bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suppression of c-Myc-Induced Apoptosis by the Epstein-Barr Virus Gene Product BHRF1
Authors: Fanidi Abdallah , Hancock David C. , Littlewood Trevor D. 
Published: December 2019

ABSTRACT

Constitutive expression of the c-
myc
proto-oncogene in growth factor-deprived fibroblasts promotes proliferation and induces apoptosis. In these cells, apoptosis can be inhibited by survival factors such as insulin-like growth factor I or the
bcl-2
proto-oncogene product. Deregulated c-Myc expression is a common feature in Epstein-Barr virus-positive Burkitt’s lymphoma in which the c-
myc
gene is reciprocally translocated and placed under the control of one of the immunoglobulin loci. BHRF1 is an Epstein-Barr virus protein expressed early in the lytic cycle. BHRF1 is a member of the Bcl-2 family and has been shown to suppress apoptosis and to increase cell survival in different settings. In the present study, we report that BHRF1 inhibits c-Myc-induced apoptosis which occurs in the absence of survival factors. It does not, however, affect the capacity of c-Myc to promote cell growth. These findings demonstrate that BHRF1 has not only structural but also functional similarities to Bcl-2.
Canine Distemper Virus DNA Vaccination Induces Humoral and Cellular Immunity and Protects against a Lethal Intracerebral Challenge
Authors: Sixt Nathalie , Cardoso Alicia , Vallier Agnès , Fayolle Joël , Buckland Robin , Wild T. Fabian 
Published: December 2019

ABSTRACTWe have studied the immune responses to the two glycoproteins of theMorbilliviruscanine distemper virus (CDV) after DNA vaccination of BALB/c mice. The plasmids coding for both CDV hemagglutinin (H) and fusion protein (F) induce high levels of antibodies which persist for more than 6 months. Intramuscular inoculation of the CDV DNA induces a predominantly immunoglobulin G2a (IgG2a) response (Th1 response), whereas gene gun immunization with CDV H evokes exclusively an IgG1 response (Th2 response). In contrast, the CDV F gene elicited a mixed, IgG1 and IgG2a response. Mice vaccinated (by gene gun) with either the CDV H or F DNA showed a class I-restricted cytotoxic lymphocyte response. Immunized mice challenged intracerebrally with a lethal dose of a neurovirulent strain of CDV were protected. However, approximately 30% of the mice vaccinated with the CDV F DNA became obese in the first 2 months following the challenge. This was not correlated with the serum antibody levels.
Immediate-Early Transactivator Rta of Epstein-Barr Virus (EBV) Shows Multiple Epitopes Recognized by EBV-Specific Cytotoxic T Lymphocytes
Authors: Pepperl Sandra , Benninger-Döring Gerlinde , Modrow Susanne , Wolf Hans , Jilg Wolfgang 
Published: December 2019

ABSTRACTWe analyzed the immediate-early transactivator Rta of Epstein-Barr virus (EBV) for its role as a target for specific cytotoxic T lymphocytes (CTL). Panels of overlapping peptides covering the entire amino acid sequence of Rta were synthesized and used to induce and analyze specific CTL responses in EBV-positive donors. Using peptide-pulsed target cells, we found nine different CTL epitopes that are distributed over the entire protein sequence. One epitope restricted by HLA-A24 could be mapped to the decameric sequence DYCNVLNKEF between amino acid positions 28 and 37 of the Rta protein. A second epitope could be assigned to the same region of Rta (residues 25 to 39) and was shown to be restricted by HLA-B18. Another, minimal epitope could be mapped to the nonameric sequence ATIGTAMYK between amino acid positions 134 and 142; this peptide was restricted by HLA-A11. Another four epitopes were proven to be restricted by HLA-A2, -A3, -B61, and -Cw4 and were located between Rta residues 225 and 239, 145 and 159, 529 and 543, and 393 and 407, respectively. For two other epitopes, only the location within the Rta protein is known so far (residues 121 to 135 and 441 to 455); their exact HLA restriction patterns have not yet been identified. Using target cells infected with recombinant vaccinia virus containing the gene for Rta, we showed that six of eight Rta-specific CTL lines recognized the corresponding peptides also after endogenous processing. These data suggest that Rta comprises an important target for EBV-specific cellular cytotoxicity. Together with recent findings of other immediate-early and early proteins also acting as CTL targets, they reveal the role of proteins of the lytic cycle in the immune recognition of EBV-infected cells.
The Molecular Chaperone Calnexin Interacts with the NSP4 Enterotoxin of Rotavirus In Vivo and In Vitro
Authors: Mirazimi Ali , Nilsson Mikael , Svensson Lennart 
Published: December 2019

ABSTRACT
Calnexin is an endoplasmic reticulum (ER)-associated molecular chaperone proposed to promote folding and assembly of glycoproteins that traverse the secretory pathway in eukaryotic cells. In this study we examined if calnexin interacts with the ER-associated luminal (VP7) and transmembrane (NSP4) proteins of rotavirus. Only glycosylated NSP4 interacted with calnexin and did so in a time-dependent manner (half-life, 20 min). In vitro translation experiments programmed with gene 10 of rhesus rotavirus confirmed that calnexin recognizes only glycosylated NSP4. Castanospermine (a glucosidase I and II inhibitor) experiments established that calnexin associates only with partly deglucosylated (di- or monoglucosylated) NSP4. Furthermore, enzymatic removal of the remaining glucose residues on the N-linked glycan units was essential to disengage the NSP4-calnexin complex. Novel experiments with castanospermine revealed that glucose trimming and the calnexin-NSP4 interaction were not critical for the assembly of infectious virus.
The 3′-Untranslated Region of Hepatitis C Virus RNA Enhances Translation from an Internal Ribosomal Entry Site
Authors: Ito Takayoshi , Tahara Stanley M. , Lai Michael M. C. 
Published: December 2019

ABSTRACTTranslation of most eukaryotic mRNAs and many viral RNAs is enhanced by their poly(A) tails. Hepatitis C virus (HCV) contains a positive-stranded RNA genome which does not have a poly(A) tail but has a stretch of 98 nucleotides (X region) at the 3′-untranslated region (UTR), which assumes a highly conserved stem-loop structure. This X region binds a polypyrimidine tract-binding protein (PTB), which also binds to the internal ribosome entry site (IRES) in HCV 5′-UTR. These RNA-protein interactions may regulate its translation. We generated a set of HCV RNAs differing only in their 3′-UTRs and compared their translation efficiencies. HCV RNA containing the X region was translated three- to fivefold more than the corresponding RNAs without this region. Mutations that abolished PTB binding in the X region reduced, but did not completely abolish, enhancement in translation. The X region also enhanced translation from another unrelated IRES (from encephalomyocarditis virus RNA), but did not affect the 5′-end-dependent translation of globin mRNA in either monocistronic or bicistronic RNAs. It did not appear to affect RNA stability. The free X region added intrans, however, did not enhance translation, indicating that the translational enhancement by the X region occurs only incis. These results demonstrate that the highly conserved 3′ end of HCV RNA provides a novel mechanism for enhancement of HCV translation and may offer a target for antiviral agents.
Vaccinia Virus Protein Synthesis Has a Low Requirement for the Intact Translation Initiation Factor eIF4F, the Cap-Binding Complex, within Infected Cells
Authors: Mulder Jacqueline , Robertson Morwenna E. M. , Seamons Rachael A. , Belsham Graham J. 
Published: December 2019

ABSTRACT
The role of the cap-binding complex, eIF4F, in the translation of vaccinia virus mRNAs has been analyzed within infected cells. Plasmid DNAs, which express dicistronic mRNAs containing a picornavirus internal ribosome entry site, produced within vaccinia virus-infected cells both β-glucuronidase and a cell surface-targeted single-chain antibody (sFv). Cells expressing sFv were selected from nonexpressing cells, enabling analysis of protein synthesis specifically within the transfected cells. Coexpression of poliovirus 2A or foot-and-mouth disease virus Lb proteases, which cleaved translation initiation factor eIF4G, greatly inhibited cap-dependent protein (β-glucuronidase) synthesis. Under these conditions, internal ribosome entry site-directed expression of sFv continued and cell selection was maintained. Furthermore, vaccinia virus protein synthesis persisted in the selected cells containing cleaved eIF4G. Thus, late vaccinia virus protein synthesis has a low requirement for the intact cap-binding complex eIF4F. This may be attributed to the short unstructured 5′ noncoding regions of the vaccinia virus mRNAs, possibly aided by the presence of poly(A) at both 5′ and 3′ termini.
High-Titer Human Immunodeficiency Virus Type 1-Based Vector Systems for Gene Delivery into Nondividing Cells
Authors: Mochizuki Hideki , Schwartz Joan P. , Tanaka Koichi , Brady Roscoe O. , Reiser Jakob 
Published: December 2019

ABSTRACT
Previously we designed novel pseudotyped high-titer replication defective human immunodeficiency virus type 1 (HIV-1) vectors to deliver genes into nondividing cells (J. Reiser, G. Harmison, S. Kluepfel-Stahl, R. O. Brady, S. Karlsson, and M. Schubert, Proc. Natl. Acad. Sci. USA 93:15266–15271, 1996). Since then we have made several improvements with respect to the safety, flexibility, and efficiency of the vector system. A three-plasmid expression system is used to generate pseudotyped HIV-1 particles by transient transfection of human embryonic kidney 293T cells with a defective packaging construct, a plasmid coding for a heterologous envelope (Env) protein, and a vector construct harboring a reporter gene such as neo, ShlacZ (encoding a phleomycin resistance/β-galactosidase fusion protein), HSA (encoding mouse heat-stable antigen), or EGFP (encoding enhanced green fluorescent protein). The packaging constructs lack functional Vif, Vpr, and Vpu proteins and/or a large portion of the Env coding region as well as the 5′ and 3′ long terminal repeats, the Nef function, and the presumed packaging signal. Using G418 selection, we routinely obtained vector particles pseudotyped with the vesicular stomatitis virus G glycoprotein (VSV-G) with titers of up to 8 × 107 CFU/μg of p24, provided that a functional Tat coding region was present in the vector. Vector constructs lacking a functional Tat protein yielded titers of around 4 × 106 to 8 × 106 CFU/μg of p24. Packaging constructs with a mutation within the integrase (IN) core domain profoundly affected colony formation and expression of the reporter genes, indicating that a functional IN protein is required for efficient transduction. We explored the abilities of other Env proteins to allow formation of pseudotyped HIV-1 particles. The rabies virus and Mokola virus G proteins yielded high-titer infectious pseudotypes, while the human foamy virus Env protein did not. Using the improved vector system, we successfully transduced contact-inhibited primary human skin fibroblasts and postmitotic rat cerebellar neurons and cardiac myocytes, a process not affected by the lack of the accessory proteins.
Development of a Neutralizing Antibody Response during Acute Primary Human Immunodeficiency Virus Type 1 Infection and the Emergence of Antigenic Variants
Authors: Lewis J. , Balfe P. , Arnold C. , Kaye S. , Tedder R. S. , McKeating J. A. 
Published: December 2019

ABSTRACT
We monitored the primary humoral response to human immunodeficiency virus type 1 infection and showed that, in addition to antibodies to p24 and gp41, antigens which form the basis of most diagnostic assays, the response included a significant antibody response directed to the gp120 region of the infecting viral quasispecies. When tested in a recombinant virus neutralization assay, these antibodies were capable of inhibiting viral growth. We found the primary viral quasispecies to solely utilize the CCR-5 chemokine receptor; however, recombinant viruses differed in their cytopathology and in their sensitivity to β-chemokine inhibition of viral growth. Sequence analysis of the gp120 open reading frames showed that amino acid changes in the C1 (D→G at position 62) and C4 (V→A at position 430) regions accounted for the phenotypic differences. These data demonstrate that early in infection, polymorphism exists in envelope glycoprotein coreceptor interactions and imply that therapeutic strategies targeted at this step in the viral life cycle may lead to rapid resistance.
Epstein-Barr Virus Contributes to the Malignant Phenotype and to Apoptosis Resistance in Burkitt’s Lymphoma Cell Line Akata
Authors: Komano Jun , Sugiura Makoto , Takada Kenzo 
Published: December 2019

ABSTRACT
In the present study, we established an in vitro system representing the Burkitt’s lymphoma (BL)-type Epstein-Barr virus (EBV) infection which is characterized by expression of EBV-determined nuclear antigen 1 (EBNA-1) and absence of EBNA-2 and latent membrane protein 1 (LMP1) expression. EBV-negative cell clones isolated from the EBV-positive BL line Akata were infected with an EBV recombinant carrying a selectable marker, and the following selection culture easily yielded EBV-infected clones. EBV-reinfected clones showed BL-type EBV expression and restored the capacity for growth on soft agar and tumorigenicity in SCID mice that were originally retained in parental EBV-positive Akata cells and lost in EBV-negative subclones. Moreover, it was found that EBV-positive cells were more resistant to apoptosis than were EBV-negative cells. EBV-infected cells expressed the bcl-2 protein, through which cells might become resistant to apoptosis, at a higher level than did uninfected cells. This is the first report that BL-type EBV infection confers apoptosis resistance even in the absence of expression of LMP1 and BHRF1, both of which are known to have an antiapoptotic function. Surprisingly, transfection of the EBNA-1 gene into EBV-negative Akata clones could not restore malignant phenotypes and apoptosis resistance, thus suggesting that EBNA-1 alone was not sufficient for conferring them. Our results suggest that the persistence of EBV in BL cells is required for the cells to be more malignant and apoptosis resistant, which underlines the oncogenic role of EBV in BL genesis.
Mutations in the N Terminus of the Brome Mosaic Virus Polymerase Affect Genetic RNA-RNA Recombination
Authors: Figlerowicz M. , Nagy P. D. , Tang N. , Kao C. C. , Bujarski J. J. 
Published: December 2019

ABSTRACT
Previously, we have observed that mutations in proteins 1a and 2a, the two virally encoded components of the brome mosaic virus (BMV) replicase, can affect the frequency of recombination and the locations of RNA recombination sites (P. D. Nagy, A. Dzianott, P. Ahlquist, and J. J. Bujarski, J. Virol. 69:2547–2556, 1995; M. Figlerowicz, P. D. Nagy, and J. J. Bujarski, Proc. Natl. Acad. Sci. USA 94:2073–2078, 1997). Also, it was found before that the N-terminal domain of 2a, the putative RNA polymerase protein, participates in the interactions between 1a and 2a (C. C. Kao, R. Quadt, R. P. Hershberger, and P. Ahlquist, J. Virol. 66:6322–6329, 1992; E. O’Reilly, J. Paul, and C. C. Kao, J. Virol. 71:7526–7532, 1997). In this work, we examine how mutations within the N terminus of 2a influence RNA recombination in BMV. Because of the likely electrostatic character of 1a-2a interactions, five 2a mutants, MF1 to MF5, were generated by replacing clusters of acidic amino acids with their neutral counterparts. MF2 and MF5 retained nearly wild-type levels of 1a-2a interaction and were infectious inChenopodium quinoa. However, compared to that in wild-type virus, the frequency of nonhomologous recombination in both MF2 and MF5 was markedly decreased. Only in MF2 was the frequency of homologous recombination reduced and the occurrence of imprecise homologous recombination increased. In MF5 there was also a 3′ shift in the positions of homologous crossovers. The observed effects of MF2 and MF5 reveal that the 2a N-terminal domain participates in different ways in homologous and in nonhomologous BMV RNA recombination. This work maps specific locations within the N terminus involved in 1a-2a interaction and in recombination and further suggests that the mechanisms of the two types of crossovers in BMV are different.
Adenovirus Induction of an Interferon-Regulatory Factor during Entry into the Late Phase of Infection
Authors: Feigenblum David , Walker Robert , Schneider Robert J. 
Published: December 2019

ABSTRACTVirus infection of animal cells can induce intracellular antiviral responses mediated by the induction of interferon-regulatory transcription factors (IRFs), which bind to and control genes directed by the interferon-stimulated response element (ISRE). The purpose of this study was to determine whether adenovirus (Ad) induces IRFs during infection, because they might play a role in promoting viral pathogenesis. Here we show that after the late phase of infection, Ad induces a transcription factor related to the IRF family of factors. The IRF is induced shortly after Ad entry into late phase and is shown to stimulate ISRE-directed transcription, to require activation by protein tyrosine kinase signalling, and to be induced several hours prior to the inhibition of cell protein synthesis. Inhibition of tyrosine kinase activity blocks Ad induction and activation of the IRF. Attempts to identify the Ad-induced factor immunologically and by photo-UV cross-linking indicate that it is likely a novel member of the IRF family. Finally, several independent lines of evidence also suggest that Ad induction of the IRF might correlate with the ability of the virus to block host cell protein synthesis later during infection.
CD4+ T-Lymphocyte Depletion in Human Lymphoid Tissue Ex Vivo Is Not Induced by Noninfectious Human Immunodeficiency Virus Type 1 Virions
Authors: Sylwester A. W. , Grivel J.-C. , Fitzgerald W. , Rossio J. L. , Lifson J. D. , Margolis L. B. 
Published: December 2019

ABSTRACT
We tested infectious human immunodeficiency virus type 1 (HIV-1), noninfectious but conformationally authentic inactivated whole HIV-1 virions, and purified gp120 for the ability to induce depletion of CD4+ T cells in human lymphoid tissues ex vivo. Infectious CXCR4-tropic HIV-1, but not matched inactivated virions or gp120, mediated CD4+ T-cell depletion, consistent with mechanisms requiring productive infection.
Identification and Characterization of an RNA-Dependent RNA Polymerase Activity within the Nonstructural Protein 5B Region of Bovine Viral Diarrhea Virus
Authors: Zhong Weidong , Gutshall Lester L. , Del Vecchio Alfred M. 
Published: December 2019

ABSTRACT
Nonstructural protein 5B (NS5B) of bovine viral diarrhea virus (BVDV) contains sequence motifs that are predictive of an RNA-dependent RNA polymerase activity. We describe the expression and purification of the BVDV NS5B protein derived from an infectious cDNA clone of BVDV (NADL strain). BVDV NS5B protein was active in an in vitro RNA polymerase assay using homopolymeric RNA or BVDV minigenomic RNA templates. The major product was a covalently linked double-stranded molecule generated by a “copy-back” mechanism from the input template RNA. In addition, a nucleotide-nonspecific and template-independent terminal nucleotidyl transferase activity was observed with the BVDV NS5B preparation.
Mapping of Epitopes Exposed on Intact Human Immunodeficiency Virus Type 1 (HIV-1) Virions: a New Strategy for Studying the Immunologic Relatedness of HIV-1
Authors: Nyambi Phillipe N. , Gorny Miroslaw K. , Bastiani Lisa , van der Groen Guido , Williams Constance , Zolla-Pazner Susan 
Published: December 2019

ABSTRACTTo study the antigenic conservation of epitopes of human immunodeficiency virus type 1 (HIV-1) isolates of different clades, the abilities of human anti-HIV-1 gp120 and gp41 monoclonal antibodies (MAbs) to bind to intact HIV-1 virions were determined by a newly developed virus-binding assay. Eighteen human anti-HIV MAbs, which were directed at the V2, V3 loop, CD4-binding domain (CD4bd), C5, or gp41 regions, were used. Nine HIV-1 isolates from clades A, B, D, F, G, and H were used. Microtiter wells were coated with the MAbs, after which virus was added. Bound virus was detected after lysis by testing for p24 antigen with a noncommercial p24 enzyme-linked immunosorbent assay. The anti-V3 MAbs strongly bound the four clade B viruses and viruses from the non-B clades, although binding was weaker and more sporadic with the latter. The degrees of binding by the anti-V3 MAbs to CXCR4- and CCR5-tropic viruses were similar, suggesting that the V3 loops of these two categories of viruses are similarly exposed. The anti-C5 MAbs bound isolates of clades A, B, and D. Only weak and sporadic binding of all the viruses tested with anti-CD4bd, anti-V2, and anti-gp41 MAbs was detected. These results suggest that V3 and C5 structures are shared and well exposed on intact virions of different clades compared to the CD4bd, V2, and gp41 regions.
Requirement for CD4+ T Cells in the Friend Murine Retrovirus Neutralizing Antibody Response: Evidence for Functional T Cells in Genetic Low-Recovery Mice
Authors: Super Heidi J. , Brooks Diane , Hasenkrug Kim , Chesebro Bruce 
Published: December 2019

ABSTRACTRecovery from infection with the Friend murine leukemia retrovirus complex (FV) requires T-helper cells and cytotoxic T cells as well as neutralizing antibodies. Several host genes, including genes of the major histocompatibility complex (H-2) and anH-2-unlinked gene,Rfv-3, influence these FV-specific immune responses. (B10.A × A/Wy)F1mice, which have theH-2a/aRfv-3r/sgenotype, fail to mount a detectable FV-specific T-cell proliferative response but nevertheless produce FV-specific neutralizing immunoglobulin M (IgM) antibodies and can eliminate FV viremia. Thus, this IgM response, primarily influenced by theRfv-3gene, may be T-cell independent. To test this idea, mice were depleted of either CD4+or CD8+T-cell populations in vivo and were monitored for the effect on the neutralizing antibody response following FV infection. Surprisingly, mice in which CD4+cells were depleted showed undetectable FV-neutralizing antibody responses and high viremia levels compared to nondepleted or CD8-depleted animals. In addition to knocking out the FV antibody response, CD4+T-cell depletion reduced survival time significantly, further indicating the importance of CD4+T cells. These studies revealed the first evidence for a functional T-cell response following FV infection in these low-recovery mice and showed that CD4+T-helper cells are required for theRfv-3-controlled FV antibody response.