Virus Genes

A unique feature of the Epstein-Barr virus (EBV) genome is its high content of repetitive sequences. We identified a new human minisatellite element, tentatively designated MEB-1, that is similar to the 10 × “15bp” tandem repeat within the EBV nuclear antigen-3C (EBNA-3C) coding region. Southern blot analysis showed that the human genome has multiple copies of MEB-1-related repeats and that some of them are highly polymorphic. Both MEB-1 and the 10 × “15bp” repeat contain an octamer consensus GC[A/T]GG[A/T]GG, resembling the prokaryotic recombination signalchi. This octamer was also found in another EBV repeat sequence IR3 and the cellular GGA family of repeats that are related to IR3. Since the octamer motif is generally considered to have a role in the generation of a group of minisatellite DNA, these findings suggest that the four viral and cellular repeats have been generated through similar mechanisms promoted by the motif.

TheSpodoptera littoralis multicapsid nuclear polyhedrosis virus (SlMNPV) is a member of the Baculoviridae that shows a distant genetic relationship to the prototypeAutographa californica MNPV (AcMNPV). Using anAcMNPV gene-specific probe, we identified and mapped an ecdysteroid UDP-glucosyltransferase (egt) gene in the genome ofSlMNPV. Sequence determination of a part from the hybridizing DNA fragment revealed an open reading frame of 1548 nucleotides that exhibits 38% and 44% identity to theegt amino acid sequences ofAcMNPV andLymantria dispar MNPV (LdMNPV), respectively. Sequences flanking theSlMNPVegt gene, including the promoter region, were found to be unique to the virus. The presence of this nonstructural gene inSlMNPV and several other baculoviruses points to the importance ofegt for the viral infection process.

African swine fever virus (ASFV) is highly contagious and can cause lethal disease in pigs. ASFV p72 protein is a major capsid protein that presents as trimer in the virion. Epitopes on the surface of p72 trimer are considered as protective antigens. In this study, recombinant p72 protein and p72-baculovirus were constructed and obtained. Three monoclonal antibodies (mAbs) specific to ASFV p72 protein, designated as 1A3, 2B5 and 4A5, were generated. Among them, 4A5 showed strong reactivity with ASFV infected cells. Subsequently, the epitope recognized by 4A5 was mapped and identified using a series of overlapping peptides generated from p72 protein. IFA and western blot analyses showed that 4A5 recognized the linear epitope of p72 monomer located between amino acids 245–285 and recognized the conformational epitope located at the surface and top of the p72 trimer. These findings will enrich our knowledge regarding the epitope on p72 protein and provide valuable information for further characterization of the antigenicity and molecular functions of p72 protein.

Post-translational modification of proteins is a key regulatory event in many cellular processes. African swine fever virus (ASFV) is a large DNA virus that contains about 150 open reading frames (ORF) which encode for more than 150 polypeptides, most of them without assigned function. Two-dimensional gel electrophoresis (2DE) followed by Post-Source Decay Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (PSD-MALDI-MS) revealed that ASFV protein pE120R, essential for virus transport from assembly sites to plasma membranes, is acetylated at the N-terminal Ala residue during infection. To our knowledge, this is the first acetylated ASFV protein described and this modification might be relevant to ASFV life cycle since many viruses use the acetylation signaling pathway as a primary target for viral proteins after infection.

The complete nucleotide sequences of genomic segments S5 to S10 from Operophtera brumata cypovirus 18 (OpbuCPV18), and the complete nucleotide sequences of genomic segments S2, S5, S9 and S10 from Operophtera brumata cypovirus 19 (OpbuCPV19) have been determined. Each genome segment contained a single open reading frame (ORF). Conserved motifs 5′ (AGUAAA....GUUAGCU) 3′ were found at the ends of each segment of OpbuCPV18, whilst conserved motifs 5′ (AACAAA....UUUGC) 3′ were found at each segment terminus of OpbuCPV19. The putative proteins were compared with those of other members of the Reoviridae family. Phylogenetic analysis using the polyhedrin gene (S10) indicated that OpbuCPV18 was most closely related to Dendrolimus punctatus cypovirus 1, whilst OpbuCPV19 was most closely related to Trichoplusia ni cypovirus 15. In addition, analysis of S2, which encoded a putative RNA-dependant RNA polymerase gene, confirmed OpbuCPV19 belonged to the genus Cypovirus. Following the expression of the ORF from OpbuCPV19 S10, using a baculovirus expression vector, occlusion bodies were observed in insect cell culture. This demonstrated that segment 10 coded for the polyhedrin gene, capable of forming a polyhedral crystalline matrix.

Thousands of scientists participated in the World of Microbes Congress, which was organized by the International Union of the Microbiological Societies (IUMS) and took place in the Palais de Congres in Paris, France from 27 July to 1 August 2002. The attendees were members of the IUMS divisions of Bacteriology and Applied Microbiology, Mycology, and Virology. In addition to the symposia that were organized by each division, joined plenary symposia were held, which encompassed subjects of common interest to all microbiologists. The activities at the 12th Congress of Virology's plenary lectures, symposia, and poster sessions were organized to accommodate the presentation of over 1500 presentations. These brief comments are aimed to provide a sample of only a few presentations that dealt with subjects of emerging and re-emerging virus diseases, which are of general interest.

Beet curly top Iran virus (BCTIV) was previously reported as a distinct curtovirus in Iran. Complete nucleotide sequences of three BCTIV isolates, one each from central, southern, and south eastern Iran were determined to be 2844, 2844, and 2845 nt long, respectively. BCTIV shared highest nucleotide sequence identity (52.3%) with Spinach curly top virus (SpCTV) and lowest identity (46.6%) with Horseradish curly top virus (HrCTV). The BCTIV genome comprises three virion-sense (V1, V2, and V3) and two complementary-sense (C1 and C2) ORFs. ORFs C3 and C4 were not found in BCTIV genome. Based on a comparison of nucleotide sequence identity of individual genes, the three virion-sense ORFs were 72.7–79.9% related to the corresponding ORFs of curtoviruses, whereas no significant relationship was found between the C1 and C2 ORFs of BCTIV and curtoviruses. These two ORFs, however, were only distantly related with those of mastreviruses. Similar to the latter viruses, the BCTIV genome comprises two intergenic regions. The BCTIV large intergenic region included a sequence capable of forming a stem loop structure and a novel nonanucleotide (TAAGATT/CC) with a unique nick site. Phylogenetic analysis using deduced amino acid sequence of individual ORFs revealed that the V2 and V3 ORFs are monophyletic and the V1 ORF is classified with the related ORF of curtoviruses. Whereas the two complementary-sense ORFs are grouped with those of mastreviruses. Computer-based prediction suggested that BCTIV has a chimeric genome which may have arisen by a recombination event involving curto- and mastrevirus ancestors. Percent nucleotide sequence identities of the coat protein gene of ten isolates of BCTIV, collected from a wide range of geographical regions in Iran, varied from 87.1 to 99.9, with the isolates being distributed between two subgroups. Based on biological and molecular properties, BCTIV is proposed as a new member of the genus Curtovirus.

The amino acid sequences of the large proteins of potexviruses and tymoviruses were aligned. It was shown that three domains of these proteins display significant similarity between the two virus groups. In contrast to central (putative NTPase-helicase) and C-terminal (putative polymerase) domains, the conservative N-terminal domain of the potexvirus/tymovirus large protein displayed no obvious similarity to the respective regions of the large proteins of other Sindbis-like viruses.