bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in the Extracellular Envelope Glycoprotein of Variants That Evolve during the Course of Simian Immunodeficiency Virus SIVMne Infection Affect Neutralizing Antibody Recognition, Syncytium Formation, and Macrophage Tropism but Not Replication, Cytopathicity, or CCR-5 Coreceptor Recognition
Authors: Rudensey Lyle M. , Kimata Jason T. , Long E. Michelle , Chackerian Bryce , Overbaugh Julie 
Published: December 2019

ABSTRACT
Simian immunodeficiency virus SIVMne, like human immunodeficiency virus, evolves from a macrophage-tropic, non-syncytium-inducing virus at early times in infection to a T-cell-tropic, syncytium-inducing, cytopathic virus population over the course of progression to AIDS. Because the viruses isolated late in SIVMne infection of macaques include a complex mixture of variants, the viral determinants of such phenotypic changes have not been defined. To identify genetic changes that are important to virus evolution in the host, we constructed chimeric viruses by introducing variant envelope genes representative of proviruses throughout the course of infection and disease into the SIVMne parental clone (SIVMneCL8) that infected the macaque. The chimeric viruses expressed sequences encoding the surface unit of the envelope glycoprotein (Env-SU) of variants cloned between 35 and 170 weeks postinfection. The chimera with Env-SU from 35 weeks postinfection encoded only four changes in V1 compared to SIVMneCL8, whereas the chimeras encoding Env-SU from variants isolated later in infection encoded progressively more mutations both in V1 and elsewhere. Like SIVMneCL8, the chimeras were infectious for CEMx174 cells and macaque peripheral blood mononuclear cells. However, in contrast to SIVMneCL8, the chimeric viruses did not infect macaque macrophages, although each retained the ability to recognize the CCR-5 coreceptor. Thus, these data provide direct evidence that changes which evolve in Env-SU during the course of SIVMne infection do not alter CCR-5 interactions. Viruses encoding Env-SU from the latest times in infection (121 to 170 weeks postinfection), after disease was apparent, were syncytium inducing. However, these viruses were not highly cytopathic, suggesting that additional viral determinants may be required for the rapidly replicating, cytopathic phenotype of the uncloned mixed variant population. Changes in Env-SU did allow the virus to escape serum neutralizing antibodies that recognized the SIVMneCL8 parent. Moreover, the chimera encoding the Env-SU of a virus from 35 weeks postinfection, which differed from SIVMneCL8 only in V1, was not sensitive to neutralization by infected macaque sera, suggesting that V1 may define a portion of the principal neutralizing determinant for SIVMne. Together, these data suggest that SIV variants with changes in the Env-SU may be selected primarily by virtue of their ability to escape neutralizing antibody recognition.
Antibody-Dependent Cellular Cytotoxicity Directed against Cells Expressing Human Immunodeficiency Virus Type 1 Envelope of Primary or Laboratory-Adapted Strains by Human and Chimpanzee Monoclonal Antibodies of Different Epitope Specificities
Authors: Alsmadi Osama , Tilley Shermaine A. 
Published: December 2019

ABSTRACTThe characteristics of antibody-dependent cellular cytotoxicity (ADCC) directed by a panel of human and chimpanzee antienvelope (anti-Env) monoclonal antibodies (MAbs) of different epitope specificities were studied; this was accomplished by using target cells expressing human immunodeficiency virus type 1 (HIV-1) Envs of either primary or laboratory-adapted strains. Human MAbs of similar apparent affinities (1 × 109to 2 × 109liters/mol) against either a “cluster II”-overlapping epitope of gp41 or against the CD4 binding site, V3 loop, or C5 domain of gp120 directed substantial and comparable levels of specific lysis against targets infected with laboratory-adapted strains of HIV-1. As expected, those MAbs specific for relatively conserved regions of Env generally exhibited ADCC activity against a broader range of HIV-1 strains than those directed against variable epitopes. Significant ADCC activities of selected MAbs against primary isolate Env-expressing cells were demonstrated. In addition, a new ADCC epitope in the V2 domain of gp120 was defined. CD56+cells were demonstrated to be the effector cells in these studies by fluorescence-activated cell sorting followed by ADCC assays. Notably, all anti-Env MAbs tested in this study, including MAbs directed against each of the known neutralization epitope clusters in gp120, directed significant levels of ADCC against targets expressing Env of one or more HIV-1 strains. These results imply that many, if not most, HIV-1-neutralizing human Abs of high affinity (≥3 × 108liters/mol in these studies) and of the immunoglobulin G1 (IgG1) subclass (i.e., the predominate IgG subclass) are capable of directing ADCC. Since neutralizing Abs have been associated with long-term survival following HIV-1 infection, this suggests that ADCC activity may be beneficial in vivo.
Spontaneous Mutations in the
env
Gene of the Human Immunodeficiency Virus Type 1 NDK Isolate Are Associated with a CD4-Independent Entry Phenotype
Authors: Dumonceaux Julie , Nisole Sébastien , Chanel Chantal , Quivet Laurence , Amara Ali , Baleux Frano̧ise , Briand Pascale , Hazan Uriel 
Published: December 2019

ABSTRACT
Human immunodeficiency virus type 1 (HIV-1) entry into target cells is a multistep process initiated by envelope protein gp120 binding to cell surface CD4. The conformational changes induced by this interaction likely favor a second-step interaction between gp120 and a coreceptor such as CXCR4 or CCR5. Here, we report a spontaneous and stable CD4-independent entry phenotype for the HIV-1 NDK isolate. This mutant strain, which emerged from a population of chronically infected CD4-positive CEM cells, can replicate in CD4-negative human cell lines. The presence of CXCR4 alone renders cells susceptible to infection by the mutant NDK, and infection can be blocked by the CXCR4 natural ligand SDF-1. Furthermore, we have correlated the CD4-independent phenotype with seven mutations in the C2 and C3 regions and the V3 loop. We propose that the mutant gp120 spontaneously acquires a conformation allowing it to interact directly with CXCR4. This virus provides us with a powerful tool to study directly gp120-CXCR4 interactions.
Glycoproteins M and N of Pseudorabies Virus Form a Disulfide-Linked Complex
Authors: Jöns Alice , Dijkstra Johannes M. , Mettenleiter Thomas C. 
Published: December 2019

ABSTRACT

Genes homologous to the herpes simplex virus UL49.5 open reading frame are conserved throughout the
Herpesviridae
. In the alphaherpesvirus pseudorabies virus (PrV), the UL49.5 product is an O-glycosylated structural protein of the viral envelope, glycoprotein N (gN) (A. Jöns, H. Granzow, R. Kuchling, and T. C. Mettenleiter, J. Virol. 70:1237–1241, 1996). For functional characterization of gN, a gN-negative PrV mutant, PrV-gNβ, and the corresponding rescuant, PrV-gNβR, were constructed, gN-negative PrV was able to productively replicate on noncomplementing cells, and one-step growth in cell culture was only slightly reduced compared to that of wild-type PrV. However, penetration was significantly delayed. In indirect immunofluorescence assays with rabbit serum directed against baculovirus-expressed gN, specific staining of wild-type PrV-infected cells occurred only after permeabilization of cells, whereas live cells failed to react with the antiserum. This indicates the lack of surface accessibility of gN in the plasma membrane of a PrV-infected cell. Western blot analyses and radioimmunoprecipitation experiments under reducing and nonreducing conditions led to the discovery of a heteromeric complex composed of gM and gN. The complex was stable in the absence of 2-mercaptoethanol but dissociated after the addition of the reducing agent, indicating that the partners are linked by disulfide bonds. Finally, gN was absent from gM-negative PrV virions, whereas gM was readily detected in virions in the absence of gN. Thus, gM appears to be required for virion localization of gN.
Genetic Determinants of Rous Sarcoma Virus Particle Size
Authors: Krishna Neel K. , Campbell Stephen , Vogt Volker M. , Wills John W. 
Published: December 2019

ABSTRACT
The Gag proteins of retroviruses are the only viral products required for the release of membrane-enclosed particles by budding from the host cell. Particles released when these proteins are expressed alone are identical to authentic virions in their rates of budding, proteolytic processing, and core morphology, as well as density and size. We have previously mapped three very small, modular regions of the Rous sarcoma virus (RSV) Gag protein that are necessary for budding. These assembly domains constitute only 20% of RSV Gag, and alterations within them block or severely impair particle formation. Regions outside of these domains can be deleted without any effect on the density of the particles that are released. However, since density and size are independent parameters for retroviral particles, we employed rate-zonal gradients and electron microscopy in an exhaustive study of mutants lacking the various dispensable segments of Gag to determine which regions would be required to constrain or define the particle dimensions. The only sequence found to be absolutely critical for determining particle size was that of the initial capsid cleavage product, CA-SP, which contains all of the CA sequence plus the spacer peptides located between CA and NC. Some regions of CA-SP appear to be more important than others. In particular, the major homology region does not contribute to defining particle size. Further evidence for interactions among CA-SP domains was obtained from genetic complementation experiments using mutant ΔNC, which lacks the RNA interaction domains in the NC sequence but retains a complete CA-SP sequence. This mutant produces low-density particles heterogeneous in size. It was rescued into particles of normal size and density, but only when the complementing Gag molecules contained the complete CA-SP sequence. We conclude that CA-SP functions during budding in a manner that is independent of the other assembly domains.
The Mouse Homolog of the Bovine Leukemia Virus Receptor Is Closely Related to the δ Subunit of Adaptor-Related Protein Complex AP-3, Not Associated with the Cell Surface
Authors: Suzuki Takako , Ikeda Hidetoshi 
Published: December 2019

ABSTRACT

A mouse cDNA (mBLVR1) which was highly homologous to the bovine cDNA of the bovine leukemia virus receptor (
BLVR
) gene was cloned. The mBLVR1 cDNA, of 4,730 bp, covered nearly the full length of the mRNA (about 5 kb) and included an open reading frame (ORF) encoding a protein of 1,199 amino acids. While the bovine BLVR protein was thought to be a type I transmembrane protein, the deduced protein coded by mBLVR1 did not appear to be a typical transmembrane protein. The ORF of mBLVR1 ended at a site 280 amino acids upstream of the termination codon of the bovine BLVR ORF, so the deduced mouse BLVR protein lacked the corresponding transmembrane and cytoplasmic regions of the predicted bovine BLVR protein. No significant hydrophobic region was found in the mouse protein. Recently, a human cDNA which was highly homologous (69.6% homology) to the mouse
BLVR
gene was reported. The cDNA encodes the δ subunit of the human adaptor-related protein complex AP-3, which aligned almost collinearly with the mouse BLVR protein. AP-3 and all other related adaptor protein complexes have been shown to be associated with intracellular vesicles but not with the cell surface. Thus, the mouse
BLVR
homolog appeared to be the mouse AP-3 δ subunit itself or closely related to it, but the bovine
BLVR
gene seemed slightly different from the adaptor subunit gene family.
The gH-gL Complex of Herpes Simplex Virus (HSV) Stimulates Neutralizing Antibody and Protects Mice against HSV Type 1 Challenge
Authors: Peng Tao , Ponce-de-Leon Manuel , Jiang Hongbin , Dubin Gary , Lubinski John M. , Eisenberg Roselyn J. , Cohen Gary H. 
Published: December 2019

ABSTRACT
The herpes simplex virus type 1 (HSV-1) gH-gL complex which is found in the virion envelope is essential for virus infectivity and is a major antigen for the host immune system. However, little is known about the precise role of gH-gL in virus entry, and attempts to demonstrate the immunologic or vaccine efficacy of gH and gL separately or as the gH-gL complex have not succeeded. We constructed a recombinant mammalian cell line (HL-7) which secretes a soluble gH-gL complex, consisting of gH truncated at amino acid 792 (gHt) and full-length gL. Purified gHt-gL reacted with gH- and gL-specific monoclonal antibodies, including LP11, which indicates that it retains its proper antigenic structure. Soluble forms of gD (gDt) block HSV infection by interacting with specific cellular receptors. Unlike soluble gD, gHt-gL did not block HSV-1 entry into cells, nor did it enhance the blocking capacity of gD. However, polyclonal antibodies to the complex did block entry even when added after virus attachment. In addition, these antibodies exhibited high titers of complement-independent neutralizing activity against HSV-1. These sera also cross-neutralized HSV-2, albeit at low titers, and cross-reacted with gH-2 present in extracts of HSV-2-infected cells. To test the potential for gHt-gL to function as a vaccine, BALB/c mice were immunized with the complex. As controls, other mice were immunized with gD purified from HSV-infected cells or were sham immunized. Sera from the gD- or gHt-gL-immunized mice exhibited high titers of virus neutralizing activity. Using a zosteriform model of infection, we challenged mice with HSV-1. All animals showed some evidence of infection at the site of virus challenge. Mice immunized with either gD or gHt-gL showed reduced primary lesions and exhibited no secondary zosteriform lesions. The sham-immunized control animals exhibited extensive secondary lesions. Furthermore, mice immunized with either gD or gHt-gL survived virus challenge, while many control animals died. These results suggest that gHt-gL is biologically active and may be a candidate for use as a subunit vaccine.
Inhibition of Human Cytomegalovirus DNA Maturation by a Benzimidazole Ribonucleoside Is Mediated through the UL89 Gene Product
Authors: Underwood Mark R. , Harvey Robert J. , Stanat Sylvia C. , Hemphill Mary Lou , Miller Teresa , Drach John C. , Townsend Leroy B. , Biron Karen K. 
Published: December 2019

ABSTRACT

2-Bromo-5,6-dichloro-1-β-
d
-ribofuranosyl benzimidazole (BDCRB) is a member of a new class of benzimidazole ribonucleosides which inhibit human cytomegalovirus (HCMV) late in the replication cycle without inhibiting viral DNA synthesis. We show here that polygenomic concatemeric HCMV DNA does not mature to unit genome length in the presence of BDCRB. To discover the locus of action, virus resistant to BDCRB was selected by serial passage in the presence of the compound. Genetic mapping experiments with BDCRB-resistant virus demonstrated that the resistance phenotype mapped to one amino acid (Asp
344
Glu; low resistance) or two amino acids (Asp
344
Glu and Ala
355
Thr; high resistance) within the product of exon 2 of the HCMV U
L
89 open reading frame. The HCMV U
L
89 open reading frame and its homologs are among the most conserved open reading frames in the herpesviruses, and their products have sequence similarities to a known ATP-dependent endonuclease from the double-stranded DNA bacteriophage T4. These findings strongly suggest that BDCRB prevents viral DNA maturation by interacting with a U
L
89 gene product and that the U
L
89 open reading frame may encode an endonucleolytic subunit of the putative HCMV terminase. Further, since mammalian cell DNA replication does not involve a DNA maturation step, compounds which inhibit viral DNA maturation should be selective and safe.
CXCR-4 Is Expressed by Primary Macrophages and Supports CCR5-Independent Infection by Dual-Tropic but Not T-Tropic Isolates of Human Immunodeficiency Virus Type 1
Authors: Yi Yanjie , Rana Shalini , Turner Julie D. , Gaddis Nathan , Collman Ronald G. 
Published: December 2019

ABSTRACTPrimary macrophages are infected by macrophage (M)-tropic but not T-cell line (T)-tropic human immunodeficiency virus type 1 (HIV-1) strains, and CCR5 and CXCR-4 are the principal cofactors utilized for CD4-mediated entry by M-tropic and T-tropic isolates, respectively. Macrophages from individuals homozygous for an inactivating mutation of CCR5 are resistant to prototype M-tropic strains that depend on CCR5 but are permissive for a dual-tropic isolate, 89.6, that can use both CCR5 and CXCR-4, as well as CCR2b, CCR3, and CCR8. Here we show that 89.6 entry into CCR5-deficient macrophages is blocked by an anti-CXCR-4 antibody and by the CXCR-4-specific chemokine SDF but not by the ligands to CCR2b or CCR3. Reverse transcription-PCR demonstrated expression of CXCR-4 but not CCR3 or CCR8 in macrophages, while CCR2b was variable. Macrophage surface expression of CXCR-4 was confirmed by immunofluorescence staining and flow cytometry. Thus, CXCR-4 is expressed by primary macrophages and functions as a cofactor for entry by dual-tropic but not T-tropic HIV-1 isolates, and macrophage resistance to T-tropic strains does not result from a lack of the T-tropic entry cofactor CXCR-4. Since CXCR-4 on macrophages can be used by some but not other isolates, these results indicate that HIV-1 strains differ in how they utilize chemokine receptors as cofactors for entry and that the ability of a chemokine receptor to mediate HIV-1 entry differs, depending on the cell type in which it is expressed.
Gene Arrangement within the Unique Long Genome Region of Infectious Laryngotracheitis Virus Is Distinct from That of Other Alphaherpesviruses
Authors: Ziemann Katharina , Mettenleiter Thomas C. , Fuchs Walter 
Published: December 2019

ABSTRACT

The genome of the avian alphaherpesvirus infectious laryngotracheitis virus (ILTV) comprises ca. 155 kbp of which ca. one-third have been sequenced so far. To gain additional sequence information we analyzed two stretches of 15.5 and 1.9 kbp of the ILTV unique long (U
L
) genome region. The larger fragment contains homologs of the herpes simplex virus (HSV) UL23 (thymidine kinase) and UL22 (glycoprotein H) genes followed by five open reading frames (ORF) encoding putative proteins of 334 to 410 amino acids which exhibit no homology to any known herpesvirus protein. RNA analyses showed that these unique ILTV genes are indeed expressed. An origin of replication separates this cluster of unique genes from a conserved gene cluster consisting of the UL45, UL46, UL48, UL49, UL49.5, and UL50 homologs. The absence of UL47 from this position coincides with the localization of a UL47-homologous ORF within the unique short (U
S
) region of the ILTV genome (M. Wild, S. Cook, and M. Cochran, Virus Genes 12:107–116, 1996). Within the second analyzed region the ILTV UL21 homolog was found adjacent to the UL44 gene. We thus identified five novel herpesvirus genes in ILTV and present evidence for a large internal inversion in the ILTV U
L
region, in contrast to the collinear genomes of other alphaherpesviruses. Interestingly, a similar inversion is also present in the porcine alphaherpesvirus pseudorabies virus.
Effect of Immune Activation on the Dynamics of Human Immunodeficiency Virus Replication and on the Distribution of Viral Quasispecies
Authors: Ostrowski Mario A. , Krakauer David C. , Li Yuexia , Justement Shawn J. , Learn Gerald , Ehler Linda A. , Stanley Sharilyn K. , Nowak Martin , Fauci Anthony S. 
Published: December 2019

ABSTRACTVirus replication in a human immunodeficiency virus (HIV)-infected individual, as determined by the steady-state level of plasma viremia, reflects a complex balance of viral and host factors. We have previously demonstrated that immunization of HIV-infected individuals with the common recall antigen, tetanus toxoid, disrupts this steady state, resulting in transient bursts of plasma viremia after immunization. The present study defines the viral genetic basis for the transient bursts in viremia after immune activation. Tetanus immunization was associated with dramatic and generally reversible shifts in the composition of plasma viral quasispecies. The viral bursts in most cases reflected a nonspecific increase in viral replication secondary to an expanded pool of susceptible CD4+T cells. An exception to this was in a patient who harbored viruses of differing tropisms (syncytium inducing and non-syncytium inducing [NSI]). In this situation, immunization appeared to select for the replication of NSI viruses. In one of three patients, the data suggested that immune activation resulted in the appearance in plasma of virus induced from latently infected cells. These findings illustrate certain mechanisms whereby antigenic stimulation may influence the dynamics of HIV replication, including the relative expression of different viral variants.
The NH
2
Terminus of the Herpes Simplex Virus Type 1 Regulatory Protein ICP0 Contains a Promoter-Specific Transcription Activation Domain
Authors: Lium Erik K. , Panagiotidis Christos A. , Wen Xiaoshan , Silverstein Saul J. 
Published: December 2019

ABSTRACT

The transcriptional program of herpes simplex virus is regulated by the concerted action of three immediate-early (α) proteins, ICP4, ICP27, and ICP0. The experiments described in this study examine the role of the acidic amino terminus (amino acids 1 to 103) of ICP0 in gene activation. When tethered to a DNA binding domain, this sequence activates transcription in the yeast
Saccharomyces cerevisiae
. Deletion of these amino acids affects the ability of ICP0 to activate α-gene promoter reporters in transient expression assays, while it has little or no effect on a β- and a γ-gene reporter in the same assay. Viruses that express the deleted form of ICP0 (ICP0-NX) have a small-plaque phenotype on both Vero cells and the complementing cell line L7. Transient expression and immunofluorescence analyses demonstrate that ICP0-NX is a dominant negative form of ICP0. Immunoprecipitation of ICP0 from cells coinfected with viruses expressing ICP0-NX and ICP0 revealed that ICP0 oligomerizes in infected cells. These data, in conjunction with the finding that ICP0-N/X is dominant negative, provide both biochemical and genetic evidence that ICP0 functions as a multimer in infected cells.
E1B 55-Kilodalton-Associated Protein: a Cellular Protein with RNA-Binding Activity Implicated in Nucleocytoplasmic Transport of Adenovirus and Cellular mRNAs
Authors: Gabler Stefan , Schütt Holger , Groitl Peter , Wolf Hans , Shenk Thomas , Dobner Thomas 
Published: December 2019

ABSTRACT
The adenovirus type 5 (Ad5) early 1B 55-kDa protein (E1B-55kDa) is a multifunctional phosphoprotein that regulates viral DNA replication and nucleocytoplasmic RNA transport in lytically infected cells. In addition, E1B-55kDa provides functions required for complete oncogenic transformation of rodent cells in cooperation with the E1A proteins. Using the far-Western technique, we have isolated human genes encoding E1B-55kDa-associated proteins (E1B-APs). The E1B-AP5 gene encodes a novel nuclear RNA-binding protein of the heterogeneous nuclear ribonucleoprotein (hnRNP) family that is highly related to hnRNP-U/SAF-A. Immunoprecipitation experiments indicate that two distinct segments in the 55-kDa polypeptide which partly overlap regions responsible for p53 binding are required for complex formation with E1B-AP5 in Ad-infected cells and that this protein interaction is modulated by the adenovirus E4orf6 protein. Expression of E1B-AP5 efficiently interferes with Ad5 E1A/E1B-mediated transformation of primary rat cells. Furthermore, stable expression of E1B-AP5 in Ad-infected cells overcomes the E1B-dependent inhibition of cytoplasmic host mRNA accumulation. These data suggest that E1B-AP5 might play a role in RNA transport and that this function is modulated by E1B-55kDa in Ad-infected cells.