bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Vaccinia Virus Intermediate Transcription Factor
Authors: Sanz Patrick , Moss Bernard 
Published: December 2019

ABSTRACT
Transcription of the vaccinia virus genome is mediated by a virus-encoded multisubunit DNA-dependent RNA polymerase in conjunction with early-, intermediate-, and late-stage-specific factors. Previous studies indicated that two virus-encoded proteins (capping enzyme and VITF-1) and one unidentified cellular protein (VITF-2) are required for specific transcription of an intermediate promoter template in vitro. We have now extensively purified an additional virus-induced intermediate transcription factor with a native mass of approximately 100 kDa.
The Polyserine Tract of Herpes Simplex Virus ICP4 Is Required for Normal Viral Gene Expression and Growth in Murine Trigeminal Ganglia
Authors: Bates Patricia A. , DeLuca Neal A. 
Published: December 2019

ABSTRACT

ICP4 of herpes simplex virus (HSV) is essential for productive infection due to its central role in the regulation of HSV transcription. This study identified a region of ICP4 that is not required for viral growth in culture or at the periphery of experimentally inoculated mice but is critical for productive growth in the trigeminal ganglia. This region of ICP4 encompasses amino acids 184 to 198 and contains 13 nearly contiguous serine residues that are highly conserved among the alphaherpesviruses. A mutant in which this region is deleted (ΔSER) was able to grow on the corneas of mice and be transported back to the trigeminal ganglia. ΔSER did not grow in the trigeminal ganglia but did express low levels of several immediate-early (ICP4 and ICP27) and early (thymidine kinase [
tk
] and UL42) genes. It expressed very low levels of the late gC gene and did not appear to replicate DNA. This pattern of gene expression was similar to that observed for a
tk
mutant,
dl
sptk. Both ΔSER and
dl
sptk expressed higher levels of the latency-associated transcript (LAT) per genome earlier in infected ganglia than did the wild-type virus, KOS. However, infected ganglia from all three viruses accumulated the same level of LAT per genome at 30 days postinfection (during latency). The data suggest that the polyserine tract of ICP4 provides an activity that is required for lytic infection in ganglia to progress to viral DNA synthesis and full lytic gene expression. In the absence of this activity, higher levels of LAT per genome accumulate earlier in infection than with wild-type virus.
The Early Region 4 orf4 Protein of Human Adenovirus Type 5 Induces p53-Independent Cell Death by Apoptosis
Authors: Marcellus Richard C. , Lavoie Josée N. , Boivin Dominique , Shore Gordon C. , Ketner Gary , Branton Philip E. 
Published: December 2019

ABSTRACT
Previous studies by our group showed that infection of human and rodent cells by human adenovirus type 5 (Ad5) results in the induction of p53-independent apoptosis and cell death that are dependent upon transactivation of early region 4 (E4). To identify which E4 products are involved, studies were conducted with p53-deficient human SAOS-2 cells infected with various Ad5 E4 mutants. An E4orf6-deficient mutant was defective in cell killing, whereas another that expressed only E4orf6 and E4orf4 killed like wild-type virus, suggesting that E4orf6 may be responsible for cytotoxicity; however, a mutant expressing only E4orf4 induced high levels of cell death, indicating that this E4 product may also be able to induce cytotoxicity. To define the E4 cell death-inducing functions more precisely, cDNAs encoding individual E4 products were introduced into cells by DNA transfection in the absence of other Ad5 proteins. In cotransfections with a cDNA encoding firefly luciferase, enzymatic activity was high in all cases except with E4orf4, where luciferase levels were less than 20% of those in controls. In addition, drug selection of several cell types following transfection with retroviral vector DNA encoding individual E4 products as well as puromycin resistance yielded a large number of cell colonies except when E4orf4 was expressed. These data demonstrated that E4orf4 is the only E4 product capable of independent cell killing. Cell death induced by E4orf4 was due to apoptosis, as evidenced by 4′,6-diamidino-2-phenylindole (DAPI) staining of cell nuclei in E4orf4-expressing cells. Thus, although E4orf6 may play some role, these results suggested that E4orf4 may be the major E4 product responsible for induction of p53-independent apoptosis.
trans
-Complementation of Flavivirus RNA Polymerase Gene NS5 by Using Kunjin Virus Replicon-Expressing BHK Cells
Authors: Khromykh Alexander A. , Kenney Mark T. , Westaway Edwin G. 
Published: December 2019

ABSTRACT

A BHK cell line persistently expressing a Kunjin (KUN) virus replicon RNA (repBHK, similar to our recently described ME/76Neo BHK cell line [A. A. Khromykh and E. G. Westaway, J. Virol. 71:1497–1505, 1997]) was used for rescue and propagation of KUN viruses defective in the RNA polymerase gene (NS5). A new infectious full-length KUN virus cDNA clone, FLSDX, prepared from our previously described cDNA clone pAKUN (A. A. Khromykh and E. G. Westaway, J. Virol. 68:4580–4588, 1994) and possessing ∼10
5
-fold higher specific infectivity than that of pAKUN, was used for preparation of defective mutants. Deletions of the predicted RNA polymerase motif GDD (producing FLd
GDD
) and of one of the predicted methyltransferase motifs (
S
-adenosylmethionine [SAM] binding site, producing FLdSAM) were introduced separately into FLSDX. Transcription and transfection of FLd
GDD
and FLdSAM RNAs into repBHK cells but not into normal BHK cells resulted in their replication and the recovery of defective viruses able to replicate only in repBHK cells. Reverse transcription-PCR and sequencing analyses showed retention of the introduced deletions in the genomes of the recovered viruses. Retention of these deletions, as well as our inability to recover viruses able to replicate in normal BHK cells after prolonged incubation (for 7 days) of FLd
GDD
- or FLdSAM-transfected repBHK cells, excluded the possibility that recombination had occurred between the deleted defective NS5 genes present in transfected RNAs and the functional NS5 gene present in the repBHK cells. An RNA with a point mutation in the GDD motif (FL
GVD
) was also complemented in transfected repBHK cells, and defective virus was recovered by day 3 after transfection. However, in contrast to the results with FLd
GDD
and FLdSAM RNAs, prolonged (4 days or more) incubation of FL
GVD
RNA in normal BHK cells allowed recovery of a virus in which the
GVD
mutation had reverted via a single base change to the wild-type
GDD
sequence. Overall, these results represent the first demonstration of
trans
-complementation of defective flavivirus RNAs with deleterious deletions in the flavivirus RNA polymerase gene NS5. The complementation system described here may prove to be useful for the in vivo complementation of deletions and mutations affecting functional domains or the essential secondary structure in any of the other flavivirus nonstructural proteins.
Epstein-Barr Virus Recombinant Lacking Expression of Glycoprotein gp150 Infects B Cells Normally but Is Enhanced for Infection of Epithelial Cells
Authors: Borza Corina M. , Hutt-Fletcher Lindsey M. 
Published: December 2019

ABSTRACTGlycoprotein gp150 is a highly glycosylated protein encoded by the BDLF3 open reading frame of Epstein-Barr virus (EBV). It does not have a homolog in the alpha- and betaherpesviruses, and its function is not known. To determine whether the protein is essential for replication of EBV in vitro, a recombinant virus which lacked its expression was made. The recombinant virus had no defects in assembly, egress, binding, or infectivity for B cells or epithelial cells. Infection of epithelial cells was, however, enhanced. The glycoprotein was sensitive to digestion with a glycoprotease that digests sialomucins, but no adhesion to cells that express selectins that bind to sialomucin ligands could be detected.
Preactivation of B Lymphocytes Does Not Enhance Mouse Mammary Tumor Virus Infection
Authors: Finke Daniela , Mortezavi Laure , Acha-Orbea Hans 
Published: December 2019

ABSTRACTWe investigated whether mouse mammary tumor virus (MMTV) favors preactivated or naive B cells as targets for efficient infection. We have demonstrated previously that MMTV activates B cells upon infection. Here, we show that polyclonal activation of B cells leads instead to lower infection levels and attenuated superantigen-specific T-cell responses in vivo. This indicates that naive small resting B cells are the major targets of MMTV infection and that the activation induced by MMTV is sufficient to allow efficient infection.
Persistent Hz-1 Virus Infection in Insect Cells: Evidence for Insertion of Viral DNA into Host Chromosomes and Viral Infection in a Latent Status
Authors: Lin Chi-Long , Lee Jin-Ching , Chen Shih-Shun , Alan Wood H. , Li Ming-Liang , Li Chih-Fen , Chao Yu-Chan 
Published: December 2019

ABSTRACT
Persistent/latent viral infections of insect cells are a prominent though poorly understood phenomenon. In this study, the long-term association between the Hz-1 virus and insect host cells, conventionally referred to as persistent viral infection, is described. With the aid of a newly developed fluorescent cell-labeling system, we found that productive viral replication occurs by spontaneous viral reactivation in fewer than 0.2% of persistently infected cell lines over a 5-day period. Once viral reactivation takes place, the host cell dies. The persistently infected cells contain various amounts of viral DNA, and, in an extreme case, up to 16% of the total DNA isolated from infected cells could be of viral origin. Both pulsed-field gel electrophoresis and in situ hybridization experiments showed that some of these viral DNA molecules are inserted into the host chromosomes but that the rest of viral DNA copies are free from host chromosomes. Thus, Hz-1 virus is the first nonretroviral insect virus known to insert its genome into the host chromosome during the infection process. These data also suggest that the previously described persistent infection of Hz-1 virus in insect cells should be more accurately referred to as latent viral infection.
Microglia Express CCR5, CXCR4, and CCR3, but of These, CCR5 Is the Principal Coreceptor for Human Immunodeficiency Virus Type 1 Dementia Isolates
Authors: Albright Andrew V. , Shieh Joseph T. C. , Itoh Takayuki , Lee Benhur , Pleasure David , O’Connor Michael J. , Doms Robert W. , González-Scarano Francisco 
Published: December 2019

ABSTRACTMicroglia are the main human immunodeficiency virus (HIV) reservoir in the central nervous system and most likely play a major role in the development of HIV dementia (HIVD). To characterize human adult microglial chemokine receptors, we analyzed the expression and calcium signaling of CCR5, CCR3, and CXCR4 and their roles in HIV entry. Microglia expressed higher levels of CCR5 than of either CCR3 or CXCR4. Of these three chemokine receptors, only CCR5 and CXCR4 were able to transduce a signal in microglia in response to their respective ligands, MIP-1β and SDF-1α, as recorded by single-cell calcium flux experiments. We also found that CCR5 is the predominant coreceptor used for infection of human adult microglia by the HIV type 1 dementia isolates HIV-1DS-br, HIV-1RC-br, and HIV-1YU-2, since the anti-CCR5 antibody 2D7 was able to dramatically inhibit microglial infection by both wild-type and single-round luciferase pseudotype reporter viruses. Anti-CCR3 (7B11) and anti-CXCR4 (12G5) antibodies had little or no effect on infection. Last, we found that virus pseudotyped with the DS-br and RC-br envelopes can infect cells transfected with CD4 in conjunction with the G-protein-coupled receptors APJ, CCR8, and GPR15, which have been previously implicated in HIV entry.
Dynamics of Human Immunodeficiency Virus Type 1 Replication in Vertically Infected Infants
Authors: Luzuriaga Katherine , Wu Hulin , McManus Margaret , Britto Paula , Borkowsky William , Burchett Sandra , Smith Betsy , Mofenson Lynne , Sullivan John L. ,   the PACTG 356 Investigators
Published: December 2019

ABSTRACTPlasma human immunodeficiency virus type 1 (HIV-1) turnover and kinetics were studied in children aged 15 days to 2 years following the initiation of a triple antiretroviral drug regimen consisting of zidovudine, lamivudine, and nevirapine. HIV-1 turnover was at least as rapid as that previously described in adults; turnover rates were more rapid in infants and children aged 3 months to 2 years than in infants less than 3 months of age. These data confirm the central role of HIV-1 replication in the pathogenesis of vertical HIV-1 infection and reinforce the importance of early, potent combination therapies for the long-term control of HIV-1 replication.
Targeting of the Visna Virus Tat Protein to AP-1 Sites: Interactions with the bZIP Domains of Fos and Jun In Vitro and In Vivo
Authors: Morse B. A. , Carruth L. M. , Clements J. E. 
Published: December 2019

ABSTRACT
The visna virus Tat protein is required for efficient viral transcription from the visna virus long terminal repeat (LTR). AP-1 sites within the visna virus LTR, which can be bound by the cellular transcription factors Fos and Jun, are also necessary for Tat-mediated transcriptional activation. A potential mechanism by which the visna virus Tat protein could target the viral promoter is by protein-protein interactions with Fos and/or Jun bound to AP-1 sites in the visna virus LTR. Once targeted to the visna virus promoter, the Tat protein could then interact with basal transcription factors to activate transcription. To examine protein-protein interactions with cellular proteins at the visna virus promoter, we used an in vitro protein affinity chromatography assay and electrophoretic mobility shift assay, in addition to an in vivo two-hybrid assay, to show that the visna virus Tat protein specifically interacts with the cellular transcription factors Fos and Jun and the basal transcription factor TBP (TATA binding protein). The Tat domain responsible for interactions with Fos and Jun was localized to an alpha-helical domain within amino acids 34 to 69 of the protein. The TBP binding domain was localized to amino acids 1 to 38 of Tat, a region previously described by our laboratory as the visna virus Tat activation domain. The bZIP domains of Fos and Jun were found to be important for the interactions with Tat. Mutations within the basic domains of Fos and Jun abrogated binding to Tat in the in vitro assays. The visna virus Tat protein was also able to interact with covalently cross-linked Fos and Jun dimers. Thus, the visna virus Tat protein appears to target AP-1 sites in the viral promoter in a mechanism similar to the interaction of human T-cell leukemia virus type 1 Tax with the cellular transcription factor CREB, by binding the basic domains of an intact bZIP dimer. The association between Tat, Fos, and Jun would position Tat proximal to the viral TATA box, where the visna virus Tat activation domain could contact TBP to activate viral transcription.
Strong Human Immunodeficiency Virus (HIV)-Specific Cytotoxic T-Lymphocyte Activity in Sydney Blood Bank Cohort Patients Infected withnef-Defective HIV Type 1
Authors: Dyer Wayne B. , Ogg Graham S. , Demoitie Marie-Ange , Jin Xia , Geczy Andrew F. , Rowland-Jones Sarah L. , McMichael Andrew J. , Nixon Douglas F. , Sullivan John S. 
Published: December 2019

ABSTRACTProposals for the use of live attenuated human immunodeficiency virus (HIV) type 1 (HIV-1) as a vaccine candidate in humans have been based on the protection afforded by attenuated simian immunodeficiency virus in the macaque model. Although it is not yet known if this strategy could succeed in humans, a study of the Sydney Blood Bank Cohort (SBBC), infected with an attenuated HIV-1 quasispecies with naturalnefandnef/long terminal repeat deletions for up to 17 years, could provide insights into the long-term immunological consequences of living with an attenuated HIV-1 infection. In this study, HIV-specific cytoxic T-lymphocyte (CTL) responses in an SBBC donor and six recipients were examined over a 3-year period with enzyme-linked immunospot, tetrameric complex binding, direct CTL lysis, and CTL precursor level techniques. Strong HIV-specific CTL responses were detected in four of seven patients, including one patient with an undetectable viral load. Two of seven patients had weak CTL responses, and in one recipient, no HIV-specific CTLs were detected. High levels of circulating effector and memory HIV-specific CTLs can be maintained for prolonged periods in these patients despite very low viral loads.
Enhancement of Human Immunodeficiency Virus Type 1 Infection by the CC-Chemokine RANTES Is Independent of the Mechanism of Virus-Cell Fusion
Authors: Gordon Cynthia J. , Muesing Mark A. , Proudfoot Amanda E. I. , Power Christine A. , Moore John P. , Trkola Alexandra 
Published: December 2019

ABSTRACTWe have studied the effects of CC-chemokines on human immunodeficiency virus type 1 (HIV-1) infection, focusing on the infectivity enhancement caused by RANTES. High RANTES concentrations increase the infectivity of HIV-1 isolates that use CXC-chemokine receptor 4 for entry. However, RANTES can have a similar enhancing effect on macrophagetropic viruses that enter via CC-chemokine receptor 5 (CCR5), despite binding to the same receptor as the virus. Furthermore, RANTES enhances the infectivity of HIV-1 pseudotyped with the envelope glycoprotein of murine leukemia virus or vesicular stomatitis virus, showing that the mechanism of enhancement is independent of the route of virus-cell fusion. The enhancing effects of RANTES are not mediated via CCR5 or other known chemokine receptors and are not mimicked by MIP-1α or MIP-1β. The N-terminally modified derivative aminooxypentane RANTES (AOP-RANTES) efficiently inhibits HIV-1 infection via CCR5 but otherwise mimics RANTES by enhancing viral infectivity. There are two mechanisms of enhancement: one apparent when target cells are pretreated with RANTES (or AOP-RANTES) for several hours, and the other apparent when RANTES (or AOP-RANTES) is added during virus-cell absorption. We believe that the first mechanism is related to cellular activation by RANTES, whereas the second is an increase in virion attachment to target cells.
Adaptation of a CCR5-Using, Primary Human Immunodeficiency Virus Type 1 Isolate for CD4-Independent Replication
Authors: Kolchinsky Peter , Mirzabekov Tajib , Farzan Michael , Kiprilov Enko , Cayabyab Mark , Mooney Larissa J. , Choe Hyeryun , Sodroski Joseph 
Published: December 2019

ABSTRACTThe gp120 envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1) promotes virus entry by sequentially binding CD4 and chemokine receptors on the target cell. Primary, clinical HIV-1 isolates require interaction with CD4 to allow gp120 to bind the CCR5 chemokine receptor efficiently. We adapted a primary HIV-1 isolate, ADA, to replicate in CD4-negative canine cells expressing human CCR5. The gp120 changes responsible for the adaptation were limited to alteration of glycosylation addition sites in the V2 loop–V1-V2 stem. The gp120 glycoproteins of the adapted viruses bound CCR5 directly, without prior interaction with CD4. Thus, a major function of CD4 binding in the entry of primary HIV-1 isolates can be bypassed by changes in the gp120 V1-V2 elements, which allow the envelope glycoproteins to assume a conformation competent for CCR5 binding.
trans-Dominant Interference with Human Immunodeficiency Virus Type 1 Replication and Transmission in CD4+Cells by an Envelope Double Mutant
Authors: Chen Steve S.-L. , Lee Sheau-Fen , Chuang Chin-Kai , Raj V. Samuel 
Published: December 2019

ABSTRACTWe previously reported that a human immunodeficiency virus type 1 (HIV-1) envelope (Env) mutant with the whole cytoplasmic domain deleted, denoted mutant TC, is able to dominantly interfere with wild-type (wt) virus infectivity. In the present study, the feasibility of developing a dominant negative mutant-based genetic anti-HIV strategy targeting the gp41 cytoplasmic domain was investigated. Mutants TC and 427,TC, a TC derivative with a Trp-to-Ser substitution introduced into residue 427 in the CD4-binding site, and a series of mutants with deletions in the cytoplasmic domain, effectivelytrans-dominantly interfered with wt Env-mediated viral infectivity, as demonstrated by anenv trans-complementation assay. The syncytium formation-defective 427,TC double mutant not only inhibited heterologous LAV and ELI Env-mediated viral infectivity but also interfered with syncytium formation and infectivity mediated by the Env proteins of the two primary isolates 92BR and 92US. Stable HeLa-CD4-LTR-β-gal clones that harbored Tat-controlled expression cassettes encoding the control ΔKS, which had a deletion in theenvgene, wt, or mutantenvgene were generated. Viral transmission mediated by laboratory-adapted T-cell-tropic HXB2 and NL4-3 viruses was greatly reduced in the TC and 427,TC transfectants compared to that observed in the control ΔKS and wt transfectants. Viral replication caused by HXB2 and NL4-3 viruses and by macrophage-tropic ConB and ADA-GG viruses was delayed or reduced in human CD4+T cells transfected with the 427,TCenvconstruct compared to that observed in cells transfected with the control ΔKS or TCenvconstruct. The lack of significant interference by TC mutant was due neither to the lack of TCenvgene integration into host DNA nor to the lack of TC Env expression upon Tat induction. These results indicate that this 427,TC Env double mutant has a role in the development oftrans-dominant mutant-based genetic anti-HIV strategies.
Identification of an Internal Ribosome Entry Segment in the 5′ Region of the Mouse VL30 Retrotransposon and Its Use in the Development of Retroviral Vectors
Authors: López-Lastra Marcelo , Ulrici Sandrine , Gabus Caroline , Darlix Jean-Luc 
Published: December 2019

ABSTRACT
Mouse virus-like 30S RNAs (VL30m) constitute a family of retrotransposons, present at 100 to 200 copies, dispersed in the mouse genome. They display little sequence homology to Moloney murine leukemia virus (MoMLV), do not encode virus-like proteins, and have not been implicated in retroviral carcinogenesis. However, VL30 RNAs are efficiently packaged into MLV particles that are propagated in cell culture. In this study, we addressed whether the 5′ region of VL30m could replace the 5′ leader of MoMLV functionally in a recombinant vector construct. Our data confirm that the putative packaging sequence of VL30 is located within the 5′ region (nucleotides 362 to 1149 with respect to the cap structure) and that it can replace the packaging sequence of MoMLV. We also show that VL30m contains an internal ribosome entry segment (IRES) in the 5′ region, as do MoMLV, Friend murine leukemia virus, Harvey murine sarcoma virus, and avian reticuloendotheliosis virus type A. Our data show that both the packaging and IRES functions of the 5′ region of VL30m RNA can be efficiently used to develop retrotransposon-based vectors.