bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mutant Cells Selected during Persistent Reovirus Infection Do Not Express Mature Cathepsin L and Do Not Support Reovirus Disassembly
Authors: Baer Geoffrey S. , Ebert Daniel H. , Chung Chia J. , Erickson Ann H. , Dermody Terence S. 
Published: December 2019

ABSTRACT
Persistent reovirus infections of murine L929 cells select cellular mutations that inhibit viral disassembly within the endocytic pathway. Mutant cells support reovirus growth when infection is initiated with infectious subvirion particles (ISVPs), which are intermediates in reovirus disassembly formed following proteolysis of viral outer-capsid proteins. However, mutant cells do not support growth of virions, indicating that these cells have a defect in virion-to-ISVP processing. To better understand mechanisms by which viruses use the endocytic pathway to enter cells, we defined steps in reovirus replication blocked in mutant cells selected during persistent infection. Subcellular localization of reovirus after adsorption to parental and mutant cells was assessed using confocal microscopy and virions conjugated to a fluorescent probe. Parental and mutant cells did not differ in the capacity to internalize virions or distribute them to perinuclear compartments. Using pH-sensitive probes, the intravesicular pH was determined and found to be equivalent in parental and mutant cells. In both cell types, virions localized to acidified intracellular organelles. The capacity of parental and mutant cells to support proteolysis of reovirus virions was assessed by monitoring the appearance of disassembly intermediates following adsorption of radiolabeled viral particles. Within 2 h after adsorption to parental cells, proteolysis of viral outer-capsid proteins was observed, consistent with formation of ISVPs. However, in mutant cells, no proteolysis of viral proteins was detected up to 8 h postadsorption. Since treatment of cells with E64, an inhibitor of cysteine-containing proteases, blocks reovirus disassembly, we used immunoblot analysis to assess the expression of cathepsin L, a lysosomal cysteine protease. In contrast to parental cells, mutant cells did not express the mature, proteolytically active form of the enzyme. The defect in cathepsin L maturation was not associated with mutations in procathepsin L mRNA, was not complemented by procathepsin L overexpression, and did not affect the maturation of cathepsin B, another lysosomal cysteine protease. These findings indicate that persistent reovirus infections select cellular mutations that affect the maturation of cathepsin L and suggest that alterations in the expression of lysosomal proteases can modulate viral cytopathicity.
Proliferation Response to Interleukin-2 and Jak/Stat Activation of T Cells Immortalized by Human T-Cell Lymphotropic Virus Type 1 Is Independent of Open Reading Frame I Expression
Authors: Collins Nathaniel D. , D’Souza Celine , Albrecht Björn , Robek Michael D. , Ratner Lee , Ding Wei , Green Patrick L. , Lairmore Michael D. 
Published: December 2019

ABSTRACTHuman T-cell lymphotropic virus type 1 (HTLV-1), a complex retrovirus, encodes a hydrophobic 12-kD protein from pX open reading frame (ORF) I that localizes to cellular endomembranes and contains four minimal SH3 binding motifs (PXXP). We have demonstrated the importance of ORF I expression in the establishment of infection and hypothesize that p12Ihas a role in T-cell activation. In this study, we tested interleukin-2 (IL-2) receptor expression, IL-2-mediated proliferation, and Jak/Stat activation in T-cell lines immortalized with either wild-type or ORF I mutant clones of HTLV-1. All cell lines exhibited typical patterns of T-cell markers and maintained mutation fidelity. No significant differences between cell lines were observed in IL-2 receptor chain (α, β, or γc) expression, in IL-2-mediated proliferation, or in IL-2-induced phosphorylated forms of Stat3, Stat5, Jak1, or Jak3. The expression of ORF I is more likely to play a role in early HTLV-1 infection, such as in the activation of quiescent T cells in vivo.
Multiple Effects of an Anti-Human Immunodeficiency Virus Nucleocapsid Inhibitor on Virus Morphology and Replication
Authors: Berthoux Lionel , Péchoux Christine , Darlix Jean-Luc 
Published: December 2019

ABSTRACT
Human immunodeficiency virus type 1 nucleocapsid protein is a major structural component of the virion core and a key factor involved in proviral DNA synthesis and virus formation. 2,2′-Dithiobenzamides (DIBA-1) and related compounds that are inhibitors of NCp7 are thought to eject zinc ions from NCp7 zinc fingers, inhibiting the maturation of virion proteins. Here, we show that the presence of DIBA-1 at the time of virus formation causes morphological malformations of the virus and reduces proviral DNA synthesis. Thus, it seems that DIBA-1 is responsible for a “core-freezing effect,” as shown by electron microscopy analyses. DIBA-1 can also directly interfere with the fate of the newly made proviral DNA in a manner independent of its effects on virion core formation. These data strongly suggest that nucleocapsid protein is a prime target for new compounds aimed at inhibiting human immunodeficiency virus and other retroviruses.
Molecular Mechanisms of Coxsackievirus Persistence in Chronic Inflammatory Myopathy: Viral RNA Persists through Formation of a Double-Stranded Complex without Associated Genomic Mutations or Evolution
Authors: Tam Patricia E. , Messner Ronald P. 
Published: December 2019

ABSTRACT
Enterovirus infection and persistence have been implicated in the pathogenesis of certain chronic muscle diseases. In vitro studies suggest that persistent enteroviruses mutate, evolving into forms that are less lytic and display altered tropism, but it is less clear whether these mechanisms operate in vivo. In this study, persistent coxsackievirus RNA from the muscle of mice afflicted with chronic inflammatory myopathy (CIM) was characterized and compared with RNA from a virus that had established a persistent infection of G8 mouse myoblasts for 30 passages in vitro. Competitive strand-specific reverse transcription-PCR and susceptibility to RNase I treatment revealed that plus- and minus-strand viral RNAs were present at nearly equivalent levels in muscle and that they persisted in a double-stranded conformation. All regions of the viral genome persisted and were amplified as a series of seven overlapping fragments. Restriction endonuclease fingerprinting coupled with sequencing indicated that there was no evolution of the viral genome associated with its persistence in muscle. This contrasted with the productive persistent infection that was established in myoblast cultures, where plus-strand RNA predominated and persistent virus developed distinct mutations. In vitro persistence proceeded by a carrier culture mechanism and was completely dependent on production of infectious virus, since persistent viral RNA was not detected in cultures subjected to antibody-mediated curing. These experiments demonstrate that persistence of coxsackievirus RNA in muscle is not facilitated by distinct genetic changes in the virus that give rise to replication-defective forms but occurs primarily through production of stable double-stranded RNA that is produced as the acute viral infection resolves. The data suggest a mechanism for coxsackievirus persistence in myofibers and perhaps other nondividing cells whereby cells that survive infection could harbor persistent viral RNA for extended times without producing detectable levels of infectious virus.
Caspase-Dependent N-Terminal Cleavage of Influenza Virus Nucleocapsid Protein in Infected Cells
Authors: Zhirnov O. P. , Konakova T. E. , Garten W. , Klenk H.-D. 
Published: December 2019

ABSTRACT
The nucleocapsid protein (NP) (56 kDa) of human influenza A viruses is cleaved in infected cells into a 53-kDa form. Likewise, influenza B virus NP (64 kDa) is cleaved into a 55-kDa protein with a 62-kDa intermediate (O. P. Zhirnov and A. G. Bukrinskaya, Virology 109:174–179, 1981). We show now that an antibody specific for the N terminus of influenza A virus NP reacted with the uncleaved 56-kDa form but not with the truncated NP53 form, indicating the removal of a 3-kDa peptide from the N terminus. Amino acid sequencing revealed the cleavage sites ETD16*G for A/Aichi/68 NP and sites DID7*G and EAD61*V for B/Hong Kong/72 NP. With D at position −1, acidic amino acids at position −3, and aliphatic ones at positions −2 and +1, the NP cleavage sites show a recognition motif typical for caspases, key enzymes of apoptosis. These caspase cleavage sites demonstrated evolutionary stability and were retained in NPs of all human influenza A and B viruses. NP of avian influenza viruses, which is not cleaved in infected cells, contains G instead of D at position 16. Oligopeptide DEVD derivatives, specific caspase inhibitors, were shown to prevent the intracellular cleavage of NP. All three events, the NP cleavage, the increase of caspase activity, and the development of apoptosis, coincide in cells infected with human influenza A and B viruses. The data suggest that intracellular cleavage of NP is exerted by host caspases and is associated with the development of apoptosis at the late stages of infection.
Induction of Endogenous Genes following Infection of Human Endothelial Cells with an E1−E4+Adenovirus Gene Transfer Vector
Authors: Ramalingam Ramachandran , Rafii Shahin , Worgall Stefan , Hackett Neil R. , Crystal Ronald G. 
Published: December 2019

ABSTRACTRecombinant adenovirus (Ad) gene transfer vectors are effective at transferring exogenous genes to a variety of cells and tissue types both in vitro and in vivo. However, in the process of gene transfer, the Ad vectors induce the expression of target cell genes, some of which may modify the function of the target cell and/or alter the local milieu. To develop a broader understanding of Ad vector-mediated induction of endogenous gene expression, genes induced by first-generation E1−E4+Ad vectors in primary human umbilical vein endothelial cells were identified by cDNA subtraction cloning. The identified cDNAs included signaling molecules (lymphoid blast crisis [LBC], guanine nucleotide binding protein α type S [Gα-S], and mitogen kinase [MEK5]), calcium-regulated/cytoskeletal proteins (calpactin p11 and p36 subunits, vinculin, and spinocerebellar ataxia [SCA1]), growth factors (insulin-like growth factor binding protein 4 and transforming growth factor β2), glyceraldehyde-6-phosphate dehydrogenase, an expressed sequence tag, and a novel cDNA showing homology to a LIM domain sequence. Two- to sevenfold induction of the endogenous gene expression was observed at 24 h postinfection, and induction continued up to 72 h, although the timing of gene expression varied among the identified genes. In contrast to that observed in endothelial cells, the Ad vector-mediated induction of gene expression was not found following Ad vector infection of primary human dermal fibroblasts or human alveolar macrophages. Empty Ad capsids did not induce endogenous gene expression in endothelial cells. Interestingly, additional deletion of the E4 gene obviated the upregulation of genes in endothelial cells by the E1−E3−Ad vector, suggesting that genes carried by the E4 region play a central role in modifying target cell gene expression. These findings are consistent with the notion that efficient transfer of exogenous genes to endothelial cells by first-generation Ad vectors comes with the price that these vectors also induce the expression of a variety of cellular genes.
Altering the Cellular Location of an Antigen Expressed by a DNA-Based Vaccine Modulates the Immune Response
Authors: Lewis P. J. , van Drunen Littel-van den Hurk S. , Babiuk L. A. 
Published: December 2019

ABSTRACTThe potential for DNA vaccines encoding mutated versions of the same antigen to modulate immune responses in C3H/HeN mice was investigated. We created expression plasmids that encoded several versions of glycoprotein D (gD) from bovine herpesvirus 1, including authentic membrane-anchored glycoprotein (pSLRSV.AgD), a secreted glycoprotein (pSLRSV.SgD), and an intracellular protein (pSLRSV.CgD). Immunization of an inbred strain of mice with these plasmids resulted in highly efficacious and long-lasting humoral and cell-mediated immunity. We also demonstrated that the cell compartment in which plasmid-encoded gD was expressed caused a deviation in the serum immunoglobulin (Ig) isotype profile as well as the predominant cytokines secreted from the draining lymph node. Immunization of C3H/HeN mice with DNA vaccines encoding cell-associated forms of gD resulted in a predominance of serum IgG2a and gamma interferon-secreting cells within the spleens and draining lymph nodes. In contrast, mice immunized with a secreted form of this same antigen displayed immune responses characterized by greater levels of interleukin 4 in the draining lymph node and IgG1 as the predominant serum isotype. We also showed evidence of compartmentalization of distinct immune responses within different lymphoid organs.
Dependence of Echovirus 9 on the Enterovirus RNA Replication Inhibitor 2-(α-Hydroxybenzyl)-Benzimidazole Maps to Nonstructural Protein 2C
Authors: Hadaschik Dirk , Klein Marcus , Zimmermann Holger , Eggers Hans J. , Nelsen-Salz Birgit 
Published: December 2019

ABSTRACT

HBB [2-(α-hydroxybenzyl)-benzimidazole] selectively inhibits RNA synthesis of most enteroviruses. However, isolation of HBB-dependent variants is possible. Sequence analysis and characterization of recombinant viruses revealed that HBB dependence maps to the nonstructural protein 2C. A single point mutation at position C
4782
U is sufficient to establish the HBB-dependent phenotype in our echovirus 9 model.
Persistent CCR5 Utilization and Enhanced Macrophage Tropism by Primary Blood Human Immunodeficiency Virus Type 1 Isolates from Advanced Stages of Disease and Comparison to Tissue-Derived Isolates
Authors: Li Shan , Juarez Julius , Alali Mohammed , Dwyer Dominic , Collman Ronald , Cunningham Anthony , Naif Hassan M. 
Published: December 2019

ABSTRACTViral phenotype, tropism, coreceptor usage, and envelope gene diversity were examined in blood isolates collected from 27 individuals at different stages of human immunodeficiency virus type 1 (HIV-1) disease and tissue derived isolates from 10 individuals with AIDS. The majority (89%) of blood and all tissue HIV-1 isolates from all stages of infection were non-syncytium inducing and macrophage (M) tropic. Tropism and productive infection by HIV isolates in both monocytes and monocyte-derived macrophages (MDM) increased in advanced disease (HIV tropism for monocytes, 1 of 6 from categories I and II versus 11 of 21 [P= 0.05] from category IV and II [CD4 < 250]; and high-level replication in MDM, 1 of 6 from categories I and II versus 16 of 21 from categories IV and II [P= 0.015]). There was a high level of replication of blood and tissue isolates in T lymphocytes without restriction at any stage. Overall, the level of replication in MDM was 5- to 10-fold greater than in monocytes, with restriction in the latter occurring mainly at entry and later stages of replication. Only three blood isolates were identified as syncytium inducing, and all had a dualtropic phenotype. There was a significant increase of HIV envelope gene diversity, as shown by a heteroduplex mobility assay, in advanced disease; this may partly underlie the increase of HIV replication in MDM. Unlike blood isolates (even those from patients with advanced disease), tissue isolates displayed greater similarities (90%) in productive infection between MDM and monocytes. The majority (87%) of all isolates, including those from patients with advanced disease, used CCR5, and only 5 of 37 isolates showed expanded coreceptor usage. These results indicate that in the late stage of disease with increasing viral load and diversity, CCR5 utilization and M-tropism persist in blood and tissue and the replicative ability in macrophages increases. This suggests that these characteristics are advantageous to HIV and are important to disease progression.
Similar Interactions of the Poliovirus and Rhinovirus 3D Polymerases with the 3′ Untranslated Region of Rhinovirus 14
Authors: Meredith Janet M. , Rohll Jonathan B. , Almond Jeffrey W. , Evans David J. 
Published: December 2019

ABSTRACT
We showed previously that a human rhinovirus 14 (HRV14) 3′ untranslated region (3′ UTR) on a poliovirus genome was able to replicate with nearly wild-type kinetics (J. B. Rohll, D. H. Moon, D. J. Evans, and J. W. Almond, J. Virol 69:7835–7844, 1995). This enabled the HRV14 single 3′ UTR stem-loop structure to be studied in combination with a sensitive reporter system, poliovirus FLC/REP, in which the capsid coding region is replaced by an in-frame chloramphemicol acetyltransferase (CAT) gene. Using such a construct, we identified a mutant (designated mut4), in which the structure and stability of the stem were predicted to be maintained, that replicated very poorly as determined by its level of CAT activity. The effect of this mutant 3′ UTR on replication has been further investigated by transferring it onto the full-length cDNAs of both poliovirus type 3 (PV3) and HRV14. Virus was recovered with a parental plaque phenotype at a low frequency, indicating the acquisition of compensating changes, which sequence analysis revealed were, in both poliovirus- and rhinovirus-derived viruses, located in the active-site cleft of 3D polymerase and involved the substitution of Asn18 for Tyr. These results provide further evidence of a specific interaction between the 3′ UTR of picornaviruses and the viral polymerase and also indicate similar interactions of the 3′ UTR of rhinovirus with both poliovirus and rhinovirus polymerases.
Germ Cell Expression of an Isolated Human Endogenous Retroviral Long Terminal Repeat of the HERV-K/HTDV Family in Transgenic Mice
Authors: Casau Armelle E. , Vaughan Joe E. , Lozano Guillermina , Levine Arnold J. 
Published: December 2019

ABSTRACT

In contrast to most other human endogenous retroviral families, various HERV-K members have open reading frames that code for functional viral proteins which can form noninfectious particles in some germ cell tumors. The HERV-K viral genes are highly transcribed in germ cell tumors but are transcribed to lower or undetectable levels in most other tissue and tumor types. To further analyze the expression patterns of these proviruses, long terminal repeats (LTRs) were isolated from the human genome and used in reporter gene assays. Expression of some HERV-K LTRs was found to be high in human and murine germ cell tumors (testicular teratocarcinomas) and low in non-germ-cell tumors. Furthermore, upon differentiation of a teratocarcinoma cell line, the expression of an active LTR dropped dramatically, suggesting developmental regulation of these proviral LTRs. Transgenic mice harboring an active LTR driving
lacZ
expression were generated and analyzed. Adult mouse testes showed the highest levels of expression, and the transgene staining appeared to be restricted primarily to the more undifferentiated spermatocytes. Most other tissues analyzed revealed very low or undetectable levels of expression both by reverse transcription-PCR and by Northern blot analysis. Whether the restricted expression of HERV-K in germ cells and in germ cell-derived tumors is of significant importance during development or tumorigenesis remains to be elucidated. Germ line expression of these viruses would allow for their expansion and movement, while somatic repression would ensure limited insertional mutagenesis and misexpression in an individual.
A Replication-Incompetent Adenovirus Vector with the Preterminal Protein Gene Deleted Efficiently Transduces Mouse Ears
Authors: Moorhead John W. , Clayton Gerald H. , Smith Roderic L. , Schaack Jerome 
Published: December 2019

ABSTRACT

Adenoviruses offer great potential as gene therapy agents but are limited by the strong inflammatory response that occurs in response to the recombinant virus. Since the degree of inflammation correlates in part with the potential of the viral vector for replication, we constructed a preterminal protein (pTP) deletion mutant adenovirus type 5 vector, Ad5
dl
308
ΔpTP
β-gal, that is replication incompetent due to deletion of the pTP gene and that has the E1 genes replaced by the
Escherichia coli lacZ
reporter gene under the control of the cytomegalovirus major immediate-early promoter. This virus was compared with a first-generation, replication-defective adenovirus vector, Ad5
dl
308β-gal, that is isogenic except that it contains a wild-type pTP gene. To examine transduction efficiency and induction of inflammation, we developed a novel system involving intradermal injection of BALB/c mouse ears. Mouse ears can be accurately measured to determine the degree of edema as an indirect measurement of inflammation. Edema and inflammation were induced in a dose- and time-dependent manner by both viruses and correlated well. LacZ activity correlated inversely with edema and inflammation. The pTP-defective vector Ad5
dl
308
ΔpTP
β-gal transduced mouse ears much more efficiently and induced edema and inflammatory cell infiltration approximately 10-fold less efficiently than the first-generation vector Ad5
dl
308β-gal. The diminished inflammatory response and increased efficiency of transduction observed with Ad5
dl
308
ΔpTP
β-gal indicate its promise as a gene therapy agent for other tissues. The results also demonstrate that the mouse ear model offers potential for the study of adenovirus-induced inflammation because of the ready access of the ears, the relative ease of continuous measurement, and the sensitivity to adenovirus transducing vectors.
Conserved Cysteines of the Human Immunodeficiency Virus Type 1 Protease Are Involved in Regulation of Polyprotein Processing and Viral Maturation of Immature Virions
Authors: Davis David A. , Yusa Keisuke , Gillim Laura A. , Newcomb Fonda M. , Mitsuya Hiroaki , Yarchoan Robert 
Published: December 2019

ABSTRACT

We investigated the role of the two highly conserved cysteine residues, cysteines 67 and 95, of the human immunodeficiency virus type 1 (HIV-1) protease in regulating the activity of that protease during viral maturation. To this end, we generated four HIV-1 molecular clones: the wild type, containing both cysteine residues; a protease mutant in which the cysteine at position 67 was replaced by an alanine (C67A); a C95A protease mutant; and a double mutant (C67A C95A). When immature virions were produced in the presence of an HIV-1 protease inhibitor, KNI-272, and the inhibitor was later removed, limited polyprotein processing was observed for wild-type virion preparations over a 20-h period. Treatment of immature wild-type virions with the reducing agent dithiothreitol considerably improved the rate and extent of Gag processing, suggesting that the protease is, in part, reversibly inactivated by oxidation of the cysteine residues. In support of this, C67A C95A virions processed Gag up to fivefold faster than wild-type virions in the absence of a reducing agent. Furthermore, oxidizing agents, such as H
2
O
2
and diamide, inhibited Gag processing of wild-type virions, and this effect was dependent on the presence of cysteine 95. Electron microscopy revealed that a greater percentage of double-mutant virions than wild-type virions developed a mature-like morphology on removal of the inhibitor. These studies provide evidence that under normal culture conditions the cysteines of the HIV-1 protease are susceptible to oxidation during viral maturation, thus preventing immature virions from undergoing complete processing following their release. This is consistent with the cysteines being involved in the regulation of viral maturation in cells under oxidative stress.