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At least 1,063 records · Page 59Linked to original sources
PubMed1991

Cowpea mosaic virus middle component RNA contains a sequence that allows internal binding of ribosomes and that requires eukaryotic initiation factor 4F for optimal translation.

Cowpea mosaic virus (CPMV) middle component RNA (M-RNA) encodes two proteins of 105 and 95 kDa, of which translation starts at nucleotide (nt) 161 and nt 512, respectively. In vitro translation of both proteins directed by T7 transcripts of M-RNA was stimulated fourfold by eukaryotic initiation factor 4F (eIF-4F), the cap-binding protein complex. The ratio of the synthesis of both proteins after translation was not influenced by eIF-4F or by any known eIF. Part of the CPMV 5' sequence was cloned downstream of the 5' untranslated region of ornithine decarboxylase (ODC); the latter untranslated sequence has a highly stable secondary structure, preventing efficient translation of ODC. Insertion of nt 161 to 512 of CPMV M-RNA upstream of the ODC initiation codon resulted in a marked increase in ODC translation, which indicates that the CPMV sequence contains an internal ribosome-binding site. The insertion conferred stimulation by eIF-4F on ODC translation, showing that eIF-4F is able to stimulate internal initiation.

Base Sequence↗
PubMed1993

Proteolytic enhancement of human rotavirus infectivity.

Rotaviruses are the most important etiologic agents of severe diarrhea worldwide. Despite great advances in vaccine development, little is known about host protection mechanisms other than immunity. This presentation focuses on the proteolytic enhancement of rotavirus infection, with emphasis on the functions of VP4, an outer capsid protein. The in vitro growth of human rotavirus is enhanced by trypsin, which selectively cleaves VP4. Treatment with trypsin increases the infectivity of human rotavirus while decreasing its hemagglutination activity. There are two modes of rotavirus internalization: direct penetration with the aid of trypsin and endocytosis without trypsin. Direct penetration via VP4 cleaved by trypsin is essential for the replication of the virus, whereas endocytotic internalization does not give rise to viral replication.

Animals↗
PubMed1994

Concanamycin A: a powerful inhibitor of enveloped animal-virus entry into cells.

Concanamycin A, a selective inhibitor of the vacuolar proton ATPase, blocks the infection of animal cells by vesicular stomatitis virus, Semliki Forest virus and influenza virus even when the drug is present at the low concentration of 5 nM. Nevertheless the antibiotic prevents neither the attachment, to cells, of Semliki Forest virus nor its subsequent internalization. Under certain conditions, described in this communication, virus entry is prevented even when the pH of the medium is low, thus suggesting that a pH gradient, rather than low pH per se, is required to drive the entry, into cells, of these enveloped animal viruses.

Animals↗
PubMed2000

Avian-to-human transmission of H9N2 subtype influenza A viruses: relationship between H9N2 and H5N1 human isolates.

In 1997, 18 cases of influenza in Hong Kong (bird flu) caused by a novel H5N1 (chicken) virus resulted in the deaths of six individuals and once again raised the specter of a potentially devastating influenza pandemic. Slaughter of the poultry in the live bird markets removed the source of infection and no further human cases of H5N1 infection have occurred. In March 1999, however, a new pandemic threat appeared when influenza A H9N2 viruses infected two children in Hong Kong. These two virus isolates are similar to an H9N2 virus isolated from a quail in Hong Kong in late 1997. Although differing in their surface hemagglutinin and neuraminidase components, a notable feature of these H9N2 viruses is that the six genes encoding the internal components of the virus are similar to those of the 1997 H5N1 human and avian isolates. This common feature emphasizes the apparent propensity of avian viruses with this genetic complement to infect humans and highlights the potential for the emergence of a novel human pathogen.

Animals↗
PubMed1991

Safety and immunogenicity of live attenuated cold-adapted influenza B/Ann Arbor/1/86 reassortant virus vaccine in infants and children.

A cold-adapted (ca) influenza B reassortant vaccine consisting of two genes encoding the hemagglutinin and neuraminidase from wild-type influenza B/Ann Arbor/1/86 virus and the six internal RNA segments from influenza B/Ann Arbor/1/66 ca virus was evaluated in 18 seropositive and 57 seronegative infants and children. The ca reassortant was infectious in seronegative vaccinees, with an estimated 50% human infectious dose of 10(2.5) TCID50. Nasal wash specimens from vaccinees retained the temperature-sensitive phenotype, indicating that the virus was phenotypically stable after replication in fully susceptible children. The vaccine was highly immunogenic in the seronegative vaccinees; 54% of the seropositive vaccinees also developed an increase in serum antibody. The ca vaccine was well tolerated, with only a mild increase in upper respiratory tract symptoms seen in the seronegative vaccinees. These studies indicate that the B/Ann Arbor/1/86 ca reassortant is safe, immunogenic, and phenotypically stable in infants and children.

Antibodies, Viral↗
PubMed1997

Effect of adenovirus 2 on cellular gene activation in blood-derived monocytes and macrophages.

We have investigated the effect of adenovirus 2 (Ad2) infection on human monocytes and monocyte-derived macrophages with regard to expression of TNF-alpha and IL-1 beta. In monocytes, the virus was bound to the surface without being internalized. On the other hand, Ad2 was internalized by macrophages. No virus replication and no transcription of the Ad2 early genes was observed in either of the cells. Ad2 infection induced transient increase in the mRNA levels for TNF-alpha and IL-1 beta in both monocytes and in macrophages, although the kinetics of the transcription was slightly different. The production of both cytokines, measured by ELISA tests, was enhanced in monocytes. In macrophages, a slight enhancement of TNF-alpha production was seen, whereas IL-1 beta was not detected. The data indicate that cellular genes might be activated by Ad2 virus infection in nonpermissive cells where no viral gene products could be detected.

Adenoviridae↗
PubMed1981

Characterization of the temperature sensitive phenotype of the A/Ann Arbor/6/60 cold-adapted virus and its recombinants.

The A/Ann Arbor/6/60 cold-adapted (ca) donor virus had a 38 degrees C shutoff temperature when tested in MDCK tissue culture. ca recombinant viruses bearing all six "internal genes" of the A/Ann Arbor/6/60 ca donor virus and the surface antigens of wild-type virus can manifest a 1,000-fold difference in plaquing efficiency at 38 degrees C. These observations suggest that the A/Ann Arbor/6/60 ca donor genes that specify the temperature sensitive phenotype of the ca recombinants can undergo genetic modification during the production and passage of the recombinants. The NS gene in the ca recombinant virus could be inherited from either parent without influencing the level of temperature sensitivity of the ca recombinant.

Animals↗
PubMed1987

Role of receptor-binding activity of the viral hemagglutinin molecule in the presentation of influenza virus antigens to helper T cells.

The concentration of antigen required to stimulate influenza virus-specific helper T cells was observed to be dependent upon the antigenic form bearing the relevant determinant: intact, nonreplicative virus was needed only in picomolar amounts, while denatured proteins, protein fragments, or synthetic peptides were required in micromolar concentrations for a threshold level of stimulation. Antigenic efficiency of intact virus was found to result from the attachment of virus to sialic acid residues on the surface of the antigen-presenting cell since spikeless viral particles lacking the hemagglutinin molecule were much less efficient antigens for helper T cells and continuous presence of hemagglutination-inhibiting antihemagglutinin antibodies reduced efficiency of stimulation by intact virus approximately 100-fold for both hemagglutinin and internal virion proteins. Influenza virus associated rapidly with antigen-presenting cells; less than 10 min at 20 degrees C was sufficient to introduce virus for a maximal level of T-cell stimulation. This rapid attachment was blocked by antibodies to the hemagglutinin or by pretreatment of the antigen-presenting cells with neuraminidase to remove the cellular virus receptor. Following viral adsorption by antigen-presenting cells, a lag period of 30 min at 37 degrees C was required for the expression of helper T-cell determinants. One early event identified was the movement of the virus to a neuraminidase-insensitive compartment, which can occur at 10 degrees C, but which was not equivalent to expression of helper T-cell determinants. Preincubation of cells with virus at 10 degrees C for 4 h reduced the lag period of helper T-cell determinant expression to 15 min when these cells were shifted to 37 degrees C, suggesting that transition of the virus to a neuraminidase-resistant state is a required step in presentation of T-cell antigenic determinants.

Animals↗
PubMed1997

Epstein-Barr virus-associated Hodgkin's disease: epidemiologic characteristics in international data.

Hodgkin's disease (HD) has long been suspected to have an infectious precursor, and indirect evidence has implicated Epstein-Barr virus (EBV), a ubiquitous herpesvirus, as a causal agent. Recent molecular studies using EBER in situ hybridization or latency membrane protein-I (LMP-I) immunohistochemistry have identified EBV latent infection in up to 50% of HD tumors. However, the epidemiologic features of these cases have not been examined in detail. To explore the epidemiology of EBV-positive HD so as to understand the role of EBV in HD etiology more clearly, this project accumulated patient data from 14 studies that had applied these EBV assays to HD tumors. With information on age at diagnosis, sex, ethnicity, histologic subtype, country of residence, clinical stage and EBV tumor status from 1,546 HD patients, we examined risk for EBV-positive disease using logistic regression. Forty percent of subjects had EBV-positive tumors, and EBV prevalence varied significantly across groups defined by the study variables. Odds ratios (OR) for EBV-associated HD were significantly elevated for Hispanics vs. whites (OR = 4.1), mixed cellularity vs. nodular sclerosis histologic subtypes (OR = 7.3, 13.4, 4.9 for ages 0-14, 15-49, 50+ years), children from economically less-developed vs. more-developed regions and young adult males vs. females (OR = 2.5). These findings suggest that age, sex, ethnicity and the physiologic effects of poverty may represent biologic modifiers of the EBV association and confirm that this association is strongly but variably linked to histologic subtype. The data augment biologic evidence that EBV is actively involved in HD pathogenesis in some cases but describe epidemiologic complexity in this process.

Adolescent↗
PubMed2001

Herpes simplex virus type 2 UL34 protein requires UL31 protein for its relocation to the internal nuclear membrane in transfected cells.

Herpes simplex virus type 2 UL34 protein is expressed late in infection and is required for envelopment of nucleocapsids at the nuclear membrane and possibly at the endoplasmic reticulum (ER). It is a type II membrane protein with a C-terminal anchor that localizes mainly to the nuclear membrane in infected cells. However, in single transient expression, UL34 protein localizes predominantly to the ER. Relocation of UL34 protein from the ER to the internal nuclear membrane and the nucleus was observed in the presence of UL31 protein, a phosphoprotein known to interact physically with UL34. It is suggested here that interaction with UL31 protein is important for the nuclear targetting of UL34 protein and also that the trans-membrane region of UL34 protein is responsible for its localization at the internal nuclear membrane. The results also suggest possible sites for the interaction.

Active Transport, Cell Nucleus↗
PubMed1995

Interaction between the 5'-terminal cloverleaf and 3AB/3CDpro of poliovirus is essential for RNA replication.

On the basis of sequence alignments and secondary structure comparisons of the first 100 nucleotides of enterovirus and rhinovirus RNAs, chimeric constructs in which this region of poliovirus type 1 Mahoney [PV1(M)] is replaced with that of human rhinovirus type 2 (HRV2) or HRV14 have been engineered. These chimeric constructs contain the internal ribosomal entry site of either poliovirus or encephalomyocarditis virus. Independent of the internal ribosomal entry site elements, only the constructs containing either the PV1(M) or HRV2 cloverleaf sequences yielded viable viruses. The secondary structures of all three cloverleaves are quite similar. However, highly purified polioviral proteins 3CDpro and 3AB together bound to the PV1(M) and HRV2 cloverleaves, albeit with different affinities, whereas the HRV14 homolog did not interact with these proteins to any appreciable extent. These results support a mechanism of poliovirus genomic replication in which the formation of a complex between the cloverleaf structure and the 3CDpro/3AB proteins of poliovirus plays an essential role.

3C Viral Proteases↗
PubMed1990

A cellular 57 kDa protein binds to two regions of the internal translation initiation site of foot-and-mouth disease virus.

A ribosome-associated 57 kDa protein from rabbit reticulocytes was linked to the internal translation initiation site of foot-and-mouth disease virus by mild UV-irradiation. Binding studies with different RNA fragments revealed that this protein interacts with two distinct sites within the translational control region. One site is located approximately 400 nucleotides upstream from the translational start codon and the second binding site could be confined to 60 nucleotides preceding this codon. Both sequences coincide with hairpin structures at the two opposite ends of a secondary structure model of the internal ribosomal entry site proposed by Pilipenko et al. [(1989) Nucleic Acids Res. 17, 5701-5711].

Animals↗
PubMed1996

Use of cis- and trans-acting viral regulatory sequences to improve expression of human immunodeficiency virus vectors in human lymphocytes.

We compared the efficiency of human immunodeficiency virus (HIV-1) vectors that express a marker gene (chloramphenicol acetyltransferase, CAT) using different promoter elements. In one vector, CAT was expressed under the control of an internal murine leukemia virus (MuLV) long terminal repeat (LTR). In other vectors, CAT production was regulated by the HIV-1 LTR; these vectors also contained the HIV-1 tat gene and pol sequences reported to exert cis-acting positive effects on reverse transcription or gene expression. Vectors employing the Tat-driven HIV-1 LTR exhibited up to 500-fold greater CAT expression in Jurkat lymphocytes or human peripheral blood mononuclear cells compared with vectors using the internal MuLV LTR element as a promoter. This difference was not due to improved packaging of the vector RNA into virions, but to an improved level of gene expression in the target cells. Target cell CAT expression was two- to threefold higher for the vector containing the pol sequences and was only slightly less than that seen for a trans-complemented envdeleted provirus. These results indicate that defective HIV-1 vectors with efficiencies of gene transfer and expression comparable with that of HIV-1 itself are feasible.

Cells, Cultured↗
PubMed2004

Foamy viruses--a world apart.

Foamy viruses (FVs) or spumaviruses were described for the first time in the early 1950s in cell cultures derived from monkey kidneys. Later, FVs were isolated in several mammal species such as cats, cattle and horses. Highly prevalent in non-human primates they are not naturally present in humans, although several cases of simian-to-human transmissions have been described. Interestingly, the replication strategy of FVs differs in many aspects from that of other retroviruses, presenting features that are closely related to pararetroviruses, exemplified by the hepatitis B virus (HBV), but also characteristics that are closely related to yeast retrotransposons. These characteristics led to the creation of a distinct viral subfamily by the International Committee on Virus Taxonomy in 2002; the Spumaretrovirinae.

Animals↗
PubMed2004

From lethal virus to life-saving vaccine: developing inactivated vaccines for pandemic influenza.

Over the past eight years, cases of human infection with highly pathogenic avian influenza viruses have raised international concern that we could be on the brink of a global influenza pandemic. Many of these human infections have proved fatal and if the viruses had been able to transmit efficiently from person to person, the effects would have been devastating. How can we arm ourselves against this pandemic threat when these viruses are too dangerous to use in conventional vaccine production? Recent technological developments (reverse genetics) have allowed us to manipulate the influenza virus genome so that we can construct safe, high-yielding vaccine strains. However, the transition of reverse-genetic technologies from the research laboratory to the manufacturing environment has presented new challenges for vaccine manufacturers as well as veterinary and public health authorities.

Disease Outbreaks↗
PubMed2000

Glycoprotein D or J delivered in trans blocks apoptosis in SK-N-SH cells induced by a herpes simplex virus 1 mutant lacking intact genes expressing both glycoproteins.

We have made two stocks of a herpes simplex virus 1 mutant lacking intact U(S)5 and U(S)6 open reading frames encoding glycoproteins J (gJ) and D (gD), respectively. The stock designated gD(-/+), made in cells carrying U(S)6 and expressing gD, was capable of productively infecting cells, whereas the stock designated gD(-/-), made in cells lacking viral DNA sequences, was known to attach but not initiate infection. We report the following. (i) Both stocks of virus induced apoptosis in SK-N-SH cells. Thus, annexin V binding to cell surfaces was detected as early as 8 h after infection. (ii) U(S)5 or U(S)6 cloned into the baculovirus under the human cytomegalovirus immediate-early promoter was expressed in SK-N-SH cells and blocked apoptosis in cells infected with either gD(-/+) or gD(-/-) virus, whereas glycoprotein B, infected cell protein 22, or the wild-type baculovirus did not block apoptosis. (iii) In SK-N-SH cells, internalized, partially degraded virus particles were detected at 30 min after exposure to gD(-/-) virus but not at later intervals. (iv) Concurrent infection of cells with baculoviruses did not alter the failure of gD(-/-) virus from expressing its genes or, conversely, the expression of viral genes by gD(-/+) virus. These results underscore the capacity of herpes simplex virus to initiate the apoptotic cascade in the absence of de novo protein synthesis and indicate that both gD and gJ independently, and most likely at different stages in the reproductive cycle, play a key role in blocking the apoptotic cascade leading to cell death.

Animals↗