Isolation and characterization of GI-19/L1148-like infectious bronchitis virus in China

Ten infectious bronchitis viruses (IBVs) were isolated from diseased chicken flocks in China between 2018 and 2024. Phylogenetic, homology, and pairwise comparisons of the complete S1 gene revealed that the 10 isolates shared a close genetic relationship with the European L1148 vaccine strain. Complete genomic sequence of isolate I0317/22 confirmed this result. Inoculation of 1-day-old specific pathogen free (SPF) chickens with I0317/22 induced mild clinical signs. The virus replicated at low levels in most of the tissues, except in the respiratory and upper digestive (preventriculus) tracts. We speculate that the 10 isolates derived from the L1148 vaccine strain and spread with low pathogenicity within chicken flocks. In 1-day-old SPF chickens, inoculation with I0317/22 and vaccination with the Mycoplasma gallisepticum (MG) F vaccine strain demonstrated that the MG F vaccine did not promote I0317/22 replication. Similarly, challenge of the chickens inoculated with MG F after 28 days with strain I0305/19 did not enhance I0305/19 replication compared to the control group. However, inoculation with MG F suppressed the neutralizing antibody responses against I0317/22 and I0305/19. We hypothesize that MG F strain induced suppression of neutralizing antibodies by affecting the host immune response to IBV infection, thereby increasing susceptibility to other pathogens, such as Escherichia coli. This likely led to mixed infections where synergistic interactions between pathogens exacerbated disease severity beyond what would be expected under experimental conditions alone.

Challenges to the Poultry Industry: Current Perspectives and Strategic Future After the COVID-19 Outbreak

Poultry immunity, health, and production are several factors that challenge the future growth of the poultry industry. Consumer confidence, product quality and safety, types of products, and the emergence and re-emergence of diseases will continue to be major challenges to the current situation and the strategic future of the industry. Foodborne and zoonotic diseases are strictly linked with poultry. Eradication, elimination, and/or control of foodborne and zoonotic pathogens present a major challenge to the poultry industry. In addition, the public health hazards from consuming foods with high antibiotic residues will remain a critical issue. The theory of poultry production described in this review will not be limited to considering disease control. Rather, it will also incorporate the interconnection of the animals' health, welfare, and immunity. It is essential to know that chickens are not susceptible to intranasal infection by the SARS-CoV-2 (COVID-19) virus. Nevertheless, the COVID-19 pandemic will affect poultry consumption, transport, and the economics of poultry farming. It will also take into consideration economic, ethical, social dimensions, and the sustenance of the accomplishment of high environmental security. Stockholders, veterinarians, farmers, and all the partners of the chain of poultry production need to be more involved in the current situation and the strategic future of the industry to fulfill human demands and ensure sustainable agriculture. Thus, the present review explores these important tasks.

A highly pathogenic GI-19 lineage infectious bronchitis virus originated from multiple recombination events with broad tissue tropism

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The GI-19 strain was shown to be the dominant IBV lineage worldwide.

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Isolate I0305/19 belongs to GI-19 lineage.

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Isolate I0305/19 emerged through recombination events.

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Isolate I0305/19 is a highly nephropathogenic strain.

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Isolate I0305/19 showed broad tissue tropism in infected chickens.

In the present study, an IBV strain I0305/19 was isolated from a diseased commercial broiler flock in 2019 in China with high morbidity and mortality. The isolate I0305/19 was clustered together with viruses in sublineage D of GI-19 lineage on the basis of the complete S1 sequence analysis. Isolate I0305/19 and other GI-19 viruses isolated in China have the amino acid sequence MIA at positions 110–112 in the S protein. Further analysis based on the complete genomic sequence showed that the isolate emerged through at least four recombination events between GI-19 ck/CH/LJS/120848- and GI-13 4/91-like strains, in which the S gene was found to be similar to that of the GI-19 ck/CH/LJS/120848-like strain. Pathological assessment showed the isolate was a nephropathogenic IBV strain that caused high morbidity of 100 % and mortality of 80 % in 1-day-old specific-pathogen-free (SPF) chicks. The isolate I0305/19 exhibited broader tropisms in different tissues, including tracheas, lungs, bursa of Fabricius, spleen, liver, kidneys, proventriculus, small intestines, large intestines, cecum, and cecal tonsils. Furthermore, subpopulations of the virus were found in tissues of infected chickens; this finding is important in understanding how the virulent IBV strains can potentially replicate and evolve to cause disease. This information is also valuable for understanding the mechanisms of replication and evolution of other coronaviruses such as the newly emerged SARS-CoV-2.

Epidemiological investigation of avian infectious bronchitis and locally determined genotype diversity in central China: a 2016-2018 study

Infectious bronchitis (IB), caused by avian IB virus (IBV), is an acute and highly contagious disease of chickens. From 2016 to 2018, 56 IBV strains were isolated and identified from clinical samples obtained from various chicken farms located in central China. The S1 sequencing of these strains revealed nucleotide and amino acid identities of 70.2 to 100% and 62.6 to 100%, respectively, compared with those of reference strains. Phylogenetic analysis indicated that the genotypes of the isolates included GI-13 (4/91), GI-7 (TW-I), GI-24 (Mass), GI-19 (QX), and GI-18 (LDT3-A), with GI-19 (QX) being the predominant genotype. Meanwhile, GI-13 (4/91) was the second most dominant genotype in Henan Province, whereas it was GI-7 (TW-I) in Hunan and Hubei provinces. Recombination analysis of 3 variant strains showed that CK/CH/HeN/20160113 might be a recombination of LDT3-A- and QX-type strains and that CK/CH/HeN/20160316 might be a recombination of Italy-02-type strain and CK-CH-LJS08II. The predicted tertiary structure between CK/CH/HeN/20160113 and LDT3-A-type strain revealed that the novel 336 (L-P) and 455 (S-A) mutations changed the structure from an alpha helix to a random crimp. In addition, the 275 (Y-F) site reduced the length of the β-sheet, whereas the site 353 (A-T) extended the β-sheet. These findings suggested that GI-19 (QX) remains the predominant genotype in central China, and a locally determined complex genotype associated with variable clinical symptoms exists related to gene recombination and mutations.

Epidemiology and characterization of avian infectious bronchitis virus strains circulating in southern China during the period from 2013-2015

Two hundred and six strains of avian infectious bronchitis virus (IBV) were isolated from chickens showing signs of disease in southern China during the period from 2013–2015. The nucleotide and amino acid sequences from the isolated field strains were compared to 42 published references. Nucleotide homologies ranged from 63.1–99.9% and amino acid homologies ranging from 60.2–100%. At least seven IBV genotypes were co-circulating in commercial chicken farms in southern China. The IBV isolates were genetically diverse and underwent continuing evolution. The QX-type, TW I-type, and 4/91-type were the most common genotypes during the three-year observation period and accounted for 88.8% of the isolated strains. Notably, the prevalence of the TW I-type strains has been increasing in recent years and has become the most common genotype in China. The emergence of variant IBV strains can be attributed to recombination. Serologic analysis and antigenic 3D cartography of 4 reference and 14 field isolated strains indicated the surveyed IBVs had diverse serology types and that the serotype of the isolated QX-type and TW I-type strains was distinct from the vaccines strains. Therefore, long-term continuing surveillance is necessary for IBV prevention and control.

Development and characterization of neutralizing monoclonal antibodies against the S1 subunit protein of QX-like avian infectious bronchitis virus strain Sczy3

Infectious bronchitis (IB) is a highly contagious disease in chickens caused by infectious bronchitis virus (IBV). The present study was carried out with the aim to develop anti-spike 1 (S1) subunit monoclonal antibodies (MAbs) that could react with IBV strains of different genotypes. The high antigenicity region of S1 gene of an QX-like IBV strain Sczy3 was amplified and ligated into the prokaryotic expression vector pET-32a(+), and the recombinant His-S1 fusion proteins were expressed and purified. The purified whole viral antigen of Sczy3 strain was used to immunize BALB/c mice to produce hybridoma-secreting anti-IBV MAbs. Eleven anti-IBV MAbs were generated, and two MAbs 1C8 and 2C10 were positive in indirect ELISA against both His-S1 protein and the purified whole viral antigen. These two MAbs showed positive reaction with IBV in Western blot, and the isotype were both IgM. These two MAbs react specifically with IBV but not with Newcastle disease virus (NDV) or avian influenza virus (AIV) subtype H9 or H5, and could cross-react with other 10 IBV strains in five different genotypes. End-point neutralizing assay performed in chicken embro kidney (CEK) cells revealed that the neutralization titer of 1C8 and 2C10 against Sczy3 reached 1:2.82 and 1:4.70, respectively. The anti-S1 MAbs produced in the present work may be valuable in developing an antigen-capture ELISA test for antigen detection or a competitive ELISA test for antibody detection or therapeutic medicine for IB in poultry.

Molecular characterization of infectious bronchitis viruses isolated from broiler chicken farms in Iran, 2014-2015

Infectious bronchitis (IB) is a viral avian disease with economic importance in the world, including Iran. S1 gene sequencing has been used for molecular epidemiological studies and genotypic characterization of infectious bronchitis virus (IBV). A total of 118 IBV isolates were obtained from tissue samples from chickens with clinically suspected IB from Iranian broiler farms (eight provinces, 200 samples). The isolates were confirmed by real-time polymerase chain reaction (PCR) and characterized by sequencing the spike glycoprotein gene. The isolates formed six distinct phylogenetic groups (IS/1494/06 [Var2] like, 4/91-like, IS/720-like, QX-like, IR-1 and Mass-like) that were related to variants isolated in the region. The most frequently detected viruses were of the Var2-like (IS/1494/06-like) genotype, with an overall prevalence of 34 %. Twenty-one percent of the isolates formed a cluster together with the 4/91 IBV type, 10 % were of the QX genotype, and 8 % were of the IS/720 genotype. In addition, 4 % and 3 % of the isolates belonged to the Massachusetts and IR-1 genotype, respectively. For the first time, we have isolated and characterized IBV variants from broiler farms in different provinces of Iran. This study demonstrates a constant evolution of IBV in Iran, demonstrating the need for continuous monitoring and development of new vaccines based on indigenous viruses.

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.

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.

Molecular characterization of an infectious bronchitis virus strain isolated from northern China in 2012

This study reports the complete genome sequence of an infectious bronchitis virus (CK/CH/SD/121220, KJ128295) isolated in 2012 from Shandong Province in northern China. The genome is 27,666 nt long, comprising six genes and 5′ and 3′ untranslated regions. The full-length genome of the CK/CH/SD/121220 isolate had the highest nucleotide sequence identity (96.7 %) to the YX10 strain. Sites of recombination were identified in the genes 1ab, S, 5a, 5b and N, with their putative parental strains belonging to the QX- and YN-type subgroups, which are already circulating in China. Our findings suggest an important role played by recombination in IBV evolution.

Emergence of avian infectious bronchitis in a non-vaccinating country

Infectious bronchitis virus (IBV) is a coronavirus of the chicken. It is a highly contagious pathogen and in addition to causing respiratory and kidney diseases can affect the reproductive organs, resulting in loss of production and poor egg quality. Despite the global distribution of IBV, Finland has been free of clinical cases for almost three decades. Since April 2011, outbreaks involving genotypes QX, D274-like and 4/91-like have occurred in southern Finland. The clinical samples studied were submitted to the Finnish Food Safety Authority Evira from different regions of Finland during 2011 to 2013 and originated from a voluntary health monitoring programme, a national survey for avian influenza and diagnostic specimens from both commercial poultry production and hobby flocks. The sources of the infections are not known, but strains D274 and 4/91 are widely used in vaccines elsewhere.

A duplex SYBR Green I-based real-time RT-PCR assay for the simultaneous detection and differentiation of Massachusetts and non-Massachusetts serotypes of infectious bronchitis virus

Infectious bronchitis is a highly contagious viral disease of poultry caused by infectious bronchitis virus (IBV) and is considered one of the most economically important viral diseases of chickens. Control of IBV has been attempted using live attenuated and inactivated vaccines. Live attenuated vaccines of the Massachusetts (Mass.) serotype are the most commonly used for this purpose. Due to the continuous emergence of new variants of the infectious bronchitis virus, the identification of the type of IBV causing an outbreak in commercial poultry is important in the selection of the appropriate vaccine(s) capable of inducing a protective immune response. The present work was aimed at developing and evaluating a duplex SYBR Green I-based real-time RT-PCR (rRT-PCR) assay for the simultaneous detection and differentiation of Mass. and non-Mass. serotypes of IBV. The duplex rRT-PCR yielded curves of amplification with two specific melting curves (Tm1 = 83 °C ± 0.5 °C and Tm2 = 87 °C ± 0.5 °C) and only one specific melting peak (Tm = 87 °C ± 0.5 °C) when the IBV Mass. serotype and IBV non-Mass. serotype strains were evaluated, respectively. The detection limit of the assay was 8.2 gene copies/μL based on in vitro transcribed RNA and 0.1 EID50/mL. The assay was able to detect all the IBV strains assessed and discriminated well among the IBV Mass. and the IBV non-Mass. serotypes strains. In addition, amplification curves were not obtained with any of the other viruses tested. From the 300 field samples tested, the duplex rRT-PCR yielded a total of 80 samples that were positive for IBV (26.67%), 73 samples identified as the IBV Mass. serotype and seven samples as identified as the IBV non-Mass. serotype. A comparison of the performance of test as assessed with field samples revealed that the duplex rRT-PCR detected a higher number of IBV-positive samples than when conventional RT-PCR or virus isolation tests were used. The duplex rRT-PCR presented here is a useful tool for the rapid identification of outbreaks and for surveillance programmes during IB-suspected cases, particularly in countries with a vaccination control programme.