-
Volume 84,
Issue 4,
2003
Volume 84, Issue 4, 2003
- Animal
-
- DNA viruses
-
-
Antibody-induced internalization of viral glycoproteins and gE–gI Fc receptor activity protect pseudorabies virus-infected monocytes from efficient complement-mediated lysis
More LessPseudorabies virus (PRV)-infected blood monocytes are able to transport virus throughout the body of vaccination-immune pigs. PRV-infected monocytes express viral glycoproteins in their plasma membrane that can be recognized by virus-specific antibodies. Recently, it has been shown that addition of PRV-specific polyclonal immunoglobulins to PRV-infected monocytes at 37 °C induces internalization of the majority of plasma membrane-expressed viral glycoproteins. This study investigated whether this process may interfere with efficient antibody-dependent complement-mediated lysis (ADCML) of infected monocytes. Therefore, an ADCML assay was set up in vitro. A significant decrease in the percentage of cells lysed by ADCML was observed when antibody-induced internalization of PRV glycoproteins occurred (P<0·005). Furthermore, it is shown (i) that the PRV gE–gI complex, which, like certain other alphaherpesvirus orthologues, possesses IgG-binding capacity, aids in avoiding efficient ADCML of PRV-infected monocytes and (ii) that the efficiency of PRV gE–gI-mediated evasion of ADCML can be decreased by the presence of gE–gI-specific antibodies.
-
-
-
Heterogeneous Epstein–Barr virus latent gene expression in AIDS-associated lymphomas and in type I Burkitt's lymphoma cell lines
More LessEpstein–Barr virus (EBV) is associated with lymphoma in immunocompromised patients. This study provides evidence that the expression of EBV nuclear antigen-3 genes can be directed from the F promoter in different type I Burkitt's lymphoma cell lines and in some lymphomas from human immunodeficiency virus-infected patients. This expression occurs predominantly after induction of the EBV lytic cycle.
-
-
-
The BZLF1 promoter of Epstein–Barr virus is controlled by E box-/HI-motif-binding factors during virus latency
More LessThe BZLF1 open reading frame of Epstein–Barr virus (EBV) encodes an important transactivator of replication. During latency, transcription of this gene is switched off. HI motifs have been shown to cause negative regulation of the promoter. Using yeast one-hybrid assays, we isolated the E box-binding protein, E2-2, interacting with these motifs. Electrophoretic mobility shift assays demonstrated that E2-2 binds to HIα, HIβ and HIγ, which contain E box consensus binding sites. Deletion of the HI-associated E boxes and overexpression of E2-2 in transfection assays revealed that these elements act as repressors in lymphoid cells. In contrast, in epithelial cells they contribute to the increased responsiveness of the promoter to transactivation by the BZLF1 protein. The data presented are in accord with an alternative and exclusive binding of different cell type- and differentiation-specific factors, such as E2-2, to the HI-associated E boxes in lymphoid and epithelial cells. This implies a role in cell type-specific virus replication.
-
-
-
A novel function for the Epstein–Barr virus transcription factor EB1/Zta: induction of transcription of the hIL-10 gene
More LessInterleukin-10 (IL-10) plays a critical role in Epstein–Barr virus (EBV) biology. Indeed, the EBV genome contains a gene (BCRF1) with homology to the human IL-10 (hIL-10) gene. In addition to viral IL-10, which is secreted late in the productive cycle, hIL-10 production is also induced in B cells infected by EBV. The EBV protein LMP-1 and the viral small non-polyadenylated RNAs (EBERs) expressed during latency are involved in hIL-10 induction. In this study, we show that in B cells the viral transcription factor EB1, which is the main inducer of the EBV productive cycle, also activates transcription of the hIL-10 gene and secretion of the hIL-10 protein. Accordingly, EB1 bound directly to specific DNA sequences in the hIL-10 minimal promoter. Moreover, specific disruption of EB1 binding to some of these sites impaired EB1-mediated activation of transcription at the hIL-10 promoter in a transient expression assay. Therefore, an increase in IL-10 production occurs during latency and early and late during the productive cycle. This production of IL-10 might favour the survival of EBV-infected cells in vivo and/or create a microenvironment required for efficient de novo infection of B lymphocytes by EBV virions.
-
- Plant
-
-
-
Double-stranded RNA-binding proteins could suppress RNA interference-mediated antiviral defences
More LessRNA interference (RNAi) is a double-stranded (ds)RNA-inducible, sequence-specific RNA-degradation mechanism that operates as a natural antiviral system in plants and animals. Successful virus infection requires evasion or suppression of RNAi. Indeed, RNAi suppressor proteins have been identified in plant and animal viruses, although the molecular mechanism of silencing inhibition is still poorly understood. Because many RNA viruses encode dsRNA-binding proteins (dsRBPs) and as RNAi is triggered by the accumulation of dsRNAs, dsRBPs were examined to see if they inhibit RNAi. Here, it is shown that heterologous dsRBPs suppressed RNAi in plants, indicating that in natural host–virus interactions, pathogen-encoded dsRBPs could inactivate RNAi-mediated host defences.
-
-
-
-
Assembly of single-shelled cores and double-shelled virus-like particles after baculovirus expression of major structural proteins P3, P7 and P8 of Rice dwarf virus
More LessExpression of the core capsid protein P3 of Rice dwarf virus in a baculovirus system resulted in the formation of single-shelled core-like particles in insect cells in the absence of any other capsid proteins. Double-shelled virus-like particles were also observed upon mixing or co-expression of P3 and the major outer capsid protein P8, suggesting that P3 and P8 have the ability to form double-shelled particles both in vivo and in vitro. Core protein P7 expressed in a similar manner was incorporated into the virus-like particles.
-
-
-
Immunodetection and fluorescent microscopy of transgenically expressed hordeivirus TGBp3 movement protein reveals its association with endoplasmic reticulum elements in close proximity to plasmodesmata
The subcellular localization of the hydrophobic TGBp3 protein of Poa semilatent virus (PSLV, genus Hordeivirus) was studied in transgenic plants using fluorescent microscopy to detect green fluorescent protein (GFP)-tagged protein and immunodetection with monoclonal antibodies (mAbs) raised against the GFP-based fusion expressed in E. coli. In Western blot analysis, mAbs efficiently recognized the wild-type and GFP-fused PSLV TGBp3 proteins expressed in transgenic Nicotiana benthamiana, but failed to detect TGBp3 in hordeivirus-infected plants. It was found that PSLV TGBp3 and GFP–TGBp3 had a tendency to form large protein complexes of an unknown nature. Fractionation studies revealed that TGBp3 represented an integral membrane protein and probably co-localized with an endoplasmic reticulum-derived domain. Microscopy of epidermal cells in transgenic plants demonstrated that GFP–TGBp3 localized to cell wall-associated punctate bodies, which often formed pairs of opposing discrete structures that co-localized with callose, indicating their association with the plasmodesmata-enriched cell wall fields. After mannitol-induced plasmolysis of the leaf epidermal cells in the transgenic plants, TGBp3 appeared within the cytoplasm and not at cell walls. Although TGBp3-induced bodies were normally static, most of them became motile after plasmolysis and displayed stochastic motion in the cytoplasm.
-
-
-
The optimal temperature for RNA replication in cells infected by Soil-borne wheat mosaic virus is 17 °C
More LessSystemic infection of wheat plants with Soil-borne wheat mosaic virus (SBWMV) requires temperatures below 20 °C. Here we examine the cause of the temperature sensitivity by inoculating infectious in vitro transcripts of SBWMV RNA1 and RNA2 to barley mesophyll protoplasts. After RNA inoculation, protoplasts were incubated at temperatures between 15 and 25 °C for up to 48 h. Western blot analysis showed that the capsid protein accumulated most abundantly at 17 °C but was not detectable at 25 °C. Northern blot analysis showed that the wild-type RNA1 and RNA2 and their subgenomic RNAs accumulated most abundantly at 17 °C but were barely detectable at 25 °C. An RNA1 mutant in which the p152 and p211 replicase genes were placed between the 5′- and 3′-untranslated regions also replicated most efficiently at 17 °C but not at 25 °C. Thus, the requirement for temperatures lower than 20 °C for SBWMV infection is primarily determined by replication of RNA1, which encodes the viral RNA replicase.
-
-
-
Potato mop-top virus: the coat protein-encoding RNA and the gene for cysteine-rich protein are dispensable for systemic virus movement in Nicotiana benthamiana
Full-length genomic cDNA clones of the Swedish isolate of Potato mop-top virus (PMTV) were transcribed in vitro using T7 RNA polymerase. The combination of RNA 1, 2 and 3 synthesized in the presence of m7GpppG cap analogue was infectious when inoculated onto Nicotiana benthamiana plants. Also, the combination of RNA 1 (encodes the viral replicase) with RNA 3 [encodes the triple gene block proteins and a small cysteine-rich protein (CRP)] was infectious and both RNAs moved systemically in N. benthamiana plants in the absence of RNA 2, which encodes the coat protein (CP). However, the yellow mosaic symptoms that typically developed following PMTV infection with all three RNAs were not observed in plants infected with RNA 1+RNA 3. Site-directed mutagenesis experiments revealed that expression of the putative CRP was not required for systemic infection and symptom induction in N. benthamiana. These data show that PMTV represents an example of a multipartite virus capable of establishing systemic infection without the CP-encoding RNA, and also without the putative CRP.
-
-
-
Nucleotide sequence and genome organization of Cucumber yellows virus, a member of the genus Crinivirus
More LessThe genome of Cucumber yellows virus (CuYV), isolated in Japan from cucumber (Cucumis sativus L.), was completely sequenced and shown to be bipartite. CuYV RNA1 consisted of 7889 nucleotides and encompassed seven open reading frames (ORFs), which is typical of the Closteroviridae, including a heat-shock protein 70 homologue, a coat protein and a diverged coat protein (CPd). CuYV RNA2 consisted of 7607 nucleotides and included two ORFs: ORF1a potentially encoded a polyprotein containing putative papain-like protease, methyltransferase and helicase domains, and ORF 1b potentially encoded an RNA-dependent RNA polymerase, which is probably expressed via a +1 ribosomal frameshift. The size and organization of the CuYV genome are similar to those of Lettuce infectious yellows virus (LIYV), the type member of the genus Crinivirus in the family Closteroviridae, indicating that CuYV is a member of that genus, although CuYV differed in several points from LIYV.
-
- Other Agents
-
-
-
In vitro cell-free conversion of bacterial recombinant PrP to PrPres as a model for conversion
More LessPrion diseases are associated with the conversion of the normal cellular prion protein, PrPC, to the abnormal disease-associated protein, PrPSc. This conversion can be mimicked in vitro using PrPSc isolated from the brains of scrapie-infected animals to induce conversion of recombinant PrPC into a proteinase K-resistant isoform, PrPres. Traditionally, the ‘cell-free’ conversion assay has used, as substrate, recombinant PrPC purified from mammalian tissue culture cells or, more recently, from baculovirus-infected insect cells. The cell-free conversion assay has been modified by replacing the tissue culture-derived PrPC with recombinant PrP purified from bacteria. Bacterial expression and chromatographic purification give high yields of recombinant radiolabelled untagged protein, eliminates artefacts that may be due to cellular factors or antibody fragments normally present in labelled PrP preparations and allows accurate and rapid variation of protein sequence using standard molecular biological techniques. In addition, these cell-free conversion assays were carried out under more physiological conditions, giving more relevance to the assay as a model for conversion. To validate its use in this assay, this bacterial recombinant PrP has been shown to have the conversion properties of mammalian PrPC: (i) it converts to a proteinase K-resistant isoform in the presence of PrPSc; (ii) the efficiency of this conversion by PrPSc of different strains and species parallels that found in vivo; and (iii) its cell-free conversion is inhibited by Congo Red analogues in a structure-dependent manner similar to that seen in in vivo and in vitro cell assays.
-
-
-
-
Studies of the transmissibility of the agent of bovine spongiform encephalopathy to pigs
Studies to test the transmissibility of the bovine spongiform encephalopathy (BSE) agent to pigs began in 1989. Parenteral inoculation of the agent by three routes simultaneously (intracranially, intravenously and intraperitoneally) produced disease with an incubation period range of 69–150 weeks. Pre-clinical pathological changes were detected in two pigs killed electively at 105 and 106 weeks post-inoculation. Infectivity was detected by bioassay in inbred mice in the CNS of those pigs that developed spongiform encephalopathy. Infectivity was also found in the stomach, jejunum, distal ileum and pancreas of terminally affected pigs. These findings show that pigs are susceptible to BSE. In contrast, disease failed to occur in pigs retained for 7 years after exposure by feeding BSE-affected brain on three separate days, at 1–2 week intervals. The amounts fed each day were equivalent to the maximum daily intake of meat and bone meal in rations for pigs aged 8 weeks. No infectivity was found in tissues assayed from the pigs exposed orally. This included tissues of the alimentary tract. It is suggested that these pigs did not become infected. The relatively high oral exposure used in these experiments compared with feed-borne exposure in the field may explain the absence of an epidemic of spongiform encephalopathy in domestic pigs concurrent with the BSE epidemic in the UK.
-
-
-
Cell-associated variants of disease-specific prion protein immunolabelling are found in different sources of sheep transmissible spongiform encephalopathy
More LessScrapie and bovine spongiform encephalopathy (BSE) are transmissible spongiform encephalopathies (TSEs) or prion diseases affecting domestic and exotic ruminants. In previous immunohistochemical studies, we have shown that different sheep TSE sources may be distinguished by both the proportion of disease-specific prion protein (PrPd) accumulation relative to different cell types in the brain (the ‘PrPd profile’) and by different labelling patterns for PrP peptide sequences within phagocytic cells. In the present study, we have further characterized the intracellular accumulation patterns of PrPd in the lymphoreticular system (LRS) and in the brain of sheep clinically affected with scrapie or BSE. BSE-infected PrPARQ/ARQ sheep of different breeds were compared with scrapie-infected sheep of different PrP genotypes. Cases of BSE infection could be distinguished from scrapie cases by a marked reduction in labelling of PrPd containing the 84–105 amino acid residues in phagocytic cells of the LRS and in neurones and glia of the brain. These results therefore indicate that TSE agent-dependent processing of PrP in specific cell types within the brain and LRS can be used to distinguish between BSE in PrPARQ/ARQ sheep and scrapie in sheep of several PrP genotypes. Three different N-terminal peptide antibody labelling patterns were recognized for different cell types in different tissues of BSE-infected sheep, suggesting that different truncated forms of PrPd are formed following infections with this agent strain. These variations in the cleavage sites of BSE PrPd may be due to cell-specific variation in endosomal–lysosomal digestion or to cell- and tissue-specific differences in BSE PrPd conformation.
-
-
-
Molecular analysis of iatrogenic scrapie in Italy
An accidental intra- and interspecies transmission of scrapie occurred in Italy in 1997 and 1998 following exposure to a vaccine against Mycoplasma agalactiae. PrPSc in affected sheep and goats, collected from a single flock exposed to vaccination 2 years earlier, was molecularly typed. In five animals with iatrogenic scrapie, a PrPSc type with a 20 kDa core fragment was found in all areas of the brain investigated. In three sheep and one goat, this isoform co-occurred with a fully glycosylated isoform that had a protease-resistant backbone of 17 kDa, whereas in two sheep and four goats, the two PrPSc types were detected in different regions of the brain. In sheep with natural field scrapie, a PrPSc type with physico-chemical properties indistinguishable from the 20 kDa isoform was found. The present results suggest the co-presence of two prion strains in mammary gland and brain homogenates used for vaccination.
-
Volumes and issues
-
Volume 106 (2025)
-
Volume 105 (2024)
-
Volume 104 (2023)
-
Volume 103 (2022)
-
Volume 102 (2021)
-
Volume 101 (2020)
-
Volume 100 (2019)
-
Volume 99 (2018)
-
Volume 98 (2017)
-
Volume 97 (2016)
-
Volume 96 (2015)
-
Volume 95 (2014)
-
Volume 94 (2013)
-
Volume 93 (2012)
-
Volume 92 (2011)
-
Volume 91 (2010)
-
Volume 90 (2009)
-
Volume 89 (2008)
-
Volume 88 (2007)
-
Volume 87 (2006)
-
Volume 86 (2005)
-
Volume 85 (2004)
-
Volume 84 (2003)
-
Volume 83 (2002)
-
Volume 82 (2001)
-
Volume 81 (2000)
-
Volume 80 (1999)
-
Volume 79 (1998)
-
Volume 78 (1997)
-
Volume 77 (1996)
-
Volume 76 (1995)
-
Volume 75 (1994)
-
Volume 74 (1993)
-
Volume 73 (1992)
-
Volume 72 (1991)
-
Volume 71 (1990)
-
Volume 70 (1989)
-
Volume 69 (1988)
-
Volume 68 (1987)
-
Volume 67 (1986)
-
Volume 66 (1985)
-
Volume 65 (1984)
-
Volume 64 (1983)
-
Volume 63 (1982)
-
Volume 62 (1982)
-
Volume 61 (1982)
-
Volume 60 (1982)
-
Volume 59 (1982)
-
Volume 58 (1982)
-
Volume 57 (1981)
-
Volume 56 (1981)
-
Volume 55 (1981)
-
Volume 54 (1981)
-
Volume 53 (1981)
-
Volume 52 (1981)
-
Volume 51 (1980)
-
Volume 50 (1980)
-
Volume 49 (1980)
-
Volume 48 (1980)
-
Volume 47 (1980)
-
Volume 46 (1980)
-
Volume 45 (1979)
-
Volume 44 (1979)
-
Volume 43 (1979)
-
Volume 42 (1979)
-
Volume 41 (1978)
-
Volume 40 (1978)
-
Volume 39 (1978)
-
Volume 38 (1978)
-
Volume 37 (1977)
-
Volume 36 (1977)
-
Volume 35 (1977)
-
Volume 34 (1977)
-
Volume 33 (1976)
-
Volume 32 (1976)
-
Volume 31 (1976)
-
Volume 30 (1976)
-
Volume 29 (1975)
-
Volume 28 (1975)
-
Volume 27 (1975)
-
Volume 26 (1975)
-
Volume 25 (1974)
-
Volume 24 (1974)
-
Volume 23 (1974)
-
Volume 22 (1974)
-
Volume 21 (1973)
-
Volume 20 (1973)
-
Volume 19 (1973)
-
Volume 18 (1973)
-
Volume 17 (1972)
-
Volume 16 (1972)
-
Volume 15 (1972)
-
Volume 14 (1972)
-
Volume 13 (1971)
-
Volume 12 (1971)
-
Volume 11 (1971)
-
Volume 10 (1971)
-
Volume 9 (1970)
-
Volume 8 (1970)
-
Volume 7 (1970)
-
Volume 6 (1970)
-
Volume 5 (1969)
-
Volume 4 (1969)
-
Volume 3 (1968)
-
Volume 2 (1968)
-
Volume 1 (1967)
Most Read This Month
