bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amino Acids 270 to 510 of the Severe Acute Respiratory Syndrome Coronavirus Spike Protein Are Required for Interaction with Receptor
Authors: Babcock Gregory J. , Esshaki Diana J. , Thomas William D. , Ambrosino Donna M. 
Published: April 2004

ABSTRACT

A novel coronavirus, severe acute respiratory syndrome coronavirus (SARS-CoV), has recently been identified as the causative agent of severe acute respiratory syndrome (SARS). SARS-CoV appears similar to other coronaviruses in both virion structure and genome organization. It is known for other coronaviruses that the spike (S) glycoprotein is required for both viral attachment to permissive cells and for fusion of the viral envelope with the host cell membrane. Here we describe the construction and expression of a soluble codon-optimized SARS-CoV S glycoprotein comprising the first 1,190 amino acids of the native S glycoprotein (S
1190
). The codon-optimized and native S glycoproteins exhibit similar molecular weight as determined by Western blot analysis, indicating that synthetic S glycoprotein is modified correctly in a mammalian expression system. S
1190
binds to the surface of Vero E6 cells, a cell permissive to infection, as demonstrated by fluorescence-activated cell sorter analysis, suggesting that S
1190
maintains the biologic activity present in native S glycoprotein. This interaction is blocked with serum obtained from recovering SARS patients, indicating that the binding is specific. In an effort to map the ligand-binding domain of the SARS-CoV S glycoprotein, carboxy- and amino-terminal truncations of the S
1190
glycoprotein were constructed. Amino acids 270 to 510 were the minimal receptor-binding region of the SARS-CoV S glycoprotein as determined by flow cytometry. We speculate that amino acids 1 to 510 of the SARS-CoV S glycoprotein represent a unique domain containing the receptor-binding site (amino acids 270 to 510), analogous to the S1 subunit of other coronavirus S glycoproteins.
Epistatic Effects of Immunoglobulin GM and KM Allotypes on Outcome of Infection with Hepatitis C Virus
Authors: Pandey Janardan P. , Astemborski Jacquie , Thomas David L. 
Published: April 2004

ABSTRACTImmunoglobulin GM and KM allotypes—genetic markers of γ and κ chains, respectively—are associated with immune responsiveness to several infectious pathogens and with survival in certain viral epidemics. We hypothesized that GM and KM allotypes affect the outcome of hepatitis C virus (HCV) infection. To test this hypothesis, we serologically allotyped 100 persons with well-documented clearance of HCV infection and 198 matched persistently infected persons. None of the GM or KM phenotypes by itself was associated with the clearance or persistence of HCV infection. Particular combinations of these phenotypes, however, were significantly associated with the outcome of HCV infection. Subjects with GM 1,17 5,13 and KM 1,3 phenotypes were over three times (odds ratio [OR], 3.57; 95% confidence interval [CI], 1.44 to 8.87) as likely to clear the infection as the subjects who lacked these phenotypes. This GM phenotype had a similar association with clearance in the absence of KM 3 (OR, 2.75; 95% CI, 1.21 to 6.23). The presence of GM 1,3,17 23 5,13 phenotype (in the absence of KM 3) was associated with persistence (OR, 0.21; 95% CI, 0.06 to 0.77), while its absence (in the presence of KM 1,3) was associated with the clearance of infection (OR, 2.03; 95% CI, 1.16 to 3.54). These results show epistatic interactions of genes on chromosomes 14 (GM) and 2 (KM) in influencing the outcome of an HCV infection. Further investigations involving candidate genes (GM, KM, HLA, and Fcγ receptors) and cellular and humoral immune responses to HCV epitopes are needed to understand the mechanisms underlying these associations.
Inhibition of Cellular Proteasome Activities Enhances Hepadnavirus Replication in an HBX-Dependent Manner
Authors: Zhang Zhensheng , Protzer Ulrike , Hu Zongyi , Jacob James , Liang T. Jake 
Published: April 2004

ABSTRACTThe X protein (HBX) of the hepatitis B virus (HBV) is not essential for the HBV life cycle in vitro but is important for productive infection in vivo. Our previous study suggests that interaction of HBX with the proteasome complex may underlie the pleiotropic functions of HBX. With the woodchuck model, we demonstrated that the X-deficient mutants of woodchuck hepatitis virus (WHV) are not completely replication defective, possibly behaving like attenuated viruses. In the present study, we analyzed the effects of the proteasome inhibitors on the replication of wild-type and X-negative HBV and WHV. Recombinant adenoviruses or baculoviruses expressing replicating HBV or WHV genomes have been developed as a robust and convenient system to study viral replication in tissue culture. In cells infected with either the recombinant adenovirus-HBV or baculovirus-WHV, the replication level of the X-negative construct was about 10% of that of the wild-type virus. In the presence of proteasome inhibitors, the replication of the wild-type virus was not affected, while the replication of the X-negative virus of either HBV or WHV was enhanced and restored to the wild-type level. Our data suggest that HBX affects hepadnavirus replication through a proteasome-dependent pathway.
Ex Vivo and In Vivo Biological Effects of a Truncated Form of the Receptor Tyrosine Kinase Stk When Activated by Interaction with the Friend Spleen Focus-Forming Virus Envelope Glycoprotein or by Point Mutation
Authors: Rulli Karen , Yugawa Takashi , Hanson Charlotte , Thompson Delores , Ruscetti Sandra , Nishigaki Kazuo 
Published: April 2004

ABSTRACT

The erythroleukemia-inducing Friend spleen focus-forming virus (SFFV) encodes a unique envelope protein, gp55, which interacts with the erythropoietin (Epo) receptor complex, causing proliferation and differentiation of erythroid cells in the absence of Epo. Susceptibility to SFFV-induced erythroleukemia is conferred by the
Fv-2
gene, which encodes a short form of the receptor tyrosine kinase Stk/Ron (sf-Stk) only in susceptible strains of mice. We recently demonstrated that sf-Stk becomes activated by forming a strong interaction with SFFV gp55. To examine the biological consequences of activated sf-Stk on erythroid cell growth, we prepared retroviral vectors which express sf-Stk, either in conjunction with gp55 or alone in a constitutively activated mutant form, and tested them for their ability to induce Epo-independent erythroid colonies ex vivo and disease in mice. Our data indicate that both gp55-activated sf-Stk and the constitutively activated mutant of sf-Stk induce erythroid cells from
Fv-2
-susceptible and
Fv-2
-resistant (sf-Stk null) mice to form Epo-independent colonies. Mutational analysis of sf-Stk indicated that a functional kinase domain and 8 of its 12 tyrosine residues are required for the induction of Epo-independent colonies. Further studies demonstrated that coexpression of SFFV gp55 with sf-Stk significantly extends the half-life of the kinase. When injected into
Fv-2
-resistant mice, neither the gp55-activated sf-Stk nor the constitutively activated mutant caused erythroleukemia. Surprisingly, both
Fv-2
-susceptible and -resistant mice injected with the gp55-sf-Stk vector developed clinical signs not previously associated with SFFV-induced disease. We conclude that sf-Stk, activated by either point mutation or interaction with SFFV gp55, is sufficient to induce Epo-independent erythroid colonies from both
Fv-2
-susceptible and -resistant mice but is unable to cause erythroleukemia in
Fv-2
-resistant mice.
Apoptosis Induced by the Histone Deacetylase Inhibitor FR901228 in Human T-Cell Leukemia Virus Type 1-Infected T-Cell Lines and Primary Adult T-Cell Leukemia Cells
Authors: Mori Naoki , Matsuda Takehiro , Tadano Masayuki , Kinjo Takao , Yamada Yasuaki , Tsukasaki Kunihiro , Ikeda Shuichi , Yamasaki Yoshihiro , Tanaka Yuetsu , Ohta Takao , Iwamasa Teruo , Tomonaga Masao , Yamamoto Naoki 
Published: April 2004

ABSTRACTInhibition of histone deacetylase (HDAC) activity induces growth arrest, differentiation, and, in certain cell types, apoptosis. FR901228, FK228, or depsipeptide, is an HDAC inhibitor effective in T-cell lymphomas. Adult T-cell leukemia (ATL) is caused by human T-cell leukemia virus type 1 (HTLV-1) and remains incurable. We examined whether FR901228 is effective for treatment of ATL by assessing its ability to induce apoptosis of HTLV-1-infected T-cell lines and primary leukemic cells from ATL patients. FR901228 induced apoptosis of Tax-expressing and -unexpressing HTLV-1-infected T-cell lines and selective apoptosis of primary ATL cells, especially those of patients with acute ATL. FR901228 also efficiently reduced the DNA binding of NF-κB and AP-1 in HTLV-1-infected T-cell lines and primary ATL cells and down-regulated the expression of Bcl-xLand cyclin D2, regulated by NF-κB. Although the viral protein Tax is an activator of NF-κB and AP-1, FR901228-induced apoptosis was not associated with reduced expression of Tax. In vivo use of FR901228 partly inhibited the growth of tumors of HTLV-1-infected T cells transplanted subcutaneously in SCID mice. Our results indicated that FR901228 could induce apoptosis of these cells and suppress the expression of NF-κB and AP-1 and suggest that FR901228 could be therapeutically effective in ATL.
Growth Arrest of Epithelial Cells during Measles Virus Infection Is Caused by Upregulation of Interferon Regulatory Factor 1
Authors: Yokota Shin-ichi , Okabayashi Tamaki , Yokosawa Noriko , Fujii Nobuhiro 
Published: April 2004

ABSTRACT

Natural infection with measles virus (MeV) is initiated when the virus reaches epithelial cells in the respiratory tract, oropharynx, or conjunctivae. Human epithelial cells infected with MeV frequently show growth suppression. In this study, we investigated the possible mechanisms for this suppression. The bronchiolar epithelial cell A549 showed growth arrest in G
0
/G
1
following MeV infection or treatment with gamma interferon (IFN-γ). IFN regulatory factor-1 (IRF-1) was upregulated during MeV infection, although A549 did not produce IFN-γ. Cells of the cervical squamous cell line SiHa persistently infected with various strains of MeV displayed slower growth than uninfected SiHa cells, although the growth rates varied depending on the MeV strain. Transfection of antisense-oriented IRF-1 cDNA released the MeV-infected SiHa cells from growth suppression. Although these infected cells did not produce IFN-γ and suppressed IFN-α/β-induced Jak1 phosphorylation, Jak1 was constitutively phosphorylated. The growth rates negatively correlated with levels of both IRF-1 expression and constitutively phosphorylated Jak1. These results indicate that MeV upregulates IRF-1 in a manner that is independent of IFN but dependent on the JAK/STAT pathway. This induction of IRF-1 appears to suppress cell growth, although the extent seems to vary among MeV strains.
The UL12.5 Gene Product of Herpes Simplex Virus Type 1 Exhibits Nuclease and Strand Exchange Activities but Does Not Localize to the Nucleus
Authors: Reuven Nina Bacher , Antoku Susumu , Weller Sandra K. 
Published: April 2004

ABSTRACT

The herpes simplex virus type 1 (HSV-1) alkaline nuclease, encoded by the
UL12
gene, plays an important role in HSV-1 replication, as a null mutant of
UL12
displays a severe growth defect. Although the precise in vivo role of UL12 has not yet been determined, several in vitro activities have been identified for the protein, including endo- and exonuclease activities, interaction with the HSV-1 single-stranded DNA binding protein ICP8, and an ability to promote strand exchange in conjunction with ICP8. In this study, we examined a naturally occurring N-terminally truncated version of UL12 called UL12.5. Previous studies showing that UL12.5 exhibits nuclease activity but is unable to complement a
UL12
null virus posed a dilemma and suggested that UL12.5 may lack a critical activity possessed by the full-length protein, UL12. We constructed a recombinant baculovirus capable of expressing UL12.5 and purified soluble UL12.5 from infected insect cells. The purified UL12.5 exhibited both endo- and exonuclease activities but was less active than UL12. Like UL12, UL12.5 could mediate strand exchange with ICP8 and could also be coimmunoprecipitated with ICP8. The primary difference between the two proteins was in their intracellular localization, with UL12 localizing to the nucleus and UL12.5 remaining in the cytoplasm. We mapped a nuclear localization signal to the N terminus of UL12, the domain absent from UL12.5. In addition, when UL12.5 was overexpressed so that some of the enzyme leaked into the nucleus, it was able to partially complement the UL12 null mutant.
Discovery of a Second Form of Tripartite Complex Containing gH-gL of Human Herpesvirus 6 and Observations on CD46
Authors: Mori Yasuko , Akkapaiboon Pilailuk , Yonemoto Sayoko , Koike Masato , Takemoto Masaya , Sadaoka Tomohiko , Sasamoto Yumi , Konishi Shozo , Uchiyama Yasuo , Yamanishi Koichi 
Published: April 2004

ABSTRACT
The human herpesvirus 6 (HHV-6) glycoprotein H (gH)-glycoprotein L (gL) complex associates with glycoprotein Q (gQ) (Y. Mori, P. Akkapaiboon, X. Yang, and K. Yamanishi, J. Virol. 77:2452-2458, 2003), and the gH-gL-gQ complex interacts with human CD46 (Y. Mori, X. Yang, P. Akkapaiboon, T. Okuno, and K. Yamanishi, J. Virol. 77:4992-4999, 2003). Here, we show that the HHV-6 U47 gene, which is a positional homolog of the human cytomegalovirus glycoprotein O (gO) gene, encodes a third component of the HHV-6 gH-gL-containing envelope complex. A monoclonal antibody (MAb) against the amino terminus of HHV-6 gO reacted in immunoblots with protein species migrating at 120 to 130 kDa and 74 to 80 kDa in lysates of HHV-6-infected cells and with a 74- to 80-kDa protein species in purified virions. The 80-kDa form of gO was coimmunoprecipitated with an anti-gH MAb, but an anti-gQ MAb, which coimmunoprecipitated gH, did not coprecipitate gO. Furthermore, the gH-gL-gO complex did not bind to human CD46, indicating that the complex was not a ligand for CD46. These findings suggested that the viral envelope contains at least two kinds of tripartite complexes, gH-gL-gQ and gH-gL-gO, and that the gH-gL-gO complex may play a role different from that of gH-gL-gQ during viral infection. This is the first report of two kinds of gH-gL complexes on the viral envelope in a member of the herpesvirus family.
Hepatitis C Virus Quasispecies Variability Modulates Nonstructural Protein 5A Transcriptional Activation, Pointing to Cellular Compartmentalization of Virus-Host Interactions
Authors: Pellerin Muriel , Lopez-Aguirre Yolanda , Penin François , Dhumeaux Daniel , Pawlotsky Jean-Michel 
Published: April 2004

ABSTRACT

Hepatitis C virus (HCV) behaves in infected patients as a complex mixture of genetically distinct but closely related variants referred to as a “quasispecies.” By using quasispecies analysis strategies, we showed that HCV nonstructural protein 5A (NS5A) has a quasispecies distribution in infected humans and that NS5A quasispecies undergo significant genetic evolution over time, as a result of random accumulation of nucleotide mutations during replication. Genetic evolution of the NS5A quasispecies results in sporadic amino acid changes in the protein sequence. By using the functional in vitro model of HCV NS5A transcriptional activation in
Saccharomyces cerevisiae
, we showed that natural NS5A quasispecies variants induce different levels of transcriptional activation, according to the charge of the residues (and possibly minor conformational changes) in the quasispecies variant sequence. These findings show that the accumulation of mutations on HCV genomes during replication randomly generates variant proteins with quantitatively different functional properties. The fact that each new variant protein is initially produced in a single infected hepatocyte and may or may not subsequently spread throughout the liver (depending on the replication capacities of the variant virus) points to cellular compartmentalization of virus-host interactions during chronic infection. This feature of quasispecies-distributed viruses could play an important role in various aspects of the viral life cycle and related disease.
Relative Replicative Fitness of Human Immunodeficiency Virus Type 1 Mutants Resistant to Enfuvirtide (T-20)
Authors: Lu Jing , Sista Prakash , Giguel Françoise , Greenberg Michael , Kuritzkes Daniel R. 
Published: April 2004

ABSTRACT

Resistance to enfuvirtide (ENF; T-20), a fusion inhibitor of human immunodeficiency virus type 1 (HIV-1), is conferred by mutations in the first heptad repeat of the gp41 ectodomain. The replicative fitness of recombinant viruses carrying ENF resistance mutations was studied in growth competition assays. ENF resistance mutations, selected in vitro or in vivo, were introduced into the
env
gene of HIV-1
NL4-3
by site-directed mutagenesis and expressed in HIV-1 recombinants carrying sequence tags in
nef
. The doubling time of ENF-resistant viruses was highly correlated with decreasing ENF susceptibility (
R
2
= 0.859;
P
< 0.001). Initial fitness experiments focused on mutants identified by in vitro selection in the presence of ENF (L. T. Rimsky, D. C. Shugars, and T. J. Matthews, J. Virol. 72:986-993, 1998). In the absence of drug, these mutants displayed reduced fitness compared to wild-type virus with a relative order of fitness of wild type > I37T > V38 M > D36S/V38 M; this order was reversed in the presence of ENF. Likewise, recombinant viruses carrying ENF resistance mutations selected in vivo displayed reduced fitness in the absence of ENF with a relative order of wild type > N42T > V38A > N42T/N43K ≈ N42T/N43S > V38A/N42D ≈ V38A/N42T. Fitness and ENF susceptibility were inversely correlated (
r
= −0.988;
P
< 0.001). Similar results were obtained with recombinants expressing molecularly cloned full-length
env
genes obtained from patient-derived HIV-1 isolates before and after ENF treatment. Further studies are needed to determine whether the reduced fitness of ENF-resistant viruses alters their pathogenicity in vivo.
Generation and Characterization of DNA Vaccines Targeting the Nucleocapsid Protein of Severe Acute Respiratory Syndrome Coronavirus
Authors: Kim Tae Woo , Lee Jin Hyup , Hung Chien-Fu , Peng Shiwen , Roden Richard , Wang Mei-Cheng , Viscidi Raphael , Tsai Ya-Chea , He Liangmei , Chen Pei-Jer , Boyd David A. K. , Wu T.-C. 
Published: April 2004

ABSTRACT

Severe acute respiratory syndrome (SARS) is a serious threat to public health and the economy on a global scale. The SARS coronavirus (SARS-CoV) has been identified as the etiological agent for SARS. Thus, vaccination against SARS-CoV may represent an effective approach to controlling SARS. DNA vaccines are an attractive approach for SARS vaccine development, as they offer many advantages over conventional vaccines, including stability, simplicity, and safety. Our investigators have previously shown that DNA vaccination with antigen linked to calreticulin (CRT) dramatically enhances major histocompatibility complex class I presentation of linked antigen to CD8
+
T cells. In this study, we have employed this CRT-based enhancement strategy to create effective DNA vaccines using SARS-CoV nucleocapsid (N) protein as a target antigen. Vaccination with naked CRT/N DNA generated the most potent N-specific humoral and T-cell-mediated immune responses in vaccinated C57BL/6 mice among all of the DNA constructs tested. Furthermore, mice vaccinated with CRT/N DNA were capable of significantly reducing the titer of challenging vaccinia virus expressing the N protein of the SARS virus. These results show that a DNA vaccine encoding CRT linked to a SARS-CoV antigen is capable of generating strong N-specific humoral and cellular immunity and may potentially be useful for control of infection with SARS-CoV.
Expression of an E1A/E7 Chimeric Protein Sensitizes Tumor Cells to Killing by Activated Macrophages but Not NK Cells
Authors: Miura Tanya A. , Li Han , Morris Kristin , Ryan Sharon , Hembre Kristine , Cook James L. , Routes John M. 
Published: April 2004

ABSTRACTAdenovirus (Ad) E1A and human papillomavirus (HPV) E7 express homologous conserved regions (CRs) that mediate their shared biological functions. Despite their similarities, the expression of E1A sensitizes tumor cells to killing by NK cells and macrophages but the expression of E7 does not, a factor that may contribute to the dissimilar oncogenicities of Ad and HPV. This study was undertaken to define molecular differences between E1A and E7 that are responsible for the ability of E1A and the inability of E7 to sensitize cells to killing by NK cells and macrophages. Genetic mapping studies using human fibrosarcoma cells (H4) that stably expressed mutant forms of E1A showed that only those forms of E1A that interacted with the transcriptional coadaptor protein p300 sensitized cells to killing by NK cells and macrophages. E7 lacks the N-terminal p300-binding region present in E1A. Therefore, a chimericE1A/E7gene was constructed that included the N terminus and the CR1 (p300-binding) domain of E1A fused to CR2 and the C-terminal sequences of E7. The E1A/E7 protein interacted with p300 and pRb and immortalized primary mouse embryo fibroblasts (MEF). The expression of E1A/E7 sensitized H4 and MEF cells to killing by activated macrophages but not to killing by NK cells. Therefore, N-terminal differences between E1A and E7 that map to the E1A-p300 binding region accounted for differences in their abilities to sensitize cells to killing by macrophages. However, regions in addition to the E1A-p300 binding region are required to sensitize cells to killing by NK cells.
The 3′ Untranslated Region of Tobacco Necrosis Virus RNA Contains a Barley Yellow Dwarf Virus-Like Cap-Independent Translation Element
Authors: Shen Ruizhong , Miller W. Allen 
Published: April 2004

ABSTRACT

RNAs of many viruses are translated efficiently in the absence of a 5′ cap structure. The tobacco necrosis virus (TNV) genome is an uncapped, nonpolyadenylated RNA whose translation mechanism has not been well investigated. Computational analysis predicted a cap-independent translation element (TE) within the 3′ untranslated region (3′ UTR) of TNV RNA that resembles the TE of barley yellow dwarf virus (BYDV), a luteovirus. Here we report that such a TE does indeed exist in the 3′ UTR of TNV strain D. Like the BYDV TE, the TNV TE (i) functions both in vitro and in vivo, (ii) requires additional sequence for cap-independent translation in vivo, (iii) has a similar secondary structure and the conserved sequence CGGAUCCUGGGAAACAGG, (iv) is inactivated by a four-base duplication in this conserved sequence, (v) can function in the 5′ UTR, and (vi) when located in its natural 3′ location, may form long-distance base pairing with the viral 5′ UTR that is conserved and probably required. The TNV TE differs from the BYDV TE by having only three helical domains instead of four. Similar structures were found in all members of the
Necrovirus
genus of the
Tombusviridae
family, except satellite tobacco necrosis virus, which harbors a different 3′ cap-independent translation domain. The presence of the BYDV-like TE in select genera of different families indicates that phylogenetic distribution of TEs does not follow standard viral taxonomic relationships. We propose a new class of cap-independent TE called BYDV-like TE.