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.

Phillygenin activates PKR/eIF2α pathway and induces stress granule to exert anti-avian infectious bronchitis virus

The prevalence of avian infectious bronchitis virus (IBV) is still one of causes inducing severe losses of production in the poultry industry worldwide. Vaccination does not completely prevent IBV infection and spread due to immune failure and viral mutations. ForsythiaeFructus and its compounds have been widely used in a lot of prescriptions of the traditional Chinese medicine for a long history, and it is well-known as safety and efficiency in heat-clearing and detoxifying. This study aims to investigate the anti-IBV activity and mechanism of phillygenin. The results showed that phillygenin inhibited IBV replication by disturbing multiple stages of the virus life cycle, including viral adsorption, invasion, internalization, and release in Vero cells. After being treated with 100, 125 and 150 μg/mL phillygenin, the expression of G3BP1 was significantly increased and the phosphorylation of PKR/eIF2α was activated, which increased stress granule, thereby triggering the antiviral response in Vero cells. The anti-virus activity of PHI was decreased when G3BP1 was interfered by si-RNA, and G3BP1 was down-regulated when PKR/eIF2α was interfered by si-RNA. In conclusion, our findings indicate that phillygenin activates PKR/eIF2α pathway and induces stress granule formation to exert anti-IBV, which holds promise to develop into a novel anti-IBV drug. Further study in vivo is needed to explore phillygenin as a potential and effective drug to prevent IB in poultry.

Comparative trachea transcriptome analysis in SPF broiler chickens infected with avian infectious bronchitis and avian influenza viruses

Infectious bronchitis virus (IBV) and avian influenza virus (AIV) are two major respiratory infections in chickens. The coinfection of these viruses can cause significant financial losses and severe complications in the poultry industry across the world. To examine transcriptome profile changes during the early stages of infection, differential transcriptional profiles in tracheal tissue of three infected groups (i.e., IBV, AIV, and coinfected) were compared with the control group. Specific-pathogen-free chickens were challenged with Iranian variant-2-like IBV (IS/1494), UT-Barin isolates of H9N2 (A/chicken/Mashhad/UT-Barin/2017), and IBV-AIV coinfection; then, RNA was extracted from tracheal tissue. The Illumina RNA-sequencing (RNA-seq) technique was employed to investigate changes in the Transcriptome. Up- and downregulated differentially expressed genes (DEGs) were detected in the trachea transcriptome of all groups. The Kyoto Encyclopedia of Genes and Genomes pathway and Gene Ontology databases were examined to identify possible relationships between DEGs. In the experimental groups, upregulated genes were higher compared to downregulated genes. A more severe immune response was observed in the coinfected group; further, cytokine-cytokine receptor interaction, RIG-I-like receptor signaling, Toll-like receptor signaling, NOD-like receptor signaling, Janus kinase/signal transducer, and activator of transcription, and apoptotic pathways were important upregulated genes in this group. The findings of this paper may give a better understanding of transcriptome changes in the trachea during the early stages of infection with these viruses.

The mechanism of antigen-presentation of avian bone marrowed dendritic cells suppressed by infectious bronchitis virus

Dendritic cells are first guard to defend avian infectious bronchitis virus (IBV) infection and invasion. While IBV always suppress dendritic cells and escape the degradation and presentation, which might help viruses to transfer and migrant. Initially, we compared two IBV's function in activating avian bone marrow dendritic cells (BMDCs) and found that both IBV (QX and M41) did not significantly increase surface marker of avian BMDCs. Moreover, a significant decrease of m⁶A modification level in mRNA, but an increased in the ut RNA were observed in avian BMDCs upon the prevalent IBV (QX) infection. Further study found that both non-structural protein 7 (NSP7) and NSP16 inhibited the maturation and cytokines secretion of BMDCs, as well as their antigen-presentation ability. Lastly, we found that gga-miR21, induced by both NSP7 and NSP16, inhibited the antigen presentation of avian BMDCs. Taken together, our results illustrated how IBV inhibited the antigen-presentation of avian DCs.

Pathogenicity and genome changes in QX-like infectious bronchitis virus during continuous passaging in embryonated chicken eggs

Infectious bronchitis (IB) remains a major problem in the global poultry industry despite the many available vaccines. Live attenuated vaccines are the most effective means of preventing IB and are traditionally generated by serial passaging of a wild strain in embryonated chicken eggs. In this study, the SZ isolate of the QX-like infectious bronchitis virus (IBV) was continuously passaged in chicken embryos for 250 passages. We compared the pathogenicity of different passages (SZ50, SZ100, SZ150, SZ200 and SZ250) of strain SZ by clinical signs, gross lesions, viral load, tissue tropism, weight gain and tracheal ciliary activity. As the passaging increased in the chicken embryos, the strain lost its ability to infect many organs, and the viral pathogenicity gradually decreased. We also found 23 genomic variations of the QX-like strain SZ throughout the passaging process by further analyzing its complete genome sequence. This work offers valuable insight for IBV vaccine development and further research on the IBV attenuation mechanisms.

Expression and immunoreactivity of a recombinant multi-epitope antigen designed based on four major structural proteins of avian infectious bronchitis virus

The development of rapid, simple, and sensitive diagnostic methods for identification of avian infectious bronchitis virus (IBV) is crucial for the effective control of avian infectious bronchitis. In the present study, a tandemly arranged multiepitope peptide (named SEMN) was designed with four antigenic regions derived from four major structural proteins of IBV. Then, we performed codon optimization of SEMN gene by changing the codon-adaptation index from 0.45 to 0.94 and expressed the optimized gene in codon bias-adjusted Escherichia coli Rosetta (DE3), followed by determination of the immunoreactivity of the purified protein. Bioinformatics analysis of SEMN showed a high antigenicity, surface probability and hydrophilicity. The recombinant protein rSEMN was expressed both in soluble forms and as inclusion bodies, and the molecular weight of rSEMN was about 39 kDa. The preliminary diagnostic performance of rSEMN was confirmed by Western blotting analysis using chicken anti-IBV polyclonal antibodies. Further studies are needed to evaluate the immunogenicity in animal models and to give a final assessment of the diagnostic utility of this recombinant multi-epitope antigen.

Genotyping of avian infectious bronchitis virus in Iran: Detection of D274 and changing in the genotypes rate

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An updating data about avian infectious bronchitis genotypes circulating in Iran.

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First detection of D274 genotype in Iran.

The coronavirus avian Infectious bronchitis virus (IBV) poses economic threats to poultry farms worldwide, affecting the performance of both meat-type and egg-laying birds. To define the evolution of recent IBVs in Iran, a genetic analysis based on hypervariable nucleotide sequences of S1 gene was carried out. Tracheal swab samples were collected from 170 Broiler flocks during 2017. Ten tracheal swabs from each flock pooled. From a total number of 170 flocks tested, 84.71% found to be positive. Phylogenetic tree analysis revealed the presence of D274 as a first time in Iran. IS/1494/06 was showed to be dominant IBV type circulating in broiler farms with a significantly higher prevalence than other four genotypes. Considering fluctuations in QX-type prevalence in recent years, continuous monitoring is necessary to reduce economic consequences in layer and broiler farms. The findings highlight the importance of using modified vaccination strategies that are adapted to the changing disease scenario.

Complete genome analysis of Iranian IS-1494 like avian infectious bronchitis virus

The nephropathogenic infectious bronchitis virus (IBV) strain IS-1494 like (variant-2; GI-23) was first isolated in the Middle East (1998). Despite intensive vaccinations, IS-1494 like IBVs are still circulating in Iran (the dominant genotype) and spread to other countries. Here, the full-length genome of this Iranian IS-1494 like IBV was (Mahed) determined to understand its evolutionary relationships. The genome consists of 27,652 nucleotides, with mutations in most of the structural genes. Thirteen open reading frames (ORFs) were predicted in the Mahed isolate (5' UTR-1a-1b-S-3a-3b-E-M-4b-4c-5a-5b-N-6b-3' UTR). ORFs 4b, 4c, and 6b, which has rarely been reported, were present in the Mahed genome. According to phylogenetic analysis of the full-length genome, 1a, S2, M, E, N protein, Mahed isolate clustered with the QX type strain. Based on the partial 1b, S1, Mahed clustered with the Q1 strain. The full-length genome of Mahed isolate shared the highest sequence homology with Gray and JMK (90.06-90.07%) and was least related to the Vic-s (86.21%). These data show that evolutionary variation because of recombination in IBV plays a major role in the adaptation and origin of IBV leading to new genetic and types of the virus strain.

Inactivated infectious bronchitis virus vaccine encapsulated in chitosan nanoparticles induces mucosal immune responses and effective protection against challenge

Avian infectious bronchitis virus (IBV) is one of the most important viral diseases of poultry. The mucosa of upper respiratory tract, specially the trachea, is the primary replication site for this virus. However, conventional inactivate IBV vaccines usually elicit reduced mucosal immune responses and local protection. Thus, an inactivated IBV vaccine containing BR-I genotype strain encapsulated in chitosan nanoparticles (IBV-CS) was produced by ionic gelation method to be administered by oculo-nasal route to chickens. IBV-CS vaccine administered alone resulted in markedly mucosal immune responses, characterized by high levels of anti-IBV IgA isotype antibodies and IFNγ gene expression at 1dpi. The association of live attenuated Massachusetts IBV and IBV-CS vaccine also induced strong mucosal immune responses, though a switch from IgA isotype to IgG was observed, and IFNγ gene expression peak was late (at 5 dpi). Efficacy of IBV-CS was evaluated by tracheal ciliostasis analysis, histopathology examination, and viral load determination in the trachea and kidney. The results indicated that IBV-CS vaccine administered alone or associated with a live attenuated heterologous vaccine induced both humoral and cell-mediated immune responses at the primary site of viral replication, and provided an effective protection against IBV infection at local (trachea) and systemic (kidney) sites.

Attenuation, safety, and efficacy of a QX-like infectious bronchitis virus serotype vaccine

Avian infectious bronchitis (IB) is a highly contagious disease caused by avian infectious bronchitis virus (IBV), which is a considerable economic threat to the poultry industry. QX-like IBV strains have increasingly emerged in China in recent years. Hence, development of a specific vaccine to guard against their potential threat is important. In this study, we sought to develop an attenuated vaccine strain. First, attenuated QX-like IBV strain SZ130 was created by continuous passage in chicken embryos for 130 generations, and then its safety was tested. We also evaluated the protective efficacy of different doses of SZ130 against challenge with QX-like IBV field strain SD in chickens. SZ130-infected birds did not experience IB-like signs and organ lesions. Additionally, an excellent protective effect of SZ130 vaccination was observed when vaccinated birds were challenged with SD, with no clinical signs or gross lesions, decreased target tissue replication rates, and lower ciliostasis scores in all immunized groups. These findings indicate that attenuated IBV strain SZ130 is highly safe in chicks and may serve as an effective vaccine against the threat posed by QX-like IBV strains.

Co-circulation of three clusters of 793/B-like avian infectious bronchitis virus genotypes in Iranian chicken flocks

Avian infectious bronchitis (IB) is an acute and highly contagious viral disease causing severe economic losses in the poultry industry. The 793/B IB virus is an important infectious bronchitis virus (IBV) genotype currently circulating in several countries, including Iran. One hundred confirmed IBV samples (between 2014 and 2015; from 15 provinces in Iran) were selected for genotyping based on S1 sequencing. After phylogenetic analysis, it was found that 30% of the IBV isolates belonged to the 793/B genotype. Results showed that the Iranian 793/B-like IBV isolates could be divided in to three clusters: 4/91-like (50%), 1/96-like (40%), and IB88-like (10%). The sequence similarity between Iranian 793/B-like IBV isolates is 87.69%-100%. The highest identity is between the 4/91 and IB88 clusters (96.38%), and the lowest similarity is between the 1/96 and IB88 clusters (87.62%). This study provides a comprehensive analysis of 793/B-type IBV in Iran and characterization of IBV molecular epidemiology in the country.

Analysis of antigenicity and pathogenicity reveals major differences among QX-like infectious bronchitis viruses and other serotypes

Avian coronavirus infectious bronchitis virus (IBV) causes considerable damage to the poultry industry worldwide and the proportion of QX-like genotype isolates have increased over time. Here, to better understand the antigenicity and pathogenicity of this genotype, we conducted sequence analyses, cross neutralization tests, and also examined the pathogenicity of two strains, SD and SZ. Sequence analyses revealed that SD and SZ isolates belong to the QX-like IBV genotype and share high homology in their full-length genomes. Cross neutralization tests showed high cross neutralization between SD and SZ, but distant relationships with other representative strains of the classical IBV serotypes. Virus infection experiments showed that SD caused high mortality with strong respiratory and renal pathogenicity in chickens, whereas SZ caused milder lesions by comparison. This study highlights the big discrepancy in antigenicity that exists between QX-like strains and other serotypes. Collectively, these findings provide important information about the epidemiology and pathogenicity of IBV, which may benefit the control of IB in the poultry industry.

CpG-ODNs induced changes in cytokine/chemokines genes expression associated with suppression of infectious bronchitis virus replication in chicken lungs

The process of virus replication in host cells is greatly influenced by the set of cytokines, chemokines and antiviral substances activated as a result of host–virus interaction. Alteration of cytokines profiles through manipulation of the innate immune system by innate immune stimulants may be helpful in inhibiting virus replication in otherwise permissive cells. The aim of present studies was to characterize innate immune responses capable of inhibiting infectious bronchitis virus (IBV) replication in chicken lungs after in ovo administration of CpG ODN. In our experiments, CpG ODN 2007 or PBS solution was injected on 18th embryonic day (ED) via the chorioallontoic route. CpG ODN and PBS inoculated embryos were challenged with virulent IBV on the 19th ED. Lung tissue samples from experimental chicks were analysed for cytokines/chemokines gene expression at 24 h, 48 h, and 72 h, post infection. Our data showed significant differential up-regulation of IFN-γ, IL-8 (CXCLi2) and MIP-1β genes and suppression of IL-6 gene expression being associated with inhibition of IBV replication in lungs tissue retrieved from embryos pre-treated with CpG ODN.

It is expected that understanding of the innate immune modulation of target tissues by the virus and innate immune stimulants will be helpful in identification of valuable targets for development of novel, safe, effective and economical control strategies against IBV infection in chickens.

Origin and characteristics of the recombinant novel avian infectious bronchitis coronavirus isolate ck/CH/LJL/111054

Recombination among infectious bronchitis viruses (IBVs), coupled with point mutations, insertions, and deletions that occur in the genome, is thought to contribute to the emergence of new IBV variants. In this study an IBV, ck/CH/LJL/111054, was isolated from a H120-vaccinated chicken, which presented with a suspected IBV infection. Phylogenetic analysis of the S1 subunit sequence confirmed that strain ck/CH/LJL/111054 is of the Connecticut-type; however, further extensive full-length genomic analysis identified the occurrence of recombination events. Therefore, strain ck/CH/LJL/111054 may have originated from recombination events between Conn- and Mass-like strains at three recombination breakpoints: two located within the nsp3 gene sequence and one in the nsp12 gene sequence. Further, the uptake of the 5' untranslated regions, nsp2, parts of nsp3, nsp4-11, and parts of nsp 12 from Mass-like virus by ck/CH/LJL/111054 might have resulted in changes in viral replication efficiency rather than antigenic changes, via cross-neutralization analysis with the H120 strain. Recombination events coupled with the accumulation of mutations in the ck/CH/LJL/111054 genome may account for its increased virulence in specific-pathogen free chickens.

Evaluation of sialic acid and acute-phase proteins (haptoglobin and serum amyloids A) in healthy and avian infection bronchitis virus-infected chicks

Forty-five 24-day-old Cobb chicks infected with infectious bronchitis virus (IBV) and ten healthy 24-day-old Cobb chicks without any clinical signs of IBV as control group were selected for the study. All of the diseased chicks showed some or all of the clinical signs of infectious bronchitis including gasping, coughing and nasal discharge, wet eyes, swollen sinuses, reduction of food consumption and weight gain. Diagnosis of IBV was based on clinical signs and ELISA test. Blood samples were taken from the wing vein into two tubes: one containing ethylenediaminetetraacetic acid (EDTA) and one without EDTA. Haptoglobin (Hp), serum amyloid A (SAA), total sialic acid (TSA), lipid-bound sialic acid (LBSA) and protein-bound sialic acid (PBSA) concentrations were measured. All of the study variables were significantly higher in diseased birds compared with control group. Results showed that there were significant positive correlations between TSA, LBSA and PBSA in both groups. No correlation was observed between Hp and SAA with any other parameters; however, there was significant negative correlation between Hp and SAA in the control group. Results for receiver operating characteristic analysis showed that area under the curve (AUC) for TSA, LBSA, PBSA, Hp and SAA were 0.93, 0.98, 0.90, 0.90 and 0.80, respectively. According to AUC, LBSA was the most sensitive factor to change in the diseased birds. It can be concluded that in naturally occurring IBV infection, significant increases in TSA, LBSA, PBSA, Hp and SAA concentrations are expected and among study variables, LBSA had the most obvious change so it may be considered as the most sensitive parameter.