bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antigenic Diversity and Distribution of Rabies Virus in Mexico
Authors: Velasco-Villa Andrés , Gómez-Sierra Mauricio , Hernández-Rodríguez Gustavo , Juárez-Islas Victor , Meléndez-Félix Alejandra , Vargas-Pino Fernando , Velázquez-Monroy Oscar , Flisser Ana 
Published: July 2002

ABSTRACT

Rabies remains a public health problem in the Americas because of the great diversity of wild reservoirs that maintain the virus in nature. Here we report the antigenic characterization of 254 rabies viruses isolated from 148 nonreservoir and 106 reservoir hosts collected in 27 states of Mexico. Nine out of 11 antigenic variants previously reported in the United States were detected in Mexico by using the limited panel of monoclonal antibodies donated by the Centers for Disease Control and Prevention. Some rabies virus variants were isolated from their natural reservoirs, which were also taxonomically identified. Terrestrial reservoirs included stray dogs with V1,
Urocyon cineroargenteus
(gray foxes) with V7, and two subspecies of
Spilogale putorius
(spotted skunks) with different viral variants (V8 and V10). Aerial hosts included
Tadarida brasiliensis mexicana
and
Desmodus rotundus
, which harbored V9 and V4 and harbored V11, respectively. All variants, with the exception of V9, were isolated from nonreservoir hosts, while V3, V4, and V5 were not isolated from their natural reservoirs but only from livestock. Rabies virus antigenic typing allowed us to determine rabies reservoirs and their distribution in Mexico, data which will probably improve prevention and control of the illness in humans and in the reservoir hosts.
Enhanced Enzyme-Linked Immunosorbent Assay for Detection of Antibodies to Virus-Like Particles of Human Papillomavirus
Authors: Studentsov Yevgeniy Y. , Schiffman Mark , Strickler Howard D. , Ho Gloria Y. F. , Pang Yuk-Ying Susana , Schiller John , Herrero Rolando , Burk Robert D. 
Published: July 2002

ABSTRACT
Measurement of antibodies to human papillomavirus (HPV) is complicated by many factors. Although enzyme-linked immunosorbent assays (ELISAs) that use virus-like particles (VLPs) have proved useful, the assays have, in general, had moderate sensitivities and low signal-to-noise ratios. To enhance the performance of the assay, a systematic investigation was undertaken to examine key variables used in ELISAs for the detection of antibodies to VLPs of HPV. Incorporation of two vinyl polymers, polyvinyl alcohol (molecular weight, 50,000) (PVA-50) and polyvinylpyrrolidone (molecular weight, 360,000) (PVP-360), was found to increase the sensitivity as well as the specificity of the assay for the detection of antibodies to VLPs of HPV. In particular, the addition of PVA-50 to the blocking solution reduced the amount of nonspecific binding of antibodies to VLPs and the microplate surface, whereas the addition of PVP-360 increased the sensitivity of antibody detection. The new ELISA demonstrated increased sensitivity and specificity for the detection of cervical HPV type 16 infection compared to those of a prototype assay with coded clinical serum samples from women with known cervicovaginal HPV infection status. It is anticipated that the enhanced ELISA conditions will have wide application to a large number of clinical diagnostic assays.
Microsatellite Characterization of
Plasmodium falciparum
from Cerebral and Uncomplicated Malaria Patients in Southern Vietnam
Authors: Ferreira Marcelo U. , Nair Shalini , Hyunh Thien Van , Kawamoto Fumihiko , Anderson Timothy J. C. 
Published: July 2002

ABSTRACT

If parasite genotype influences the clinical course of malaria, we expect that isolates from patients with similar pathology would be more closely related than would be expected by chance. To explore this prediction, we typed nine microsatellite markers in sympatric
Plasmodium falciparum
isolates from cerebral and uncomplicated malaria patients from Vietnam. Temporal structure and linkage disequilibrium were also examined in this data set.
Development of Variable-Number Tandem Repeat Typing ofMycobacterium bovis: Comparison of Results with Those Obtained by Using Existing Exact Tandem Repeats and Spoligotyping
Authors: Roring Solvig , Scott Alistair , Brittain David , Walker Ian , Hewinson Glyn , Neill Sydney , Skuce Robin 
Published: July 2002

ABSTRACTVarious genetic markers have been exploited for fingerprinting theMycobacterium tuberculosiscomplex (MTBC) in molecular epidemiological studies, mainly through identifying restriction fragment length polymorphisms (RFLP). In large-scale studies, RFLP typing has practical processing and analysis limitations; therefore, attempts have been made to move towards PCR-based typing techniques. Spoligotyping (spacer oligotyping) and, more recently, variable-number tandem repeat (VNTR) typing have provided PCR-derived typing techniques. This study describes the identification and characterization of novel VNTR loci, consisting of tandem repeats in the size range of 53 to 59 bp in the MTBC, and their assessment as typing tools in 47Mycobacterium bovisfield isolates and nine MTBC strains. Spoligotyping and the previously described set of exact tandem repeats (ETRs) (R. Frothingham and W. A. Meeker-O'Connell, Microbiology144:1189-1196, 1998) were also applied to the same panel of isolates. The allelic diversity of the individual VNTR loci was calculated, and a comparison of the novel VNTRs was made against the results obtained by spoligotyping and the existing set of ETRs. Eleven unique spoligotypes were discriminated in the panel of 47M. bovisisolates. Greater resolution was obtained through the combination of the most-discriminating VNTRs from both sets. Considerable discrimination was achieved, with the 47M. bovisisolates resolved into 14 unique profiles, while all nine MTBC isolates were uniquely differentiated. The novel VNTR markers described increased the discrimination possible in strain typing ofM. bovis, with the added benefit of an intuitive digital nomenclature, with the allele copy number of the individual VNTRs providing a profile. VNTR typing was shown to be a valuable technique with great potential for further development and application to epidemiological tracing of tuberculosis transmissions.
The Intracytoplasmic Domain of the Env Transmembrane Protein Is a Locus for Attenuation of Simian Immunodeficiency Virus SIVmac in Rhesus Macaques
Authors: Shacklett Barbara L. , Weber Claudia Jo , Shaw Karen E. S. , Keddie Elise M. , Gardner Murray B. , Sonigo Pierre , Luciw Paul A. 
Published: July 2002

ABSTRACTThe human and simian immunodeficiency virus (HIV-1 and SIVmac) transmembrane proteins contain unusually long intracytoplasmic domains (ICD-TM). These domains are suggested to play a role in envelope fusogenicity, interaction with the viral matrix protein during assembly, viral infectivity, binding of intracellular calmodulin, disruption of membranes, and induction of apoptosis. Here we describe a novel mutant virus, SIVmac-M4, containing multiple mutations in the coding region for the ICD-TM of pathogenic molecular clone SIVmac239. Parental SIVmac239-Nef+ produces high-level persistent viremia and simian AIDS in both juvenile and newborn rhesus macaques. The ICD-TM region of SIVmac-M4 contains three stop codons, a +1 frameshift, and mutation of three highly conserved, charged residues in the conserved C-terminal alpha-helix referred to as lentivirus lytic peptide 1 (LLP-1). Overlapping reading frames fortat,rev, andnefare not affected by these changes. In this study, four juvenile macaques received SIVmac-M4 by intravenous injection. Plasma viremia, as measured by branched-DNA (bDNA) assay, reached a peak at 2 weeks postinoculation but dropped to below detectable levels by 12 weeks. At over 1.5 years postinoculation, all four juvenile macaques remain healthy and asymptomatic. In a subsequent experiment, four neonatal rhesus macaques were given SIVmac-M4 intravenously. These animals exhibited high levels of viremia in the acute phase (2 weeks postinoculation) but are showing a relatively low viral load in the chronic phase of infection, with no clinical signs of disease for 1 year. These findings demonstrated that the intracytoplasmic domain of the transmembrane Env (Env-TM) is a locus for attenuation in rhesus macaques.
The Chicken Anemia Virus-Derived Protein Apoptin Requires Activation of Caspases for Induction of Apoptosis in Human Tumor Cells
Authors: Danen-van Oorschot A. A. A. M. , van der Eb A. J. , Noteborn M. H. M. 
Published: July 2002

ABSTRACT

The chicken anemia virus protein Apoptin has been shown to induce apoptosis in a large number of transformed and tumor cell lines, but not in primary cells. Whereas many other apoptotic stimuli (e.g., many chemotherapeutic agents and radiation) require functional p53 and are inhibited by Bcl-2, Apoptin acts independently of p53, and its activity is enhanced by Bcl-2. Here we study the involvement of caspases, an important component of the apoptotic machinery present in mammalian cells. Using a specific antibody, active caspase-3 was detected in cells expressing Apoptin and undergoing apoptosis. Although Apoptin activity was not affected by CrmA, p35 did inhibit Apoptin-induced apoptosis, as determined by nuclear morphology. Cells expressing both Apoptin and p35 showed only a slight change in nuclear morphology. However, in most of these cells, cytochrome
c
is still released and the mitochondria are not stained by CMX-Ros, indicating a drop in mitochondrial membrane potential. These results imply that although the final apoptotic events are blocked by p35, parts of the upstream apoptotic pathway that affect mitochondria are already activated by Apoptin. Taken together, these data show that the viral protein Apoptin employs cellular apoptotic factors for induction of apoptosis. Although activation of upstream caspases is not required, activation of caspase-3 and possibly also other downstream caspases is essential for rapid Apoptin-induced apoptosis.
The First Step of Adenovirus Type 2 Disassembly Occurs at the Cell Surface, Independently of Endocytosis and Escape to the Cytosol
Authors: Nakano M. Y. , Boucke K. , Suomalainen M. , Stidwill R. P. , Greber U. F. 
Published: July 2002

ABSTRACT
Disassembly is a key event of virus entry into cells. Here, we have investigated cellular requirements for the first step of adenovirus type 2 (Ad2) disassembly, the release of the fibers. Although fiber release coincides temporally with virus uptake, fiber release is not required for Ad2 endocytosis. It is, however, inhibited by actin-disrupting agents or soluble RGD peptides, which interfere with integrin-dependent endocytosis of Ad2. Fiber release occurs at the cell surface. Actin stabilization with jasplakinolide blocks Ad2 entry at extended cell surface invaginations and efficiently promotes fiber release, indicating that fiber release and virus endocytosis are independent events. Fiber release is not sufficient for Ad2 escape from endosomes, since inhibition of protein kinase C (PKC) prevents Ad2 escape from endosomes but does not affect virus internalization or fiber release. PKC-inhibited cells accumulate Ad2 in small vesicles near the cell periphery, indicating that PKC is also required for membrane trafficking of virus. Taken together, our data show that fiber release from incoming Ad2 requires integrins and filamentous actin. Together with correct subcellular transport of Ad2-containing endosomes, fiber release is essential for efficient delivery of virus to the cytosol. We speculate that fiber release at the surface might extend the host range of Ad2 since it is associated with the separation of a small fraction of incoming virus from the target cells.
Semliki Forest Virus Budding: Assay, Mechanisms, and Cholesterol Requirement
Authors: Lu Yanping E. , Kielian Margaret 
Published: July 2002

ABSTRACT
All enveloped viruses must bud through a cellular membrane in order to acquire their lipid bilayer, but little is known about this important stage in virus biogenesis. We have developed a quantitative biochemical assay to monitor the budding of Semliki Forest virus (SFV), an enveloped alphavirus that buds from the plasma membrane in a reaction requiring both viral spike proteins and nucleocapsid. The assay was based on cell surface biotinylation of newly synthesized virus spike proteins and retrieval of biotinylated virions using streptavidin-conjugated magnetic particles. Budding of biotin-tagged SFV was continuous for at least 2 h, independent of microfilaments and microtubules, strongly temperature dependent, and relatively independent of continued exocytic transport. Studies of cell surface spike proteins at early times of infection showed that these spikes did not efficiently bud into virus particles and were rapidly degraded. In contrast, at later times of infection, spike protein degradation was markedly reduced and efficient budding was then observed. The previously described cholesterol requirement in SFV exit was shown to be due to a block in budding in the absence of cholesterol and correlated with the continued degradation of spike proteins at all times of virus infection in sterol-deficient cells.
Neuroinvasion by Human Respiratory Coronaviruses
Authors: Arbour Nathalie , Day Robert , Newcombe Jia , Talbot Pierre J. 
Published: July 2002

ABSTRACTHuman coronaviruses (HCoV) cause common colds but can also infect neural cell cultures. To provide definitive experimental evidence for the neurotropism and neuroinvasion of HCoV and its possible association with multiple sclerosis (MS), we have performed an extensive search and characterization of HCoV RNA in a large panel of human brain autopsy samples. Very stringent reverse transcription-PCR with two primer pairs for both viral strains (229E and OC43), combined with Southern hybridization, was performed on samples from 90 coded donors with various neurological diseases (39 with MS and 26 with other neurological diseases) or normal controls (25 patients). We report that 44% (40 of 90) of donors were positive for 229E and that 23% (21 of 90) were positive for OC43. A statistically significant higher prevalence of OC43 in MS patients (35.9%; 14 of 39) than in controls (13.7%; 7 of 51) was observed. Sequencing of nucleocapsid protein (N) gene amplicons revealed point mutations in OC43, some consistently found in three MS patient brains and one normal control but never observed in laboratory viruses. In situ hybridization confirmed the presence of viral RNA in brain parenchyma, outside blood vessels. The presence of HCoV in human brains is consistent with neuroinvasion by these respiratory pathogens. Further studies are needed to distinguish between opportunistic and disease-associated viral presence in human brains.
Induction of the Chemokines Interleukin-8 and IP-10 by Human Immunodeficiency Virus Type 1 Tat in Astrocytes
Authors: Kutsch O. , Oh J.-W. , Nath A. , Benveniste E. N. 
Published: July 2002

ABSTRACTA finding commonly observed in human immunodeficiency virus type 1 (HIV-1)-infected patients is invasion of the brain by activated T cells and infected macrophages, eventually leading to the development of neurological disorders and HIV-1-associated dementia. The recruitment of T cells and macrophages into the brain is likely the result of chemokine expression. Indeed, earlier studies revealed that levels of different chemokines were increased in the cerebrospinal fluid of HIV-1-infected patients whereas possible triggers and cellular sources for chemokine expression in the brain remain widely undefined. As previous studies indicated that HIV-1 Tat, the retroviral transactivator, is capable of inducing a variety of cellular genes, we investigated its capacity to induce production of chemokines in astrocytes. Herein, we demonstrate that HIV-1 Tat72aais a potent inducer of MCP-1, interleukin-8 (IL-8), and IP-10 expression in astrocytes. Levels of induced IP-10 protein were sufficiently high to induce chemotaxis of peripheral blood lymphocytes. In addition, Tat72aainduced IL-8 expression in astrocytes. IL-8 mRNA induction was seen less then 1 h after Tat72aastimulation, and levels remained elevated for up to 24 h, leading to IL-8 protein production. Tat72aa-mediated MCP-1 and IL-8 mRNA induction was susceptible to inhibition by the MEK1/2 inhibitor UO126 but was only modestly decreased by the inclusion of the p38 mitogen-activated protein kinase (MAPK) inhibitor SB202190. In contrast, Tat-mediated IP-10 mRNA induction was suppressed by SB202190 but not by the MEK1/2 inhibitor UO126. These findings indicate that MAPKs play a major role in Tat72aa-mediated chemokine induction in astrocytes.
RNA Sequences Involved in Transcriptional Termination of Respiratory Syncytial Virus
Authors: Harmon Shawn B. , Megaw A. George , Wertz Gail W. 
Published: July 2002

ABSTRACT

RNA signals at the ends of the genes of respiratory syncytial (RS) virus direct polyadenylation and termination of viral transcription. These gene ends contain two conserved regions, a pentanucleotide and a tract of uridylate (U) residues, separated by an A/U-rich central region that is less well conserved. The U tract is thought to be the template for polyadenylation of viral mRNAs by reiterative transcription. The
cis
-acting requirements for termination were investigated by mutagenesis of the matrix (M) gene end (3′-UCAAUUAUUUUUU-5′) in a dicistronic RNA replicon. Termination efficiencies were quantitated by intracellular metabolic labeling of monocistronic mRNAs and the dicistronic readthrough RNAs that result when termination fails to occur. All three regions of the gene end were necessary for termination. Mutation of each of the first 8 nucleotides of the M gene end to all other nucleotides showed that nucleotides 2 to 6 were important for termination and intolerant of change, whereas nucleotides 1 and 7 were tolerant of change. At position 8, A or U allowed termination, but G or C did not. Both the length and the position of the U tract were important for termination. U residues at positions 9 to 12 were necessary, while additional U residues at position 8, and especially position 13, enhanced termination efficiency. Altering the length of the central region abolished termination, suggesting that the position of the U tract with respect to the 3′-UCAAU-5′ sequence was critical. The termination efficiencies of each of the 10 genes of RS virus are different. Since transcription is obligatorily sequential and termination of each gene is required for transcription of the next gene downstream, these differences may contribute to gene regulation. In agreement with our data, the naturally occurring gene ends of RS virus that terminate inefficiently have short U tracts or other sequence features that correlated with decreased termination when similar mutations were analyzed in RNA replicons.
CD4+T Cells and Gamma Interferon in the Long-Term Control of Persistent Friend Retrovirus Infection
Authors: Iwashiro Michihiro , Peterson Karin , Messer Ronald J. , Stromnes Ingunn M. , Hasenkrug Kim J. 
Published: July 2002

ABSTRACTWe have used the Friend virus model to determine the basic mechanisms by which the immune system can control persistent retroviral infections. Previously we showed that CD4+T cells play an essential role in keeping persistent retrovirus in check. The present in vitro experiments with a Friend virus-specific CD4+T-cell clone revealed that these cells produce gamma interferon (IFN-γ), which acts with two distinct mechanisms of antiviral activity. First, IFN-γ had a direct inhibitory effect on virus production. This inhibitory effect was noncytolytic and, interestingly, was not associated with decreased cell surface expression of viral antigens. The second mechanism of IFN-γ-mediated antiviral activity was an enhancement of CD4+T-cell-mediated cytolytic activity. We also found an in vivo role for IFN-γ in the control of persistent Friend virus infections. Neutralization of IFN-γ in persistently infected mice resulted in significantly increased levels of virus in the spleen, and a significant percentage of IFN-γ-deficient mice were unable to maintain long-term control over Friend virus infections.
Ebola Virus VP40-Induced Particle Formation and Association with the Lipid Bilayer
Authors: Jasenosky Luke D. , Neumann Gabriele , Lukashevich Igor , Kawaoka Yoshihiro 
Published: July 2002

ABSTRACT
Viral protein 40 (VP40) of Ebola virus appears equivalent to matrix proteins of other viruses, yet little is known about its role in the viral life cycle. To elucidate the functions of VP40, we investigated its ability to induce the formation of membrane-bound particles when it was expressed apart from other viral proteins. We found that VP40 is indeed able to induce particle formation when it is expressed in mammalian cells, and this process appeared to rely on a conserved N-terminal PPXY motif, as mutation or loss of this motif resulted in markedly reduced particle formation. These findings demonstrate that VP40 alone possesses the information necessary to induce particle formation, and this process most likely requires cellular WW domain-containing proteins that interact with the PPXY motif of VP40. The ability of VP40 to bind cellular membranes was also studied. Flotation gradient analysis indicated that VP40 binds to membranes in a hydrophobic manner, as NaCl at 1 M did not release the protein from the lipid bilayer. Triton X-114 phase-partitioning analysis suggested that VP40 possesses only minor features of an integral membrane protein. We confirmed previous findings that truncation of the 50 C-terminal amino acids of VP40 results in decreased association with cellular membranes and demonstrated that this deletion disrupts hydrophobic interactions of VP40 with the lipid bilayer, as well as abolishing particle formation. Truncation of the 150 C-terminal amino acids or 100 N-terminal amino acids of VP40 enhanced the protein's hydrophobic association with cellular membranes. These data suggest that VP40 binds the lipid bilayer in an efficient yet structurally complex fashion.