bluuebunny/crossref_metadata_2025 huggingface dataset:
Papillomavirus Capsid Mutation To Escape Dendritic Cell-Dependent Innate Immunity in Cervical Cancer
Authors: Yang Rongcun , Wheeler Cosette M. , Chen Xiaojiang , Uematsu Satoshi , Takeda Kiyoshi , Akira Shizuo , Pastrana Diana V. , Viscidi Raphael P. , Roden Richard B. S.
Published: May 2005

Infection with oncogenic human papillomaviruses (HPVs), typified by HPV type 16 (HPV16), is a necessary cause of cervical cancer. Prophylactic vaccination with HPV16 L1 virus-like particles (VLPs) provides immunity. HPV16 VLPs activate dendritic cells and a potent neutralizing immunoglobulin G (IgG) response, yet many cervical cancer patients fail to generate detectable VLP-specific IgG. Therefore, we examined the role of the innate recognition of HPV16 L1 in VLP-induced immune responses and its evasion during carcinogenesis. Nonconservative mutations within HPV16 L1 have been described in isolates from cervical cancer and its precursor, high-grade cervical intraepithelial neoplasia (CIN). We determined the effect of mutations in L1 upon in vitro self-assembly into VLPs and their influence upon the induction of innate and adaptive immune responses in mice. Several nonconservative mutations in HPV16 L1 isolated from high-grade CIN or cervical carcinoma prevent self-assembly of L1 VLPs. Intact VLPs, but not assembly-defective L1, activate dendritic cells to produce proinflammatory factors, such as alpha interferon, that play a critical role in inducing adaptive immunity. Indeed, effective induction of L1-specific IgG1 and IgG2a was dependent upon intact VLP structure. Dendritic cell activation and production of virus-specific neutralizing IgG by VLPs requires MyD88-dependent signaling, although the L1 structure that initiates MyD88-mediated signaling is distinct from the neutralizing epitopes. We conclude that innate recognition of the intact L1 VLP structure via MyD88 is critical in the induction of high-titer neutralizing IgG. Tumor progression is associated with genetic instability and L1 mutants. Selection for assembly-deficient L1 mutations suggests the evasion of MyD88-dependent immune control during cervical carcinogenesis.
The Carboxyl-Terminal Domain of RNA Polymerase II Is Phosphorylated by a Complex Containing cdk9 and Infected-Cell Protein 22 of Herpes Simplex Virus 1
Authors: Durand Lizette O. , Advani Sunil J. , Poon Alice P. W. , Roizman Bernard
Published: May 2005

The infected-cell protein 22 (ICP22), a regulatory protein encoded by the α22 gene of herpes simplex virus 1, is required for the optimal expression of a set of late viral proteins that includes the products of the U
S
11, U
L
38, and U
L
41 genes. ICP22 has two activities. Thus, ICP22 and the U
L
13 protein kinase mediate the activation of cdc2 and degradation of its partners, cyclins A and B. cdc2 and its new partner, the DNA polymerase accessory factor (U
L
42), bind topoisomerase IIα in an ICP22-dependent manner. In addition, ICP22 and U
L
13 mediate an intermediate phosphorylation of the carboxyl terminus of RNA polymerase II (RNA POL II). Here we report another function of ICP22. Thus, ICP22 physically interacts with cdk9, a constitutively active cyclin-dependent kinase involved in transcriptional regulation. A protein complex containing ICP22 and cdk9 phosphorylates in vitro the carboxyl-terminal domain of RNA POL II in a viral U
S
3 protein kinase-dependent fashion. Finally, the carboxyl-terminal domain of RNA POL II fused to glutathione
S
-transferase is phosphorylated in reaction mixtures containing complexes pulled down with ICP22 or cdk9 immune precipitated from lysates of wild-type parent virus or ΔU
L
13 but not ΔU
S
3 mutant-infected cells. The experiments described here place ICP22 and cdk9 in a complex with the carboxyl-terminal domain of RNA POL II. At the same time we confirm the requirement of ICP22 and the U
L
13 protein kinase in the posttranslational modification of RNA POL II that alters its electrophoretic mobility, although U
S
3 kinase appears to play a role in a cell-type-dependent fashion.
Improvement of Influenza A/Fujian/411/02 (H3N2) Virus Growth in Embryonated Chicken Eggs by Balancing the Hemagglutinin and Neuraminidase Activities, Using Reverse Genetics
Authors: Lu Bin , Zhou Helen , Ye Dan , Kemble George , Jin Hong
Published: May 2005

The H3N2 influenza A/Fujian/411/02-like virus strains that circulated during the 2003-2004 influenza season caused influenza epidemics. Most of the A/Fujian/411/02 virus lineages did not replicate well in embryonated chicken eggs and had to be isolated originally by cell culture. The molecular basis for the poor replication of A/Fujian/411/02 virus was examined in this study by the reverse genetics technology. Two antigenically related strains that replicated well in embryonated chicken eggs, A/Sendai-H/F4962/02 and A/Wyoming/03/03, were compared with the prototype A/Fujian/411/02 virus. A/Sendai differed from A/Fujian by three amino acids in the neuraminidase (NA), whereas A/Wyoming differed from A/Fujian by five amino acids in the hemagglutinin (HA). The HA and NA segments of these three viruses were reassorted with cold-adapted A/Ann Arbor/6/60, the master donor virus for the live attenuated type A influenza vaccines (FluMist). The HA and NA residues differed between these three H3N2 viruses evaluated for their impact on virus replication in MDCK cells and in embryonated chicken eggs. It was determined that replication of A/Fujian/411/02 in eggs could be improved by either changing minimum of two HA residues (G186V and V226I) to increase the HA receptor-binding ability or by changing a minimum of two NA residues (E119Q and Q136K) to lower the NA enzymatic activity. Alternatively, recombinant A/Fujian/411/02 virus could be adapted to grow in eggs by two amino acid substitutions in the HA molecule (H183L and V226A), which also resulted in the increased HA receptor-binding activity. Thus, the balance between the HA and NA activities is critical for influenza virus replication in a different host system. The HA or NA changes that increased A/Fujian/411/02 virus replication in embryonated chicken eggs were found to have no significant impact on antigenicity of these recombinant viruses. This study demonstrated that the reverse genetics technology could be used to improve the manufacture of the influenza vaccines.
Protein Kinase C θ Is Not Essential for T-Cell-Mediated Clearance of Murine Gammaherpesvirus 68
Authors: Giannoni Francesca , Lyon Ashley B. , Wareing Mark D. , Dias Peter B. , Sarawar Sally R.
Published: May 2005

Murine gammaherpesvirus 68 (MHV-68) is a naturally occurring rodent pathogen with significant homology to human pathogens Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus. T cells are essential for primary clearance of MHV-68 and survival of mice following intranasal infection. Previous reports have suggested that protein kinase C θ (PKCθ) is essential for T-cell activation and cytokine production in vitro. To determine the role of this molecule in vivo during the immune response to a viral infection, PKCθ−/−mice were infected with MHV-68. Despite the essential role of T cells in viral clearance, PKCθ−/−mice survived infection, cleared lytic virus, and maintained effective long-term control of latency. CD8 T-cell expansion, trafficking to the lung, and cytotoxic activity were similar in PKCθ+/+and PKCθ−/−mice, whereas antiviral antibody and T-helper cell cytokine production were significantly lower in PKCθ−/−mice than in PKCθ+/+mice. These studies demonstrate a differential requirement for PKCθ in the immune response to MHV-68 and show that PKCθ is not essential for the T-cell activation events leading to viral clearance.
Identification of Residues in the Hepatitis C Virus Core Protein That Are Critical for Capsid Assembly in a Cell-Free System
Authors: Klein Kevin C. , Dellos Sheri R. , Lingappa Jaisri R.
Published: May 2005

Significant advances have been made in understanding hepatitis C virus (HCV) replication through development of replicon systems. However, neither replicon systems nor standard cell culture systems support significant assembly of HCV capsids, leaving a large gap in our knowledge of HCV virion formation. Recently, we established a cell-free system in which over 60% of full-length HCV core protein synthesized de novo in cell extracts assembles into HCV capsids by biochemical and morphological criteria. Here we used mutational analysis to identify residues in HCV core that are important for capsid assembly in this highly reproducible cell-free system. We found that basic residues present in two clusters within the N-terminal 68 amino acids of HCV core played a critical role, while the uncharged linker domain between them was not. Furthermore, the aspartate at position 111, the region spanning amino acids 82 to 102, and three serines that are thought to be sites of phosphorylation do not appear to be critical for HCV capsid formation in this system. Mutation of prolines important for targeting of core to lipid droplets also failed to alter HCV capsid assembly in the cell-free system. In addition, wild-type HCV core did not rescue assembly-defective mutants. These data constitute the first systematic and quantitative analysis of the roles of specific residues and domains of HCV core in capsid formation.
The Cellular Chaperone Heat Shock Protein 90 Facilitates Flock House Virus RNA Replication in
Drosophila
Cells
Authors: Kampmueller Kathryn M. , Miller David J.
Published: May 2005

The assembly of viral RNA replication complexes on intracellular membranes represents a critical step in the life cycle of positive-strand RNA viruses. We investigated the role of the cellular chaperone heat shock protein 90 (Hsp90) in viral RNA replication complex assembly and function using Flock House virus (FHV), an alphanodavirus whose RNA-dependent RNA polymerase, protein A, is essential for viral RNA replication complex assembly on mitochondrial outer membranes. The Hsp90 chaperone complex transports cellular mitochondrial proteins to the outer mitochondrial membrane import receptors, and thus we hypothesized that Hsp90 may also facilitate FHV RNA replication complex assembly or function. Treatment of FHV-infected
Drosophila
S2 cells with the Hsp90-specific inhibitor geldanamycin or radicicol potently suppressed the production of infectious virions and the accumulation of protein A and genomic, subgenomic, and template viral RNA. In contrast, geldanamycin did not inhibit the activity of preformed FHV RNA replication complexes. Hsp90 inhibitors also suppressed viral RNA and protein A accumulation in S2 cells expressing an FHV RNA replicon. Furthermore, Hsp90 inhibition with either geldanamycin or RNAi-mediated chaperone downregulation suppressed protein A accumulation in the absence of viral RNA replication. These results identify Hsp90 as a host factor involved in FHV RNA replication and suggest that FHV uses established cellular chaperone pathways to assemble its RNA replication complexes on intracellular membranes.
Human Papillomavirus Type 31b Infection of Human Keratinocytes Does Not Require Heparan Sulfate
Authors: Patterson Nicole A. , Smith Jessica L. , Ozbun Michelle A.
Published: May 2005

Oncogenic human papillomaviruses (HPVs) are difficult to study experimentally as they replicate at low levels in vivo. This has precluded the purification of high-risk HPV virions from in vivo lesions. Virus-like particles (VLPs) and pseudovirions from low- and high-risk HPV types can emulate various aspects of HPV virion attachment and infections. These studies suggest that HPV infection is mediated by α6-integrin and/or heparan-sulfonated receptors. However, whether VLPs and pseudovirions accurately reflect the infection process of HPV virions has not been verified. We generated infectious HPV31b virions from organotypic (raft) tissues and performed experimental infections in a variety of cells. Successful infection following viral attachment, internalization, and nuclear transport was assayed by detecting newly synthesized, spliced HPV transcripts using reverse transcription (RT)-PCR or RT-quantitative PCR. Most human epithelial cells were infected with HPV31b at a multiplicity of infection as low as 1 to 10 viral genome equivalents per cell. HPV31b infection was detected in other cell lines, including COS-7 monkey kidney cells, but higher viral multiplicities of infection were required. Heparin preparations of various molecular weights or heparinase I treatment of cells prevented HPV31b infection of COS-7 cells and C-33A human cervical cancer cells in reproducible and dose-dependent manners. However, these reagents were unable to block infection of human keratinocytes, including HaCaT and N/TERT-1 cells and low-passage human foreskin keratinocytes. These data suggest that HPV31b infection of human keratinocytes, the natural host cell for HPV infections in vivo, does not require a heparan-sulfonated receptor, whereas heparan sulfate is important for infection of some other cells.
Complete Translation of the Hepatitis C Virus Genome In Vitro: Membranes Play a Critical Role in the Maturation of All Virus Proteins except for NS3
Authors: Svitkin Yuri V. , Pause Arnim , Lopez-Lastra Marcelo , Perreault Sandra , Sonenberg Nahum
Published: May 2005

We developed an in vitro translation extract from Krebs-2 cells that translates the entire open reading frame of the hepatitis C virus (HCV) strain H77 and properly processes the viral protein precursors when supplemented with canine microsomal membranes (CMMs). Translation of the C-terminal portion of the viral polyprotein in this system is documented by the synthesis of NS5B. Evidence for posttranslational modification of the viral proteins, the N-terminal glycosylation of E1 and the E2 precursor (E2-p7), and phosphorylation of NS5A is presented. With the exception of NS3, efficient generation of all virus-specific proteins is CMM dependent. A time course of the appearance of HCV products indicates that the viral polyprotein is cleaved cotranslationally. A competitive inhibitor of the NS3 protease inhibited accumulation of NS3, NS4B, NS5A, and NS5B, but not that of NS2 or structural proteins. CMMs also stabilized HCV mRNA during translation. Finally, the formyl-[35S]methionyl moiety of the initiator tRNAMetwas incorporated exclusively into the core protein portion of the polyprotein, demonstrating that translation initiation in this system occurs with high fidelity.
Effects of Simian Virus 40 Large and Small Tumor Antigens on Mammalian Target of Rapamycin Signaling: Small Tumor Antigen Mediates Hypophosphorylation of eIF4E-Binding Protein 1 Late in Infection
Authors: Yu Yongjun , Kudchodkar Sagar B. , Alwine James C.
Published: May 2005

We report that late in a simian virus 40 (SV40) infection in CV-1 cells, there are significant decreases in phosphorylations of two mammalian target of rapamycin (mTOR) signaling effectors, the eIF4E-binding protein (4E-BP1) and p70 S6 kinase (p70S6K). The hypophosphorylation of 4E-BP1 results in 4E-BP1 binding to eIF4E, leading to the inhibition of cap-dependent translation. The dephosphorylation of 4E-BP1 is specifically mediated by SV40 small t antigen and requires the protein phosphatase 2A binding domain but not an active DnaJ domain. Serum-starved primary African green monkey kidney (AGMK) cells also showed decreased phosphorylations of mTOR, 4E-BP1, and p70S6K at late times in infection (48 h postinfection [hpi]). However, at earlier times (12 and 24 hpi), in AGMK cells, phosphorylated p70S6K was moderately increased, correlating with a significant increase in phosphorylation of the p70S6K substrate, ribosomal protein S6. Hyperphosphorylation of 4E-BP1 at early times could not be determined, since hyperphosphorylated 4E-BP1 was present in mock-infected AGMK cells. Elevated levels of phosphorylated eIF4G, a third mTOR effector, were detected in both CV-1 and AGMK cells at all times after infection, indicating that eIF4G phosphorylation was induced throughout the infection and unaffected by small t antigen. The data suggest that during SV40 lytic infection in monkey cells, the phosphorylations of p70S6K, S6, and eIF4G are increased early in the infection (12 and 24 hpi), but late in the infection (48 hpi), the phosphorylations of mTOR, p70S6K, and 4E-BP1 are dramatically decreased by a mechanism mediated, at least in part, by small t antigen.
Dynamics of Viral RNA Synthesis during Measles Virus Infection
Authors: Plumet Sébastien , Duprex W. Paul , Gerlier Denis
Published: May 2005

We propose a reference model of the kinetics of a viral RNA-dependent RNA polymerase (vRdRp) activities and its regulation during infection of eucaryotic cells. After measles virus infects a cell, mRNAs from all genes immediately start to accumulate linearly over the first 5 to 6 h and then exponentially until ∼24 h. The change from a linear to an exponential accumulation correlates with de novo synthesis of vRdRp from the incoming template. Expression of the virus nucleoprotein (N) prior to infection shifts the balance in favor of replication. Conversely, inhibition of protein synthesis by cycloheximide favors the latter. The in vivo elongation speed of the viral polymerase is ∼3 nucleotides/s. A similar profile with fivefold-slower kinetics can be obtained using a recombinant virus expressing a structurally altered polymerase. Finally, virions contain only encapsidated genomic, antigenomic, and 5′-end abortive replication fragment RNAs.
The C108g Epitope in the V2 Domain of gp120 Functions as a Potent Neutralization Target When Introduced into Envelope Proteins Derived from Human Immunodeficiency Virus Type 1 Primary Isolates
Authors: Pinter Abraham , Honnen William J. , D'Agostino Paul , Gorny Miroslaw K. , Zolla-Pazner Susan , Kayman Samuel C.
Published: May 2005

Monoclonal antibodies (MAbs) directed against epitopes in the V2 domain of human immunodeficiency virus type 1 gp120 often possess neutralizing activity, but these generally are highly type specific, neutralize only laboratory isolates, or have low potency. The most potent of these is C108g, directed against a type-specific epitope in HXB2 and BaL gp120s, which is glycan dependent and, in contrast to previous reports, dependent on intact disulfide bonds. This epitope was introduced into two primary Envs, derived from a neutralization-sensitive (SF162) and a neutralization-resistant (JR-FL) isolate, by substitution of two residues and, for SF162, addition of an N-linked glycosylation site. C108g effectively neutralized both variant Envs with considerably higher potency than standard MAbs against the V3 and CD4-binding domains and the broadly neutralizing MAbs 2G12 and 2F5. These amino acid substitutions also introduced the epitope recognized by a second V2-specific MAb, 10/76b, but this MAb possessed potent neutralizing activity only in the absence of the glycan required for C108g reactivity. In contrast to other gp120-specific neutralizing MAbs, C108g did not block binding of soluble Env proteins to either the CD4 or the CCR5 receptor, but studies with a fusion-arrested Env indicated that C108g neutralized at a step preceding the one blocked by the gp41-specific MAb, 2F5. These results indicate that the V1/V2 domain possesses targets that mediate potent neutralization of primary viral isolates via a novel mechanism and suggest that inclusion of carbohydrate determinants into these epitopes may help overcome the indirect masking effects that limit the neutralizing potency of antibodies commonly produced after infection.
The 5′-Terminal Region of the Aichi Virus Genome Encodes
cis
-Acting Replication Elements Required for Positive- and Negative-Strand RNA Synthesis
Authors: Nagashima Shigeo , Sasaki Jun , Taniguchi Koki
Published: May 2005

Aichi virus is a member of the family
Picornaviridae
. It has already been shown that three stem-loop structures (SL-A, SL-B, and SL-C, from the 5′ end) formed at the 5′ end of the genome are critical elements for viral RNA replication. In this study, we further characterized the 5′-terminal
cis
-acting replication elements. We found that an additional structural element, a pseudoknot structure, is formed through base-pairing interaction between the loop segment of SL-B (nucleotides [nt] 57 to 60) and a sequence downstream of SL-C (nt 112 to 115) and showed that the formation of this pseudoknot is critical for viral RNA replication. Mapping of the 5′-terminal sequence of the Aichi virus genome required for RNA replication using a series of Aichi virus-encephalomyocarditis virus chimera replicons indicated that the 5′-end 115 nucleotides including the pseudoknot structure are the minimum requirement for RNA replication. Using the cell-free translation-replication system, we examined the abilities of viral RNAs with a lethal mutation in the 5′-terminal structural elements to synthesize negative- and positive-strand RNAs. The results showed that the formation of three stem-loops and the pseudoknot structure at the 5′ end of the genome is required for negative-strand RNA synthesis. In addition, specific nucleotide sequences in the stem of SL-A or its complementary sequences at the 3′ end of the negative-strand were shown to be critical for the initiation of positive-strand RNA synthesis but not for that of negative-strand synthesis. Thus, the 5′ end of the Aichi virus genome encodes elements important for not only negative-strand synthesis but also positive-strand synthesis.
Attenuation of Bunyavirus Replication by Rearrangement of Viral Coding and Noncoding Sequences
Authors: Lowen Anice C. , Boyd Amanda , Fazakerley John K. , Elliott Richard M.
Published: May 2005

Bunyamwera virus (BUN) is the prototype virus of the family
Bunyaviridae
. BUN has a tripartite negative-sense RNA genome comprising small (S), medium (M), and large (L) segments. Partially complementary untranslated regions (UTRs) flank the coding region of each segment. The terminal 11 nucleotides of these UTRs are conserved between the three segments, while the internal regions are unique. The UTRs direct replication and transcription of viral RNA and are sufficient to allow encapsidation of viral RNA into ribonucleoprotein complexes. To investigate the segment-specific functions of the UTRs, we have used reverse genetics to recover a recombinant virus (called BUN MLM) in which the L segment open reading frame (ORF) is flanked by the M segment UTRs. Compared to wild-type virus, BUN MLM virus shows growth attenuation in cultured mammalian cells and a slower disease progression in mice, produces small plaques, expresses reduced levels of L mRNA and L (RNA polymerase) protein, synthesizes less L genomic and antigenomic RNA, and has an increased particle-to-PFU ratio. Our data suggest that the packaging of BUN RNAs is not segment specific. In addition, the phenotype of BUN MLM virus supports the finding that BUN UTRs differ in their regulation of RNA synthesis but suggests that the interplay between each segment UTR and its cognate ORF may contribute to that regulation. Since BUN MLM virus is attenuated due to an essentially irreversible mutation, the rearrangement of UTRs is a feasible strategy for vaccine design for the more pathogenic members of the
Bunyaviridae
.
Cryptic Nature of a Conserved, CD4-Inducible V3 Loop Neutralization Epitope in the Native Envelope Glycoprotein Oligomer of CCR5-Restricted, but Not CXCR4-Using, Primary Human Immunodeficiency Virus Type 1 Strains
Authors: Lusso Paolo , Earl Patricia L. , Sironi Francesca , Santoro Fabio , Ripamonti Chiara , Scarlatti Gabriella , Longhi Renato , Berger Edward A. , Burastero Samuele E.
Published: May 2005

The external subunit of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env), gp120, contains conserved regions that mediate sequential interactions with two cellular receptor molecules, CD4 and a chemokine receptor, most commonly CCR5 or CXCR4. However, antibody accessibility to such regions is hindered by diverse protective mechanisms, including shielding by variable loops, conformational flexibility and extensive glycosylation. For the conserved neutralization epitopes hitherto described, antibody accessibility is reportedly unrelated to the viral coreceptor usage phenotype. Here, we characterize a novel, conserved gp120 neutralization epitope, recognized by a murine monoclonal antibody (MAb), D19, which is differentially accessible in the native HIV-1 Env according to its coreceptor specificity. The D19 epitope is contained within the third variable (V3) domain of gp120 and is distinct from those recognized by other V3-specific MAbs. To study the reactivity of MAb D19 with the native oligomeric Env, we generated a panel of PM1 cells persistently infected with diverse primary HIV-1 strains. The D19 epitope was conserved in the majority (23/29; 79.3%) of the subtype-B strains tested, as well as in selected strains from other genetic subtypes. Strikingly, in CCR5-restricted (R5) isolates, the D19 epitope was invariably cryptic, although it could be exposed by addition of soluble CD4 (sCD4); epitope masking was dependent on the native oligomeric structure of Env, since it was not observed with the corresponding monomeric gp120 molecules. By contrast, in CXCR4-using strains (X4 and R5X4), the epitope was constitutively accessible. In accordance with these results, R5 isolates were resistant to neutralization by MAb D19, becoming sensitive only upon addition of sCD4, whereas CXCR4-using isolates were neutralized regardless of the presence of sCD4. Other V3 epitopes examined did not display a similar divergence in accessibility based on coreceptor usage phenotype. These results provide the first evidence of a correlation between HIV-1 biological phenotype and neutralization sensitivity, raising the possibility that the in vivo evolution of HIV-1 coreceptor usage may be influenced by the selective pressure of specific host antibodies.
Varicella-Zoster Virus ORF4 Latency-Associated Protein Is Important for Establishment of Latency
Authors: Cohen Jeffrey I. , Krogmann Tammy , Ross Jeffrey P. , Pesnicak Lesley , Prikhod'ko Elena A.
Published: May 2005

Varicella-zoster virus (VZV) encodes at least six genes that are expressed during latency. One of the genes, ORF4, encodes an immediate-early protein that is present in the virion tegument. ORF4 RNA and protein have been detected in latently infected human ganglia. We have constructed a VZV mutant deleted for ORF4 and have shown that the gene is essential for replication in vitro. The ORF4 mutant virus could be propagated when grown in cells infected with baculovirus expressing the ORF4 protein under the human cytomegalovirus immediate-early promoter. In contrast, the VZV ORF4 deletion mutant could not be complemented in cells expressing herpes simplex virus type 1 (HSV-1) ICP27, the homolog of ORF4. Cells infected with baculovirus expressing ORF4 did not complement an HSV-1 ICP27 deletion mutant. VZV-infected cotton rats have been used as a model for latency; viral DNA and latency-associated transcripts are expressed in dorsal root ganglia 1 month or more after experimental infection. Cotton rats inoculated with VZV lacking ORF4 showed reduced frequency of latency compared to animals infected with the parental or ORF4-rescued virus. Thus, in addition to VZV ORF63, which was previously shown to be critical for efficient establishment of latency, ORF4 is also important for latent infection.
Strain-Specific T-Cell Suppression and Protective Immunity in Patients with Chronic Hepatitis C Virus Infection
Authors: Sugimoto Kazushi , Kaplan David E. , Ikeda Fusao , Ding Jin , Schwartz Jonathan , Nunes Frederick A. , Alter Harvey J. , Chang Kyong-Mi
Published: May 2005

Hepatitis C virus (HCV) frequently persists with an apparently ineffective antiviral T-cell response. We hypothesized that some patients may be exposed to multiple HCV subtypes and that strain-specific T cells could contribute to the viral dynamics in this setting. To test this hypothesis, CD4 T-cell responses to three genotype 1a-derived HCV antigens and HCV antibody serotype were examined in chronically HCV infected (genotypes 1a, 1b, 2, 3, and 4) and spontaneously HCV recovered subjects. Consistent with multiple HCV exposure, 63% of patients infected with genotypes 2 to 4 (genotypes 2-4) and 36% of those infected with genotype 1b displayed CD4 T-cell responses to 1a-derived HCV antigens, while 29% of genotype 2-4-infected patients showed serotype responses to genotype 1. Detection of 1a-specific T cells in patients without active 1a infection suggested prior self-limited 1a infection with T-cell-mediated protection from 1a but not from non-1a viruses. Remarkably, CD4 T-cell responses to 1a-derived HCV antigens were weakest in patients with homologous 1a infection and greater in non-1a-infected patients: proportions of patients responding were 19% (1a), 36% (1b), and 63% (2-4) (P= 0.0006). Increased 1a-specific CD4 T-cell responsiveness in non-1a-infected patients was not due to increased immunogenicity or cross-reactivity of non-1a viruses but directly related to sequence divergence. We conclude that the T-cell response to the circulating virus is either suppressed or not induced in a strain-specific manner in chronically HCV infected patients and that, despite their ability to clear one HCV strain, patients may be reinfected with a heterologous strain that can then persist. These findings provide new insights into host-virus interactions in HCV infection that have implications for vaccine development.
vLIP, a Viral Lipase Homologue, Is a Virulence Factor of Marek's Disease Virus
Authors: Kamil Jeremy P. , Tischer B. Karsten , Trapp Sascha , Nair Venugopal K. , Osterrieder Nikolaus , Kung Hsing-Jien
Published: May 2005

The genome of Marek's disease virus (MDV) has been predicted to encode a secreted glycoprotein, vLIP, which bears significant homology to the α/β hydrolase fold of pancreatic lipases. Here it is demonstrated that MDV
vLIP
mRNA is produced via splicing and that
vLIP
is a late gene, due to its sensitivity to inhibition of DNA replication. While vLIP was found to conserve several residues essential to hydrolase activity, an unfavorable asparagine substitution is present at the lipase catalytic triad acid position. Consistent with structural predictions, purified recombinant vLIP did not show detectable activity on traditional phospholipid or triacylglyceride substrates. Two different
vLIP
mutant viruses, one bearing a 173-amino-acid deletion in the lipase homologous domain, the other having an alanine point mutant at the serine nucleophile position, caused a significantly lower incidence of Marek's disease in chickens and resulted in enhanced survival relative to two independently produced
vLIP
revertants or parental virus. These data provide the first evidence that vLIP enhances the replication and pathogenic potential of MDV. Furthermore, while vLIP may not serve as a traditional lipase enzyme, the data indicate that the serine nucleophile position is nonetheless essential in vivo for the viral functions of vLIP. Therefore, it is suggested that this particular example of lipase homology may represent the repurposing of an α/β hydrolase fold toward a nonenzymatic role, possibly in lipid bonding.
Paleogenomic Record of the Extinction of Human Endogenous Retrovirus ERV9
Authors: López-Sánchez Paula , Costas Javier C. , Naveira Horacio F.
Published: May 2005

An outstanding question of genome evolution is what stops the invasion of a host genome by transposable elements (TEs). The human genome, harboring the remnants of many extinct TE families, offers an extraordinary opportunity to investigate this problem. ERV9 is an endogenous retrovirus repeatedly mobilized during primate evolution, 15 to 6 million years ago (MYA), which left a trace of over a hundred provirus-like copies and at least 4,000 solitary long terminal repeats (LTRs) in the human genome. Then, its proliferation ceased for unknown reasons, and the family went extinct. We have made a detailed reconstruction of its last active subfamily, ERV9_XII, by examining 115 solitary LTRs from it. These insertions were grouped into 11 sets according to shared nucleotide variants, which could be placed in a sequential order of 10 to 6 MYA. At least 75% of the subfamily was produced 8 to 6 MYA, during a stage of intense proliferation. With new analytical tools, we show that the youngest and most prolific sets may have been produced by effectively instantaneous expansions of corresponding single-sequence variants. The extinction of this family apparently was not a consequence of its slow gradual degeneration, but the outcome of the fixation of specific restrictive alleles in the human-chimpanzee ancestral population. Three species-specific insertions (two in humans and one in chimpanzees) were identified, further supporting that extinction took place when these two species were beginning to diverge. These are the only fixed differences of this kind so far observed between humans and chimpanzees, apart from those belonging to the human endogenous retrovirus K family.
5′-Terminal Deletions Occur in Coxsackievirus B3 during Replication in Murine Hearts and Cardiac Myocyte Cultures and Correlate with Encapsidation of Negative-Strand Viral RNA
Authors: Kim K.-S. , Tracy S. , Tapprich W. , Bailey J. , Lee C.-K. , Kim K. , Barry W. H. , Chapman N. M.
Published: May 2005

Adult human enteroviral heart disease is often associated with the detection of enteroviral RNA in cardiac muscle tissue in the absence of infectious virus. Passage of coxsackievirus B3 (CVB3) in adult murine cardiomyocytes produced CVB3 that was noncytolytic in HeLa cells. Detectable but noncytopathic CVB3 was also isolated from hearts of mice inoculated with CVB3. Sequence analysis revealed five classes of CVB3 genomes with 5′ termini containing 7, 12, 17, 30, and 49 nucleotide deletions. Structural changes (assayed by chemical modification) in cloned, terminally deleted 5′-nontranslated regions were confined to the cloverleaf domain and localized within the region of the deletion, leaving key functional elements of the RNA intact. Transfection of CVB3 cDNA clones with the 5′-terminal deletions into HeLa cells generated noncytolytic virus (CVB3/TD) which was neutralized by anti-CVB3 serum. Encapsidated negative-strand viral RNA was detected using CsCl-purified CVB3/TD virions, although no negative-strand virion RNA was detected in similarly treated parental CVB3 virions. The viral protein VPg was detected on CVB3/TD virion RNA molecules which terminate in 5′ CG or 5′ AG. Detection of viral RNA in mouse hearts from 1 week to over 5 months postinoculation with CVB3/TD demonstrated that CVB3/TD virus strains replicate and persist in vivo. These studies describe a naturally occurring genomic alteration to an enteroviral genome associated with long-term viral persistence.
A Heptad Repeat in Herpes Simplex Virus 1 gH, Located Downstream of the α-Helix with Attributes of a Fusion Peptide, Is Critical for Virus Entry and Fusion
Authors: Gianni Tatiana , Menotti Laura , Campadelli-Fiume Gabriella
Published: May 2005

Entry of herpes simplex virus 1 (HSV-1) into cells occurs by fusion with cell membranes; it requires gD as the receptor binding glycoprotein and the trigger of fusion, and the trio of the conserved glycoproteins gB, gH, and gL to execute fusion. Recently, we reported that the ectodomain of HSV-1 gH carries a hydrophobic α-helix (residues 377 to 397) with attributes of an internal fusion peptide (T. Gianni, P. L. Martelli, R. Casadio, and G. Campadelli-Fiume, J. Virol.
79:
2931-2940, 2005). Downstream of this α-helix, a heptad repeat (HR) with a high propensity to form a coiled coil was predicted between residues 443 and 471 and was designated HR-1. The simultaneous substitution of two amino acids in HR-1 (E450G and L453A), predicted to abolish the coiled coil, abolished the ability of gH to complement the infectivity of a gH-null HSV mutant. When coexpressed with gB, gD, and gL, the mutant gH was unable to promote cell-cell fusion. These defects were not attributed to a defect in heterodimer formation with gL, the gH chaperone, or in trafficking to the plasma membrane. A 25-amino-acid synthetic peptide with the sequence of HR-1 (pep-gH
wt25
) inhibited HSV replication if present at the time of virus entry into the cell. A scrambled peptide had no effect. The effect was specific, as pep-gH
wt25
did not reduce HSV-2 and pseudorabies virus infection. The presence of a functional HR in the HSV-1 gH ectodomain strengthens the view that gH has attributes typical of a viral fusion glycoprotein.
Hepatitis C Virus Replicons Escape RNA Interference Induced by a Short Interfering RNA Directed against the NS5b Coding Region
Authors: Wilson Joyce A. , Richardson Christopher D.
Published: May 2005

RNA interference represents an exciting new technology that could have therapeutic applications for the treatment of viral infections. Hepatitis C virus (HCV) is a major cause of chronic liver disease and affects over 270 million individuals worldwide. The HCV genome is a single-stranded RNA that functions as both an mRNA and a replication template, making it an attractive target for therapeutic approaches using short interfering RNA (siRNA). We have shown previously that double-stranded siRNA molecules designed to target the HCV genome block gene expression and RNA synthesis from hepatitis C replicons propagated in human liver cells. However, we now show that this block is not complete. After several treatments with a highly effective siRNA, we have shown growth of replicon RNAs that are resistant to subsequent treatment with the same siRNA. However, these replicon RNAs were not resistant to siRNA targeting another part of the genome. Sequence analysis of the siRNA-resistant replicons showed the generation of point mutations within the siRNA target sequence. In addition, the use of a combination of two siRNAs together severely limited escape mutant evolution. This suggests that RNA interference activity could be used as a treatment to reduce the devastating effects of HCV replication on the liver and the use of multiple siRNAs could prevent the emergence of resistant viruses.
Induction of Systemic and Mucosal Cross-Clade Neutralizing Antibodies in BALB/c Mice Immunized with Human Immunodeficiency Virus Type 1 Clade A Virus-Like Particles Administered by Different Routes of Inoculation
Authors: Buonaguro L. , Visciano M. L. , Tornesello M. L. , Tagliamonte M. , Biryahwaho B. , Buonaguro F. M.
Published: May 2005

We have recently developed a candidate human immunodeficiency virus type 1 (HIV-1) vaccine model, based on virus-like particles (VLPs) expressing gp120 from a Ugandan HIV-1 isolate of clade A (HIV-VLPAs), which shows the induction of neutralizing antibodies as well as cytotoxic T lymphocytes (CTL) in BALB/c mice by intraperitoneal (i.p.) administration. In the present study, immunization experiments based on a multiple-dose regimen have been performed with BALB/c mice to compare different routes of administration. i.p. and intranasal (i.n.), but not oral, administration induce systemic as well as mucosal (vaginal and intestinal) immunoglobulin G (IgG) and IgA responses. These immune sera exhibit >50% ex vivo neutralizing activity against both autologous and heterologous primary isolates. Furthermore, the administration of HIV-VLPAs by the i.n. immunization route induces a specific CTL activity, although at lower efficiency than the i.p. route. The HIV-VLPAs represent an efficient strategy to stimulate both arms of immunity; furthermore, the induction of specific humoral immunity at mucosal sites, which nowadays represent the main port of entry for HIV-1 infection, is of great interest. All these properties, and the possible cross-clade in vivo protection, could make these HIV-VLPAs a good candidate for a mono- and multicomponent worldwide preventive vaccine approach not restricted to high-priority regions, such as sub-Saharan countries.
Human Herpesvirus 7 Open Reading Frames U12 and U51 Encode Functional β-Chemokine Receptors
Authors: Tadagaki Kenjiro , Nakano Kazushi , Yamanishi Koichi
Published: May 2005

Human herpesvirus 7 (HHV-7), which belongs to the betaherpesvirus subfamily and infects mainly CD4
+
T cells in vitro, infects children during infancy. HHV-7 contains two genes, U12 and U51, that encode putative homologs of cellular G-protein-coupled receptors. To analyze the biological function of the U12 and U51 genes, we cloned these genes and expressed the proteins in cells. U12 and U51 encoded functional calcium-mobilizing receptors for β-chemokines, which include thymus and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC), EBI1-ligand chemokine (ELC), and secondary lymphoid-tissue chemokine (SLC), but not for other chemokines, suggesting that the chemokine selectivities of the U12 and U51 products were distinct from those of the known mammalian chemokine receptors. ELC and SLC induced migration in Jurkat cells stably expressing U12, but TARC and MDC did not. In contrast, none of these chemokines induced migration in Jurkat cells stably expressing U51. Together, these data indicate that the products of U12 and U51 may play important and different roles in the pathogenesis of HHV-7 through transmembrane signaling.
Enterovirus 70 Binds to Different Glycoconjugates Containing α2,3-Linked Sialic Acid on Different Cell Lines
Authors: Nokhbeh M. Reza , Hazra Samir , Alexander David A. , Khan Ahmar , McAllister Morgan , Suuronen Erik J. , Griffith May , Dimock Kenneth
Published: May 2005

Enterovirus 70 (EV70), the causative agent of acute hemorrhagic conjunctivitis, exhibits a restricted tropism for conjunctival and corneal cells in vivo but infects a wide spectrum of mammalian cells in culture. Previously, we demonstrated that human CD55 is a receptor for EV70 on HeLa cells but that EV70 also binds to sialic acid-containing receptors on a variety of other human cell lines. Virus recognition of sialic acid attached to underlying glycans by a particular glycosidic linkage may contribute to host range, tissue tropism, and pathogenesis. Therefore, we tested the possibility that EV70 binds to α2,3-linked sialic acid, like other viruses associated with ocular infections. Through the use of linkage-specific sialidases, sialyltransferases, and lectins, we show that EV70 recognizes α2,3-linked sialic acid on human corneal epithelial cells and on U-937 cells. Virus attachment to both cell lines is CD55 independent and sensitive to benzylN-acetyl-α-d-galactosaminide, an inhibitor of O-linked glycosylation. Virus binding to corneal cells, but not U-937 cells, is inhibited by proteinase K, but not by phosphatidylinositol-specific phospholipase C treatment. These results are consistent with the idea that a major EV70 receptor on corneal epithelial cells is an O-glycosylated, non-glycosyl phosphatidylinositol-anchored membrane glycoprotein containing α2,3-linked sialic acid, while sialylated receptors on U-937 cells are not proteinaceous.
Biological and Biochemical Characteristics of Prion Strains Conserved in Persistently Infected Cell Cultures
Authors: Arima Kazuhiko , Nishida Noriyuki , Sakaguchi Suehiro , Shigematsu Kazuto , Atarashi Ryuichiro , Yamaguchi Naohiro , Yoshikawa Daisuke , Yoon Jaewoo , Watanabe Ken , Kobayashi Nobuyuki , Mouillet-Richard Sophie , Lehmann Sylvain , Katamine Shigeru
Published: May 2005

Abnormal prion protein (PrP
Sc
) plays a central role in the transmission of prion diseases, but the molecular basis of prion strains with distinct biological characteristics remains to be elucidated. We analyzed the characteristics of prion disease by using mice inoculated with the Chandler and Fukuoka-1 strains propagated in a cultured mouse neuronal cell line, GT1-7, which is highly permissive to replication of the infectious agents. Strain-specific biological characteristics, including clinical manifestations, incubation period as related to the infectious unit, and pathological profiles, remained unchanged after passages in the cell cultures. We noted some differences in the biochemical aspects of PrP
Sc
between brain tissues and GT1-7 cells which were unlikely to affect the strain phenotypes. On the other hand, the proteinase K-resistant PrP core fragments derived from Fukuoka-1-infected tissues and cells were slightly larger than those from Chandler-infected versions. Moreover, Fukuoka-1 infection, but not Chandler infection, gave an extra fragment with a low molecular weight, ∼13 kDa, in both brain tissues and GT1-7 cells. This cell culture model persistently infected with different strains will provide a new insight into the understanding of the molecular basis of prion diversity.
Viral Expression of CCL2 Is Sufficient To Induce Demyelination in RAG1−/−Mice Infected with a Neurotropic Coronavirus
Authors: Kim Taeg S. , Perlman Stanley
Published: May 2005

Mouse hepatitis virus strain JHM causes a chronic demyelinating disease in susceptible strains of rodents. Demyelination does not develop in infected RAG1−/−(recombination activation gene-deficient) mice but can be induced by several experimental interventions, including adoptive transfer of virus-specific T cells or antibodies. A common feature of demyelination in these models is extensive infiltration of macrophages/microglia into the white matter. The data obtained thus far do not indicate whether macrophage/microglia infiltration, in the absence of T cells or antibody, is sufficient to mediate demyelination. To determine whether the expression of a single macrophage chemoattractant, in the context of virus infection, could initiate the demyelinating process, we engineered a recombinant coronavirus that expressed the chemokine CCL2/monocyte chemoattractant protein-1. CCL2 has been implicated in macrophage infiltration into the central nervous system and is involved in demyelination in many experimental models of demyelination. Extensive macrophage/microglia infiltration and demyelination has developed in RAG1−/−mice infected with this recombinant virus. Thus, these results suggest that the minimal requirement for demyelination is increased expression of a single macrophage-attracting chemokine in the context of an inflammatory milieu, such as that induced by a viral infection.
Differences in the Fitness of Two Diverse Wild-Type Human Immunodeficiency Virus Type 1 Isolates Are Related to the Efficiency of Cell Binding and Entry
Authors: Marozsan Andre J. , Moore Dawn M. , Lobritz Michael A. , Fraundorf Erika , Abraha Awet , Reeves Jacqueline D. , Arts Eric J.
Published: May 2005

The ability of one primary human immunodeficiency virus type 1 (HIV-1) isolate to outcompete another in primary CD4
+
human lymphoid cells appears to be mediated by the efficiency of host cell entry. This study was designed to test the role of entry on fitness of wild-type HIV-1 isolates (e.g., replicative capacity) and to examine the mechanism(s) involved in differential entry efficiency. The gp120 coding regions of two diverse HIV-1 isolates (the more-fit subtype B strain, B5-91US056, and less-fit C strain, C5-97ZA003) were cloned into a neutral HIV-1 backbone by using a recently described yeast cloning technique. The fitness of the primary B5 HIV-1 isolates and its
env
gene cloned into the NL4-3 laboratory strain had similar fitness, and both were more fit than the C5 primary isolate and its
env
/NL4-3 chimeric counterpart. Increased fitness of the B5 over C5 virus was mediated by the gp120 coding region of the
env
gene. An increase in binding/fusion, as well as decreased sensitivity to entry inhibitors (PSC-RANTES and T-20), was observed in cell fusion assays mediated by B5 gp120 compared to C5 gp120. Competitive binding assays using a novel whole virus-cell system indicate that the primary or chimeric B5 had a higher avidity for CD4/CCR5 on host cells than the C5 counterpart. This increased avidity of an HIV-1 isolate for its cell receptors may be a significant factor influencing overall replicative capacity or fitness.