bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predominance of
Trypanosoma cruzi
Lineage I in Mexico
Authors: Bosseno Marie-France , Barnabé Christian , Magallón Gastélum Ezequiel , Lozano Kasten Felipe , Ramsey Janine , Espinoza Bertha , Brenière Simone Frédérique 
Published: July 2002

ABSTRACT

Randomly amplified polymorphic DNA (RAPD) has emerged as an effective genetic marker for analysis of
Trypanosoma cruzi
population variability. This method has been used to study the genetic variability of Mexican
T. cruzi
stocks and to relate these results to previous classifications. High clonal diversity was observed among the Mexican populations: 24 RAPD types were scored among 56 stocks analyzed. Only two stocks (3.6%) belonged to the
T. cruzi
II lineage, while all others belonged to
T. cruzi
I. The robustness of these clusters was statistically highly significant. Mexican
T. cruzi
I stocks formed a homogeneous group with reduced genetic distances among its members. Parasites from this group were isolated from both domestic and sylvatic cycles over a broad geographic area in Mexico. The two Mexican stocks classified as
T. cruzi
II (isolated from sylvatic cycles) were of the same RAPD type, although they were not closely related to the three reference
T. cruzi
II stocks circulating in domestic cycles in Argentina, Brazil, Bolivia, and Chile. These stocks were also unrelated to the formerly named Zymodeme III.
Genetic Characterization of H1N2 Influenza A Viruses Isolated from Pigs throughout the United States
Authors: Karasin Alexander I. , Landgraf John , Swenson Sabrina , Erickson Gene , Goyal Sagar , Woodruff Mary , Scherba Gail , Anderson Gary , Olsen Christopher W. 
Published: July 2002

ABSTRACT
An H1N2 influenza A virus was isolated from a pig in the United States for the first time in 1999 (A. I. Karasin, G. A. Anderson, and C. W. Olsen, J. Clin. Microbiol. 38:2453-2456, 2000). H1N2 viruses have been isolated subsequently from pigs in many states. Phylogenetic analyses of eight such viruses isolated from pigs in Indiana, Illinois, Minnesota, Ohio, Iowa, and North Carolina during 2000 to 2001 showed that these viruses are all of the same reassortant genotype as that of the initial H1N2 isolate from 1999.
A Positive-Strand RNA Virus with Three Very Different Subgenomic RNA Promoters
Authors: Koev Gennadiy , Miller W. Allen 
Published: July 2002

ABSTRACT
Numerous RNA viruses generate subgenomic mRNAs (sgRNAs) for expression of their 3′-proximal genes. A major step in control of viral gene expression is the regulation of sgRNA synthesis by specific promoter elements. We used barley yellow dwarf virus (BYDV) as a model system to study transcriptional control in a virus with multiple sgRNAs. BYDV generates three sgRNAs during infection. The sgRNA1 promoter has been mapped previously to a 98-nucleotide (nt) region which forms two stem-loop structures. It was determined that sgRNA1 is not required for BYDV RNA replication in oat protoplasts. In this study, we show that neither sgRNA2 nor sgRNA3 is required for BYDV RNA replication. The promoters for sgRNA2 and sgRNA3 synthesis were mapped by using deletion mutagenesis. The minimal sgRNA2 promoter is approximately 143 nt long (nt 4810 to 4952) and is located immediately downstream of the putative sgRNA2 start site (nt 4809). The minimal sgRNA3 core promoter is 44 nt long (nt 5345 to 5388), with most of the sequence located downstream of sgRNA3 start site (nt 5348). For both promoters, additional sequences upstream of the start site enhanced sgRNA promoter activity. These promoters contrast to the sgRNA1 promoter, in which almost all of the promoter is located upstream of the transcription initiation site. Comparison of RNA sequences and computer-predicted secondary structures revealed little or no homology between the three sgRNA promoter elements. Thus, a small RNA virus with multiple sgRNAs can have very different subgenomic promoters, which implies a complex system for promoter recognition and regulation of subgenomic RNA synthesis.
The Majority of Duck Hepatitis B Virus Reverse Transcriptase in Cells Is Nonencapsidated and Is Bound to a Cytoplasmic Structure
Authors: Yao Ermei , Gong Yunhao , Chen Nanhai , Tavis John E. 
Published: July 2002

ABSTRACTThe hepadnavirus reverse transcriptase binds cotranslationally to the viral pregenomic RNA. This ribonucleoprotein complex is then encapsidated into nascent viral core particles, where the reverse transcriptase copies the viral RNA into DNA. Here we report that 75% of the duck hepatitis B virus reverse transcriptase present in transfected LMH cells does not follow this well-known pathway but rather exists in the cell separate from the core protein or nucleocapsids. The nonencapsidated reverse transcriptase is also abundant in infected duck liver. The nonencapsidated reverse transcriptase exists as a complex set of isoforms that are most likely produced by posttranslational modification. Interestingly, only the smallest of these isoforms is encapsidated into viral core particles. The nonencapsidated reverse transcriptase is bound to a large cellular cytoplasmic structure(s) in a detergent-sensitive complex. The cellular distribution of the reverse transcriptase only partially overlaps that of the core protein, and this distribution is unaffected by blocking encapsidation. These observations raise the possibilities that the metabolic fate of the reverse transcriptase may be posttranscriptionally regulated and that the reverse transcriptase may have roles in the viral replication cycle beyond its well-known function in copying the viral genome.
Is the 135S Poliovirus Particle an Intermediate during Cell Entry?
Authors: Huang Yan , Hogle James M. , Chow Marie 
Published: July 2002

ABSTRACT
Poliovirus binding to its receptor (PVR) on the cell surface induces a conformational transition which generates an altered particle with a sedimentation value of 135S versus the 160S of the native virion. A number of lines of evidence suggest that the 135S particle is a cell entry intermediate. However, the low infection efficiencies of the 135S particle and the absence of detectable 135S particles during infection at 26°C by the cold-adapted mutants argue against a role for the 135S particle during the cell entry process. We show here that binding of 135S-antibody complexes to the Fc receptor (CDw32) increases the infectivity of these particles by 2 to 3 orders of magnitude. Thus, the low efficiency of infection by 135S particles is due in part to the low binding affinity of these particles. In addition, we show that there is an additional stage in the entry process that is associated with RNA release. This stage occurs after formation of the 135S particle, is rate limiting during infection at 37°C, but not at 26°C, and is PVR independent. The data also demonstrate that during infection at 26°C, the rate-limiting step is the PVR-mediated conversion of wild-type 160S particles to 135S particles. This suggests that during infection at 26°C by the cold-adapted viruses, 135S particles are formed, but they fail to accumulate to detectable levels because the subsequent post-135S particle events occur at a significantly faster rate than the initial conversion of 160S to 135S particles. These data support a model in which the 135S particle is an intermediate during poliovirus entry.
Role of Dendritic Cell Targeting in Venezuelan Equine Encephalitis Virus Pathogenesis
Authors: MacDonald Gene H. , Johnston Robert E. 
Published: July 2002

ABSTRACT
The initial steps of Venezuelan equine encephalitis virus (VEE) spread from inoculation in the skin to the draining lymph node have been characterized. By using green fluorescent protein and immunocytochemistry, dendritic cells in the draining lymph node were determined to be the primary target of VEE infection in the first 48 h following inoculation. VEE viral replicon particles, which can undergo only one round of infection, identified Langerhans cells to be the initial set of cells infected by VEE directly following inoculation. These cells are resident dendritic cells in the skin, which migrate to the draining lymph node following activation. A point mutation in the E2 glycoprotein gene of VEE that renders the virus avirulent and compromises its ability to spread beyond the draining lymph blocked the appearance of virally infected dendritic cells in the lymph node in vivo. A second-site suppressor mutation that restores viral spread to lymphoid tissues and partially restore virulence likewise restored the ability of VEE to infect dendritic cells in vivo.
Lack of Shielding of Primer Binding Site Silencer-Mediated Repression of an Internal Promoter in a Retrovirus Vector by the Putative Insulators scs, BEAD-1, and HS4
Authors: Modin Charlotte , Pedersen Finn Skou , Duch Mogens 
Published: July 2002

ABSTRACT
A major determinant for transcriptional incompetence of murine leukemia virus (MLV) and MLV-derived vectors in embryonal cells is located at the proline primer binding site (PBS). The mechanism of silencing is unknown, yet the effect is capable of spreading to adjacent promoters. Based on a retroviral vector containing an internal promoter and the escape mutant B2 PBS with expressional capacity in embryonal cells, we have developed an assay to test the ability of putative insulators to shield the silencer at the PBS. Since the B2 PBS reverts to the wild-type PBS at high frequency, a shielding ability of a putative insulator can be assessed from the ratio of expressing B2 PBS to proline PBS proviruses in the target embryonal carcinoma cell population as measured by primer extension. Our results show that none of the possible insulators, scs, BEAD-1, or HS4, is able to shield an internal promoter from the repressive effect of the silencer at the PBS region when inserted between the silencer and the promoter.
Horizontal Transmissible Protection against Myxomatosis and Rabbit Hemorrhagic Disease by Using a Recombinant Myxoma Virus
Authors: Bárcena Juan , Morales Mónica , Vázquez Belén , Boga José A. , Parra Francisco , Lucientes Javier , Pagès-Manté Albert , Sánchez-Vizcaíno José M. , Blasco Rafael , Torres Juan M. 
Published: July 2002

ABSTRACTWe have developed a new strategy for immunization of wild rabbit populations against myxomatosis and rabbit hemorrhagic disease (RHD) that uses recombinant viruses based on a naturally attenuated field strain of myxoma virus (MV). The recombinant viruses expressed the RHDV major capsid protein (VP60) including a linear epitope tag from the transmissible gastroenteritis virus (TGEV) nucleoprotein. Following inoculation, the recombinant viruses induced specific antibody responses against MV, RHDV, and the TGEV tag. Immunization of wild rabbits by the subcutaneous and oral routes conferred protection against virulent RHDV and MV challenges. The recombinant viruses showed a limited horizontal transmission capacity, either by direct contact or in a flea-mediated process, promoting immunization of contact uninoculated animals.
Activation of the Mitogen-Activated Protein Kinase p38 by Human Cytomegalovirus Infection through Two Distinct Pathways: a Novel Mechanism for Activation of p38
Authors: Johnson Robert A. , Huong Shu-Mei , Huang Eng-Shang 
Published: July 2002

ABSTRACTRecent evidence indicates activated mitogen-activated protein kinase (MAPK) p38 has a critical function in human cytomegalovirus (HCMV) viral DNA replication in infected human fibroblasts. To elucidate the mechanism of HCMV-mediated p38 activation, we have performed a detailed analysis of p38 activation and the kinases associated with this activation at different times postinfection. We demonstrate that p38 kinase activity is strongly increased following viral infection. Inhibition of this activity significantly inhibited HCMV-induced hyperphosphorylation of pRb and phosphorylation of heat shock protein 27, suggesting that p38 activation is involved in virus-mediated changes in host cell metabolism throughout the course of infection. We then provide evidence that p38 activation is mediated by different mechanisms at early times versus later times of infection. At early times of infection (8 to 14 h postinfection [hpi]), when p38 activation is first observed, no significant activation of the three kinases which can directly phosphorylate p38 (namely, MKK3, MKK6, and MKK4) is detected. Using vectors which express dominant negative proteins, we demonstrate that basal MKK6 kinase activity is necessary for HCMV-mediated p38 activation at these early times of infection (12 hpi). Then, we use ATP depletion to show that at 12 hpi, HCMV inhibits dephosphorylation of activated p38. These two experiments suggest that HCMV activates p38 by inhibition of dephosphorylation of p38. In contrast to early times of infection, at later times of infection (48 to 72 hpi), increased MKK3/6, but not MKK4, activity is observed. These results indicate that at early times of HCMV infection, increased steady-state levels of activated p38 is mediated at least in part by inhibition of dephosphorylation of p38, while at later times of infection p38 activation is due to increased activity of the upstream kinases MKK3 and MKK6. These findings indicate that HCMV has developed multiple mechanisms to ensure activation of the MAPK p38, a kinase critical to viral infection.
Chimeric Yellow Fever Virus 17D-Japanese Encephalitis Virus Vaccine: Dose-Response Effectiveness and Extended Safety Testing in Rhesus Monkeys
Authors: Monath T. P. , Levenbook I. , Soike K. , Zhang Z.-X. , Ratterree M. , Draper K. , Barrett A. D. T. , Nichols R. , Weltzin R. , Arroyo J. , Guirakhoo F. 
Published: July 2002

ABSTRACTChimeriVax-JE is a live, attenuated recombinant virus prepared by replacing the genes encoding two structural proteins (prM and E) of yellow fever 17D virus with the corresponding genes of an attenuated strain of Japanese encephalitis virus (JE), SA14-14-2 (T. J. Chambers et al., J. Virol. 73:3095–3101, 1999). Since the prM and E proteins contain antigens conferring protective humoral and cellular immunity, the immune response to vaccination is directed principally at JE. The prM-E genome sequence of the ChimeriVax-JE in diploid fetal rhesus lung cells (FRhL, a substrate acceptable for human vaccines) was identical to that of JE SA14-14-2 vaccine and differed from sequences of virulent wild-type strains (SA14 and Nakayama) at six amino acid residues in the envelope gene (E107, E138, E176, E279, E315, and E439). ChimeriVax-JE was fully attenuated for weaned mice inoculated by the intracerebral (i.c.) route, whereas commercial yellow fever 17D vaccine (YF-Vax) caused lethal encephalitis with a 50% lethal dose of 1.67 log10PFU. Groups of four rhesus monkeys were inoculated by the subcutaneous route with 2.0, 3.0, 4.0, and 5.0 log10PFU of ChimeriVax-JE. All 16 monkeys developed low viremias (mean peak viremia, 1.7 to 2.1 log10PFU/ml; mean duration, 1.8 to 2.3 days). Neutralizing antibodies appeared between days 6 and 10; by day 30, neutralizing antibody responses were similar across dose groups. Neutralizing antibody titers to the homologous (vaccine) strain were higher than to the heterologous wild-type JE strains. All immunized monkeys and sham-immunized controls were challenged i.c. on day 54 with 5.2 log10PFU of wild-type JE. None of the immunized monkeys developed viremia or illness and had mild residual brain lesions, whereas controls developed viremia, clinical encephalitis, and severe histopathologic lesions. Immunized monkeys developed significant (≥4-fold) increases in serum and cerebrospinal fluid neutralizing antibodies after i.c. challenge. In a standardized test for neurovirulence, ChimeriVax-JE and YF-Vax were compared in groups of 10 monkeys inoculated i.c. and analyzed histopathologically on day 30. Lesion scores in brains and spinal cord were significantly higher for monkeys inoculated with YF-Vax. ChimeriVax-JE meets preclinical safety and efficacy requirements for a human vaccine; it appears safer than yellow fever 17D vaccine but has a similar profile of immunogenicity and protective efficacy.
Oligomeric Modeling and Electrostatic Analysis of the gp120 Envelope Glycoprotein of Human Immunodeficiency Virus
Authors: Kwong Peter D. , Wyatt Richard , Sattentau Quentin J. , Sodroski Joseph , Hendrickson Wayne A. 
Published: July 2002

ABSTRACT
The human immunodeficiency virus envelope glycoproteins, gp120 and gp41, function in cell entry by binding to CD4 and a chemokine receptor on the cell surface and orchestrating the direct fusion of the viral and target cell membranes. On the virion surface, three gp120 molecules associate noncovalently with the ectodomain of the gp41 trimer to form the envelope oligomer. Although an atomic-level structure of a monomeric gp120 core has been determined, the structure of the oligomer is unknown. Here, the orientation of gp120 in the oligomer is modeled by using quantifiable criteria of carbohydrate exposure, occlusion of conserved residues, and steric considerations with regard to the binding of the neutralizing antibody 17b. Applying similar modeling techniques to influenza virus hemagglutinin suggests a rotational accuracy for the oriented gp120 of better than 10°. The model shows that CD4 binds obliquely, such that multiple CD4 molecules bound to the same oligomer have their membrane-spanning portions separated by at least 190 Å. The chemokine receptor, in contrast, binds to a sterically restricted surface close to the trimer axis. Electrostatic analyses reveal a basic region which faces away from the virus, toward the target cell membrane, and is conserved on core gp120. The electrostatic potentials of this region are strongly influenced by the overall charge, but not the precise structure, of the third variable (V3) loop. This dependence on charge and not structure may make electrostatic interactions between this basic region and the cell difficult to target therapeutically and may also provide a means of viral escape from immune system surveillance.
Expression of Two Related Viral Early Genes in Epstein-Barr Virus-Associated Tumors
Authors: Xue Shao-An , Lu Qi-Long , Poulsom R. , Karran Loraine , Jones M. D. , Griffin Beverly E. 
Published: July 2002

ABSTRACT

The transcription of two early “leftwardly” expressed genes carrying repetitive sequences, IR2 and IR4, has been studied for Epstein-Barr virus-associated tumors, and for established B-cell lines, using sequence-specific probes generated for this purpose. Whereas the IR4 transcript was identified in every tumor and cell line assessed (except B95-8, with a deletion that removes the gene), expression of the IR2 gene was restricted to B lymphocytes. Though the promoters for both transcripts lie within homologous regions (D
L
and D
R
) in the viral genome, the IR2 promoter appears more tightly regulated. Detailed characterization of the IR4 transcript from a nasopharyngeal carcinoma tumor, C15, identifies a sequence variant of this gene that differs from those reported for B cells; in situ hybridization methods show transcription to be restricted to a subset of cells, with the strongest signals seen adjacent to host stroma. As with B cells in culture (Y. Gao, P. R. Smith, L. Karran, Q. L. Lu, and B. E. Griffin, J. Virol. 71:84–94, 1997), chemical induction enhanced transcriptional expression of the IR4 gene in the C15 tumor, although staining for both the IR4 antigen and that of the virus lytic switch, Zta, gave negative results. In a Burkitt's lymphoma biopsy specimen, however, both proteins were found expressed, notably in the same subset of cells. The data here and elsewhere (Gao et al., J. Virol., 1997) are consistent with a block to intracellular transport of the transcript(s) and suggest nuclear roles for it in tumors, possibly in RNA processing and viral lytic replication. Both roles could be fulfilled in the absence of translation.
Microarray Analysis Identifies Interferon-Inducible Genes and Stat-1 as Major Transcriptional Targets of Human Papillomavirus Type 31
Authors: Chang Yijan E. , Laimins Laimonis A. 
Published: July 2002

ABSTRACT
Human papillomaviruses (HPVs) infect keratinocytes and induce proliferative lesions. In infected cells, viral gene products alter the activities of cellular proteins, such as Rb and p53, resulting in altered cell cycle response. It is likely that HPV gene products also alter expression of cellular genes. In this study we used microarray analysis to examine the global changes in gene expression induced by high-risk HPV type 31 (HPV31). Among 7,075 known genes and ESTs (expressed sequence tags) tested, we found that 178 were upregulated and 150 were downregulated twofold or more in HPV31 cells compared to normal human keratinocytes. While no specific pattern could be deduced from the list of genes that were upregulated, downregulated genes could be classified to three groups: genes that are involved in the regulation of cell growth, genes that are specifically expressed in keratinocytes, and genes whose expression is increased in response to interferon stimulation. The basal level of expression of several interferon-responsive genes was found to be downregulated in HPV31 cells by both microarray analysis and Northern blot analysis in different HPV31 cell lines. When cells were treated with alpha or gamma interferon, expression of interferon-inducible genes was impaired. At high doses of interferon, the effects were less pronounced. Among the genes repressed by HPV31 was the signal transducer and activator of transcription (Stat-1), which plays a major role in mediating the interferon response. Suppression of Stat-1 expression may contribute to a suppressed response to interferon as well as immune evasion.
Selective Induction of Apoptosis in Antigen-Presenting Cells in Mice by
Parapoxvirus ovis
Authors: Kruse Nicole , Weber Olaf 
Published: July 2002

ABSTRACT

Viruses have evolved numerous mechanisms to avoid host immune reactions. Here we report a mechanism by which
Parapoxvirus ovis
(PPVO) interferes with antigen presentation. PPVO (
orf
virus) causes orf, an acute skin disease of sheep and goats worldwide. Importantly, PPVO can repeatedly infect its host in spite of a vigorous inflammatory and host immune response to the infection. We demonstrate in a mouse system that PPVO induces apoptosis in a significant number of antigen-presenting cells after intraperitoneal injection using the CD95 pathway, thus preventing a primary T-cell response. We also show that PPVO induces a compensatory activation of the immune system. Our results may help to explain the phenomenon that natural PPVO infections in sheep occur repeatedly even after short intervals. They also suggest that the combination of immunosuppressive and immunostimulatory mechanisms is an effective survival strategy that might be used in other viruses as well.
Identification of the Immunodominant H-2Kk-Restricted Cytotoxic T-Cell Epitope in the Borna Disease Virus Nucleoprotein
Authors: Schamel Karin , Staeheli Peter , Hausmann Jürgen 
Published: July 2002

ABSTRACTBorna disease virus (BDV)-induced immunopathology in mice is most prominent in strains carrying the major histocompatibility complexH-2kallele and is mediated by CD8+T cells that are directed against the viral nucleoprotein p40. We now identified the highly conserved octamer peptide TELEISSI, located between amino acid residues 129 and 136 of BDV p40, as a potent H-2Kk-restricted cytotoxic T-cell (CTL) epitope. When added to the culture medium of L929 target cells, TELEISSI conferred sensitivity to lysis by CTLs isolated from brains of BDV-infected MRL mice with acute neurological disease. Vaccinia virus-mediated expression of a p40 variant with mutations in the two Kk-specific anchor residues of the TELEISSI peptide (p40E130K,I136T) did not sensitize L929 target cells for lysis by BDV-specific CTLs, whereas expression of wild-type p40 did. Furthermore, unlike vaccination with wild-type p40, vaccination of persistently infected symptomless B10.BR mice with p40E130K,I136Tdid not result in central nervous system inflammation and neurological disease. These results demonstrate that TELEISSI is the immunodominant CTL epitope of BDV p40 inH-2kmice.