pinecone/core-2020-05-10-deduplication huggingface dataset:
A Comparison of the Spread of Murray Valley Encephalitis Viruses of High or Low Neuroinvasiveness in the Tissues of Swiss Mice after Peripheral Inoculation

AbstractA Murray Valley encephalitis virus (MVE) field isolate of high neuroinvasiveness (BH3479) and a neutralization escape variant of low neuroinvasiveness (BHv1) selected from BH3479 (which differ by a single amino acid at residue 277 in the envelope glycoprotein) were examined for their distribution in the tissues of weanling Swiss mice at various times after footpad inoculation. BH3479 was first detected in lymph nodes draining the inoculated limb at 24 hr postinoculation (pi) and was found in serum between 36 and 72 hr pi. BH3479 was first detected in the central nervous system (CNS) at 4 days pi and reached maximum CNS titers (>109PFU/g) between 6 and 9 days pi. All BH3479-infected mice developed encephalitis and died before 10 days pi. In contrast, BHv1 was not detected in lymph nodes draining the footpad at any time after inoculation; BHv1 was first detected in the serum between 60 and 72 hr pi—24 hr later, and at a 20-fold lower titer than for BH3479. BHv1 was first detected in the CNS at 7 days pi 3 days later and at a 300-fold lower titer than for BH3479. After 10 days pi, BHv1 could not be isolated from the CNS or from other host tissues. Most BHv1-infected mice experienced a subclinical infection; the mortality rate from BHv1 infection was less than 1%. Both viruses appeared to enter the CNS via the olfactory lobes. BH3479 spread throughout the CNS in a rostral to caudal direction over 3–4 days. In contrast, BHv1 infection in the CNS was restricted to the olfactory lobes and adjacent structures of the forebrain
Localization of the UsProtein Kinase of Equine Herpesvirus Type 1 Is Affected by the Cytoplasmic Structures Formed by the Novel IR6 Protein

AbstractPrevious work revealed that the Us(unique short) segment of equine herpesvirus type-1 (EHV-1), like that of other alphaherpesviruses, encodes a serine/threonine protein kinase (PK). Experiments were carried out to identify the PK encoded by the EHV-1 EUS2 gene (ORF 69) and to ascertain its time course of synthesis and cellular localization. Western blot and immunoprecipitation analyses of EHV-1-infected cell extracts using a PK-specific polyclonal antibody generated against a bacterially expressed TrpE/PK fusion protein identified the UsPK as a 42- to 45-kDa phosphoprotein. The PK protein is first synthesized at 3 hr postinfection, is produced throughout the infection cycle, and is incorporated into EHV-1 virions. Interestingly, immunoprecipitation analyses revealed that the PK protein within the cytoplasm is associated with the 33-kDa IR6 novel protein of EHV-1, is expressed abundantly as an early protein, and is present in the large rod-like structures formed by the IR6 protein (ORF67 protein) within the cytoplasm of infected cells. Confocal microscopic examination of cells stained with fluorescein-labeled antibody clearly showed that the PK protein colocalized with the cytoplasmic IR6 rod-like structures and remained associated with these unique structures during infection. In contrast, in cells infected with the EHV-1 RacM strain in which the IR6 protein harbors four amino acid substitutions that prevent formation of the rod-like structures (Osterriederet al.,1996,Virology217, 442–451), the PK protein localized predominantly to the nucleus. The possible significance of the association of the IR6 and PK proteins in EHV-1 replication is discussed
Functional Characterization of the V1V2 Region of Human Immunodeficiency Virus Type I

AbstractThe level of proviral DNA sequence variation in the V1V2 region was monitored over time in six HIV-1-infected individuals. Substitutional and length variation was observed, where the majority of length changes, ranging from 28 to 49 amino acids, was located within the V1 region. Evidence for convergent evolution in the V2 region was found. The functional significance of this variation was assessed by cloning the V1V2 sequences into an infectious molecular clone, HXB2. The majority of chimeras replicated, demonstrating that the sequences, though genetically distinct, were capable of conferring a viable phenotype. Chimeras expressing closely related sequences in a constant genetic background displayed different biological phenotypes, with respect to both cytopathicity and cell tropism. However, no association between primary V1V2 amino acid sequence and viability or cytopathicity of the chimeric virus was observed, suggesting that predictions of virus phenotype based on sequences alone may be incorrect. The effect of V1V2 variation on the overall gp120 conformation was measured by expressing the gp120 from a number of viable and nonviable clones. No differences were observed, suggesting that misfolding of the chimeric gp120 protein was not an explanation for the nonviability of some virus clones. Several chimeras were noncytopathic and only able to replicate in PBMC cultures, demonstrating that the V1V2 region, independent of the V3 sequence, is capable of defining both tropism and cytopathicity
Chimeric Viruses Expressing Primary Envelope Glycoproteins of Human Immunodeficiency Virus Type I Show Increased Sensitivity to Neutralization by Human Sera

AbstractWe constructed a number of HXB2 viruses chimeric for the gp120 glycoprotein derived from a number of viable molecular clones obtained from a primary isolate. Comparative biological characterization of the parental primary viruses with the gp120.HXB2 chimeras demonstrated identical patterns of cell tropism and cytopathicity. Furthermore, both parental and chimeric viruses were insensitive to neutralization by sCD4 and a panel of conformation-dependent monoclonal antibodies, demonstrating that transfer of the gp120 protein alone was sufficient to confer a “neutralization-resistant” phenotype to the T-cell-adapted clone HXB2. We assessed the contribution of gp120 epitopes to the neutralizing immune response by comparing the sensitivity of these viruses to neutralization by a panel of sera from HIV-infected individuals. Seven of eleven sera tested were able to neutralize HXB2 and two or more of the chimeric viruses; in contrast, only one serum neutralized more than one of the parental primary virus clones. The association of gp120–gp41 envelope at the surface of infected PBMC cultures was measured in the presence or absence of soluble CD4. No differences in CD4-induced gp120 dissociation were seen between the chimeric and parental virus-infected cultures. Since gp120 conformation appeared the same between primary and chimeric viruses, we suggest that the ability of human sera to neutralize the chimeric viruses may be mediated by epitopes within gp41
Mutational Analysis of HIV-1 gp160-Mediated Receptor Interference: Intracellular Complex Formation

AbstractFormation of CD4–gp160 intracellular complexes represents an important mechanism leading to the induction of receptor interference. Previous studies have demonstrated that cells coexpressing gp160 and CD4 formed complexes of CD4 and gp160 which became blocked within the endoplasmic reticulum (ER), preventing CD4 from reaching the cell surface. In this report we have investigated the domains and residues of CD4 and gp160 involved in intracellular interaction. Accordingly, we have introduced mutations in both CD4 and gp160 at sites previously shown to disrupt CD4–gp120 interactions at the cell surface. Using a T7-vaccinia virus transient expression system, we expressed these gp160 and CD4 mutants in HeLa cells and analyzed their effects on intracellular complex formation and CD4 surface modulation. We observed that a number of gp160 mutants which failed to interact with CD4 at the cell surface also failed to bind and trap CD4 within the ER as expected. However, mutations at a critical residue, W427, did not abrogate intracellular CD4 binding. These gp160 mutants continued to interact with intracellular CD4 and inhibit CD4 transport to the cell surface, although gp120 produced from these mutants did not bind CD4 at the cell surface as expected. A number CD4 mutants also continued to form intracellular complexes with gp160, resulting in the loss of CD4 surface expression. Again, these CD4 mutants did not bind to gp120 at the cell surface, consistent with earlier reports. These results demonstrate that intracellular interactions between gp160 and CD4 in the ER may utilize different contact sites compared to those used during CD4 and gp120 binding at the cell surface. The data provide further evidence that the environment in which CD4 and the HIV-1 envelope glycoprotein interact can have a significant effect on their interaction
Membrane Anchorage of gp160 Is Necessary and Sufficient to Prevent CD4 Transport to the Cell Surface

AbstractThe HIV envelope glycoprotein gp160 plays a major role in the posttranslational down-regulation of its receptor, CD4. In this report we have analyzed the requirements of both CD4 and gp160 involved in transport block of the gp160–CD4 complex causing the down-regulation of cell surface CD4. Using a transient expression system we observed that both soluble and membrane-bound CD4 were equally blocked by the wild-type gp160, indicating that neither the transmembrane domain nor the cytoplasmic tail of CD4 affected its interaction with gp160 or exocytic transport block of the complex. Similarly, deletions of the gp160 cytoplasmic domain or mutation in the transmembrane domain had little effect on its transport, or its ability to down-regulate CD4 surface expression. Furthermore, substitution of the gp160 transmembrane domain and cytoplasmic tail with that of the influenza virus hemagglutinin or with a glycophosphatidylinositol moiety did not affect its ability to bind CD4 and block its transport. However, soluble envelope glycoprotein constructs (either gp120 or soluble gp160) were unable to block CD4 transport to the cell surface despite their binding to CD4 within the ER. Taken together these results demonstrate that neither the gp160 cytoplasmic tail nor the specific sequences of the transmembrane region of gp160 nor the membrane anchoring of CD4 were involved in ER retention of the CD4–gp160 complex and that anchoring of gp160 to the ER membrane was responsible for gp160-mediated cell surface down-regulation of CD4
Generation of Defective Interfering Particles by Two Vaccine Strains of Measles Virus

AbstractA systematic study was made to measure the generation of defective interfering particles upon up to 13 serial passages of two measles vaccine strains, Edmonston and Edmonston–Zagreb, through either simian (Vero) or human (WI-38) cell lines. Results for the Vero cell passage were nearly identical for both viruses. Infectivity titers dropped by nearly 8 logs to undetectable levels at passage 4 and cycled between maximum and minimum levels every 4 passages. Samples with the lowest infectivity titers produced the greatest reduction in titer of standard virus and contained an approximately 900-nucleotide subgenomic RNA for the Edmonston strain and two subgenomic RNAs of 4300 and 3000 nucleotides for the Edmonston–Zagreb vaccine strain. A defective interfering RNA-specific reverse transcription-polymerase chain reaction (RT-PCR) detected subgenomic RNAs at all passage levels. In contrast, samples obtained after passage of these viruses in WI-38 did not reduce the yield of standard virus and did not contain subgenomic RNAs in both Northern blot and RT-PCR assays. These results clearly show that cell type rather than virus strain affects defective interfering particle generation for measles virus
Analysis of the Intracellular Transport Properties of Recombinant La Crosse Virus Glycoproteins

AbstractThe G1 and G2 glycoproteins of La Crosse virus, a member of theBunyavirusgenus of the Bunyaviridae, are encoded as a single open reading frame (ORF) in the viral middle-sized RNA segment. The primary product from this ORF is processed, either cotranslationally or shortly after translation, into the two glycoproteins and a nonstructural protein, NSm, of unknown function. We have expressed La Crosse glycoproteins using vaccinia vectors and studied their processing and localization. When expressed in the native G2-NSm-G1 configuration, both G1 and G2 targeted to the Golgi apparatus as shown by their colocalization with wheat germ agglutinin and acquired resistance to endoglycosidase H. When expressed independently, G2 was targeted to the Golgi apparatus but G1 was retained in the endoplasmic reticulum, indicating that a G1–G2 association is required for Golgi targeting of G1. In contrast to results with other members of the Bunyaviridae, we found that expression of G1 and G2 from separate vectors did not lead to the transport of the G1–G2 complex to the Golgi. However, disruption of the NSm region with a foreign sequence did not interfere with transport of the complex. When a portion of the β-galactosidase gene was inserted in frame into NSm, the glycoproteins derived from this construct were processed and targeted properly and were capable of mediating cell-to-cell fusion
Neutralizing Epitope on Penetration Protein of Vaccinia Virus

AbstractThe monoclonal antibody 2D5 neutralized vaccinia virus by preventing penetration of the virus and reacting with VP23-29K. The conformation of the VP23-29K was maintained by a disulfide bond(s), and the 2D5mAb reacted stronger with the nonreduced 23-kDa form than with the reduced 29-kDa form. We selected several escape mutants. Sequences of the A17L genes, which were thought to encode the VP23-29K, did not show cognate mutation. Genomic DNA of a 2D5mAb-resistant mutant (M4) was cleaved withHindIII, and all the fragments were introduced into parental IHD-J strain vaccinia virus by transfection. Only the L fragment produced a 2D5mAb-resistant virus. Dissection of the L fragment and subsequent transfection revealed that the L1R gene induced the 2D5mAb-resistant virus. The 2D5mAb-resistant mutants showed a consensus G to A conversion at nucleotide 101 of their LIRs which would replace asparatic acid 35 with asparagine. Ishibashi-111 strain mousepox virus spontaneously resistant to 2D5mAb also had the same sequence at this region. Moreover, the VP23-29K was myristoylated as predicted by the L1R gene. The coding gene of the VP23-29K was L1R
The Herpes Simplex Virus Type 1 Transactivator ICP0 Mediates Aberrant Intracellular Localization of the Viral Helicase/Primase Complex Subunits

AbstractThe infected cell polypeptide 0 (ICP0) protein of herpes simplex virus type 1 (HSV-1) is a promiscuous transactivator. When expressed by transfection, ICP0 forms spherical structures in the nucleus. Using a double-label immunofluorescence assay, we have found that the HSV-1 helicase/primase complex subunits accumulate within ICP0 structures in cotransfected cells. This phenomenon was also observed in cells coexpressing ICP0 and UL6, a protein thought to be involved in the cleavage and/or packaging of viral genomes. ICP0 structures were found to be proteinaceous by immunoelectron microscopy. These results suggest that ICP0 may interact nonspecifically with a variety of viral proteins
Nucleo-Cytoplasmic Redistribution of the HTLV-I Rex Protein: Alterations by Coexpression of the HTLV-I p21xProtein

AbstractThe function of the Rex protein of human T-cell leukemia virus type I (HTLV-I) has been demonstrated to be very similar to the Rev protein of human immunodeficiency virus type 1 (HIV-1). Both of these retroviral regulatory proteins rescue unspliced viral RNAs from the nuclei of infected cells. The Rev protein of HIV-1 has been reported to shuttle between the nucleus/nucleolus and the cytoplasm. Here, we have found that Rex also relocated out of the nucleus in the presence of actinomycin D. This effect was demonstrated in dose- and time-course-dependent manners. In comparison with previous reports on HIV-1 Rev, these effects with Rex seemed to be similar, but less distinct, which may reflect precise differences in the subcellular localization and/or shuttling pathways of Rev and Rex. Interestingly, the endogenous truncated form of the Rex protein, p21x, significantly interfered with the intracellular translocation of Rex, when coexpressedin trans.As expression of p21xoccurs in various HTLV-I-infected cells, p21xmay play a role in the life-cycle of HTLV-I, through regulating the dynamic subcellular distribution of the viral trans-activator, Rex
Viral Persistence in Neurons Alters Synaptic Plasticity and Cognitive Functions without Destruction of Brain Cells

AbstractNeurons have a restricted expression of MHC heavy chain molecules which prevents presentation of antigens of infecting viruses. As a result, such infected cells escape immune surveillance and allow the establishment of noncytolytic persistent infection. Here we show that a chronic noncytolytic viral infection bothin vitroandin vivoselectively perturbed the expression of GAP-43, a protein that plays a central role in neuronal plasticity processes accompanying learning and memory. GAP-43 expression was greatly decreased in the hippocampus, an area of heightened viral replication, while synaptic density was preserved. Concurrently, the ability to learn tasks was significantly impaired in these persistently infected mice. Yet, infected neurons remained free from structural injury
Molecular Interactions between the HSV-1 Capsid Proteins as Measured by the Yeast Two-Hybrid System

AbstractHSV-1 B capsids are composed of seven major proteins, designated VP5, VP19C, 21, 22a, VP23, VP24, and VP26. VP indicates that the capsid protein is also a component of the infectious virion. Capsid proteins 21, 22a, and VP24 are specified by a single open reading frame (UL26) that encodes 635 amino acids. An objective of the work in our laboratory is to identify and map interactions among and between capsid proteins. In the present studies we employed the yeast GAL4 two-hybrid system developed by Fields and his colleagues (Nature240, 245–246 (1989)) for this purpose. DNA corresponding to the capsid open reading frames was derived as a PCR product and fused to sequences of the GAL4 activation and DNA binding domains. Using this system each of the capsid proteins has been tested for interactions with all of the other capsid proteins. Three interactions have been identified: a relatively strong self-interaction between 22a molecules (residues 307–635 of UL26), bimolecular interactions between 22a and VP5, and another between VP19C and VP23. The interactions were detected by the expression of β-galactosidase enzyme activity, and yielded 289, 86, and 63 units of enzyme activity, respectively. For the 22a self-interaction, elimination of residues 611–635 resulted in an approximately twofold decrease in enzyme activity. The C-terminal 25 amino acids of 22a were also essential for the bimolecular interaction between 22a and VP5
Prolonged Infection in Rhesus Macaques with Simian Immunodeficiency Virus (SIVmac239) Results in Animal-Specific and Rarely Tissue-Specific Selection ofnefVariants

AbstractWe analyzed the sequence ofnefgenes from different tissues of three rhesus macaques that had been infected with molecularly cloned SIVmac239 for 88 to 92 weeks. Comparison of the predicted amino acid sequences revealed that each macaque had selected out specific amino acid substitutions and that most of this variation (70%) was confined to four regions, amino acids 39 to 75, 90 to 105, 153 to 167, and 191 to 217, comprising 36% of the protein. Thenefgenes in these animals underwent extensive genetic variation with average nucleotide and amino acid substitution rates varying from 0.86 to 2.84% and 2.47 to 6.27%, respectively, although tissue-specific selection ofnefvariants occurred in only 1 of 14 tissues examined in this study. Comparison of the rate of nucleotide and amino acid substitutions in thenefgenes to those previously reported in theenvin the central nervous system (CNS) and lymph node (LN) revealed that the predicted amino acid substitution rates for Nef were much higher than for the gp120 region ofenvin the CNS and LN tissues for one macaque. In the two other macaques, the predicted amino acid substitution rates were similar between these two proteins in LN tissues, but the amino acid substitution rates in Nef were significantly higher than in the gp120 from the CNS. Comparison of the nucleotide substitutions in the region of overlap between theenvand thenefrevealed that approximately 83% of the nucleotide substitutions in this area resulted in a Nef amino acid sequence change, 26% of the nucleotide substitutions resulted in a gp41 amino acid change, and 9.5% of nucleotide substitutions resulted in amino acid sequence changes in both proteins, suggesting a preference for the selection of amino acid substitutions in the Nef in these animals. Our results indicate that in animals infected with SIVmac239 for prolonged periods, variation in thenefoccurs at rates similar to or exceeding that observed for theenvgene
HIV-1 Gag Protein Associates with F-actin Present in Microfilaments

AbstractSeveral studies have provided evidence that the cellular cytoskeleton may be involved in the assembly and budding of retroviruses. In fractionation studies of HIV-1-infected CEM cells, the majority of the unprocessed Gag polyprotein cofractionated with the cellular cytoskeleton.In vivoandin vitroanalyses of this interaction indicated that the unprocessed Gag polyprotein is capable of association with polymerized actin (F-actin). Binding of Gag to F-actin may be involved in the assembly or budding of HIV-1
Replacement of the Tyrosine Residue That Links a Potyviral VPg to the Viral RNA Is Lethal

AbstractMutants of tobacco vein mottling virus (TVMV) were constructed in which the tyrosine residue (Tyr1860) that links the VPg to the viral RNA was changed to phenylalanine or serine or was inverted in position with the adjacent glycine residue. In another mutant, the tyrosine residue nearest to Tyr1860 (Tyr1867) was changed to a phenylalanine residue. The resulting mutants were tested for their ability to infectNicotiana tabacumplants or protoplasts. The Tyr1860 mutants did not accumulate to detectable levels in infected plants when tested by ELISA and Northern blot analysis. Moreover, the Tyr1860-associated mutants were not infectious in protoplasts, indicating that mutations involving the linking amino acid of the TVMV VPg abolished viral replication. In contrast to the Tyr1860 mutants, transcripts from the mutation of Tyr1867 to a phenylalanine residue infected both protoplasts and plants. Analysis of progeny RNA from plants inoculated with the Tyr1867 mutant indicated that a reversion to wild type had occurred in systemically infected leaves
Variability of Herpes Simplex Virus 1 gL and Anti-gL Antibodies That Inhibit Cell Fusion but Not Viral Infectivity

AbstractHerpes simplex virus type 1 gL lacks a transmembrane domain but stably associates with membranes through its oligomerization with the integral membrane glycoprotein designated gH. The gH-gL oligomers are essential for virion infectivity and virus-induced cell fusion. Monoclonal and polyclonal antibodies were raised against HSV-1(KOS) gL as probes for antigenic structure and functional protein domains. Antigenic determinants recognized by these antibodies were found to be present on gL expressed by many, but not all, strains of HSV-1 and were not detected on gL expressed by HSV-2 strains. These antigenic determinants were localized to the C-terminal region of HSV-1 gL, where amino acid substitutions define at least two classes of HSV-1 gL and where the sequences of HSV-1 and HSV-2 gL diverge considerably. The antibodies were extremely effective at inhibiting virus-induced cell fusion, provided the virus strain expressed the relevant antigenic determinants, but failed to neutralize viral infectivity despite demonstrable binding to virions. These results define strain-dependent differences in the structure and antigenic conformation of HSV-1 forms of gL and suggest that the roles of gL in cell fusion and viral entry are different