- Volume 70, Issue 7, 1989
Volume 70, Issue 7, 1989
- Animal
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Enhancement of Virus Transmission by Tick Salivary Glands
More LessSUMMARYPrevious studies have demonstrated that Thogoto (THO) virus is transmitted from infected to uninfected ticks cofeeding on an uninfected guinea-pig, although the guinea-pig does not develop a detectable viraemia. To investigate this mode of transmission, guinea-pigs were infested with uninfected Rhipicephalus appendiculatus nymphs prior to inoculation with either a mixture of THO virus and tick salivary gland extract, or with THO virus alone. The number of ticks that acquired the virus from feeding on animals inoculated with a mixture of virus and salivary gland extract was 10-fold greater than the number that became infected by feeding on animals inoculated with virus alone. The increase in the number of ticks that became infected was greatest when the salivary glands used in the inoculum were derived from uninfected ticks, which had partially fed for a period of 6 days. Viraemia was not detected in any of the guinea-pigs tested during the experiments. These results indicate that THO virus transmission is enhanced by factor(s) associated with the salivary glands of ticks, and that these factor(s) may facilitate ‘non-viraemic’ transmission between infected and uninfected ticks.
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Studies on the Mechanism of the Interferon-mediated Antiviral State to Vesicular Stomatitis Virus in Resting Mouse Peritoneal Macrophages
More LessSUMMARYWe have analysed the expression of vesicular stomatitis virus (VSV) proteins in virus-infected freshly explanted mouse peritoneal macrophages (resistant to virus replication), macrophages aged in vitro (permissive for virus replication) and freshly explanted macrophages from mice treated with antibody to interferon (IFN) α/β (permissive for VSV replication). Our data showed that some VSV proteins (i.e. N/NS and G) were synthesized in virus-infected (1 p.f.u./cell) freshly harvested macrophages at early times after infection (3 to 6 h); the expression of such viral proteins was subsequently inhibited at 18 h post-infection. In contrast, a progressive increase in the expression of VSV proteins was observed in the macrophages aged in vitro and infected with VSV at 1 p.f.u./cell. Infection with a higher m.o.i. (16 p.f.u./cell) resulted in similar viral protein electrophoresis patterns for both aged macrophages and freshly explanted macrophages. Even at low m.o.i. a marked and progressive expression of all VSV proteins was observed in freshly harvested macrophages from mice treated with antibody to mouse IFN-.α/β Higher levels of oligo-2′,5′-adenylate synthetase (2-5AS) were found in freshly harvested macrophages than in either aged macrophages or those from mice treated with antibody to IFN. No dsRNA-dependent 67K protein kinase was detected in freshly harvested macrophages or peritoneal cells from untreated mice or mice treated with poly(rI).poly(rC) or Newcastle disease virus. The following conclusions can be drawn from these results. Low levels of spontaneous IFN–α/β are responsible for the time-dependent inhibition of VSV protein synthesis in virus-infected freshly harvested macrophages; high levels of 2–5AS (in the absence of detectable levels of 67K protein kinase) appear to correlate with the progressive inhibition of VSV proteins; this natural antiviral state is highly effective only at low m.o.i.
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Persistent Replication of Herpes Simplex Virus Type 1 in JOK-1 Cells
More LessSUMMARYInfection of the human B cell line JOK-1 with herpes simplex virus type 1 persisted over a period of more than 12 months (to date). Although limited cytopathic effects were seen, viral infection did not lead to extinction of the culture. Infectious centre assays, performed at various times after infection, revealed that only a small proportion of cells (1 to 10%) produced infectious virus particles. However, immunofluorescence studies showed that at any given time considerably more cells than calculated by infectious centre assays contained the immediate early viral protein ICP4 and expressed viral glycoproteins. These observations were confirmed by in situ hybridization analyses which revealed the presence of viral DNA even in cells not producing infectious particles. Since no evidence for the involvement of interferon could be found, some other so far unknown intrinsic property of the cells must be responsible for the restriction of virus replication and/or maturation.
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Structure and Expression of an Integrated Human Papillomavirus Type 16 Genome Amplified in a Cervical Carcinoma Cell Line
SUMMARYA cellular sequence containing the integrated human papillomavirus type 16 genome in a cervical carcinoma cell line QG-U was cloned and analysed. The transcriptionally active viral genome disrupted at the E2 and L2 open reading frames was amplified with its flanking sequences.
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Retrovirus-induced Cell Fusion Is Enhanced by Protease Treatment
More LessSUMMARYThe effect of proteases on retrovirus-induced cell fusion was studied. Both ‘fusion from within’ (fusion between infected and uninfected cells) and ‘fusion from without’ (fusion of uninfected cells by virus addition) was enhanced after treatment with proteases. An enhancement of up to 10-fold, giving 30% fusion of the cells, was observed. Protease treatment of infected cells or of virus particles enhanced fusion, indicating that cleavage of the virus surface proteins is important for cell fusion. Cell fusion is believed to reflect the virus–cell membrane fusion which occurs during the entry of enveloped viruses into cells. It is therefore possible that proteolytic cleavage of virus surface components during entry is involved in virus infection.
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Infection of Rats with Bovine Leukaemia Virus: Establishment of a Virus-producing Rat Cell Line
More LessSUMMARYAdult rats were infected with bovine leukaemia virus (BLV). Inoculated rats persistently produced antibodies directed against viral structural proteins. No major pathogenesis in infected rats was found during 2 years of observation. It was possible to recover the virus from rat spleen several months after infection. A cell line, R(BLV), was established from rat spleen; this contained integrated BLV provirus. R(BLV) cells kept for over 80 passages in vitro produced viral particles with the properties of BLV. Provirus reintegration and/or amplification occurred in R(BLV) cells. The cell line was found to be tumorigenic in rats, and the virus produced was immunogenic. R(BLV) cells represent the first described BLV-producing rat cell line. Proven persistent infection with BLV indirectly suggests that rats can serve as a reservoir of BLV in nature.
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- Plant
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Mutual Exclusion Occurs in a Chlorella-like Green Alga Inoculated with Two Viruses
More LessSUMMARYProgeny viruses resulting from dual inoculations with different and near-isogenic viruses of a Chlorella-like green alga were distinguished by immunoblotting. Plaques arising from single cells inoculated with two viruses usually contained only one of the viruses. Thus the viruses mutually exclude one another. In some combinations the ratio of viruses (as infective centres) recovered differed significantly from the input ratio.
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Fate of African Cassava Mosaic Virus Coat Protein Deletion Mutants after Agroinoculation
More LessSUMMARYWe have investigated the behaviour of coat protein deletion mutants of the geminivirus African cassava mosaic virus (ACMV) when introduced into Nicotiana benthamiana by agroinoculation. In dividing callus tissue, replicating mutant DNA A, in the absence of DNA B, remained subgenomic in size. However, systemic infection of plants was associated with the rapid reversion of the deletion mutants to native component size, as happened when the mutants were introduced into the host by more conventional mechanical inoculation procedures. The results contrast with those reported for tomato golden mosaic virus (TGMV) for which similar mutants, agroinoculated into N. benthamiana, remained subgenomic. The results indicate that the inoculation route is not responsible for the different behaviour of ACMV and TGMV mutants and illustrate a significant difference between the interaction of these otherwise closely related geminiviruses with a common host that might be exploited for the investigation of the determinants of DNA replication and spread.
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Properties and in vitro Translation of Maize Dwarf Mosaic Virus RNA
More LessSUMMARYThe RNA of maize dwarf mosaic virus strain A (MDMV-A) was characterized and compared with that of strain B (MDMV-B). Glyoxal-treated MDMV-A RNA has an M r of 3·32 × 106 measured in agarose gels, compared with that of MDMV-B which is 3·41 × 106 under the same conditions. MDMV-A RNA has a Tm of 50·7 °C and a hyperchromicity of 23·3%, which are higher than those reported for MDMV-B RNA. Translation products of both RNAs in a rabbit reticulocyte cell-free system ranged from 23K to 121K. Four major polypeptide products of 57K, 91K, 100K and 117K were produced by MDMV-A RNA-directed translation, and four major products of 39K, 55K, 86K and 121K by MDMV-B RNA. Protein profiles from the two RNAs were distinct including translation products that comigrated with authentic coat protein at 37K (MDMV-A) or 39K (MDMV-B) for each strain. Anti-virion sera immunoprecipitated polypeptide products from each strain. Distinct subsets of translation products were immunoprecipitated with antisera to tobacco etch virus 49K and 54K nuclear inclusion proteins. No cell-free translation products were recognized by antisera to potato virus Y (PVY) or tobacco vein mottling virus (TVMV) helper components or antisera to the cylindrical inclusion proteins of PVY or TVMV.
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The Nucleotide Sequence of a Soybean Mosaic Virus Coat Protein-coding Region and Its Expression in Escherichia coli, Agrobacterium tumefaciens and Tobacco Callus
More LessSUMMARYA DNA complementary to the 3′-terminal 1168 nucleotides of the genome of the N strain of soybean mosaic virus (SMV) has been cloned and sequenced. cDNA sequence and coat protein analyses indicate that the SMV coat protein-coding region is at the 3′ end of the genome, and that the coat protein is processed from a larger protein. The coat protein-coding sequence is predicted to be 795 nucleotides in length, encoding a protein of 265 amino acids with a calculated M r of 29 857. The 3′ untranslated region is 259 nucleotides in length and is followed by a polyadenylate tract. The SMV coat protein-coding region, along with a small amount of upstream sequence, has been expressed in Escherichia coli as a β-galactosidase fusion protein. The size of the protein was less than predicted for the fusion protein, suggesting processing in E. coli. The coat protein-coding region has also been expressed in Agrobacterium tumefaciens and transgenic tobacco callus as an unfused protein under the control of the cauliflower mosaic virus 35S promoter. The coat protein produced in transgenic tobacco callus had an electrophoretic mobility identical to that of SMV coat protein and constituted approximately 0·05% (w/w) of the total extracted protein.
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Partial Nucleotide Sequence of Potato Virus M RNA Shows Similarities to Potexviruses in Gene Arrangement and the Encoded Amino Acid Sequences
More LessSUMMARYThe nucleotide sequence of the 3′-proximal 2630 nucleotides of potato virus M (PVM) genomic RNA was determined. The sequenced region contained five long open reading frames (ORFs). The ORF nearest to the 3′-terminal poly(A) tail corresponds to a polypeptide of M r 10848. This ORF is preceded by one which encodes a protein of M r 33906 (34K) which has an amino acid sequence that is very similar in its carboxyterminal part to that of the coat proteins of some potexviruses. Three other ORFs encoding polypeptides of M r 24615, 11893 and 6739 are present in the region 5′ to the 34K protein gene. There is extensive similarity between these proteins and the corresponding proteins encoded by the conserved triple gene block in the RNA of potexviruses.
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Nucleotide Sequence of the 3′-Terminal Region of Clover Yellow Mosaic Virus RNA
More LessSUMMARYThe nucleotide sequence of the 3′-terminal region of clover yellow mosaic virus RNA determined from cDNA clones contains one major open reading frame (ORF) encoding a protein with an M r, of 28093 (28·1K). A smaller ORF, in frame with the major one, is also present and encodes a 23·5K protein which is similar in size to the capsid protein of the virus and has several sequence similarities with the coat proteins of four other potexviruses. The smaller ORF is probably used for the expression of the coat protein because the capsid subgenomic mRNA probably does not include the AUG of the 28·1K protein. Comparison of the amino acid sequences of the coat proteins of five potexviruses revealed a large number of identical and conservative replacements of amino acid residues.
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