- Volume 71, Issue 10, 1990
Volume 71, Issue 10, 1990
- Animal
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Production of a non-functional nef protein in human immunodeficiency virus type 1-infected CEM cells
The nef gene product of the human immunodeficiency virus (HIV) is suggested to be a negative factor involved in down-regulating viral expression by a mechanism in which the correct conformation of the nef protein is essential. The nef protein expressed by vaccinia virus recombinants is phosphorylated by protein kinase C. We investigated the synthesis of the nef protein and its state of phosphorylation during HIV-1 infection of a T4 cell line (CEM cells). Maximum synthesis of viral proteins occurred 3 days after infection, when more than 90% of cells were producing viral proteins. The synthesis of the nefprotein was detected in parallel with the env and gag proteins. As expected, the nef protein was myristylated but not phosphorylated, and its half-life was less than 1 h. By the use of the polymerase chain reaction technique, we isolated and sequenced the nef gene of this HIV-1 stock. Two significant mutations were observed. Firstly, threonine, at amino acid number 15, the site of phosphorylation by protein kinase C, was mutated into an alanine, and secondly aspartic acid of the tetrapeptide WRFD, which is probably involved in GTP binding, was mutated into an asparagine. The mutated nef gene was expressed in a vaccinia virus system, in which it was not phosphorylated and its half-life was dramatically reduced compared to the wild-type nef gene product. Furthermore, down- regulation of CD4 cell surface expression was no longer affected by the mutated nef gene. These results emphasize that phosphorylation of the nef protein provides an efficient test to monitor its biological activity.
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Inhibition of the uncoating of bovine enterovirus by short chain fatty acids
More LessShort chain fatty acids inhibit the replication of bovine enterovirus but are almost ineffective against poliovirus type 1, coxsackievirus B5, encephalomyocarditis virus and human rhinovirus 1B. Lauric acid binds to bovine enterovirus, thereby stabilizing the virus particle to heat degradation. Fatty acid-bound virions attach to susceptible cells but fail to undergo cell-mediated uncoating. The inhibitory effect is reversible with chloroform and may result from a hydrophobic interaction between the fatty acid and a specific site on the virus particle.
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The complete nucleotide sequence of enterovirus type 70: relationships with other members of the Picornaviridae
Enterovirus type 70 (EV70) is the causative agent of acute haemorrhagic conjunctivitis and may also give rise to a rare neurological complication closely resembling poliomyelitis. The complete nucleotide sequence of the genome of EV70 has been determined from cDNA cloned in Escherichia coli. The genome consists of a 5′ non-coding region of 726 nucleotides (nt), a long open reading frame of 6582 nt and a 3′ non-coding region of 82 nt prior to the poly(A) tract. Comparison of the nucleotide sequence and the predicted amino acid sequence of the polyprotein with those published for other enteroviruses reveals sufficiently high similarity to predict antigenic regions and polyprotein cleavage sites. The P1 region of EV70 is as similar to those of the entero- as to those of the rhinoviruses, whereas the P2 and P3 regions are more closely related to the coxsackie B and swine vesicular disease viruses than other entero- or rhinoviruses.
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Attenuation of wild-type yellow fever virus by passage in HeLa cells
During the 1960s three different research groups reported that passage of wild-type yellow fever (YF) virus [strain Asibi (YF-Asibi)] in HeLa cells resulted in attenuation of the virus for monkeys so that the virus no longer caused viscerotropic disease. We have repeated and extended this observation to analyse the process of attenuation of YF virus during cell culture passage. A large plaque (LP) variant of YF-Asibi virus became attenuated for both monkeys and mice following six serial subcultures in HeLa cells (YF-Asibi-LP HeLa p6). Thus, attenuation was probably due to a genetic change in the virus population rather than to selective enrichment of a pre-existing variant of YF-Asibi-LP virus. No evidence was obtained to implicate defective interfering particles in the attenuation process. Comparison of the YF-Asibi-LP viruses before and after passage in HeLa cells, using a panel of envelope protein-reactive monoclonal antibodies (MAbs), showed that MAbs which specifically neutralize YF-Asibi-LP virus, and not YF 17D-204 vaccine virus, also neutralized YF-Asibi-LP HeLa p6. This indicated that the epitopes involved in the biological process of neutralization were not altered during attenuation. However, two MAbs that recognize envelope protein epitopes did distinguish between HeLa- and non-HeLa-passaged YF-Asibi-LP virus. One of these (MAb 117) which is YF wild-type-specific, recognized YF-Asibi-LP virus but not YF-Asibi-LP HeLa p6 virus, whereas the other (MAb 411), which is YF vaccine-specific, recognized YF-Asibi-LP HeLa p6 virus but not YF-Asibi-LP virus. These results suggest that antigenic changes in the viral envelope protein may determine the relative virulence or attenuation of YF virus.
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Generation and transmission of Rift Valley fever viral reassortants by the mosquito Culex pipiens
More LessReassortant viruses containing heterologous S and M genomic RNA segments were obtained from both mosquito and vertebrate hosts that had been co-infected with Egyptian and Senegalese strains of Rift Valley fever (RVF) virus. The origin of the S and M RNA segments in each plaque-cloned virus was determined with monoclonal antibodies capable of differentiating the nucleocapsid protein (S segment marker) or the G1 glycoprotein (M segment marker) of the parental strains. In the mosquito Culex pipiens, reassortants were detected after sequential ingestion of parental viruses by interrupted feeding on two infected hamster hosts, after feeding on a single host that had been infected with both parental strains, and from individual mosquitoes inoculated intrathoracically with both parental strains. Reassortant viruses replicated efficiently in mosquitoes and were readily transmissible by bite to hamsters. Replication of a second infecting strain of RVF virus was, however, completely inhibited if that virus was inoculated into a mosquito ⩾48 h after the first viral strain. Genetic reassortment may provide a mechanism for increased heterogeneity, and thus affect the epidemiology and evolution of RVF virus.
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Morphological studies of the neutralization of influenza virus by IgM
More LessQuantitative relationships between neutralization, aggregation and attachment to monolayers of chick embryo fibroblast (CEF) cells have been studied using a constant amount of influenza A/fowl plague virus/Rostock/34 (H7N1) and varying amounts of purified mouse polyclonal IgM directed against the haemagglutinin, the major viral neutralization antigen. There are two major types of interaction, (i) At low concentrations of IgM there is aggregation of virus, but no neutralization provided that the aggregates are dispersed by vortexing and dilution. Maximum aggregation occurs at less than seven molecules of IgM per virion and the IgM is probably bound in the ‘staple’ or ‘crab’ conformation at these concentrations, (ii) At higher concentrations there is neutralization and this coincides with inhibition of attachment of virus to CEF cells. Neutralization of 50% infectivity requires about 35 molecules of IgM per virion. The maximum neutralization observed was only 87%. Quantitative data and electron microscopy observations suggest that molecules of IgM at the higher concentrations adopt a planar stance approximately perpendicular to the viral surface. It appears that IgM neutralizes fowl plague virus in vitro primarily by interfering with its attachment to cells; the fraction of neutralized virus that does attach is known not to be internalized.
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Delineation of canine parvovirus T cell epitopes with peripheral blood mononuclear cells and T cell clones from immunized dogs
Three synthetic peptides derived from the amino acid sequence of VP2 of canine parvovirus (CPV) which were recently shown to represent three distinct T cell epitopes for BALB/c mice could prime BALB/c mice for a CPV-specific proliferative T cell response upon immunization. Proliferative responses of peripheral blood mononuclear cells (PBMC) from CPV-immunized dogs upon stimulation with these and other peptides, covering the major part of the sequence of VP2′, identified the presence of T cell epitopes for this species. Most of these epitopes were recognized by PBMC from only a minority of the dogs tested. With three newly generated canine Thyl+ T cell clones, which recognized CPV antigen in association with major histocompatibility complex class II molecules, two distinct T cell epitopes were identified within the unique sequence of VP1.
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Variable regions on the genome of Malawi isolates of African swine fever virus
More LessRestriction enzyme site mapping showed that most BamHI and all ClaI sites were conserved on the genomes of 17 African swine fever virus isolates from separate disease outbreaks that occurred between 1982 and 1989 in Malawi. However, frequent variation between virus genomes did occur due to addition or deletion of DNA sequences at various positions along the genome and 11 virus genotypes could thus be distinguished among the 17 isolates analysed. Length variations occurred at 10 different loci on the virus genome. These variable regions were located between the left DNA terminus and a position up to 48 kb from that terminus, in the centre of the genome 90 to 93 kb from the left DNA terminus and between the right DNA terminus and a position 22 kb from that terminus. Length variations in most of these regions were small (< 1 kb) but variations of about 4 kb occurred in a region up to 20 kb from the left DNA terminus.
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Structural and functional analysis of orthopoxvirus epitopes with neutralizing monoclonal antibodies
More LessNeutralizing monoclonal antibodies (MAbs) were produced in BALB/c mice immunized with live modified vaccinia virus Ankara or infected with sublethal doses of the neurovirulent vaccinia virus strain Munich 1. The immunization scheme proved to be important for obtaining MAbs of different specificity. The MAbs could be classified into three epitope groups (1 A, 1 B and 2). Immunogold electron microscopy demonstrated that the epitopes were localized on the virus surface. In immunoblotting, MAbs were reactive with polypeptides of 14K, 16K and 30K. Purified MAbs binding to the epitopes 1 A and 2 showed a 50 % reduction of 100 p.f.u./0·05 ml vaccinia virus M1 with respectively 3·9 and 5·9 ng of immunoglobulin/ 0·05 ml. MAbs binding to the epitope 1 B neutralized the virus at a concentration of 250 ng/0·05 ml. In intraperitoneal challenge experiments, MAbs binding to the epitopes 1 A and 2 protected mice against 4 LD50 of vaccinia virus Ml, but not against local lesions by subcutaneous application. MAbs against epitope 1 B had no protective effect in vivo. The three epitopes were present in 14 of 16 orthopoxviruses tested but with quantitative differences. Maximal binding (Vmax ) and the antibody concentration at half-maximal binding (Km ) which were calculated as for Michaelis-Menten kinetics from regression analysis of the ELISA data and the MAb concentration giving 50 % plaque reduction were the basis for the evaluation. In monkeypox virus Kopenhagen the epitopes 1 A and 1 B were absent. MAbs binding to epitope 2 reacted just as well as with vaccinia viruses. Ectromelia virus lacked all the epitopes.
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Biochemical and immunological studies of proteins from polydnavirus Chelonus sp. near curvimaculatus
More LessPolydnavirus from Chelonus sp. curvimaculatus (CcV) was purified and 18 structural polypeptides associated with CcV were identified by silver staining. Antibodies were raised against CcV protein and used in testing for the presence of the virus in different tissues of the wasp ovary and in stung eggs. It was also established that the virus does not enter during the first 5 s of oviposition. Furthermore, no degradation of the virus proteins was detected inside the egg within 2 h after oviposition. The glycoprotein nature of virus proteins was also determined by concanavalin A/horseradish peroxidase staining. The amino acid compositions of the most highly abundant peptides (41K, 33K, 21K, 17K and 13K) were determined, as was the N-terminal amino acid sequence of the 41K protein. The latter did not show similarity with any reported protein sequences.
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Evolutionary relationships of virion glycoprotein genes in the S regions of alphaherpesvirus genomes
More LessThe short region in the genome of herpes simplex virus type 1 contains a contiguous array of five genes (US4, US5, US6, US7 and US8) which encode known or proposed virion-surface glycoprotein species. Counterparts for certain of these have been described in the genomes of other alphaherpesviruses, namely herpes simplex virus type 2, pseudorabies virus and varicella- zoster virus. Within each of the US4-, US6- and US7- related sets, the amino acid sequences are most conserved in a region containing several cysteine residues. Comparisons in this region among the three sets were carried out by first aligning three cysteine residues which were very similarly placed in each set, and a number of other similarities were then visible. It was concluded that the US4, US6 and US7 sets of genes are related, and thus have evolved by duplication and divergence. The US8-related sequences are distinct from the US4, US6 and US7 sequences, although possible signs of a distant relationship were detected. The US8 set contains two clusters of cysteine residues, and the sequences around these show some similarity, which was interpreted as evidence for occurrence of an intramolecular duplication event.
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A single amino acid substitution in the large subunit of herpes simplex virus type 1 ribonucleotide reductase which prevents subunit association
More LessThe herpes simplex virus type 1 temperature-sensitive (ts) mutant ts1207 does not induce detectable levels of ribonucleotide reductase activity at the non-permissive temperature (NPT, 39.5 °C). The ts lesion prevents the association of the enzyme's large (RR1) and small (RR2) subunits to give an active holoenzyme and maps within the gene specifying RR1. Here, it is shown that the ts mutant phenotype is due to the substitution of an asparagine for the wild-type (wt) serine at RR1 position 961, which is located within a region highly conserved between herpesviral and cellular RR1 subunit polypeptides. This ts1207 asparagine is predicted to alter a wt α-helix to a β-strand. We have used synthetic oligopeptides, corresponding to the wt amino acid sequence of the mutation site, and antisera raised against them to determine whether this region is involved in subunit association. Neither the oligopeptides nor the antisera inhibit the enzyme activity, or the reconstituted activity formed by mixing intact RR2 and RR1 subunits present in partially purified extracts of cells infected at the NPT with ts1207 or ts1222 (an HSV-1 mutant with a lesion in the RR2 subunit), respectively. We infer from these results that the site of the mutation is unlikely to be positioned at the surface of RR1 and hence is probably not directly involved in subunit association. We suggest that the mutation site identifies an important RR1 region whose alteration in ts1207 changes the structure of a contact region(s) positioned at the RR1/RR2 interface.
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Herpes simplex virus type 1 UL28 gene product is important for the formation of mature capsids
More LessThe herpes simplex virus type 1 temperature-sensitive (ts) DNA-positive mutant ts1203 has been characterized. The ts lesion in ts 1203 was located by marker rescue within the coding region of gene UL28. Nuclei of cells infected with ts1203 at the non-permissive temperature (NPT) contained large numbers of capsids with a uniform morphology. These capsids lacked DNA but had a defined internal structure. No full capsids were detected at the NPT, suggesting that ts1203 was unable to package viral DNA. In this respect ts1203 is similar to ts1201 which has a defect in gene UL26. The capsids made by ts1203 at the NPT, however, contained a more compact internal structure than those of ts1201. In addition, ts1203 capsids were dispersed throughout the nucleus whereas ts1201 capsids were frequently found clustered together in large arrays. Southern blot and sedimentation analyses of viral DNA confirmed that ts1203 had an encapsida- tion defect and showed that most of the mutant DNA at the NPT was of a high Mr. The effect of the ts1203 mutation could not be reversed in the absence of de novo protein synthesis by transferring mutant-infected cells from the NPT to the permissive temperature.
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Possible latent infection with herpes simplex virus in the mouse eye
More LessHerpes simplex virus (HSV) was isolated from organ cultures of anterior segments of the eyes of mice inoculated with virus on the snout or directly onto the cornea at least 5 weeks previously. The frequency of isolation of the virus was not decreased by treatment of the animals with acyclovir, suggesting that the virus is latent by the criteria usually applied. Peroxidase-antiperoxidase staining of organ cultures that had shed virus showed that viral antigens were predominantly present in the anterior uvea. Inoculation of mouse eye anterior segments in vitro showed that this tissue was the most susceptible to productive infection. These results suggest the possibility that HSV can establish a latent infection in tissues of the anterior segment of the mouse eye.
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Murine cytotoxic T lymphocytes specific for herpes simplex virus type 1 recognize the immediate early protein ICP4 but not ICP0
Vaccinia virus recombinants expressing the herpes simplex virus type 1 (HSV-1) genes encoding ICP0 or ICP4 were used to identify the precise target antigen(s) of murine anti-viral cytotoxic T lymphocytes (CTL) specific for the non-structural immediate early proteins. These studies revealed that HSV-1-specific CTL, restricted to class I major histocompatibility complex genes of the H-2k haplotype but not the H-2d or H-2bhaplotypes, would lyse autologous cells expressing ICP4. HSV-1-specific CTL derived from various mice strains failed to lyse target cells expressing ICP0.Calculation of the frequencies of H-2k-restricted virus-specific CTL demonstrated that approximately a third of the total HSV-1-specific response was directed against ICP4. Immunization of mice with either recombinant vaccinia virus or transfected L cells expressing ICP4 induced HSV-1-specific lymphoproli-feration and delayed hypersensitivity but CTLs were not induced. More importantly, such immunized animals were unable to resist or control a subsequent challenge with virulent HSV-1.
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The role of mucosal antibody in immunity to infectious laryngotracheitis virus in chickens
More LessThe role of mucosal antibody in recovery from a primary infection and resistance to reinfection with infectious laryngotracheitis (ILT) herpesvirus was studied in bursectomized chickens, which were unable to synthesize specific antibodies. Viral antigen in the infected trachea was assessed by indirect immunofluorescence on tissue sections and by ELISA. The ability of bursectomized chickens to resolve primary infections as effectively as intact chickens and of vaccinated-bursectomized chickens to prevent the replication of challenge virus without the participation of mucosal antibody, is evidence for the importance of local cell-mediated rather than humoral immune mechanisms in the outcome of infection with ILT virus.
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Characterization of the high M r glycoprotein (gP300) of equine herpesvirus type 1 as a novel glycoprotein with extensive O-linked carbohydrate
The high Mr glycoprotein (gp300) of equine herpesvirus type 1 was found to have an Mr , estimated by SDS-PAGE, of over 400000 and was confirmed as being a surface glycoprotein by 125I-labelling. In contrast to [3H]glucosamine, gp300 showed very low levels of [3H]mannose incoporation. The Mr of gp300 showed no detectable change upon treatment of purified virus with (N-glycanase, and showed only a small change in virus-infected cells treated with tunicamycin. In addition, gp300 failed to bind the lectin concanavalin A. Taken together, these results indicate a lack of N-linked carbohydrate on gp300. The major carbohydrate species were found to be composed primarily of O-linked chains, as indicated by the sensitivity of the protein to monensin, to exoglycanase enzymes specific for sugars present in O-linked chains and to mild alkaline borohydride treatment, which revealed three species of carbohydrate of Mr of > 10000, 2400 and 1100, respectively. Neuraminidase treatment and binding of Helix pomatia lectin indicated the presence of α- N-acetylglucosamine and sialic acid as terminal sugars. Immunological cross-reactivity of gp300 with a high Mr protein of equine herpesvirus type 4 was shown and it also exhibited a marked Mr variation in the vaccine strain Rhinomune.
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The location and nucleotide sequence of the thymidine kinase gene of bovine herpesvirus type 1.2
More LessOn the basis of their restriction endonuclease digestion patterns, four Australian bovine herpesvirus type 1 (BHV-1) isolates were classified as belonging to the BHV-1.2a subtypes. The thymidine kinase (TK) genes of all four BHV-1.2a isolates were located on a 3·5 kb SalI restriction fragment. This is in contrast to North American and European BHV-1.1 isolates whose TK genes are contained on a 2·6 to 2·8 kb salI fragment. The restriction fragments containing the TK genes were cloned into phagemid vectors and their sequences determined using the dideoxynucleotide chain termination method. The BHV-1.2a isolates possessed identical TK gene sequences, which differed from previously published TK sequences for the LA and 6660 BHV-1.1 strains. In addition to five single base alterations, there were six separate base insertions which resulted in two major frameshifts which spanned an area of 72 amino acids or 20% of the expressed TK gene product. The predicted amino acid sequence exhibited a higher degree of similarity to other herpesvirus TKs, suggesting that previously published TK gene sequences may have been incorrect. The present nucleotide sequence and corresponding amino acid composition reinforces previous observations concerning regions of herpesvirus TK amino acid conservation and should assist in future studies into the evolution and functional domains of herpesvirus TKs.
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Construction of a defective adenovirus vector expressing the pseudorabies virus glycoprotein gp50 and its use as a live vaccine
More LessThe gene encoding the pseudorabies virus glycoprotein gp50 was cloned at the very left end of the genome of adenovirus type 5 to give a recombinant adenovirus (Ad-gp50) defective for the E1A gene. Ad-gp50 expressed high levels of gp50 in cells which either complemented (293 cells) or did not complement (Vero and HeLa cells) the E1A gene. Surprisingly, over an extended period, higher levels of gp50 were produced in HeLa cells which lack the E1A gene. Rabbits and mice inoculated with Ad-gp50 showed a strong antibody response against gp50. Some of them were protected from a virulent challenge with pseudorabies virus.
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The structure of the pseudorabies virus genome at the end of the inverted repeat sequences proximal to the junction with the short unique region
More LessThe complete nucleotide sequence is presented of the 2·67 kbp BamHI-EcoRV portion of the the Bam HI 10 fragment of the pseudorabies virus (PRV) genome (strain Ka) containing sequences upstream of the previously reported protein kinase gene, and completing the sequence of this 4008 bp fragment. It is predicted to contain a gene designated RSp40, homologous to gene US1 of herpes simplex virus type 1 (HSV-1), with the potential to encode a protein of 364 amino acids. Analysis of PRV mRNA synthesized in the presence and absence of cycloheximide indicated that, in contrast to its HSV-1 homologue, the PRV gene RSp40 does not specify an immediate-early mRNA. Between the RSp40 gene and the protein kinase gene are two reiterated sequences: one containing 11 tandem copies of a 35 nucleotide sequence and the other containing nine tandem copies of a 10 nucleotide sequence. The BamHI 10 and the BamHI 12 fragments of PRV contain the junctions between the short unique (Us) and short repeat (Rs) regions of the PRV genome. The nucleotide sequence of that portion of the BamHI 12 fragment containing Us sequences was determined so that, by comparison with the nucleotide sequence of the BamHI 10 fragment, the junction between the Us and Rs regions could be defined. In BamHI 10 this was found to be at a point between the two reiterated sequences (which are in the Rs region) and the protein kinase gene (which is in the Us region). The organization of this region of the PRV genome is compared to that of other alphaherpesviruses.
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