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Immunity to avian infectious bronchitis.

Avian infectious bronchitis is recognized clinically as a respiratory disease in its only natural host,the chicken, but the virus is disseminated throughout other systems by a viraemia with localization especially in the kidney and oviduct. The sensitivity or instability of the antigenic and immunogenic properties of the virus under laboratory stress or natural influences complicates the selection of seed virus for vaccines. Modified or attenuated active virus vaccines induce greater protection against subsequent infection than do inactive virus vaccines. Maternal antibody is effective in providing passive immunity for about two weeks after the chick is hatched. Immunoglobulins induced by primary infection or by vaccination are IgG effective for neutralization of virus by circulating antibody, and presumably secretory IgA in the respiratory tract, with the latter being more effective as evidenced by protection of the trachea against reinfection. The level of humoral antibody is not necessarily correlative with immunity based on chicken protection tests against challenge with virulent virus. A true carrier status apparently does not result from primary infection but it has been suggested that the chicken may possibly become an immune carrier.

Animals↗

Transcriptional analysis of avian embryonic tissues following infection with avian infectious bronchitis virus.

Avian infectious bronchitis virus (IBV) infection is one of the major viral respiratory diseases of chickens. Better understanding of the molecular basis of viral pathogenesis should contribute significantly towards the development of improved prophylactic, therapeutic and diagnostic reagents to control infections. In the present investigation, transcriptional profiles were analyzed by using RNA recovered from the lung tissue of IBV infected 18-day-old chicken embryos at 6, 24, 48 and 72 h post IBV infection. This microarray analysis was completed using avian cDNA arrays comprised of fragments of 1191 unique chicken and turkey gene transcripts. These arrays were generated from normalized cDNA subtraction libraries that were derived from avian pneumovirus (APV) infected chicken embryo fibroblast (CEF) cultures and tissues obtained from APV infected turkeys subtracted with their respective uninfected cultures and tissues. Of the 1191 unique genes represented on the array, the expression of a total of 327 genes (27% of total) were altered by two-fold or more from 6 through 72 h post-infection. A comparative analysis of IBV regulated genes with genes previously reported to change in expression following infection with other avian respiratory viruses revealed both conserved and unique changes. Real-time qRT-PCR was used to confirm the regulated expression of genes related to several functional classes including kinases, interferon induced genes, chemokines and adhesion molecules, vesicular trafficking and fusion protein genes, extracellular matrix protein genes, cell cycle, metabolism, cell physiology and development, translation, RNA binding, lysosomal, protein degradation and ubiquitination related genes. Microarray analysis served as an efficient tool in facilitating a comparative analysis of avian respiratory viral infections and provided insight into host transcriptional changes that were conserved as well as those which were unique to individual pathogens.

Animals↗

The polypeptide composition of avian infectious bronchitis virus.

Avian infectious bronchitis virus grown in ovo was purified by differential centrifugation and isopycnic sedimentation in density gradients. The purified virus was analysed by SDS polyacrylamide gel electrophoresis and found to comprise up to sixteen polypeptides, four of which were glycopeptides. Bromelain treatment of the particles removed three polypeptides and two glycopeptides.

Bromelains↗

Recent studies on the enterotropic strain of avian infectious bronchitis virus.

Avian infectious bronchitis (AIB) is an economically important disease of chickens. Recent studies have revealed enterotropism by at least one strain of AIB virus with pathological lesions in parts of the gut. This review highlights the findings of the studies so far made on this enterotropic strain of AIB virus.

Animals↗

Studies on the structure of a coronavirus-avian infectious bronchitis virus.

When avian infectious bronchitis virus (IBV) is fixed in formaldehyde, negative stain is able to penetrate the particle and an internal component is visualized. This component is seen as a tongue or flask shaped structure attached at one point to the outer virus membrane. A model yielding transmission patterns similar to the virus has been made. Gradient centrifugation studies on IBV reveal that the RNP is associated with the internal sac.

Coronaviridae↗

Polypeptides of the surface projections and the ribonucleoprotein of avian infectious bronchitis virus.

Purified avian infectious bronchitis virus was digested with bromelain (0.7 mg/ml), and the surface projections were removed. Polyacrylamide gel electrophoresis of the polypeptides from these bromelain-treated particles showed that VP1, VP2, and VP5 were missing from the seven polypeptides. VP1 to VP7, that were present in untreated virus preparations. Milder bromelain treatment (0.07 mg/ml) left visible surface projections and polypeptides comprising VP1 and VP2 intact, but removed VP5. Thus, there are apparently two types of surface projections on the virus particle. The ribonucleoprotein complex was released from virus particles disrupted with 1% Nonidet P-40. The proportion of VP6 in such preparations was greatly reduced, implying that VP6 is the structural polypeptide of the ribonucleoprotein. Polypeptides VP1, VP2, VP4, and VP5 are glycosylated, but none of the polypeptides contains lipid.

Bromelains↗

One-pot Golden Gate Assembly of an avian infectious bronchitis virus reverse genetics system.

Avian infectious bronchitis is an acute respiratory disease of poultry of particular concern for global food security. Investigation of infectious bronchitis virus (IBV), the causative agent of avian infectious bronchitis, via reverse genetics enables deeper understanding of virus biology and a rapid response to emerging variants. Classic methods of reverse genetics for IBV can be time consuming, rely on recombination for the introduction of mutations, and, depending on the system, can be subject to genome instability and unreliable success rates. In this study, we have applied data-optimized Golden Gate Assembly design to create a rapidly executable, flexible, and faithful reverse genetics system for IBV. The IBV genome was divided into 12 fragments at high-fidelity fusion site breakpoints. All fragments were synthetically produced and propagated in E. coli plasmids, amenable to standard molecular biology techniques for DNA manipulation. The assembly can be carried out in a single reaction, with the products used directly in subsequent viral rescue steps. We demonstrate the use of this system for generation of point mutants and gene replacements. This Golden Gate Assembly-based reverse genetics system will enable rapid response to emerging variants of IBV, particularly important to vaccine development for controlling spread within poultry populations.

Infectious bronchitis virus↗

The polypeptide composition of isolated surface projections of avian infectious bronchitis virus.

Disruption of avian infectious bronchitis virus (IBV) particles with 4% Triton X-100 and 1.0 M-KCl and centrifugation through a sucrose gradient containing 0.1% Triton X-100 and 1.0 M-KCl enabled separation of the petal-shaped surface projections. By negative-contrast electron microscopy the separated projections appeared mainly as rosettes containing 3 to 12 projections radiating from a central core, although single projections and rosettes containing up to 16 projections were seen. SDS-PAGE of these preparations revealed two polypeptides of 86,000 and 66,000 mol. wt. The larger polypeptide was glycosylated.

Coronaviridae↗

Identification of one peptide which inhibited infectivity of avian infectious bronchitis virus in vitro.

Purified avian infectious bronchitis virus (IBV) was used to screen a random phage display peptide library. After the fourth panning, 10 positive phages were sequenced and characterized. The phages specifically inhibited IBV infectivity in HeLa cells and blocked IBV haemagglutination. One linear peptide "GSH HRH VHS PFV" from the positive phages with the highest neutralization titer was synthesized and this peptide inhibited IBV infection in HeLa as well. The results may contribute to development of antiviral therapeutics for IBV and studying the determinants for viral and cell interaction.

Amino Acid Sequence↗

The resistance to reinfection of tracheal organ cultures from chickens previously infected with avian infections bronchitis virus.

Lower titres of avian infectious bronchitis (AIB) virus were found following the infection of tracheal organ cultures prepared from chickens that had been given AIB virus intranasally six weeks previously than were found following the infection of organ cultures prepared from untreated or from passively-immune chickens. No infectious virus was found in the tracheal organ cultures at the time they were prepared.

Animals↗

Serological relationship among ten strains of avian infectious bronchitis virus.

Ten strains of avian infectious bronchitis virus (IBV) were studied serologically by cross-neutralization test using rabbit and chicken immune sera. With the chicken sera all 10 IBV strains were antigenically related. In particular, anti-KH serum neutralized all heterologous strains except of the Ishida strain; Nerima strain was neutralized by all antisera except of anti-Ishida serum. Most cross-reactions were less or more heterologous, thus all 10 IBV strains seemed to belong to one serological type. Using rabbit sera, all strains except of Connecticut A-5968, cross-reacted with certain other strains. Most cross-reactions were partially heterologous showing one-way-relationship; heterologous relations were observed less frequently than with chicken sera.

Animals↗