Characterization of the nuclear export signal in the coronavirus infectious bronchitis virus nucleocapsid protein.
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The nucleocapsid (N) protein of infectious bronchitis virus (IBV) localizes to the cytoplasm and nucleolus and contains an eight-amino-acid nucleolar retention motif. In this study, a leucine-rich nuclear export signal (NES) (291-LQLDGLHL-298) present in the C-terminal region of the IBV N protein was analyzed by using alanine substitution and deletion mutagenesis to investigate the relative contributions that leucine residues make to nuclear export and where these residues are located on the structure of the IBV N protein. The analysis indicated that Leu296 and Leu298 are required for efficient nuclear export of the protein. Structural information indicated that both of these amino acids are available for interaction with protein complexes involved in this process. However, export of N protein from the nucleus/nucleolus was not inhibited by leptomycin B treatment, indicating that N protein nuclear export is independent of the CRM1-mediated export pathway. (+info)
Monoclonal antibodies to three structural proteins of avian infectious bronchitis virus: characterization of epitopes and antigenic differentiation of Australian strains.
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Ten monoclonal antibodies (MAbs) directed against three structural proteins of infectious bronchitis viruses (IBV), the peplomer (S), membrane (M) and nucleocapsid (N) proteins, were characterized and used to determine the antigenic relationship between Australian IBV strains. One MAb (MAb 5) was directed against an epitope on the S1 subunit of the peplomer, another (MAb 2) against an epitope on the M glycoprotein and eight MAbs (MAbs 1, 7, 9, 16, 24, 26, 27 and 51) were directed against seven non-overlapping epitopes on the N protein. None of the MAbs neutralized infectivity or inhibited haemagglutination of the virus. Conservation of the nine epitopes detected by these MAbs was determined in 13 serotypes of Australian IBV strains. Only epitope 5 on the S1 subunit of the peplomer was conserved in all strains. Epitope 2 on the M protein showed a high degree of conservation although this epitope was absent from four strains. None of the eight epitopes on the N proteins was conserved in all IBV strains but four epitopes (1, 16, 24 and 27) showed a high degree of conservation. Epitope 9 on the N protein was present only in IBV strains of one serotype whereas epitope 7 on the N protein distinguished vaccine viruses of serotype B from other IBV strains. The presence or absence of nine epitopes on three structural proteins differentiated IBV strains into five antigenic groups. (+info)
Infectious bronchitis virus (IBV), the coronavirus of the chicken (Gallus gallus), is one of the foremost causes of economic loss within the poultry industry, affecting the performance of both meat-type and egg-laying birds. The virus replicates not only in the epithelium of upper and lower respiratory tract tissues, but also in many tissues along the alimentary tract and elsewhere e.g. kidney, oviduct and testes. It can be detected in both respiratory and faecal material. There is increasing evidence that IBV can infect species of bird other than the chicken. Interestingly breeds of chicken vary with respect to the severity of infection with IBV, which may be related to the immune response. Probably the major reason for the high profile of IBV is the existence of a very large number of serotypes. Both live and inactivated IB vaccines are used extensively, the latter requiring priming by the former. Their effectiveness is diminished by poor cross-protection. The nature of the protective immune response to IBV is poorly understood. What is known is that the surface spike protein, indeed the amino-terminal S1 half, is sufficient to induce good protective immunity. There is increasing evidence that only a few amino acid differences amongst S proteins are sufficient to have a detrimental impact on cross-protection. Experimental vector IB vaccines and genetically manipulated IBVs--with heterologous spike protein genes--have produced promising results, including in the context of in ovo vaccination. (+info)
Feline aminopeptidase N is not a functional receptor for avian infectious bronchitis virus.
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BACKGROUND: Coronaviruses are an important cause of infectious diseases in humans, including severe acute respiratory syndrome (SARS), and have the continued potential for emergence from animal species. A major factor in the host range of a coronavirus is its receptor utilization on host cells. In many cases, coronavirus-receptor interactions are well understood. However, a notable exception is the receptor utilization by group 3 coronaviruses, including avian infectious bronchitis virus (IBV). Feline aminopeptidase N (fAPN) serves as a functional receptor for most group 1 coronaviruses including feline infectious peritonitis virus (FIPV), canine coronavirus, transmissible gastroenteritis virus (TGEV), and human coronavirus 229E (HCoV-229E). A recent report has also suggested a role for fAPN during IBV entry (Miguel B, Pharr GT, Wang C: The role of feline aminopeptidase N as a receptor for infectious bronchitis virus. Brief review. Arch Virol 2002, 147:2047-2056. RESULTS: Here we show that, whereas both transient transfection and constitutive expression of fAPN on BHK-21 cells can rescue FIPV and TGEV infection in non-permissive BHK cells, fAPN expression does not rescue infection by the prototype IBV strain Mass41. To account for the previous suggestion that fAPN could serve as an IBV receptor, we show that feline cells can be infected with the prototype strain of IBV (Mass 41), but with low susceptibility compared to primary chick kidney cells. We also show that BHK-21 cells are slightly susceptible to certain IBV strains, including Ark99, Ark_DPI, CA99, and Iowa97 (<0.01% efficiency), but this level of infection is not increased by fAPN expression. CONCLUSION: We conclude that fAPN is not a functional receptor for IBV, the identity of which is currently under investigation. (+info)
Strong antiviral activity of heated and hydrated dolomite--preliminary investigation.
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Heated and hydrated naturally occurring dolomite showed very strong antiviral activity. Infectivity of avian and human influenza, avian infectious bronchitis (coronavirus), Newcastle disease (paramyxovirus) and avian laryngotracheitis (herpesvirus) viruses dropped at least 1,000 fold following contact with the dolomite for five minutes at 4 degrees C. Dolomite is expected to be useful to inhibit the incidence of emerging and re-emerging infectious diseases. (+info)
Characterisation of cyclin D1 down-regulation in coronavirus infected cells.
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The positive strand RNA coronavirus, infectious bronchitis virus (IBV), induces a G2/M phase arrest and reduction in the G1 and G1/S phase transition regulator cyclin D1. Quantitative real-time RT-PCR and Western blot analysis demonstrated that cyclin D1 was reduced post-transcriptionally within infected cells independently of the cell-cycle stage at the time of infection. Confocal microscopy revealed that cyclin D1 decreased in IBV-infected cells as infection progressed and inhibition studies indicated that a population of cyclin D1 could be targeted for degradation by a virus mediated pathway. In contrast to the SARS-coronavirus, IBV nucleocapsid protein did not interact with cyclin D1. (+info)
Cell cycle arrest and apoptosis induced by the coronavirus infectious bronchitis virus in the absence of p53.
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Manipulation of the cell cycle and induction of apoptosis are two common strategies used by many viruses to regulate their infection cycles. In cells infected with coronaviruses, cell cycle perturbation and apoptosis were observed in several reports. However, little is known about how these effects are brought out, and how manipulation of the functions of host cells would influence the replication cycle of coronavirus. In this study, we demonstrate that infection with coronavirus infectious bronchitis virus (IBV) imposed a growth-inhibitory effect on cultured cells by inducing cell cycle arrest at S and G(2)/M phases in both p53-null cell line H1299 and Vero cells. This cell cycle arrest was catalyzed by the modulation of various cell cycle regulatory genes and the accumulation of hypophosphorylated RB, but was independent of p53. Proteasome inhibitors, such as lactacystin and NLVS, could bypass the IBV-induced S-phase arrest by restoring the expression of corresponding cyclin/Cdk complexes. Our data also showed that cell cycle arrest at both S- and G(2)/M-phases was manipulated by IBV for the enhancement of viral replication. In addition, apoptosis induced by IBV at late stages of the infection cycle in cultured cells was shown to be p53-independent. This conclusion was drawn based on the observations that apoptosis occurred in both IBV-infected H1299 and Vero cells, and that IBV infection did not affect the expression of p53 in host cells. (+info)
Comparison of a microneutralization test in cell culture and virus neutralization test in embryonated eggs for determining infectious bronchitis virus antibodies.
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A microneutralization test (MNT) system utilizing cytopathic effect end points was effective in determing neutralization indexes for infectious bronchitis virus antibodies. The system is reproducible within 1 index unit at the 95% level of probability. Comparison of the MNT to tests in eggs resulted in a positive correlation (B =0.81), which was significant (P greater than 0.01). The quantitative dose-response relationship of the MNT is linear (P greater than 0.005), with the 95% prediction limits fitting between one 10-fold dilution. (+info)