bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Residues 121 to 124 of Vesicular Stomatitis Virus Matrix Protein in Virus Assembly and Virus-Host Interaction
Authors: Connor John H. , McKenzie Margie O. , Lyles Douglas S. 
Published: March 2006

ABSTRACT
The recent solution of the crystal structure of a fragment of the vesicular stomatitis virus matrix (M) protein suggested that amino acids 121 to 124, located on a solvent-exposed loop of the protein, are important for M protein self-association and association with membranes. These residues were mutated from the hydrophobic AVLA sequence to the polar sequence DKQQ. Expression and purification of this mutant from bacteria showed that it was structurally stable and that the mutant M protein had self-association kinetics similar to those of the wild-type M protein. Analysis of the membrane association of M protein in the context of infection with isogenic recombinant viruses showed that both wild-type and mutant M proteins associated with membranes to the same extent. Virus expressing the mutant M protein did show an approximately threefold-lower binding affinity of M protein for nucleocapsid-M complexes. In contrast to the relatively minor effects of the M protein mutation on virus assembly, the mutant virus exhibited growth restriction in MDBK but not BHK cells, a slower induction of apoptosis, and lower viral-protein synthesis. Despite translating less viral protein, the mutant virus produced more viral mRNA, showing that the mutant virus could not effectively promote viral translation. These results demonstrate that the 121-to-124 region of the VSV M protein plays a minor role in virus assembly but is involved in virus-host interactions and VSV replication by augmenting viral-mRNA translation.
Evidence for a Functional Link between Uncoating of the Human Immunodeficiency Virus Type 1 Core and Nuclear Import of the Viral Preintegration Complex
Authors: Dismuke David J. , Aiken Christopher 
Published: March 2006

ABSTRACT
Human immunodeficiency virus type 1 (HIV-1) particles begin their replication upon fusion with the plasma membrane of target cells and release of the viral core into the host cell cytoplasm. Soon thereafter, the viral capsid, which is composed of a polymer of the CA protein, disassociates from the internal ribonucleoprotein complex. While this disassembly process remains poorly understood, the available evidence indicates that proper uncoating of the core is a key step in infection. Defects in uncoating most often lead to a failure of the virus to undergo reverse transcription, resulting in an inability to form a functional viral preintegration complex (PIC). In a previous study, we reported that an HIV-1 mutant containing two substitutions in CA (Q63A/67A) was unusual in that it was poorly infectious yet synthesized normal levels of viral DNA. Here we report that this mutant is impaired for nuclear entry. Quantitative analysis of viral DNA synthesis from infected cells by Southern blotting and real-time PCR revealed that the Q63A/Q67A mutant is impaired in the synthesis of one-long terminal repeat (1-LTR) and 2-LTR circles. Isolation of PICs from acutely infected cells revealed that the Q63A/Q67A mutant produces protein-DNA complexes similar to wild-type in yield and overall composition, but these PICs contained elevated levels of CA and were impaired for integration in vitro. These results demonstrate that mutations in CA can have deleterious effects on both nuclear targeting and integration, suggesting that these steps in the HIV-1 life cycle are dependent on proper uncoating of the viral core.
Genetic Analysis of Simian Immunodeficiency Virus Expressed in Milk and Selectively Transmitted through Breastfeeding
Authors: Rychert Jenna , Lacour Nedra , Amedee Angela Martin 
Published: March 2006

ABSTRACT

To develop effective intervention strategies that prevent breast milk transmission of human immunodeficiency virus (HIV), we must understand the specific viral properties and mechanisms responsible for infant infection. We have used lactating rhesus macaques infected with a pathogenic simian immunodeficiency virus (SIV) stock to analyze the viral genotypes expressed in plasma and milk throughout the disease course and to identify those variants ultimately transmitted to infants through breastfeeding. In these studies we observed mother-to-infant transmission of SIV/Delta
B670
by eight females during the chronic phase of disease, and we analyzed by heteroduplex tracking assays and sequence analysis the distribution and fluctuations in viral genotypes expressed. Each female expressed multiple V1 envelope genotypes in milk near the time of transmission, while a single genotype was found in each of the infants. Variants transmitted to infants were not expressed throughout the maternal disease course but were only detected near the time of transmission. The emergence of the transmitted genotype in the dam typically occurred in plasma before milk and was coincident with increased milk viral loads. Transmitted genotypes tended to be longer and more glycosylated and had a less negative charge over the V1 region compared to viral genotypes expressed in milk but not transmitted. These observations demonstrate that specific viral genotypes are selectively transmitted to infants through breastfeeding and support the hypothesis that transmission occurs as genotypes adapt for efficient expression in milk.
U
S
3 and U
S
3.5 Protein Kinases of Herpes Simplex Virus 1 Differ with Respect to Their Functions in Blocking Apoptosis and in Virion Maturation and Egress
Authors: Poon Alice P. W. , Benetti Luca , Roizman Bernard 
Published: March 2006

ABSTRACT

Previously, we reported that the U
S
3 protein kinase blocks apoptosis, that it activates protein kinase A (PKA), that activation of PKA blocks apoptosis in cells infected with a U
S
3 deletion mutant, and that an overlapping transcriptional unit encodes a truncated kinase designated U
S
3.5. Here, we report the properties of the kinases based on comparisons of herpes simplex virus and baculoviruses expressing U
S
3 or U
S
3.5 kinase. Specifically, we report the following. (i) Both kinases mediate the phosphorylation of HDAC1, HDAC2, and the PKA regulatory IIα subunit in the absence of other viral proteins. (ii) Both enzymes mediate the phosphorylation of largely identical sets of proteins carrying the phosphorylation consensus site of PKA, but only U
S
3 blocks apoptosis, suggesting that it is U
S
3 and not PKA that is responsible for the phosphorylation of the proteins bearing the shared consensus phosphorylation site and the antiapoptotic activity. (iii) Both kinases cofractionate with mitochondria. Immune depletion of the U
S
3 and U
S
3.5 kinases from the cytoplasm removed the kinases from the supernatant fraction, but not from the mitochondrial fraction, and therefore, if the antiapoptotic activity of the U
S
3 kinase is expressed in mitochondria, the localization signal and the antiapoptotic functions are located on different parts of the protein. (iv) The U
S
3 protein kinase is required for the translocation of virus particles from the nucleus. Although the U
L
31 protein is phosphorylated in cells infected with the mutant expressing U
S
3.5 kinase, the release of virus particles from nuclei was impeded in some cells, suggesting that the U
S
3 kinase affects the modification of the nuclear membrane more efficiently than the U
S
3.5 kinase.
Full Genomic Analysis of Human Rotavirus Strain B4106 and Lapine Rotavirus Strain 30/96 Provides Evidence for Interspecies Transmission
Authors: Matthijnssens Jelle , Rahman Mustafizur , Martella Vito , Xuelei Yang , De Vos Sofie , De Leener Karolien , Ciarlet Max , Buonavoglia Canio , Van Ranst Marc 
Published: March 2006

ABSTRACT
The Belgian rotavirus strain B4106, isolated from a child with gastroenteritis, was previously found to have VP7 (G3), VP4 (P[14]), and NSP4 (A genotype) genes closely related to those of lapine rotaviruses, suggesting a possible lapine origin or natural reassortment of strain B4106. To investigate the origin of this unusual strain, the gene sequences encoding VP1, VP2, VP3, VP6, NSP1, NSP2, NSP3, and NSP5/6 were also determined. To allow comparison to a lapine strain, the 11 double-stranded RNA segments of a European G3P[14] rabbit rotavirus strain 30/96 were also determined. The complete genome similarity between strains B4106 and 30/96 was 93.4% at the nucleotide level and 96.9% at the amino acid level. All 11 genome segments of strain B4106 were closely related to those of lapine rotaviruses and clustered with the lapine strains in phylogenetic analyses. In addition, sequence analyses of the NSP5 gene of strain B4106 revealed that the altered electrophoretic mobility of NSP5, resulting in a super-short pattern, was due to a gene rearrangement (head-to-tail partial duplication, combined with two short insertions and a deletion). Altogether, these findings confirm that a rotavirus strain with an entirely lapine genome complement was able to infect and cause severe disease in a human child.
The Ribosomal Shunt Translation Strategy of
Cauliflower Mosaic Virus
Has Evolved from Ancient Long Terminal Repeats
Authors: Shababi Monir , Bourque June , Palanichelvam Karuppaiah , Cole Anthony , Xu Dong , Wan Xiu-Feng , Schoelz James 
Published: March 2006

ABSTRACT

We have screened portions of the large intergenic region of the
Cauliflower mosaic virus
(CaMV) genome for promoter activity in baker's yeast (
Saccharomyces cerevisiae
) and have identified an element that contributes to promoter activity in yeast but has negligible activity in plant cells when expressed in an agroinfiltration assay. A search of the yeast genome sequence revealed that the CaMV element had sequence similarity with the R region of the long terminal repeat (LTR) of the yeast Ty1 retrotransposon, with significant statistical confidence. In plants, the same CaMV sequence has been shown to have an essential role in the ribosomal shunt mechanism of translation, as it forms the base of the right arm of the stem-loop structure that is required for the ribosomal shunt. Since the left arm of the stem-loop structure must represent an imperfect reverse copy of the right arm, we propose that the ribosomal shunt has evolved from a pair of LTRs that have become incorporated end to end into the CaMV genome.
Intrarectal Immunization with Rotavirus 2/6 Virus-Like Particles Induces an Antirotavirus Immune Response Localized in the Intestinal Mucosa and Protects against Rotavirus Infection in Mice
Authors: Agnello Davide , Hervé Christine A. , Lavaux Amandine , Darniot Magali , Guillon Patrice , Charpilienne Annie , Pothier Pierre 
Published: March 2006

ABSTRACTRotavirus (RV) is the main etiological agent of severe gastroenteritis in infants, and vaccination seems the most effective way to control the disease. Recombinant rotavirus-like particles composed of the viral protein 6 (VP6) and VP2 (2/6-VLPs) have been reported to induce protective immunity in mice when administered by the intranasal (i.n.) route. In this study, we show that administration of 2/6-VLPs by the intrarectal (i.r.) route together with either cholera toxin (CT) or a CpG-containing oligodeoxynucleotide as the adjuvant protects adult mice against RV infection. Moreover, when CT is used, RV shedding in animals immunized by the i.r. route is even reduced in comparison with that in animals immunized by the i.n. route. Humoral and cellular immune responses induced by these immunization protocols were analyzed. We found that although i.r. immunization with 2/6-VLPs induces lower RV-specific immunoglobulin G (IgG) and IgA levels in serum, intestinal anti-RV IgA production is higher in mice immunized by the i.r. route. Cellular immune response has been evaluated by measuring cytokine production by spleen and Peyer's patch cells (PPs) after ex vivo restimulation with RV. Mice immunized by the i.n. and i.r. routes display higher gamma interferon production in spleen and PPs, respectively. In conclusion, we demonstrate that i.r. immunization with 2/6-VLPs protects against RV infection in mice and is more efficient than i.n. immunization in inducing an anti-RV immune response in intestinal mucosa.
White Spot Syndrome Virus Open Reading Frame 222 Encodes a Viral E3 Ligase and Mediates Degradation of a Host Tumor Suppressor via Ubiquitination
Authors: He Fang , Fenner Beau J. , Godwin Andrew K. , Kwang Jimmy 
Published: March 2006

ABSTRACT

We have characterized a white spot syndrome virus (WSSV) RING-H2-type protein, WSSV222, which is involved in ubiquitination. WSSV222 exhibits RING-H2-dependent E3 ligase activity in vitro in the presence of the specific conjugating enzyme UbcH6. Mutations in the RING-H2 domain abolished WSSV222-dependent ubiquitination, revealing the importance of this domain in WSSV222 function. Yeast two-hybrid and pull-down analyses revealed that WSSV222 interacts with a shrimp tumor suppressor-like protein (TSL) sharing 60% identity with human OVCA1. To better characterize the interaction of WSSV222 and TSL in vivo, we established a stable TSL-expressing cell line derived from the human ovarian cancer cell line A2780, where we observed a TSL-dependent prolonged G
1
phase. Furthermore, we detected WSSV222-mediated ubiquitination and MG132-sensitive degradation of TSL both in shrimp primary cell culture and in the TSL-expressing cell line. Transient expression of TSL in BHK cells leads to apoptosis, which was rescued by WSSV222. Taken together, our data suggest that WSSV222 acts as an antiapoptosis protein by ubiquitin-mediated proteolysis of TSL to ensure successful WSSV replication in shrimp.
Phosphorylation Mutants of JC Virus Agnoprotein Are Unable To Sustain the Viral Infection Cycle
Authors: Sariyer Ilker K. , Akan Ilhan , Palermo Victoria , Gordon Jennifer , Khalili Kamel , Safak Mahmut 
Published: March 2006

ABSTRACT
Many eukaryotic and viral regulatory proteins are known to undergo posttranslational modifications including phosphorylation, which plays a critical role in many aspects of cell function. Previous studies from our and other laboratories indicated that the JC virus (JCV) late regulatory protein, agnoprotein, plays an important role in the JCV life cycle. Agnoprotein contains several potential phosphorylation sites, including Ser7, Ser11, and Thr21, which are potential targets for the serine/threonine-specific protein kinase C (PKC). In this study, we investigated the functional significance of these phosphorylation sites for the activity of agnoprotein. In vitro and in vivo kinase assays demonstrated that agnoprotein is a target for phosphorylation by PKC. In addition, each of the PKC phosphorylation sites was mutated to Ala singly and in combination, and the effects of these mutations on the JCV life cycle were analyzed. Although the expression of each mutant agnoprotein was detectable during the infection cycle, virus containing each of these mutations failed to propagate. These results contrast with those obtained with an agnoprotein start codon point (Pt) mutant where agnoprotein expression was completely inhibited. The Pt mutant was viable but replicates less efficiently than the wild type (WT). Moreover, conservative substitutions at PKC phosphorylation sites (Ser7, Ser11, and Thr21 to Asp) resulted in a viable virus, which further demonstrate the importance of these sites on agnoprotein function. Further analysis of the mutants by viral release assay and electron microscopy studies revealed that viral particles were efficiently released from infected cells and morphologically indistinguishable from those of WT but were deficient in DNA content. This may account for the defective propagation of the mutants. These results imply that phosphorylated forms of agnoprotein may have essential functions in the viral life cycle and serve as potential targets for therapeutic interventions to limit JCV propagation and JCV-induced diseases.
Function of Bovine CD46 as a Cellular Receptor for Bovine Viral Diarrhea Virus Is Determined by Complement Control Protein 1
Authors: Krey Thomas , Himmelreich Anke , Heimann Manuela , Menge Christian , Thiel Heinz-Jürgen , Maurer Karin , Rümenapf Till 
Published: March 2006

ABSTRACTThe pestivirus bovine viral diarrhea virus (BVDV) was shown to bind to the bovine CD46 molecule, which subsequently promotes entry of the virus. To assess the receptor usage of BVDV type 1 (BVDV-1) and BVDV-2, 30 BVDV isolates including clinical samples were assayed for their sensitivity to anti-CD46 antibodies. With a single exception the infectivity of all tested strains of BVDV-1 and BVDV-2 was inhibited by anti-CD46 antibodies, which indicates the general usage of CD46 as a BVDV receptor. Molecular analysis of the interaction between CD46 and the BVD virion was performed by mapping the virus binding site on the CD46 molecule. Single complement control protein modules (CCPs) within the bovine CD46 were either deleted or replaced by analogous CCPs of porcine CD46, which does not bind BVDV. While the epitopes recognized by anti-CD46 monoclonal antibodies which block BVDV infection were attributed to CCP1 and CCP2, in functional assays only CCP1 turned out to be essential for BVDV binding and infection. Within CCP1 two short peptides on antiparallel beta strands were identified as crucial for the binding of BVDV. Exchanges of these two peptide sequences were sufficient for a loss of function in bovine CD46 as well as a gain of function in porcine CD46. Determination of the size constraints of CD46 revealed that a minimum length of four CCPs is essential for receptor function. An increase of the distance between the virus binding domain and the plasma membrane by insertion of one to six CCPs of bovine C4 binding protein exhibited only a minor influence on susceptibility to BVDV.
Antibody Production and In Vitro Behavior of CD27-Defined B-Cell Subsets: Persistent Hepatitis C Virus Infection Changes the Rules
Authors: Racanelli Vito , Frassanito Maria Antonia , Leone Patrizia , Galiano Maria , De Re Valli , Silvestris Franco , Dammacco Franco 
Published: March 2006

ABSTRACTThere is growing interest in the tendency of B cells to change their functional program in response to overwhelming antigen loading, perhaps by regulating specific parameters, such as efficiency of activation, proliferation rate, differentiation to antibody-secreting cells (ASC), and rate of cell death in culture. We show that individuals persistently infected with hepatitis C virus (HCV) carry high levels of circulating immunoglobulin G (IgG) and IgG-secreting cells (IgG-ASC). Thus, generalized polyclonal activation of B-cell functions may be supposed. While IgGs include virus-related and unrelated antibodies, IgG-ASC do not include HCV-specific plasma cells. Despite signs of widespread activation, B cells do not accumulate and memory B cells seem to be reduced in the blood of HCV-infected individuals. This apparent discrepancy may reflect the unconventional activation kinetics and functional responsiveness of the CD27+B-cell subset in vitro. Following stimulation with T-cell-derived signals in the absence of B-cell receptor (BCR) engagement, CD27+B cells do not expand but rapidly differentiate to secrete Ig and then undergo apoptosis. We propose that their enhanced sensitivity to BCR-independent noncognate T-cell help maintains a constant level of nonspecific serum antibodies and ASC and serves as a backup mechanism of feedback inhibition to prevent exaggerated B-cell responses that could be the cause of significant immunopathology.
Dissecting Rotavirus Particle-Raft Interaction with Small Interfering RNAs: Insights into Rotavirus Transit through the Secretory Pathway
Authors: Cuadras Mariela A. , Bordier Bruno B. , Zambrano Jose L. , Ludert Juan E. , Greenberg Harry B. 
Published: March 2006

ABSTRACT
Studies of rotavirus morphogenesis, transport, and release have shown that although these viruses are released from the apical surface of polarized intestinal cells before cellular lysis, they do not follow the classic exocytic pathway. Furthermore, increasing evidence suggests that lipid rafts actively participate in the exit of rotavirus from the infected cell. In this study, we silenced the expression of VP4, VP7, and NSP4 by using small interfering RNAs (siRNAs) and evaluated the effect of shutting down the expression of these proteins on rotavirus-raft interactions. Silencing of VP4 and NSP4 reduced the association of rotavirus particles with rafts; in contrast, inhibition of VP7 synthesis slightly affected the migration of virions into rafts. We found that inhibition of rotavirus migration into lipid rafts, by either siRNAs or tunicamycin, also specifically blocked the targeting of VP4 to rafts, suggesting that the association of VP4 with rafts is mostly mediated by the formation of viral particles in the endoplasmic reticulum (ER). We showed that two populations of VP4 exist, one small population that is independently targeted to rafts and a second large pool of VP4 whose association with rafts is mediated by particle formation in the ER. We also present evidence to support the hypothesis that assembly of VP4 into mature virions takes place in the late stages of transit through the ER. Finally, we analyzed the progression of rotavirus proteins in the exocytic pathway and found that VP4 and virion-assembled VP7 colocalized with ERGIC-53, suggesting that rotavirus particles transit through the intermediate compartment between the ER and the Golgi complex.
In Vivo Ablation of CD11c-Positive Dendritic Cells Increases Susceptibility to Herpes Simplex Virus Type 1 Infection and Diminishes NK and T-Cell Responses
Authors: Kassim Sadik H. , Rajasagi Naveen K. , Zhao Xiangyi , Chervenak Robert , Jennings Stephen R. 
Published: March 2006

ABSTRACTThe precise role of each of the seven individual CD11c+dendritic cell subsets (DCs) identified to date in the response to viral infections is not known. DCs serve as critical links between the innate and adaptive immune responses against many pathogens, including herpes simplex virus type 1 (HSV-1). The role of DCs as mediators of resistance to HSV-1 infection was investigated using CD11c-diphtheria toxin (DT) receptor-green fluorescent protein transgenic mice, in which DCs can be transiently depleted in vivo by treatment with low doses of DT. We show that ablation of DCs led to enhanced susceptibility to HSV-1 infection in the highly resistant C57BL/6 mouse strain. Specifically, we showed that the depletion of DCs led to increased viral spread into the nervous system, resulting in an increased rate of morbidity and mortality. Furthermore, we showed that ablation of DCs impaired the optimal activation of NK cells and CD4+and CD8+T cells in response to HSV-1. These data demonstrated that DCs were essential not only in the optimal activation of the acquired T-cell response to HSV-1 but also that DCs were crucial for innate resistance to HSV-1 infection.