness of the CAN98-75 (CAN75) and the CAN97-83 (CAN83) human metapneumovirus (HMPV) strains, which represent the two distinct HMPV genetic lineages and exhibit 5 and 63% amino acid divergence in the fusion (F) and attachment (G) proteins, respectively, were investigated in vitro and in rodents and nonhuman primates. Both strains replicated to high titers (≥6.0 log
10
) in the upper respiratory tract of hamsters and to moderate titers (≥3.6 log
10
) in the lower respiratory tract. The two lineages exhibited 48% antigenic relatedness based on reciprocal cross-neutralization assay with postinfection hamster sera, and infection with each strain provided a high level of resistance to reinfection with the homologous or heterologous strain. Hamsters immunized with a recombinant human parainfluenza virus type 1 expressing the fusion F protein of the CAN83 strain developed a serum antibody response that efficiently neutralized virus from both lineages and were protected from challenge with either HMPV strain. This result indicates that the HMPV F protein is a major antigenic determinant that mediates extensive cross-lineage neutralization and protection. Both HMPV strains replicated to low titers in the upper and lower respiratory tracts of rhesus macaques but induced high levels of HMPV-neutralizing antibodies in serum effective against both lineages. The level of HMPV replication in chimpanzees was moderately higher, and infected animals developed mild colds. HMPV replicated the most efficiently in the respiratory tracts of African green monkeys, and the infected animals developed a high level of HMPV serum-neutralizing antibodies (1:500 to 1:1,000) effective against both lineages. Reciprocal cross-neutralization assays in which postinfection sera from all three primate species were used indicated that CAN75 and CAN83 are 64 to 99% related antigenically. HMPV-infected chimpanzees and African green monkeys were highly protected from challenge with the heterologous HMPV strain. Taken together, the results from hamsters and nonhuman primates support the conclusion that the two HMPV genetic lineages are highly related antigenically and are not distinct antigenic subtypes or subgroups as defined by reciprocal cross-neutralization in vitro.
Functional Analysis of the Putative Fusion Domain of the Baculovirus Envelope Fusion Protein F
Authors: Westenberg Marcel , Veenman Frank , Roode Els C. , Goldbach Rob W. , Vlak Just M. , Zuidema Douwe 
Published: June 2004

ABSTRACT

Group II nucleopolyhedroviruses (NPVs), e.g.,
Spodoptera exigua M
NPV, lack a GP64-like protein that is present in group I NPVs but have an unrelated envelope fusion protein named F. In contrast to GP64, the F protein has to be activated by a posttranslational cleavage mechanism to become fusogenic. In several vertebrate viral fusion proteins, the cleavage activation generates a new N terminus which forms the so-called fusion peptide. This fusion peptide inserts in the cellular membrane, thereby facilitating apposition of the viral and cellular membrane upon sequential conformational changes of the fusion protein. A similar peptide has been identified in NPV F proteins at the N terminus of the large membrane-anchored subunit F
1
. The role of individual amino acids in this putative fusion peptide on viral infectivity and propagation was studied by mutagenesis. Mutant F proteins with single amino acid changes as well as an F protein with a deleted putative fusion peptide were introduced in
gp64
-null
Autographa californica M
NPV budded viruses (BVs). None of the mutations analyzed had an major effect on the processing and incorporation of F proteins in the envelope of BVs. Only two mutants, one with a substitution for a hydrophobic residue (F152R) and one with a deleted putative fusion peptide, were completely unable to rescue the
gp64
-null mutant. Several nonconservative substitutions for other hydrophobic residues and the conserved lysine residue had only an effect on viral infectivity. In contrast to what was expected from vertebrate virus fusion peptides, alanine substitutions for glycines did not show any effect.
Sequence and Organization of the
Neodiprion lecontei
Nucleopolyhedrovirus Genome
Authors: Lauzon Hilary A. M. , Lucarotti Christopher J. , Krell Peter J. , Feng Qili , Retnakaran Arthur , Arif Basil M. 
Published: June 2004

ABSTRACT

All fully sequenced baculovirus genomes, with the exception of the dipteran
Culex nigripalpus
nucleopolyhedrovirus (CuniNPV), have previously been from Lepidoptera. This study reports the sequencing and characterization of a hymenopteran baculovirus,
Neodiprion lecontei
nucleopolyhedrovirus (NeleNPV), from the redheaded pine sawfly. NeleNPV has the smallest genome so far published (81,755 bp) and has a GC content of only 33.3%. It contains 89 potential open reading frames, 43 with baculovirus homologues, 6 identified by conserved domains, and 1 with homology to a densovirus structural protein. Average amino acid identity of homologues ranged from 19.7% with CuniNPV to 24.9% with
Spodoptera exigua
nucleopolyhedrovirus. The conserved set of baculovirus genes has dropped to 29, since NeleNPV lacks an F protein homologue (ac23/ld130). NeleNPV contains 12 conserved lepidopteran baculovirus genes, including that for DNA binding protein, late expression factor 11 (
lef
-
11
),
polyhedrin
,
occlusion derived virus envelope protein
-
18
(
odv-e18
),
p40
, and
p45
, but lacks 21 others, including
lef
-
3
,
me53
,
immediate early gene
-
1
,
lef
-
6
,
pp31
,
odv-e66
,
few polyhedra 25k
,
odv-e25
,
protein kinase
-
1
,
fibroblast growth factor
, and
ubiquitin
. The lack of identified baculovirus homologues may be due to difficulties in identification, differences in host-virus interactions, or other genes performing similar functions. Gene parity plots showed limited colinearity of NeleNPV with other baculoviruses, and phylogenetic analysis indicates that NeleNPV may have existed before the lepidopteran nucleopolyhedrovirus and granulovirus divergence. The creation of two new
Baculoviridae
genera to fit hymenopteran and dipteran baculoviruses may be necessary.
Noninfectious X4 but Not R5 Human Immunodeficiency Virus Type 1 Virions Inhibit Humoral Immune Responses in Human Lymphoid Tissue Ex Vivo
Authors: Fitzgerald Wendy , Sylwester Andrew W. , Grivel Jean-Charles , Lifson Jeffrey D. , Margolis Leonid B. 
Published: June 2004

ABSTRACTEx vivo human immunodeficiency virus type 1 (HIV-1) infection of human lymphoid tissue recapitulates some aspects of in vivo HIV-1 infection, including a severe depletion of CD4+T cells and suppression of humoral immune responses to recall antigens or to polyclonal stimuli. These effects are induced by infection with X4 HIV-1 variants, whereas infection with R5 variants results in only mild depletion of CD4+T cells and no suppression of immune responses. To study the mechanisms of suppression of immune responses in this ex vivo system, we used aldrithiol-2 (AT-2)-inactivated virions that have functional envelope glycoproteins but are not infectious and do not deplete CD4+T cells in human lymphoid tissues ex vivo. Nevertheless, AT-2-inactivated X4 (but not R5) HIV-1 virions, even with only a brief exposure, inhibit antibody responses in human lymphoid tissue ex vivo, similarly to infectious virus. This phenomenon is mediated by soluble immunosuppressive factor(s) secreted by tissue exposed to virus.
Myxoma Virus M11L Prevents Apoptosis through Constitutive Interaction with Bak
Authors: Wang Gen , Barrett John W. , Nazarian Steven H. , Everett Helen , Gao Xiujuan , Bleackley Chris , Colwill Karen , Moran Michael F. , McFadden Grant 
Published: June 2004

ABSTRACT

M11L, a 166-amino-acid antiapoptotic protein of myxoma virus, was previously shown to bind to the peripheral benzodiazepine receptor by hydrophobic interactions at the outer mitochondrial membrane. Here we demonstrate that an additional property of M11L is the ability to constitutively form inhibitory complexes with the proapoptotic Bcl-2 family member Bak in human cells. This binding interaction was identified by both FLAG-tagged pull-down assays and tandem affinity purification from transfected and virus-infected human cells. M11L binds constitutively to human Bak and, under some inducible conditions, to human Bax as well, but not to the other Bcl-2 family members (Bad, Bid, Bcl-2). When stably expressed in human embryonic kidney (HEK293) cells, M11L effectively protects these cells from Fas ligand-induced apoptosis, thereby blocking release of cytochrome
c
, activation of caspase 9, and cleavage of poly(ADP-ribose) polymerase. We also demonstrate in coexpression studies that M11L can interact with Bak independently of any involvement with Bax. Furthermore, cells stably expressing M11L function to prevent apoptosis that is induced by overexpression of Bak. We conclude that M11L inhibits, in a species-independent fashion, apoptotic signals mediated by activation of Bak.
Mutations in the Human Cytomegalovirus UL27 Gene That Confer Resistance to Maribavir
Authors: Chou Sunwen , Marousek Gail I. , Senters Anne E. , Davis Michelle G. , Biron Karen K. 
Published: June 2004

ABSTRACT
Previous drug selection experiments resulted in the isolation of a human cytomegalovirus (CMV) UL97 phosphotransferase mutant resistant to the benzimidazole compound maribavir (1263W94), reflecting the anti-UL97 effect of this drug. Three other CMV strains were plaque purified during these experiments. These strains showed lower-grade resistance to maribavir than the UL97 mutant. Extensive DNA sequence analyses showed no changes from the baseline strain AD169 in UL97, the genes involved in DNA replication, and most structural proteins. However, changes were identified in UL27 where each strain contained a different mutation (R233S, W362R, or a combination of A406V and a stop at codon 415). The mutation at codon 415 is predicted to truncate the expressed UL27 protein by 193 codons (32% of UL27) with a loss of nuclear localization. The expression of full-length UL27 as a green fluorescent fusion protein in uninfected fibroblasts resulted in nuclear and nucleolar fluorescence, whereas cytoplasmic localization was observed when codons 1 to 415 were similarly expressed. Viable UL27 deletion mutants were created by recombination and showed slight growth attenuation and maribavir resistance in cell culture. Marker transfer experiments confirmed that UL27 mutations conferred maribavir resistance. The UL27 sequence was well conserved in a sample of 16 diverse clinical isolates. Mutation in UL27, a betaherpesvirus-specific early gene of unknown biological function, may adapt the virus for growth in the absence of UL97 activity.
Actin Cytoskeletal Reorganizations and Coreceptor-Mediated Activation of Rac during Human Immunodeficiency Virus-Induced Cell Fusion
Authors: Pontow S. E. , Heyden N. Vander , Wei S. , Ratner L. 
Published: June 2004

ABSTRACTThe membrane fusion events which initiate human immunodeficiency virus type 1 (HIV-1) infection and promote cytopathic syncytium formation in infected cells commence with the binding of the HIV envelope glycoprotein (Env) to CD4 and an appropriate coreceptor. Here, we show that HIV Env-coreceptor interactions activate Rac-1 GTPase and stimulate the actin filament network reorganizations that are requisite components of the cell fusion process. Disrupting actin filament dynamics with jasplakinolide or latrunculin A arrested fusion at a late step in the formation of Env-CD4-coreceptor complexes. Time-lapse confocal microscopy of living cells revealed vigorous activity of actin-based, target cell membrane extensions at the target cell-Env-expressing cell interface. The expression of dominant-negative forms of actin-regulating Rho-family GTPases established that HIV Env-mediated syncytium formation relies on Rac-1 but not on Cdc42 or Rho activation in target cells. Similar dependencies were found when cell fusion was induced by Env expressed on viral or cellular membranes. Additionally, Rac activity was specifically upregulated in a coreceptor-dependent manner in fusion reaction cell lysates. These results define a role for HIV Env-coreceptor interactions in activating the cellular factors essential for virus-cell and cell-cell fusion and provide evidence for the participation of pertussis toxin-insensitive signaling pathways in HIV-induced membrane fusion.
Prion Infection of Epithelial Rov Cells Is a Polarized Event
Authors: Paquet Sophie , Sabuncu Elifsu , Delaunay Jean-Louis , Laude Hubert , Vilette Didier 
Published: June 2004

ABSTRACT
During prion infections, the cellular glycosylphosphatidylinositol-anchored glycoprotein PrP is converted into a conformational isoform. This abnormal conformer is thought to recruit and convert the normal cellular PrP into a likeness of itself and is proposed to be the infectious agent. We investigated the distribution of the PrP protein on the surface of Rov cells, an epithelial cell line highly permissive to prion multiplication, and we found that PrP is primarily expressed on the apical side. We further show that prion transmission to Rov cells is much more efficient if infectivity contacts the apical side, indicating that the apical and basolateral sides of Rov cells are not equally competent for prion infection and adding prions to the list of the conventional infectious agents (viruses and bacteria) that infect epithelial cells in a polarized manner. These data raise the possibility that apically expressed PrP may be involved in this polarized process of infection. This would add further support for a crucial role of PrP at the cell surface in prion infection of target cells.