pinecone/core-2020-05-10-deduplication huggingface dataset:
Exogenous Mouse Mammary Tumor Virus (MMTV) Infection Induces Endogenous MMTVsagExpression

AbstractThe mouse mammary tumor virus (MMTV) superantigen (Sag) protein is involved in the transmission of milk-borne MMTV from virus-infected milk in the gut to the target mammary gland tissue. Using an RT–PCR assay forin vivoMMTV infection, BALB/c or C3H mice nursed on C3H MMTV-infected mothers showedsagmRNA expression in intestine, spleen, and thymus as early as 1 day after infection, whereas uninfected BALB/c control animals had approximately 10- to 30-fold lowersagexpression. Further fractionation experiments with small intestine indicated thatsagexpression occurred in gut-associated lymphoid cells. Restriction enzyme digestion of PCR products indicated that thesagmRNA detected was derived from the endogenous MMTVs, and sequencing analysis confirmed that the PCR products were derived from endogenousMtv-6.Expression of C3H-specific mRNA was detectable in BALB/cfC3H or C3H tissues by RNase protection or by RT–PCR. Endogenous MMTVsagexpression was low in spleen and undetectable in thymocytes of C3H MMTV-infected C57BL/6 mice, a strain resistant to C3H MMTV tumorigenesis and defective for MHC class II I-E molecules. The RT–PCR assay forsagmRNA appears to measure the Sag-induced stimulation previously predicted for milk-borne MMTV infection. Together these data suggest that exogenous MMTVsagexpression is minimal, but sufficient to rapidly stimulate transcription of endogenous MMTVsagmRNA in B- and T-cells in an MHC class II I-E-dependent manner. The endogenoussagexpression on maternal lymphocytes may increase the number of proliferating T-cells available for milk-borne MMTV infection
N-Linked Glycans in the CD4-Binding Domain of Human Immunodeficiency Virus Type 1 Envelope Glycoprotein gp160 Are Essential for thein VivoPriming of T Cells Recognizing an Epitope Located in Their Vicinity

AbstractDeglycosylation of viral glycoproteins has been suggested to influence the number of available T cell determinants and to increase T cell recognition of antigens. In this study, we have investigated whether T cell responses to the HIV-1 envelope glycoprotein gp160 were influenced by deletion of three N-glycans of the protein. Wild type (wt) and a mutated form of gp160 (gp160A123) lacking the threeN-glycans in the C-terminal CD4-binding region efficiently induced antigen-specific T cell responses in mice of the H-2b, H-2d, and H-2khaplotypes. Further, T cells primed by either wt gp160 or gp160A123were stimulatedin vitroto a similar extent by the homologous and heterologous protein, indicating that deletion of the glycans did not affect the overall immunogenicity and antigenicity of gp160A123. Wild-type gp160 and gp160A123induced comparable T cell responses to those of epitopes which with respect to the secondary structure of gp160 were distant from the deleted glycans. However, in mice of the H-2bhaplotype, wt gp160 primed T cells which respondedin vitroto a peptide containing one of the deleted N-glycosylation sites (Asn448), whereas T cells induced by gp160A123were unable to recognize this peptide. Thus, deletion of the glycans abrogated thein vivopriming of T cells recognizing an epitope in close proximity to the deletion sites. Furthermore, enzymatically deglycosylated gp160 failed to induce a T cell response to this epitope. These results indicate that thein vivogeneration of certain T cell determinants from glycoproteins is dependent on the glycosylation of the protein
The Capsid Architecture of Channel Catfish Virus, an Evolutionarily Distant Herpesvirus, Is Largely Conserved in the Absence of Discernible Sequence Homology with Herpes Simplex Virus

AbstractAlthough herpesviruses have a wide host range and their genomes vary substantially in size, the nucleocapsid appears to be a conservative element of viral design. The capsid shell is icosahedrally symmetric (T= 16), and 125 nm in diameter and 15nm thick in the case of herpes simplex virus 1 (HSV-1). Channel catfish virus (CCV) has the gross morphology of a herpesvirus, although no relationship to other herpesviruses is evident from the sequences of its proteins. To examine CCV capsid architecture more closely, we have determined its structure by cryoelectron microscopy and three-dimensional image reconstruction. The CCV capsid is smaller than that of HSV-1, but its 12% smaller genome is packed to essentially the same average density; its icosahedral facets are flatter, and its shell is about 20% thinner, consistent with the smaller size of its major capsid protein. Otherwise, their major features are remarkably similar: CCV has the same triangulation number; its hexons and pentons also have chimney-like protrusions with an axial channel through each capsomer; and there are “triplexes” on the outer surface at the sites of local threefold symmetry. The basic herpesvirus capsid architecture is, therefore, remarkably well conserved in CCV and implies a utilitarian basis to this design. The protein composition of CCV mirrors that of HSV-1, except for the absence of the 12-kDa protein, VP26, which is dispensable for assembly in the HSV-1 system and, apparently, wholly dispensable for CCV
Effects of Subtle Changes in the SU Protein of Ecotropic Murine Leukemia Virus on Its Brain Capillary Endothelial Cell Tropism and Interference Properties

AbstractPVC-211 murine leukemia virus (MuLV) is a neuropathogenic variant of Friend MuLV (F-MuLV) that causes a rapidly progressive neurodegenerative disease in susceptible rodents. PVC-211 MuLV, but not the parental F-MuLV, can infect rat brain capillary endothelial cells (BCEC) efficiently, and the major determinant for BCEC tropism of PVC-211 MuLV is localized within theXbaI–BamHI fragment of the viral genome containing the 5′ half of theenvgene. To further dissect theXbaI–BamHI region for its effects on BCEC tropism, we constructed recombinant viruses between PVC-211 MuLV and F-MuLV and tested their infectivity on a cell line established from rat BCEC. Our results indicated that Glu116-to-Gly and Glu129-to-Lys substitutions in the background of the F-MuLV envelope SU protein were sufficient for conferring BCEC tropism on the virus. Interference studies of these viruses on Rat-1 fibroblastic cells showed that the structure of the SU protein encoded by theXbaI–BamHI region also has significant effects on their affinity for the rat ecotropic MuLV receptor. These results support the possibility that structural elements I and II of the SU protein are important determinants for virus–receptor interaction
The Product of a 1.9-kb mRNA Which Overlaps the HSV-1 Alkaline Nuclease Gene (UL12) Cannot Relieve the Growth Defects of a Null Mutant

AbstractAlkaline nuclease, a relatively abundant viral phosphoprotein in herpes simplex virus type 1 (HSV-1)- or HSV-2-infected cells, is encoded by a 2.3-kb mRNA (R. H. Costa, K. G. Draper, L. Banks, K. L. Powell, G. Cohen, R. Eisenberg, and E. K. Wagner, 1983.J. Virol.48, 591–603). This mRNA is a member of a family of five unspliced 3′-coterminal messages. Costaet al.proposed that another member of this family of mRNAs (1.9-kb) may encode an N-terminally truncated protein which shares its carboxy-terminus with the alkaline nuclease protein. We previously described the isolation of AN-1, a deletion/insertion mutant of the alkaline nuclease gene (S. K. Weller, R. M. Seghatoleslami, L. Shao, D. Rowse, and E. P. Carmichael, 1990.J. Gen. Virol.71, 2941–2952). The deletion in AN-1 would be predicted to abolish gene products of both the 2.3- and the 1.9-kb mRNAs. To investigate whether the putative truncated version of alkaline nuclease encoded by the 1.9-kb mRNA has enzymatic activity and plays a role in the viral life cycle, a viral mutant (AN-F1) was constructed which is predicted to abolish the gene product of the 2.3-kb mRNA (full-length alkaline nuclease) but leave intact the putative product of the 1.9-kb mRNA. Using a highly sensitive polyclonal antiserum raised against a bacterially expressed full-length alkaline nuclease, we observed a 60-kDa protein in KOS- and AN-F1-infected cells but not in AN-1-infected cells. This suggests that the 60-kDa protein is likely to be expressed from the 1.9-kb mRNA; the open reading frame is now designated UL12.5. Despite the presence of the 60-kDa band, AN-F1 failed to exhibit any alkaline exonuclease activity. This result suggests that the truncated polypeptide (UL12.5) is not enzymatically active, has low levels of activity, or possesses enzymatic activity which is not detected because of the low abundance of the polypeptide. AN-1 and AN-F1 are both severely restricted with respect to growth in Vero cells, as viral yields are 100- to 1000-fold lower than those of wild-type virus. We previously reported that the major defect in AN-1 is in the ability of DNA-containing capsids which form in the nucleus to mature into the cytoplasm (L. Shao, L. M. Rapp, and S. K. Weller, 1993.Virology196, 146–162); AN-F1 exhibits the same defect. These results indicate that although the 1.9-kb mRNA encodes a 60-kDa protein presumably from the UL12.5 open reading frame, this polypeptide cannot substitute for the full-length UL12 product
Subgroup B Adenovirus Type 35 Early Region 3 mRNAs Differ from Those of the Subgroup C Adenoviruses

AbstractAdenovirus type 35 (Ad35) is a member of Ad subgroup B, DNA homology cluster B2. The B2 Ads are unique in that they are isolated most frequently from immunosupressed individuals such as AIDS patients and bone marrow transplant recipients and in that they have a tropism for the urinary tract. One region of the Ad genome which may influence serotype specific pathology is early region 3 (E3). E3 of subgroup C Ad2 and Ad5 has been shown to encode proteins which counteract the immune response to Ad infection. While a great deal is known about gene expression of the subgroup C Ad E3s, little is known about the E3 gene expression from the subgroup B Ads. Although some E3 open reading frames (ORFs) are shared between subgroups B and C, there are additional ORFs that appear in subgroup B. This paper demonstrates the results of an analysis of gene expression from the Ad35 E3 and describes differences in splicing and polyadenylation between the Ad35 and Ad2 E3s. RT–PCR, cDNA sequencing, RNase protection, 3′ RACE, and Northern blotting techniques were utilized to identify, quantify, and determine the structure of six Ad35 E3 mRNAs predicted to encode at least seven proteins. A common intron that is removed during splicing of the subgroup C E3 mRNAs is not removed from Ad35 E3 mRNAs, and only one E3 polyadenylation signal is present in the Ad35 E3 while two polyadenylation signals are used in the formation of subgroup C E3 mRNAs. The quantity of individual mRNAs encoding homologous proteins for Ad35 and Ad2 also differ substantially, presumably because of the absence in Ad35 ofcis-acting signals which have been shown to be important for regulation of Ad2 E3 pre-mRNA processing. Such information should contribute to an understanding of the role the E3 plays in determining subgroup B Ad pathogenesis in general and Ad35 pathogenesis in particular
Human JC Virus cAMP Response Elements Functional for Enhanced Glial Cell Expression in Differentiating Embryonal Carcinoma Cells

AbstractHuman JC virus (JCV) is glial cell-specific for growth and expression. This specificity is attributed to thecis-acting sequences of the two 98-bp tandem repeats in the JCV regulatory region. JCV causes brain lesions, especially in AIDS patients. To study the expression of JCV in glial cells, the role of both repeat region TGAGCTCA sequences, which are homologous to the classical TGAGCTCA cAMP response element (CRE), was examined. The effect of the CRE on expression of the JCV early promoter (JCVE) in response to cAMP was studied with undifferentiated, glial and muscle P19 embryonal carcinoma cells. The results showed a threefold increase in response to cAMP only in the glial cells in which JCV is efficiently expressed. The directin vivorole of the JCV CRE was confirmed by site-directed mutagenesis. Additionally, a CRE oligonucleotide was induced by cAMPin vivo,and inin vitrotranscription assays with glial cell extracts. The early promoter of human BK virus containing nonhomologous CRE sequences was previously shown not to be glial cell-specific and failed to respond to cAMP in glial P19 cells in this study. Mobility shift assays showed the cAMP-inducedin vitrointeraction of glial cell protein(s) with the CRE oligonucleotide. Southwestern blot and uv crosslinking experiments identified an approximately 43-kDa protein interacting with the JCV CRE oligonucleotide. The results indicate that thein vivoexpression of JCVEis specifically increased in response to cAMP only in glial cells and JCV CREin vitroprotein complexes are only detected in response to cAMP for glial cell extracts
Evolution of Canine Parvovirus Involved Loss and Gain of Feline Host Range

AbstractCanine parvovirus (CPV) type-2 emerged as a new virus infecting dogs in 1978, and it was probably derived as a variant of feline panleukopenia virus or of a closely related virus infecting another carnivore. CPV type-2 was subsequently replaced in nature by antigenically variant viruses (CPV type-2a and CPV type-2b) which now coexist in dog populations worldwide. We show that CPV type-2 isolates did not replicate in cats, but that both CPV type-2a and CPV type-2b isolates replicated efficiently. About 10% of the viruses isolated from cats with natural parvovirus disease were antigenically indistinguishable from CPV type-2a or type-2b. The capsid protein gene sequence of a 1990 feline parvovirus isolate (“FPV-24”) was essentially identical to the sequence of CPV type-2b viruses from dogs. The loss and reacquisition of the feline host range in CPV was most likely due in each case to small numbers of changes in a region of the virus capsid where three protein monomers interact
Sequence Analysis of the E3 Region and Fiber Gene of Human Adenovirus Genome Type 7h

AbstractAdenovirus type 7h is currently the predominant virulent genome type of serotype 7 isolated in Argentina, Chile, and Uruguay in association with severe infantile pneumonia. In order to characterize possible molecular determinants of pathogenicity, the nucleotide sequence of a 5904-bp fragment (76 to 93 mu) containing the entire E3 region and the fiber gene of Ad7h was established. The organization of the ORFs within the E3 region was similar to that reported for the prototype strains of Ad7 and Ad3. A comparison of the nucleotide and amino acid sequences of all ORFs revealed a higher homology between Ad7h and Ad7p than between Ad7h and Ad3 for 12.0K and 16.1K, whereas the 15.3K ORF and the adjacent fiber gene were strikingly more homologous to those of Ad3 (99.5 vs 81.1% and 98.2 vs 66.6%, respectively). The equivalent to ORF 7.7K in Ad7p was missing in Ad7h due to a deletion and a mutation affecting the start codon (ATG → ATT). Although the hemagglutinin of the Ad7h fiber could not be characterized due to its lack of activity on monkey erythrocytes, our results indicate that Ad7h is an intermediate strain 7-3
Coexpression of a Nonsyncytium Inducer HIV-1 Glycoprotein Inhibits Syncytium Formation by Another HIV-1 Env Protein

AbstractThe biosynthesis and biological properties of the envelope glycoprotein from a primary isolate of the human immunodeficiency virus type 1, HIV-1 YU2, and the Env product from the laboratory-adapted strain, HIV-1 LAI were compared in the absence of viral replication. We found that the level of expression and proteolytic processing into gp120/gp41 complexes of both glycoproteins was equivalent and independent of the cell type used. Although the two glycoproteins were detected on the surface of HeLa cells expressing high levels of CD4, only the HIV LAI Env product induced significant syncytium formation. Interestingly, when both glycoproteins were coexpressed in HeLa-CD4 cells, syncytium formation was greatly reduced. However, cell fusion could be restored by increasing amounts of the LAI envelope gene product. HeLa-CD4 cells expressing either glycoprotein fused with high efficiency to CEM-A cells, a hybrid of CEM and peripheral blood mononuclear cells, indicating that both glycoproteins were expressed in a biologically active form on the surface of these cells. These studies suggest that primary isolates and laboratory adapted strains may require, in addition to the CD4 receptor, independent accessory membrane components for the fusion activation step. Our results agree with the concept that virus entry requires the concerted activation of each glycoprotein subunit of the Env oligomeric complex
Long-Term Cultivation and Productive Infection of Primary Thymocyte Cultures by a Thymocytopathic Murine Retrovirus

Abstractts1, a mutant of MoMuLV, selectively kills T cells and neurons in the infected host resulting in neuroimmunodegeneration. In the infected thymus there is an early increase in mitosis of thymocytes followed by rapid death, suggesting that thymocyte death may be induced by viral mitogenic activation. Studies on thymocytes obtained fromts1-infected mice indicated that thets1-induced depletion of thymocytes is mediated through activation-induced death by apoptosis. To further investigate the interaction betweents1 and thymocytes, we have established long-term primary murine thymocyte cultures by placing the thymocytes together with thymic remnants in culture medium containing IL-2 and IL-7. These thymocytes retained their immature phenotype and were susceptible to infection byts1 and its parental wild-type MoMuLV.ts1-infected thymocytes proliferated initially at accelerated rate but subsequently produced more infectious virus and died much faster than control or MoMuLV-infected thymocytes. Thesein vitrostudies to some extent reflect ourin vivostudies reported previously
Evidence for Phenotypic Mixing with Reovirus in Cell Culture

AbstractFrom pairwise mixed infections of different reovirus wild-type isolates (T3 Dearing plus T1 Lang or plus T2 Jones) the progeny virus is phenotypically mixed, i.e., progeny viral particles contain proteins derived from both parents but the corresponding genes derived from only one parent. Experiments with differential inactivation of virus progeny of mixed infections by monoclonal antibodies or by 33% ethanol reveal phenotypic mixing of two outer shell proteins, σ1 and probably μ1. Phenotypic mixing of the μ1 protein, the product of the M2 gene, is a possible explanation for the recent observation of M2 gene-linked dominant interference between reovirus isolates (M. N. Rozinov and B. N. Fields. 1994.J. Virol.68, 6667–6671)
Orbivirus Structure and Assembly

AbstractOrbiviruses (Reoviridae family) are complex nonenveloped RNA viruses with seven structural proteins and a RNA genome consisting of 10 variously sized double-stranded RNA segments. Significant advances in orbivirus research have been made in recent years through the use of gene manipulation techniques coupled with the baculovirus expression system. Several orbivirus proteins have yielded to crystallization and X-ray crystallographic structure determination and, when combined with the three-dimensional image reconstruction of virion particles and cores obtained by cryoelectron microscopy, considerable insight has been gained into the intricate organization and topography of the individual viral components. Formal identification of the sites of interaction has been obtained through protein–protein interaction studies on the components of the virion particle, including those that are involved in capsid assembly. Finally, a beginning of the understanding of the sequence of assembly events has also been obtained
Purification of a Virus-Induced RNA Polymerase fromAutographa californicaNuclear Polyhedrosis Virus-Infected Spodoptera Frugiperda Cells That Accurately Initiates Late and Very Late Transcriptionin Vitro

AbstractThe virus-induced RNA polymerase fromAutographa californicanuclear polyhedrosis virus-infectedSpodoptera frugiperdacells was separated from the three host nuclear RNA polymerases by DEAE–Sephadex chromatography and then purified through two more steps: heparin–agarose chromatography and glycerol gradient ultracentrifugation. Fractions from each of these purification steps have been assayedin vitrofor the ability to perform accurate initiation of transcription on a late (p6.9) and a very late (polyhedrin) template using primer extension analysis. In each case, the ability to accurately initiate transcription of these genes coincided with the virus-induced polymerase activity. Only after the glycerol gradient ultracentrifugation step did significant amounts of nonspecific late initiation occur, but specific late initiation was still readily detectable, suggesting that there is a limited number of late transcription factors, or that the factors are stably bound in a complex. After the glycerol gradient ultracentrifugation step, SDS–PAGE showed fewer than 10 prominent polypeptides remaining in the active fractions, which suggests a high degree of purity of the transcription machinery
Isolation of a Mutant Bacteriophage T7 Deleted in Nonessential Genetic Elements, Gene19.5andm

AbstractHalf of the 55 potential genes of bacteriophage T7 appear to be dispensable. One of the major obstacles in the study of these nonessential genes is the difficulty in obtaining mutants. During a study of genes involved in the packaging of bacteriophage T7, we hypothesized that some nonessential genes may be required for optimal growth. Mutant phages lacking such nonessential genes may form plaques but grow slowly. One gene located at the extreme right end of the linear T7 genome, gene19.5with no known mutants, and a genetic elementmresponsible for a unique hairpin end, were studied. Mutant T7 phages deleted in gene19.5andm(T7Δ19.5-M) were generatedin vivoby homologous recombination with a recombinant plasmid. This phage produces small plaques and the production of progeny phage particles per infected cell was reduced fourfold. Investigation of the intracellular DNA after infection with T7Δ19.5-Mshowed the persistence ofEscherichia coliDNA as well as delayed conversion of concatemers to unit-length T7 DNA. The inefficiency of concatemer processing confirmed the proposed function of the M-hairpin in duplication of the concatemer junction. Since it is not likely that the M-hairpin influences the degradation of host DNA, we propose that the gene19.5product is partly responsible for the degradation ofE. colichromosomal DNA
Inhibition of VSV Genome RNA Replication but Not Transcription by Monoclonal Antibodies Specific for the Viral P Protein

AbstractThe growth of vesicular stomatitis virus requires two distinct RNA synthetic events: transcription of messenger RNA molecules and replication of the viral genome RNA. We report the use of a panel of monoclonal antibodies directed against the viral phosphoprotein P in an attempt to assess the role of this protein in RNA synthesis. Using extracts derived from virus-infected cells, we show that several anti-P monoclonal antibodies can have an inhibitory effect on genome RNA replication by binding to a soluble form of the P protein. We also show that the P protein to which one of these antibodies (6D11) is directed is not complexed with the N protein and that the amount of soluble P protein that binds to the 6D11 antibody in immunoprecipitation reactions can be increased by treating extracts with alkaline phosphatase. In addition, phosphatase treatment of infected cell extracts results in an increased level of genome RNA replication. These results suggest that a soluble subspecies of the P protein that functions in genome RNA replication exists in infected cells and that this species of the P protein is not required for transcription