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PubMedDate not supplied

In vivo evaluation of the pathogenicity of field isolates of infectious bronchitis virus.

The pathogenicity of 13 field isolates of infectious bronchitis virus (IBV) isolated from Georgia broiler farms from 1989 to 1992 was evaluated using the IBV and Escherichia coli mixed-infection model. Based on the clinical signs, mortality, and lesions, the isolates were classified as high, intermediate, and low in pathogenicity. The in vivo classification was compared with the serotype classification results obtained by reverse transcriptase-polymerase chain reaction-restriction fragment length polymorphism analysis. The high-pathogenicity group was composed of five isolates representing three serotypes: Arkansas, Georgia variant (GAV), and Massachusetts. Isolates in the intermediate- and low-pathogenicity groups were all representatives of the Connecticut serotype, except for one isolate, which belonged to the Massachusetts serotype.

Animals↗
PubMed2007

Characterization of the nuclear export signal in the coronavirus infectious bronchitis virus nucleocapsid protein.

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.

Amino Acid Substitution↗
PubMedDate not supplied

Novel infectious bronchitis virus S1 genotypes in Mexico 1998-1999.

Seventeen infectious bronchitis virus (IBV) field isolates recovered from commercial broiler flocks in Mexico were identified by reverse transcription-polymerase chain reaction cycle sequencing of the S1 gene. The isolates were obtained from broilers on farms from the neighboring states of Queretaro and San Luis Potosi in 1998 and 1999. Flocks had an ongoing history of bacterial-complicated respiratory disease with mortality rates as high as 28% in spite of receiving live vaccinations for Massachusetts and Connecticut strains of IBV. Sequence analysis of the S1 gene identified two unique genotypes that have been described, as of this time, only in Mexico and thus appear to represent strains indigenous to the country. The Mex/1765/99 genotype was isolated from 64% (11/17) of the respiratory disease outbreaks. Three isolates (18%) were similar to the BL-56 genotype, a unique Mexican IBV strain observed initially in 1996. In addition to the two indigenous strains, three isolates (18%) were found to be the Connecticut genotype.

Animals↗
PubMed2005

Evaluation of serum- and animal protein-free media for the production of infectious bronchitis virus (M41) strain in a continuous cell line.

Infectious bronchitis virus (IBV) is produced in vitro using specific pathogen free chicken embryos, primary chicken kidney cells (CKC) and/or tracheal organ culture (TOC). Regulatory authorities in Europe (EMEA) and in the United States (FDA) have encouraged biological manufactures to reduce or eliminate the use of live animals and/or products of animal origin in biological manufacturing processes. In this paper, a stable chicken embryo-related (CER) cell line was adapted and maintained in serum free (SF) or animal protein free (APF) medium after a direct switch of the medium. The most suitable media were Ex Cell 520 and Ex Cell 302. CER monolayers adapted to SF or APF were infected with IBV (M41 strain) in agitated suspended culture and the IBV titre obtained 48 h post infection was 2.8 x 104 PFU/ml in both cases. Thus, propagation of CER cells and culture of IBV can be performed without the use of animal serum or animal protein.

Animals↗
PubMed1998

Cytotoxic T lymphocyte responses to infectious bronchitis virus infection.

Cytotoxic T lymphocyte (CTL) activity to infectious bronchitis virus (IBV) was examined at regular intervals between 3 and 30 days post infection (p.i.). The maximal CTL lysis of target cells infected with IBV with 82% was detected at 10 days p.i. The specific CTL activity began to decrease only after viral loads, which peaked at day 8 p.i. in both kidneys and lungs, started to decline. Therefore, the CTL response correlated with elimination of acute infection. IgM antibody did not appear until day 10 and levels peaked at day 12 p.i. whereas IgG antibody titers were detectable only by day 15 p.i., but continued to increase exponentially until day 30 p.i., the last day examined. IBV specific CTL epitope(s) were mapped within the carboxyl terminal 120 amino acids of nucleocapsid protein. In vivo inoculation of this fragment, as cDNA, induced protection against acute infection. The absence of viral neutralizing epitopes on the nucleocapsid protein would suggest that protection with known CTL eptiope(s) can be induced in the absence of neutralizing antibody.

Animals↗
PubMedDate not supplied

Cellular response of the respiratory tract of chickens to infection with Massachusetts 41 and Australian T infectious bronchitis viruses.

Cellular response of chickens to infection with infectious bronchitis virus (IBV) was investigated by lavage of the respiratory tract of five 2-week-old specific-pathogen-free (SPF) chickens at 2, 8, 24, 48, 72, and 96 hours postinfection (PI) with either Massachusetts 41 (IBV-M41) or Australian T (IBV-T) IBV. Tissue response was monitored by microscopic examination of trachea and lung from five non-lavaged infected chickens collected at the same intervals. The total number of cells recovered by lavage from IBV-M41-infected chickens was dramatically higher than the total number recovered from IBV-T-infected chickens and uninfected controls. By contrast, the total number of cells recovered from IBV-T-infected chickens was no higher than that of the uninfected chickens. Heterophils constituted the majority of inflammatory cells recovered from both IBV-M41-infected and IBV-T-infected chickens. Heterophil numbers in IBV-M41-infected chickens paralleled total cell-number recovery, whereas heterophil numbers in IBV-T-infected birds were no higher than those in uninfected chickens. The number of lymphocytes recovered from IBV-M41-infected chickens increased 72 hours PI and continued to increase for the duration of the study. Lymphocyte numbers in IBV-T-infected chickens exceeded those in uninfected chickens only at 96 hours PI. The number of lavage macrophages in IBV-M41-infected chickens increased earlier than the number of lymphocytes but later reached a plateau. IBV-T macrophage numbers did not exceed those of uninfected chickens. Tissue damage occurred most consistently in the trachea and occurred when lavage heterophil numbers were rising or at their peak. Lavage cell recovery and composition reflected tracheal mucosa inflammatory cell infiltrate.

Animals↗
PubMed1975

The ribonucleic acid of infectious bronchitis virus.

Analysis of the nucleic acid of infectious bronchitis virus by SDS polyacrylamide gel electrophoresis revealed an RNA of molecular weight 9.0 times 10-6 Daltons. The RNA was shown to have a sedimentation coefficient of 50.

Bronchitis↗
PubMed1983

Comparison of a microneutralisation test with ELISA and precipitin tests for detection of antibodies to infectious bronchitis virus in chickens.

A microneutralisation test for infectious bronchitis virus using virus antigens available in Australia, cell culture medium containing low concentrations of serum and an elevated incubation temperature is described. The technique was economical on reagents and of comparable sensitivity to the enzyme-linked immunosorbent assay (ELISA). The value of the microneutralisation, ELISA and precipitin tests in assessing the serological response of a flock of commercial chickens to vaccine and natural virus challenge was determined.

Animals↗
PubMedDate not supplied

Comparison of ciliary activity and virus recovery from tracheas of chickens and humoral immunity after inoculation with serotypes of avian infectious bronchitis virus.

Cross-protection tests with homologous and heterologous serotypes of infectious bronchitis virus (IBV) were used to compare ciliary activity and virus recovery from tracheas of chickens. Validation of this technique included correlating the neutralization indices of antiserum obtained from some infected birds. Chickens were inoculated intratracheally with either the JMK or Connecticut (Conn) serotype of IBV. Three weeks later, infected and uninfected groups were challenged by the same route with homologous and heterologous virus. The JMK strain provided immunity against homologous challenge and the Conn strain, as indicated by good ciliary activity and lack of challenge virus recovery. The Conn strain provided only homologous protection, as ciliostasis occurred and virus was recovered after challenge with the JMK strain. In each case, antiserum to immunizing virus neutralized only the homologous virus. Controls were uniformly susceptible and lacked neutralizing antibody. A similar experiment with the Ark 99 serotype and a recent isolate (397) of IBV revealed complete cross-protection of the tracheas. Antiserum to each virus neutralized the homologous and heterologous virus in each case in reciprocal tests. The results indicate that these two viruses are closely related. The complete agreement between ciliary activity and virus isolation indicates that ciliary activity is a reliable, objective criterion upon which tracheal immunity can be judged in cross-protection tests.

Animals↗
PubMedDate not supplied

Differentiation of avian infectious bronchitis virus isolates by thermal sensitivity.

Six isolates of avian infectious bronchitis virus (IBV) at different passage levels in the chicken embryo were tested for sensitivity at 56 C, with the following results: 1) isolates differed in thermal sensitivity; 2) virus was inactivated in a first-order exponential-kinetics 2-component fashion indicative of a heterogeneous population with a preponderance, 98% or more, of thermal-sensitive (S) virions over thermal-resistant (R) virons; 3) R virions 2-component populations were inactivated; 4) recovered R virions could be maintained in continuous passage in the chicken embryo as a one-component population by the limiting-dilution technique, although there was a progressive parallel increase in thermal sensitivity associated directly with the continuous passage; 5) growth curves of isolated one-component populations of R virions were quantitatively and in time sequence similar to curves of 2-component populations of continuous-passage virus.

Animals↗
PubMedDate not supplied

Variant serotypes of infectious bronchitis virus isolated from commercial layer and broiler chickens.

Twenty infectious bronchitis virus (IBV) field isolates obtained from commercial layer and broiler chickens in 1987 and 1988 were serotyped using the virus-neutralization (VN) test. Six different previously unrecognized variant serotypes were identified from a total of seven isolates from layer chickens. Only two isolates, both from Maine, were the same variant serotype. Variant serotypes also were recovered from layer flocks in Illinois and Washington and the province of Ontario, Canada. Two different variants were isolated from the same multi-age layer complex in Connecticut. Only one of 13 broiler chicken isolates was found to be a new variant serotype, that being from birds reared in Delaware. Cross-protection studies in specific-pathogen-free chickens indicated that vaccines containing the Holland, L-1, or Connaught strains of Massachusetts (Mass) combined with Arkansas produced a broader spectrum of immunity against challenge with the layer variants than Mass (Holland) alone or Mass (L-1) + Connecticut. All vaccines tested produced solid immunity (greater than or equal to 80% protection) against the broiler variant virus.

Animals↗
PubMedDate not supplied

Growth kinetics of embryo- and organ-culture adapted Beaudette strain of infectious bronchitis virus in embryonated chicken eggs.

Three Beaudette strains of infectious bronchitis virus (IBV) [two chicken-embryo trachea-culture-adapted (E71CET10 and E71CEK10CET30) and one embryo-adapted (E72)] were propagated in 10-day-old embryonated chicken eggs (CE) to investigate growth and lethality patterns. The E72 and E71CEK10CET30 viruses were similar in growth pattern as to logarithmic phase and maximum virus production, but 95% of the CE mortality with E72 virus occurred between 20 and 32 hours whereas with E71CEK10CET30 60% mortality occurred between 36 and 84 hours. The yield of the E71CET10 virus was minimum, with little lethality.

Animals↗
PubMed2006

Infectious bronchitis virus S1 gene sequence comparison is a better predictor of challenge of immunity in chickens than serotyping by virus neutralization.

Five strains of infectious bronchitis virus isolated from commercial chickens from the state of Pennsylvania, USA during the years 1998 and 1999 were studied. The strains were selected for cross-challenge in specific pathogen free chickens and virus neutralization in chick embryos on the basis of partial S1 sequence amino acid identity values. The partial sequences analysed spanned the hypervariable amino terminus region of S1 from amino acid residues 48 to 219, based on the Beaudette strain. Using their S1 identity values, the strains represented a continuum of genetic, and thus antigenic, relationships. When compared with strain PA/5083/99, strain PA/Wolgemuth/98 had high sequence identity (96%) followed by PA/171/99 (85%), PA/5344/98 (70%) and PA/1220/98 (34%). The method of Archetti and Horsfall was used for calculating antigenic relatedness values of virus neutralization tests. The same formula was also applied to the percentage protection values of cross-challenge tests to derive protective relatedness values among the strains. The antigenic relatedness values, protective relatedness values, and the partial S1 sequence identity values were then analysed. The findings indicated partial S1 sequence identity values were more strongly correlated with protective relatedness values and than antigenic relatedness values.

Amino Acid Sequence↗
PubMedDate not supplied

Attenuation, safety, and efficacy of an infectious bronchitis virus GA98 serotype vaccine.

In 1998, novel strains of infectious bronchitis virus (IBV) were identified in chickens from the southeastern United States and classified as a new serotype designated Georgia 98 (GA98). Because of the widespread nature of the GA98 virus in the southeastern United States and the lack of adequate protection with the DE072 vaccine, we developed a specific vaccine for the GA98 serotype. The GA98/0470/98 isolate of IBV was passaged in embryonating chicken eggs 70 times, and attenuation of the virus was determined in specific-pathogen-free chicks. Pass 70 of the GA98/0470/98 strain of IBV when given at 1 day of age by coarse spray and at 14 days of age in the drinking water at 1 x 10(4.5) 50% embryo infectious dose/bird protected against the homologous GA98 challenge as well as provided good protection against the DE072-type virus. In addition, the vaccine was shown to be adequately attenuated and safe at a 10x dosage.

Animals↗
PubMed2001

cis-acting sequences required for coronavirus infectious bronchitis virus defective-RNA replication and packaging.

The parts of the RNA genome of infectious bronchitis virus (IBV) required for replication and packaging of the RNA were investigated using deletion mutagenesis of a defective RNA (D-RNA) CD-61 (6.1 kb) containing a chloramphenicol acetyltransferase reporter gene. A D-RNA with the first 544, but not as few as 338, nucleotides (nt) of the 5' terminus was replicated; the 5' untranslated region (UTR) comprises 528 nt. Region I of the 3' UTR, adjacent to the nucleocapsid protein gene, comprised 212 nt and could be removed without impairment of replication or packaging of D-RNAs. A D-RNA with the final 338 nt, including the 293 nt in the highly conserved region II of the 3' UTR, was replicated. Thus, the 5'-terminal 544 nt and 3'-terminal 338 nt contained the necessary signals for RNA replication. Phylogenetic analysis of 19 strains of IBV and 3 strains of turkey coronavirus predicted a conserved stem-loop structure at the 5' end of region II of the 3' UTR. Removal of the predicted stem-loop structure abolished replication of the D-RNAs. D-RNAs in which replicase gene 1b-derived sequences had been removed or replaced with all the downstream genes were replicated well but were rescued poorly, suggesting inefficient packaging. However, no specific part of the 1b gene was required for efficient packaging.

3' Untranslated Regions↗