- Volume 75, Issue 2, 1994
Volume 75, Issue 2, 1994
- Animal
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Changes in the dominant Epstein–Barr virus type during human immunodeficiency virus infection
Two types of Epstein-Barr virus (EBV), EBV-1 and EBV-2, were identified on the basis of DNA sequence divergence in the genes for nuclear proteins EBNA 2, 3a, 3b and 3c. In the present study, we conducted an immunological and genomic analysis in a human immunodeficiency virus (HIV)-infected population to determine the prevalence of the two types, and whether the identified type was stable over years. The EBNA-2 serotyping and genotyping showed that HIV-infected patients were highly infected by EBV-2, and that the dominant strain was mostly retained. However, during a follow-up study, a change in the dominant viral strain was observed in two patients. A first HIV-positive patient (patient A), although having a stable level of anti- EBNA-2A and -2B antibodies, showed a change in the genotype and antigen produced in spontaneously established lymphoblastoid cell lines (LCL). The sequence analysis of LCLs confirmed the emergence of the EBV- 2 type population. A strain from a second HIV-positive patient (patient B) was clearly identified as EBV-2: the genotype from a saliva sample and from sequential LCLs belonged to EBV-2, as well as the antigen produced from LCLs, and serum antibodies. After a 5-year continuous EBV-2 infection, a reactivation of the EBV-1 strain was observed. In both cases, sequence analysis of the EBNA- 2 gene showed, only with EBV-1, the presence of EBV variants related to the B95-8 prototype. Two mutations (at nucleotides 49212 and 49304) were found in both patients A and B, whereas an additional mutation (at nucleotide 49237) was characteristic of the patient A. No mutation relative to the prototype B95-8 strain was observed in a subsequent analysis of this EBNA-2 region from LCLs obtained from two HIV-negative patients predominantly infected by EBV-1. Therefore, we speculate that these mutations may be EBV-1 mutations specifically occurring during HIV infection.
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The equine herpesvirus type 1 glycoprotein homologous to herpes simplex virus type 1 glycoprotein M is a major constituent of the virus particle
More LessGlycoprotein 45 is a major envelope glycoprotein of equine herpesvirus type 1. The gene encoding this protein is located between map units 0·615 and 0·636 on the virus genome and evidence has suggested that it is encoded by gene 52, one of four genes within this region. Using PCR we have amplified gene 52 and subsequently cloned it into a mammalian expression vector under the control of the human cytomegalovirus immediate early gene promoter. The gene was expressed in COS-7 cells and its product was detected by immunofluorescence and Western blotting. The results indicate that glycoprotein 45 is encoded by gene 52, and that it is the homologue of herpes simplex virus type 1 glycoprotein M.
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A novel hepatitis B virus variant in the sera of immunized children
A novel hepatitis B virus (HBV) variant was detected in the sera of two children in The Gambia, West Africa. The children had been immunized with plasma-derived vaccine and had developed antibody titres of 1448 international units × 10 −3 (mIU)/ml and 133 mIU/ml respectively against the hepatitis B surface antigen (HBsAg). Despite the protective levels of antibodies, HBV DNA was subsequently detected in both children. The complete surface (S) protein gene sequence demonstrated that this HBV isolate was closely related to the ayw4 subtype. However, five nucleotide changes were identified and two of these were unique to the Gambian isolate. One of these changes was within the region of the S gene coding for the immunodominant a determinant of the S protein. A unique nucleotide change from adenosine to guanosine at nucleotide 421 was found, resulting in an amino acid substitution at residue 141 from lysine to glutamic acid. Previous studies have shown that amino acids 141 to 146 are critical for binding to the protective anti-HBsAg antibodies. The presence of a variant HBV in these children suggests the emergence of a novel strain of HBV which can evade immune recognition. This has potential implications for HBV diagnosis and prophylaxis.
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Intracellular retention of hepatitis B virus surface protein mutants devoid of amino-terminal pre-S1 sequences
More LessTo study the mechanism of L protein-mediated, intracellular (pre-Golgi) retention of hepatitis B virus (HBV) surface proteins, a collection of HBV preS-S open reading frame variants bearing wild-type or modified preS extensions was expressed in human cells. When the secretion phenotype of the corresponding proteins was analysed, all surface proteins with rearranged preS domains were found to be at least partially retained. This held true, in particular, for two variant proteins lacking preSl amino acids 1 to 19 (ayw), the preSl myristylated N terminus and a putative retention domain, and for another variant lacking the entire preSl domain plus the N-terminal portion (amino acids 1 to 12) of the preS2 domain. All the retained variants underwent intracellular dimerization/oligomerization via disulphide bonds to a degree comparable to that observed in well exported natural proteins. Our results show that retention can take place in the absence of L N-terminal sequences and does not imply inhibition of covalent oligomerization.
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- Plant
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Nucleotide sequence and genome characterization of rice yellow mottle virus RNA
The genome of rice yellow mottle virus (RYMV) is a single-stranded positive-sense RNA that is not poly- adenylated, and has an Mr of 1·4 × 106. We present here the 4550 nucleotide (nt) sequence of RYMV RNA, and its predicted genomic organization. The RYMV genomic RNA contains four open reading frames (ORFs). The first (nt 80 to 553) encodes a protein containing 157 amino acids with a predicted Mr of 17·8K. No function has yet been attributed to this product. ORF2 (nt 608 to 3607) encodes a polyprotein of 999 amino acids, with a predicted Mx of 110·7K. The first 134 amino acids of ORF2 are predicted to be the genome-linked protein, VPg, followed by the viral protease, the helicase and the RNA-dependent RNA polymerase. ORF3 is within the boundaries of ORF2 and is predicted to encode a polypeptide with 126 amino acids and an Mr of 13·7K. No function has yet been attributed to this protein. ORF4 (nt 3447 to 4166), which overlaps the 3ʹ terminus of ORF2, encodes a 26K protein. This polypeptide has been identified as the RYMV coat protein. The data presented here confirm that RYMV belongs to the sobemovirus group and thus is a member of the picoma- like family of plant viruses.
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Genome characterization and taxonomy of Plantago asiatica mosaic potexvirus
The complete nucleotide sequence of Plantago asiatica mosaic virus (PlAMV) genomic RNA has been determined. The 6128 nucleotide sequence contains five open reading frames (ORFs) coding for proteins of M r 156K (ORF1), 25K (ORF2), 12K (ORF3), 13K (ORF4) and 22K (ORF5). The sequences of these PlAMV proteins exhibit strong homology to the proteins of the other potexviruses. Phylogenetic trees based on the multiple sequence alignments of three conserved domains in ORF1 product and capsid protein reveal a close relationship of PlAMV to papaya mosaic virus and clover yellow mosaic virus. The PlAMV genomic RNA and a major subgenomic RNA (sgRNA) of 0·9 kb have been detected in infected leaves by Northern blot hybridization. The latter sgRNA is the messenger for virus capsid protein and its 5′ terminus has been located 23 nucleotides upstream of the initiator codon of the coat protein gene. The PlAMV virion RNA and RNA transcript resembling the 0·9 kb sgRNA have been translated in vitro giving rise to a single major 170K product and a major 22K product, respectively.
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Conserved primary structures in core capsid proteins and reassembly of core particles and outer capsids between rice gall dwarf and rice dwarf phytoreoviruses
More LessThe nucleotide sequence of the S3 genome segment of rice gall dwarf virus, a phytoreovirus, consisted of 3224 bp and sequence analysis showed that the segment potentially encoded a 116K major core capsid protein of the virus. This 116K protein and the 114K major core capsid protein of rice dwarf virus are similar in size and were found to have amino acid sequence homology as high as that between the major outer capsid proteins of the two viruses. Core particles and outer capsids of these viruses were interchangeable, suggesting conformational similarity in the three-dimensional architecture of their core and outer capsid proteins.
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The nucleotide sequence of potato virus A genomic RNA and its sequence similarities with other potyviruses
More LessThe complete nucleotide sequence of potato virus A (PVA) was obtained from six independent cDNA clones. The RNA genome of PVA is 9565 nucleotides long and contains one open reading frame (ORF) of 9177 bases encoding a large polyprotein of 3059 amino acids with a calculated M r of 340K. Seven potential proteinase NIa, one HC-pro and one P1 proteinase recognition sites were found in PVA polyprotein by searching for cleavage site consensus sequences amongst the potyvirus group. The non-coding region preceding the ORF is 161 nucleotides long. The termination codon is followed by a 227-nucleotide sequence. Overall nucleotide sequence identity compared with several completely sequenced potyvirus genomes is between 53 and 58 %, with overall amino acid sequence identity between 65 and 71%. When the putative amino acid sequences of individual proteins of PVA were compared with the corresponding proteins of other potyviruses, P1 and P3 appeared the least conserved (34 to 53 %) whereas the other proteins were in most cases from 63 to 80% identical to each other.
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Alleged reaction in gel-immunodiffusion of an IgM monoclonal antibody with alfalfa mosaic virus and cucumber mosaic virus is an artefact
More LessA previously reported spurious serological crossreaction between alfalfa mosaic virus (AMV) and cucumber mosaic virus (CMV), which had been defined by the reaction in gel-immunodiffusion tests of a single IgM monoclonal antibody (MAb), MAb 8, was no longer detected in the presence of 0·1 m-NaCl. The non-specific reactivity of this IgM was also confirmed in Western blotting assays. When skimmed milk was used as a blocking agent and as a diluent of antibodies, MAb 8 failed to recognize AMV and CMV coat proteins. Hence, it is concluded that the alleged cross-reaction between AMV and CMV is due to non-specific binding of MAb 8 and that there is no evidence for a serological relationship between these two viruses.
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