The Gammacoronavirus infectious bronchitis virus (IBV) is a highly contagious economically important respiratory pathogen of domestic fowl. Reverse genetics allows for the molecular study of pathogenic determinants to enable rational vaccine design. The recombinant IBV (rIBV) Beau-R, a molecular clone of the apathogenic Beaudette strain, has previously been investigated as a vaccine platform. To determine tissues in which Beau-R could effectively deliver antigenic genes, an in vivo study in chickens, the natural host, was used to compare the pattern of viral dissemination of Beau-R to the pathogenic strain M41-CK. Replication of Beau-R was found to be restricted to soft tissue within the beak, whereas M41-CK was detected in beak tissue, trachea and eyelid up to seven days post infection. In vitro assays further identified that, unlike M41-CK, Beau-R could not replicate at 41 °C, the core body temperature of a chicken, but is able to replicate a 37 °C, a temperature relatable to the very upper respiratory tract. Using a panel of rIBVs with defined mutations in the structural and accessory genes, viral replication at permissive and non-permissive temperatures was investigated, identifying that the Beau-R replicase gene was a determinant of temperature sensitivity and that sub-genomic mRNA synthesis had been affected. The identification of temperature sensitive allelic lesions within the Beau-R replicase gene opens up the possibility of using this method of attenuation in other IBV strains for future vaccine development as well as a method to investigate the functions of the IBV replicase proteins.
Aim: Gestational diabetes mellitus (GDM) has been linked with adverse long-term health outcomes for the fetus and mother. These effects may be mediated by epigenetic modifications. Materials & methods: Genome-wide RNA sequencing was performed in placental tissue and maternal blood in six GDM and six non-GDM pregnancies. Promoter region DNA methylation was examined for selected genes and correlated with gene expression to examine an epigenetic modulator mechanism. Results: Reductions of mRNA expression and increases in promoter methylation were observed for G6PD in GDM women, and for genes encoding IGF-binding proteins in GDM-exposed placenta. Conclusion: GDM involves epigenetic attenuation of G6PD, which may lead to hyperglycemia and oxidative stress, and the IGF-axis, which may modulate fetal macrosomia.
The coronaviruses are a large family of enveloped RNA viruses that commonly cause gastrointestinal or respiratory illnesses in the infected host. Avian coronavirus infectious bronchitis virus (IBV) is a highly contagious respiratory pathogen of chickens that can affect the kidneys and reproductive systems resulting in bird mortality and decreased reproductivity. The interferon-inducible transmembrane (IFITM) proteins are activated in response to viral infections and represent a class of cellular restriction factors that restrict the replication of many viral pathogens. Here, we characterize the relative mRNA expression of the chicken IFITM genes in response to IBV infection, in vivo, ex vivo and in vitro using the pathogenic M41-CK strain, the nephropathogenic QX strain and the nonpathogenic Beaudette strain. In vivo we demonstrate a significant upregulation of chIFITM1, 2, 3 and 5 in M41-CK- and QX-infected trachea two days post-infection. In vitro infection with Beaudette, M41-CK and QX results in a significant upregulation of chIFITM1, 2 and 3 at 24 h post-infection. We confirmed a differential innate response following infection with distinct IBV strains and believe that our data provide new insights into the possible role of chIFITMs in early IBV infection.
The human IL-1 receptor family is comprised of 11 membrane bound or soluble receptors and the IL-18 binding protein (IL-18BP). These receptors are dispersed across seven genomic loci, with the majority at a single locus. Direct orthologues were identified in the chicken at conserved genomic loci; however, the IL-18BP remained absent from the first four builds of the chicken genome sequence. Subsequent assemblies identified the gene at a locus syntenic with mammals; however, these predicted sequences differed between genome builds and contained multiple errors. A partial IL-18BP-like sequence in the NCBI EST database was used to clone the full-length cDNA. A splice variant, which lacks the exon that encodes part of the signal peptide, was also cloned. Human IL-18BP is differentially spliced to produce a number of variants, which are all secreted. By contrast, the spliced chicken isoform was predicted to be intracellular, and we identified similar variants with the same exon missing in a limited number of divergent vertebrate species. Mammalian and viral IL-18BPs inhibit IL-18 activity by directly binding to this cytokine. Full-length and intracellular chicken IL-18BPs were equally effective at inhibiting IL-18-mediated IFN-γ release from an avian B-cell line. Analysis of the predicted chIL-18BP protein sequence revealed two crucial residues, which account for 50% of the binding affinity between human IL-18 and IL-18BP, are conserved in the chicken and a fowlpox-encoded homologue, fpv214. This suggests specific fowlpox viruses used in humans as a vaccine vector have the potential to dampen anti-viral host immune responses.
Infectious Bronchitis Virus (IBV) is a gammacoronavirus that is prevalent in commercial chicken flocks, resulting in characteristic clinical signs including snicking, rales, decreased tracheal ciliary activity, reduced weight gain and reduced egg production. Preliminary results indicate that there is a different clinical response to IBV infection in different chicken lines. Therefore, we aim to determine whether there is a differential innate or humoral immune response to IBV between chicken lines. A series of in vivo experiments were conducted comparing brown leghorns (Rhode Island Red, RIR (Roslin)) to white leghorns (from Valo and Ovagen). Trachea and bursa were collected from infected and control birds at four-, six- and fourteen-days post infection (dpi). There was a difference in snick rate and rales between the RIRs and the white leghorns (both lines). However, no difference was observed in ciliary activity. Viral load was determined by absolute quantification using qRT-PCR. The viral load in the trachea of RIRs was significantly lower (p<0.05) at 6 dpi compared to 4 dpi, unlike in Ovagen birds where there was no significant difference between the timepoints. Relative gene expression of IFN-α, IFN-β, IFN-γ, IL-6 and IL-1β in these tissues will be measuredby qRT-PCR. Serum was processed from whole blood collected at zero and ten dpi for use in IBV specific ELISAs which will measure antibody responses in the chicken lines. This project aims to explore immune responses against IBV as well as identifying the causes of variability in experimentation using chickens to investigate IBV infection.
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