bluuebunny/crossref_metadata_2025_split huggingface dataset:
Live, Attenuated Simian Immunodeficiency Virus SIVmac-M4, with Point Mutations in the Env Transmembrane Protein Intracytoplasmic Domain, Provides Partial Protection from Mucosal Challenge with Pathogenic SIVmac251
Authors: Shacklett Barbara L. , Shaw Karen E. S. , Adamson Lou A. , Wilkens David T. , Cox Catherine A. , Montefiori David C. , Gardner Murray B. , Sonigo Pierre , Luciw Paul A. 
Published: October 2002

ABSTRACTAttenuated molecular clones of simian immunodeficiency virus (SIVmac) are important tools for studying the correlates of protective immunity to lentivirus infection in nonhuman primates. The most highly attenuated SIVmac mutants fail to induce disease but also fail to induce immune responses capable of protecting macaques from challenge with pathogenic virus. We recently described a novel attenuated virus, SIVmac-M4, containing multiple mutations in the transmembrane protein (TM) intracytoplasmic domain. This domain has been implicated in viral assembly, infectivity, and cytopathogenicity. Whereas parental SIVmac239-Nef+induced persistent viremia and simian AIDS in rhesus macaques, SIVmac-M4 induced transient viremia in juvenile and neonatal macaques, with no disease for at least 1 year postinfection. In this vaccine study, 8 macaques that were infected as juveniles (n= 4) or neonates (n= 4) with SIVmac-M4 were challenged with pathogenic SIVmac251 administered through oral mucosa. At 1 year postchallenge, six of the eight macaques had low to undetectable plasma viremia levels. Assays of cell-mediated immune responses to SIVmac Gag, Pol, Env, and Nef revealed that all animals developed strong CD8+T-cell responses to Gag after challenge but not before. Unvaccinated control animals challenged with SIVmac251 developed persistent viremia, had significantly weaker SIV-specific T-cell responses, and developed AIDS-related symptoms. These findings demonstrate that SIVmac-M4, which contains a full-length Nef coding region and multiple point mutations in the TM, can provide substantial protection from mucosal challenge with pathogenic SIVmac251.
Murine Leukemia Virus Nucleocapsid Mutant Particles Lacking Viral RNA Encapsidate Ribosomes
Authors: Muriaux Delphine , Mirro Jane , Nagashima Kunio , Harvin Demetria , Rein Alan 
Published: October 2002

ABSTRACT

A single retroviral protein, termed Gag, is sufficient for assembly of retrovirus-like particles in mammalian cells. Gag normally selects the genomic RNA of the virus with high specificity; the nucleocapsid (NC) domain of Gag plays a crucial role in this selection process. However, encapsidation of the viral RNA is completely unnecessary for particle assembly. We previously showed that mutant murine leukemia virus (MuLV) particles that lack viral RNA because of a deletion in the
cis
-acting packaging signal (“Ψ”) in the genomic RNA compensate for the loss of the viral RNA by incorporating cellular mRNA. The RNA in wild-type and Ψ− particles was also found to be necessary for virion core structure. In the present work, we explored the role of RNA in MuLV particles that lack genomic RNA because of mutations in the NC domain of Gag. Using a fluorescent dye assay, we observed that NC mutant particles contain the same amount of RNA that wild-type virions do. Surprisingly enough, these particles contained large amounts of rRNAs. Furthermore, ribosomal proteins were detected by immunoblotting, and ribosomes were observed inside the particles by electron microscopy. The biological significance of the presence of ribosomes in NC mutant particles lacking genomic RNA is discussed.
Reovirus-Induced Apoptosis Requires Mitochondrial Release of Smac/DIABLO and Involves Reduction of Cellular Inhibitor of Apoptosis Protein Levels
Authors: Kominsky Douglas J. , Bickel Ryan J. , Tyler Kenneth L. 
Published: October 2002

ABSTRACT

Many viruses belonging to diverse viral families with differing structure and replication strategies induce apoptosis both in cultured cells in vitro and in tissues in vivo
.
Despite this fact, little is known about the specific cellular apoptotic pathways induced during viral infection. We have previously shown that reovirus-induced apoptosis of HEK cells is initiated by death receptor activation but requires augmentation by mitochondrial apoptotic pathways for its maximal expression. We now show that reovirus infection of HEK cells is associated with selective cytosolic release of the mitochondrial proapoptotic factors cytochrome
c
and Smac/DIABLO, but not the release of apoptosis-inducing factor. Release of these factors is not associated with loss of mitochondrial transmembrane potential and is blocked by overexpression of Bcl-2. Stable expression of caspase-9b, a dominant-negative form of caspase-9, blocks reovirus-induced caspase-9 activation but fails to significantly reduce activation of the key effector caspase, caspase-3. Smac/DIABLO enhances apoptosis through its action on cellular inhibitor of apoptosis proteins (IAPs). Reovirus infection is associated with selective down-regulation of cellular IAPs, including c-IAP1, XIAP, and survivin, effects that are blocked by Bcl-2 expression, establishing the dependence of IAP down-regulation on mitochondrial events. Taken together, these results are consistent with a model in which Smac/DIABLO-mediated inhibition of IAPs, rather than cytochrome
c-
mediated activation of caspase-9, is the key event responsible for mitochondrial augmentation of reovirus-induced apoptosis. These studies provide the first evidence for the association of Smac/DIABLO with virus-induced apoptosis.
Stable Expression of Primary Human Immunodeficiency Virus Type 1 Structural Gene Products by Use of a Noncytopathic Sindbis Virus Vector
Authors: Kong Wei , Tian Chunjuan , Liu Bindong , Yu Xiao-Fang 
Published: October 2002

ABSTRACTEfficient expression of the human immunodeficiency virus type 1 (HIV-1) structural gene products Gag, Pol, and Env involves the regulation by viral Rev and Rev-responsive elements (RRE). Removal of multiple inhibitory sequences (INS) in the coding regions of these structural genes or modification of the codon usage patterns of HIV-1 genes to those used by highly expressed human genes has been found to significantly increase HIV-1 structural protein expression in the absence of Rev and RRE. In this study, we show that efficient and stable expression of the HIV-1 structural gene products Gag and Env could be achieved by transfection with a noncytopathic Sindbis virus expression vector by using HIV-1 sequences from primary isolates without any sequence modification. Stable expression of these Gag and Env proteins was observed for more than 12 months. The fact that the Sindbis virus expression vector replicates its RNA only in the cytoplasm of the transfected cells and the fact that the lack of expression of HIV-1 Gag by the DNA vector containing unmodified HIV-1gagsequences was associated with a lack of detectable cytoplasmicgagRNA suggest that a major blockage in the expression of HIV-1 structural proteins in the absence of Rev/RRE is caused by inefficient accumulation of mRNA in the cytoplasm. Efficient long-term expression of structural proteins of diverse HIV-1 strains by the noncytopathic Sindbis virus expression system may be a useful tool for functional study of HIV-1 gene products and vaccine research.
Inhibition of Endosomal/Lysosomal Degradation Increases the Infectivity of Human Immunodeficiency Virus
Authors: Fredericksen Brenda L. , Wei Bangdong L. , Yao Jian , Luo Tianci , Garcia J. Victor 
Published: October 2002

ABSTRACTProductive entry of human immunodeficiency virus type 1 (HIV-1) into a host cell is believed to proceed via fusion of the viral envelope with the host cell's plasma membrane. Interestingly, the majority of HIV-1 particles that bind to the cell surface are taken up by the host cell via endocytosis; however, this mode of internalization generally does not result in infection. Presumably, virus particles remain trapped in the endocytic pathway and are eventually degraded. Here, we demonstrate that treatment of cells with various pharmacological agents known to elevate the pH of endosomes and lysosomes allows HIV-1 to efficiently enter and infect the host cell. Pretreatment of cells with bafilomycin A1 results in up to a 50-fold increase in the infectivity of HIV-1SF2. Similarly, pretreatment of target cells with amantadine, concanamycin A, concanamycin B, chloroquine, and ammonium chloride resulted in increases in HIV-1 infectivity ranging between 2- and 15-fold. Analysis of receptor and coreceptor expression, HIV-long terminal repeat (LTR) transactivation, and transduction with amphotropic-pseudotyped murine leukemia virus (MLV)-based vectors suggests that the increase in infectivity is not artifactual. The increased infectivity under these conditions appears to be due to the ability of HIV-1 and MLV particles to enter via the endocytic pathway when spared from degradation in the late endosomes and lysosomes. These results could have significant implications for the administration of current and future lysosmotropic agents to patients with HIV disease.
Comparison of the Complete DNA Sequences of the Oka Varicella Vaccine and Its Parental Virus
Authors: Gomi Yasuyuki , Sunamachi Hiroki , Mori Yasuko , Nagaike Kazuhiro , Takahashi Michiaki , Yamanishi Koichi 
Published: October 2002

ABSTRACT
The DNA sequences of the Oka varicella vaccine virus (V-Oka) and its parental virus (P-Oka) were completed. Comparison of the sequences revealed 42 base substitutions, which led to 20 amino acid conversions and length differences in tandem repeat regions (R1, R3, and R4) and in an origin of DNA replication. Amino acid substitutions existed in open reading frames (ORFs) 6, 9A, 10, 21, 31, 39, 50, 52, 55, 59, 62, and 64. Of these, 15 base substitutions, leading to eight amino acid substitutions, were in the gene 62 region alone. Further DNA sequence analysis showed that these substitutions were specific for V-Oka and were not present in nine clinical isolates. The immediate-early gene 62 product (IE62) of P-Oka had stronger transactivational activity than the mutant IE62 contained in V-Oka in 293 and CV-1 cells. An infectious center assay of a plaque-purified clone (S7-01) from the V-Oka with 8 amino acid substitutions in ORF 62 showed smaller plaque formation and less-efficient virus-spreading activity than did P-Oka in human embryonic lung cells. Another clone (S-13) with only five substitutions in ORF 62 spread slightly faster than S7-01 but not as effectively as P-Oka. Moreover, transient luciferase assay in 293 cells showed that transactivational activities of IE62s of S7-01 and S7-13 were lower than that of P-Oka. Based on these results, it appears that amino acid substitutions in ORF 62 are responsible for virus growth and spreading from infected to uninfected cells. Furthermore, the Oka vaccine virus was completely distinguishable from P-Oka and 54 clinical isolates by seven restriction-enzyme fragment length polymorphisms that detected differences in the DNA sequence.
Antibody to a Lytic Cycle Viral Protein Decreases Gammaherpesvirus Latency in B-Cell-Deficient Mice
Authors: Gangappa Shivaprakash , Kapadia Sharookh B. , Speck Samuel H. , Virgin Herbert W. 
Published: October 2002

ABSTRACTWhile antiviral antibody plays a key role in resistance to acute viral infection, the contribution of antibody to the control of latent virus infection is less well understood. Gammaherpesvirus 68 (γHV68) infection of mice provides a model well suited to defining contributions of specific immune system components to the control of viral latency. B cells play a critical role in regulating γHV68 latency, but the mechanism(s) by which B cells regulate latency is not known. In the experiments reported here, we determined the effect of passively transferred antibody on established γHV68 latency in B-cell-deficient (B-cell−/−) mice. Immune antibody decreased the frequency of cells reactivating ex vivo from latency in splenocytes (>10-fold) and peritoneal cells (>100-fold) and the frequency of cells carrying latent viral genome in splenocytes (>5-fold) and peritoneal cells (>50-fold). This effect required virus-specific antibody and was observed when total and virus-specific serum antibody concentrations in recipient B-cell−/−mice were <8% of those in normal mice during latent infection. Passive transfer of antibody specific for the lytic cycle γHV68 RCA protein, but not passive transfer of antibody specific for the v-cyclin protein or the latent protein M2, decreased both the frequency of cells reactivating ex vivo from latency and the frequency of cells carrying the latent viral genome. Therefore, antibody specific for lytic cycle viral antigens can play an important role in the control of gammaherpesvirus latency in immunocompromised hosts. Based on these findings, we propose a model in which ongoing productive replication is essential for maintaining high levels of latently infected cells in immunocompromised hosts. We confirmed this model by the treatment of latently infected B-cell−/−mice with the antiviral drug cidofovir.
Truncated Forms of Glycoprotein D of Herpes Simplex Virus 1 Capable of Blocking Apoptosis and of Low-Efficiency Entry into Cells Form a Heterodimer Dependent on the Presence of a Cysteine Located in the Shared Transmembrane Domains
Authors: Zhou Guoying , Roizman Bernard 
Published: October 2002

ABSTRACT

Earlier studies have shown that herpes simplex virus 1 (HSV-1) virions of mutant lacking glycoprotein D (gD) and made in either complementing (gD
−/+
stocks) or noncomplementing cells (gD
−/−
stocks) induce apoptosis. Subsequent studies have shown that apoptosis induced by gD
−/−
mutant virus stocks can be blocked by in
trans
delivery of viral genes that encode either intact gD or a mixture of two genes encoding the glycoprotein ectodomain plus transmembrane domain (gD-B) and transmembrane domain plus the cytoplasmic carboxyl terminus of the protein (gD-D), respectively. Since the presence of the transmembrane domains was critical for precluding apoptosis in the bipartite system, the question arose whether the two components, gD-B and gD-D, form a heterodimer mediated by an unpaired cysteine located in the transmembrane domain. We report the following. (i) The substitution of the unpaired cysteine with serine in either gD-B or gD-D truncated forms of gD disabled the ability of gD-D and gD-B to block apoptosis. (ii) Immunoprecipitation of gD-D coprecipitated gD-B only from lysates of cells transduced with gD-D and gD-B containing the cysteine in the transmembrane domains. Replacement of cysteine with serine ablated coprecipitation of the components. (ii) The mixture of gD-D and gD-B complemented at a low level gD
−/+
virions. We conclude that the gD-B and gD-D can form a heterodimer dependent on the presence of cysteines in the transmembrane domain and the heterodimer can substitute for intact gD but at a much reduced efficiency.
Nipah Virus V Protein Evades Alpha and Gamma Interferons by Preventing STAT1 and STAT2 Activation and Nuclear Accumulation
Authors: Rodriguez Jason J. , Parisien Jean-Patrick , Horvath Curt M. 
Published: October 2002

ABSTRACT

Characterization of recent outbreaks of fatal encephalitis in southeast Asia identified the causative agent to be a previously unrecognized enveloped negative-strand RNA virus of the
Paramyxoviridae
family, Nipah virus. One feature linking Nipah virus to this family is a conserved cysteine-rich domain that is the hallmark of paramyxovirus V proteins. The V proteins of other paramyxovirus species have been linked with evasion of host cell interferon (IFN) signal transduction and subsequent antiviral responses by inducing proteasomal degradation of the IFN-responsive transcription factors, STAT1 or STAT2. Here we demonstrate that Nipah virus V protein escapes IFN by a distinct mechanism involving direct inhibition of STAT protein function. Nipah virus V protein differs from other paramyxovirus V proteins in its subcellular distribution but not in its ability to inhibit cellular IFN responses. Nipah virus V protein does not induce STAT degradation but instead inhibits IFN responses by forming high-molecular-weight complexes with both STAT1 and STAT2. We demonstrate that Nipah virus V protein accumulates in the cytoplasm by a Crm1-dependent mechanism, alters the STAT protein subcellular distribution in the steady state, and prevents IFN-stimulated STAT redistribution. Consistent with the formation of complexes, STAT protein tyrosine phosphorylation is inhibited in cells expressing the Nipah virus V protein. As a result, Nipah virus V protein efficiently prevents STAT1 and STAT2 nuclear translocation in response to IFN, inhibiting cellular responses to both IFN-α and IFN-γ.
Kaposi's Sarcoma-Associated Herpesvirus Mitochondrial K7 Protein Targets a Cellular Calcium-Modulating Cyclophilin Ligand To Modulate Intracellular Calcium Concentration and Inhibit Apoptosis
Authors: Feng Pinghui , Park Junsoo , Lee Bok-Soo , Lee Sun-Hwa , Bram Richard J. , Jung Jae U. 
Published: October 2002

ABSTRACTOn viral infection, infected cells can become the target of host immune responses or can go through a programmed cell death process, called apoptosis, as a defense mechanism to limit the ability of the virus to replicate. To prevent this, viruses have evolved elaborate mechanisms to subvert the apoptotic process. Here, we report the identification of a novel antiapoptotic K7 protein of Kaposi's sarcoma-associated herpesvirus (KSHV) which expresses during lytic replication. The KSHV K7 gene encodes a small mitochondrial membrane protein, and its expression efficiently inhibits apoptosis induced by a variety of apoptogenic agents. The yeast two-hybrid screen has demonstrated that K7 targets cellular calcium-modulating cyclophilin ligand (CAML), a protein that regulates the intracellular Ca2+concentration. Similar to CAML, K7 expression significantly enhances the kinetics and amplitudes of the increase in intracellular Ca2+concentration on apoptotic stimulus. Mutational analysis showed that K7 interaction with CAML is required for its function in the inhibition of apoptosis. This indicates that K7 targets cellular CAML to increase the cytosolic Ca2+response, which consequently protects cells from mitochondrial damage and apoptosis. This is a novel viral antiapoptosis strategy where the KSHV mitochondrial K7 protein targets a cellular Ca2+-modulating protein to confer resistance to apoptosis, which allows completion of the viral lytic replication and, eventually, maintenance of persistent infection in infected host.
Generation of a Replication-Competent, Propagation-Deficient Virus Vector Based on the Transmissible Gastroenteritis Coronavirus Genome
Authors: Ortego Javier , Escors David , Laude Hubert , Enjuanes Luis 
Published: October 2002

ABSTRACT

Replication-competent propagation-deficient virus vectors based on the transmissible gastroenteritis coronavirus (TGEV) genome that are deficient in the essential E gene have been developed by complementation within E
+
packaging cell lines. Cell lines expressing the TGEV E protein were established using the noncytopathic Sindbis virus replicon pSINrep21. In addition, cell lines stably expressing the E gene under the CMV promoter have been developed. The Sindbis replicon vector and the ectopic TGEV E protein did not interfere with the rescue of infectious TGEV from full-length cDNA. Recombinant TGEV deficient in the nonessential 3a and 3b genes and the essential E gene (rTGEV-Δ3abΔE) was successfully rescued in these cell lines. rTGEV-Δ3abΔE reached high titers (10
7
PFU/ml) in baby hamster kidney cells expressing porcine aminopeptidase N (BHK-pAPN), the cellular receptor for TGEV, using Sindbis replicon and reached titers up to 5 × 10
5
PFU/ml in cells stably expressing E protein under the control of the CMV promoter. The virus titers were proportional to the E protein expression level. The rTGEV-Δ3abΔE virions produced in the packaging cell line showed the same morphology and stability under different pHs and temperatures as virus derived from the full-length rTGEV genome, although a delay in virus assembly was observed by electron microscopy and virus titration in the complementation system in relation to the wild-type virus. These viruses were stably grown for >10 passages in the E
+
packaging cell lines. The availability of packaging cell lines will significantly facilitate the production of safe TGEV-derived vectors for vaccination and possibly gene therapy.
LMP-1's Transmembrane Domains Encode Multiple Functions Required for LMP-1's Efficient Signaling
Authors: Kaykas Ajamete , Worringer Kathleen , Sugden Bill 
Published: October 2002

ABSTRACTThe latent membrane protein-1 (LMP-1) of Epstein-Barr virus (EBV) contributes to the proliferation of infected B lymphocytes by signaling through its binding to cellular signaling molecules. It apparently mimics members of the tumor necrosis factor receptor family, in particular, CD40, by binding a similar set of cellular molecules as does CD40. LMP-1 differs dramatically in its structure from CD40. LMP-1 has six membrane-spanning domains as opposed to CD40's one. LMP-1 also differs from CD40 in its apparent independence of a ligand for its signaling. We have examined the role of LMP-1's membrane-spanning domains in its signaling. Their substitution with six membrane-spanning domains from the LMP-2A protein of EBV yields a derivative which neither coimmunoprecipitates with LMP-1 nor signals to increase the activity of NF-κB as does wild-type LMP-1. These observations indicate that LMP-1 has specific sequences in its membrane-spanning domains required for these activities. LMP-1's first and sixth membrane-spanning domains have multiple leucine residues potentially similar to leucine-heptad motifs that can mediate protein-protein interactions in membranes (Gurezka et al., J. Biol. Chem. 274:9265-9270, 1999). Substitution of seven leucines in LMP-1's sixth membrane-spanning domain has no effect on its function, whereas similar substitutions in its first membrane-spanning domain yielded a derivative which aggregates as does wild-type LMP-1 but has only 3% of wild-type's ability to signal through NF-κB. Importantly, this derivative complements a mutant of LMP-1 with wild-type membrane-spanning domains but no carboxy-terminal signaling domain. These findings together indicate that the membrane-spanning domains of LMP-1 contribute multiple functions to its signaling.
Interleukin-8 and Growth-Regulated Oncogene Alpha Mediate Angiogenesis in Kaposi's Sarcoma
Authors: Lane Brian R. , Liu Jianguo , Bock Paul J. , Schols Dominique , Coffey Michael J. , Strieter Robert M. , Polverini Peter J. , Markovitz David M. 
Published: October 2002

ABSTRACTThe development of the complex neoplasm Kaposi's sarcoma is dependent on infection with the Kaposi's sarcoma-associated herpesvirus (KSHV) and appears to be greatly enhanced by cytokines and human immunodeficiency virus type 1 (HIV-1) Tat. Interleukin-8 (IL-8) and growth-regulated oncogene alpha (GRO-α) are chemokines involved in chemoattraction, neovascularization, and stimulation of HIV-1 replication. We have previously demonstrated that production of GRO-α is stimulated by exposure of monocyte-derived macrophages (MDM) to HIV-1. Here we show that exposure of MDM to HIV-1, viral Tat, or viral gp120 leads to a substantial increase in IL-8 production. We also demonstrate that IL-8 and GRO-α are induced by KSHV infection of endothelial cells and are crucial to the angiogenic phenotype developed by KSHV-infected endothelial cells in cell culture and upon implantation into SCID mice. Thus, the three known etiological factors in Kaposi's sarcoma pathogenesis—KSHV, HIV-1 Tat, and cellular growth factors—might be linked, in part, through induction of IL-8 and GRO-α.