Tissue tropism of avian reoviruses is genetically determined

Two genome segments, M2 and S1, were preferentially selected in reassortants isolated in Vero cells. Analysis with monoclonal antibodies (MAbs) against RAM-1 strain showed that the 39-kDa protein encoded by the genome segment S1 contained epitopes involved in neutralisation of virus infecti vity for both Vero and chicken kidney (CK) cells. The 39-kDa protein appeared to have two major epitopes that are attachment sites for cell receptors, one interacting only with CK cell receptors and the other with both CK and Vero cell receptors but principally Vero cell receptors. These results suggest that the strain RAM-1 may have developed an epitope for Vero cell receptors owing to mutation in the S1 genome segment, but still retained the epitope responsible for infection of CK cells

Sequence and structure relatedness of matrix protein of human respiratory syncytial virus with matrix proteins of other negative-sense RNA viruses

Matrix proteins of viruses within the order Mononegavirales have similar functions and play important roles in virus assembly. Protein sequence alignment, phylogenetic tree derivation, hydropathy profiles and secondary structure prediction were performed on selected matrix protein sequences, using human respiratory syncytial virus matrix protein as the reference. No general conservation of primary, secondary or tertiary structure was found, except for a broad similarity in the hydropathy pattern correlating with the fact that all the proteins studied are membrane-associated. Interestingly, the matrix proteins of Ebola virus and human respiratory syncytial virus shared secondary structure homology.</p

Immune response to avian reovirus in chickens and protection against experimental infection

Objectives To assess the efficacy of the vaccination procedure and the effect of the transfer of maternal antibodies to progeny chickens on reovirus pathogenicity. Design To vaccinate chickens and challenge progeny chickens with high doses of homologous and heterologous viruses. Procedure High doses of reovirus strains RAM-1, 1091 and 724 were used to induce tenosynovitis lesions. High doses were produced by concentration of viruses grown in cell culture. Then similar doses of viruses were used to challenge immunised chickens progeny. Result Vaccination of breeding hens with the RAM-1 strain of avian reovirus, which resulted in the passive transfer of neutralising antibody to progeny chickens, completely prevented the development of tenosynovitis in 80% of progeny chickens infected with the homologous virus. Even though multiple injection of hens resulted in broadening of the normal type-specificity of the neutralising antibody response against heterologous serotypes of avian reovirus, only marginal protection against strains of two heterologous serotypes of avian reovirus was obtained. Conclusions A model for assessing the efficacy of vaccination against avian reovirus strains on clinical signs such as tenosynovitis was developed that overcome the normal low virulence of Australian strains of avian reovirus. Breeding hens can be immunised with Australian strain of avian reovirus with passive transfer of antibody via the yolk to the progeny chickens. Although the neutralising antibody response to three injections of inactivated virus decreased the specificity of the neutralising antibody response against antigenically heterologous strains of avian reovirus, the protective immunity appeared to retain type-specificity

The matrix protein of Human respiratory syncytial virus localises to the nucleus of infected cells and inhibits transcription

We studied the kinetics of localisation of matrix (M) protein of Human respiratory syncytial virus (RSV) in infected cells. M protein was detected in the nucleus early in infection, by confocal microscopy and by immunoblotting of nuclear fractions. We next tested the possibility that M protein may be involved in inhibition of host cell transcription. Nuclear extracts from RSV infected cells had less transcriptional activity in vitro when compared to nuclear extracts from mock infected cells. In addition, nuclear extracts from RSV infected cells inhibited the transcriptional activity of nuclear extracts from mock infected cells, suggesting that an inhibitory activity was transferred with nuclear extracts from RSV infected cells. Our data suggest that M protein may play a role early in the infection by inhibiting host cell transcription.</p

Avian reovirus proteins associated with neutralization of virus infectivity

Monoclonal antibodies against two virion proteins of the RAM-1 strain of avian reovirus neutralized virus infectivity; antibody against a 124-kDa(λB) protein caused broadly specific neutralization and antibody against a 39-kDa (σC) protein caused neutralization of greater type-specificity. The neutralizing activity of the monoclonals also exhibited host cell specificity: antibodies against the λB protein inhibited virus infectivity in Vero cells and not chicken kidney cells; one monoclonal antibody against the σC protein neutralized virus in only chicken kidney cells, whereas two other monoclonals against the σC protein neutralized virus in both Vero and chicken kidney cells but had greater neutralizing activity in Vero cells

Expression and characterisation of the ovine respiratory syncytial virus (ORSV) G protein for use as a diagnostic reagent

Respiratory syncytial virus (RSV) causes severe lower respiratory tract infection in children and calves. Antibodies to ovine RSV (ORSV) are common in sheep, but the clinical disease is not well defined. There is no report of ORSV infection in Australian sheep although respiratory distress syndrome has been described. This discrepancy may be due to the lack of a suitable diagnostic test. In this report, we have characterised the ORSV G protein in an attempt to study its relatedness to human and bovine RSV (HRSV, BRSV) and for use in the development of a suitable diagnostic assay. Full length and a truncated variant of ORSV G protein were expressed in mammalian cells and the expressed proteins characterised by indirect immunofluorescence and radioimmunoprecipitation assays. Our results indicate that like HRSV, the ORSV G protein is heavily glycosylated. The expressed protein was membrane bound as well as secreted and could be purified from culture supernatants and may be suitable for use in development of a diagnostic assay.</p

Association between the σC protein of avian reovirus and virus-induced fusion of cells

Monoclonal antibodies (MAbs) against a 39 kDa (σC) protein of the avian reovirus RAM-1 strain inhibited virus-induced fusion of cells and the protein was expressed on the surface of infected cells. The fusion-inhibiting activity of the three MAbs reacting with the σC protein suggest two putative epitopes were involved: one epitope recognised by antibody 6H1 and involved in fusion of both Vero and CK cells and a second epitope recognised by antibody 1G1 involved in fusion of Vero cells but not CK cells. The activity of the MAb 6E2 was intermediate, suggesting it may have been located in an intermediate position between the two putative epitopes and inhibited fusion by steric hindrance

Multiple heparin binding domains of respiratory syncytial virus G mediate binding to mammalian cells

Respiratory syncytial virus (RSV) G glycoprotein mediates cell attachment through surface glycosaminoglycans (GAGs). Feldman et al. [10] suggested that specific basic amino acids in residues 184-198 of G defined a critical heparin binding domain (HBD). To further define the G HBD we made a series of truncated G proteins expressed in Escherichia coli. G88 (G residues 143-231), bound to HEp-2 cells in a dose dependent manner and binding was inhibited &gt;99% with heparin. Cell binding of G88 was unaltered by alanine substitution mutagenesis of all basic amino acids in Feldman's region 184-198. A G88 variant truncated beyond residue 198, G58, and G58 fully alanine substituted in the region 184-198, G58A6, bound to HEp-2 cells about half as well and 100-fold less well than G88, respectively. G88 and all alanine substitution mutants of G88 inhibited RSV plaque formation by 50% (ID(50)) at concentrations of approximately 50 nM; the ID(50) of G58 was approximately 425 nM while G58A6 had an ID(50) &gt;1600 nM. These data show that the G HBD includes as much as residues 187-231, that there is redundancy beyond the previously described HBD, and that the cell-binding and virus infectivity-blocking functions of these recombinant G proteins were closely linked and required at least one HBD.</p