Emendation of the Genus Auritidibacter Yassin et al. 2011 and Auritidibacter ignavus Yassin et al. 2011 based on features observed from Canadian and Swiss clinical isolates and whole-genome sequencing analysis

Auritidibacter ignavus is a Gram-stain-positive bacillus derived from otorrhea. Four strains derived from ear discharges in Canada and Switzerland, with features consistent with but distinguishable from Auritidibacter ignavus IMMIB L-1656^T (accession number FN554542) by 16S rRNA gene sequencing (97.5 % similarity), were thought to represent a novel species of the genus Auritidibacter. Auritidibacter ignavus DSM 45359^T (=IMMIB L-1656^T) was acquired to compare with Canadian and Swiss strains by whole-genome sequencing (WGS). Unexpectedly, those isolates were observed to be consistent with A. ignavus DSM 45359^T by WGS (ANIb scores >98 %), MALDI-TOF (Bruker), cellular fatty acid analysis and biochemically (some differences were observed). A nearly full 16S rRNA gene sequence could not be readily prepared from A. ignavus DSM 45359^T, even after multiple attempts. A 16S rRNA gene chimeric consensus sequence created from the genome assembly of A. ignavus DSM 45359^T had only 97.5 % similarity to that of A. ignavus IMMIB L-1656^T, implying that 16S rRNA sequence accession number FN554542 could not be replicated. We concluded that our isolates of members of the genus Auritidibacter were consistent with A. ignavus DSM 45359^T, did not represent a novel species, and that the sequence corresponding to FN554542 was not reproducible. By WGS, A. ignavus DSM 45359^T had genome of 2.53×10⁶ bp with a DNA G+C content of 59.34%, while genomes of Canadian and Swiss isolates ranged from 2.47 to 2.59×10⁶ bp with DNA G+C contents of 59.3-59.52 %. A. ignavus NML 100628 (=NCTC 14178=LMG 30897) did not demonstrate a rodcoccus cycle. Emendation of Auritidibacter ignavus was proposed based on these results.

Hepatitis B Virus Genotype G forms core-like particles with unique structural properties

We have determined the structure of the core capsid of an unusual variant of hepatitis B virus, genotype G (HBV/G) at 14Å resolution, using cryo-electron microscopy. The structure reveals surface features not present in the prototype HBV/A genotype. HBV/G is novel in that it has a unique 36-bp insertion downstream of the core gene start codon. This results in a twelve amino acid insertion at the N-terminal end of the core protein, and two stop codons in the precore region that prevent the expression of HBeAg. HBV/G replication in patients is associated with co-infection with another genotype of HBV, suggesting that HBV/G may have reduced replication efficiency in vivo. We localized the N-terminal insertion in HBV/G and show that it forms two additional masses on the core surface adjacent to each of the dimer-spikes and have modelled the structure of the additional residues within this density. We show that the position of the insertion would not interfere with translocation of nucleic acids through the pores to the core interior compartment. However, the insertion may partially obscure several residues on the core surface that are known to play a role in envelopment and secretion of virions, or that could affect structural rearrangements that may trigger envelopment after DNA second-strand synthesis.

Molecular analysis and implications of neurovirulent circulating vaccine-derived poliovirus in Jamaica. A case report and review of literature

As the goal to eradicate wild polio virus (WPV) is approached, outbreaks associated with vaccine derived polioviruses (VDPV) with neurovirulent properties have emerged. The relevance for the spread of infection by nonparalytic cVDPV cases, with mutations associated with neurovirulence, is discussed with reference to the molecular analysis of a VDPV isolated from a Jamaican child who presented with aseptic meningitis. Potential risks to the Jamaican community resulting from circulation of cVDPV and critical factors defined by the World Health Organization (WHO) in the global eradication of Polio are analyzed in the context of immunization coverage, and the need to stop all Oral Polio Vaccine (OPV) use once wild polioviruses (WPVs) have been eradicated.

First detection and confirmation of spring viraemia of carp virus in common carp, Cyprinus carpio L., from Hamilton Harbour, Lake Ontario, Canada

In June 2006, 150 wild common carp were sampled from Hamilton Harbour, Lake Ontario, Canada. Tissue pools consisting of kidney, spleen and encephalon were screened for viruses as a condition facilitating the export of live carp to France. Cytopathic effect (CPE), indicative of a viral infection, became evident after 8 days of incubation at 15 degrees C. Eighteen of 30 tissue pools (five fish per pool) eventually demonstrated viral CPE. The viral pathogen was initially cultured and isolated on the epithelioma papulosum cyprini cell line and subsequently shown to produce CPE in the fathead minnow and bluegill fin cell lines. Electron microscopy demonstrated the virus to be a rhabdovirus. Reverse transcriptase-polymerase chain reaction assay and nucleotide sequence analysis identified the isolate as spring viraemia of carp virus (SVCV). Phylogenetic analysis of a 533 bp region of the glycoprotein gene grouped the Canadian isolate in SVCV genogroup Ia together with isolates from Asia and the USA. Sequence comparisons revealed the Hamilton Harbour, Lake Ontario isolate to be most similar to an isolate obtained from common carp in the Calumet Sag Channel in Illinois in 2003 (98.9% nucleotide identity). This is the first report of the detection of SVCV in Canada.

Helicobacter winghamensis sp. nov., a novel Helicobacter sp. isolated from patients with gastroenteritis

From 1997 to 1999 seven isolates of Campylobacter-like organisms from five patients that were exhibiting symptoms of gastroenteritis, including fever, stomach malaise, and diarrhea, were investigated. The organisms were isolated from stool samples and found to exhibit a diverse colony morphology; hence multiple isolates were submitted from one of the patients. All isolates were found to be identical. The organisms were catalase, urease, alkaline phosphatase, and nitrate negative but oxidase and indoxyl acetate positive. They grew at 37 degrees C but not at 42 degrees C, and three of the isolates from two different patients were sensitive to nalidixic acid and cephalothin. Full 16S rRNA sequence analysis not only grouped these organisms within the Helicobacter genus but also differentiated them from previously identified Helicobacter species. The closest relative by phylogenetic analysis was Helicobacter sp. flexispira taxon 1. Electron microscopy showed that these isolates had one or two bipolar flagella; however, the periplasmic fibers, a characteristic of the known Helicobacter sp. flexispira taxa, were not observed. The present isolates also lacked a flagellar sheath, a trait shared with four other Helicobacter spp., H. canadensis, H. mesocricetorum, H. pullorum, and H. rodentium. On the basis of the unique phenotypic properties of these isolates and 16S rRNA sequence analysis, we propose the classification of a new Helicobacter species, Helicobacter winghamensis sp. nov.

Incursion of bluetongue virus into the Okanagan Valley, British Columbia

Bluetongue virus was isolated from a sentinel herd in British Columbia. Virus isolation was by intravenous inoculation of embryonated chicken eggs and subculture in BHK-21 cells. The cytopathic agent was identified as bluetongue virus by electron microscopy and the immunoperoxidase test. The serotype was identified as serotype 11 by virus neutralization.

Three-dimensional structure of Aleutian mink disease parvovirus: implications for disease pathogenicity

The three-dimensional structure of expressed VP2 capsids of Aleutian mink disease parvovirus strain G (ADVG-VP2) has been determined to 22 A resolution by cryo-electron microscopy and image reconstruction techniques. A structure-based sequence alignment of the VP2 capsid protein of canine parvovirus (CPV) provided a means to construct an atomic model of the ADVG-VP2 capsid. The ADVG-VP2 reconstruction reveals a capsid structure with a mean external radius of 128 A and several surface features similar to those found in human parvovirus B19 (B19), CPV, feline panleukopenia virus (FPV), and minute virus of mice (MVM). Dimple-like depressions occur at the icosahedral twofold axes, canyon-like regions encircle the fivefold axes, and spike-like protrusions decorate the threefold axes. These spikes are not present in B19, and they are more prominent in ADV compared to the other parvoviruses owing to the presence of loop insertions which create mounds near the threefold axes. Cylindrical channels along the fivefold axes of CPV, FPV, and MVM, which are surrounded by five symmetry-related beta-ribbons, are closed in ADVG-VP2 and B19. Immunoreactive peptides made from segments of the ADVG-VP2 capsid protein map to residues in the mound structures. In vitro tissue tropism and in vivo pathogenic properties of ADV map to residues at the threefold axes and to the wall of the dimples.

The structure of a cypovirus and the functional organization of dsRNA viruses

Cytoplasmic polyhedrosis virus (CPV) is unique among the double-stranded RNA viruses of the family Reoviridae in having a single capsid layer. Analysis by cryo-electron microscopy allows comparison of the single shelled CPV and orthoreovirus with the high resolution crystal structure of the inner shell of the bluetongue virus (BTV) core. This suggests that the novel arrangement identified in BTV, of 120 protein subunits in a so-called 'T=2' organization, is a characteristic of the Reoviridae and allows us to delineate structural similarities and differences between two subgroups of the family--the turreted and the smooth-core viruses. This in turn suggests a coherent picture of the structural organization of many dsRNA viruses.

Lipofectin increases the specific activity of cypovirus particles for cultured insect cells

Cytoplasmic polyhedrosis viruses (CPV) are classified as 14 distinct species (electropherotypes) within the genus Cypovirus, family Reoviridae. Cypovirus research has been limited by a lack of appropriate cell culture systems (for each of these virus species) in which the majority of cells can become productively infected. Lipofection increased the infection rate of Lymantria dispar 652 cells, by virus particles (derived from polyhedra) of Orgyia pseudosugata type 5 cypovirus (Op-5 CPV), from 3 to 44%. Lipofection also significantly increased the percentage of Trichoplusia ni 368 cells infected with the same virus (from < 1 to approximately 7%). The spread of cypovirus infection between cells was either very slow or insignificant, and infected cells appeared to remain viable for long periods. Virus infection was detected by the observation of polyhedra formation in individual cells and it was therefore possible to develop a simple quantitative assay system to measure virus titre (TCID50). Cryo-electron microscopy showed that cypovirus particles formed a complex with the lipid, involving their envelopment within the liposome membrane. It was concluded that the increased infectivity of the virus by lipofection was due to a more efficient cell entry mechanism, probably involving fusion between liposome and cell membranes.

Disruption of lysosomal targeting is associated with insecticidal potency of juvenile hormone esterase

Juvenile hormone esterase (JHE; EC 3.1.1.1), which is intrinsically involved in regulation of development of some insect larvae, is rapidly removed from the hemolymph by the pericardial cells. Lys-29 and Lys-524, which are implicated in the degradation of JHE, were mutated to Arg. Neither the half-life of the modified JHE in the hemolymph nor the catalytic parameters were changed significantly, but when combined, these mutations resulted in apparent failure of lysosomal targeting in the pericardial cell complex. A hypothesis for the mechanism of reduced efficiency of lysosomal targeting is presented. Infection of larvae with a recombinant baculovirus expressing the modified JHE resulted in a 50% reduction in feeding damage compared with larvae infected with the wild-type virus, thus demonstrating improved properties as a biological insecticide. These data demonstrate that alteration of specific residues of JHE that disrupted lysosomal targeting, dramatically increased the insecticidal activity of this protein.

Mechanistic studies of the degradation of juvenile hormone esterase in Manduca sexta

The mechanisms of degradation of juvenile hormone esterase (JHE) were investigated in larvae of the tobacco hornworm, Manduca sexta. JHE is removed from the hemolymph by the pericardial cells by receptor-mediated endocytosis and is ultimately degraded in the lysosomes. Immunoprecipitation experiments and native PAGE followed by Western blotting showed that JHE associates with a putative heat shock cognate protein (Hsp). Approximately 25% of the active JHE in the pericardial cell complex is associated with the putative Hsp 1 h postinjection of affinity purified JHE. Electron microscope analysis revealed that the putative Hsp is located in the trans-Golgi network of pericardial cells, where it is hypothesized to be involved in sorting of proteins destined for the lysosomes, from those destined for the cell membrane. Data acquired from immunoprecipitation and Western blotting experiments argue against the involvement of ubiquitin in the degradation of JHE. Injection of radiolabeled JHE into larvae of M. sexta followed by SDS-PAGE of pericardial cell homogenates revealed covalent binding of an unidentified protein to JHE in the pericardial cell complex.

Structure of correctly self-assembled bluetongue virus-like particles

Bluetongue virus-like particles (VLPs), synthesized by coexpression of VP2, VP3, VP5, and VP7 using recombinant baculoviruses, have been examined by cryoelectron microscopy and image analysis. The 3-D reconstruction of these VLPs reveals an icosahedral structure 86 nm in diameter with essentially the same features as for the native Bluetongue virus (BTV) particle. The VLP is thus shown to contain the four constituent proteins as the native virus particle, with each of the protein positions highly occupied. Since the BTV core-like particle formed by coexpression of VP3 and VP7 lacks five VP7 trimers around each of the five-fold axes, it appears that the presence of the outer capsid proteins VP2 and VP5 is necessary for the adhesion of these VP7 trimers around the five-fold axes. The observed spontaneous formation of complete VLP in the absence of the BTV nonstructural proteins implies that the nonstructural proteins are not necessary for the formation of the double-shelled viral capsid. However, the nonstructural proteins may be involved in different aspects of genome replication and packaging.

Morphogenic capabilities of human immunodeficiency virus type 1 gag and gag-pol proteins in insect cells

To determine the interaction between the gag precursor and the viral protease and to confirm the role of gag precursor in formation of human immunodeficiency virus type 1 particles, the gag and protease encoding regions of a proviral genome with mutations at the site between p17 and p24 or p24 and p15 were expressed by recombinant baculoviruses under the transcriptional control of the strong polyhedrin promoter. Western blot analyses of the expressed products of p17-p24 mutated viruses revealed that both 41- and 55-kDa proteins were synthesized. However, free p24, p17, and the other smaller cleavage products (p9, p6) could not be detected in infected insect cells. The second recombinant virus (p24-p15) synthesized not only a 55k-Da protein, but also a number of smaller products including a 40k-Da protein, p24, and p17. Examination of the insect cells infected by either of these two recombinant viruses by electron microscopy failed to detect any gag particle formation, although some irregular membrane protrusions and profound distortions of the cell surface were clearly visible in the cells infected with recombinant mutant p17-p24 virus, but not with recombinant p24-p15 mutants. To investigate the morphogenic capability of the gag-pol fusion protein, a mutant gag-pol gene containing an inactive protease as well as a modified gag-pol gene lacking the frameshifting activity were expressed in insect cells. While the inactive protease mutant was capable of forming immature particles that were secreted, the frameshifting mutant synthesized only an aberrant form of gag particles with a large radius of curvature in lieu of spherical particles. However, when this mutant was expressed in insect cells in the presence of a truncated gag protein with M(r) of 46 kDa (lacking only the p6 domain), normal immature particles containing both antigens were formed.

Interactions between bluetongue virus core and capsid proteins translated in vitro

To determine whether the two major core proteins (VP3 and VP7) of bluetongue virus can interact in vitro to form morphological structures, linearized VP3 and VP7 cDNA clones were transcribed using SP6 polymerase and the resultant transcripts were co-translated using rabbit reticulocyte lysates. The structures derived were isolated by sedimentation through a sucrose gradient and found to resemble VP3-VP7 core-like particles (CLPs) expressed in vivo. Reacting CLPs synthesized in vivo with outer capsid proteins translated in vitro (VP2 or VP5) indicated that each outer capsid protein has the capacity to bind to a preformed CLP. This was confirmed by in vivo expression of the appropriate genes using baculovirus vectors. The interaction of VP2 or VP5 with the CLP was analysed by electron microscopy and by using immunogold-labelled monoclonal antibody.

Structure of bluetongue virus particles by cryoelectron microscopy

The structure of the bluetongue virus (BTV) particle, determined by cryoelectron microscopy and image analysis, reveals a well-ordered outer shell which differs markedly from other known Reoviridae. The inner shell is known to have an icosahedral structure with 260 triangular spikes of VP7 trimers arranged on a T = 13,l lattice. The outer shell is seen to consist of 120 globular regions (possibly VP5), which sit neatly on each of the six-membered rings of VP7 trimers. "Sail"-shaped spikes located above 180 of the VP7 trimers form 60 triskelion-type motifs which cover all but 20 of the VP7 trimers. These spikes are possibly the hemagglutinating protein VP2 which contains a virus neutralization epitope. Thus, VP2 and VP5 together form a continuous layer around the inner shell except for holes on the 5-fold axis.

Three-dimensional reconstruction of baculovirus expressed bluetongue virus core-like particles by cryo-electron microscopy

When the viral proteins VP3 and VP7 of bluetongue virus (BTV) are expressed simultaneously in the baculovirus system, core-like particles form spontaneously. The 3-D structure of these core-like particles, determined from cryo-electron micrographs, reveals an icosahedral structure 72.5 nm in diameter with 200 triangular spikes arranged on a T = 13,I lattice; The five spikes around each of the fivefold axes are absent. This is in contrast to the native BTV core particles which have a complete T = 13,I lattice of 260 spikes. The spikes, attributed to VP7 trimers appear as triangular columns 8.0 nm in height with distinct inner and outer domains. The inner shell of the core-like particles, or subcore-like particle, has a T = 1 lattice composed of 60 copies of VP3. The subcore-like particle is noticeably thicker around the fivefold positions. Pores in the subcore-like particle are situated near each of the local sixfold axes, below each six-membered ring of spikes. These pores could allow the passage of metabolites and RNA to and from the core for RNA transcription during infection. It is possible that the synthetic core-like particles have an incomplete complement of VP7 spikes because the ratio of VP7 to VP3 produced in the dual expression system is less than the 13:1 required for complete core-like particles. Only the VP7 spikes which have the strongest affinity for the VP3 inner core and are involved in maintaining the structural integrity of the core-like particle are incorporated. The BTV core-like particle shows greater morphological similarity to the rotavirus than to the reovirus core particle.

3-D reconstruction of bluetongue virus tubules using cryoelectron microscopy

Bluetongue virus (BTV) forms tubules in infected mammalian cells. These tubules are virally encoded entities which can be formed with only one protein, NS1. The NS1 protein does not form a part of virus particles, and its function in viral infection is uncertain. Expression of the NS1 gene in insect cells by recombinant baculovirus yields high amounts of NS1 tubules (ca. 50% of cellular proteins) which are morphologically and immunologically similar to authentic BTV NS1 and can be isolated to about 90% purity. The structure of these synthetic NS1 tubules was investigated by cryoelectron microscopy. NS1 tubules are on average 52.3 nm in diameter and up to 100 nm long. The structure of their helical surface lattice has been determined using computer image processing to a resolution of 40 A. The NS1 protein is about 5.3 nm in diameter and forms a dimer-like structure, so that the tubules are composed of helically coiled ribbons of NS1 "dimers," with 21 or 22 dimers per turn. The surface lattice displays P2 symmetry and forms a one-start helix with a pitch of 9.1 nm. The NS1 tubules exist in two slightly different pH-dependent conformational states.

Localization of juvenile hormone esterase during development in normal and in recombinant baculovirus-infected larvae of the moth Trichoplusia ni

The pathogenesis and cellular localization of juvenile hormone esterase (JHE) was examined in larvae of the moth Trichoplusia ni, infected with a recombinant baculovirus (Autographa californica nuclear polyhedrosis virus: AcNPV) engineered to produce high levels of JHE (JHE virus). The course of JHE localization in the recombinant virus infected larvae was compared with that of both wild type AcNPV infected, and uninfected larvae, using immunogold electron microscopy. In the JHE virus infected insects, high levels of JHE were observed in the endoplasmic reticulum of all cells showing evidence of viral structures in the nucleus, except for gut cells which showed only background JHE levels. Tracheole cells and haemocytes appeared to play a role in the dissemination of infection. In uninfected larvae, fat body and epidermis were the major tissues staining for JHE, which was only detectable at peak times of JHE activity during the fifth instar: lower levels at other times could not be distinguished from background. JHE was also present in lysosomes of granular haemocytes: these lysosomes increased in number in the fifth instar compared to the fourth instar. Similar lysosome-like granules in the pericardial cells did not become highly positive for JHE antigen until the fifth instar.

Structure and morphogenesis of Dugbe virus (Bunyaviridae, Nairovirus) studied by immunogold electron microscopy of ultrathin cryosections

We have studied the structure and morphogenesis of Dugbe (DUG) virus (Bunyaviridae, Nairovirus) in cultured porcine kidney (PS) cells and a tick cell line (Ra 243) using immunogold electron microscopy. DUG virus is a tickborne arbovirus, considered to be a low health hazard, that is antigenically and genetically related to Crimean Congo haemorrhagic fever (CCHF) virus (Marriott et al., 1990). We have investigated the maturation and intracellular transport of DUG virus particles as a model for other more pathogenic nairoviruses using monoclonal antibodies for immunogold labelling of ultrathin cryosections and immunofluorescence techniques. The spherical DUG virus particle measures about 90 nm in diameter, with a 5 nm thick membrane covered by 5-7 nm long projections or "spikes". These projections form hollow cylindrical morphological units, about 5 nm in diameter. DUG virus infection caused only a slight cytopathogenic effect in mammalian cells and none in tick cells. DUG virus particles assembled by budding from the Golgi complex, where the DUG virus glycoprotein G1 accumulated in vesicles originating from Golgi cisternae. The nucleocapsid protein N accumulated in scattered foci throughout the cytoplasm, and this appears to be related to the limited maturation of DUG virus particles that occurred. The reduced number of budding virus particles observed in tick cells was correlated with the reduced cytopathology observed.

Analyses of the requirements for the synthesis of virus-like particles by feline immunodeficiency virus gag using baculovirus vectors

Feline immunodeficiency virus (FIV) gag gene was expressed in baculovirus vectors to investigate its potential for the assembly of virus-like particles. The unprocessed 50-kDa FIV gag precursor made in infected insect cells by recombinant AcFIVGAG-1 was myristoylated, assembled at the cell surface into virus-like particles (with diameters of approximately 100 nm), and efficiently released into the culture supernatant fluids. The presence of the complete viral-coded protease component of the FIV pol gene engineered into a second expression vector (AcFIVGAG-P5) resulted in the efficient processing of the gag precursor to its component proteins and abolished particle formation and secretion. Insertion of a stop codon in this vector upstream of the putative gag-pol frameshift site (GGGAAAC) resulted in the derivation of an expression vector (AcFIVGAG-R) that made a truncated, unprocessed 46-kDa FIV gag precursor lacking some 34 amino acids in the p10 carboxy-proximal coding region of gag. This vector synthesized tubular structures in the cytoplasm of infected cells and released them into the cell supernatant. The results demonstrate that the FIV gag precursor can spontaneously assemble into virus-like particles without any other virus proteins and that the carboxy-terminal part of the precursor gag protein is essential for such assembly.

Dissemination, replication, and trans-stadial persistence of Dugbe virus (Nairovirus, Bunyaviridae) in the tick vector Amblyomma variegatum

The dissemination and replication of Dugbe (DUG) virus and its tissue tropisms in the tick vector Amblyomma variegatum were examined by immunohistochemical analysis using specific antibody, in situ hybridization with a viral-complementary riboprobe, and infectivity assays of dissected tissues. Dugbe virus was localized in both unfed and feeding adults inoculated as nymphs or orally infected by capillary feeding, and in nymphs infected by capillary feeding. In non-feeding ticks, the main sites of DUG virus replication were the epidermis, hemocytes associated with loose connective tissue, and a small number of phagocytic digestive cells in the gut lumen. Virus infectivity in the hemolymph was associated entirely with hemocytes. Dugbe viral antigen or infectivity was not detected in the salivary glands until after the start of feeding. Viral titers in the salivary glands of feeding ticks were about ten-fold higher than in gut, ovary, or loose connective tissue. The level of infection decreased during molting and increased during feeding. Viral particles and pathologic effects were not detected in infected ticks. The primary site of trans-stadial persistence of DUG virus is the hemocytes. Tick hemocytes and other motile cells may be important in the transmission of persistent virus infection from one cell or organ to another by diapedesis.

Detection of an arbovirus in an invertebrate and a vertebrate host using the polymerase chain reaction

The ability of the polymerase chain reaction (PCR) to diagnose an arboviral infection in an arthropod vector or a mammalian host was examined. Dugbe (DUG) viral RNA was detected in RNA extracts from infected tissue samples by reverse transcription and enzymatic amplification of the resulting cDNA using Taq DNA polymerase, followed by characterisation of the amplified product by agarose gel electrophoresis or dot-blot hybridisation. Viral RNA was detected in the organs and haemolymph of infected Amblyomma variegatum ticks, and in the brain and blood of infected mice. The PCR technique was found to be as sensitive as a plaque assay for detecting DUG virus, but not as sensitive as intracerebral inoculation of mice. The sensitivity of the technique was greatest using crude RNA extracts combined with dot-blot analysis of the resulting PCR products using a DUG specific cDNA probe. A result was obtained within 48 h using PCR whereas biological assays took at least 8 days to diagnose the virus infection.

Synthesis of bluetongue virus-encoded phosphoprotein and formation of inclusion bodies by recombinant baculovirus in insect cells: it binds the single-stranded RNA species

A DNA clone of RNA segment 8 (S8) of bluetongue virus type 10 (BTV-10), an orbivirus member of the Reoviridae family has been expressed to high levels (20 mg/1 x 10(9) cells) using an Autographa californica nuclear polyhedrosis virus expression vector (pA-cYM1). The expressed protein is similar to the authentic BTV phosphoprotein NS2, in its size, antigenicity, and also the manner of phosphorylation (e.g. same peptides and residues). Both mammalian and insect cell-derived NS2 proteins are phosphorylated at serine residues only. Using affinity column chromatography and a gel retardation assay, the expressed protein has been shown to possess ssRNA-binding ability, a property which is shown to be independent of the phosphorylation state of the protein. In immunoelectron micrographic studies, gold-labelled anti-expressed NS2 antibodies have been used to localize the NS2 protein within the viral inclusion bodies (VIBs) in BTV-infected mammalian cells. Large inclusion bodies, morphologically similar to VIBs, have been identified in the recombinant virus-infected Spodoptera frugiperda cells. These structures have been shown to react with gold-labelled anti-BTV-10 antisera, demonstrating the first direct evidence of the origin of inclusion bodies in orbivirus infection.

Identification of bluetongue virus VP6 protein as a nucleic acid-binding protein and the localization of VP6 in virus-infected vertebrate cells

Recently the insect baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) has been effectively adapted as a highly efficient vector in insect cells for the expression of various genes. A cDNA sequence of RNA segment 9 of bluetongue virus serotype 10 (BTV-10, an orbivirus member of the Reoviridae family) encoding a minor core protein (VP6) has been inserted into the BamHI site of the pAcYM1 transfer vector derived from AcNPV. Spodoptera frugiperda cells were cotransfected with the derived vector in the presence of authentic AcNPV DNA to produce recombinant viruses. These synthesized significant amounts of a protein (representing ca. 50% of the stained cellular protein) similar in size and antigenicity to the authentic BTV VP6. The expressed protein was identified as a nucleic acid-binding protein by using an RNA overlay-protein blot assay. A polyclonal anti-VP6 serum prepared by using the expressed VP6 protein has been used in an immunogold procedure to locate VP6 in BTV-infected mammalian cells. Gold was found to be associated with the matrix of virus inclusion bodies (VIB), with viruslike particles in the VIB, as well as with mature virion particles that were in close proximity to the VIB or were released from cells and adsorbed to cell surfaces. The recombinant virus antigen has also been used to identify antibodies to different BTV serotypes in infected sheep sera, indicating the potential of the expressed protein as a group-reactive antigen for the diagnosis of BTV infections.

Viral interference in the tick, Rhipicephalus appendiculatus. II. Absence of interference with Thogoto virus when the tick gut is by-passed by parenteral inoculation

Genetic reassortment of Thogoto (THO) virus has been demonstrated in dually infected Rhipicephalus appendiculatus ticks. However previous results showed that oral superinfection is inhibited by interference. To ascertain the site of THO viral interference, ticks were infected parenterally or orally with a temperature-sensitive (ts) mutant of THO virus. Infected ticks were then challenged with wild-type (wt) THO virus via parenteral inoculation. Intra-stadial superinfection was carried out by parenteral inoculation of newly infected engorged ticks whereas inter-stadial superinfection involved inoculation of engorged ticks infected at the previous stage. In both instances viral interference was not observed, i.e. the challenge virus replicated and was delivered by bite to susceptible hosts. Therefore when the gut is bypassed, R. appendiculatus ticks are apparently permissive to dual infection even when there is a delay in the presentation of the superinfecting virus. These results demonstrate that interference following superinfection per os does not occur in the salivary glands, but may occur in the gut and possibly in a secondary site of viral replication such as the synganglion.

Anatomical basis of Thogoto virus infection in BHK cell culture and in the ixodid tick vector, Rhipicephalus appendiculatus

Infection by Thogoto (THO) virus, a tick-borne virus related to the orthomyxoviruses, has been compared in vertebrate cell culture and in Rhipicephalus appendiculatus ticks using infectivity titrations, immunofluorescence, and immune electron microscopy with colloidal gold markers to detect cell surface and intracellular antigens. Morphogenesis of THO virus in cell culture was similar to that of influenza virus, with polymorphic virus particles budding at the plasma membrane. In the tick, THO viral infection caused no obvious pathology; virions or budding profiles were not observed in electron micrographs, although replication, trans-stadial persistence and transmission to a susceptible host occur. THO virus was not detected in the salivary glands of trans-stadially infected ticks until about 7 days after the commencement of feeding on a host. The synganglion (brain) appears to be the major organ involved in trans-stadial persistence of the virus; viral antigens were detected in the neural cortex (cell bodies) but not in nerve fibres and axons. The detection of THO viral antigen in basement membranes and connective tissue, but its absence from nerve fibres, suggests that dissemination occurs via the haemolymph rather than a neural route.

Wax lipid secretion and ultrastructural development in the egg-waxing (Gene's) organ in ixodid ticks

Gene's organ, the egg-waxing organ of ticks, performs an essential function in females by coating the eggs with a waterproofing layer during oviposition, which prevents desiccation of the embryo, ensuring its viability. The organ is a target for control agents and a potential site of virus replication involving trans-oval transmission of arboviruses. The organ is a complex dermal gland, developed to an elaborate degree. The external appendage, the horns, is an evertable balloon-like cuticular sac which manipulates the eggs and coats them in wax. Wax passes through pores in the cuticle from the internal, sub-cuticular lumen. Gene's organ develops in synchrony with oogenesis and oviposition. This paper describes the development of the gland cells and formation of the intra-cuticular lumen and its ultrastructure during engorgement and oviposition in ixodid ticks. The structural basis for wax secretion in Gene's organ is also described.

Ultrastructure of the accessory glands of gene's organ in the cattle tick, Boophilus

The organization and ultrastructure of the accessory glands of the cattle tick, Boophilus microplus, are described. The glands consist of two groups of acinar cells situated on either side of Gene's organ. A single acinus consists of from eight to 12 cells and each cell is connected via an individual duct to pores on the dorsal surface of the mouthparts. The position of these pores is such that the secretion of the accessory glands is incorporated into the egg wax during oviposition. Each gland cell has striking quantities of smooth endoplasmic reticulum and numerous Golgi dictyosomes and appears to produce a secretion that is lipoidal in nature. Each cell secretes into its own individual lumen and is connected to a cuticular pore by a duct cell.