bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theiler's Virus Infection of Primary Cultures of Bone Marrow-Derived Monocytes/Macrophages
Authors: Martinat Cécile , Mena Ignacio , Brahic Michel 
Published: November 2002

ABSTRACTTheiler's virus, a murine picornavirus, causes a persistent infection of macrophage/microglial cells in the central nervous systems of SJL/J mice. Viral replication is restricted in the majority of infected cells, whereas a minority of them contain large amounts of viral RNA and antigens. For the present work, we infected primary cultures of bone marrow monocytes/macrophages from SJL/J mice with Theiler's virus. During the first 10 h postinfection (p.i.), infected monocytes/macrophages were round and covered with filopodia and contained large amounts of viral antigens throughout their cytoplasm. Later on, they were large, flat, and devoid of filopodia and they contained only small amounts of viral antigens distributed in discrete inclusions. These two types of infected cells were very reminiscent of the two types of infected macrophages found in the spinal cords of SJL/J mice. At the peak of virus production, the viral yield per cell was approximately 200 times lower than that for BHK-21 cells. Cell death occurred in the culture during the first 24 h p.i. but not thereafter. No infected cells could be detected after 4 days p.i., and the infection never spread to 100% of the cells. This restriction was unchanged by treating the medium at pH 2 but was abolished by treating it with a neutralizing alpha/beta interferon antiserum, indicating a role for this cytokine in limiting virus expression in monocyte/macrophage cultures. The role of alpha/beta interferon was confirmed by the observation that monocytes/macrophages from IFNA/BR−/−mice were fully permissive.
Induction of Autoreactive CD8+Cytotoxic T Cells during Theiler's Murine Encephalomyelitis Virus Infection: Implications for Autoimmunity
Authors: Tsunoda Ikuo , Kuang Li-Qing , Fujinami Robert S. 
Published: November 2002

ABSTRACTTheiler's murine encephalomyelitis virus (TMEV) belongs to the familyPicornaviridaeand causes demyelinating disease in the spinal cords of infected mice. Although immune responses have been shown to play an important role in demyelination, the precise effector mechanism(s) is unknown. Potentially autoreactive cytotoxic cells could contribute to the destruction. We tested whether an autoreactive cell induced by TMEV infection mediated cytotoxicity by using a 5-h51Cr release assay in SJL/J mice. Spleen cells from TMEV-infected mice were stimulated with irradiated TMEV antigen-presenting cells and used as effector cells. The effector cells differed from conventional cytotoxic T cells since these cells could kill both TMEV-infected and uninfected syngeneic or semisyngenic cell lines (PSJLSV and BxSF11gSV) but could not kill an allogeneic cell line (C57SV). The TMEV-induced autoreactive cells were also different from conventional natural killer (NK) cells or lymphokine-activated killer (LAK) cells, because they could kill neither NK cell-sensitive YAC-1 nor NK cell-resistant P815 and EL4 cells. Induction of autoreactive cells was not detected in vaccinia virus infection. The autoreactive killing required direct cell-to-cell contact and was mediated by a Fas-FasL pathway but not by a perforin pathway. The phenotype of the killer cells was CD3+CD4−CD8+. Intracerebral inoculation of the effector cells into naive mice caused meningitis and perivascular cuffing not only in the brain parenchyma but also in the spinal cord, with no evidence of viral antigen-positive cells. This is the first report demonstrating that TMEV can induce autoreactive cytotoxic cells that induce central nervous system pathology.
Mamu-A*01
Allele-Mediated Attenuation of Disease Progression in Simian-Human Immunodeficiency Virus Infection
Authors: Zhang Zhi-Qiang , Fu Tong-Ming , Casimiro Danilo R. , Davies Mary-Ellen , Liang Xiaoping , Schleif William A. , Handt Larry , Tussey Lynda , Chen Minchun , Tang Aimin , Wilson Keith A. , Trigona Wendy L. , Freed Daniel C. , Tan Charles Y. , Horton Melanie , Emini Emilio A. , Shiver John W. 
Published: November 2002

ABSTRACT

Expression of several major histocompatibility complex (MHC) class I alleles is associated with a protective effect against disease progression in both human immunodeficiency virus type 1 and simian immunodeficiency virus infection. To understand the mechanism underlying this effect, we investigated the expression of the MHC class I allele
Mamu-A*01
in simian-human immunodeficiency virus (SHIV) infection, one of the major models for evaluation of AIDS vaccine candidates. We found that disease progression was significantly delayed in
Mamu-A∗01
-positive rhesus monkeys infected with the highly pathogenic SHIV 89.6P. The delay corresponded not only to a noted
Mamu-A∗01
-restricted dominant cytotoxic T-lymphocyte (CTL) response but also to a lower viral load in lymph nodes (LN) and, importantly, to minimal destruction of LN structure during early infection. In contrast,
Mamu-A∗01
-negative monkeys exhibited massive destruction of LN structure with accompanying rapid disease progression. These data indicate that MHC class I allele-restricted CTL responses may play an important role in preservation of lymphoid tissue structure, thereby resulting in attenuation of disease progression in immunodeficiency virus infection.
Human Immunodeficiency Virus Envelope (gp120) Binding to DC-SIGN and Primary Dendritic Cells Is Carbohydrate Dependent but Does Not Involve 2G12 or Cyanovirin Binding Sites: Implications for Structural Analyses of gp120-DC-SIGN Binding
Authors: Hong Patrick W.-P. , Flummerfelt Karen B. , de Parseval Aymeric , Gurney Kevin , Elder John H. , Lee Benhur 
Published: November 2002

ABSTRACTThe calcium-dependent lectin, DC-SIGN, binds to human immunodeficiency virus (HIV) (and simian immunodeficiency virus) gp120 and mediates the binding and transfer of HIV from monocyte-derived dendritic cells (MDDCs) to permissive T cells. However, it has been recently reported that DC-SIGN binding to HIV gp120 may be carbohydrate independent. Here, we formally demonstrate that gp120 binding to DC-SIGN and MDDCs is largely if not wholly carbohydrate dependent. Endo-β-N-glucosaminidase H (EndoH) treatment of gp120-Fc under conditions that maintained wild-type CD4 binding—and the full complement of complex glycans—significantly decreased (>90%) binding to DC-SIGN expressing cell lines, as well as to MDDCs. Any residual binding of EndoH-treated gp120-Fc to DC-SIGN was completely competed off with mannan. Mutational analysis indicated that no single glycosylation site affected the ability of gp120-Fc to bind DC-SIGN. To further guide our efforts in mapping the DC-SIGN binding sites on gp120, we used two well-characterized HIV inhibitory agents (2G12 monoclonal antibody and cyanovirin) that bind to high-mannose sugars on gp120. We showed that 2G12 and DC-SIGN bound to nonoverlapping sites in gp120 because (i) 2G12 did not block soluble gp120 or virion binding to DC-SIGN, (ii) 2G12 bound to gp120-Fc that was prebound to cell surface DC-SIGN, and (iii) gp120-Fc mutants that lack glycosylation sites involved in 2G12's epitope were also fully capable of binding DC-SIGN. These data were substantiated by the inability of cyanovirin to block gp120-Fc binding to DC-SIGN. Cyanovirin has been shown to effectively compete for 2G12 binding to gp120. Indeed, high concentrations of cyanovirin dramatically enhanced gp120-Fc binding to cell surfaces in the presence or absence of DC-SIGN. We provide evidence that this enhancement may be due to cyanovirin's ability to bridge gp120 to mannosylated cell surface proteins. These results have implications for antiviral therapeutics and for ongoing efforts to finely map the glycan structures on gp120 responsible for DC-SIGN binding.
Endocytosis Is a Critical Step in Entry of Subgroup B Avian Leukosis Viruses
Authors: Diaz-Griffero Felipe , Hoschander Steven Ari , Brojatsch Jürgen 
Published: November 2002

ABSTRACTThe avian leukosis virus (ALV) entry mechanism is controversial, with evidence for and against a low-pH requirement for viral fusion. To further address this question, we tested the entry of human immunodeficiency virus type 1 (HIV-1) pseudotyped with the envelope protein of subgroup B ALV (ALV-B) in the presence of three different lysosomotropic agents. These lysosomotropic agents were able to block the entry of wild-type and pseudotyped ALV-B in two different cell lines, strongly suggesting that ALV-B requires a low-pH step for entry. ALV-B and pH-dependent Semliki Forest virus (SFV) entered cells with slower uptake kinetics than HIV-1, which is pH independent. These slow uptake rates support the theory that ALV-B utilizes endocytic pathways to enter cells. Using immunofluorescence and electron microscopy analysis, we visualized the colocalization of virus particles with the endosomal marker transferrin and demonstrated virus particles in clathrin-coated vesicles and endosome-like structures. Surprisingly, a low-pH treatment did not overcome the inhibition of ALV-B entry by lysosomotropic agents. This indicates that, in contrast to SFV, ALV-B is unable to fuse at the cellular surface, even at a low pH. Taken together, our findings suggest that endocytosis and a subsequent low-pH step are critical for successful ALV-B infection.
ICP27 Interacts with the RNA Export Factor Aly/REF To Direct Herpes Simplex Virus Type 1 Intronless mRNAs to the TAP Export Pathway
Authors: Chen I-Hsiung Brandon , Sciabica Kathryn S. , Sandri-Goldin Rozanne M. 
Published: November 2002

ABSTRACT

Herpes simplex virus type 1 (HSV-1) protein ICP27 facilitates the export of viral intronless mRNAs. ICP27 shuttles between the nucleus and cytoplasm, which has been shown to require a leucine-rich nuclear export sequence (NES). ICP27 export was reported to be sensitive to the CRM1 inhibitor leptomycin B (LMB) in HSV-1-infected cells but not in
Xenopus
oocytes, where ICP27 interacts with the export factor Aly/REF to access the TAP export pathway. Here, we show that ICP27 interacts with Aly/REF in HSV-1-infected mammalian cells and that Aly/REF stimulates export of viral intronless RNAs but does not cross-link to these RNAs. During infection, Aly/REF was no longer associated with splicing factor SC35 but moved into structures that colocalized with ICP27, suggesting that ICP27 recruits Aly/REF from spliceosomes to viral intronless RNAs. Further, ICP27 was found to interact in vivo with TAP but not with CRM1. In vitro export assays showed that ICP27 export was not sensitive to LMB but was blocked by a dominant-negative TAP deletion mutant lacking the nucleoporin interaction domain. These data suggest that ICP27 uses the TAP pathway to export viral RNAs. Interestingly, the leucine-rich N-terminal sequence was required for efficient export, even though ICP27 export was LMB insensitive. Thus, this region is required for efficient ICP27 export but does not function as a CRM1-dependent NES.
Early Evolution of the Human Immunodeficiency Virus Type 1 Subtype C Epidemic in Rural Malawi
Authors: McCormack Grace P. , Glynn Judith R. , Crampin Amelia C. , Sibande Felix , Mulawa Dominic , Bliss Lyn , Broadbent Philip , Abarca Katia , Pönnighaus Jorg M. , Fine Paul E. M. , Clewley Jonathan P. 
Published: November 2002

ABSTRACT
We have tracked the early years of the evolution of the human immunodeficiency virus type 1 (HIV-1) epidemic in a rural district of central east Africa from the first documented introductions of subtypes A, D, and C to the present predominance of subtype C. The earliest subtype C sequences ever reported are described. Blood samples were collected on filter papers from 1981 to 1984 and from 1987 to 1989 from more than 44,000 individuals living in two areas of Karonga District, Malawi. These samples included HIV-1-positive samples from 200 people. In 1982 to 1984, HIV-1 subtypes A, C, and D were all present, though in small numbers. By 1987 to 1989, 152 (90%) of a total of 168 sequences were subtype C and AC, AD, and DC recombinants had emerged. Four of the subtype C sequences from 1983 to 1984 were closely related and were found at the base of a large cluster of low diversity that by the late 1980s accounted for 40% of C sequences. The other two early C sequences fell into a separate and more diverse cluster. Three other clusters containing sequences from the late 1980s were identified. Each cluster contained at least one sample from a person who had recently arrived in the district. From 18 HIV-1-positive spouse pairs, 12 very closely related pairs of sequences were identified. We conclude that there were multiple introductions of HIV-1 with limited spread, followed by explosive growth of a subtype C cluster, probably arising from a single introduction in or before 1983.
Conjugate-Based Targeting of Recombinant Adeno-Associated Virus Type 2 Vectors by Using Avidin-Linked Ligands
Authors: Ponnazhagan Selvarangan , Mahendra Gandham , Kumar Sanjay , Thompson John A. , Castillas, Mark 
Published: November 2002

ABSTRACT
The development of targeted vectors, capable of tissue-specific transduction, remains one of the important aspects of vector modification for gene therapy applications. Recombinant adeno-associated virus type 2 (rAAV-2)-based vectors are nonpathogenic, have relatively low immunogenicity, and are capable of long-term transgene expression. AAV-2 vectors bind primarily to heparan sulfate proteoglycan (HSPG), a receptor that is present in many tissues and cell types. Because of the widespread expression of HSPG on many tissues, targeted transduction in vivo appears to be limited with AAV-2 vectors. Thus, development of strategies to achieve transductional targeting will have a profound benefit in the future application of these vectors. We report here a novel conjugate-based targeting method to enhance tissue-specific transduction of AAV-2-based vectors. The present report utilized a high-affinity biotin-avidin interaction as a molecular bridge to cross-link purified targeting ligands, produced genetically as fusion proteins to core-streptavidin, in a prokaryotic expression system. Conjugation of the bispecific targeting protein to the vector was achieved by biotinylating purified rAAV-2 without abolishing the capsid structure, internalization, and subsequent transgene expression. The tropism-modified vectors, targeted via epidermal growth factor receptor (EGFR) or fibroblast growth factor 1α receptor (FGFR1α), resulted in a significant increase in transduction efficiency of EGFR-positive SKOV3.ip1 cells and FGFR1α-positive M07e cells, respectively. Further optimization of this method of targeting should enhance the potential of AAV-2 vectors in ex vivo and in vivo gene therapy and may form the basis for developing targeting methods for other AAV serotype capsids.
Novel
N
Gene-Associated, Temperature-Independent Resistance to the Movement of
Tobacco Mosaic Virus
Vectors Neutralized by a
Cucumber Mosaic Virus
RNA1 Transgene
Authors: Canto Tomas , Palukaitis Peter 
Published: November 2002

ABSTRACT

The
N
gene conditions for resistance to
Tobacco mosaic virus
(TMV) but only below 28°C. However, a TMV-based vector expressing green fluorescent protein (TMV-GFP) showed only limited movement at 33°C in tobacco plants harboring the
N
gene and other genes cointrogressed from
Nicotiana glutinosa
. TMV-GFP moved efficiently in tobacco plants that either lacked these genes or that contained the
N
gene but were transgenic for RNA1 of
Cucumber mosaic virus
. These findings identified novel temperature-independent resistance to the movement of TMV-GFP which could be neutralized by a different viral transgene. Using the
N
gene and
nahG
gene-transgenic tobacco, we show that this novel resistance is manifested specifically by the
N
gene itself and operates via a pathway independent of salicylic acid.
Chromosome Binding Site of Latency-Associated Nuclear Antigen of Kaposi's Sarcoma-Associated Herpesvirus Is Essential for Persistent Episome Maintenance and Is Functionally Replaced by Histone H1
Authors: Shinohara Hirohiko , Fukushi Masaya , Higuchi Masaya , Oie Masayasu , Hoshi Osamu , Ushiki Tatsuo , Hayashi Jun-Ichi , Fujii Masahiro 
Published: November 2002

ABSTRACT
Latency-associated nuclear antigen 1 (LANA1) of Kaposi's sarcoma-associated herpesvirus (KSHV; human herpesvirus 8) persistently maintains a plasmid containing the KSHV latent origin of replication (oriP) as a closed circular episome in dividing cells. In this study, we investigated the involvement of chromosome binding activity of LANA1 in persistent episome maintenance. Deletion of the N-terminal 22 amino acids of LANA1 (ΔN-LANA) inhibited the interaction with mitotic chromosomes in a human cell line, and the mutant concomitantly lost activity for the long-term episome maintenance of a plasmid containing viral oriP in a human B-cell line. However, a chimera of ΔN-LANA with histone H1, a cellular chromosome component protein, rescued the association with mitotic chromosomes as well as the long-term episome maintenance of the oriP-containing plasmid. Our results suggest that tethering of KSHV episomes to mitotic chromosomes by LANA1 is crucial in mediating the long-term maintenance of viral episomes in dividing cells.
RNA Silencing of Dengue Virus Type 2 Replication in Transformed C6/36 Mosquito Cells Transcribing an Inverted-Repeat RNA Derived from the Virus Genome
Authors: Adelman Zach N. , Sanchez-Vargas Irma , Travanty Emily A. , Carlson Jon O. , Beaty Barry J. , Blair Carol D. , Olson Ken E. 
Published: November 2002

ABSTRACT

Double-stranded RNA (dsRNA) initiates cellular posttranscriptional responses that are collectively called RNA silencing in a number of different organisms, including plants, nematodes, and fruit flies. In plants, RNA silencing has been associated with protection from virus infection. In this study, we demonstrate that dsRNA-mediated interference also can act as a viral defense mechanism in mosquito cells. C6/36 (
Aedes albopictus
) cells were stably transformed with a plasmid designed to transcribe an inverted-repeat RNA (irRNA) derived from the genome of dengue virus type 2 (DEN-2) capable of forming dsRNA. Clonal cell lines were selected with an antibiotic resistance marker and challenged with DEN-2. The cell lines were classified as either susceptible or resistant to virus replication, based on the percentage of cells expressing DEN-2 envelope (E) antigen 7 days after challenge. Eight out of 18 (44%) cell lines designed to express irRNA were resistant to DEN-2 challenge, with more than 95% of the cells showing no DEN-2 antigen accumulation. One of the DEN-2-resistant cell lines, FB 9.1, was further characterized. DEN-2 genome RNA failed to accumulate in FB 9.1 cells after challenge. Northern blot hybridization detected transcripts containing transgene sequences of both sense and antisense polarity, suggesting that DEN-2-specific dsRNA was present in the cells. In addition, a class of small RNAs 21 to 25 nucleotides in length was detected that specifically hybridized to labeled sense or antisense DEN-2 RNA derived from the target region of the genome. These observations were consistent with RNA silencing as the mechanism of resistance to DEN-2 in transformed mosquito cells.
A Minimal Chimera of Human Cyclin T1 and Tat Binds TAR and Activates Human Immunodeficiency Virus Transcription in Murine Cells
Authors: Fujinaga Koh , Irwin Dan , Taube Ran , Zhang Fan , Geyer Matthias , Peterlin B. Matija 
Published: November 2002

ABSTRACT

The transcriptional elongation of human immunodeficiency virus type 1 (HIV-1) is mediated by the virally encoded transactivator Tat and its cellular cofactor, positive transcription elongation factor b (P-TEFb). The human cyclin T1 (hCycT1) subunit of P-TEFb forms a stable complex with Tat and the transactivation response element (TAR) RNA located at the 5′ end of all viral transcripts. Previous studies have demonstrated that hCycT1 binds Tat in a Zn
2+
-dependent manner via the cysteine at position 261, which is a tyrosine in murine cyclin T1. In the present study, we mutated all other cysteines and histidines that could be involved in this Zn
2+
-dependent interaction. Because all of these mutant proteins except hCycT1(C261Y) activated viral transcription in murine cells, no other cysteine or histidine in hCycT1 is responsible for this interaction. Next, we fused the N-terminal 280 residues in hCycT1 with Tat. Not only the full-length chimera but also the mutant hCycT1 with an N-terminal deletion to position 249, which retained the Tat-TAR recognition motif, activated HIV-1 transcription in murine cells. This minimal hybrid mutant hCycT1-Tat protein bound TAR RNA as well as human and murine P-TEFb in vitro. We conclude that this minimal chimera not only reproduces the high-affinity binding among P-TEFb, Tat, and TAR but also will be invaluable for determining the three-dimensional structure of this RNA-protein complex.
Mutations in the N-Terminal Domains of Nectin-1 and Nectin-2 Reveal Differences in Requirements for Entry of Various Alphaherpesviruses and for Nectin-Nectin Interactions
Authors: Struyf Frank , Martinez Wanda M. , Spear Patricia G. 
Published: November 2002

ABSTRACT

Nectin-1 and nectin-2 are related molecules that can function with different specificities as entry receptors for mammalian alphaherpesviruses through interaction with viral glycoprotein D (gD). The normal function of members of the nectin family is to mediate cell-cell adhesion through homotypic and heterotypic nectin-nectin interactions in cadherin-based adherens junctions. We examined mutations in three equivalent regions of the N-terminal V-like domains of nectin-1 and nectin-2 to test the effects on entry of various alphaherpesviruses, nectin-nectin interactions, and interactions of the mutant nectins with gD. Mutations in region I previously shown to severely impair herpes simplex virus (HSV) entry activity, but not pseudorabies virus (PRV) or bovine herpesvirus 1 (BHV-1) entry, did not reduce homotypic
trans
interactions for either nectin-1 or nectin-2 or binding of nectin-3 to nectin-1. Mutations in region II, patterned after a reported single-nucleotide polymorphism in nectin-2, enhanced intracellular accumulation of both nectin-1 and nectin-2 and had a deleterious effect on all of the activities under study. Mutations in region III previously shown to reduce homotypic
trans
interactions of nectin-2 impaired the entry of PRV and BHV-1 when introduced into either nectin-1 or nectin-2, but only the nectin-2 mutation reduced HSV entry activity. Binding of nectin-1 to nectin-3 was not affected. Effects of the nectin-1 and nectin-2 mutations on interactions with gD did not necessarily correlate with entry activity of the mutant receptors. We can conclude that structural requirements for HSV entry, PRV and BHV-1 entry, and homotypic and heterotypic
trans
interactions are all different despite the previously reported ability of HSV and HSV gD to inhibit
trans
interactions.