bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Hemagglutinin Surface Density in the Initial Stages of Influenza Virus Fusion: Lack of Evidence for Cooperativity
Authors: Günther-Ausborn Susanne , Schoen Pieter , Bartoldus Ingrid , Wilschut Jan , Stegmann Toon 
Published: July 2002

ABSTRACT
Membrane fusion mediated by influenza virus hemagglutinin (HA) is believed to proceed via the cooperative action of multiple HA trimers. To determine the minimal number of HA trimers required to trigger fusion, and to assess the importance of cooperativity between these HA trimers, we have generated virosomes containing coreconstituted HAs derived from two strains of virus with different pH dependencies for fusion, X-47 (optimal fusion at pH 5.1; threshold at pH 5.6) and A/Shangdong (optimal fusion at pH 5.6; threshold at pH 6.0), and measured fusion of these virosomes with erythrocyte ghosts by a fluorescence lipid mixing assay. Virosomes with different X-47-to-A/Shangdong HA ratios, at a constant HA-to-lipid ratio, showed comparable ghost-binding activities, and the low-pH-induced conformational change of A/Shangdong HA did not affect the fusion activity of X-47 HA. The initial rate of fusion of these virosomes at pH 5.7 increased directly proportional to the surface density of A/Shangdong HA, and a single A/Shangdong trimer per virosome appeared to suffice to induce fusion. The reciprocal of the lag time before the onset of fusion was directly proportional to the surface density of fusion-competent HA. These results support the notion that there is no cooperativity between HA trimers during influenza virus fusion.
A Recombinant Human Parainfluenza Virus Type 3 (PIV3) in Which the Nucleocapsid N Protein Has Been Replaced by That of Bovine PIV3 Is Attenuated in Primates
Authors: Bailly Jane E. , McAuliffe Josephine M. , Durbin Anna P. , Elkins William R. , Collins Peter L. , Murphy Brian R. 
Published: July 2002

ABSTRACT
The shipping fever (SF) and Kansas (Ka) strains of bovine parainfluenza virus type 3 (BPIV3) are restricted in their replication in rhesus monkeys 100- to 1,000-fold compared to human parainfluenza virus type 3 (HPIV3), and the Ka strain also was shown to be attenuated in humans. To initiate an investigation of the genetic basis of the attenuation of BPIV3 in primates, we produced viable chimeric HPIV3 recombinants containing the nucleoprotein (N) open reading frame (ORF) from either BPIV3 Ka or SF in place of the HPIV3 N ORF. These chimeric recombinants were designated cKa-N and cSF-N, respectively. Remarkably, cKa-N and cSF-N grew to titers comparable to those of their HPIV3 and BPIV3 parents in LLC-MK2 monkey kidney and Madin-Darby bovine kidney cells. Thus, the heterologous nature of the N protein did not impede replication in vitro. However, cKa-N and cSF-N were each restricted in replication in rhesus monkeys to a similar extent as Ka and SF, respectively. This identified the BPIV3 N protein as a determinant of the host range restriction of BPIV3 in primates. These chimeras thus combine the antigenic determinants of HPIV3 with the host range restriction and attenuation phenotype of BPIV3. Despite their restricted replication in rhesus monkeys, the chimeric viruses induced a level of resistance to HPIV3 challenge in these animals which was indistinguishable from that conferred by immunization with HPIV3. The infectivity, attenuation, and immunogenicity of these BPIV3/HPIV3 chimeras suggest that the modified Jennerian approach described in the present report represents a novel method to design vaccines to protect against HPIV3-induced disease in humans.
Cospeciation and Horizontal Transmission of Avian Sarcoma and Leukosis Virus
gag
Genes in Galliform Birds
Authors: Dimcheff Derek E. , Drovetski Sergei V. , Krishnan Mallika , Mindell David P. 
Published: July 2002

ABSTRACT

In a study of the evolution and distribution of avian retroviruses, we found avian sarcoma and leukosis virus (ASLV)
gag
genes in 26 species of galliform birds from North America, Central America, eastern Europe, Asia, and Africa. Nineteen of the 26 host species from whom ASLVs were sequenced were not previously known to contain ASLVs. We assessed congruence between ASLV phylogenies based on a total of 110
gag
gene sequences and ASLV-host phylogenies based on mitochondrial 12S ribosomal DNA and ND2 sequences to infer coevolutionary history for ASLVs and their hosts. Widespread distribution of ASLVs among diverse, endemic galliform host species suggests an ancient association. Congruent ASLV and host phylogenies for two species of
Perdix
, two species of
Gallus
, and
Lagopus lagopus
and
L. mutus
also indicate an old association with vertical transmission and cospeciation for these ASLVs and hosts. An inference of horizontal transmission of ASLVs among some members of the Tetraoninae subfamily (grouse and ptarmigan) is supported by ASLV monophyletic groups reflecting geographic distribution and proximity of hosts rather than host species phylogeny. We provide a preliminary phylogenetic taxonomy for the new ASLVs, in which named taxa denote monophyletic groups.
Transfer of Primer Binding Site-Mutated Simian Immunodeficiency Virus Vectors by Genetically Engineered Artificial and Hybrid tRNA-Like Primers
Authors: Hansen Anette Chemnitz , Grunwald Thomas , Lund Anders Henrik , Schmitz Alexander , Duch Mogens , Überla Klaus , Pedersen Finn Skou 
Published: July 2002

ABSTRACT

Simian immunodeficiency viruses (SIV) harbor primer binding sites (PBS) matching tRNA

3

Lys

or tRNA

5

Lys

. To study determinants of primer usage in SIV, a SIVmac239-based vector was impaired by mutating the PBS to a sequence (PBS-X2) with no match to any tRNA. By cotransfection of a synthetic gene encoding a tRNA
Pro
-like RNA with a match to PBS-X2, the activity of this vector could be restored to a transduction efficiency slightly lower than that of the wild-type vector. A vector with a PBS matching tRNA
Pro
was functional at a level slightly below that of the wild-type vector, but higher transduction efficiency could be obtained by cotransfection of a gene for an engineered tRNA
Pro
-tRNA

3

Lys

hybrid with a match to PBS-Pro. The importance of tRNA backbone identity was further analyzed by complementing the PBS-X2 vector with a gene for a matching x2 primer with a tRNA

3

Lys

backbone, which led to three- to fourfold-higher titers than those observed for the x2 primer with the tRNA
Pro
backbone. In summary, our results demonstrate flexibility in PBS and primer usage for SIVmac239, with PBS-primer complementarity being the major determinant, in analogy with previous findings for murine leukemia viruses and human immunodeficiency virus type 1.
Regulation of mRNA Translation and Cellular Signaling by Hepatitis C Virus Nonstructural Protein NS5A
Authors: He Yupeng , Tan Seng-Lai , Tareen Semih U. , Vijaysri Sangeetha , Langland Jeffrey O. , Jacobs Bertram L. , Katze Michael G. 
Published: July 2002

ABSTRACTThe NS5A nonstructural protein of hepatitis C virus (HCV) has been shown to inhibit the cellular interferon (IFN)-induced protein kinase R (PKR). PKR mediates the host IFN-induced antiviral response at least in part by inhibiting mRNA translation initiation through phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α). We thus examined the effect of NS5A inhibition of PKR on mRNA translation within the context of virus infection by using a recombinant vaccinia virus (VV)-based assay. The VV E3L protein is a potent inhibitor of PKR. Accordingly, infection of IFN-pretreated HeLa S3 cells with an E3L-deficient VV (VVΔE3L) resulted in increased phosphorylation levels of both PKR and eIF2α. IFN-pretreated cells infected with VV in which theE3Llocus was replaced with theNS5Agene (VVNS5A) displayed diminished phosphorylation of PKR and eIF2α in a transient manner. We also observed an increase in activation of p38 mitogen-activated protein kinase in IFN-pretreated cells infected with VVΔE3L, consistent with reports that p38 lies downstream of the PKR pathway. Furthermore, these cells exhibited increased phosphorylation of the cap-binding initiation factor 4E (eIF4E), which is downstream of the p38 pathway. Importantly, these effects were reduced in cells infected with VVNS5A. NS5A was also found to inhibit activation of the p38-eIF4E pathway in epidermal growth factor-treated cells stably expressing NS5A. NS5A-induced inhibition of eIF2α and eIF4E phosphorylation may exert counteracting effects on mRNA translation. Indeed, IFN-pretreated cells infected with VVNS5A exhibited a partial and transient restoration of cellular and viral mRNA translation compared with IFN-pretreated cells infected with VVΔE3L. Taken together, these results support the role of NS5A as a PKR inhibitor and suggest a potential mechanism by which HCV might maintain global mRNA translation rate during early virus infection while favoring cap-independent translation of HCV mRNA during late infection.
Cytomegalovirus Basic Phosphoprotein (pUL32) Binds to Capsids In Vitro through Its Amino One-Third
Authors: Baxter Michael K. , Gibson Wade 
Published: July 2002

ABSTRACT
The cytomegalovirus (CMV) basic phosphoprotein (BPP) is a component of the tegument. It remains with the nucleocapsid fraction under conditions that remove most other tegument proteins from the virion, suggesting a direct and perhaps tight interaction with the capsid. As a step toward localizing this protein within the molecular structure of the virion and understanding its function during infection, we have investigated the BPP-capsid interaction. In this report we present evidence that the BPP interacts selectively, through its amino one-third, with CMV capsids. Radiolabeled simian CMV (SCMV) BPP, synthesized in vitro, bound to SCMV B-capsids, and C-capsids to a lesser extent, following incubation with either isolated capsids or lysates of infected cells. Human CMV (HCMV) BPP (pUL32) also bound to SCMV capsids, and SCMV BPP likewise bound to HCMV capsids, indicating that the sequence(s) involved is conserved between the two proteins. Analysis of SCMV BPP truncation mutants localized the capsid-binding region to the amino one-third of the molecule—the portion of BPP showing the greatest sequence conservation between the SCMV and HCMV homologs. This general approach may have utility in studying the interactions of other proteins with conformation-dependent binding sites.
Downstream Sequences Influence the Choice between a Naturally Occurring Noncanonical and Closely Positioned Upstream Canonical Heptameric Fusion Motif during Bovine Coronavirus Subgenomic mRNA Synthesis
Authors: Ozdarendeli Aykut , Ku Seulah , Rochat Sylvie , Williams Gwyn D. , Senanayake Savithra D. , Brian David A. 
Published: July 2002

ABSTRACT

Mechanisms leading to subgenomic mRNA (sgmRNA) synthesis in coronaviruses are poorly understood but are known to involve a heptameric signaling motif, originally called the intergenic sequence. The intergenic sequence is the presumed crossover region (fusion site) for RNA-dependent RNA polymerase (RdRp) during discontinuous transcription, a process leading to sgmRNAs that are both 5′ and 3′ coterminal. In the bovine coronavirus, the major fusion site for synthesis of mRNA 5 (
GG
UA
G
AC) does not conform to the canonical motif (UC[U,C]AAAC) at three positions (underlined), yet it lies just 14 nucleotides downstream from such a sequence (UCCAAAC). The infrequently used canonical sequence, by computer prediction, is buried within the stem of a stable hairpin (−17.2 kcal/mol). Here we document the existence of this stem by enzyme probing and examine its influence and that of neighboring sequences on the unusual choice of fusion sites by analyzing transcripts made in vivo from mutated defective interfering RNA constructs. We learned that (i) mutations that were predicted to unfold the stem-loop in various ways did not switch RdRp crossover to the upstream canonical site, (ii) a totally nonconforming downstream motif resulted in no measurable transcription from either site, (iii) the canonical upstream site does not function ectopically to lend competence to the downstream noncanonical site, and (iv) altering flanking sequences downstream of the downstream noncanonical motif in ways that diminish sequence similarity with the virus genome 5′ end caused a dramatic switch to the upstream canonical site. These results show that sequence elements downstream of the noncanonical site can dramatically influence the choice of fusion sites for synthesis of mRNA 5 and are interpreted as being most consistent with a mechanism of similarity-assisted RdRp strand switching during minus-strand synthesis.
Expression and Immunogenicity of Human Immunodeficiency Virus Type 1 Gag Expressed by a Replication-Competent Rhabdovirus-Based Vaccine Vector
Authors: McGettigan James P. , Sarma Satyam , Orenstein Jan M. , Pomerantz Roger J. , Schnell Matthias J. 
Published: July 2002

ABSTRACT

A replication-competent rhabdovirus-based vector expressing human immunodeficiency virus type 1 (HIV-1) Gag protein was characterized on human cell lines and analyzed for the induction of a cellular immune response in mice. We previously described a rabies virus (RV) vaccine strain-based vector expressing HIV-1 gp160. The recombinant RV was able to induce strong humoral and cellular immune responses against the HIV-1 envelope protein in mice (M. J. Schnell et al., Proc. Natl. Acad. Sci. USA 97:3544–3549, 2000; J. P. McGettigan et al., J. Virol. 75:4430–4434, 2001). Recent research suggests that the HIV-1 Gag protein is another important target for cell-mediated host immune defense. Here we show that HIV-1 Gag can efficiently be expressed by RV on both human and nonhuman cell lines. Infection of HeLa cells with recombinant RV expressing HIV-1 Gag resulted in efficient expression of HIV-1 precursor protein p55 as indicated by both immunostaining and Western blotting. Moreover, HIV-1 p24 antigen capture enzyme-linked immunosorbent assay and electron microscopy showed efficient release of HIV-1 virus-like particles in addition to bullet-shaped RV particles in the supernatants of the infected cells. To initially screen the immunogenicity of this new vaccine vector, BALB/c mice received a single vaccination with the recombinant RV expressing HIV-1 Gag. Immunized mice developed a vigorous CD8
+
cytotoxic T-lymphocyte response against HIV-1 Gag. In addition, 26.8% of CD8
+
T cells from mice immunized with RV expressing HIV-1 Gag produced gamma interferon after challenge with a recombinant vaccinia virus expressing HIV-1 Gag. These results further confirm and extend the potency of RV-based vectors as a potential HIV-1 vaccine.
Assembly and Catalysis of Concerted Two-End Integration Events by Moloney Murine Leukemia Virus Integrase
Authors: Yang Fan , Roth Monica J. 
Published: July 2002

ABSTRACT
Retroviral integration results in the stable and coordinated insertion of the two termini of the linear viral DNA into the host genome. An in vitro concerted two-end integration reaction catalyzed by the Moloney murine leukemia virus (M-MuLV) integrase (IN) was used to investigate the binding and coordination of the two viral DNA ends. Comparison of the two-end integration and strand transfer assays indicates that zinc is required for efficient concerted integration utilizing plasmid DNA as target. Complementation assays using a pair of nonoverlapping integrase domains, consisting of the HHCC domain and the core/C-terminal region, yielded products containing the correct 4-base target site duplication. The efficiency of the coordinated two-end integration varied depending on the order of addition of the individual protein and DNA components in the complementation assay. Two-end integration was most efficient when the long terminal repeat (LTR) was premixed with either the target DNA or the HHCC domain. The preference for two-end integration through preincubation of the HHCC finger with the viral DNA supports the role of this domain in the recognition and/or positioning of the LTR.
Interleukin-12- and Gamma Interferon-Dependent Innate Immunity Are Essential and Sufficient for Long-Term Survival of Passively Immunized Mice Infected with Herpes Simplex Virus Type 1
Authors: Vollstedt Sabine , Franchini Marco , Alber Gottfried , Ackermann Mathias , Suter Mark 
Published: July 2002

ABSTRACTInterferon (IFN) type I (alpha/beta IFN [IFN-α/β]) is very important in directly controlling herpes simplex virus type I (HSV-1) replication as well as in guiding and upregulating specific immunity against this virus. By contrast, the roles of IFN type II (IFN-γ) and antibodies in the defense against HSV-1 are not clear. Mice without a functional IFN system and no mature B and T cells (AGR mice) did not survive HSV-1 infection in the presence or absence of neutralizing antibodies to the virus. Mice without a functional IFN type I system and with no mature B and T cells (AR129 mice) were unable to control infection with as little as 10 PFU of HSV-1 strain F. By contrast, in the presence of passively administered neutralizing murine antibodies to HSV-1, some AR129 mice survived infection with up to104PFU of HSV-1. This acute immune response was dependent on the presence of interleukin-12 (IL-12) p75. Interestingly, some virus-infected mice stayed healthy for several months, at which time antibody to HSV-1 was no longer detectable. Treatment of these virus-exposed mice with dexamethasone led to death in approximately 40% of the mice. HSV-1 was found in brains of mice that did not survive dexamethasone treatment, whereas HSV-1 was absent in those that survived the treatment. We conclude that in the presence of passively administered HSV-1-specific antibodies, the IL-12-induced IFN-γ-dependent innate immune response is able to control low doses of virus infection. Surprisingly, in a significant proportion of these mice, HSV-1 appears to persist in the absence of antibodies and specific immunity.
Recombinant Norwalk Virus-Like Particles Administered Intranasally to Mice Induce Systemic and Mucosal (Fecal and Vaginal) Immune Responses
Authors: Guerrero Roberto A. , Ball Judith M. , Krater Sharon S. , Pacheco Susan E. , Clements John D. , Estes Mary K. 
Published: July 2002

ABSTRACT

Recombinant Norwalk virus-like particles (rNV VLPs) were administered to BALB/c mice by the intranasal (i.n.) route to evaluate the induction of mucosal antibody responses. The results were compared to systemic and mucosal responses observed in new and previous studies (J. M. Ball, M. E. Hardy, R. L. Atmar, M. E. Connor, and M. K. Estes, J. Virol. 72:1345–1353, 1998) after oral administration of rNV VLPs. Immunizations were given in the presence or absence of a mucosal adjuvant, mutant
Escherichia coli
heat-labile toxin LT(R192G). rNV-specific immunoglobulin G (IgG) and fecal IgA were evaluated by enzyme-linked immunosorbent assay. The i.n. delivery of rNV VLPs was more effective than the oral route at inducing serum IgG and fecal IgA responses to low doses of rNV particles. Vaginal responses of female mice given VLPs by the i.n. and oral routes were also examined. All mice that received two immunizations with low doses i.n. (10 or 25 μg) of rNV VLPs and the majority of mice that received two high doses orally (200 μg) in the absence of adjuvant had rNV-specific serum IgG, fecal, and vaginal responses. Additional experiments evaluated whether rNV VLPs can function as a mucosal adjuvant by evaluating the immune responses to two soluble proteins, keyhole limpet hemocyanin and chicken egg albumin. Under the conditions tested, rNV VLPs did not enhance the serum IgG or fecal IgA response to these soluble proteins when coadministered by the i.n. or oral route. Low doses of nonreplicating rNV VLPs are immunogenic when administered i.n. in the absence of adjuvant, and addition of adjuvant enhanced the magnitude and duration of these responses. Recombinant NV VLPs represent a candidate mucosal vaccine for NV infections in humans.
Differential Expression of Interleukin-2 and Gamma Interferon in Human Immunodeficiency Virus Disease
Authors: Sieg Scott F. , Bazdar Douglas A. , Harding Clifford V. , Lederman Michael M. 
Published: July 2002

ABSTRACTSubnormal T-cell production of interleukin-2 (IL-2) in human immunodeficiency virus (HIV) disease has been described; however, it is not clear whether failure to synthesize IL-2 represents a selective or global defect in T-cell cytokine production. We evaluated the intracellular production of gamma interferon (IFN-γ) and IL-2 in CD4+cells that were stimulated with staphylococcal enterotoxin B or cytomegalovirus antigen. Strikingly, IFN-γ and IL-2 are differentially regulated in T cells of HIV-infected patients such that the numbers of CD69+cells or IFN-γ-positive cells that make IL-2 are proportionally decreased in CD4+T cells from HIV-infected patients. These findings demonstrate a selective defect in IL-2 production and suggest that enumeration of IFN-γ-producing cells in response to T-cell receptor stimulation, while providing some estimate of antigen-reactive cell frequency, may not reflect or predict “normal” T-cell function in HIV-infected patients.
Ten-Kilodalton Domain in Ty3 Gag3-Pol3p between PR and RT Is Dispensable for Ty3 Transposition
Authors: Claypool Jonathan A. , Malik Harmit S. , Eickbush Thomas H. , Sandmeyer Suzanne B. 
Published: July 2002

ABSTRACT

Ty3 is a gypsy-type, retrovirus-like element found in the budding yeast
Saccharomyces cerevisiae
. In cells overexpressing Ty3 under the
GAL1
upstream activation sequence, Ty3 RNA, proteins, and DNA are made. Elucidation of the molecular masses and amino-terminal sequences of protease and reverse transcriptase indicated the existence of an additional intervening domain, designated J, in the Ty3 Gag3-Pol3p polyprotein. A region analogous to J can be found in many retrotransposable elements closely related to Ty3; however, J does not correspond to any of the highly conserved retroviral protein domains. Ty3 mutants deleted for the J-coding region showed moderately reduced transposition frequency but greatly reduced levels of Ty3 DNA. These results show that under galactose regulation, the Ty3 J domain is not absolutely essential.
Evolution and Characterization of Tetraonine Endogenous Retrovirus: a New Virus Related to Avian Sarcoma and Leukosis Viruses
Authors: Dimcheff Derek E. , Krishnan Mallika , Mindell David P. 
Published: July 2002

ABSTRACT

In a previous study, we found avian sarcoma and leukosis virus (ASLV)
gag
genes in 19 species of birds in the order Galliformes including all grouse and ptarmigan (Tetraoninae) surveyed. Our data suggested that retroviruses had been transmitted horizontally among some host species. To further investigate these elements, we sequenced a replication-defective retrovirus, here named tetraonine endogenous retrovirus (TERV), from
Bonasa umbellus
(ruffed grouse). This is the first report of a complete, replication-defective ASLV provirus sequence from any bird other than the domestic chicken. We found a replication-defective proviral sequence consisting of putative Gag and Env proteins flanked by long terminal repeats. Reverse transcription-PCR analysis showed that retroviral
gag
sequences closely related to TERV are transcribed, supporting the hypothesis that TERV is an active endogenous retrovirus. Phylogenetic analyses suggest that TERV may have arisen via recombination between different retroviral lineages infecting birds. Southern blotting using
gag
probes showed that TERV occurs in tetraonines but not in chickens or ducks, suggesting that integration occurred after the earliest phasianid divergences but prior to the radiation of tetraonine birds.