bluuebunny/crossref_metadata_2025 huggingface dataset:
Tropism of human cytomegalovirus for endothelial cells is determined by a post-entry step dependent on efficient translocation to the nucleus
Authors: Sinzger C. , Kahl M. , Laib K. , Klingel K. , Rieger P. , Plachter B. , Jahn G.
Published: August 2015

Marked interstrain differences in the endothelial cell (EC) tropism of human cytomegalovirus (HCMV) isolates have been described. This study aimed to define the step during the replicative cycle of HCMV that determines this phenotype. The infection efficiency of various HCMV strains in EC versus fibroblasts was quantified by immunodetection of immediate early (IE), early and late viral antigens. Adsorption and penetration were analysed by radiolabelled virus binding assays and competitive HCMV-DNA-PCR. The translocation of penetrated viral DNA to the nucleus of infected cells was quantified by competitive HCMV-DNA-PCR in pure nuclear fractions. The intracytoplasmic translocation of capsids that had penetrated was followed by immunostaining of virus particles on a single particle level; this was correlated with the initiation of viral gene expression by simultaneous immunostaining of viral IE antigens. The infectivity of nonendotheliotropic HCMV strains in EC was found to be 100–1000-fold lower when compared to endotheliotropic strains. The manifestation of this phenotype at the level of IE gene expression indicated the importance of initial replication events. Surprisingly, no interstrain differences were detected during virus entry. However, dramatic interstrain differences were found regarding the nuclear translocation of penetrated viral DNA. With nonendotheliotropic strains, the content of viral DNA in the cell nucleus was 100–1000-fold lower in EC when compared to endotheliotropic strains, thereby reflecting the strain differences in IE gene expression. Simultaneous staining of viral particles and viral IE antigen revealed that interstrain differences in the transport of penetrated capsids towards the nucleus of endothelial cells determine the EC tropism of HCMV.
Auto-activation of the rta gene of human herpesvirus-8/Kaposi’s sarcoma-associated herpesvirus
Authors: Deng Hongyu , Young Arthur , Sun Ren
Published: August 2015

Rta, mainly encoded by open reading frame 50 (ORF50), is the product of an immediate-early gene of human herpesvirus-8 (HHV-8)/Kaposi’s sarcoma-associated herpesvirus. Rta is a transcriptional activator that is both necessary and sufficient to disrupt viral latency and activate the expression of downstream viral lytic genes. We report that ectopically expressed Rta protein could also activate the rta promoter on a reporter plasmid up to 144-fold, both in latently infected B cells and in uninfected epithelial cells, and that this activation was dose-dependent. Furthermore, by analysing the 5′ untranslated region using ribonuclease protection assays, we demonstrated that transfection of an Rta expression plasmid into latently infected cells activated the expression of rta transcripts from endogenous viral genomes. We propose that auto-activation of the immediate-early gene, rta, is an important strategy for HHV-8 to effectively respond to environmental stimuli and maximally activate the virus lytic cycle.
Characterization of two novel Microplitis demolitor polydnavirus mRNAs expressed in Pseudoplusia includens haemocytes
Authors: Trudeau D. , Witherell R. A. , Strand M. R.
Published: August 2015

The braconid waspMicroplitis demolitorcarriesM. demolitorpolydnavirus (MdPDV) and parasitizes the larval stage of the mothPseudoplusia includens. M. demolitorinjects MdPDV intoP. includenslarvae when it lays an egg and the virus infects various cells including haemocytes. Two new MdPDV transcripts expressed in host haemocytes were characterized in this study. Screening of an MdPDV-infected haemocyte cDNA library identified a 0·4 kb cDNA encoding a predicted protein of 103 amino acids which was named Egf0·4. This protein contained a cysteine-rich epidermal growth factor (EGF)-like motif at its N terminus that was similar to the EGF-like domains in the previously identified MdPDV genesegf1·5andegf1·0. Sequencing of the genomic clone pMd-10 indicated that it contained theegf0·4gene, which consisted of two introns and three exons. This gene was located on MdPDV segment O and appeared to exist in multiple copies. A nucleic acid and expression screen identified a 1·8 kb cDNA encoding a predicted protein of 515 amino acids designated Glc1·8. This protein consisted of a heavily glycosylated central core of six tandemly arranged repeats flanked by hydrophobic N- and C-terminal domains. Northern blotting andin situhybridization studies indicated that bothegf0·4andglc1·8were expressed in MdPDV-infected host haemocytes. Immunocytochemical studies also indicated that Glc1·8 localized to the cell surface.
Activities associated with the putative replication initiation protein of Coconut foliar decay virus, a tentative member of the genus Nanovirus
Authors: Merits Andres , Fedorkin Oleg N. , Guo Deyin , Kalinina Natalia O. , Morozov Sergey Yu.
Published: August 2015

The putative replication initiation protein (Rep) of Coconut foliar decay virus (CFDV) was expressed as a 6× His recombinant protein inE. coliand in recombinant baculovirus. Purified 6× His–Rep protein was demonstrated to possess sequence non-specific RNA- and ssDNA-binding activities as well as magnesium-dependent ATPase/GTPase activity. The yeast two-hybrid system revealed that CFDV Rep could interact with itself. Subcellular distribution of the CFDV Rep was studied by fractionation of insect cells infected with recombinant baculovirus expressing the 6× His–Rep protein and by laser scanning confocal microscopy ofNicotiana benthamianaepidermal cells bombarded with a construct encoding CFDV Rep fused to GFP. It was shown that CFDV Rep associated predominantly with nuclei and membranes of infected/transfected cells. These activities of CFDV-encoded Rep are very similar to those reported for Reps of geminiviruses.
A novel RNA mycovirus in a hypovirulent isolate of the plant pathogen Diaporthe ambigua
Authors: Preisig O. , Moleleki N. , Smit W. A. , Wingfield B. D. , Wingfield M. J.
Published: August 2015

Hypovirulent isolates of the fruit tree fungal pathogen Diaporthe ambigua have previously been shown to harbour a double-stranded (ds)RNA genetic element of about 4 kb. In this study, we established the complete cDNA sequence of this dsRNA, which represents a replicative form of a positive-strand RNA virus that we have named D. ambigua RNA virus (DaRV). The nucleotide sequence of the genome is 4113 bp and has a GC content of 53%. Two large ORFs are present in the same reading frame. They are most probably translated by readthrough of a UAG stop codon in the central part of the genome. The longest possible translation product (p125) has a predicted molecular mass of about 125 kDa. A significant homology can be found to the non-structural proteins of carmoviruses of the positive-strand RNA virus family Tombusviridae. These proteins also include the conserved RNA-dependent RNA polymerase (RDRP) domain. In contrast to the genome organization of these plant viruses, no ORF is present at the 3′ end of the DaRV genome that encodes a coat protein. Therefore, it is proposed that DaRV is not encapsidated but that it occurs as RNA–RDRP complexes and/or that it might be associated with cell membranes. Interestingly, six putative transmembrane helices are predicted in the N-terminal part of p56 (translation product of the first ORF, N-terminal part of p125), which might direct and anchor the viral complex to membranes. DaRV is a mycovirus with a unique genome organization and has a distant relationship to the plant virus family Tombusviridae.
α6 integrin is not the obligatory cell receptor for bovine papillomavirus type 4
Authors: Sibbet Gary , Romero-Graillet Christine , Meneguzzi Guerrino , Campo M. Saveria
Published: August 2015

Recently, α6 integrin has been proposed as the epithelial cell receptor for papillomavirus. This study investigated whether α6 integrin is the cellular receptor for bovine papillomavirus type 4 (BPV-4), which is strictly epitheliotropic and infects the mucous epithelium of the upper digestive tract. Primary bovine mucosal keratinocytes from the palate of a foetus (PalK) displayed high levels of α6 integrin; matched primary fibroblasts from the same biopsy (PalF) expressed almost no α6 integrin. However, BPV-4 bound both PalK and PalF to similar, saturable levels. Native BPV-4 virions infected PalKin vitro, as detected by RT–PCR of E7 RNA. Infection could be blocked by excess virus-like particles (VLPs) and by neutralizing antisera against L1–L2 and L1 VLPs or by denaturation of the virions, supporting the view that infectionin vitromimics the processin vivo. α6 integrin-negative human keratinocyte cell lines were derived from patients affected by junctional epidermolysis bullosa presenting genetic lesions in their hemidesmosomes. The level of α6 integrin expression was determined in these cell lines byin situimmunofluorescence and FACS. Despite the absence of α6 integrin expression by BO-SV cells, they were bound by BPV-4 to similar, saturable levels as normal keratinocytes, KH-SV. Furthermore, BO-SV and KH-SV cells were both infected by BPV-4 to apparently the same extent as PalK cells. These results are consistent with the conclusion that α6 integrin is not the obligatory receptor for a bovine mucosotropic papillomavirus.
Relationships within and between genotypes of hepatitis B virus at points across the genome: footprints of recombination in certain isolates
Authors: Bowyer S. M. , Sim J. G. M.
Published: August 2015

Hepatitis B virus (HBV) was partitioned into type, subtype and isolate categories and the average evolutionary distances within and between categories was plotted at each of 54 points along the genome. The graphs showed alternating variable and conserved domains within and between HBV subtypes and revealed that some specimens assigned to different groups are more similar across several contiguous intervals than specimens belonging to the same group. Isolates were screened individually to determine their conformation to type and mosaic structure was identified in 14/65 specimens. Two entire clades (six specimens) of genotype B had a B/C sequence switch in the core gene region, whereas six genotype D specimens showed D/A switching in one or more regions of the genome. Genotype E was not separate from genotype D in the X and C subgenomic regions. The nature and distribution of polymorphic sites in mosaic regions was mapped at both the nucleotide and protein levels and the position of the variant fragments was related to mutational hot spots and linear epitopes of HBV. Mosaic structure was demonstrated statistically in 11 isolates using bootstrap resampling and recombination, rather than random change, appeared to be the mechanism responsible. The sequence between and including the two DR regions was represented in all putative recombinants. The distribution of genetic distances over subgenomic regions showed that substitution rates are not constant among the lineages of HBV in the preS regions. Genotype F is the most diverse group. Only genotypes A, C and F partition consistently into subtypes.
Diminished secondary CTL response in draining lymph nodes on cutaneous challenge with herpes simplex virus
Authors: Jones Claerwen M. , Cose Stephen C. , McNally James M. , Jennings Stephen R. , Heath William R. , Carbone Francis R.
Published: August 2015

We have shown that C57BL/6-derived CD8+CTL specific for an immunodominant herpes simplex virus type 1 (HSV-1) glycoprotein B (gB) determinant express a highly conserved Vβ10/junctional sequence combination. This extreme T cell receptor β-chain bias can be used to track the activation of gB-specific CTL in lymph nodes draining the site of HSV-1 infection. In this report we have examined the accumulation of gB-specific CTL in the primary and secondary or recall CTL responses to HSV-1 infection. We found that gB-specific cytolytic activity present within popliteal lymph nodes draining HSV-infected foot-pads peaked at day 5 post-infection during the primary response. As found previously, this correlates with the accumulation of Vβ10+CD8+CTL in the activated T cell subset. Lymph node-derived cytotoxicity peaked between days 3 and 4 on secondary challenge with virus and, somewhat surprisingly, was considerably below that seen in the primary response. This reduced gB-specific cytolytic activity mirrored a near absence of Vβ10+CD8+T cell enrichment found within the draining lymph nodes during this recall response, consistent with the overall diminution of gB-specific CTL accumulation in this site. Finally, there was a second wave of biased accumulation of Vβ10+CD8+activated T cells within the popliteal lymph nodes well after the resolution of infection in both the primary and secondary responses. These results are discussed in terms of preferential activation of virus-specific memory T cells directly in infected tissues during a secondary CTL response at the expense of draining lymphoid organs.
Identification of a new cleavage site of the 3C-like protease of rabbit haemorrhagic disease virus
Authors: Joubert Pascale , Pautigny Carine , Madelaine Marie-Françoise , Rasschaert Denis
Published: August 2015

The calicivirus rabbit haemorrhagic disease virus (RHDV) possesses a 3C-like protease which processes the RHDV polyprotein. In order to monitor the proteolytic activity of the RHDV 3C-like protease on its putative target sequences, i.e. the 10 EG dipeptide bonds distributed along the large polyprotein, a new approach was carried out. Preliminary experiments showed that the luciferase gene when fused in-frame with a long gene yielded a fusion protein almost devoid of luciferase activity. This reporter system was used to test which EG dipeptide bonds were cleaved by the RHDV protease when the coding sequences of the dipeptides and their flanking sequences were inserted at the junction between the protease and luciferase genes. The coding sequences of the fusion proteins were cloned downstream of the T7 promoter and the proteolytic activity was evaluated by measuring the luciferase activity in both in vitro and ‘in vivo’ systems. The EG dipeptide bonds at positions 718–719, 1108–1109 and 1767–1768 were confirmed as cleavage sites and a new cleavage site EG (143–144) was identified.
Changes of leukocyte phenotype and function in the broncho-alveolar lavage fluid of pigs infected with porcine reproductive and respiratory syndrome virus: a role for CD8+ cells
Authors: Samsom Janneke N. , de Bruin Tiny G. M. , Voermans John J. M. , Meulenberg Janneke J. M. , Pol Jan M. A. , Bianchi Andre T. J.
Published: August 2015

Porcine reproductive and respiratory virus (PRRSV) primarily infects and destroys alveolar macrophages of the pig. The aim of the present study was to characterize the changes of leukocyte populations in the broncho-alveolar lavage fluid (BALF) of PRRSV-infected pigs. Piglets were inoculated intranasally with PRRSV strain LV ter Huurne. On various days post-infection the piglets were sacrificed and the lungs removed, washed semi-quantitatively and analysed by flow cytometry. The total number of recovered BALF cells increased approximately 10 times between day 10 and day 21 of infection and decreased thereafter. The number of small low-autofluorescent cells (SLAC), i.e. lymphocytic and monocytic cells, increased very strongly from day 2 until day 21 of infection; in contrast, the number of large highly autofluorescent cells (LHAC), i.e. mostly macrophages, remained constant until day 14 of infection, increased slightly on day 21 and then decreased. On day 21 of infection in specific-pathogen-free piglets approximately 60% of the SLAC consisted of CD2+CD8+CD4−γδTCR− cells, which were partly CD8+CD6+ and partly CD8+CD6−. These phenotypes correspond to that of cytotoxic T-cells and natural killer cells respectively. From these results we can conclude that during a PRRSV infection the total number of BALF cells increases mainly due to an influx of lymphocytic cells with a cytolytic phenotype.
Broadening of coreceptor usage by human immunodeficiency virus type 2 does not correlate with increased pathogenicity in an in vivo model
Authors: van der Ende M. E. , Guillon C. , Boers P. H. M. , Gruters R. A. , Racz P. , Tenner-Racz K. , Osterhaus A. D. M. E. , Schutten M.
Published: August 2015

The pathogenic properties of four primary human immunodeficiency virus type 2 (HIV-2) isolates and two primary HIV-2 biological clones were studied in anin vivohuman-to-mouse chimeric model. The cell-associated viral load and the ability to reduce the severity of the induced graft-versus-host disease symptoms, the CD4/CD8 ratio and the level of repopulation of the mouse tissues by the graft, were determined. All HIV-2 strains, irrespective of theirin vitrobiological phenotype, replicated to high titres and significantly reduced graft-versus-host disease symptoms as well as the CD4/CD8 ratios. Reduction of graft repopulation caused by infection with the respective HIV-2 strains showed that thein vitroreplication rate, syncytium-inducing capacity and ability to infect human macrophages did influence thein vivopathogenic potential whereas broadening of coreceptor usage did not.
Molecular characterization of the genome of a partitivirus from the basidiomycete Rhizoctonia solani
Authors: Strauss Ethan E. , Lakshman Dilip K. , Tavantzis Stellos M.
Published: August 2015

The bisegmented genome of a double-stranded (ds) RNA virus from the fungusRhizoctonia solaniisolate Rhs 717 was characterized. The larger segment, dsRNA 1, is 2363 bases long whereas the smaller segment, dsRNA 2, has 2206 bases. The 5′ ends of the coding strands of dsRNA 1 and dsRNA 2 are highly conserved (100% identity over 47 bases), and contain inverted repeats capable of forming stable stem–loop structures. Analysis of the coding potential of each of the two segments showed that dsRNAs 1 and 2 could code for polypeptides of 730 aa (bases 86–2275; molecular mass 86 kDa) and 683 aa (bases 79–2130; molecular mass 76 kDa), respectively. The 86 kDa polypeptide has all the motifs of dsRNA RNA-dependent RNA polymerases (RDRP), and has significant homology with putative RDRPs of partitiviruses fromFusarium poaeandAtkinsonella hypoxylon. The 76 kDa protein shows homology with the putative capsid proteins (CP) of the same viruses. Northern blot analysis revealed no subgenomic RNA species, consistent with the fact that the long open reading frames encoding the putative RDRP and CP cover the entire length of the respective dsRNAs.
High genetic variability of the group-specific a-determinant of hepatitis B virus surface antigen (HBsAg) and the corresponding fragment of the viral polymerase in chronic virus carriers lacking detectable HBsAg in serum
Authors: Weinberger Klaus M. , Bauer Tanja , Böhm Stephan , Jilg Wolfgang
Published: August 2015

Chronic carriers of hepatitis B virus (HBV) usually show hepatitis B surface antigen (HBsAg) in their sera, which is considered the best marker for acute and chronic HBV infection. In some individuals, however, this antigen cannot be detected by routine serological assays despite the presence of virus in liver and peripheral blood. One reason for this lack of HBsAg might be mutations in the part of the molecule recognized by specific antibodies. To test this hypothesis, the HBV S gene sequences were determined of isolates from 33 virus carriers who were negative for HBsAg but showed antibodies against the virus core (anti-HBc) as the only serological marker of hepatitis B. Isolates from 36 HBsAg-positive patients served as controls. In both groups, a considerable number of novel mutations were found. In isolates from individuals with anti-HBc reactivity only, the variability of the major hydrophilic loop of HBsAg, the main target for neutralizing and diagnostic antibodies, was raised significantly when compared with the residual protein (22·6 vs 9·4 mutations per 1000 amino acids; P<0·001) and with the corresponding region in the controls (22·6 vs 7·5 exchanges per 1000 residues; P<0·001). A similar hypervariable spot was identified in the reverse transcriptase domain of the viral polymerase, encoded by the same nucleotide sequence in an overlapping reading frame. These findings suggest that at least some of the chronic low-level carriers of HBV, where surface antigen is not detected, could be infected by diagnostic escape mutants and/or by variants with impaired replication.
Evolution of human polyomavirus JC
Authors: Hatwell John N. , Sharp Paul M.
Published: August 2015

More than 20 near full-length genome sequences have been reported for human polyomavirus JC (JCV). These have previously been classified into seven genotypes, and additional subtypes, which exhibit geographical associations. One of these genotypes, Type 4, has been suggested to be a recombinant of Types 1 and 3. We have investigated the pattern of diversity, and evolutionary relationships, among these sequences. In direct contradiction of a recent report, we found that different phylogenetic methods gave consistent results for the phylogenetic relationships among strains. The single known strain representing Type 5 was shown to be a mosaic of sequences from Types 2 and 6, although whether this recombination occurred in vivo or in vitro is not clear. In contrast, there was no substantial evidence that Type 4 strains are recombinant; rather they seem to be simply divergent examples of Type 1. On the assumption that the major genotypes of JCV diverged with human populations, the rate of synonymous nucleotide substitution was estimated to be around 4×10−7 per site per year, about 10 times higher than a previous estimate for primate polyomaviruses.
Ectromelia, vaccinia and cowpox viruses encode secreted interleukin-18-binding proteins
Authors: Smith Vincent P. , Bryant Neil A. , Alcamí Antonio
Published: August 2015

Interleukin-18 (IL-18) is a proinflammatory cytokine that plays a key role in the activation of natural killer and T helper 1 cell responses principally by inducing interferon-γ (IFN-γ). Human and mouse secreted IL-18-binding proteins (IL-18BPs) have recently been described which block IL-18 activity but have no sequence similarity to membrane IL-18 receptors. Several poxvirus genes encode proteins with sequence similarity to IL-18BPs. Here we show that vaccinia, ectromelia and cowpox viruses secrete from infected cells a soluble IL-18BP (vIL-18BP) that may modulate the host antiviral response. The ectromelia virus protein was found to block NF-κB activation and induction of IFN-γ in response to IL-18. The highly attenuated vaccinia virus modified virus Ankara encodes IL-18-binding activity, and thus deletion of the vIL-18BP may improve further the safety and immunogenicity of this promising human vaccine candidate. We confirm that molluscum contagiosum virus, a molluscipoxvirus that produces small skin tumours in immunocompetent individuals and opportunistic infections in immunodeficient AIDS patients, also encodes a related, larger vIL-18BP (gene MC54L). This protein may contribute to the lack of inflammatory response characteristic of molluscum contagiosum virus lesions. The expression of vIL-18BPs by distinct poxvirus genera that cause local or general viral dissemination, or persistent or acute infections in the host, emphasizes the importance of IL-18 in response to viral infections.
Simian rhesus rotavirus is a unique heterologous (non-lapine) rotavirus strain capable of productive replication and horizontal transmission in rabbits
Authors: Ciarlet Max , Estes Mary K. , Conner Margaret E.
Published: August 2015

Simian rhesus rotavirus (RRV) is the only identified heterologous (non-lapine) rotavirus strain capable of productive replication at a high inoculum dose of virus (>108 p.f.u.) in rabbits. To evaluate whether lower doses of RRV would productively infect rabbits and to obtain an estimate of the 50% infectious dose, rotavirus antibody-free rabbits were inoculated orally with RRV at inoculum doses of 103, 105 or 107 p.f.u. Based on faecal virus antigen or infectious virus shedding, RRV replication was observed with inoculum doses of 107 and 105 p.f.u., but not 103 p.f.u. Horizontal transmission of RRV to one of three mock-inoculated rabbits occurred 4–5 days after onset of virus antigen shedding in RRV-infected rabbits. Rabbits infected at 107 and 105, but not 103, p.f.u. of RRV developed rotavirus-specific immune responses and were completely (100%) protected from lapine ALA rotavirus challenge. These data confirm that RRV can replicate productively and spread horizontally in rabbits. In attempts to elucidate the genetic basis of the unusual replication efficacy of RRV in rabbits, the sequence of the gene encoding the lapine non-structural protein NSP1 was determined. Sequence analysis of the NSP1 of three lapine rotaviruses revealed a high degree of amino acid identity (85–88%) with RRV. Since RRV and lapine strains also share similar VP7s (96–97%) and VP4s (69–70%), RRV might replicate efficiently in rabbits because of the high relatedness of these three gene products, each implicated in host range restriction.
Genetic analysis of the compatibility between polymerase proteins from human and avian strains of influenza A viruses
Authors: Naffakh Nadia , Massin Pascale , Escriou Nicolas , Crescenzo-Chaigne Bernadette , van der Werf Sylvie
Published: August 2015

In order to determine how efficiently the polymerase proteins derived from human and avian influenza A viruses can interact with each other in the context of a mammalian cell, a genetic system that allows the in vivo reconstitution of active ribonucleoproteins was used. The ability to achieve replication of a viral-like reporter RNA in COS-1 cells was examined with heterospecific mixtures of the core proteins (PB1, PB2, PA and NP) from two strains of human viruses (A/Puerto Rico/8/34 and A/Victoria/3/75), two strains of avian viruses (A/Mallard/NY/6750/78 and A/FPV/-Rostock/34), and a strain of avian origin (A/Hong Kong/156/97) that was isolated from the first human case of H5N1 influenza in Hong Kong in 1997. In accordance with published observations on reassortant viruses, PB2 amino acid 627 was identified as a major determinant of the replication efficiency of heterospecific complexes in COS-1 cells. Moreover, the results showed that replication of the viral-like reporter RNA was more efficient when PB2 and NP were both derived from the same avian or human virus or when PB1 was derived from an avian virus, whatever the origin of the other proteins. Furthermore, the PB1 and PB2 proteins from the A/Hong- Kong/156/97 virus exhibited intermediate properties with respect to the corresponding proteins from avian or human influenza viruses, suggesting that some molecular characteristics of PB1 and PB2 proteins might at least partially account for the ability of the A/Hong Kong/156/97 virus to replicate in humans.
Evolutionary characterization of the six internal genes of H5N1 human influenza A virus
Authors: Hiromoto Yasuaki , Yamazaki Yoshinao , Fukushima Tatsunobu , Saito Takehiko , Lindstrom Stephen E. , Omoe Katsuhiko , Nerome Reiko , Lim Wilina , Sugita Shigeo , Nerome Kuniaki
Published: August 2015

The entire nucleotide sequences of all six internal genes of six human H5N1 influenza A viruses isolated in Hong Kong in 1997 were analysed in detail from a phylogenetic point of view and compared with the evolutionary patterns of the haemagglutinin and neuraminidase genes. Despite being isolated within a single year in the same geographical location, human H5N1 viruses were characterized by a variety of amino acid substitutions in the ribonucleoprotein complex [PB2, PB1, PA and nucleoprotein (NP)] as well as the matrix (M) proteins 1 and 2 and nonstructural (NS) proteins 1 and 2. The presence of previously reported amino acid sequences specific for human strains was confirmed in the PB2, PA, NP and M2 proteins. Nucleotide and amino acid sequence identities of the six internal genes of H5N1 viruses examined here were separated into at least two variant groups. In agreement with the above result, phylogenetic trees of the six internal genes of human H5N1 viruses were generally composed of two minor clades. Additionally, variable dendrogram topologies suggested that reassortment among viruses contributed further to the genetic variability of these viruses. As a result, it became clear that human H5N1 viruses are characterized by divergent gene constellations, suggesting the possible occurrence of genetic reassortment between viruses of the two evolutionary lineages.
Effect of cellular changes and onset of humoral immunity on the replication of porcine reproductive and respiratory syndrome virus in the lungs of pigs
Authors: Labarque Geoffrey G. , Nauwynck Hans J. , Van Reeth Kristien , Pensaert Maurice B.
Published: August 2015

Twenty-two 4- to 5-week-old gnotobiotic pigs were intranasally inoculated with 106·0TCID50of porcine reproductive and respiratory syndrome virus (PRRSV) (Lelystad) and euthanized at different time intervals post-inoculation (p.i.). Bronchoalveolar lavage (BAL) cell populations were characterized, together with the pattern of virus replication and appearance of antibodies in the lungs. Total BAL cell numbers increased from 140×106at 5 days p.i. to 948×106at 25 days p.i. and remained at high levels until the end of the experiment. The number of monocytes/macrophages, as identified by monoclonal antibodies 74-22-15 and 41D3, increased two- to fivefold between 9 and 52 days p.i. with a maximum at 25 days p.i. Flow cytometry showed that the population of differentiated macrophages was reduced between 9 and 20 days p.i. and that between the same time interval, both 74-22-15-positive and 41D3-negative cells, presumably monocytes, and 74-22-15- and 41D3-double negative cells, presumably non-phagocytes, entered the alveolar spaces. Virus replication was highest at 7 to 9 days p.i., decreased slowly thereafter and was detected until 40 days p.i. Anti-PRRSV antibodies were detected starting at 9 days p.i. but neutralizing antibodies were only demonstrated in one pig euthanized at 35 days and another at 52 days p.i. The decrease of virus replication in the lungs from 9 days p.i. can be attributed to (i) shortage of susceptible differentiated macrophages, (ii) lack of susceptibility of the newly infiltrated monocytes and (iii) appearance of anti-PRRSV antibodies in the lungs. Neutralizing antibodies may contribute to the clearance of PRRSV from the lungs.
Echovirus infection of rhabdomyosarcoma cells is inhibited by antiserum to the complement control protein CD59
Authors: Goodfellow Ian G. , Powell Robert M. , Ward Trevor , Spiller O. Brad , Almond Jeffrey W. , Evans David J.
Published: August 2015

A number of echoviruses use decay accelerating factor (DAF) as a cellular receptor or attachment protein for cell infection. Binding of echovirus 7 to DAF at the cell surface, but not to soluble DAF in solution, triggers the formation of virus particles exhibiting an altered sedimentation coefficient (‘A’ particles) which are considered indicative of the particle uncoating process. We have previously demonstrated that antibodies to β2-microglobulin block cell infection at a stage prior to ‘A’ particle formation and suggested that this reflects the involvement of β2-microglobulin (or the associated MHC-I) in a virus–receptor complex that forms at the cell surface. We demonstrate here that antiserum to CD59 specifically blocks infection of rhabdomyosarcoma cells by a range of echoviruses, including viruses that bind DAF (e.g. echovirus 7) and those that use currently unidentified receptors other than DAF. The block occurs prior to ‘A’ particle formation and is cell-type specific. The potential role of CD59 as an active member, or passive participant, in the virus–receptor complex is discussed.
Mutational analysis of hepatitis C virus NS3-associated helicase
Authors: Paolini Chantal , Lahm Armin , De Francesco Raffaele , Gallinari Paola
Published: August 2015

Nonstructural protein 3 (NS3) of hepatitis C virus contains a bipartite structure consisting of an N-terminal serine protease and a C-terminal DEXH box helicase. To investigate the roles of individual amino acid residues in the overall mechanism of unwinding, a mutational–functional analysis was performed based on a molecular model of the NS3 helicase domain bound to ssDNA, which has largely been confirmed by a recently published crystal structure of the NS3 helicase–ssDNA complex. Three full-length mutated NS3 proteins containing Tyr(392)Ala, Val(432)Gly and Trp(501)Ala single substitutions, respectively, together with a Tyr(392)Ala/Trp(501)Ala double-substituted protein were expressed in Escherichia coli and purified to homogeneity. All individually mutated forms showed a reduction in duplex unwinding activity, single-stranded polynucleotide binding capacity and polynucleotide-stimulated ATPase activity compared to wild-type, though to different extents. Simultaneous replacement of both Tyr392 and Trp501 with Ala completely abolished all these enzymatic functions. On the other hand, the introduced amino acid substitutions had no influence on NS3 intrinsic ATPase activity and proteolytic efficiency. The results obtained with Trp(501)Ala and Val(432)Gly single-substituted enzymes are in agreement with a recently proposed model for NS3 unwinding activity. The mutant phenotype of the Tyr(392)Ala and Tyr(392)Ala/Trp(501)Ala enzymes, however, represents a completely novel finding.
Dengue virus type 1 DNA vaccine induces protective immune responses in rhesus macaques
Authors: Raviprakash Kanakatte , Porter Kevin R. , Kochel Tadeuscz J. , Ewing Daniel , Simmons Monica , Phillips Irving , Murphy Gerald S. , Weiss Walter R. , Hayes Curtis G.
Published: August 2015

A candidate DNA vaccine expressing dengue virus type 1 pre-membrane and envelope proteins was used to immunize rhesus macaques. Monkeys were immunized intramuscularly (i.m.) or intradermally (i.d.) by three or four 1 mg doses of vaccine, respectively. Monkeys that were inoculated i.m. seroconverted more quickly and had higher antibody levels than those that were inoculated i.d. The sera exhibited virus-neutralizing activity, which declined over time. Four of the eight i.m.-inoculated monkeys were protected completely from developing viraemia when challenged 4 months after the last dose with homologous dengue virus. The other four monkeys had reduced viraemia compared with the control immunized monkeys. The i.d.-inoculated monkeys showed no reduction in viraemia when challenged with the virus. All vaccinated monkeys showed an anamnestic antibody response, indicating that they had established immunological memory. Vaccine-induced antibody had an avidity index similar to that of antibody induced by virus infection; however, no clear correlation was apparent between antibody avidity and virus neutralization titres.
Expression of reporter genes from the defective RNA CD-61 of the coronavirus infectious bronchitis virus
Authors: Stirrups Kathleen , Shaw Kathleen , Evans Sharon , Dalton Kevin , Casais Rosa , Cavanagh David , Britton Paul
Published: August 2015

The defective RNA (D-RNA) CD-61, derived from the Beaudette strain of the avian coronavirus infectious bronchitis virus (IBV), was used as an RNA vector for the expression of two reporter genes, luciferase and chloramphenicol acetyltransferase (CAT). D-RNAs expressing the CAT gene were demonstrated to be capable of producing CAT protein in a helper-dependent expression system to about 1·6 μg per 106 cells. The reporter genes were expressed from two different sites within the CD-61 sequence and expression was not affected by interruption of the CD-61-specific ORF. Expression of the reporter genes was under the control of a transcription-associated sequence (TAS) derived from the Beaudette gene 5, normally used for the transcription of IBV subgenomic mRNA 5. The Beaudette gene 5 TAS is composed of two tandem repeats of the IBV canonical consensus sequence involved in the acquisition of a leader sequence during the discontinuous transcription of IBV subgenomic mRNAs. It is demonstrated that only one canonical sequence is required for expression of mRNA 5 or for the expression of an mRNA from a D-RNA and that either sequence can function as an acceptor site for acquisition of the leader sequence.
Replication-competent foot-and-mouth disease virus RNAs lacking capsid coding sequences
Authors: McInerney Gerald M. , King Andrew M. Q. , Ross-Smith Natalie , Belsham Graham J.
Published: August 2015

RNA transcripts were prepared from plasmids encoding an infectious cDNA of foot-and-mouth disease virus (FMDV) or derivatives in which the leader (Lab and Lb) and capsid protein coding sequences were deleted or replaced by sequences encoding chloramphenicol acetyltransferase (CAT). The transcripts were electroporated into BHK cells and the expression of CAT and the FMDV 3C protease was monitored. Detection of CAT and 3C was dependent on the ability of the transcript to replicate. All of the Lb coding sequence and 94% of P1 (the capsid protein precursor) coding sequence could be deleted without any apparent effect on the ability of the RNA to replicate. Thus, no cis-acting replication element is present within this region of the FMDV genome. Trans-encapsidation of these FMDV replicons was very inefficient, which may explain the lack of production of defective-interfering particles in FMDV-infected cells.
Genetic analysis of wild-type Dobrava hantavirus in Slovenia: co-existence of two distinct genetic lineages within the same natural focus
Authors: Avsic-Zupanc Tatjana , Nemirov Kirill , Petrovec Miro , Trilar Tomi , Poljak Mario , Vaheri Antti , Plyusnin Alexander
Published: August 2015

Genetic analysis was performed of wild-type (wt) Dobrava hantavirus (DOB) strains from Slovenia, the country where the virus was first discovered and where it was found to cause haemorrhagic fever with renal syndrome (HFRS), with a fatality rate of 12%. Two hundred and sixty mice of the genus Apodemus, trapped in five natural foci of DOB-associated HFRS during 1990–1996, were screened for the presence of anti-hantavirus antibodies and 49 Apodemus flavicollis and four Apodemus agrarius were found to be positive. RT–PCR was used to recover partial sequences of the wt-DOB medium (M) and small (S) genome segments from nine A. flavicollis and one A. agrarius. Sequence comparison and phylogenetic analysis of the Slovenian wt-DOB strains revealed close relatedness of all A. flavicollis-derived virus sequences (nucleotide diversity up to 6% for the M segment and 5% for the S segment) and the geographical clustering of genetic variants. In contrast, the strain harboured by A. agrarius showed a high level of genetic diversity from other Slovenian DOB strains (14%) and clustered together on phylogenetic trees with other DOB strains harboured by A. agrarius from Russia, Estonia and Slovakia. These findings suggest that the DOB variants carried by the two species of Apodemus in Europerepresent two distinct genetic lineages.
Neither phosphorylation nor the amino-terminal part of rabies virus phosphoprotein is required for its oligomerization
Authors: Gigant Benoit , Iseni Frédéric , Gaudin Yves , Knossow Marcel , Blondel Danielle
Published: August 2015

Rabies virus (PV strain) phosphoprotein (P) was expressed in bacteria. This recombinant protein binds specifically to the nucleoprotein–RNA complex purified from infected cells. Chemical cross-linking and gel-filtration studies indicated that the P protein forms oligomers. Analytical centrifugation data demonstrated the co-existence of monomeric and oligomeric forms of rabies virus P protein and suggested that there is an equilibrium between these species. As P expressed in bacteria is not phosphorylated, this result indicates that P phosphorylation is not required for its oligomerization. Although an alignment of several rhabdovirus P sequences revealed that the amino-terminal domain of P has a conserved predicted propensity to form helical coiled coils, an amino-terminally truncated form of P protein, lacking the first 52 residues, was also shown to be oligomeric. Therefore, the amino-terminal domain of rabies virus P is not necessary for its oligomerization.
The role of the UL41 gene of herpes simplex virus type 1 in evasion of non-specific host defence mechanisms during primary infection
Authors: Suzutani Tatsuo , Nagamine Masayoshi , Shibaki Taiichiro , Ogasawara Masahiro , Yoshida Itsuro , Daikoku Toru , Nishiyama Yukihiro , Azuma Masanobu
Published: August 2015

The UL41 gene product (vhs) of herpes simplex virus (HSV) is packaged in the virion, and mediates host protein synthesis shutoff at the early stage of the virus replication cycle. In order to clarify the role of vhs in virus replication and virulence, we isolated a completely UL41-deficient mutant (the VRΔ41 strain) and its revertant (the VRΔ41R strain). In the mouse encephalitis model, the replication of strain VRΔ41 was inhibited after 2 days post-infection, resulting in low virulence, by γ-ray-sensitive cells such as lymphocytes and/or neutrophils. The result suggested that some cytokines, produced in VRΔ41-inoculated brains, activate and induce the migration of γ-ray-sensitive cells to the infection site. Therefore, cytokines produced by HSV-1-infected human cells were screened, and potent inductions of interleukin (IL)-1β, IL-8 and macrophage inflammatory protein-1α by VRΔ41 infection were observed. Moreover, the VRΔ41 strain showed 20- and 5-fold higher sensitivity to interferon-α and -β compared to the wild-type strain, respectively. These results indicate that one important role of vhsin vivois evasion from non-specific host defence mechanisms during primary infection through suppression of cytokine production in HSV-infected cells and reduction of the anti-HSV activity of interferon-α and -β.
Differential recognition of ORF2 protein from type 1 and type 2 porcine circoviruses and identification of immunorelevant epitopes
Authors: Mahé Dominique , Blanchard Philippe , Truong Catherine , Arnauld Claire , Le Cann Pierre , Cariolet Roland , Madec François , Albina Emmanuel , Jestin André
Published: August 2015

Two types of porcine circovirus (PCV) have been isolated and are referred to as PCV1 and PCV2. PCV1 represents an apathogenic virus, whereas PCV2 is associated with post-weaning multisystemic wasting syndrome. The two PCVs are related, since they display about 70% identity based on nucleotide sequences. In order to discriminate between common and type-specific antigens, an immunocytological approach was used following transfections with cloned circovirus DNAs, as well as recombinant proteins expressed by either baculovirus or plasmid vectors. The ORF1-encoded proteins in the two viruses were shown to be antigenically related, whereas the ORF2 proteins were recognized differentially by polyclonal anti-PCV2 antibodies. Furthermore, PEPSCAN analysis performed on overlapping fragments of the genes encoding part of ORF1 and the entire ORF2 and ORF3 led to the identification of five dominant immunoreactive areas, one located on ORF1 and four on ORF2. However, only some ORF2 peptides proved to be immunorelevant epitopes for virus type discrimination. The potential use of ORF2-derived antigens as diagnostic tools is demonstrated.
Potato leafroll virus protein P1 contains a serine proteinase domain
Authors: Li X. , Ryan M. D. , Lamb J. W.
Published: August 2015

The multi-domain potato leafroll virus replicase protein P1 was expressed in insect cells from the polyhedrin promoter of Autographa californica nucleopolyhedrovirus. Using antisera raised against P1, it was shown that P1 was cleaved near the VPg in insect cells in a manner similar to that in plant cells, to produce a ∼27 kDa C-terminal fragment. Furthermore, it was shown that the proposed serine proteinase-like domain within P1 is responsible for this processing and that this can occur in a trans (intermolecular) reaction. Four conserved residues within the serine proteinase domain that are essential for catalysis have been identified, consistent with the proposal that this domain comprises a serine proteinase.
Sugarcane yellow leaf virus: a novel member of the Luteoviridae that probably arose by inter-species recombination
Authors: Smith Grant R. , Borg Zara , Lockhart Ben E. L. , Braithwaite Kathryn S. , Gibbs Mark J.
Published: August 2015

The 5895 nucleotide long single-stranded RNA genome of Sugarcane yellow leaf virus Florida isolate (SCYLV-F) includes six major ORFs. All but the first of these are homologous to genes of known function encoded by viruses of the three newly defined genera in the Luteoviridae (‘luteovirids’), i.e. poleroviruses, luccccteoviruses and the enamoviruses. SCYLV-F ORFs 1 and 2 are most closely related to their polerovirus counterparts, whereas SCYLV-F ORFs 3 and 4 are most closely related to counterparts in luteovirus genomes, and SCYLV-F ORF5 is most closely related to the read-through protein gene of the only known enamovirus. These differences in affinity result from inter-species recombination. Two recombination sites in the genome of SCYLV-F map to the same genomic locations as previously described recombinations involving other luteovirids. A fourth type of luteovirid, Soybean dwarf virus, has already been described. Our analyses indicate that SCYLV-F represents a distinct fifth type.
The long terminal repeat is a determinant of cell tropism of maedi-visna virus
Authors: Agnarsdóttir Gudrún , Thorsteinsdóttir Holmfrídur , óskarsson Thórdur , Matthíasdóttir Sigrídur , St. Haflidadóttir Benedikta , Andrésson ólafur S. , Andrésdóttir Valgerdur
Published: August 2015

Maedi-visna virus (MVV) is a lentivirus of sheep, mainly affecting the lungs and the central nervous system. Long terminal repeat (LTR) sequence variability is common in tissue culture-derived isolates of MVV as well as those of other lentiviruses. The role of this sequence variation in MVV replication has not been explored. PCR amplification of the LTRs of an MVV isolate revealed two product sizes, the larger containing a 53 bp duplication. PCR products containing the two size variants of the LTRs were cloned into an infectious molecular clone of MVV and the resulting chimeric viruses were tested for growth in various cell types. The chimeric virus containing only one copy of the 53 bp sequence was found to grow more slowly in sheep choroid plexus cells, sheep fibroblasts and sheep synovial cells than the virus with the 53 bp duplication. Both viruses grew equally well in macrophages. These results indicate that the LTRs determined the extended cell tropism of MVV.
Isolation of Hendra virus from pteropid bats: a natural reservoir of Hendra virus
Authors: Halpin K. , Young P. L. , Field H. E. , Mackenzie J. S.
Published: August 2015

Since it was first described in Australia in 1994, Hendra virus (HeV) has caused two outbreaks of fatal disease in horses and humans, and an isolated fatal horse case. Our preliminary studies revealed a high prevalence of neutralizing antibodies to HeV in bats of the genusPteropus, but it was unclear whether this was due to infection with HeV or a related virus. We developed the hypothesis that HeV excretion from bats might be related to the birthing process and we targeted the reproductive tract for virus isolation. Three virus isolates were obtained from the uterine fluid and a pool of foetal lung and liver from one grey-headed flying-fox (Pteropus poliocephalus), and from the foetal lung of one black flying-fox (P. alecto). Antigenically, these isolates appeared to be closely related to HeV, returning positive results on immunofluorescent antibody staining and constant-serum varying-virus neutralization tests. Using an HeV-specific oligonucleotide primer pair, genomic sequences of the isolates were amplified. Sequencing of 200 nucleotides in the matrix gene identified that these three isolates were identical to HeV. Isolations were confirmed after RNA extracted from original material was positive for HeV RNA when screened on an HeV Taqman assay. The isolation of HeV from pteropid bats corroborates our earlier serological and epidemiological evidence that they are a natural reservoir host of the virus.