Role of phosphorylation clusters in the biology of the coronavirus infectious bronchitis virus nucleocapsid protein.
The coronavirus infectious bronchitis virus (IBV) nucleocapsid (N) protein is an RNA binding protein which is phosphorylated at two conserved clusters. Kinetic analysis of RNA binding indicated that the C-terminal phosphorylation cluster was involved in the recognition of viral RNA from non-viral RNA. The IBV N protein has been found to be essential for the successful recovery of IBV using reverse genetics systems. Rescue experiments indicated that phosphorylated N protein recovered infectious IBV more efficiently when compared to modified N proteins either partially or non-phosphorylated. Our data indicate that the phosphorylated form of the IBV N protein plays a role in virus biology. (+info)
Sequence analysis of the S1 glycoprotein gene of infectious bronchitis viruses: identification of a novel phylogenetic group in Korea.
Twelve Korean infectious bronchitis viruses (IBVs) were isolated in the field from chickens suspected of being carriers of infectious bronchitis between 2001 and 2003. The S1 glycoprotein genes of these IBV isolates were amplified by reverse transcriptase-polymerase chain reaction (RTPCR) and analyzed by restriction fragment length polymorphism (RFLP) analysis. These Korean IBV isolates were classified into three groups according to their RFLP patterns obtained using the restriction enzyme HaeIII. Half of the twelve isolates were similar to the KM91 RFLP pattern, which is a common pattern in Korea. Three more isolates were related to the Arkansas strain pattern, but with some unique variations. The other three viruses showed variant RFLP patterns. For a comparison with the published sequences for non-Korean IBV strains, amplified PCR products from the twelve isolates were cloned and sequenced. The Korean IBV field isolates had 71.2-99.7% nucleotide sequence homology with each other and 45.9-80.7% nucleotide sequence homology with non-Korean IBV strains. With respect to the deduced amino acid sequence, the Korean IBV isolates had 71.5-99.3% similarity with each other and 44.9-80.3% similarity with non-Korean IBV strains. Phylogenetic tree analysis revealed that some of the IBV isolates appear to belong to a new group, different from the non-Korean IBV strains or from previously isolated Korean IBV strains. Specifically, the new Korean IBV isolates K10217-03, K3-3 and K1255-03 represented a separate group. These findings suggest that the Korean IBVs appear to be continuously evolving. (+info)
Effects of several virucidal agents on inactivation of influenza, Newcastle disease, and avian infectious bronchitis viruses in the allantoic fluid of chicken eggs.
General theories on the inactivation of viruses in the presence of a concentrated protein, such as the allantoic fluid of chicken eggs, are not useful. That is, although sodium hypochlorite and sodium hydroxide are generally known as strong virucidal agents, they do not sufficiently inactivate viruses in allantoic fluid. We found that benzalkonium chloride (BC) is an effective virucidal agent against influenza, Newcastle disease, and avian infectious bronchitis viruses even in the presence of a concentrated protein. BC is easily biodegradable by activated sludge and is not very harmful to humans. We strongly recommend BC as a useful virucidal agent, especially in the manufacture of vaccines for these viruses. (+info)
Infectious bronchitis viruses with a novel genomic organization.
A number of novel infectious bronchitis viruses (IBVs) were previously identified in commercial poultry in Australia, where they caused significant economic losses. Since there has been only limited characterization of these viruses, we investigated the genomic and phenotypic differences between these novel IBVs and other, classical IBVs. The 3' 7.5 kb of the genomes of 17 Australian IBV strains were sequenced, and growth properties of 6 of the strains were compared. Comparison of sequences of the genes coding for structural and nonstructural proteins revealed the existence of two IBV genotypes: classical and novel. The genomic organization of the classical IBVs was typical of those of other group III coronaviruses: 5'-Pol-S-3a-3b-E-M-5a-5b-N-untranslated region (UTR)-3'. However, the novel IBV genotype lacked either all or most of the genes coding for nonstructural proteins at the 3' end of the genome and had a unique open reading frame, X1. The gene order was either 5'-Pol-S-X1-E-M-N-UTR-3' or 5'-Pol-S-X1-E-M-5b-N-UTR-3'. Phenotypically, novel and classical IBVs also differed; novel IBVs grew at a slower rate and reached lower titers in vitro and in vivo and were markedly less immunogenic in chicks. Although the novel IBVs induced histopathological lesions in the tracheas of infected chicks that were comparable to those induced by classical strains, they did not induce lesions in the kidneys. This study has demonstrated for the first time the existence of a naturally occurring IBV genotype devoid of some of the genes coding for nonstructural proteins and has also indicated that all of the accessory genes are dispensable for the growth of IBV and that such viruses are able to cause clinical disease and economic loss. The phylogenic differences between these novel IBVs and other avian coronaviruses suggest a reservoir host distinct from domestic poultry. (+info)
The spike protein of infectious bronchitis virus is retained intracellularly by a tyrosine motif.
We have analyzed the intracellular transport of the spike (S) protein of infectious bronchitis virus (IBV), an avian coronavirus. Surface expression was analyzed by immunofluorescence microscopy, by surface biotinylation, and by syncytium formation by S-expressing cells. By applying these methods, the S protein was found to be retained intracellularly. Tyr1143 in the cytoplasmic tail was shown to be a crucial component of the retention signal. Deletion of a dilysine motif that has previously been suggested to function as a retrieval signal did not abolish intracellular retention. Treatment of the S proteins with endoglycosidases did not reveal any differences between the parental and the mutant proteins. Furthermore, all S proteins analyzed were posttranslationally cleaved into the subunits S1 and S2. In coexpression experiments, the S protein was found to colocalize with a Golgi marker. Taken together, these results indicate that the S protein of IBV is retained at a late Golgi compartment. Therefore, this viral surface protein differs from the S proteins of transmissible gastroenteritis virus and severe acute respiratory syndrome coronavirus, which are retained at a pre-Golgi compartment or transported to the cell surface, respectively. The implications of these differences are discussed. (+info)
Molecular epidemiology and evolution of avian infectious bronchitis virus in Spain over a fourteen-year period.
Organ culture studies on the efficiency of infection of chicken tissues with avian infectious bronchitis virus.
Long-term organ cultures of a range of tissues collected from specific pathogen-free chickens were employed to determine their susceptibility, and their capacity for subsequent virus production, following inoculation with avian infectious bronchitis (AIB) virus. When inoculated with approximately 2-0 log10 median ciliostatic doses (CD50) of a classical highly egg-adapted vaccine strain (H120) of AIB virus, 9 of 23 tissues were shown to be susceptible, namely the nasal turbinates, trachea, air sac membranes,lungsasal turbinates, trachea, air sac membranes, lungs, proventriculus mucosa, thyroid, kidney, ovary and oviduct. When the remaining 14 tissues were inoculated with a high dose of virus (6.8 log10 CD50), the conjunctiva, caecel tonsil, testis and bursa of Fabricius were susceptible whereas the oesophagus and cloaca responded minimally. Inoculation of the same range of tissues with a high or low dose of a field strain (HVI9) of AIB virus produced similar results, except for a number of individual variations in response, due possibly to strain differences in pathogenicity. Determinations of the minimal infectious dose requirements of the susceptible tissues revealed that the efficiency of infection with the H120 strain was highest for the nasal turbinate and tracheal tissues, and thereafter, in order of decreasing efficiency, were the air sac membranes, lung, oviduct, proventriculus mucosa, conjunctiva, kidney, ovary, bursa of Fabricius, thyroid, testis, caecal tonsil, cloaca and oesophagus. The relevance of these results is discussed in connection with the early events in the pathogenesis and the clinical syndrome of AIB infection in chickens. (+info)