The S1 glycoprotein but not the N or M proteins of avian infectious bronchitis virus induces protection in vaccinated chickens

Decreased neutralizing antigenicity in IBV S1 protein expressed from mammalian cells

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The recombinant infectious bronchitis virus (IBV) S1 protein was highly glycosylated and many complex N-glycans were attached on the surface.

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The recombinant S1 protein elicited antibodies against IBV S1 protein, but most of the antibodies could not neutralize IBV.

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The results indicated that the recombinant S1 may not be able to display neutralizing epitopes by losing native conformation or masking by glycan.

We evaluated the antigenicity of recombinant infectious bronchitis virus (IBV) S1 protein expressed in mammalian cells. Recombinant S1 was expressed as a secreted protein fused with a trimerization motif peptide, then purified using Ni Sepharose. The purified protein was analyzed by Western blotting, mixed with oil adjuvant, and administered to 29-day-old specific-pathogen-free chickens. Six weeks after immunization, anti-IBV neutralizing titer and anti-S1 ELISA titer were determined; immunized chickens then were inoculated with IBV via the trachea and ciliary activity was observed. Results showed that the recombinant S1 protein was highly glycosylated, and the neutralizing antigenicity of recombinant S1 protein was lower than that of inactivated virus. However, anti-S1 ELISA indicated that the recombinant S1 protein induced antibodies against S1. These results suggest that the recombinant S1 may retain non-neutralizing epitopes but have unnatural glycosylation pattern and conformation, resulting in lacking neutralizing conformational epitopes. In conclusion, the neutralizing antigenicity of recombinant S1 protein expressed from mammalian cells was decreased, and was not sufficient to induce neutralizing antibodies.

Analysis of the S1 gene of the avian infectious bronchitis virus (IBV) reveals changes in the IBV genetic groups circulating in southern Thailand

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Two IBV clusters in southern Thailand were the indigenous THA001 and QX-like viruses.

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The THA001-type viruses were predominant between 2008 and 2009.

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The QX-like IBV viruses replaced the THA001-type from 2009 to 2013.

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Single isolates related to Massachusetts and 4/91 viruses were also detected.

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Native chickens may have contributed to IB epidemiology.

The new variants of the avian infectious bronchitis virus (IBV) produce a range of symptoms and cause global economic losses to the poultry industry. We investigated the S1 glycoprotein of 24 recent IBV isolates from chickens and demonstrated that two predominant genetic groups were circulating in southern Thailand between 2008 and 2013. Seven IBV variants, isolated from 2008 to 2009, were clustered in the Thailand THA001 group I while 15 IBV variants, isolated from 2009 to 2013, were classified into the QX-like group II. Moreover, a single isolate from a broiler was categorized into the Massachusetts-type, and an isolate from a layer belonged to the 4/91 type virus. Interestingly, both the IBV groups I and II were isolated from native chickens (62.5%) and caused a range of symptoms. Our results indicate that the QX-like viruses were predominant after 2009, replacing the THA001 type viruses. Furthermore, native chickens may contribute to the epidemiology of IB.

Progress and challenges toward the development of vaccines against avian infectious bronchitis

Avian infectious bronchitis (IB) is a widely distributed poultry disease that has huge economic impact on poultry industry. The continuous emergence of new IBV genotypes and lack of cross protection among different IBV genotypes have been an important challenge. Although live attenuated IB vaccines remarkably induce potent immune response, the potential risk of reversion to virulence, neutralization by the maternal antibodies, and recombination and mutation events are important concern on their usage. On the other hand, inactivated vaccines induce a weaker immune response and may require multiple dosing and/or the use of adjuvants that probably have potential safety risks and increased economic burdens. Consequently, alternative IB vaccines are widely sought. Recent advances in recombinant DNA technology have resulted in experimental IB vaccines that show promise in antibody and T-cells responses, comparable to live attenuated vaccines. Recombinant DNA vaccines have also been enhanced to target multiple serotypes and their efficacy has been improved using delivery vectors, nanoadjuvants, and in ovo vaccination approaches. Although most recombinant IB DNA vaccines are yet to be licensed, it is expected that these types of vaccines may hold sway as future vaccines for inducing a cross protection against multiple IBV serotypes.

Pathogenicity and molecular characteristics of infectious bronchitis virus (IBV) strains isolated from broilers showing diarrhoea and respiratory disease

Abstract 1. The possibility that infectious bronchitis virus (IBV) variants isolated from broilers with enteric and respiratory problems have a different tropism and pathological outcome from those IBV strains causing classical respiratory disease was investigated. 2. IBV variants were isolated from broiler flocks with enteric and respiratory problems in two regions of Brazil. The USP-10 isolate, of enteric origin, was inoculated via the oral oroculonasal routes into IBV-antibody-free broilers and specific pathogen-free (SPF) chickens to determine tissue tropism and pathogenicity and compared with an IBV variant (USP-50) isolated from chickens showing signs of respiratory disease only. 3. Both USP-10 and USP-50 strains caused similar pathological patterns by either route of inoculation. Both variants were detected in respiratory and non-respiratory tissues, including the kidney, intestine and testis. 4. Broilers were more susceptible to infection than SPF chickens, and seroconversion was detected in all of the chicks.

Phylodynamic analysis of avian infectious bronchitis virus in South America

Infectious bronchitis virus (IBV) is a coronavirus of chickens that causes great economic losses to the global poultry industry. The present study focuses on South American IBVs and their genetic relationships with global strains. We obtained full-length sequences of the S1 coding region and N gene of IBV field isolates from Uruguay and Argentina, and performed Phylodynamic analysis to characterize the strains and estimate the time of the most recent common ancestor. We identified two major South American genotypes, which were here denoted South America I (SAI) and Asia/South America II (A/SAII). The SAI genotype is an exclusive South American lineage that emerged in the 1960s. The A/SAII genotype may have emerged in Asia in approximately 1995 before being introduced into South America. Both SAI and A/SAII genotype strains clearly differ from the Massachusetts strains that are included in the vaccine formulations being used in most South American countries.

High-level protein expression following single and dual gene cloning of infectious bronchitis virus N and S genes using baculovirus systems

Baculovirus is an efficient system for the gene expression that can be used for gene transfer to both insect and different vertebrate hosts. The nucleocapsid gene (N) of the infectious bronchitis virus was cloned in a baculovirus expression system for insect cell expression. Dual expression vectors containing IBV N and spike (S) proteins of the avian infectious bronchitis virus were engineered under the control of human and murine cytomegalovirus immediate-early enhancer/promoter elements in combination with the baculoviral polyhedrin and p10 promoters for simultaneous expression in both vertebrate and insect cells. Transduction of the N gene in the insect Sf9 cells revealed a high level of protein expression. The expressed protein, used in ELISA, effectively detected chicken anti-IBV antibodies with high specificity. Transduction of mammalian and avian cells with BacMam viruses revealed that dual expression cassettes yielded high levels of protein from both transcription units.

The avian coronavirus spike protein

Avian coronaviruses of the genus Gammacoronavirus are represented by infectious bronchitis virus (IBV), the coronavirus of chicken. IBV causes a highly contagious disease affecting the respiratory tract and, depending on the strain, other tissues including the reproductive and urogenital tract. The control of IBV in the field is hampered by the many different strains circulating worldwide and the limited protection across strains due to serotype diversity. This diversity is believed to be due to the amino acid variation in the S1 domain of the major viral attachment protein spike. In the last years, much effort has been undertaken to address the role of the avian coronavirus spike protein in the various steps of the virus' live cycle. Various models have successfully been developed to elucidate the contribution of the spike in binding of the virus to cells, entry of cell culture cells and organ explants, and the in vivo tropism and pathogenesis. This review will give an overview of the literature on avian coronavirus spike proteins with particular focus on our recent studies on binding of recombinant soluble spike protein to chicken tissues. With this, we aim to summarize the current understanding on the avian coronavirus spike's contribution to host and tissue predilections, pathogenesis, as well as its role in therapeutic and protective interventions.

BacMam virus-based surface display of the infectious bronchitis virus (IBV) S1 glycoprotein confers strong protection against virulent IBV challenge in chickens

Avian infectious bronchitis virus (IBV) is associated with production inefficiencies in domestic fowl, and causes massive economic losses to the poultry industry worldwide. Progress has been made in designing novel and efficient candidate vaccines to control IBV infection. BacMam virus, a modified baculovirus mediating transgene expression under the control of a mammalian promoter, has emerged as a versatile and safe vector during vaccine development. In previous work, we generated the BacMam virus Ac-CMV-S1, which expressed the S1 glycoprotein of IBV-M41. We showed that Ac-CMV-S1 induced excellent cellular immunity, but did not confer adequate protection in chickens compared with the conventional inactivated vaccine. In the current study, we generated an improved BacMam virus, BV-Dual-S1. This virus displayed the S1 glycoprotein on the baculovirus envelope, and was capable of expressing it in mammalian cells. BV-Dual-S1 elicited stronger humoral and cell-mediated immune responses, and showed greater capacity for induction of cytotoxic T lymphocyte responses, compared with Ac-CMV-S1 in specific pathogen-free chickens. A significant difference was not observed for protection rates between chickens immunized with BV-Dual-S1 (83%) or inactivated vaccine (89%) following challenge with virulent IBV-M41. Our findings show that the protective efficacy of BV-Dual-S1 could be significantly enhanced by baculovirus display technology. BacMam virus-based surface display strategies could serve as effective tools in designing vaccines against IB and other infectious diseases.

Cell-mediated immune responses in the head-associated lymphoid tissues induced to a live attenuated avian coronavirus vaccine

Humoral immunity is important for controlling viral diseases of poultry, but recent studies have indicated that cytotoxic T cells also play an important role in the immune response to infectious bronchitis virus (IBV). To better understand the cell mediated immune responses to IBV in the mucosal and systemic immune compartments chickens were ocularly vaccinated with IBV. This induced a lymphocyte expansion in head-associated lymphoid tissues (HALT) and to a lesser extent in the spleen, followed by a rapid decline, probably due to homing of lymphocytes out of these organs and contraction of the lymphocyte population. This interpretation was supported by observations that changes in mononuclear cells were mirrored by that in CD3(+)CD44(+) T cell abundance, which presumably represent T effector cells. Increased interferon gamma (IFN-γ) expression was observed in the mucosal immune compartment, i.e., HALT, after primary vaccination, but shifted to the systemic immune compartment after boosting. In contrast, the expression of cytotoxicity-associated genes, i.e., granzyme A (GZMA) and perforin mRNA, remained associated with the HALT after boosting. Thus, an Ark-type IBV ocular vaccine induces a central memory IFN-γ response in the spleen while the cytotoxic effector memory response, as measured by GZMA and perforin mRNA expression, remains associated with CALT after boosting.

Development and characterization of a recombinant infectious bronchitis virus expressing the ectodomain region of S1 gene of H120 strain

Infectious bronchitis (IB), caused by infectious bronchitis virus (IBV), is a highly contagious chicken disease, and can lead to serious economic losses in poultry enterprises. The continual introduction of new IBV serotypes requires alternative strategies for the production of timely and safe vaccines against the emergence of variants. Modification of the IBV genome using reverse genetics is one way to generate recombinant IBVs as the candidates of new IBV vaccines. In this study, the recombinant IBV is developed by replacing the ectodomain region of the S1 gene of the IBV Beaudette strain with the corresponding fragment from H120 strain, designated as rBeau-H120(S1e). In Vero cells, the virus proliferates as its parental virus and can cause syncytium formation. The peak titer would reach 10(5.9) 50% (median) tissue culture infective dose/mL at 24 h post-infection. After inoculation of chickens with the recombinant virus, it demonstrated that rBeau-H120(S1e) remained nonpathogenic and was restricted in its replication in vivo. Protection studies showed that vaccination with rBeau-H120 (S1e) at 7-day after hatch provided 80% rate of immune protection against challenge with 10(3) 50% embryos infection dose of the virulent IBV M41 strain. These results indicate that rBeau-H120 (S1e) has the potential to be an alternative vaccine against IBV based on excellent propagation property and immunogenicity. This finding might help in providing further information that replacement of the ectodomain fragment of the IBV Beaudette S1 gene with that from a present field strain is promising for IBV vaccine development.

Assembly and immunogenicity of coronavirus-like particles carrying infectious bronchitis virus M and S proteins

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We generate IBV VLPs carrying M and S proteins using recombinant baculovirus.

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The VLPs elicit humoral immune responses comparable to inactivated IBV in mice and chickens.

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The VLPs elicit higher cellular immune responses than inactivated IBV in mice.

Infectious bronchitis virus (IBV) as an avian coronavirus is still posing a persistent and imminent threat to the poultry industry worldwide. Here we report that transfection of Sf9 cells with a single recombinant baculovirus encoding M and S proteins resulted in the assembly of IBV VLPs; this is the first report that S protein plus M protein alone were able to be assembled into VLPs for coronaviruses. We further showed that the generated IBV VLPs could induce humoral immune responses in a level comparable to that of inactivated IBV vaccine, and more importantly the IBV VLPs could elicit significantly higher cellular immune responses than the inactivated IBV vaccine. In summary, the assembly of IBV VLPs with M and S proteins provided a simple strategy for generating VLPs for coronaviruses, and the generated IBV VLPs laid a feasible foundation for the development of an effective vaccine against infection of IBV in the future.

The required sample size in vaccination-challenge experiments with infectious bronchitis virus, a meta-analysis

For statistical, animal welfare and financial reasons the choice of the number of chickens per group in experiments is important. This estimation, together with the number of tracheal organ cultures (TOCs) that need to be examined from each chicken in order to assess protection, should be based on the difference in level of protection that one would like to be able to detect (effect size), the expected variability of the results between and within the chickens, the desired confidence level and the power of the study. To obtain data that would facilitate this estimation, a meta-analysis was performed on the data from 18 infectious bronchitis virus (IBV) vaccination-challenge experiments performed at the Dutch Animal Health Service Deventer, the Netherlands (GD) in order to determine and quantify the source of variation in the mean level of protection of different groups. For the calculations, 137 groups of chickens were subdivided into 10 clusters based on age (young or adult), vaccination (none, homologous or heterologous), challenge (IBV or mock infected) and location of vaccination (isolator at GD or in the field). The results were used to estimate the required number of chickens per group for the different clusters using 2, 5 or 10 TOCs per chicken to be able to detect effect sizes of 6.25%, 12.5%, 25% and 50% between groups of chickens with 95% confidence (P<0.05) and 80% power. The number of chickens that was required for the mentioned effect sizes varied greatly from 2 to 650. This meta-analysis provided data that allow research workers to estimate the number of chickens that should be included in each group in order to obtain reliable results based on particular combinations of infectious bronchitis vaccination and challenge strains as defined by the presented clusters.

Association of the chicken MHC B haplotypes with resistance to avian coronavirus

Clinical respiratory illness was compared in five homozygous chicken lines, originating from homozygous B2, B8, B12 and B19, and heterozygous B2/B12 birds after infection with either of two strains of the infectious bronchitis virus (IBV). All chickens used in these studies originated from White Leghorn and Ancona linages. IBV Gray strain infection of MHC homozygous B12 and B19 haplotype chicks resulted in severe respiratory disease compared to chicks with B2/B2 and B5/B5 haplotypes. Demonstrating a dominant B2 phenotype, B2/B12 birds were also more resistant to IBV. Respiratory clinical illness in B8/B8 chicks was severe early after infection, while illness resolved similar to the B5 and B2 homozygous birds. Following M41 strain infection, birds with B2/B2 and B8/B8 haplotypes were again more resistant to clinical illness than B19/B19 birds. Real time RT-PCR indicated that infection was cleared more efficiently in trachea, lungs and kidneys of B2/B2 and B8/B8 birds compared with B19/B19 birds. Furthermore, M41 infected B2/B2 and B8/B8 chicks performed better in terms of body weight gain than B19/B19 chicks. These studies suggest that genetics of B defined haplotypes might be exploited to produce chicks resistant to respiratory pathogens or with more effective immune responses.

Fine level epitope mapping and conservation analysis of two novel linear B-cell epitopes of the avian infectious bronchitis coronavirus nucleocapsid protein

The nucleocapsid (N) protein of the infectious bronchitis virus (IBV) may play an essential role in the replication and translation of viral RNA. The N protein can also induce high titers of cross-reactive antibodies and cell-mediated immunity, which protects chickens from acute infection. In this study, we generated two monoclonal antibodies (mAbs), designated as 6D10 and 4F10, which were directed against the N protein of IBV using the whole viral particles as immunogens. Both of the mAbs do not cross react with Newcastle disease virus (NDV), infectious laryngotracheitis virus (ILTV) and subtype H9 avian influenza virus (AIV). After screening a phage display peptide library and peptide scanning, we identified two linear B-cell epitopes that were recognized by the mAbs 6D10 and 4F10, which corresponded to the amino acid sequences (242)FGPRTK(247) and (195)DLIARAAKI(203), respectively, in the IBV N protein. Alignments of amino acid sequences from a large number of IBV isolates indicated that the two epitopes, especially (242)FGPRTK(247), were well conserved among IBV strains. This conclusion was further confirmed by the relationships of 18 heterologous sequences to the 2 mAbs. The novel mAbs and the epitopes identified will be useful for developing diagnostic assays for IBV infections.

Molecular analysis of the 793/B serotype of infectious bronchitis virus in Great Britain

Since the winter of 1990/91 respiratory disease of poultry in Great Britain has commonly been associated with the 793/B (or 4/91) serotype of infectious bronchitis virus (IBV). We have sequenced a variable part of the S1 region of the spike protein (5) gene. Comparison of up to 270 nucleotides of 12 British 793/B isolates, obtained in 1991 and 1993, revealed 94 to 100% nucleotide identity with each other. Eleven of them fell into one of two subgroups, A and B, one isolate forming subgroup C. Identity within subgroups A and B was > 98%. The whole S1 gene sequence (1617 nucleotides) was determined for five 793/B isolates, two from each of subgroups A and B and one from subgroup C; nucleotide identity between any two isolates was > 97%. A large proportion of the nucleotide differences corresponded to amino acid changes. The whole S1 amino acid sequence differed by 21 to 25% or more from that of all other published IBV sequences. This extensive difference has probably contributed to the persistence of the 793/B serotype in Britain even though het-erologous vaccines have been used. The finding that the 793/B isolates could be placed into three subgroups suggests that either (a) they had diverged from a common progenitor present, but undetected, in Britain prior to 1990/91 or (b) at least three different strains of the 793/B serotype had entered Britain in or prior to 1990/91.

Relationship between sequence variation in the S1 spike protein of infectious bronchitis virus and the extent of cross-protection in vivo

The notion that the S1 subunit of the spike glycoprotein (S) of infectious bronchitis virus (IBV) is the major inducer of protective immunity has been examined. Groups of 10 1-day-old chicks were vaccinated with isolate UK/6/82 and challenged in-tranasally 3 or 6 weeks later with strains whose S1 protein differed from that of UK/6/82 to different extents: NL/D207/79, UK/142/86 and UK/167/84 (2%), UK/123/82 (4%), UK/918/67 (19%), USA/M41/41 and Portugal/322/82 (20%; both of the Massachusetts serotype), and NL/D1466/79 (49%). Four days after challenge tracheas were removed and observed for ciliary activity. Overall, the degree of cross-protection induced by UK/6/82 diminished as the similarity of the S1 proteins diminished, although in only two cases was the protection induced statistically less (P< 0.10) against the heterologous isolates than against the homologous strain. Even when a group as a whole was poorly protected against heterologous challenge, some individual chicks, including some challenged with D1466, exhibited high protection of the trachea. Conversely, in groups where protection was high overall, a few individuals were poorly protected. The results broadly support the view that differences in the sequence of the S1 protein do contribute to the ability of an IBV strain to break through the immunity induced by another strain. However, they also indicate that some conserved sequences in S1 and/or epitopes in the other, less variable, proteins also contribute to immunity. Moreover, individual chicks can differ greatly in their response to vaccination with IBV, a factor which should not be overlooked.

Cross-reactive cellular immune responses in chickens vaccinated with live infectious bronchitis virus vaccine

Two-week-old chickens were vaccinated intra-nasally with a live infectious bronchitis virus (IBV) vaccine (H120). On days 4, 7, 11 and 14 post-vaccination (p.v.) spleen mononuclear cells (MNC) prepared from control and vaccinated chickens were stimulated in vitro with homologous (strain M41) and heterologous (strains 7 and 793/B) virus antigens. Antigen-specific lymphoproliferation and interleukin-2 (IL-2) and interferon-y (IFN) production were used to measure cross-reactive cell mediated immune responses. In antigen-specific lymphoproliferation assays, it was found that while 4/16 vaccinated birds responded to the homologous antigen, only one responded to an heterologous antigen (strain 7). However, IL-2 production was seen in the supernatants of spleen MNC from vaccinated chickens stimulated with all three antigens. Production of IFN was also demonstrated in samples stimulated with the homologous and one heterologous (strain 7) antigen. Thus it appears that, following vaccination of chickens with live IBV vaccine, cross-reactive cellular immune responses occur that vary in magnitude with the strain of IBV used for in vitro stimulation.

Bioinformatics and evolutionary insight on the spike glycoprotein gene of QX-like and Massachusetts strains of infectious bronchitis virus

Background

Infectious bronchitis virus (IBV) is a Gammacoronavirus of the family Coronaviridae and is a causative agent of an economically important disease in poultry. The spike glycoprotein of IBV is essential for host cell attachment, neutralization, and is involved in the induction of protective immunity. Previously obtained sequence data of the spike gene of IBV QX-like and Massachusetts strains were subjected to bioinformatics analysis.

Findings

On analysis of potential phosphorylation sites, the Ser542 and Ser563 sites were not present in Massachusetts strains, while QX-like isolates did not have the Ser534 site. Massachusetts and QX-like strains showed different cleavage site motifs. The N-glycosylation sites ASN-XAA-SER/THR-55, 147, 200 and 545 were additionally present in QX-like strains. The leucine-rich repeat regions in Massachusetts strains consisted of stretches of 63 to 69 amino acids, while in the QX-like strains they contained 59 amino acids in length. An additional palmitoylation site was observed in CK/SWE/082066/2010 a QX-like strain. Primary structure data showed difference in the physical properties and hydrophobic nature of both genotypes. The comparison of secondary structures revealed no new structural domains in the genotypic variants. The phylogenetic analyses based on avian and mammalian coronaviruses showed the analysed IBV as closely related to turkey coronaviruses and distantly related to thrush and munia coronaviruses.

Conclusion

The study demonstrated that spike glycoprotein of the Massachusetts and the QX-like variants of IBV are molecularly distinct and that this may reflect in differences in the behavior of these viruses in vivo.

Application of purified recombinant antigenic spike fragments to the diagnosis of avian infectious bronchitis virus infection

The spike (S) protein, containing two subunits, S1 and S2, is the major immunity-eliciting antigen of avian infectious bronchitis virus (IBV), a highly contagious disease of chickens. Several immunogenic regions, mainly located within the S1 subunit, have been identified. Nonetheless, these immune-dominant regions were defined using selected monoclonal antibodies or using a short peptide approach that involves only certain limited regions of the S protein. In addition, some immune-dominant regions are located in hypervariable regions (HVRs) which are not present in all serotypes. Hence, the aim of this study was to determine a broader range of antigenic regions that have strong antibody eliciting ability; these could then be applied for development of an IBV-diagnostic tool. Initially, the S1 and part of the S2 subunit protein (24-567 amino acids) were expressed as five fragments in prokaryotic system. The antigenicity was confirmed using IBV immunized sera. Performance of the S subfragments was evaluated by ELISA using a panel of field chicken sera with known IBV titres determined by a commercial kit. This indicated that, among the five antigenic recombinant proteins, the region S-E showed the highest specificity and sensitivity, namely 95.38 % and 96.29 %, respectively. The κ value for the in-house ELISA using the S-E fragment compared to a commercial kit was 0.9172, indicating a high agreement between these two methods. As region S-E harbors strong immunogenicity within the spike protein, it has the potential to be exploited as an antigen when developing a cost-effective ELISA-based diagnosis tool.

Emergence of novel strains of avian infectious bronchitis virus in Sweden

Infectious bronchitis virus (IBV) causes avian infectious bronchitis, an important disease that produces severe economic losses in the poultry industry worldwide. Recent IBV infections in Sweden have been associated with poor growth in broilers, drop in egg production and thin egg shells in layers. The complete spike gene of selected isolates from IBV cases was amplified and sequenced using conventional RT-PCR. Nucleotide and amino acid sequence comparisons have shown that the recent isolates bear 98.97% genetic similarity with strains of the QX-like genotype. The phylogenetic analysis revealed that strains predominant in the nineties, which were of the Massachusetts type, have been replaced by D388/QX-like strains, however the evolutionary link could not be established. The homology between the two genotypes was 79 and 81%. Remarkably, a strong positive selection pressure was determined, mostly involving the S1 subunit of the S gene. This strong selective pressure resulted in recombination events, insertions and deletions in the S gene. Two new isolates generated from recombination were found with nucleotide sequence diverging 1.7–2.4% from the D388/QX-like branch, indicating the emergence of a new lineage. The study demonstrates a constant evolution of IBV that might be in relation to increased poultry farming, trade and vaccine pressure. The findings underscore the importance of continuous monitoring to control spread of infections, as well as to timely adjust diagnostic methods, molecular epidemiological studies, development and use of vaccines that are adapted to the changing disease scenario.

A recombinant avian infectious bronchitis virus expressing a heterologous spike gene belonging to the 4/91 serotype

We have shown previously that replacement of the spike (S) gene of the apathogenic IBV strain Beau-R with that from the pathogenic strain of the same serotype, M41, resulted in an apathogenic virus, BeauR-M41(S), that conferred protection against challenge with M41. We have constructed a recombinant IBV, BeauR-4/91(S), with the genetic backbone of Beau-R but expressing the spike protein of the pathogenic IBV strain 4/91(UK), which belongs to a different serogroup as Beaudette or M41. Similar to our previous findings with BeauR-M41(S), clinical signs observations showed that the S gene of the pathogenic 4/91 virus did not confer pathogenicity to the rIBV BeauR-4/91(S). Furthermore, protection studies showed there was homologous protection; BeauR-4/91(S) conferred protection against challenge with wild type 4/91 virus as shown by the absence of clinical signs, IBV RNA assessed by qRT-PCR and the fact that no virus was isolated from tracheas removed from birds primarily infected with BeauR-4/91(S) and challenged with IBV 4/91(UK). A degree of heterologous protection against M41 challenge was observed, albeit at a lower level.Our results confirm and extend our previous findings and conclusions that swapping of the ectodomain of the S protein is a precise and effective way of generating genetically defined candidate IBV vaccines.

Epidemiological survey and molecular characterization of avian infectious bronchitis virus in Brazil between 2003 and 2009

As part of an epidemiological study of infectious bronchitis virus (IBV) in Brazil, 252 samples from IBV-suspect flocks were tested and the IBV-positive samples were analysed by sequencing of hypervariable regions 1 and 2 of the S1 gene. A high prevalence of IBV variants was found and the sequence analysis of 41 samples revealed a high molecular similarity among the Brazilian isolates (from 90.2 to 100% and from 85.3 to 100% nucleotide and amino acid identity, respectively). The Brazilian isolates showed low genetic relationship with Massachusetts (63.4 to 70.7%), European (45.9 to 75.6%), American (49.3 to 76.4%) and other reference serotypes (67.5 to 78.8%). The Brazilian isolates branched into one unique cluster, separate from the reference serotypes used for infectious bronchitis control in other countries. The variants analysed in this work had a high similarity with all previously published Brazilian IBV isolates, suggesting the presence and high prevalence of a unique or predominant genotype circulating in Brazil. In addition, the virus neutralization test showed that the three Brazilian isolates analysed in the present study are antigenically related to one another but are different from the Massachusetts serotype. The present study shows that IBVs of a unique genotype can be associated with different clinical diseases, and that low genetic variation was detected in this genotype over a long period of time. The molecular characterization of the Brazilian variants isolated from 2003 to 2009 from different geographic regions of the country shows that only one predominant genotype is widespread in the Brazilian territory, denominated in this study as BR-I genotype.

Binding of avian coronavirus spike proteins to host factors reflects virus tropism and pathogenicity

The binding of viruses to host cells is the first step in determining tropism and pathogenicity. While avian infectious bronchitis coronavirus (IBV) infection and avian influenza A virus (IAV) infection both depend on α2,3-linked sialic acids, the host tropism of IBV is restricted compared to that of IAV. Here we investigated whether the interaction between the viral attachment proteins and the host could explain these differences by using recombinant spike domains (S1) of IBV strains with different pathogenicities, as well as the hemagglutinin (HA) protein of IAV H5N1. Protein histochemistry showed that S1 of IBV strain M41 and HA of IAV subtype H5N1 displayed sialic acid-dependent binding to chicken respiratory tract tissue. However, while HA bound with high avidity to a broad range of α2,3-linked sialylated glycans, M41 S1 recognized only one particular α2,3-linked disialoside in a glycan array. When comparing the binding of recombinant IBV S1 proteins derived from IBV strains with known differences in tissue tropism and pathogenicity, we observed that while M41 S1 displayed binding to cilia and goblet cells of the chicken respiratory tract, S1 derived from the vaccine strain H120 or the nonvirulent Beaudette strain had reduced or no binding to chicken tissues, respectively, in agreement with the reduced abilities of these viruses to replicate in vivo. While the S1 protein derived from the nephropathogenic IBV strain B1648 also hardly displayed binding to respiratory tract cells, distinct binding to kidney cells was observed, but only after the removal of sialic acid from S1. In conclusion, our data demonstrate that the attachment patterns of the IBV S proteins correlate with the tropisms and pathogenicities of the corresponding viruses.

Identification and characterization of a neutralizing-epitope-containing spike protein fragment in turkey coronavirus

Little is known about the neutralizing epitopes in turkey coronavirus (TCoV). The spike (S) protein gene of TCoV was divided into 10 fragments to identify the antigenic region containing neutralizing epitopes. The expression and antigenicity of S fragments was confirmed by immunofluorescence antibody (IFA) assay using an anti-histidine monoclonal antibody or anti-TCoV serum. Polyclonal antibodies raised against expressed S1 (amino acid position 1 to 573 from start codon of S protein), 4F/4R (482-678), 6F/6R (830-1071), or Mod4F/Epi4R (476-520) S fragment recognized native S1 protein and TCoV in the intestines of TCoV-infected turkey embryos. Anti-TCoV serum reacted with recombinant 4F/4R, 6F/6R, and Mod4F/Epi4R in a western blot. The results of a virus neutralization assay indicated that the carboxyl terminal region of the S1 protein (Mod4F/Epi4R) or the combined carboxyl terminal S1 and amino terminal S2 protein (4F/4R) possesses the neutralizing epitopes, while the S2 fragment (6F/6R) contains antigenic epitopes but not neutralizing epitopes.

Genotyping of newly isolated infectious bronchitis virus isolates from northeastern Georgia

Sixteen infectious bronchitis virus (IBV) field isolates obtained from vaccinated commercial broiler chickens showing clinical respiratory disease were characterized by reverse transcriptase-polymerase chain reaction and sequence analysis of the hypervariable region of the S1 spike glycoprotein gene. The genetic relationship among these variants and reference strains was determined by phylogenetic analysis and use of the basic local alignment search tool. All the isolates formed a distinct phylogenetic group with very short branched distances, suggesting that isolates had a similar origin. All the isolates showed 85% amino acid identity with recently described Australian isolates, particularly N1-62. Given that little was known about this new emergent IBV we have characterized five field isolates by sequencing the entire S1 gene. Multiple sequence alignment of deduced amino acid sequences with commonly used vaccine strains revealed that most substitutions occurred in the 53-148 amino acid region. A possible recombination site with N1-62 isolate was identified between amino acid residues 115-121. All the field isolates shared four or five out of seven amino acid residues with N1-62 in this region as opposed to Ark-DPI and Mass 41 reference strains, which shared only two residues. Results indicate that IBV isolates reported here can be considered as new IBV genotype.

Evaluation of recombinant fowlpox virus expressing infectious bronchitis virus S1 gene and chicken interferon-γ gene for immune protection against heterologous strains

A recombinant fowlpox virus (rFPV-IFNγS1) that co-expressed the infectious bronchitis virus (IBV) S1 gene and the chicken interferon-γ gene has been constructed. To evaluate the efficacy of the recombinant fowlpox virus vaccine against heterotypic IBV strains, 60 4-week-old Specific-Pathogen-Free (SPF) chickens were inoculated with this vaccine and 3 weeks post inoculation challenged with the homotypic IBV strain LX4 and the heterotypic IBV strains LHB, LHLJ04XI, LTJ95I and LSC99I. Antibodies against IBV were detected in vaccinated chickens 1-week post inoculation. The number of CD4(+) and CD8(+) T-lymphocytes in the peripheral blood increased rapidly in the vaccinated groups challenged with strains LX4, LHB and LHLJ04XI. There were significant differences in the number of CD4(+) and CD8(+) T-lymphocytes between the vaccinated groups challenged with strains LTJ95I and LSC99I and all the control groups. The morbidity was below 30% in vaccinated groups challenge with strains LX4, LHB and LHLJ04XI, but was 40% greater than that in the other groups. In addition, the lesions and the amount of virus shedding were less severe in the vaccinated groups challenged by strains LX4, LHB and LHLJ04XI when compared with the other groups, but there was no significant difference in the average body weight of the chickens in all groups (all p>0.05). These results indicate that the rFPV-IFNγS1 protected chickens against challenge with homotypic IBV strain LX4 and heterotypic strains LHLJ04XI and LHB.

Construction and immunogenicity of a recombinant fowlpox vaccine coexpressing S1 glycoprotein of infectious bronchitis virus and chicken IL-18

Infectious bronchitis virus (IBV) poses a major threat to the chicken industry worldwide. In this study, we developed a recombinant fowlpox virus (rFPV) vaccine expressing the IBV S1 gene and chicken interleukin-18 gene (IL-18), rFPV-S1/IL18. Recombinant plasmid pSY-S1/IL18 was constructed by cloning chicken IL-18 into fowlpox virus transfer plasmid containing S1 gene and transfected into the chicken embryo fibroblasts cell pre-infected with S-FPV-017 to generate rFPV-S1/IL18. Expression of the recombinant proteins was confirmed by RT-PCR and IFA. We also constructed the recombinant fowlpox virus rFPV-S1 without IL-18. One-day-old chickens were vaccinated by wing-web puncture with the two rFPVs, and the induced humoral and cellular responses were evaluated. There was a significant difference in ELISA antibody levels (P < 0.05) elicited by either rFPV-S1 or rFPV-S1/IL18. The ratios of CD4⁺ to CD8⁺ in chickens immunized with rFPV-S1/IL18 were significantly higher (P < 0.05) than in those immunized with rFPV-S1. All chickens immunized with rFPV-S1/IL18 were completely protected (20/20) after challenge with the virulent IBV HN99 strain 43 days after immunization, while only 15 out of 20 of the chickens immunized with the rFPV-S1 were protected. Our results show that the protective efficacy of the rFPV-S1 vaccine could be enhanced significantly by simultaneous expression of IL-18.

Identification of a novel linear B-cell epitope in the M protein of avian infectious bronchitis coronaviruses

This report describes the identification of a novel linear B-cell epitope at the C-terminus of the membrane (M) protein of avian infectious bronchitis virus (IBV). A monoclonal antibody (MAb) (designated as 15E2) against the IBV M protein was prepared and a series of 14 partially-overlapping fragments of the IBV M gene were expressed with a GST tag. These peptides were subjected to enzyme-linked immunosorbent assay (ELISA) and western blotting analysis using MAb 15E2 to identify the epitope. A linear motif, ¹⁹⁹FATFVYAK²⁰⁶, which was located at the C-terminus of the M protein, was identified by MAb 15E2. ELISA and western blotting also showed that this epitope could be recognized by IBV-positive serum from chicken. Given that 15E2 showed reactivity with the ¹⁹⁹FATFVYAK²⁰⁶ motif, expressed as a GST fusion protein, in both western blotting and in an ELISA, we proposed that this motif represented a linear B-cell epitope of the M protein. The ¹⁹⁹FATFVYAK²⁰⁶ motif was the minimal requirement for reactivity as demonstrated by analysis of the reactivity of 15E2 with several truncated peptides that were derived from the motif. Alignment and comparison of the 15E2-defined epitope sequence with the sequences of other corona-viruses indicated that the epitope is well conserved among chicken and turkey coronaviruses. The identified epitope should be useful in clinical applications and as a tool for the further study of the structure and function of the M protein of IBV.

Use of recombinant S1 spike polypeptide to develop a TCoV-specific antibody ELISA

Turkey coronavirus (TCoV) causes diarrhoea in young turkey poults but little is known about its prevalence in the field. To address this, a portion of the S1 region of the spike glycoprotein of TCoV carrying relevant B cell epitopes (amino acid positions 54-395) was cloned and expressed in Escherichia coli. This protein was purified and used to develop an indirect ELISA for detection of antibodies against TCoV. Using experimentally derived positive and negative turkey serum samples this ELISA showed high sensitivity (95%) and specificity (92%) for TCoV. To further evaluate the potential of the ELISA, 360 serum samples from commercial turkey farms in Ontario were tested for TCoV-specific antibodies using the recombinant TCoV ELISA. High seroprevalence of TCoV was found with 71.11% of breeders and 56.67% of meat turkeys testing seropositive. Although there was significant positive correlation with a TCoV-N protein-based ELISA, there was little to no correlation with the whole IBV antigen-based ELISA when field sera were tested for antibodies against TCoV.

Coadministration of chicken GM-CSF with a DNA vaccine expressing infectious bronchitis virus (IBV) S1 glycoprotein enhances the specific immune response and protects against IBV infection

Various approaches have been developed to improve the efficacy of DNA vaccination, such as the use of plasmids expressing cytokines as molecular adjuvants. The purpose of the present study was to determine whether co-administration of a plasmid containing a chicken granulocyte-macrophage colony-stimulating factor (GM-CSF) gene and a plasmid containing the S1 gene of infectious bronchitis virus (IBV) could enhance the immune response and protection efficacy in chickens against challenge by virulent IBV. Plasmids carrying the S1 gene of IBV (pVAX-S1) and the chicken GM-CSF gene (pVAX-chGM-CSF) were constructed. Seven-day-old chickens were injected intramuscularly with pVAX-S1, pVAX-chGM-CSF, or both and boosted 2 weeks later. Chickens were challenged with virulent IBV at 3 weeks after the booster immunization and observed for 2 weeks. The results showed that co-administration of pVAX-chGM-CSF led to a significant enhancement of humoral and cellular responses over that of vaccination with pVAX-S1 alone. In addition, vaccination with pVAX-chGM-CSF and pVAX-S1 provided 86.7% protection (13/15) against IBV challenge. In contrast, only 73.3% of the chickens were protected against IBV challenge by pVAX-S1 vaccination alone. These results strongly indicate that chGM-CSF can be used as a molecular adjuvant to enhance the protective immunity induced by an IBV-specific DNA vaccine.

Sequence of the spike protein of the Belgian B164S isolate of nephropathogenic infectious bronchitis virus

The sequence of the gene encoding the spike glycoprotein (S) of the 1984 Belgian nephropathogenic isolate B1648 has been determined and shown to encode a protein of 1171 amino acids. Comparison of the deduced amino acid sequence of the S1 (amino-terminal half) of S, which induces virus-neutralizing antibodies, with that of vaccinal strains D274, H120 and D1466 revealed that it differed from them by 21, 25 and 49%, respectively, and by 24 to 25% from the North American nephropathogenic isolates Gray and Holte. The deduced amino add sequence of the S2 (carboxy-terminal) half of S differed by 10 to 12% (25% from D1466).

Immune responses to structural proteins of avian infectious bronchitis virus

Chickens were vaccinated with live and inactivated infectious bronchitis virus (IBV), and antibody responses to the individual structural proteins, S1, S2, M and N, followed by ELISA and western blotting. All four structural proteins elicited an antibody response in chicks vaccinated with either live or inactivated IBV. The S1, S2 and N proteins elicited similar titres of antibodies following vaccination with live IBV, whereas the M glycoprotein elicited significantly lower titres. Time of appearance and the course of development of the S1, S2 and N ELISA antibodies were similar, being first detected 2 weeks after vaccination and coincided with appearance of virus neutralizing antibodies. The M antibodies were first detected 4 weeks after vaccination. S1, S2, and N antibody titres were significantly higher in chicks vaccinated at 14 days of age than in chicks vaccinated at either 1 or 7 days of age, and reached maximum levels 4 weeks after the second vaccination. The S1, S2 and N proteins induced cross-reactive antibodies, whereas the M glycoprotein induced antibodies of limited cross-reactivity. Titres of cross-reactive N antibodies were higher than titres of cross-reactive S1 and S2 antibodies, which were similar. Epitopes on the N and S2 proteins that gave rise to cross-reactive antibodies showed the same degree of conservation, whereas the cross-reactive S1 epitopes were marginally less conserved. Vaccination with inactivated virus induced significantly lower antibody titres and at least three vaccinations were necessary for induction of S1, S2, N and M antibodies in all chicks. The S2 glycoprotein was the most immunogenic structural protein following vaccination with inactivated virus. All four proteins induced cell-mediated immune responses in chicks vaccinated with live IBV as determined by a delayed type hypersensitivity response.

Isolation of 4/91 type of infectious bronchitis virus as a new variant in Japan and efficacy of vaccination against 4/91 type field isolate

Among field isolates of infectious bronchitis virus (IBV) from recent outbreaks, some isolates that were classified into the 4/91 genotype, by analysis of the S1 gene, have been confirmed to be a new variant in Japan. To elucidate the characteristics of these isolates, pathogenicity in chicks and the efficacy of vaccines against this new variant were examined. Severe respiratory symptoms were observed in 4-day-old specific pathogen free chicks inoculated with a 4/91 genotype isolate, either JP/Wakayama/2003 or JP/ Iwate/2005; body weights 3 wk after inoculation were significantly lower than those of chicks inoculated with a 4/91 vaccine strain. These 4/91 isolates were neutralized with serum from birds immunized with 4/91 vaccine. In a challenge-protection test, five groups of chicks were immunized with C78, TM-86w, H120, Kita-1, or 4/91 vaccines and then challenged with JP/Iwate/2005 4 wk after vaccination. A protective effect in the 4/91 and TM-86w vaccine groups was indicated by evaluation of the ciliostasis score of the trachea, the respiratory symptom score, and virus isolation from trachea swab samples after challenge. The results of this study suggested that the 4/91 type of IBV, which is virulent to chicks when compared to vaccine strains, has emerged as a new variant in Japan, and vaccines containing the 4/91 strain or the TM-86w strain could be effective for this variant.

The immunoreactivity of a chimeric multi-epitope DNA vaccine against IBV in chickens

Epitope-based vaccines designed to induce cellular immune response and antibody responses specific for infectious bronchitis virus (IBV) are being developed as a means for increasing vaccine potency. In this study, we selected seven epitopes from the spike (S1), spike (S2), and nucleocapsid (N) protein and constructed a multi-epitope DNA vaccine. The 7-day-old chickens were immunized intramuscularly with multi-epitope DNA vaccine encapsulated by liposome and boosted two weeks later, and were challenged by virulent IBV strain five weeks post booster. The results showed that multi-epitope DNA vaccine led to a dramatic augmentation of humoral and cellular responses, and provided up to 80.0% rate of immune protection. The novel immunogenic chimeric multi-epitope DNA vaccine revealed in this study provided a new candidate target for IBV vaccine development.

Pathogenicity of infectious bronchitis virus isolates from Ontario chickens

Infectious bronchitis (IB) is one of the important viral diseases of chickens, and in spite of regular vaccination, IB is a continuous problem in Canadian poultry operations. In an earlier study using sentinel chickens we determined the incidence of infectious bronchitis virus (IBV) in Ontario commercial layer flocks. The objective of this study was to determine the pathogenicity of 5 nonvaccine-related IBV isolates recovered from the sentinel birds. The clinical signs, gross, and histological lesions in specific pathogen-free chickens indicated that all 5 isolates caused mild lesions in the respiratory tract. An important finding of this study was the significantly lower average daily weight gain among virus-inoculated groups of chickens during the acute phase of infection. Based on sequences of part of the S1 gene IBV-ON2, IBV-ON3, and IBV-ON5 formed a cluster and they were closely related to strain CU-82792. IBV-ON4 had 98.7% identity with the strain PA/1220/9, a nephropathogenic variant.

Genetic diversity of avian infectious bronchitis virus isolates in Korea between 2003 and 2006

Thirty-three field isolates of avian infectious bronchitis virus (IBV) were recovered from commercial chicken flocks in Korea between 2003 and 2006 and were characterized phylogenetically by nucleotide sequence analysis of the IBV S1 gene hyper-variable region. Our phylogenetic analysis revealed that recent field isolates of IBV formed at least three distinct phylogenetic types, including K-I, K-II, and K-III. K-I type IBV consisted of indigenous, 13 IBV isolates which evolved from the Kr-EJ/95 strain and then separated into the lineages of type K-Ia and type K-Ib. K-II type IBV isolates (n = 19) were closely related to nephropathogenic IBV variants from China and Japan. The K-III type isolate (Kr/D064/05), first identified by this study, was closely related to enteric IBV variants from the Chinese strains that cause proventriculitis. Sequence comparisons showed amino acid differences of >27.5% between IBV types. The molecular epidemiologic characteristics of IBV field isolates are briefly discussed.

Sequence analysis of the gene coding for the S1 glycoprotein of infectious bronchitis virus (IBV) strains from New Zealand

Four new infectious bronchitis virus (IBV) strains (T6, K32, K43, and K87) were isolated from clinically infected chickens in New Zealand. These strains were compared with four strains (A, B, C, and D), which had circulated 25 years previously, by sequencing the gene coding for the S1 subunit of the spike glycoprotein. Analysis of the nucleotide and deduced amino acid sequences revealed that the eight strains from New Zealand are genetically related and share greater than 82.8% nucleotide and 79% amino acid homology within the S1 region. Strains T6, K43, and K87 were more than 99% homologous to previously described strains C and D. A fourth new strain (K32) was most closely related to the previously described B strain. Phylogenetic analysis of strains revealed that New Zealand strains were more closely related to Australian than European or North American strains. The New Zealand A strain shared 99.5% nucleotide and 98.7% amino acid homology with the Australian Vic S strain. Deduced amino acid sequence of the S1 glycoprotein indicated differences between strains that were, in general, consistent with virus neutralization patterns.

Molecular characterization of infectious bronchitis virus strains isolated from the enteric contents of Brazilian laying hens and broilers

Infectious bronchitis virus (IBV) is the causative agent of avian infectious bronchitis, which is characterized by respiratory, reproductive, and renal signs. However, the role of IBV as an enteric pathogen in still controversial. In Brazil, antigenic groups of IBV divergent from the Massachusetts serotype used for vaccination schedules in that country have already been demonstrated. The present study aimed to assess the different genotypes of IBV in Brazilian commercial poultry flocks by partial sequencing of the S1 amino-terminus coding region using enteric contents as samples and examine their relationship with the vaccine serotype currently in use. Samples of enteric contents were taken as pools of five birds from each of 18 poultry farms (17 broiler and one laying farm) from five Brazilian states between 2002 and 2006. Birds were presenting watery diarrhea and poor general condition but were without respiratory, renal, or reproductive signs. Conventional antibacterial and anticoccidial therapies were unsuccessful and, furthermore, all samples proved negative for rotavirus, reovirus, and astrovirus. Eleven IBV samples were isolated in embryonated eggs and resulted in S1 sequences. Phylogenetic analysis showed that these segregated into an exclusive cluster, close to serotype D274, but distant from Massachusetts. Mean amino acid identity amongst these Brazilian strains was 94.07%; amongst these and serotypes D274, 4/91, and Massachusetts, mean amino acid identity was 77.17%, 69.94%, and 68.93%, respectively. In conclusion, the presence of genotype variant strains of IBV in Brazilian poultry flocks has been demonstrated and might be the reason for the unsuccessful control of IBV in Brazil. Furthermore, these results also strengthen the implications of IBV in enteric diseases of poultry.

A Massachusetts prototype like coronavirus isolated from wild peafowls is pathogenic to chickens

Coronavirus infection was investigated in apparently healthy wild peafowls in Guangdong province of China in 2003, while severe acute respiratory syndrome (SARS) broke out there. No SARS-like coronavirus had been isolated but a novel avian coronavirus strain, Peafowl/GD/KQ6/2003 (KQ6), was identified. Sequence analysis revealed that KQ6 was an avian coronavirus infectious bronchitis virus (IBV), a member of coronavirus in group 3. The genome sequence of KQ6 had extremely high degree of identity with that of a Massachusetts prototype IBV M41. KQ6 was pathogenic to chickens but non-pathogenic to peafowls under experimental conditions. Seventeen out of fifty-four (31.48%) peafowl serum samples were tested positive for specific antibodies against IBV. Present results indicate that the peafowl isolate KQ6 is a Massachusetts prototype like coronavirus strain which undergoes few genetic changes and peafowl might have acted as a natural reservoir of IBV for very long time.

Coronavirus avian infectious bronchitis virus

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.

Variations in the nucleocapsid protein gene of infectious bronchitis viruses isolated in Korea

Fourteen infectious bronchitis viruses (IBVs) were isolated in Korea between 2001 and 2003 from chickens suspected to be infected with IBVs. The nucleocapsid (N) protein genes of the various IBVs were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and were cloned and sequenced, and the nucleotide and deduced amino acid sequences were compared with published sequences for non-Korean IBV strains. The Korean IBV isolates shared amino acid sequence similarity of between 89.2% (K203-02 and K1255-03) and 98.3% (K434-01 and K281-01) with each other and exhibited amino acid sequence similarity between 57.0% (K774-01 and V18/91) and 96.6% (K507-01 and JP8147) with non-Korean IBV strains. Phylogenetic analysis of the deduced N protein amino acid sequences resulted in the segregation of Korean IBV isolates into three different clusters, with cluster assignments differing for some of the isolates from those obtained with analysis of the S1 glycoprotein. Korean IBV isolates K069-01, K281-01, K434-01, K504-01, K774-01, K748-01, K044-02, K058-02, K161-02, K203-02, and K234-02 formed an independent cluster comprised only of Korean IBV isolates. Another Korean IBV isolate, K210-02, belonged to a cluster that included IBV strains isolated in USA, the Netherlands and China. Recent Korean IBV isolates K514-03 and K1255-03 grouped into a third distinct cluster related to a Chinese IBV strain. As deduced from phylogenetic analysis, some IBV isolates appear to have arisen from the recombination of IBV strains with different origins.

Molecular characterization of avian infectious bronchitis virus strains isolated in Colombia during 2003

Sixteen infectious bronchitis virus (IBV) isolates were recovered from broilers and layers from five geographic poultry regions in Colombia. The viruses were isolated from tracheas, lungs, and cecal tonsils of birds, previously vaccinated with the Massachusetts strain, that were showing respiratory signs. Further analysis of the IBV isolates was achieved by phylogenetic analysis comparing their deduced amino acid sequences in the hypervariable region 1 of the S1 gene with reference strains. Four unique genotype clusters containing isolates with indigenous genotypes were observed. One isolate was found to be the Connecticut genotype and three isolates were found to be the Massachusetts genotype.

Isolation of a variant infectious bronchitis virus in Australia that further illustrates diversity among emerging strains

Australian infectious bronchitis viruses (IBV) have undergone a separate evolution due to geographic isolation. Consequently, changes occurring in Australian IBV illustrate, independently from other countries, types of variability that could occur in emerging IBV strains. Previously, we have identified two distinct genetic groups of IBV, designated subgroups 1 and 2. IBV strains of subgroup 1 have S1 and N proteins that share a high degree of amino acid identity, 81 to 98% in S1 and 91 to 99% in N. Subgroup 2 strains possess S1 and N proteins that share a low level of identity with subgroup 1 strains: 54 to 62% in S1 and 60 to 62% in N. This paper describes the isolation and characterisation of a third, previously undetected genetic group of IBV in Australia. The subgroup 3 strains, represented by isolate chicken/Australia/N2/04, had an S1 protein that shared a low level of identity with both subgroups 1 and 2: 61 to 63% and 56 to 59%, respectively. However, the N protein and the 3′ untranslated region were similar to subgroup 1: 90 to 97% identical with the N protein of subgroup 1 strains. This N4/02 subgroup 3 of IBV is reminiscent of two other strains, D1466 and DE072, isolated in the Netherlands and in the USA, respectively. The emergence of the subgroup 3 viruses in Australia, as well as the emergence of subgroup 2 in 1988, could not be explained by any of the mechanisms that are currently considered to be involved in generation of IBV variants.

Long-term protection from SARS coronavirus infection conferred by a single immunization with an attenuated VSV-based vaccine

Although the recent SARS coronavirus (SARS-CoV) that appeared in 2002 has now been contained, the possibility of re-emergence of SARS-CoV remains. Due to the threat of re-emergence, the overall fatality rate of ∼10%, and the rapid dispersion of the virus via international travel, viable vaccine candidates providing protection from SARS are clearly needed. We developed an attenuated VSV recombinant (VSV-S) expressing the SARS coronavirus (SARS-CoV) spike (S) protein. In cells infected with this recombinant, S protein was synthesized, glycosylated at approximately 17 Asn residues, and transported via the Golgi to the cell surface. Mice vaccinated with VSV-S developed SARS-neutralizing antibody and were able to control a challenge with SARS-CoV performed at 1 month or 4 months after a single vaccination. We also demonstrated, by passive antibody transfer, that the antibody response induced by the vaccine was sufficient for controlling SARS-CoV infection. A VSV-vectored SARS vaccine could have significant advantages over other SARS vaccine candidates described to date.

S1 gene characteristics and efficacy of vaccination against infectious bronchitis virus field isolates from the United States and Israel (1996 to 2000)

The S1 genes of isolates of avian coronavirus infectious bronchitis virus (IBV) from commercial chickens in the US and Israel (20 isolates from each country) were studied using reverse transcription-polymerase chain reaction restriction fragment length polymorphism and sequencing. Partial sequences spanning the amino terminus region of S1 from amino acid residues 48 to 219, based on the Beaudette strain, were used for analysis. Phylogenetic clustering and high-sequence identity values were used to identify isolates that appeared to be derived from live IBV vaccines used in the two countries. Novel variant strains, unrelated by S1 sequencing and restriction fragment length polymorphism analyses to reference and vaccine strains, were also identified. Based on S1 sequence identity to available vaccines, the potential to use vaccination to control IBV infections was evaluated. Vaccination with commercial live strains Massachusetts (Mass), Arkansas (Ark) or DE/072/92, generally produced immunity against vaccine-related field isolates displaying high S1 sequence similarities (> or = 90%) to the respective vaccine strains. Immunization with a bivalent vaccine containing the Mass and Ark strains provided good cross-protection, averaging 81% against challenge with five variant isolates from the US having amino acid identity values ranging from 62 to 69% to Mass and from 68 to 83% to Ark, respectively. In contrast, the H120 vaccine strain induced low levels of protection, ranging from 25 to 58% against variant field isolates from Israel with amino acid identity values from 65 to 67%.