Pathological effect of different avian infectious bronchitis virus strains on the bursa of Fabricius of chickens.

Infectious bronchitis is an acute and highly contagious disease caused by avian infectious bronchitis virus (IBV). As well as the typical clinical respiratory signs, such as dyspnoea and tracheal rales, QX genotype strains can also cause damage to the urinary system and reproductive system. Our previous studies found that chickens infected with QX-type IBV also displayed damage to the bursa of Fabricius. To investigate the effects of different genotypes of IBV on the bursa of Fabricius, we challenged one-week-old SPF chickens with Mass, QX and TW genotype IBV strains and compared the clinical signs, gross lesions, histopathological damage, viral loads, and expression levels of inflammatory cytokines (IL-6, IL-8, IL-1ß, IFN-α,ß, γ and TNF-α). The results showed that all three strains caused tissue damage, while significant temporal variations in the viral loads of the different infected groups were detected. IBV infection seriously interfered with the natural immune response mediated by inflammatory cytokines (IFN-α, IFN-ß, IL-6 and IFN-γ) in chickens. Our results suggested that IBV has potential immunological implications for chickens that may lead to poor production efficiency. RESEARCH HIGHLIGHTSAvian coronavirus IBV is an important pathogen of chickens.IBV has potential immunological implications in chickens.The bursal viral load of different IBV strains varies significantly.

Genomic Analysis of Avian Infectious Bronchitis Viruses Recently Isolated in South Korea Reveals Multiple Introductions of GI-19 Lineage (QX Genotype).

Infectious bronchitis virus (IBV) was first identified in the 1930s and it imposes a major economic burden on the poultry industry. In particular, GI-19 lineage has spread globally and has evolved constantly since it was first detected in China. In this study, we analyzed S1 gene sequences from 60 IBVs isolated in South Korea. Two IBV lineages, GI-15 and GI-19, were identified in South Korea. Phylogenetic analysis suggested that there were six distinct subgroups (KM91-like, K40/09-like, and QX-like I to IV) of the South Korean GI-19 IBVs. Among them, QX-type III and IV subgroups, which are phylogenetically different from those reported in South Korea in the past, accounted for more than half of the total. Moreover, the phylogeographic analysis of the QX-like subgroups indicated at least four distinct introductions of GI-19 IBVs into South Korea during 2001-2020. The efficacy of commercialized vaccines against the recently introduced QX-like subgroups should be verified, and continuous international surveillance efforts and quarantine procedures should be enhanced to prevent the incursion of viruses.

Infectious bronchitis virus in Australia: a model of coronavirus evolution - a review.

Infectious bronchitis virus (IBV) was first isolated in Australia in 1962. Ongoing surveillance and characterization of Australian IBVs have shown that they have evolved separately from strains found throughout the rest of the world, resulting in the evolution of a range of unique strains and changes in the dominant wild-type strains, affecting tissue tropism, pathogenicity, antigenicity, and gene arrangement. Between 1961 and 1976 highly nephropathogenic genotype GI-5 and GI-6 strains, causing mortalities of 40% to 100%, predominated, while strains causing mainly respiratory disease, with lower mortality rates, have predominated since then. Since 1988, viruses belonging to two distinct and novel genotypes, GIII and GV, have been detected. The genome organization of the GIII strains has not been seen in any other gammacoronavirus. Mutations that emerged soon after the introduction of vaccination, incursion of strains with a novel lineage from unknown sources, recombination between IBVs from different genetic lineages, and gene translocations and deletions have contributed to an increasingly complex IBV population. These processes and the consequences of this variation for the biology of these viruses provide an insight into the evolution of endemic coronaviruses during their control by vaccination and may provide a better understanding of the potential for evolution of other coronaviruses, including SARS-CoV-2. Furthermore, the continuing capacity of attenuated IBV vaccines developed over 40 years ago to provide protection against viruses in the same genetic lineage provides some assurance that coronavirus vaccines developed to control other coronaviruses may continue to be effective for an extended period.

Transcriptome analysis of primary chicken cells infected with infectious bronchitis virus strain K047-12 isolated in Korea.

Infectious bronchitis virus (IBV), an avian coronavirus, is highly contagious. Chickens with IBV infection develop acute pathogenesis in multiple organs, including the respiratory and urogenital tracts. Frequent recombination in the spike (S) glycoprotein gene has made vaccine strategies ineffective. To understand IBV pathogenesis, we analyzed the genetic distance between Korean IBV isolates and other coronaviruses, including SARS-CoV-2. To obtain comprehensive information about early immune responses such as innate cytokine production and associated immune regulation during IBV infection, we infected primary chicken embryonic kidney cells and performed transcriptome analysis. We observed that the functional pathways of innate immunity are regulated and confirmed expression of genes that coordinate early immune responses. Understanding the immune profile of the host cell may assist in vaccine development.

Coronavirus: proteomics analysis of chicken kidney tissue infected with variant 2 (IS-1494)-like avian infectious bronchitis virus.

Avian infectious bronchitis virus is one of the most important gammacoronaviruses, which causes a highly contagious disease. In this study, we investigated changes in the proteome of kidney tissue of specific-pathogen-free (SPF) chickens that were infected with an isolate of the nephrotropic variant 2 genotype (IS/1494/06) of avian coronavirus. Twenty 1-day-old SPF White Leghorn chickens were randomly divided into two groups, each comprising 10 chickens, which were kept in separate positive-pressure isolators. Chickens in group A served as a virus-free control group up to the end of the experiment, whereas chickens in group B were inoculated with 0.1 ml of 104.5 EID50 of the IBV/chicken/Iran/UTIVO-C/2014 isolate of IBV, and kidney tissue samples were collected at 2 and 7 days post-inoculation (dpi) from both groups. Sequencing of five protein spots at 2 dpi and 22 spots at 7 dpi that showed differential expression by two-dimensional electrophoresis (2DE) along with fold change greater than 2 was done by MS-MALDI/TOF/TOF. Furthermore, the corresponding protein-protein interaction (PPI) networks at 2 and 7 dpi were identified to develop a detailed understanding of the mechanism of molecular pathogenesis. Topological graph analysis of this undirected PPI network revealed the effect of 10 genes in the 2 dpi PPI network and nine genes in the 7 dpi PPI network during virus pathogenesis. Proteins that were found by 2DE analysis and MS/TOF-TOF mass spectrometry to be down- or upregulated were subjected to PPI network analysis to identify interactions with other cellular components. The results show that cellular metabolism was altered due to viral infection. Additionally, multifunctional heat shock proteins with a significant role in host cell survival may be employed circuitously by the virus to reach its target. The data from this study suggest that the process of pathogenesis that occurs during avian coronavirus infection involves the regulation of vital cellular processes and the gradual disruption of critical cellular functions.

Molecular epidemiology of infectious bronchitis virus in Poland from 1980 to 2017.

The presence of infectious bronchitis virus (IBV) was identified for the first time in the poultry population in Poland at the end of the 1960s. From this time a few waves of epidemics caused by different IBV variants spread across the country. In order to gain more insight into the molecular epidemiology of IBV in Poland, in the present study the S1 coding region of 34 IBV isolates and nearly whole genome of 10 strains collected over a period of 38 years was characterized. Phylogenetic analysis showed that these strains belonged to five recently established IBV lineages: GI-1, GI-12, GI-13, GI-19 and GI-23. Additionally, two strains from 1989 and 1997 formed a separate branch of the phylogenetic tree categorized as unique early Polish variants, and one strain was revealed to be the recombinant of these and GI-1 lineage viruses. Irrespective of year of isolation and S1-dependent genotype, the genome sequences of Polish IBV strains showed the presence of six genes and 13 ORFs: 5'UTR-1a-1b-S-3a-3b-E-M-4b-4c-5a-5b-N-6b-3'UTR, however their individual genes and putative proteins had different lengths. The phylogenetic analyses performed on the genome of ten Polish IBV strains revealed that they cluster into different groups. The Polish GI-1, GI-19 and GI-23 strains cluster with other similar viruses of these lineages, with the exception of the two strains from 1989 and 1997 which are different. It seems that in Poland in the 1980s and 1990s IBV strains with a unique genome backbone circulated in the field, which were then replaced by other strains belonging to other IBV lineages with a genome backbone specific to these lineages. The recombination analysis showed that some Polish strains resulted from a recombination event involving different IBV lineages, most frequently GI-13 and GI-19.

A novel low virulent respiratory infectious bronchitis virus originating from the recombination of QX, TW and 4/91 genotype strains in China.

In China, variants of infectious bronchitis virus (IBV) evolve continually and diverse recombinant strains have been reported. Here, an IBV strain, designated as ck/CH/LJX/2017/07 (referred as JX17) was isolated from chicken vaccinated with H120 and 4/91 in Jiangxi, China, in 2017. Sequence analysis reveals of the S1 gene of JX17 the highest nucleotide identity of 98.15% with that of GI-7 genotype TW2575/98 strain. Furthermore, whole genome analysis among JX17 and other 18 IBV strains demonstrates that JX17 has the highest nucleotide identity of 95.94% with GI-19 genotype YX10 strain. Among all genes of JX17 except the S1 gene, the N gene and 3' UTR have the highest identity to GI-13 genotype 4/91 strain and the rest genes are the most identical to GI-19 genotype YX10 strain. Analyzed by the RDP and SimPlot, the recombination of JX17 strain was shown to occur in regions which include 5'-terminal S1 gene (20,344 to 22,447 nt), most N gene and 3' UTR (26,163 to 27,648 nt). The pathogenicity study shows that JX17 is a natural low virulent IBV variant which caused respiratory symptoms but no death. Taken together, these results indicate that IBV strains continue to evolve through genetic recombination and three prevalent genotypes in China including QX, TW and 4/91 have started to recombine.

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

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.