Serotype, antigenicity, and pathogenicity of a naturally recombinant TW I genotype infectious bronchitis coronavirus in China

Development and Immunoprotection of Bacterium-like Particle Vaccine against Infectious Bronchitis in Chickens

Infectious bronchitis (IB) is a major threat to the global poultry industry. Despite the availability of commercial vaccines, the IB epidemic has not been effectively controlled. The exploration of novel IBV vaccines may provide a new way to prevent and control IB. In this study, BLP-S1, a bacterium-like particle displaying the S1 subunit of infectious bronchitis virus (IBV), was constructed using the GEM-PA surface display system. The immunoprotective efficacy results showed that BLP-S1 can effectively induce specific IgG and sIgA immune responses, providing a protection rate of 90% against IBV infection in 14-day-old commercial chickens. These results suggest that BLP-S1 has potential for the development of novel vaccines with good immunogenicity and immunoprotection.

Effect of monovalent and bivalent live attenuated vaccines against QX-like IBV infection in young chickens

Since 1999, QX-like (GI-19) avian infectious bronchitis viruses have been the predominant strains in China till now. Vaccination is the most effective way to control the disease, while live attenuated vaccine is widely used. In the current research, we evaluated the effect of several monovalent and bivalent live IBV vaccines in young chickens against the QX-like (GI-19) IBV infection. The results showed that monovalent 4/91 and bivalent Ma5+LDT3 vaccines could provide efficient protection in day-old chickens that reduced morbidity and mortality, ameliorated histopathology lesions, and reduced viral loads were observed. These data suggest that vaccination through nasal route with monovalent 4/91 or bivalent Ma5+LDT3 in day-old chickens could serve a safe and effective vaccination strategy for controlling QX-like (GI-19) infectious bronchitis virus.

Infectious Bronchitis Virus: A Comprehensive Multilocus Genomic Analysis to Compare DMV/1639 and QX Strains

Infectious bronchitis virus (IBV) is a highly variable RNA virus that affects chickens worldwide. Due to its inherited tendency to suffer point mutations and recombination events during viral replication, emergent IBV strains have been linked to nephropathogenic and reproductive disease that are more severe than typical respiratory disease, leading, in some cases, to mortality, severe production losses, and/or unsuccessful vaccination. QX and DMV/1639 strains are examples of the above-mentioned IBV evolutionary pathway and clinical outcome. In this study, our purpose was to systematically compare whole genomes of QX and DMV strains looking at each IBV gene individually. Phylogenetic analyses and amino acid site searches were performed in datasets obtained from GenBank accounting for all IBV genes and using our own relevant sequences as a basis. The QX dataset studied is more genetically diverse than the DMV dataset, partially due to the greater epidemiological diversity within the five QX strains used as a basis compared to the four DMV strains from our study. Historically, QX strains have emerged and spread earlier than DMV strains in Europe and Asia. Consequently, there are more QX sequences deposited in GenBank than DMV strains, assisting in the identification of a larger pool of QX strains. It is likely that a similar evolutionary pattern will be observed among DMV strains as they develop and spread in North America.

Antiviral activity and underlying mechanisms of Baicalin against avian infectious bronchitis virus in vitro

Baicalin, a flavonoid compound extracted from the dry root of Scutellaria baicalensis Georgi, has been shown to have anti-inflammation, anti-viral, anti-bacterial, and immunomodulatory activity. However, the effect of baicalin against avian infectious bronchitis virus (IBV) remains unknown. The purpose of this study was to investigate the anti-IBV activity and underlying mechanism of baicalin in vitro. The results showed that baicalin has a direct virucidal effect but no prophylactic effect on IBV infection. The mRNA and protein of IBV N were decreased obviously when IBV-infected cells were treated with baicalin during the multiple stages of the virus replication cycle, including viral adsorption, invasion, internalization, and release. Stress granule (SG) formation resulted from the increase of G3BP1 and the phosphorylation of the PKR/eIF2α due to the treatment of IBV-infected cells with baicalin. The inhibitory activity of baicalin on IBV replication was increased when G3BP1 expression was inhibited, and the down-regulation of G3BP1 expression occurred when the expression of PKR and eIF2α was inhibited. These findings revealed that baicalin activates phosphorylation of PKR/eIF2α pathway and induces SG formation by targeting G3BP1, initiating the antiviral response to suppress IBV replication on Vero cell. The results suggest that baicalin is a promising candidate drug to treat or prevent IBV infection.

Characterization of an Infectious Bronchitis Virus Isolated from Commercial Layers Suffering from False Layer Syndrome

Infectious bronchitis virus (IBV) is a gammacoronavirus that primarily induces an upper respiratory disease in chickens, also affecting the urogenital tract and occasionally leading to a condition called false layer syndrome (FLS), where sexually mature hens ovulate normally but are unable to lay eggs. Here, we describe an outbreak of FLS in Arizona from which an IBV variant that is nearly 90% homologous to DMV/1639 using the Spike subunit 1 gene, named AZ/FLS/17, was isolated and used in challenge experiments. Three-day-old specific-pathogen-free chicks were challenged with AZ/FLS/17 or M41 in high and low doses, and the disease outcomes were compared. Overall, no differences in microscopic lesions or viral loads in the reproductive tract were detected between AZ/FLS/17- and M41-infected birds. To minimize the losses linked to FLS in the problematic flocks, an updated live-attenuated IBV vaccine protocol including the use of the Ma5 strain at the hatchery was implemented, resulting in a drastic reduction of false layers in the subsequent flocks. To monitor the circulation of wild-type and vaccine strains in this population, a molecular surveillance study was performed. Samples were collected at 1, 7, 14, and 21 days of age, and from laying hens at 30 and 36 wk. In older birds, the IBV strains detected were more diverse than at 1 and 7 days of age. Nevertheless, live vaccine combinations are still widely used to decrease the losses caused by FLS in commercial egg laying flocks worldwide.

The Efficacy of a Live Attenuated TW I-Type Infectious Bronchitis Virus Vaccine Candidate

Infectious bronchitis (IB) is a highly contagious avian disease caused by infection with infectious bronchitis virus (IBV), which seriously affects the development of the global poultry industry. The distribution of TW I-type IBV in China has increased in recent years, becoming a widespread genotype. We previously isolated a TW I-type IBV strain termed CK/CH/GD/GZ14 in 2014, but its pathogenicity and possibility for vaccine development were not explored. Therefore, this research aimed to develop a live-attenuated virus vaccine based on the CK/CH/GD/GZ14 strain. The wild type IBV CK/CH/GD/GZ14 strain was serially passaged in SPF embryos for 145 generations. The morbidity and mortality rate of wild-type strain in 14 day-old chickens is 100% and 80% respectively, while the morbidity rate in the attenuated strain was 20% in the 95th and 105th generations and there was no death. Histopathological observations showed that the pathogenicity of the 95th and 105th generations in chickens was significantly weakened. Further challenge experiments confirmed that the attenuated CK/CH/GD/GZ14 strain in the 95th and 105th generations could resist CK/CH/GD/GZ14 (5th generation) infection and the protection rate was 80%. Tracheal cilia stagnation, virus shedding, and viral load experiments confirmed that the 95th and 105th generations provide good immune protection in chickens, and the immunogenicity of the 105th generation is better than that of the 95th generation. These data suggest that the attenuated CK/CH/GD/GZ14 strain in the 105th generation may be applied as a vaccine candidate against TW I-type IBV.

Phylogenetic analysis of infectious bronchitis virus circulating in southern China in 2016-2017 and evaluation of an attenuated strain as a vaccine candidate

Avian infectious bronchitis (IB) is a highly contagious viral respiratory disease, caused by infectious bronchitis virus (IBV), that poses an important economic threat to the poultry industry. In recent years, genotypes GI-7, GI-13, and GI-19 have been the most prevalent IBV strains in China. However, in this study, we found that most IBV strains from southern China in 2016-2017 belonged to genotype GVI-1. This genotype, for which there is no vaccine, has been reported sporadically in the region. The GDTS13 strain, which caused severe IB outbreaks on the farms where it was isolated, was evaluated as a candidate vaccine strain. GDTS13 was serially passaged in specific-pathogen-free embryonated chicken eggs for 100 generations to produce GDTS13-F100. Safety testing indicated that GDTS13-F100 had no pathogenic effect on chickens. Additionally, GDTS13-F100 showed an excellent protective effect against GDTS13, with no clinical signs or virus shedding observed in immunized chickens challenged with the parent strain. These findings indicate that GVI-1 has become the most prevalent IBV genotype in southern China and that GDTS13-F100 may serve as an attenuated vaccine to protect against infection with this genotype.

Genetic, Antigenic, and Pathogenic Characteristics of Infectious Bronchitis Virus GI-7/TW-II in China

Nine infectious bronchitis virus (IBV) strains belonging to the GI-7 lineage were isolated between 2009 and 2017 in China. Phylogenetic analysis and comparisons of full-length sequences of the S1 gene suggested that the GI-7 lineage should be further classified as Taiwan (TW)-I and TW-II sublineages, which correspond to the previous TW-I and TW-II genotypes. The nine IBV strains were clustered in the TW-II sublineage. Further investigation revealed that viruses in the TW-I and TW-II were not only genetically but also antigenically different. Moreover, the TW-II sublineage contained various clades and recombinants. A recombinant was found to originate from recombination events between field strains (TW-II ck/CH/LJL/090608- and GI-19 ck/ CH/LDL/091022-like viruses) in which the recombination in the S1 subunit coding sequences had led to changes in antigenicity of the viruses. A more in-depth investigation demonstrated that TW-II viruses appear to have undergone a significant evolution following introduction in mainland China, which resulted in the viruses diverging into different clades. The viruses between the different clades in TW-II sublineage exhibited a significant change in genetic and antigenic characteristics. In addition, the five TW-II viruses selected on the basis of the results of S1 nucleotide sequence phylogenetic trees showed different pathogenicity to specific-pathogen-free chickens, although they could induce nephritis in the infected chickens and thus were identified as nephropathogenic strains.

Evaluation of the reproductive system development and egg-laying performance of hens infected with TW I-type infectious bronchitis virus

The prevalence of TW I-type infectious bronchitis virus (IBV) has been increasing rapidly, and it has become the second most common genotype of IBV in China threatening the poultry industry. In this study, 1-day-old specific-pathogen-free (SPF) chickens infected with TW I-type IBV were continuously observed for 200 days. TW I-type IBV affected the respiratory, urinary, and female reproductive systems, resulting in a mortality rate of 10% as well as a decrease in egg quantity and an increase in inferior eggs. During the monitoring period, serious lesions occurred in the female reproductive system, such as yolk peritonitis, a shortened oviduct, and cysts of different sizes with effusion in the degenerated right oviduct. The infective viruses persisted in vivo for a long time, and due to the stress of laying, virus shedding was detected again after the onset of egg production. Our findings suggest that TW I-type IBV is deadly to chickens and could cause permanent damage to the oviduct, resulting in the poor laying performance of female survivors and decreasing the breeding value and welfare of the infected flock.

Efficacy of commercial polyvalent avian infectious bronchitis vaccines against Chinese QX-like and TW-like strain via different vaccination strategies

The infectious bronchitis virus (IBV) is an acute and highly contagious disease, which affects chickens of all ages. Vaccination is the most important way to control this disease. Nevertheless, novel variant strains are constantly reported because of the lack of proofreading capabilities of RNA polymerase and high frequency of homologous RNA recombination. Cross-protection studies has demonstrated that the vaccines could provide great protective effects against viruses of same serotype or genotype. However, the protective effect of different commercial vaccines and vaccine combinations against the prevalent IBV strains in China has rarely been studied. Owing to the multiple genotype or serotype IBV strains prevalence in China, the polyvalent vaccines and their composition were used to expanding the protection spectrum of vaccine in practical application. To evaluate the protection of Chinese commercial IBV polyvalent vaccines against prevalent strains (QX-like and TW I-like), an immune challenge test was conducted. Four polyvalent vaccines, containing 4/91, H120, YX10p90, LDT3-A, and 28/86, were combined to form 8 vaccination strategies, almost all of which could provide more than 70% protection effects against challenge with QX-like strain. Particularly, the best protection rate (93%) was generated by administration the polyvalent vaccine C (H120 + 28/86 + 4/91) at 1 D of age and the polyvalent vaccine B (H120 + 4/91 + YX10p90) at 10 D of age. However, all the vaccination strategies in this study cannot provide great protective effects against TW-like strain, and more vaccines should be included in studies to expand the protection spectrum of vaccine. Therefore, for the newly emerging IBV strains, immunization with polyvalent vaccines via different vaccination strategies could be used to control the prevalence of IBV in a short time, whereas developing the homologous vaccines was not always necessary.

Multiple recombination events between field and vaccine strains resulted in the emergence of a novel infectious bronchitis virus with decreased pathogenicity and altered replication capacity

In this study, we isolated and identified 2 infectious bronchitis virus (IBV) strains from layer chickens soon after vaccination with the Massachusetts-Connecticut bivalent vaccine (Conn) and H120 and 4/91 booster vaccines in China in 2011. The results of cross-virus-neutralization tests and phylogenetic analysis of the S1 subunit of spike gene of these vaccine strains and other reference strains showed that strain LJL/110302 was of GI-19 lineage, whereas LLN/111169 was of the GI-1 lineage of the Conn serotype. Further comparative genomic analysis revealed that LLN/111169, an IBV strain with novel traits, originated from multiple recombination events (at least 3 recombination sites) between GI-19 and the Conn and 4/91 vaccine strains. LLN/111169 was pathogenic to specific pathogen-free (SPF) chickens. This is of prime importance because while IBV prevention measures worldwide are mainly dependent on modified live vaccine strains, our results showed that recombination between field and vaccine strains has produced a novel pathogenic IBV strain. In addition, LLN/111169 showed relatively broad tissue tropism (trachea, lungs, kidneys, and cecal tonsils) in infected SPF chickens. These results emphasize the importance of IBV surveillance in chicken flocks.

Emerging lethal infectious bronchitis coronavirus variants with multiorgan tropism

Infectious bronchitis virus (IBV) causes respiratory diseases in chickens and poses an economic threat to the poultry industry worldwide. Despite vaccine use, there have been field outbreaks of IBV in Taiwan. This study aimed to characterize the emerging IBV variants circulating in Taiwan. The analysis of the structural protein genes showed that these variants emerged through frequent recombination events among Taiwan strains, China strains, Japan strains and vaccine strains. Cross‐neutralization tests revealed that two of the variants exhibited novel serotypes. Clinicopathological assessment showed that two of the variants caused high fatality rates of 67% and 20% in one‐day‐old SPF chicks, and all the variants possessed multiorgan tropisms, including trachea, proventriculus and urogenital tissues. Furthermore, the commercial live‐attenuated Mass‐type vaccine conferred poor protection against these variants. This study identified novel genotypes, serotypes and pathotypes of emerging IBV variants circulating in Taiwan. There is an urgent need for effective countermeasures against these variant strains.

Molecular and biological characteristics of the infectious bronchitis virus TC07-2/GVI-1 lineage isolated in China

In the present study, a thorough comparison of the infectious bronchitis virus (IBV) TC07–2/GVI-1 linage was conducted by comparing the S1 gene sequences of GVI-1 viruses with those of viruses representing the established genotypes and lineages. IBV GVI-1 strains were found to be closely genetically related to each other, irrespective of where the viruses were isolated, and differed from other known IBV genotypes and lineages; thus, it was confirmed that GVI represents a novel genotype. However, the GVI-1 viruses exhibited variable antigenicity when compared to each other. Further analysis found that strains CO8089L and CO8091L, which were isolated in Colombia in 2003, were closely related to GVI-1 viruses, suggesting that GVI-1 viruses likely originated from Colombia and are prevalent in at least five countries (Colombia, China, the Republic of Korea, Japan, and Vietnam). Analysis of the complete GVI-1 virus genomes suggested that the GVI-1 strains in China may be independently derived from recombination events that occurred between GI-19 strains and CO8089L/CO8091L-like viruses following the introduction of the viruses from Colombia. Similar to the viruses isolated in the Republic of Korea, GVI-1 viruses isolated in China also showed an affinity for the respiratory tract of chickens, which differed from one of the deduced parental viruses, the GI-19 strain. This difference may be due to recombination events that occurred in the genomes of the GVI-1 viruses, resulting in the replacement of the spike gene sequences in an YX10-like strain of GI-19 lineage.

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GVI-1 viruses likely originated from Columbia.

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GVI-1 strains isolated in China may be derived from recombination events between GI-19 and CO8089L/CO8091L-like viruses.

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GVI-1 viruses exhibited variable antigenicity.

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GVI viruses showed an affinity for the respiratory tract of chickens.

Novel genotype of infectious bronchitis virus isolated in China

Recombination events are known to contribute to the emergence of novel infectious bronchitis virus (IBV) genotypes. In this study, we carried out detailed phylogenetic analysis and sequence comparisons based on 74 complete nucleotide sequences of the IBV S1 gene, including strain I0636/16 and 73 representative sequences from each genotype and lineage. The results showed that strain I0636/16 represented a novel genotype, designated as lineage 1 within genotype VII (GVII-1). Further comparative genomic analysis revealed at least two recombination sites that replaced the spike gene in a lineage 18 within genotype I (GI-18)-like virus with an as-yet-unidentified sequence, likely derived from another IBV strain, resulting a novel serotype with a lower affinity to the respiratory tract in chickens. To the best of our knowledge, this provides the first evidence for recombination leading to replacement of the complete spike gene and the emergence of a novel genotype/serotype with a lower affinity to the respiratory tract in chickens comparing to one of its parental virus ck/CH/LGX/111119. These results emphasize the importance of limiting exposure to novel IBVs that may serve as a source of genetic material for emerging viruses, as well as the importance of IBV surveillance in chicken flocks.

Genetic and biological characteristics of four novel recombinant avian infectious bronchitis viruses isolated in China

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Two IBV strains were proved to be originated from multiple recombination events.

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Viruses with very similar S1 gene sequences showed varying biological features.

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Point mutations were observed in the RBD and HVRs of the recombinant viruses.

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Point mutations likely have an effect on these differences in biological characteristics.

Infectious bronchitis viruses (IBVs) of GI-13 (793/B) and GI-19 (QX/LX4) lineages have been frequently detected in China in recent years. Naturally recombinant IBVs originating from the GI-13 and GI-19 lineages have also been isolated from chicken flocks with respiratory and renal problems in China. Thorough genetic and biological investigations of these recombinant viruses have led to speculation regarding their origin, evolution, and control. In order to confirm the previous results and further extend our understanding about the characteristics of the four recombinant IBV strains we had previously identified (I0718/17, I0722/17, I0724/17, and I0737/17), we conducted phylogenetic analysis by comparing their complete S1 gene sequences with those of 71 reference strains of different genotypes and lineages. We identified a close relationship between the S1 sequences of the four strains and those of GI-13 strains. The results of complete genome sequence analysis confirmed the previously identified recombination events in the four IBV strains and revealed additional recombination events in different genomic regions of strains I0718/17 and I0724/17, suggesting that the two strains originated from multiple recombination events between 4/91-like and YX10-like viruses. We comparatively evaluated the antigenicity, pathogenicity, and affinity of the four recombinant viruses and their deduced parental strains in the trachea and kidneys. Some of the strains showed comparable antigenic relatedness, pathogenicity, and affinity for the trachea and kidneys among each other and with their parental viruses; however, some of them showed varying biological characteristics. Point mutations observed in the receptor-binding domain and hypervariable region of the S1 subunit of the spike protein likely have an effect on these differences in biological characteristics, although the influence of other factors—such as host innate-immune responses and changes in genomic regions beyond the S1 protein—might also be responsible for such changes.

Genetic diversity of avian infectious bronchitis virus in China in recent years

In this study, 213 infectious bronchitis viruses (IBVs) were isolated from samples collected from 801 flocks suspected to be infected with IBV from January 2016 to December 2017 in China. By using complete nucleotide sequences of S1 gene we determined the phylogeny of these IBV isolates, which in turn allowed us to define six lineages/genotypes, a number of recombinants and a novel variant. The GI-19 lineage was the most frequently isolated type in China in recent years. Although scattered mutations in the S1 gene among the GI-19 lineage viruses were observed, we also noted different sublineages in the GI-19 lineage with unique mutations, suggesting a high degree of S1 gene variation since they were first isolated in the mid-1990s. We also isolated a number of vaccine-like viruses from vaccinated diseased chickens, although more work is needed to differentiate the reisolation of vaccine strains from field strains of the same serotype. One of the important findings in this study is that the prevalence of the TW I type viruses in GI-7 lineage has been increasing in recent years in China. Another important finding is that recombination events occurred between the predominant GI-19 lineage and the commonly used 4/91 vaccine, which gave rise to distinct IBV isolates. In addition, a novel IBV isolate, together with a reference strain in GenBank database, were found to form a novel lineage/genotype that was remarkably distinct from established lineages. The characteristics of the antigenicity, tissue tropism, pathogenicity and complete genome were required for further investigation for the recombinants and the viruses in different sublineages and novel lineages. Meanwhile, permanent monitoring of circulating strains was needed to monitor the emerging viruses and rationally modify vaccination strategies in the field situation.

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The GI-19 lineage was the most frequently isolated type in China in recent years.

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Different sub-lineages were found in the GI-19 lineage with unique mutations.

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A number of vaccine-like viruses were isolated from vaccinated diseased chickens.

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The TW I type viruses in GI-13 lineage has been increasing in recent years in China.

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A novel IBV isolate was found to form a novel clade that was distinct from established lineages.

Genetics, antigenicity and virulence properties of three infectious bronchitis viruses isolated from a single tracheal sample in a chicken with respiratory problems

Three different IBV genotypes/serotypes, designated ck/CH/LDL/150434–I (LDL/150434–I), ck/CH/LDL/150434–II (LDL/150434–II) and ck/CH/LDL/150434–III (LDL/150434–III), were detected in a single tracheal sample from a chicken showing signs of respiratory disease. The viruses were isolated using a cross-neutralization test and limiting dilution in embryonated specific-pathogen-free (SPF) eggs. Isolate LDL/150434–I was a re-isolation of H120 vaccine strain that was introduced into the chicken flock by vaccination, transmitted between chickens, and later accumulated several genomic mutations. Isolate LDL/150434–II was a novel variant that originated from recombination events between H120 and ck/CH/LDT3/03-like viruses. The widespread use of H120 vaccine, which offered incomplete protection against heterotypic IBVs in the fields, may play important roles in the emergence of such a novel genetic variant. Based on the analysis of S1 and complete genomic sequence, isolate LDL/150434–III was related genetically but distinct from the established strains of nrTW I type viruses of GI-7 lineage circulating in Mainland China since 2009. The three IBV isolates were avirulent when they infected SPF chickens. Furthermore, synergistic effects on pathogenicity were not observed when the different types co-infected the SPF chickens. However, the isolates persisted in the respiratory tracts longer in combined infected birds than those in individual infected birds. The results provide insights into the evolution of the viruses and co-infection of chickens with different virus serotypes.

Characterization of the complete genome, antigenicity, pathogenicity, tissue tropism, and shedding of a recombinant avian infectious bronchitis virus with a ck/CH/LJL/140901-like backbone and an S2 fragment from a 4/91-like virus

In this study, we isolated an infectious bronchitis virus, designated I1101/16, from broiler breeders in China. Analysis of the S1 gene showed that isolate I1101/16 was genetically close to strain ck/CH/LJL/140901, which belongs to the TW I genotype (also known as lineage GI-7 based on the recent IBV classification), however the S2 gene showed genetic diversity comparing to that of S1 gene. Comparison of the genomic sequences showed that the genome of isolate I1101/16 was similar to that of strain ck/CH/LJL/140901 from the 5' end of the genome to the 5' end of the S2 gene and from the 5' end of the 3a gene to the end of the genome, whereas the remaining parts of the genome sequences were more closely related to those of strain 4/91 than those of ck/CH/LJL/140901, thereby suggesting that recombination might have occurred during the origin of the virus. SimPlot and Bootscan analysis of the complete genomic sequence confirmed this hypothesis, where it showed that isolate I1101/16 arose through recombination events between ck/CH/LJL/140901- and 4/91-like viruses. Isolate I1101/16 and strain ck/CH/LJL/140901 shared identical amino acids in almost all five of their B cell epitopes, but the two viruses had a serotype relatedness value of 65, which is well below 80, i.e., the lower cutoff value for viruses of the same serotype. In addition, pathogenicity tests demonstrated that isolate I1101/16 was more pathogenic to 1-day-old specific-pathogen-free chickens than strain ck/CH/LJL/140901, according to analysis of the clinical signs, whereas strain ck/CH/LJL/140901 exhibited prolonged replication and shedding after challenge compared with isolate I1101/16. This study did not provide evidence that recombination can directly alter the antigenicity, virulence, replication, shedding, and tissue tropism of a virus, but it did show that recombination events are likely to be major determinants of viral evolution.

Complete Genome Sequence of a Novel Strain of Infectious Bronchitis Virus, Isolated from Chickens in China in 2016

An avian infectious bronchitis virus (IBV) was detected from trachea swabs of chickens in Hubei province, China, in 2016. The complete genome of the IBV strain, CK/CH/HB/2016, was characterized and analyzed to better understand IBV epidemiology in China.

Infectious Bronchitis Virus Variants: Molecular Analysis and Pathogenicity Investigation

Infectious bronchitis virus (IBV) variants constantly emerge and pose economic threats to poultry farms worldwide. Numerous studies on the molecular and pathogenic characterization of IBV variants have been performed between 2007 and 2017, which we have reviewed herein. We noted that viral genetic mutations and recombination events commonly gave rise to distinct IBV genotypes, serotypes and pathotypes. In addition to characterizing the S1 genes, full viral genomic sequencing, comprehensive antigenicity, and pathogenicity studies on emerging variants have advanced our understanding of IBV infections, which is valuable for developing countermeasures against IBV field outbreaks. This review of IBV variants provides practical value for understanding their phylogenetic relationships and epidemiology from both regional and worldwide viewpoints.

Genome characterization, antigenicity and pathogenicity of a novel infectious bronchitis virus type isolated from south China

In 2014, three infectious bronchitis virus (IBV) strains, designated as γCoV/ck/China/I0111/14, γCoV/ck/China/I0114/14 and γCoV/ck/China/I0118/14, were isolated and identified from chickens suspected to be infected with IBV in Guangxi province, China. Based upon data arising from S1 sequence and phylogenetic analyses, the three IBV isolates were genetically different from other known IBV types, which represented a novel genotype (GI-29). Virus cross-neutralization tests, using γCoV/ck/China/I0111/14 as a representative, showed that genotype GI-29 was antigenically different from all other known IBV types, thus representing a novel serotype. Complete genomic analysis showed that GI-29 type viruses were closely related to and might originate from a GX-YL5-like virus by accumulation of substitutions in multiple genes. These GI-29 viral genomes are still evolving and diverging, particularly in the 3′ region, although we cannot rule out the possibility of recombination events occurring. For isolate γCoV/ck/China/I0114/14, we found that recombination events had occurred between nsps 2 and 3 in gene 1 which led to the introduction of a 4/91 gene fragment into the γCoV/ck/China/I0114/14 viral genome. In addition, we found that the GI-29 type γCoV/ck/China/I0111/14 isolate was a nephropathogenic strain and high pathogenic to 1-day-old specific pathogen-free (SPF) chickens although cystic oviducts were not observed in the surviving layer chickens challenged with γCoV/ck/China/I0111/14 isolate.

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A novel infectious bronchitis virus type, GI-29, has been identified in China.

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Identification of mutations scattered throughout the GI-29 genome.

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The GI-29 type is nephropathogenic to specific pathogen-free chickens.

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.

Identification and molecular characterization of a novel serotype infectious bronchitis virus (GI-28) in China

Avian infectious bronchitis coronavirus (IBV) is a major poultry pathogen. A characteristic feature of IBV is the occurrence of many different strains belonging to different serotypes, which renders complete control of the disease by vaccination a challenging task due to the poor cross-protection between different serotypes. In this study, based on the results of S1 sequence analysis and virus cross-neutralization tests, IBV strain ck/CH/LGX/111119 was found to be genetically and antigenically different from other known IBV types, representing not only a novel genotype, but also a novel serotype (designated as GI-28). Viruses belonging to this novel serotype have been isolated from several regions in China in recent years, suggesting endemic circulation of the serotype in various geographic locations in China. Further studies by complete genomic analysis showed that strain ck/CH/LGX/111119 may have originated from recombination events involving LX4 genotype IBVs and an as-yet-unidentified IBV donating a S1 gene, or from the result of accumulation of mutations and selections, especially in the S1 gene, from a LX4 genotype virus. ck/CH/LGX/111119 is a nephropathogenic strain, although it had broader tissue tropism (respiratory, digestive, urinary, and reproductive tracts) among chickens challenged at one day old. Infection of the oviducts with ck/CH/LGX/111119 found in this study may have severe implications because the virus will likely induce the occurrence of false layers.