bluuebunny/crossref_metadata_2025_split huggingface dataset:
Loss of G
1
/S Checkpoint in Human Immunodeficiency Virus Type 1-Infected Cells Is Associated with a Lack of Cyclin-Dependent Kinase Inhibitor p21/Waf1
Authors: Clark Elizabeth , Santiago Francisco , Deng Longwen , Chong Siew yen , de la Fuente Cynthia , Wang Lai , Fu Peng , Stein Dana , Denny Thomas , Lanka Venkata , Mozafari Fariba , Okamoto Takashi , Kashanchi Fatah 
Published: July 2002

ABSTRACT

Productive high-titer infection by human immunodeficiency virus type 1 (HIV-1) requires the activation of target cells. Infection of quiescent peripheral CD4 lymphocytes by HIV-1 results in incomplete, labile reverse transcripts and lack of viral progeny formation. An interplay between Tat and p53 has previously been reported, where Tat inhibited the transcription of the p53 gene, which may aid in the development of AIDS-related malignancies, and p53 expression inhibited HIV-1 long terminal repeat transcription. Here, by using a well-defined and -characterized stress signal, gamma irradiation, we find that upon gamma irradiation, HIV-1-infected cells lose their G
1
/S checkpoints, enter the S phase inappropriately, and eventually apoptose. The loss of the G
1
/S checkpoint is associated with a loss of p21/Waf1 protein and increased activity of a major G
1
/S kinase, namely, cyclin E/cdk2. The p21/Waf1 protein, a known cyclin-dependent kinase inhibitor, interacts with the cdk2/cyclin E complex and inhibits progression of cells into S phase. We find that loss of the G
1
/S checkpoint in HIV-1-infected cells may in part be due to Tat's ability to bind p53 (a known activator of the p21/Waf1 promoter) and sequester its transactivation activity, as seen in both in vivo and in vitro transcription assays. The loss of p21/Waf1 in HIV-1-infected cells was specific to p21/Waf1 and did not occur with other KIP family members, such as p27 (KIP1) and p57 (KIP2). Finally, the advantage of a loss of the G
1
/S checkpoint for HIV-1 per se may be that it pushes the host cell into the S phase, which may then allow subsequent virus-associated processes, such as RNA splicing, transport, translation, and packaging of virion-specific genes, to occur.
Characterization and Construction of Functional cDNA Clones of Pariacoto Virus, the First
Alphanodavirus
Isolated outside Australasia
Authors: Johnson Karyn N. , Zeddam Jean-Louis , Ball L. Andrew 
Published: July 2002

ABSTRACT

Pariacoto virus (PaV) was recently isolated in Peru from the Southern armyworm (
Spodoptera eridania
). PaV particles are isometric, nonenveloped, and about 30 nm in diameter. The virus has a bipartite RNA genome and a single major capsid protein with a molecular mass of 39.0 kDa, features that support its classification as a
Nodavirus
. As such, PaV is the first
Alphanodavirus
to have been isolated from outside Australasia. Here we report that PaV replicates in wax moth larvae and that PaV genomic RNAs replicate when transfected into cultured baby hamster kidney cells. The complete nucleotide sequences of both segments of the bipartite RNA genome were determined. The larger genome segment, RNA1, is 3,011 nucleotides long and contains a 973-amino-acid open reading frame (ORF) encoding protein A, the viral contribution to the RNA replicase. During replication, a 414-nucleotide long subgenomic RNA (RNA3) is synthesized which is coterminal with the 3′ end of RNA1. RNA3 contains a small ORF which could encode a protein of 90 amino acids similar to the B2 protein of other alphanodaviruses. RNA2 contains 1,311 nucleotides and encodes the 401 amino acids of the capsid protein precursor α. The amino acid sequences of the PaV capsid protein and the replicase subunit share 41 and 26% identity with homologous proteins of
Flock house virus
, the best characterized of the alphanodaviruses. These and other sequence comparisons indicate that PaV is evolutionarily the most distant of the alphanodaviruses described to date, consistent with its novel geographic origin. Although the PaV capsid precursor is cleaved into the two mature capsid proteins β and γ, the amino acid sequence at the cleavage site, which is Asn/Ala in all other alphanodaviruses, is Asn/Ser in PaV. To facilitate the investigation of PaV replication in cultured cells, we constructed plasmids that transcribed full-length PaV RNAs with authentic 5′ and 3′ termini. Transcription of these plasmids in cells recreated the replication of PaV RNA1 and RNA2, synthesis of subgenomic RNA3, and translation of viral proteins A and α.
Yin Yang 1 Negatively Regulates the Differentiation-Specific E1 Promoter of Human Papillomavirus Type 6
Authors: Ai Wandong , Narahari Janaki , Roman Ann 
Published: July 2002

ABSTRACT

Human papillomavirus type 6 (HPV-6) is a low-risk HPV whose replication cycle, like that of all HPVs, is differentiation dependent. We have previously shown that CCAAT displacement protein (CDP) binds the differentiation-induced HPV-6 E1 promoter and negatively regulates its activity in undifferentiated cells (W. Ai, E. Toussaint, and A. Roman, J. Virol. 73:4220–4229, 1999). Using electrophoretic mobility shift assays (EMSAs), we now report that Yin Yang 1 (YY1), a multifunctional protein that can act as a transcriptional activator or repressor and that can also inhibit HPV replication in vitro, binds the HPV-6 E1 promoter. EMSAs, using subfragments of the promoter as competitors, showed that the YY1 binding site is located at the 5′ end of the E1 promoter. When a putative YY1 site was mutated, the ability of YY1 to bind was greatly decreased. The activity of the mutated E1 promoter, monitored with the reporter gene
luciferase
, was threefold greater than that of the wild-type promoter, suggesting that YY1 negatively regulates HPV-6 E1 promoter activity. Nuclear extracts from differentiated keratinocytes showed decreased binding of YY1 to the wild-type promoter. Consistent with this, in differentiated keratinocytes, the activity of the transfected
luciferase
gene transcribed from the mutated promoter was comparable to that of the wild-type promoter; both promoters were up-regulated in differentiated keratinocytes compared to undifferentiated cells. These data suggest that YY1 functions in undifferentiated keratinocytes but not in differentiated keratinocytes. Both the wild-type and mutated promoters could be negatively regulated by overexpression of a plasmid encoding CDP. Thus, both YY1 and CDP appear to be negative regulators of the differentiation-induced HPV-6 E1 promoter and thereby the HPV life cycle. In contrast, only binding of CDP was detected using the E1 promoter of the high-risk HPV-31.
Protective Immunity to Rotavirus Shedding in the Absence of Interleukin-6: Th1 Cells and Immunoglobulin A Develop Normally
Authors: VanCott John L. , Franco Manuel A. , Greenberg Harry B. , Sabbaj Steffanie , Tang Baozhing , Murray Richard , McGhee Jerry R. 
Published: July 2002

ABSTRACTWe investigated whether interleukin-6 (IL-6) was required for the development of immunoglobulin A (IgA)- and T-helper 1 (Th1)-associated protective immune responses to rotavirus by using adult IL-6-deficient mice [BALB/c and (C57BL/6 × O1a)F2backgrounds]. Naive IL-6−mice had normal frequencies of IgA plasma cells in the gastrointestinal tract. Consistent with this, total levels of IgA in fecal extracts, saliva, and sera were unaltered. In specific response to oral infection with rhesus rotavirus, IL-6−and IL-6+mice exhibited efficient Th1-type gamma interferon responses in Peyer's patches with high levels of serum IgG2a and intestinal IgA. Although there was an increase in Th2-type IL-4 in CD4+T cells from IL-6−mice following restimulation with rotavirus antigen in the presence of irradiated antigen-presenting cells, unfractionated Peyer's patch cells failed to produce a significant increase in IL-4. Moreover, virus-specific IgG1 in serum was not significantly increased in IL-6−mice in comparison with IL-6+mice. Following oral inoculation with murine rotavirus, IL-6−and IL-6+mice mediated clearance of rotavirus and mounted a strong IgA response. When IL-6−and IL-6+mice [(C57BL/6 × O1a)F2background] were orally inoculated with rhesus rotavirus and later challenged with murine rotavirus, all of the mice maintained high levels of IgA in feces and were protected against reinfection. Thus, IL-6 failed to provide unique functions in the development of IgA-secreting B cells and in the establishment of Th1-associated protective immunity against rotavirus infection in adult mice.
Persistence and Reactivation of Bovine Herpesvirus 1 in the Tonsils of Latently Infected Calves
Authors: Winkler M. T. C. , Doster A. , Jones C. 
Published: July 2002

ABSTRACTBovine herpesvirus 1 (BHV-1), like other members of theAlphaherpesvirinaesubfamily, establishes latent infection in sensory neurons. Reactivation from latency can occur after natural or corticosteroid-induced stress culminating in recurrent disease and/or virus transmission to uninfected animals. Our previous results concluded that CD4+T cells in the tonsil and other adjacent lymph nodes are infected and undergo apoptosis during acute infection (M. T. Winkler, A. Doster, and C. Jones, J. Virol. 73:8657–8668, 1999). To test whether BHV-1 persisted in lymphoreticular tissue, we analyzed tonsils of latently infected calves for the presence of viral DNA and gene expression. BHV-1 DNA was consistently detected in the tonsils of latently infected calves. Detection of the latency-related transcript (LRT) in tonsils of latently infected calves required nested reverse transcription-PCR (RT-PCR) suggesting that only a few cells contained viral DNA or that LRT is not an abundant transcript. bICP0 (immediate-early and early transcripts), ribonucleotide reductase (early transcript), and glycoprotein C (late transcript) were not detected by RT-PCR in latently infected calves. When reactivation was initiated by dexamethasone, bICP0 and ribonucleotide reductase transcripts were detected. Following dexamethasone treatment, viral nucleic acid was detected simultaneously in trigeminal ganglionic neurons and lymphoid follicles of tonsil. LRT was detected at 6 and 24 h after dexamethasone treatment but not at 48 h. Dexamethasone-induced reactivation led to apoptosis that was localized to tonsillar lymphoid follicles. Taken together, these findings suggest that the tonsil is a site for persistence or latency from which virus can be reactivated by dexamethasone. We further hypothesize that the shedding of virus from the tonsil during reactivation plays a role in virus transmission.
Human Immunodeficiency Virus Type 1 Coreceptor Preferences Determine Target T-Cell Depletion and Cellular Tropism in Human Lymphoid Tissue
Authors: Grivel Jean-Charles , Penn Michael L. , Eckstein Daniel A. , Schramm Birgit , Speck Roberto F. , Abbey Nancy W. , Herndier Brian , Margolis Leonid , Goldsmith Mark A. 
Published: July 2002

ABSTRACT

The present study sought to determine how usage of coreceptors by human immunodeficiency virus type 1 dictates cell tropism and depletion of CD4
+
T cells in human lymphoid tissues cultured ex vivo. We found that coreceptor preferences control the marked, preferential depletion of coreceptor-expressing CD4
+
lymphocytes. In addition, there was a strong, but not absolute, preference shown by CXCR4-using strains for lymphocytes and by CCR5-using strains for macrophages.
Evaluation of a Neonatal Rat Model for Prediction of Mumps Virus Neurovirulence in Humans
Authors: Rubin Steven A. , Pletnikov Mikhail , Taffs Rolf , Snoy Phil J. , Kobasa Darwyn , Brown Earl G. , Wright Kathryn E. , Carbone Kathryn M. 
Published: July 2002

ABSTRACTNeurovirulence of several mumps virus strains was assessed in a prototype rat neurovirulence test and compared to results obtained in the monkey neurovirulence test. The relative human neurovirulence of these strains was proportional to the severity of hydrocephalus in rats but not to lesion scores in the monkeys.
Estimating Relative Fitness in Viral Competition Experiments
Authors: Marée Athanasius F. M. , Keulen Wilco , Boucher Charles A. B. , De Boer Rob J. 
Published: July 2002

ABSTRACT

The relative fitness of viral variants has previously been defined as the slope of the logarithmic ratio of the genotype or phenotype frequencies in time plots of pairwise competition experiments. Developing mathematical models for such experiments by employing the conventional coefficient of selection
s
, we demonstrate that this logarithmic ratio gives the fitness difference, rather than the relative fitness. This fitness difference remains proportional to the actual replication rate realized in the particular experimental setup and hence cannot be extrapolated to other situations. Conversely, the conventional relative fitness (1 +
s
) should be more generic. We develop an approach to compute the generic relative fitness in conventional competition experiments. This involves an estimation of the total viral replication during the experiment and requires an estimate of the average lifetime of productively infected cells. The novel approach is illustrated by estimating the relative fitness, i.e., the relative replication rate, of a set of zidovudine-resistant human immunodeficiency virus type 1 variants. A tool for calculating the relative fitness from observed changes in viral load and genotype (or phenotype) frequencies is publically available on the website at

http://www-binf.bio.uu.nl/
∼
rdb/fitness.html

.
Complete Nucleotide Sequence and Genome Organization of Hibiscus Chlorotic Ringspot Virus, a New Member of the Genus
Carmovirus
: Evidence for the Presence and Expression of Two Novel Open Reading Frames
Authors: Huang Mei , Koh Dora Chin-Yen , Weng Li-Juan , Chang Min-Li , Yap Yun-Kiam , Zhang Lee , Wong Sek-Man 
Published: July 2002

ABSTRACT

The complete nucleotide sequence of hibiscus chlorotic ringspot virus (HCRSV) was determined. The genomic RNA (gRNA) is 3,911 nucleotides long and has the potential to encode seven viral proteins in the order of 28 (p28), 23 (p23), 81 (p81), 8 (p8), 9 (p9), 38 (p38), and 25 (p25) kDa. Excluding two unique open reading frames (ORFs) encoding p23 and p25, the ORFs encode proteins with high amino acid similarity to those of carmoviruses. In addition to gRNA, two 3′-coterminated subgenomic RNA (sgRNA) species were identified. Full-length cDNA clones derived from gRNA and sgRNA were constructed under the control of a T7 promoter. Both capped and uncapped transcripts derived from the full-length genomic cDNA clone were infectious. In vitro translation and mutagenesis assays confirmed that all the predicted ORFs except the ORF encoding p8 are translatable, and the two novel ORFs (those encoding p23 and p25) may be functionally indispensable for the viral infection cycle. Based on virion morphology and genome organization, we propose that HCRSV be classified as a new member of the genus
Carmovirus
in family
Tombusviridae
.
Regression of Established Human Papillomavirus Type 16 (HPV-16) Immortalized Tumors In Vivo by Vaccinia Viruses Expressing Different Forms of HPV-16 E7 Correlates with Enhanced CD8+T-Cell Responses That Home to the Tumor Site
Authors: Lamikanra Abigail , Pan Zhen-Kun , Isaacs Stuart N. , Wu Tzyy-Choou , Paterson Yvonne 
Published: July 2002

ABSTRACTUsing vaccinia virus as a live vector, we show that the expression of human papillomavirus type 16 (HPV-16) E7 fused to a nonhemolytic portion of theListeriamonocytogenesvirulence factor, listeriolysin O (LLO), induces an immune response that causes the regression of established HPV-16 immortalized tumors in C57BL/6 mice. The vaccinia virus construct expressing LLO fused to E7 (VacLLOE7) was compared with two previously described vaccinia virus constructs: one that expresses unmodified E7 (VacE7) and another that expresses E7 in a form designed to direct it to intracellular lysosomal compartments and improve major histocompatibility complex class II-restricted responses (VacSigE7LAMP-1). C57BL/6 mice bearing established HPV-16 immortalized tumors of 5 or 8 mm were treated with each of these vaccines. Fifty percent of the mice treated with VacLLOE7 remained tumor free 2 months after tumor inoculation, whereas 12 to 25% of the mice were tumor free after treatment with VacSigE7LAMP-1 (depending on the size of the tumor). No mice were tumor free in the group given VacE7. Compared to VacE7, VacSigE7LAMP-1 and VacLLOE7 resulted in increased numbers of H2-Db-specific tetramer-positive CD8+T cells in mouse spleens that produced gamma interferon and tumor necrosis factor alpha upon stimulation with RAHYNIVTF peptide. In addition, the highest frequency of tetramer-positive T cells was seen in the tumor sites of mice treated with VacLLOE7. An increased efficiency of E7-specific lysis by splenocytes from mice immunized with VacLLOE7 was also observed. These results indicate that the fusion of E7 with LLO not only enhances antitumor therapy by improving the tumoricidal function of E7-specific CD8+T cells but may also increase the number of antigen-specific CD8+T cells in the tumor, the principle site of antigen expression.
Novel
cis
-Acting Replication Element in the Adeno-Associated Virus Type 2 Genome Is Involved in Amplification of Integrated
rep-cap
Sequences
Authors: Nony Pascale , Tessier Jacques , Chadeuf Gilliane , Ward Peter , Giraud Aurélie , Dugast Marc , Linden R. Michael , Moullier Philippe , Salvetti Anna 
Published: July 2002

ABSTRACT

This study identifies a region of the adeno-associated virus type 2 (AAV-2)
rep
gene (nucleotides 190 to 540 of wild-type AAV-2) as a
cis
-acting Rep-dependent element able to promote the replication of transiently transfected plasmids. This viral element is also shown to be involved in the amplification of integrated sequences in the presence of adenovirus and Rep proteins.
Elicitation of High-Frequency Cytotoxic T-Lymphocyte Responses against both Dominant and Subdominant Simian-Human Immunodeficiency Virus Epitopes by DNA Vaccination of Rhesus Monkeys
Authors: Barouch Dan H. , Craiu Abie , Santra Sampa , Egan Michael A. , Schmitz Jörn E. , Kuroda Marcelo J. , Fu Tong-Ming , Nam Jae-Hwan , Wyatt Linda S. , Lifton Michelle A. , Krivulka Georgia R. , Nickerson Christine E. , Lord Carol I. , Moss Bernard , Lewis Mark G. , Hirsch Vanessa M. , Shiver John W. , Letvin Norman L. 
Published: July 2002

ABSTRACTIncreasing evidence suggests that the generation of cytotoxic T-lymphocyte (CTL) responses specific for a diversity of viral epitopes will be needed for an effective human immunodeficiency virus type 1 (HIV-1) vaccine. Here, we determine the frequencies of CTL responses specific for the simian immunodeficiency virus Gag p11C and HIV-1 Env p41A epitopes in simian-human immunodeficiency virus (SHIV)-infected and vaccinated rhesus monkeys. The p11C-specific CTL response was high frequency and dominant and the p41A-specific CTL response was low frequency and subdominant in both SHIV-infected monkeys and in monkeys vaccinated with recombinant modified vaccinia virus Ankara vectors expressing these viral antigens. Interestingly, we found that plasmid DNA vaccination led to high-frequency CTL responses specific for both of these epitopes. These data demonstrate that plasmid DNA may be useful in eliciting a broad CTL response against multiple epitopes.
Enhancer and Long-Term Expression Functions of Herpes Simplex Virus Type 1 Latency-Associated Promoter Are both Located in the Same Region
Authors: Berthomme Herve , Thomas Joëlle , Texier Pascale , Epstein Alberto , Feldman Lawrence T. 
Published: July 2002

ABSTRACT
During herpes simplex virus type 1 (HSV-1) latent infection in vivo, the latency-associated promoter (LAP) is the only promoter to remain highly active long term. In a previous attempt to characterize LAP activity in vitro and in a mouse model, we showed that a 1.5-kb fragment called the long-term expression element (LTE), located immediately downstream from the transcriptional start site of LAP, was able to (i) increase gene expression in an orientation-independent manner, regardless of the cell type or the promoter used in vitro (enhancer activity) and (ii) keep LAP active during latency in vivo (long-term expression activity) (H. Berthomme, J. Lokensgard, L. Yang, T. Margolis, and L. T. Feldman, J. Virol. 74:3613–3622, 2000). To determine if these two functions could be separated genetically, we conducted a mutational analysis on the LTE and analyzed the effect on the LAP-LTE properties in both transient expression in cell culture and mouse dorsal root ganglia lytic and latent infection. In this report, we show that the first half of the LTE sequence, corresponding to the region previously described as LAP2 or exon1, encodes the enhancer function. This same region is also required to keep the LAP active during latency. These results exclude the intron region as containing any significant enhancer activity or any ability to keep the LAP active during latency. The results also show that these two functions have not been separated, leaving open the possibility that there is no long-term expression function per se but that the enhancer itself may function to keep the LAP active during latency by raising the level of expression to a detectable one. Further mutational analysis will be required to determine if these two potential functions continue to cosegregate.
Chimeric Human Immunodeficiency Virus Type 1 Containing Murine Leukemia Virus Matrix Assembles in Murine Cells
Authors: Reed Margaret , Mariani Roberto , Sheppard Liana , Pekrun Katja , Landau Nathaniel R. , Soong Nay-Wei 
Published: July 2002

ABSTRACT
Murine cells do not support efficient assembly and release of human immunodeficiency virus type 1 (HIV-1) virions. HIV-1-infected mouse cells that express transfected human cyclin T1 synthesize abundant Gag precursor polyprotein, but inefficiently assemble and release virions. This assembly defect may result from a failure of the Gag polyprotein precursor to target to the cell membrane. Plasma membrane targeting of the precursor is mediated by the amino-terminal region of polyprotein. To compensate for the assembly block, we substituted the murine leukemia virus matrix coding sequences into an infectious HIV-1 clone. Transfection of murine fibroblasts expressing cyclin T1 with the chimeric proviruses resulted in viruses that were efficiently assembled and released. Chimeric viruses, in which the cytoplasmic tail of the transmembrane subunit, gp41, was truncated to prevent potential interference between the envelope glycoprotein and the heterologous matrix, could infect human and murine cells. They failed to further replicate in the murine cells, but replicated with delayed kinetics in human MT-4 cells. These findings may be useful for establishing a murine model for HIV-1 replication.