The shape of the acetabular cartilage follows the contact stress distribution across the joint. Accurate characterisation of this geometry may be useful for the development of acetabular cup devices that are more biomechanically compliant. In this study, the geometry of the acetabular cartilage was characterised by taking plaster moulds of the acetabulum from 24 dry bone human pelvises and digitising the mould shapes using a three-dimensional laser scanner. The articular bone surface geometry was analysed, and the shape of the acetabulum was approximated by fitting a best-fit sphere. To test the hypothesis that the acetabulum is non-spherical, a best-fit ellipsoid was also fitted to the geometry. In each case, points around the acetabular notch edge that disclosed the articular surface geometry were identified, and vectors were drawn between these and the best-fit sphere or ellipsoid centre. The significantly larger z radii (into the pole) of the ellipsoids indicated that the acetabulum was non-spherical and could imply that the kinematics of the hip joint is more complex than purely rotational motion, and the traditional ball-and-socket replacement may need to be updated to reflect this motion. The acetabular notch edges were observed to be curved, with males exhibiting deeper, wider and shorter notches than females, although the difference was not statistically significant (mean: p = 0.30) and supports the use of non-gender-specific models in anatomical studies.
We established a reverse genetics system for Nyamanini virus (NYMV) and recovered green fluorescent protein (GFP)-expressing virus from full-length cDNA. Using this technology, we assessed the functions of two poorly characterized viral genes. NYMV lacking open reading frame 2 (ORF2) could not be rescued, whereas virus lacking ORF4 was replication competent. ORF4-deficient NYMV readily established a persisting noncytolytic infection but failed to produce infectious viral particles, supporting the view that ORF4 represents an essential factor for NYMV particle assembly.
Nyamanini virus (NYMV) and Midway virus (MIDWV) are unclassified tick-borne agents that infect land birds and seabirds, respectively. The recent molecular characterization of both viruses confirmed their already known close serological relationship and revealed them to be nonsegmented, single- and negative-stranded RNA viruses that are clearly related to, but quite distinct from, members of the order Mononegavirales (bornaviruses, filoviruses, paramyxoviruses, and rhabdoviruses). A third agent, soybean cyst nematode virus 1 (SbCNV-1, previously named soybean cyst nematode nyavirus), was recently found to be an additional member of this new virus group. Here, we review the current knowledge about all three viruses and propose classifying them as members of a new mononegaviral family, Nyamiviridae.
The terminal structures of the Borna disease virus (BDV) genome (vRNA) and antigenome (cRNA) differ from those of other negative strand RNA viruses, as both molecules possess four nucleotides at the 3 terminus without an apparent template at the 5 end of the opposite strand. Consequently, the v- and cRNA molecules are not perfect mirror images, a situation that is not compatible with conventional strategies to maintain genetic information. We show here that recombinant viruses recovered from cDNA lacking the nontemplated nucleotides efficiently reconstitute the 3 overhangs. Analyses of recombinant viruses encoding genetic markers in potential alternative template sequences demonstrated that the BDV v- and cRNA molecules are extended by a realign-and-elongation process on internal template motifs located in close proximity to the 3 ends of v- and cRNA, respectively. The data further suggest that cRNA elongation is restricted to a single template motif of the nascent strand, whereas elongation of vRNA might use multiple template motifs. We propose that the elongation of the 3 termini supports the terminal integrity of the genomic RNA molecules during BDV persistence, and furthermore provides an elegant strategy to eliminate the triphosphate groups from the 5 termini of the BDV v- and cRNA without compromising the genetic information of the virus.
Borna disease virus (BDV) frequently persists in the brain of infected animals. To analyze viral dissemination in the mouse nervous system, we generated a mouse-adapted virus that expresses green fluorescent protein (GFP). This viral vector supported GFP expression for up to 150 days and possessed an extraordinary staining capacity, visualizing complete dendritic arbors as well as individual axonal fibers of infected neurons. GFP-positive cells were first detected in cortical areas from where the virus disseminated through the entire central nervous system (CNS). Late in infection, GFP expression was found in the sciatic nerve, demonstrating viral spread from the central to the peripheral nervous system.
The X protein of Borna disease virus (BDV) is an essential factor that regulates viral polymerase activity and inhibits apoptosis of persistently infected cells. We observed that a BDV mutant which carries an additional X gene replicated well in cell culture only after acquiring second-site mutations that selectively reduced expression of the endogenous X gene. In rat brains, the virus acquired additional mutations which inactivated the ectopic X gene or altered the sequence of X. These results demonstrate that BDV readily acquires mutations if strong selection pressure is applied. They further indicate that fine-tuning of X expression determines viral fitness.
Borna disease virus (BDV) is a neurotropic member of the order Mononegavirales with noncytolytic replication and obligatory persistence in cultured cells and animals. Here we show that the accessory protein X of BDV represents the first mitochondrion-localized protein of an RNA virus that inhibits rather than promotes apoptosis induction. Rat C6 astroglioma cells persistently infected with wild-type BDV were significantly more resistant to death receptor-dependent and -independent apoptotic stimuli than uninfected cells or cells infected with a BDV mutant expressing reduced amounts of X. Confocal microscopy demonstrated that X colocalizes with mitochondria and expression of X from plasmid DNA rendered human 293T and mouse L929 cells resistant to apoptosis induction. A recombinant virus encoding a mutant X protein unable to associate with mitochondria (BDV-X(A6A7)) failed to block apoptosis in C6 cells. Furthermore, Lewis rats neonatally infected with BDV-X(A6A7) developed severe neurological symptoms and died around day 30 postinfection, whereas all animals infected with wild-type BDV remained healthy and became persistently infected. TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) staining revealed a significant increase in the number of apoptotic cells in the brain of BDV-X(A6A7)-infected animals, whereas the numbers of CD3(+) T lymphocytes were comparable to those detected in animals infected with wild-type BDV. Our data thus indicate that inhibition of apoptosis by X promotes noncytolytic viral persistence and is required for the survival of cells in the central nervous system of BDV-infected animals.
Tick-borne Nyamanini virus (NYMV) is the prototypic member of a recently discovered genus in the order Mononegavirales, designated Nyavirus. The NYMV genome codes for six distinct genes. Sequence similarity and structural properties suggest that genes 1, 5, and 6 encode the nucleoprotein (N), the glycoprotein (G), and the viral polymerase (L), respectively. The function of the other viral genes has been unknown to date. We found that the third NYMV gene codes for a protein which, when coexpressed with N and L, can reconstitute viral polymerase activity, suggesting that it represents a polymerase cofactor. The second viral gene codes for a small protein that inhibits viral polymerase activity and further strongly enhances the formation of virus-like particles when coexpressed with gene 4 and the viral glycoprotein G. This suggests that two distinct proteins serve a matrix protein function in NYMV as previously described for members of the family Filoviridae. We further found that NYMV replicates in the nucleus of infected cells like members of the family Bornaviridae. NYMV is a poor inducer of beta interferon, presumably because the viral genome is 5 monophosphorylated and has a protruding 3 terminus as observed for bornaviruses. Taken together, our results demonstrate that NYMV possesses biological properties previously regarded as typical for filoviruses and bornaviruses, respectively.
Bornaviruses are nonsegmented negative-strand RNA viruses that establish a persistent infection in the nucleus and occasionally integrate a DNA genome copy into the host chromosomal DNA. However, how these viruses achieve intranuclear infection remains unclear. We show that Borna disease virus (BDV), a mammalian bornavirus, closely associates with the cellular chromosome to ensure intranuclear infection. BDV generates viral factories within the nucleus using host chromatin as a scaffold. In addition, the viral ribonucleoprotein (RNP) interacts directly with the host chromosome throughout the cell cycle, using core histones as a docking platform. HMGB1, a host chromatin-remodeling DNA architectural protein, is required to stabilize RNP on chromosomes and for efficient BDV RNA transcription in the nucleus. During metaphase, the association of RNP with mitotic chromosomes allows the viral RNA to segregate into daughter cells and ensure persistent infection. Thus, bornaviruses likely evolved a chromosome-dependent life cycle to achieve stable intranuclear infection.
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