bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hepatitis A Virus-Specific Immunoglobulin A Mediates Infection of Hepatocytes with Hepatitis A Virus via the Asialoglycoprotein Receptor
Authors: Dotzauer Andreas , Gebhardt Ulrike , Bieback Karen , Göttke Ulrich , Kracke Anja , Mages Jörg , Lemon Stanley M. , Vallbracht Angelika 
Published: July 2002

ABSTRACTThe mechanisms underlying the hepatotropism of hepatitis A virus (HAV) and the relapsing courses of HAV infections are unknown. In this report, we show for a mouse hepatocyte model that HAV-specific immunoglobulin A (IgA) mediates infection of hepatocytes with HAV via the asialoglycoprotein receptor, which binds and internalizes IgA molecules. Proof of HAV infection was obtained by detection of HAV minus-strand RNA, which is indicative for virus replication, and quantification of infectious virions. We demonstrate that human hepatocytes also ingest HAV–anti-HAV IgA complexes by the same mechanism, resulting in infection of the cells, by using the HepG2 cell line and primary hepatocytes. The relevance of this surrogate receptor mechanism in HAV pathogenesis lies in the fact that HAV, IgA, and antigen-IgA complexes use the same pathway within the organism, leading from the gastrointestinal tract to the liver via blood and back to the gastrointestinal tract via bile fluid. Therefore, HAV-specific IgA antibodies produced by gastrointestinal mucosa-associated lymphoid tissue may serve as carrier and targeting molecules, enabling and supporting HAV infection of IgA receptor-positive hepatocytes and, in the case of relapsing courses, allowing reinfection of the liver in the presence of otherwise neutralizing antibodies, resulting in exacerbation of liver disease.
Establishment and Characterization of Molecular Clones of Porcine Endogenous Retroviruses Replicating on Human Cells
Authors: Czauderna Frank , Fischer Nicole , Boller Klaus , Kurth Reinhard , Tönjes Ralf R. 
Published: July 2002

ABSTRACTThe use of pig xenografts is being considered to alleviate the shortage of allogeneic organs for transplantation. In addition to the problems overcoming immunological and physiological barriers, the existence of numerous porcine microorganisms poses the risk of initiating a xenozoonosis. Recently, different classes of type C porcine endogenous retoviruses (PERV) which are infectious for human cells in vitro have been partially described. We therefore examined whether completely intact proviruses exist that produce infectious and replication-competent virions. Several proviral PERV sequences were cloned and characterized. One molecular PERV class B clone, PERV-B(43), generated infectious particles after transfection into human 293 cells. A second clone, PERV-B(33), which was highly homologous to PERV-B(43), showed a G-to-A mutation in the first start codon (Met to Ile) of theenvgene, preventing this provirus from replicating. However, a genetic recombinant, PERV-B(33)/ATG, carrying a restoredenvstart codon, became infectious and could be serially passaged on 293 cells similar to virus clone PERV-B(43). PERV protein expression was detected 24 to 48 h posttransfection (p.t.) using cross-reacting antiserum, and reverse transcriptase activity was found at 12 to 14 days p.t. The transcriptional start and stop sites as well as the splice donor and splice acceptor sites of PERV mRNA were mapped, yielding a subgenomicenvtranscript of 3.1 kb. PERV-B(33) and PERV-B(43) differ in the number of copies of a 39-bp segment in the U3 region of the long terminal repeat. Strategies to identify and to specifically suppress or eliminate those proviruses from the pig genome might help in the production of PERV-free animals.
Targeted Disruption of theCeacam1(MHVR) Gene Leads to Reduced Susceptibility of Mice to Mouse Hepatitis Virus Infection
Authors: Blau Dianna M. , Turbide Claire , Tremblay Michel , Olson Melanie , Létourneau Stéphanie , Michaliszyn Eva , Jothy Serge , Holmes Kathryn V. , Beauchemin Nicole 
Published: July 2002

ABSTRACTThe CEACAM1 glycoproteins (formerly called biliary glycoproteins; BGP, C-CAM, CD66a, or MHVR) are members of the carcinoembryonic antigen family of cell adhesion molecules. In the mouse, splice variants of CEACAM1 have either two or four immunoglobulin (Ig) domains linked through a transmembrane domain to either a short or a long cytoplasmic tail. CEACAM1 has cell adhesion activity and acts as a signaling molecule, and long-tail isoforms inhibit the growth of colon and prostate tumor cells in rodents. CEACAM1 isoforms serve as receptors for several viral and bacterial pathogens, including the murine coronavirus mouse hepatitis virus (MHV) andHaemophilus influenzae,Neisseria gonorrhoeae,andNeisseria meningitidisin humans. To elucidate the mechanisms responsible for the many biological activities of CEACAM1, we modified the expression of the mouseCeacam1gene in vivo. Manipulation of theCeacam1gene in mouse embryonic stem cells that contained theCeacam1aallele yielded a partial knockout. We obtained one line of mice in which the insert in theCeacam1agene had sustained a recombination event. This resulted in the markedly reduced expression of the two CEACAM1a isoforms with four Ig domains, whereas the expression of the two isoforms with two Ig domains was doubled relative to that in wild-type BALB/c (+/+) mice. Homozygous (p/p)Ceacam1a-targeted mice (Ceacam1aΔ4D) had no gross tissue abnormalities and were viable and fertile; however, they were more resistant to MHV A59 infection and death than normal (+/+) mice. Following intranasal inoculation with MHV A59, p/p mice developed markedly fewer and smaller lesions in the liver than +/+ or heterozygous (+/p) mice. The titers of virus produced in the livers were 50- to 100-fold lower in p/p mice than in +/p or +/+ mice. p/p mice survived a dose 100-fold higher than the lethal dose of virus for +/+ mice. +/p mice were intermediate between +/+ and p/p mice in susceptibility to liver damage, virus growth in liver, and susceptibility to killing by MHV.Ceacam1a-targeted mice provide a new model to study the effects of modulation of receptor expression on susceptibility to MHV infection in vivo.
Mutational Analysis of the Repeated Open Reading Frames, ORFs 63 and 70 and ORFs 64 and 69, of Varicella-Zoster Virus
Authors: Sommer Marvin H. , Zagha Edward , Serrano Oscar K. , Ku Chia Chi , Zerboni Leigh , Baiker Armin , Santos Richard , Spengler Mary , Lynch Jennifer , Grose Charles , Ruyechan William , Hay John , Arvin Ann M. 
Published: July 2002

ABSTRACT

Varicella-zoster virus (VZV) open reading frame 63 (ORF63), located between nucleotides 110581 and 111417 in the internal repeat region, encodes a nuclear phosphoprotein which is homologous to herpes simplex virus type 1 (HSV-1) ICP22 and is duplicated in the terminal repeat region as ORF70 (nucleotides 118480 to 119316). We evaluated the role of ORFs 63 and 70 in VZV replication, using recombinant VZV cosmids and PCR-based mutagenesis to make single and dual deletions of these ORFs. VZV was recovered within 8 to 10 days when cosmids with single deletions were transfected into melanoma cells along with the three intact VZV cosmids. In contrast, VZV was not detected in transfections carried out with a dual deletion cosmid. Infectious virus was recovered when ORF63 was cloned into a nonnative
Avr
II site in this cosmid, confirming that failure to generate virus was due to the dual ORF63/70 deletion and that replication required at least one gene copy. This requirement may be related to our observation that ORF63 interacts directly with ORF62, the major immediate-early transactivating protein of VZV. ORF64 is located within the inverted repeat region between nucleotides 111565 and 112107; it has some homology to the HSV-1 Us10 gene and is duplicated as ORF69 (nucleotides 117790 to 118332). ORF64 and ORF69 were deleted individually or simultaneously using the VZV cosmid system. Single deletions of ORF64 or ORF69 yielded viral plaques with the same kinetics and morphology as viruses generated with the parental cosmids. The dual deletion of ORF64 and ORF69 was associated with an abnormal plaque phenotype characterized by very large, multinucleated syncytia. Finally, all of the deletion mutants that yielded recombinants retained infectivity for human T cells in vitro and replicated efficiently in human skin in the SCIDhu mouse model of VZV pathogenesis.
Human Immunodeficiency Virus Type 1 IIIB Selected for Replication In Vivo Exhibits Increased Envelope Glycoproteins in Virions without Alteration in Coreceptor Usage: Separation of In Vivo Replication from Macrophage Tropism
Authors: Miller Eric D. , Duus Karen M. , Townsend Michael , Yi Yanjie , Collman Ronald , Reitz Marvin , Su Lishan 
Published: July 2002

ABSTRACTAnalysis of viral replication and pathogenicity after in vivo selection of human immunodeficiency virus type 1 (HIV-1) attenuated in vitro will help to define the functions involved in replication and pathogenesis in vivo. Using the SCID-hu Thy/Liv mouse and human fetal thymus organ culture as in vivo models, we previously defined HIV-1envdeterminants (HXB2/LW) which were reverted for replication in vivo (L. Su et al., Virology 227:46–52, 1997). In this study, we examined the replication of four highly related HIV-1 clones directly derived from Lai/IIIB or after selection in vivo to investigate the envelope gp120 determinants associated with replication in macrophages and in the thymus models in vivo. The LW/C clone derived from the IIIB-infected laboratory worker and HXB2/LW both efficiently infected monocyte-derived macrophages (MDM) and the human thymus. Although the laboratory worker (LW) isolates showed altered tropism from IIIB, they still predominantly used CXCR4 as coreceptors for infecting peripheral blood mononuclear cells, macrophages, and the thymus. Interestingly, a single amino acid mutation in the V3 loop associated with resistance to neutralizing antibodies was also essential for the replication activity of the LW virus in the thymus models but not for its activity in infecting MDM. The LW virions were equally sensitive to a CXCR4 antagonist. We further demonstrated that the LW HIV-1 isolate selected in vivo produced more infectious viral particles that contained higher levels of the Env protein gp120. Thus, selection of the laboratory-attenuated Lai/IIIB isolate in vivo leads to altered tropism but not coreceptor usage of the virus. The acquired replication activity in vivo is correlated with an early A-to-T mutation in the V3 loop and increased virion association of HIV-1 Env gp120, but it is genetically separable from the acquired replication activity in macrophages.
Folding of Hepatitis C Virus E1 Glycoprotein in a Cell-Free System
Authors: Merola Marcello , Brazzoli Michela , Cocchiarella Fabienne , Heile Jens M. , Helenius Ari , Weiner Amy J. , Houghton Michael , Abrignani Sergio 
Published: July 2002

ABSTRACT
The hepatitis C virus (HCV) envelope proteins, E1 and E2, form noncovalent heterodimers and are leading candidate antigens for a vaccine against HCV. Studies in mammalian cell expression systems have focused primarily on E2 and its folding, whereas knowledge of E1 folding remains fragmentary. We used a cell-free in vitro translation system to study E1 folding and asked whether the flanking proteins, Core and E2, influence this process. We translated the polyprotein precursor, in which the Core is N-terminal to E1, and E2 is C-terminal, and found that when the core protein was present, oxidation of E1 was a slow, E2-independent process. The half-time for E1 oxidation was about 5 h in the presence or absence of E2. In contrast with previous reports, analysis of three constructs of different lengths revealed that the E2 glycoprotein undergoes slow oxidation as well. Unfolded or partially folded E1 bound to the endoplasmic reticulum chaperones calnexin and (with lower efficiency) calreticulin, whereas no binding to BiP/GRP78 or GRP94 could be detected. Release from calnexin and calreticulin was used to assess formation of mature E1. When E1 was expressed in the absence of Core and E2, its oxidation was impaired. We conclude that E1 folding is a process that is affected not only by E2, as previously shown, but also by the Core. The folding of viral proteins can thus depend on complex interactions between neighboring proteins within the polyprotein precursor.
Residual Viral Replication during Antiretroviral Therapy Boosts Human Immunodeficiency Virus Type 1-Specific CD8+T-Cell Responses in Subjects Treated Early after Infection
Authors: Ortiz Gabriel M. , Hu Jennifer , Goldwitz Joshua A. , Chandwani Rohit , Larsson Marie , Bhardwaj Nina , Bonhoeffer Sebastian , Ramratnam Bharat , Zhang Linqi , Markowitz Martin M. , Nixon Douglas F. 
Published: July 2002

ABSTRACTHuman immunodeficiency virus type 1 (HIV-1)-infected subjects treated early after infection have preserved HIV-1-specific CD4+T-cell function. We studied the effect of highly active antiretroviral therapy (HAART) on the frequency of HIV-1-specific CD8+T cells in patients treated during early (n= 31) or chronic (n= 23) infection. The degree of viral suppression and time of initiation of treatment influenced the magnitude of the CD8+T-cell response. HIV-1-specific CD8+T cells can increase in number after HAART in subjects treated early after infection who have episodes of transient viremia.
Identification of the Lymphocytic Choriomeningitis Virus (LCMV) Proteins Required To Rescue LCMV RNA Analogs into LCMV-Like Particles
Authors: Lee Ki Jeong , Perez Mar , Pinschewer Daniel D. , de la Torre Juan Carlos 
Published: July 2002

ABSTRACT

We have used a reverse genetic approach to identify the viral proteins required for packaging and assembly of the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV). Plasmids encoding individual LCMV proteins under the control of an RNA polymerase II promoter were cotransfected with a plasmid containing an LCMV minigenome (MG). Intracellular synthesis of the LCMV MG was driven by T7 RNA polymerase whose expression was also mediated by a Pol II promoter. The supernatant from transfected cells was passaged onto fresh cells that were subsequently infected with LCMV to provide the minimal viral
trans
-acting factors, NP and L, that are required for LCMV MG RNA replication and expression. Reconstitution of LCMV-specific packaging and passage was detected by expression of the chloramphenicol acetyl transferase (CAT) reporter gene present in the MG. NP and L did not direct detectable levels of MG passage. Addition of Z and GP resulted in high levels of passage of CAT activity, which could be prevented by LCMV neutralizing antibodies. Passage of LCMV MG was inhibited by omission of either GP or Z.
Human Monocytic Cell Lines Transformed In Vitro by Epstein-Barr Virus Display a Type II Latency and LMP-1-Dependent Proliferation
Authors: Masy Eric , Adriaenssens Eric , Montpellier Claire , Crépieux Pascale , Mougel Alexandra , Quatannens Brigitte , Goormachtigh Gautier , Faumont Nathalie , Meggetto Fabienne , Auriault Claude , Groux Hervé , Coll Jean 
Published: July 2002

ABSTRACTEpstein-Barr virus (EBV) classically infects and transforms B lymphocytes in vitro, yielding lymphoblastoid cell lines (LCLs). In contrast to other herpesviruses, EBV is not described as an infectious agent for monocytes. However, recent papers described in vitro infection of monocytes leading to abortive or transient viral expression. In the present study, we report the characterization of E1, a monocytic cell line infected and transformed by EBV. This cell line was derived from an LCL by a drastic electroporation and selection of neomycin-resistant cells, unfavorable to B-cell outgrowth. E1 expressed surface molecules of monocytic lineage (CD14, major histocompatibility complex class II, and CD80) and the c-fmsgene, a highly specific marker for the monocytic lineage. This cell line is able to phagocytose and secrete proinflammatory monokines tumor necrosis factor alpha, interleukin-6 (IL-6), and IL-8. E1 cells are tumorigenic after injection in nude mice, and a monocytic cell line obtained from one of these tumors (TE1) displayed immunophenotype and functional properties similar to those of E1. We detected the presence of the EBV genome in both cell lines, as well as expression of theEBNA-1andLMP-1, but notEBNA-2, viral genes, characteristic of a type II latency. LMP-1 influences the phenotype of these monocytic cell lines, as demonstrated by down-regulation of cell proliferation and membrane intercellular adhesion molecule 1 expression due to anLMP-1antisense strategy. This is the first description of a latently infected human monocytic cell line and the first direct demonstration of an instrumental role for LMP-1 in the proliferation of EBV-transformed cell lines expressing a type II latency.
The UL48 Tegument Protein of Pseudorabies Virus Is Critical for Intracytoplasmic Assembly of Infectious Virions
Authors: Fuchs Walter , Granzow Harald , Klupp Barbara G. , Kopp Martina , Mettenleiter Thomas C. 
Published: July 2002

ABSTRACT
The pseudorabies virus (PrV) homolog of the tegument protein encoded by the UL48 gene of herpes simplex virus type 1 (HSV-1) was identified by using a monospecific rabbit antiserum against a bacterial fusion protein. UL48-related polypeptides of 53, 55, and 57 kDa were detected in Western blots of infected cells and purified virions. Immunofluorescence studies demonstrated that the PrV UL48 protein is predominantly localized in the cytoplasm but is also found in the nuclei of infected cells. Moreover, it is a constituent of extracellular virus particles but is absent from primary enveloped perinuclear virions. In noncomplementing cells, a UL48-negative PrV mutant (PrV-ΔUL48) exhibited delayed growth and significantly reduced plaque sizes and virus titers, deficiencies which were corrected in UL48-expressing cells. RNA analyses indicated that, like its HSV-1 homolog, the PrV UL48 protein is involved in regulation of immediate-early gene expression. However, the most salient effect of the UL48 gene deletion was a severe defect in virion morphogenesis. Late after infection, electron microscopy of cells infected with PrV-ΔUL48 revealed retention of newly formed nucleocapsids in the cytoplasm, whereas enveloped intracytoplasmic or extracellular complete virions were only rarely observed. In contrast, capsidless particles were produced and released in great amounts. Remarkably, the intracytoplasmic capsids were labeled with antibodies against the UL36 and UL37 tegument proteins, whereas the capsidless particles were labeled with antisera directed against the UL46, UL47, and UL49 tegument proteins. These findings suggested that the UL48 protein is involved in linking capsid and future envelope-associated tegument proteins during virion formation. Thus, like its HSV-1 homolog, the UL48 protein of PrV functions in at least two different steps of the viral life cycle. The drastic inhibition of virion formation in the absence of the PrV UL48 protein indicates that it plays an important role in virion morphogenesis prior to secondary envelopment of intracytoplasmic nucleocapsids. However, the UL48 gene of PrV is not absolutely essential, and concomitant deletion of the adjacent tegument protein gene UL49 also did not abolish virus replication in cell culture.
Metal Ion Chelates of Lipophilic Alkyl Diazinyl Ketoximes as Hydrolytic Catalysts
Authors: Cibulka Radek , Hampl František , Martinů Tomáš , Mazáč Jiří , Totevová Sonja , Liška František 
Published: July 2002

A series of lipophilic dodecyl hetaryl ketoximes (hetaryl = pyridin-2-yl, pyridazin-3-yl, pyrimidin-2-yl, pyrimidin-4-yl, pyrazin-2-yl as well as their methyl hetaryl homologues was synthesized and hydrolytic activity of their chelates with Co2+, Ni2+, Cu2+ and Zn2+ in a micellar matrix of hexadecyltrimethylammonium bromide or in homogeneous aqueous solutions was investigated using 4-nitrophenyl acetate, 4-nitrophenyl hexanoate and 4-nitrophenyl diphenyl phosphate as model substrates. While Co2+ and Cu2+ chelates are almost inactive, those of Ni2+ and Zn2+ exhibit considerable activity. None of the studied chelates promotes hydrolysis of the used phosphate. The effective species are chelates of the metal : ligand stoichiometry 1 : 3 and 1 : 1 with Ni2+ and Zn2+, respectively, when the ester cleavage proceeds in the micellar matrix. The 1 : 2 stoichiometry was found in aqueous solutions of Ni2+ and Zn2+ chelates of methyl ketoximes.
Bioenergetic constraints on tactical decision making in middle distance running
Authors: Jones A M , Whipp B J 
Published: July 2002

Background: The highest velocity that a runner can sustain during middle distance races is defined by the intersection of the runner's individual velocity-time curve and the distance-time curve. The velocity-time curve is presumably fixed at the onset of a race; however, whereas the race distance is ostensibly fixed, the actual distance-time curve is not. That is, it is possible for a runner to run further than the race distance if he or she runs wide on bends in track races. In this instance, the point of intersection of the individual velocity-time curve and the distance-time curve will move downwards and to the right, reducing the best average velocity that can be sustained for the distance.Methods: To illustrate this point, the race tactics used by the gold and silver medallists at 800 m and 5000 m in the Sydney Olympics were analysed. The paths taken by the runners were carefully tracked and the total distance they covered during the races and the average velocity they sustained over the distances they actually covered were calculated.Results: In both the Olympic 800 m and 5000 m finals, for example, the winner was not the runner who ran at the highest average velocity in the race. Rather, the winners of these races were able to husband their metabolic resources to better effect by running closer to the actual race distance.Conclusions: Race results in middle distance running events are dependent not just on the energetic potential of the runners at the start of the race and their strategy for pace allocation, but also on the effect of their tactical approach to positioning on the total distance covered in the race. Middle distance runners should be conscious of minimising the distance covered in races if they wish to optimise their performance.
A GEOMETRIC APPROACH TO THE PHASE TRANSITIONS
Authors: DEMIRTÜRK SEMRA , GÜNDÜÇ YIĞIT 
Published: July 2002

In this work, we have proposed a new geometrical method for calculating the critical temperature and critical exponents by introducing a set of bond breaking probability values. The probability value Pc corresponding to the Coniglio–Klein probability for the transition temperature is obtained among this set of trial probabilities. Critical temperature, thermal and magnetic exponents are presented for d = 2 and d = 3, q = 2 Potts model and for the application of the method to the system with first order phase transition, q = 7 Potts model on different size lattices are employed. The advantage of this method can be that the bond breaking probability can be applied, where the clusters are defined on a set of dynamic variables, which are different from the dynamic quantities of the actual Hamiltonian or the action of the full system. An immediate application can be to use the method on finite temperature lattice gauge theories.