bluuebunny/crossref_metadata_2025 huggingface dataset:
Definition of Five New Simian Immunodeficiency Virus Cytotoxic T-Lymphocyte Epitopes and Their Restricting Major Histocompatibility Complex Class I Molecules: Evidence for an Influence on Disease Progression
Authors: Evans David T. , Jing Peicheng , Allen Todd M. , O'Connor David H. , Horton Helen , Venham John E. , Piekarczyk Marian , Dzuris John , Dykhuzen Marta , Mitchen Jacque , Rudersdorf Richard A. , Pauza C. David , Sette Alessandro , Bontrop Ronald E. , DeMars Robert , Watkins David I.
Published: July 2002

Simian immunodeficiency virus (SIV) infection of the rhesus macaque is currently the best animal model for AIDS vaccine development. One limitation of this model, however, has been the small number of cytotoxic T-lymphocyte (CTL) epitopes and restricting major histocompatibility complex (MHC) class I molecules available for investigating virus-specific CTL responses. To identify new MHC class I-restricted CTL epitopes, we infected five members of a family of MHC-defined rhesus macaques intravenously with SIV. Five new CTL epitopes bound by four different MHC class I molecules were defined. These included two Env epitopes bound by Mamu-A*11 and -B*03 and three Nef epitopes bound by Mamu-B*03, -B*04, and -B*17. All four restricting MHC class I molecules were encoded on only two haplotypes (borc). Interestingly, resistance to disease progression within this family appeared to be associated with the inheritance of one or both of these MHC class I haplotypes. Two individuals that inherited haplotypesbandcseparately survived for 299 and 511 days, respectively, while another individual that inherited both haplotypes survived for 889 days. In contrast, two MHC class I-identical individuals that did not inherit either haplotype rapidly progressed to disease (survived <80 days). Since all five offspring were identical at theirMamu-DRBloci, MHC class II differences are unlikely to account for their patterns of disease progression. These results double the number of SIV CTL epitopes defined in rhesus macaques and provide evidence that allelic differences at the MHC class I loci may influence rates of disease progression among AIDS virus-infected individuals.
Evasion of Host Defenses by Measles Virus: Wild-Type Measles Virus Infection Interferes with Induction of Alpha/Beta Interferon Production
Authors: Naniche Denise , Yeh Annie , Eto Danelle , Manchester Marianne , Friedman Robert M. , Oldstone Michael B. A.
Published: July 2002

Measles is a highly contagious disease currently responsible for over one million childhood deaths, particularly in the developing world. Since alpha/beta interferons (IFNs) are pivotal players both in nonspecific antiviral immunity and in specific cellular responses, their induction or suppression by measles virus (MV) could influence the outcome of a viral infection. In this study we compare the IFN induction and sensitivity of laboratory-passaged attenuated MV strains Edmonston and Moraten with those of recent wild-type viruses isolated and passaged solely on human peripheral blood mononuclear cells (PBMC) or on the B958 marmoset B-cell line. We report that two PBMC-grown wild-type measles isolates and two B958-grown strains of MV induce 10- to 80-fold-lower production of IFN by phytohemagglutinin-stimulated peripheral blood lymphocytes (PBL) compared to Edmonston and Moraten strains of measles. Preinfection of PBL with these non-IFN-inducing MV isolates prevents Edmonston-induced but not double-stranded-RNA-induced IFN production. This suggests that the wild-type viruses can actively inhibit Edmonston-induced IFN synthesis and that this is not occurring by double-stranded RNA. Furthermore, the wild-type MV is more sensitive than Edmonston MV to the effect of IFN. MV is thus able to suppress the synthesis of the earliest mediator of antiviral immunity, IFN-α/β. This could have important implications in the virulence and spread of MV.
Characterization of the Coronavirus M Protein and Nucleocapsid Interaction in Infected Cells
Authors: Narayanan Krishna , Maeda Akihiko , Maeda Junko , Makino Shinji
Published: July 2002

Coronavirus contains three envelope proteins, M, E and S, and a nucleocapsid, which consists of genomic RNA and N protein, within the viral envelope. We studied the macromolecular interactions involved in coronavirus assembly in cells infected with a murine coronavirus, mouse hepatitis virus (MHV). Coimmunoprecipitation analyses demonstrated an interaction between N protein and M protein in infected cells. Pulse-labeling experiments showed that newly synthesized, unglycosylated M protein interacted with N protein in a pre-Golgi compartment, which is part of the MHV budding site. Coimmunoprecipitation analyses further revealed that M protein interacted with only genomic-length MHV mRNA, mRNA 1, while N protein interacted with all MHV mRNAs. These data indicated that M protein interacted with the nucleocapsid, consisting of N protein and mRNA 1, in infected cells. The M protein-nucleocapsid interaction occurred in the absence of S and E proteins. Intracellular M protein-N protein interaction was maintained after removal of viral RNAs by RNase treatment. However, the M protein-N protein interaction did not occur in cells coexpressing M protein and N protein alone. These data indicated that while the M protein-N protein interaction, which is independent of viral RNA, occurred in the M protein-nucleocapsid complex, some MHV function(s) was necessary for the initiation of M protein-nucleocapsid interaction. The M protein-nucleocapsid interaction, which occurred near or at the MHV budding site, most probably represented the process of specific packaging of the MHV genome into MHV particles.
The 60-Residue C-Terminal Region of the Single-Stranded DNA Binding Protein of Herpes Simplex Virus Type 1 Is Required for Cooperative DNA Binding
Authors: Mapelli Marina , Mühleisen Martin , Persico Giorgia , van der Zandt Hans , Tucker Paul A.
Published: July 2002

ICP8 is the major single-stranded DNA (ssDNA) binding protein of the herpes simplex virus type 1 and is required for the onset and maintenance of viral genomic replication. To identify regions responsible for the cooperative binding to ssDNA, several mutants of ICP8 have been characterized. Total reflection X-ray fluorescence experiments on the constructs confirmed the presence of one zinc atom per molecule. Comparative analysis of the mutants by electrophoretic mobility shift assays was done with oligonucleotides for which the number of bases is approximately that occluded by one protein molecule. The analysis indicated that neither removal of the 60-amino-acid C-terminal region nor Cys254Ser and Cys455Ser mutations qualitatively affect the intrinsic DNA binding ability of ICP8. The C-terminal deletion mutants, however, exhibit a total loss of cooperativity on longer ssDNA stretches. This behavior is only slightly modulated by the two-cysteine substitution. Circular dichroism experiments suggest a role for this C-terminal tail in protein stabilization as well as in intermolecular interactions. The results show that the cooperative nature of the ssDNA binding of ICP8 is localized in the 60-residue C-terminal region. Since the anchoring of a C- or N-terminal arm of one protein onto the adjacent one on the DNA strand has been reported for other ssDNA binding proteins, this appears to be the general structural mechanism responsible for the cooperative ssDNA binding by this class of protein.
Bovine Parainfluenza Virus Type 3 (BPIV3) Fusion and Hemagglutinin-Neuraminidase Glycoproteins Make an Important Contribution to the Restricted Replication of BPIV3 in Primates
Authors: Schmidt Alexander C. , McAuliffe Josephine M. , Huang Anne , Surman Sonja R. , Bailly Jane E. , Elkins William R. , Collins Peter L. , Murphy Brian R. , Skiadopoulos Mario H.
Published: July 2002

This study examines the contribution of the fusion (F) and hemagglutinin-neuraminidase (HN) glycoprotein genes of bovine parainfluenza virus type 3 (BPIV3) to its restricted replication in the respiratory tract of nonhuman primates. A chimeric recombinant human parainfluenza type 3 virus (HPIV3) containing BPIV3 F and HN glycoprotein genes in place of its own and the reciprocal recombinant consisting of BPIV3 bearing the HPIV3 F and HN genes (rBPIV3-F
H
HN
H
) were generated to assess the effect of glycoprotein substitution on replication of HPIV3 and BPIV3 in the upper and lower respiratory tract of rhesus monkeys. The chimeric viruses were readily recovered and replicated in simian LLC-MK2 cells to a level comparable to that of their parental viruses, suggesting that the heterologous glycoproteins were compatible with the PIV3 internal proteins. HPIV3 bearing the BPIV3 F and HN genes was restricted in replication in rhesus monkeys to a level similar to that of its BPIV3 parent virus, indicating that the glycoprotein genes of BPIV3 are major determinants of its host range restriction of replication in rhesus monkeys. rBPIV3-F
H
HN
H
replicated in rhesus monkeys to a level intermediate between that of HPIV3 and BPIV3. This observation indicates that the F and HN genes make a significant contribution to the overall attenuation of BPIV3 for rhesus monkeys. Furthermore, it shows that BPIV3 sequences outside the F and HN region also contribute to the attenuation phenotype in primates, a finding consistent with the previous demonstration that the nucleoprotein coding sequence of BPIV3 is a determinant of its attenuation for primates. Despite its restricted replication in the respiratory tract of rhesus monkeys, rBPIV3-F
H
HN
H
conferred a level of protection against challenge with HPIV3 that was indistinguishable from that induced by previous infection with wild-type HPIV3. The usefulness of rBPIV3-F
H
HN
H
as a vaccine candidate against HPIV3 and as a vector for other viral antigens is discussed.
The Nuclear Export Signal within the E4orf6 Protein of Adenovirus Type 5 Supports Virus Replication and Cytoplasmic Accumulation of Viral mRNA
Authors: Weigel Silke , Dobbelstein Matthias
Published: July 2002

During the late phase of adenovirus infection, viral mRNA is efficiently transported from the nucleus to the cytoplasm while most cellular mRNA species are retained in the nucleus. Two viral proteins, E1B-55 kDa and E4orf6, are both necessary for these effects. The E4orf6 protein of adenovirus type 5 binds and relocalizes E1B-55 kDa, and the complex of the two proteins was previously shown to shuttle continuously between the nucleus and cytoplasm. Nucleocytoplasmic transport of the complex is achieved by a nuclear export signal (NES) within E4orf6. Mutation of this signal sequence severely reduces the ability of the E1B-55 kDa–E4orf6 complex to leave the nucleus. Here, we examined the role of functional domains within E4orf6 during virus infection. E4orf6 or mutants derived from it were transiently expressed, followed by infection with recombinant adenovirus lacking the E4 region and determination of virus yield. An arginine-rich putative alpha helix near the carboxy terminus of E4orf6 contributes to E1B-55 kDa binding and relocalization as well as to the synthesis of viral DNA, mRNA, and proteins. Further mutational analysis revealed that mutation of the NES within E4orf6 considerably reduces its ability to support virus production. The same effect was observed when nuclear export was blocked with a competitor. Further, a functional NES within E4orf6 contributed to the efficiency of late virus protein synthesis and viral DNA replication, as well as total and cytoplasmic accumulation of viral late mRNA. Our data support the view that NES-mediated nucleocytoplasmic shuttling strongly enhances most, if not all, intracellular activities of E4orf6 during the late phase of adenovirus infection.
C3H Mouse Mammary Tumor Virus Superantigen Function Requires a Splice Donor Site in the Envelope Gene
Authors: Mustafa Farah , Lozano Mary , Dudley Jaquelin P.
Published: July 2002

Mouse mammary tumor virus (MMTV) encodes a superantigen (Sag) that is required for efficient milk-borne transmission of virus from mothers to offspring. The mRNA used for Sag expression is controversial, and at least four different promoters (two in the long terminal repeat and two in the envelope gene) forsagmRNA have been reported. To determine which RNA is responsible for Sag function during milk-borne MMTV transmission, we mutated a splice donor site unique to a splicedsagRNA from the 5′ envelope promoter. The splice donor mutation in an infectious provirus was transfected into XC cells and injected into BALB/c mice. Mice injected with wild-type provirus showed Sag activity by the deletion of Sag-specific T cells and induction of mammary tumors in 100% of injected animals. However, mice injected with the splice donor mutant gave sporadic and delayed T-cell deletion and a low percentage of mammary tumors with a long latency, suggesting that the resulting tumors were due to the generation of recombinants with endogenous MMTVs. Third-litter offspring of mice injected with wild-type provirus showed Sag-specific T-cell deletion and developed mammary tumors with kinetics similar to those for mice infected by nursing on MMTV-infected mothers, whereas the third-litter offspring of the splice donor mutant-injected mice did not. One of the fifth-litter progeny of splice donor mutant-injected mice showed C3H Sag activity and had recombinants that repaired the splice donor mutation, thus confirming the necessity for the splice donor site for Sag function. These experiments are the first to show that the splicedsagmRNA from the 5′ envelope promoter is required for efficient milk-borne transmission of C3H MMTV.
Global Analysis of Herpes Simplex Virus Type 1 Transcription Using an Oligonucleotide-Based DNA Microarray
Authors: Stingley S. W. , Ramirez J. J. Garcia , Aguilar S. A. , Simmen K. , Sandri-Goldin R. M. , Ghazal P. , Wagner E. K.
Published: July 2002

More than 100 transcripts of various abundances and kinetic classes are expressed during phases of productive and latent infections by herpes simplex virus (HSV) type 1. To carry out rapid global analysis of variations in such patterns as a function of perturbation of viral regulatory genes and cell differentiation, we have made DNA microchips containing sets of 75-mer oligonucleotides specific for individual viral transcripts. About half of these are unique for single transcripts, while others function for overlapping ones. We have also included probes for 57 human genes known to be involved in some aspect of stress response. The chips efficiently detect all viral transcripts, and analysis of those abundant under various conditions of infection demonstrates excellent correlation with known kinetics of mRNA accumulation. Further, quantitative sensitivity is high. We have further applied global analysis of transcription to an investigation of mRNA populations in cells infected with a mutant virus in which the essential immediate-early α27 (UL54) gene has been functionally deleted. Transcripts expressed at 6 h following infection with this mutant can be classified into three groups: those whose abundance is augmented (mainly immediate-early transcripts) or unaltered, those whose abundance is somewhat reduced, and those where there is a significant reduction in transcript levels. These do not conform to any particular kinetic class. Interestingly, levels of many cellular transcripts surveyed are increased. The high proportion of such transcripts suggests that the α27 gene plays a major role in the early decline in cellular gene expression so characteristic of HSV infection.
High Rate of Recombination throughout the Human Immunodeficiency Virus Type 1 Genome
Authors: Jetzt Amanda E. , Yu Hong , Klarmann George J. , Ron Yacov , Preston Bradley D. , Dougherty Joseph P.
Published: July 2002

The diploid nature of human immunodeficiency virus type 1 (HIV-1) indicates that recombination serves a central function in virus replication and evolution. Previously, while examining the nature of obligatory primer strand transfers during reverse transcription, a high rate of recombination was observed at the ends of the viral genome within the viral long terminal repeats, prompting the following question: does recombination occur at a high rate throughout the genome? To address this question, two vectors based upon different strains of HIV-1 were utilized. The vectors were comprised predominantly of autologous HIV-1 sequence and were approximately the same size as the parental genome. The proviral progeny of heterodimeric virions were analyzed after a single cycle of replication, and the sequence heterogeneity between the two strains allowed direct examination of recombination crossovers. The results obtained indicate that HIV-1 undergoes approximately two to three recombination events per genome per replication cycle. These results imply that both HIV-1 RNAs are typically utilized during reverse transcription and that recombination is an important aspect of HIV-1 replication.
An African Swine Fever Virus
ERV1-ALR
Homologue,
9GL
, Affects Virion Maturation and Viral Growth in Macrophages and Viral Virulence in Swine
Authors: Lewis T. , Zsak L. , Burrage T. G. , Lu Z. , Kutish G. F. , Neilan J. G. , Rock D. L.
Published: July 2002

The African swine fever virus (ASFV) genome contains a gene,
9GL
, with similarity to yeast
ERV1
and
ALR
genes.
ERV1
has been shown to function in oxidative phosphorylation and in cell growth, while
ALR
has hepatotrophic activity.
9GL
encodes a protein of 119 amino acids and was highly conserved at both nucleotide and amino acid levels among all ASFV field isolates examined. Monospecific rabbit polyclonal antibody produced to a glutathione
S
-transferase–9GL fusion protein specifically immunoprecipitated a 14-kDa protein from macrophage cell cultures infected with the ASFV isolate Malawi Lil-20/1 (MAL). Time course analysis and viral DNA synthesis inhibitor experiments indicated that p14 was a late viral protein. A
9GL
gene deletion mutant of MAL (Δ9GL), exhibited a growth defect in macrophages of approximately 2 log
10
units and had a small-plaque phenotype compared to either a revertant (9GL-R) or the parental virus. 9GL affected normal virion maturation; virions containing acentric nucleoid structures comprised 90 to 99% of all virions observed in Δ9GL-infected macrophages. The Δ9GL virus was markedly attenuated in swine. In contrast to 9GL-R infection, where mortality was 100%, all Δ9GL-infected animals survived infection. With the exception of a transient fever response in some animals, Δ9GL-infected animals remained clinically normal and exhibited significant 100- to 10,000-fold reductions in viremia titers. All pigs previously infected with Δ9GL survived infection when subsequently challenged with a lethal dose of virulent parental MAL. Thus, ASFV
9GL
gene deletion mutants may prove useful as live-attenuated ASF vaccines.
The Human Cytomegalovirus Major Immediate-Early Distal Enhancer Region Is Required for Efficient Viral Replication and Immediate-Early Gene Expression
Authors: Meier Jeffery L. , Pruessner Jonathan A.
Published: July 2002

The human cytomegalovirus (HCMV) major immediate-early (MIE) genes, encoding IE1 p72 and IE2 p86, are activated by a complex enhancer region (base positions -65 to -550) that operates in a cell type- and differentiation-dependent manner. The expression of MIE genes is required for HCMV replication. Previous studies analyzing functions of MIE promoter-enhancer segments suggest that the distal enhancer region variably modifies MIE promoter activity, depending on cell type, stimuli, or state of differentiation. To further understand the mechanism by which the MIE promoter is regulated, we constructed and analyzed several different recombinant HCMVs that lack the distal enhancer region (-300 to -582, -640, or -1108). In human fibroblasts, the HCMVs without the distal enhancer replicate normally at high multiplicity of infection (MOI) but replicate poorly at low MOI in comparison to wild-type virus (WT) or HCMVs that lack the neighboring upstream unique region and modulator (-582 or -640 to -1108). The growth aberrancy was normalized after restoring the distal enhancer in a virus lacking this region. For HCMVs without a distal enhancer, the impairment in replication at low MOI corresponds to a deficiency in production of MIE RNAs compared to WT or virus lacking the unique region and modulator. An underproduction of viral US3 RNA was also evident at low MOI. Whether lower production of IE1 p72 and IE2 p86 causes a reduction in expression of the immediate-early (IE) class US3 gene remains to be determined. We conclude that the MIE distal enhancer region possesses a mechanism for augmenting viral IE gene expression and genome replication at low MOI, but this regulatory function is unnecessary at high MOI.
Characterization of the Interaction between the Interferon-Induced Protein P56 and the Int6 Protein Encoded by a Locus of Insertion of the Mouse Mammary Tumor Virus
Authors: Guo Jinjiao , Sen Ganes C.
Published: July 2002

For determining cellular functions of the interferon-inducible human cytoplasmic protein P56, we undertook a
Saccharomyces cerevisiae
two-hybrid screen that identified Int6 as a P56-interacting protein. That the interaction also occurs in human cells was confirmed by coimmunoprecipitation and the observed cytoplasmic displacement of nuclear Int6 upon coexpression of P56. Because Int6 has been claimed to be both a cytoplasmic and a nuclear protein, we investigated the structural basis of this discrepancy. By mutational analyses, we showed that the Int6 protein contains a bipartite nuclear localization signal and a nuclear export signal at the far end of the amino terminus. The 20 amino-terminal residues of Int6, when they were attached to a different nuclear protein, were sufficient to translocate that protein to the cytoplasm. Within this region, replacement of any of the three leucine residues with alanine destroyed the function of the export signal. The specific domain of P56 that is required for its interaction with Int6 was mapped using the yeast two-hybrid assay and a mammalian coimmunoprecipitation assay. Both assays demonstrated that the C-terminal region of P56 containing three specific tetratricopeptide motifs is required for this interaction. In contrast, removal of an internal domain of P56 enhanced the interaction, as quantified by the two-hybrid assay.
Roscovitine, a Specific Inhibitor of Cellular Cyclin-Dependent Kinases, Inhibits Herpes Simplex Virus DNA Synthesis in the Presence of Viral Early Proteins
Authors: Schang Luis M. , Rosenberg Amy , Schaffer Priscilla A.
Published: July 2002

We have previously shown that two inhibitors specific for cellular cyclin-dependent kinases (cdks), Roscovitine (Rosco) and Olomoucine (Olo), block the replication of herpes simplex virus (HSV). Based on these results, we demonstrated that HSV replication requires cellular cdks that are sensitive to these drugs (L. M. Schang, J. Phillips, and P. A. Schaffer. J. Virol. 72:5626–5637, 1998). We further established that at least two distinct steps in the viral replication cycle require cdks: transcription of immediate-early (IE) genes and transcription of early (E) genes (L. M. Schang, A. Rosenberg, and P. A. Schaffer, J. Virol. 73:2161–2172, 1999). Since Rosco inhibits HSV replication efficiently even when added to infected cells at 6 h postinfection, we postulated that cdks may also be required for viral functions that occur after E gene expression. In the study presented herein, we tested this hypothesis directly by measuring the efficiency of viral replication, viral DNA synthesis, and expression of several viral genes during infections in which Rosco was added after E proteins had already been synthesized. Rosco inhibited HSV replication, and specifically viral DNA synthesis, when the drug was added at the time of release from a 12-h phosphonoacetic acid (PAA)-induced block in viral DNA synthesis. Inhibition of DNA synthesis was not a consequence of inhibition of expression of IE or E genes in that Rosco had no effect on steady-state levels of two E transcripts under the same conditions in which it inhibited viral DNA synthesis. Moreover, viral DNA synthesis was inhibited by Rosco even in the absence of protein synthesis. In a second series of experiments, the replication of four HSV mutants harboring temperature-sensitive mutations in genes essential for viral DNA replication was inhibited when Rosco was added at the time of shift-down from the nonpermissive to the permissive temperature. Viral DNA synthesis was inhibited by Rosco under these conditions, whereas expression of viral E genes was not affected. We conclude that cellular Rosco-sensitive cdks are required for replication of viral DNA in the presence of viral E proteins. This requirement may indicate that HSV DNA synthesis is functionally linked to transcription, which requires cdks, or that both viral transcription and DNA replication, independently, require viral or cellular factors activated by Rosco-sensitive cdks.
Rotavirus Infection Induces an Increase in Intracellular Calcium Concentration in Human Intestinal Epithelial Cells: Role in Microvillar Actin Alteration
Authors: Brunet Jean-Philippe , Cotte-Laffitte Jacqueline , Linxe Catherine , Quero Anne-Marie , Géniteau-Legendre Monique , Servin Alain
Published: July 2002

Rotaviruses, which infect mature enterocytes of the small intestine, are recognized as the most important cause of viral gastroenteritis in young children. We have previously reported that rotavirus infection induces microvillar F-actin disassembly in human intestinal epithelial Caco-2 cells (N. Jourdan, J. P. Brunet, C. Sapin, A. Blais, J. Cotte-Laffitte, F. Forestier, A. M. Quero, G. Trugnan, and A. L. Servin, J. Virol. 72:7228–7236, 1998). In this study, to determine the mechanism responsible for rotavirus-induced F-actin alteration, we investigated the effect of infection on intracellular calcium concentration ([Ca
2+
]
i
) in Caco-2 cells, since Ca
2+
is known to be a determinant factor for actin cytoskeleton regulation. As measured by quin2 fluorescence, viral replication induced a progressive increase in [Ca
2+
]
i
from 7 h postinfection, which was shown to be necessary and sufficient for microvillar F-actin disassembly. During the first hours of infection, the increase in [Ca
2+
]
i
was related only to an increase in Ca
2+
permeability of plasmalemma. At a late stage of infection, [Ca
2+
]
i
elevation was due to both extracellular Ca
2+
influx and Ca
2+
release from the intracellular organelles, mainly the endoplasmic reticulum (ER). We noted that at this time the [Ca
2+
]
i
increase was partially related to a phospholipase C (PLC)-dependent mechanism, which probably explains the Ca
2+
release from the ER. We also demonstrated for the first time that viral proteins or peptides, released into culture supernatants of rotavirus-infected Caco-2 cells, induced a transient increase in [Ca
2+
]
i
of uninfected Caco-2 cells, by a PLC-dependent efflux of Ca
2+
from the ER and by extracellular Ca
2+
influx. These supernatants induced a Ca
2+
-dependent microvillar F-actin alteration in uninfected Caco-2 cells, thus participating in rotavirus pathogenesis.
Development of an Effective Polyvalent Vaccine against both Marek's and Newcastle Diseases Based on Recombinant Marek's Disease Virus Type 1 in Commercial Chickens with Maternal Antibodies
Authors: Sonoda Kengo , Sakaguchi Masashi , Okamura Hiroshi , Yokogawa Kenji , Tokunaga Eiji , Tokiyoshi Sachio , Kawaguchi Yasushi , Hirai Kanji
Published: July 2002

An earlier report (M. Sakaguchi et al., Vaccine 16:472–479, 1998) showed that recombinant Marek's disease virus type 1 (rMDV1) expressing the fusion (F) protein of Newcastle disease virus (NDV-F) under the control of the simian virus 40 late promoter [rMDV1-US10L(F)] protected specific pathogen-free chickens from NDV challenge, but not commercial chickens with maternal antibodies against NDV and MDV1. In the present study, we constructed an improved polyvalent vaccine based on MDV1 against MDV and NDV in commercial chickens with maternal antibodies. The study can be summarized as follows. (i) We constructed rMDV1 expressing NDV-F under the control of the MDV1 glycoprotein B (gB) promoter [rMDV1-US10P(F)]. (ii) Much less NDV-F protein was expressed in cells infected with rMDV1-US10P(F) than in those infected with rMDV1-US10L(F). (iii) The antibody response against NDV-F and MDV1 antigens of commercial chickens vaccinated with rMDV1-US10P(F) was much stronger and faster than with rMDV1-US10L(F), and a high level of antibody against NDV-F persisted for over 80 weeks postvaccination. (iv) rMDV1-US10P(F) was readily reisolated from the vaccinated chickens, and the recovered viruses were found to express NDV-F. (v) Vaccination of commercial chickens having maternal antibodies to rMDV1-US10P(F) completely protected them from NDV challenge. (vi) rMDV1-US10P(F) offered the same degree of protection against very virulent MDV1 as the parental MDV1 and commercial vaccines. These results indicate that rMDV1-US10P(F) is an effective and stable polyvalent vaccine against both Marek's and Newcastle diseases even in the presence of maternal antibodies.
Evidence for Budding of Human Immunodeficiency Virus Type 1 Selectively from Glycolipid-Enriched Membrane Lipid Rafts
Authors: Nguyen Dzung H. , Hildreth James E. K.
Published: July 2002

A number of recent studies have demonstrated the significance of detergent-insoluble, glycolipid-enriched membrane domains or lipid rafts, especially in regard to activation and signaling in T lymphocytes. These domains can be viewed as floating rafts composed of sphingolipids and cholesterol which sequester glycosylphosphatidylinositol (GPI)-linked proteins, such as Thy-1 and CD59. CD45, a 200-kDa transmembrane phosphatase protein, is excluded from these domains. We have found that human immunodeficiency virus type 1 (HIV-1) particles produced by infected T-cell lines acquire the GPI-linked proteins Thy-1 and CD59, as well as the ganglioside GM1, which is known to partition preferentially into lipid rafts. In contrast, despite its high expression on the cell surface, CD45 was poorly incorporated into virus particles. Confocal fluorescence microscopy revealed that HIV-1 proteins colocalized with Thy-1, CD59, GM1, and a lipid raft-specific fluorescent lipid, DiIC16(3), in uropods of infected Jurkat cells. CD45 did not colocalize with HIV-1 proteins and was excluded from uropods. Dot immunoassay of Triton X-100-extracted membrane fractions revealed that HIV-1 p17 matrix protein and gp41 were present in the detergent-resistant fractions and that [3H]myristic acid-labeled HIV Gag showed a nine-to-one enrichment in lipid rafts. We propose a model for the budding of HIV virions through lipid rafts whereby host cell cholesterol, sphingolipids, and GPI-linked proteins within these domains are incorporated into the viral envelope, perhaps as a result of preferential sorting of HIV Gag to lipid rafts.
Impaired Antiviral Response and Alpha/Beta Interferon Induction in Mice Lacking Beta Interferon
Authors: Deonarain Raj , Alcamí Antonio , Alexiou Maria , Dallman Margaret J. , Gewert Dirk R. , Porter Andrew C. G.
Published: July 2002

We have generated mice lacking the gene for beta interferon and report that they are highly susceptible to vaccinia virus infection. Furthermore, in cultured embryo fibroblasts, viral induction of alpha interferon and of 2-5A synthetase genes is impaired. We also show that beta interferon does not prime its own expression.
Cultured Cell Sublines Highly Susceptible to Prion Infection
Authors: Bosque Patrick J. , Prusiner Stanley B.
Published: July 2002

Cultured cell lines infected with prions produce an abnormal isoform of the prion protein (PrP
Sc
). In order to derive cell lines producing sufficient quantities of PrP
Sc
for most studies, it has been necessary to subclone infected cultures and select the subclones producing the largest amounts of PrP
Sc
. Since postinfection cloning can introduce differences between infected and uninfected cell lines, we sought an approach to generate prion-infected cell lines that would avoid clonal artifacts. Using an improved cell blot technique, which permits sensitive and rapid comparison of PrP
Sc
levels in multiple independent cell cultures, we discovered marked heterogeneity with regard to prion susceptibility in tumor cell sublines. We exploited this heterogeneity to derive sublines which are highly susceptible to prion infection and used these cells to generate prion-infected lines without further subcloning. These infected sublines can be compared to the cognate uninfected cultures without interference from cloning artifacts. We also used susceptible cell lines and our modified cell blot procedure to develop a sensitive and reproducible quantitative cell culture bioassay for prions. We found that the sublines were at least 100-fold more susceptible to strain RML prions than to strain ME7 prions. Comparisons between scrapie-susceptible and -resistant cell lines may reveal factors that modulate prion propagation.
The Human Immunodeficiency Virus Type 1gagGene Encodes an Internal Ribosome Entry Site
Authors: Buck Christopher B. , Shen Xuefei , Egan Michael A. , Pierson Theodore C. , Walker Christopher M. , Siliciano Robert F.
Published: July 2002

Several retroviruses have recently been shown to promote translation of theirgaggene products by internal ribosome entry. In this report, we show that mRNAs containing the human immunodeficiency virus type 1 (HIV-1)gagopen reading frame (ORF) exhibit internal ribosome entry site (IRES) activity that can promote translational initiation of Pr55gag. Remarkably, this IRES activity is driven by sequences within thegagORF itself and is not dependent on the nativegag5′-untranslated region (UTR). This cap-independent mechanism for Pr55gagtranslation may help explain the high levels of translation of this protein in the face of major RNA structural barriers to scanning ribosomes found in thegag5′ UTR. ThegagIRES activity described here also drives translation of a novel 40-kDa Gag isoform through translational initiation at an internal AUG codon found near the amino terminus of the Pr55gagcapsid domain. Our findings suggest that this low-abundance Gag isoform may be important for wild-type replication of HIV-1 in cultured cells. The activities of the HIV-1gagIRES may be an important feature of the HIV-1 life cycle and could serve as a novel target for antiretroviral therapeutic strategies.
Infectious Entry by Amphotropic as well as Ecotropic Murine Leukemia Viruses Occurs through an Endocytic Pathway
Authors: Katen Louis J. , Januszeski Michael M. , Anderson W. French , Hasenkrug Kim J. , Evans Leonard H.
Published: July 2002

Infectious entry of enveloped viruses is thought to proceed by one of two mechanisms. pH-dependent viruses enter the cells by receptor-mediated endocytosis and are inhibited by transient treatment with agents that prevent acidification of vesicles in the endocytic pathway, while pH-independent viruses are not inhibited by such agents and are thought to enter the cell by direct fusion with the plasma membrane. Nearly all retroviruses, including amphotropic murine leukemia virus (MuLV) and human immunodeficiency virus type 1, are classified as pH independent. However, ecotropic MuLV is considered to be a pH-dependent virus. We have examined the infectious entry of ecotropic and amphotropic MuLVs and found that they were equally inhibited by NH
4
Cl and bafilomycin A. These agents inhibited both viruses only partially over the course of the experiments. Agents that block the acidification of endocytic vesicles also arrest vesicular trafficking. Thus, partial inhibition of the MuLVs could be the result of virus inactivation during arrest in this pathway. In support of this contention, we found that that the loss of infectivity of the MuLVs during treatment of target cells with the drugs closely corresponded to the loss of activity due to spontaneous inactivation at 37°C in the same period of time. Furthermore, the drugs had no effect on the efficiency of infection under conditions in which the duration of infection was held to a very short period to minimize the effects of spontaneous inactivation. These results indicate that the infectious processes of both ecotropic and amphotropic MuLVs were arrested rather than aborted by transient treatment of the cells with the drugs. We also found that infectious viruses were efficiently internalized during treatment. This indicated that the arrest occurred in an intracellular compartment and that the infectious process of both the amphotropic and ecotropic MuLVs very likely involved endocytosis. An important aspect of this study pertains to the interpretation of experiments in which agents that block endocytic acidification inhibit infectivity. As we have found with the MuLVs, inhibition of infectivity may be secondary to the block of endocytic acidification. While this strongly suggests the involvement of an endocytic pathway, it does not necessarily indicate a requirement for an acidic compartment during the infectious process. Likewise, a lack of inhibition during transient treatment with the drugs would not preclude an endocytic pathway for viruses that are stable during the course of the treatment.
Efficient Transmission of Two Different Sheep Scrapie Isolates in Transgenic Mice Expressing the Ovine PrP Gene
Authors: Crozet Carole , Flamant Frederic , Bencsik Anna , Aubert Denise , Samarut Jacques , Baron Thierry
Published: July 2002

We produced transgenic mice expressing the sheep prion protein to obtain a sensitive model for sheep spongiform encephalopathies (scrapie). The complete open reading frame, with alanine, arginine, and glutamine at susceptibility codons 136, 154, and 171, respectively, was inserted downstream from the neuron-specific enolase promoter. A mouse line, Tg(OvPrP4), devoid of the murine PrP gene, was obtained by crossing with PrP knockout mice. Tg(OvPrP4) mice were shown to selectively express sheep PrP in their brains, as demonstrated in mRNA and protein analysis. We showed that these mice were susceptible to infection by sheep scrapie following intracerebral inoculation with two natural sheep scrapie isolates, as demonstrated not only by the occurrence of neurological signs but also by the presence of the spongiform changes and abnormal prion protein accumulation in their brains. Mean times to death of 238 and 290 days were observed with these isolates, but the clinical course of the disease was strikingly different in the two cases. One isolate led to a very early onset of neurological signs which could last for prolonged periods before death. Independently of the incubation periods, some of the mice inoculated with this isolate showed low or undetectable levels of PrPsc, as detected by both Western blotting and immunohistochemistry. The development of experimental scrapie in these mice following inoculation of the scrapie infectious agent further confirms that neuronal expression of the PrP open reading frame alone is sufficient to mediate susceptibility to spongiform encephalopathies. More importantly, these mice provide a new and promising tool for studying the infectious agents in sheep spongiform encephalopathies.
The Late Stage of Human Immunodeficiency Virus Type 1 Assembly Is an Energy-Dependent Process
Authors: Tritel Marc , Resh Marilyn D.
Published: July 2002

Several recent studies have indicated the involvement of host cell factors in human immunodeficiency virus type 1 (HIV-1) assembly. To ascertain whether ATP-dependent factors play a role in this process, we quantified virus-like particle (VLP) production by ATP-depleted cells. Pharmacological ATP depletion abrogated VLP production without affecting cell viability or inducing degradation of HIV-1 Gag protein. This effect occurred even when the ATP-depleting agents were added 1 h into the assembly process, and it was reversed by removal of these agents. ATP depletion did not affect Gag membrane binding or multimerization. Density gradient analysis indicated that HIV-1 assembly intermediates were stalled late in the assembly process. This conclusion was further supported by electron microscopy analysis, which revealed a preponderance of plasma membrane-associated stalk-like structures in the ATP-depleted cells. Since no HIV-1 proteins bind or hydrolyze ATP, these findings indicate that an ATP-requiring cellular factor is an obligatory participant late in the HIV-1 assembly process.
Epstein-Barr Virus Immediate-Early Protein BRLF1 Induces the Lytic Form of Viral Replication through a Mechanism Involving Phosphatidylinositol-3 Kinase Activation
Authors: Darr Catherine Dayle , Mauser Amy , Kenney Shannon
Published: July 2002

Expression of the Epstein-Barr virus (EBV) immediate-early (IE) protein BRLF1 induces the lytic form of viral replication in most EBV-positive cell lines. BRLF1 is a transcriptional activator that binds directly to a GC-rich motif present in some EBV lytic gene promoters. However, BRLF1 activates transcription of the other IE protein, BZLF1, through an indirect mechanism which we previously showed to require activation of the stress mitogen-activated protein kinases. Here we demonstrate that BRLF1 activates phosphatidylinositol-3 (PI3) kinase signaling in host cells. We show that the specific PI3 kinase inhibitor, LY294002, completely abrogates the ability of a BRLF1 adenovirus vector to induce the lytic form of EBV infection, while not affecting lytic infection induced by a BZLF1 adenovirus vector. Furthermore, we demonstrate that the requirement for PI3 kinase activation in BRLF1-induced transcriptional activation is promoter dependent. BRLF1 activation of the SM early promoter (which occurs through a direct binding mechanism) does not require PI3 kinase activation, whereas activation of the IE BZLF1 and early BMRF1 promoters requires PI3 kinase activation. Thus, there are clearly two separate mechanisms by which BRLF1 induces transcriptional activation.
Role of the Promyelocytic Leukemia Protein PML in the Interferon Sensitivity of Lymphocytic Choriomeningitis Virus
Authors: Djavani Mahmoud , Rodas Juan , Lukashevich Igor S. , Horejsh Douglas , Pandolfi Pier Paolo , Borden Katherine L. B. , Salvato Maria S.
Published: July 2002

Lymphocytic choriomeningitis virus (LCMV) induces type I interferon (alpha and beta interferon [IFN-α and IFN-β]) upon infection and yet is sensitive to the addition of type II interferon (gamma interferon [IFN-γ]) to the culture media. This sensitivity is biologically important because it correlates inversely with the ability of certain LCMV strains to persist in mice (D. Moskophidis, M. Battegay, M. A. Bruendler, E. Laine, I. Gresser, and R. M. Zinkernagel, J. Virol. 68:1951-1955, 1994). The cellular oncoprotein PML is induced by both IFN-
α
/
β
and IFN-
γ
, and PML binds the LCMV Z protein and becomes redistributed within cells from nucleus to cytoplasm upon LCMV infection. In the present study, increased PML expression results in diminished LCMV replication, implicating PML in the IFN sensitivity of LCMV. Virus production in PML −/− murine embryonic fibroblasts (MEF) exceeds virus production in PML +/+ MEF, and this difference is exacerbated by IFN treatment that upregulates PML expression. IFN-γ also diminishes LCMV production in PML −/− cells; therefore, viral IFN sensitivity is not entirely due to PML. Both viral mRNA production and viral protein production decrease as PML expression increases. Here we propose that PML reduces LCMV transcription through its interaction with the Z protein.
Population Genetic Analysis of the Protease Locus of Human Immunodeficiency Virus Type 1 Quasispecies Undergoing Drug Selection, Using a Denaturing Gradient-Heteroduplex Tracking Assay
Authors: Doukhan Laurence , Delwart Eric
Published: July 2002

Monitoring the evolution of human immunodeficiency virus type 1 (HIV-1) drug resistance requires measuring the frequency of closely related genetic variants making up the complex viral quasispecies found in vivo. In order to resolve both major and minor (≥2%) protease gene variants differing by one or more nucleotide substitutions, we analyzed PCR products derived from plasma viral quasispecies by using a combination of denaturing gradient gel electrophoresis and DNA heteroduplex tracking assays. Correct population sampling of the high level of genetic diversity present within viral quasispecies could be documented by parallel analysis of duplicate, independently generated PCR products. The composition of genetically complex protease gene quasispecies remained constant over short periods of time in the absence of treatment and while plasma viremia fell >100-fold following the initiation of protease inhibitor ritonavir monotherapy. Within a month of initiating therapy, a strong reduction in the genetic diversity of plasma viral populations at the selected protease locus was associated with rising plasma viremia and the emergence of drug resistance. The high levels of protease genetic diversity seen before treatment reemerged only months later. In one patient, reduction in genetic diversity at the protease gene was observed concomitantly with an increase in diversity at the envelope gene (E. L. Delwart, P. Heng, A. Neumann, and M. Markowitz, J. Virol. 72:2416-2421, 1998), indicating that opposite population genetic changes can take place in different HIV-1 loci. The rapid emergence of drug-resistant HIV-1 was therefore associated with a strong, although only transient, reduction in genetic diversity at the selected locus. The denaturing gradient-heteroduplex tracking assay is a simple method for the separation and quantitation of very closely related, low-frequency, genetic variants within complex viral populations.
E Box-Dependent Activation of Telomerase by Human Papillomavirus Type 16 E6 Does Not Require Induction of c-
myc
Authors: Gewin Lindy , Galloway Denise A.
Published: July 2002

Human papillomavirus type 16 (HPV-16) E6 activates telomerase specifically in epithelial cells. The oncogene c-
myc
has also been shown to activate telomerase in several cell types. Here we show that while both HPV-16 E6 and c-
myc
require intact E boxes to transactivate the hTERT promoter, E6 does not induce hTERT transcription simply by inducing expression of c-
myc
. Moreover, hTERT transactivation by HPV-16 E6 correlates with its ability to bind the cellular E6-associated protein (E6AP), suggesting that E6 and E6AP may target a regulator of hTERT expression.
Binding of Human Immunodeficiency Virus Type 1 gp120 to CXCR4 Induces Mitochondrial Transmembrane Depolarization and Cytochromec-Mediated Apoptosis Independently of Fas Signaling
Authors: Roggero Rodolphe , Robert-Hebmann Véronique , Harrington Steve , Roland Joachim , Vergne Laurence , Jaleco Sara , Devaux Christian , Biard-Piechaczyk Martine
Published: July 2002

Apoptosis of CD4+T lymphocytes, induced by contact between human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (gp120) and its receptors, could contribute to the cell depletion observed in HIV-infected individuals. CXCR4 appears to play an important role in gp120-induced cell death, but the mechanisms involved in this apoptotic process remain poorly understood. To get insight into the signal transduction pathways connecting CXCR4 to apoptosis following gp120 binding, we used different cell lines expressing wild-type CXCR4 and a truncated form of CD4 that binds gp120 but lacks the ability to transduce signals. The present study demonstrates that (i) the interaction of cell-associated gp120 with CXCR4-expressing target cells triggers a rapid dissipation of the mitochondrial transmembrane potential resulting in the cytosolic release of cytochromecfrom the mitochondria to cytosol, concurrent with activation of caspase-9 and -3; (ii) this apoptotic process is independent of Fas signaling; and (iii) cooperation with a CD4 signal is not required. In addition, following coculture with cells expressing gp120, a Fas-independent apoptosis involving mitochondria and caspase activation is also observed in primary umbilical cord blood CD4+T lymphocytes expressing high levels of CXCR4. Thus, this gp120-mediated apoptotic pathway may contribute to CD4+T-cell depletion in AIDS.