Highly pathogenic fowlpox virus in cutaneously infected chickens, China.
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ABSTRACT:
SUBMITTER: Zhao K
PROVIDER: S-EPMC4073872 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Subclinical infection of vaccinated chickens with a highly pathogenic avian influenza A(H5N2) virus was identified through routine surveillance in China. Investigation suggested that the virus has evolved into multiple genotypes. To better control transmission of the virus, we recommend a strengthened program of education, biosecurity, rapid diagnostics, surveillance, and elimination of infected poultry.
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Project description:In order to understand the mechanism of neuroinvasion of a highly pathogenic avian influenza virus (HPAIV) into the central nervous system (CNS) of chickens, specific pathogen free chickens were inoculated with a H7N1 HPAIV. Blood, cerebrospinal fluid (CSF), nasal cavity and brain tissue samples were obtained from 1 to 4 days post-inoculation (dpi) of infected and control chickens. Viral antigen topographical distribution, presence of influenza A virus receptors in the brain, as well as, the role of the olfactory route in virus CNS invasion were studied using different immunohistochemistry techniques. Besides, viral RNA load in CSF and blood was quantified by means of a quantitative real-time reverse transcription-polymerase chain reaction. Viral antigen was observed widely distributed in the CNS, showing bilateral and symmetrical distribution in the nuclei of the diencephalon, mesencephalon and rhombencephalon. Viral RNA was detected in blood and CSF at one dpi, indicating that the virus crosses the blood-CSF-barrier early during infection. This early dissemination is possibly favoured by the presence of Sia?2,3 Gal and Sia?2,6 Gal receptors in brain vascular endothelial cells, and Sia?2,3 Gal receptors in ependymal and choroid plexus cells. No viral antigen was observed in olfactory sensory neurons, while the olfactory bulb showed only weak staining, suggesting that the virus did not use this pathway to enter into the brain. The sequence of virus appearance and the topographical distribution of this H7N1 HPAIV indicate that the viral entry occurs via the haematogenous route, with early and generalized spreading through the CSF.
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Project description:Exosomes are small cell membrane-derived vesicles; they play important roles as mediators of cell-to-cell communication via delivery of their contents, such as proteins and microRNAs (miRNAs). In particular, exosomal miRNAs regulate the gene expression of recipient cells by inhibiting the expression of target mRNAs. In this study, we investigated the miRNA expression profiles of highly pathogenic avian influenza virus (HPAIV) H5N1-infected White Leghorn chickens and analyzed the functions of their target genes. After 3 d of infection with A/chicken/Vietnam/NA-01/2019 (H5N1), exosomes were isolated from the blood serum of White Leghorn chickens for small RNA sequencing. We accordingly identified 10 differentially expressed miRNAs (DE miRNAs; 5 upregulated and 5 downregulated) by comparing the exosomes derived from infected and noninfected chickens. The target genes of DE miRNAs were predicted using miRDB and TargetScan for Gene Ontology and KEGG pathway enrichment analyses. A majority of the target genes was found to be associated with the MAPK signaling pathway; several immune-related genes were identified as being regulated by these DE miRNAs. Moreover, we predicted DE miRNA binding sites in HPAIV RNA segments using the RNAhybrid algorithm. The findings of this study provide a theoretical basis for gaining insights into the regulatory mechanisms of exosomal miRNAs in response to HPAIV H5N1 infection and the identification of novel vaccine candidates.
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Project description:Highly pathogenic avian influenza virus (HPAIV) is a permanent threat due to its capacity to cross species barriers and generate severe infections and high mortality in humans. Recent findings have highlighted the potential role of PB1-F2, a small accessory influenza protein, in the pathogenesis process mediated by HPAIV in mammals. In this study, using a recombinant H5N1 HPAIV (wt) and its PB1-F2-deleted mutant (ΔF2), we studied the effects of PB1-F2 in a chicken model. Unexpectedly, when using low inoculation dose we observed that the wt-infected chickens had a higher survival rate than the ΔF2-infected chickens, a feature that contrasts with what is usually observed in mammals. High inoculation dose had similar mortality rate for both viruses, and comparison of the bio-distribution of the two viruses indicated that the expression of PB1-F2 allows a better spreading of the virus within chicken embryos. Transcriptomic profiles of lungs and blood cells were characterized at two days post-infection in chickens inoculated with the wild type (wt) or the ΔF2 mutant viruses. In lungs, the expression of PB1-F2 during the infection induced pathways related to calcium signaling and repressed a large panel of immunological functions. In blood cells, PB1-F2 was associated with a gene signature specific for mitochondrial dysfunction and down-modulated leucocytes activation. Finally we compared the effect of PB1-F2 in lungs of chickens and mice. We identified that gene signature associated to tissue damages is a PB1-F2 feature shared by the two species; by contrast, the early inhibition of immune response mediated by PB1-F2 observed in chickens is not seen in mice. In summary, our data suggest that PB1-F2 expression deeply affect the immune response in chickens in a way that may attenuate pathogenicity at low infection dose, a feature differing from what was previously observed in mammal species.
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Project description:Highly pathogenic avian influenza H5N8 clade 2.3.4.4 virus caused outbreaks in poultry and unusually high mortality in wild birds in 2016-2017. The pathobiology of one of these viruses was examined in mallards and chickens. High mortality and transmission to direct contacts were observed in mallards inoculated with medium and high doses of the virus. However, in chickens, high mortality occurred only when birds are given the high virus dose and no transmission was observed, indicating that the virus was better adapted to mallards. In comparison with the virus inoculum, viral sequences obtained from the chickens had a higher number of nucleotide changes but lower intra-host genomic diversity than viral sequences obtained from the mallards. These observations are consistent with population bottlenecks occurring when viruses infect and replicate in a host that it is not well adapted to. Whether these observations apply to influenza viruses in general remains to be determined.
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Project description:Cutaneous fowlpox is a disease of chickens and turkeys caused by the fowlpox virus (FWPV), characterized by the development of proliferative lesions and scabs on unfeathered areas. FWPVs regularly carry an integrated, active copy of the reticuloendotheliosis virus (REV), and it has been hypothesized that such FWPVs are more problematic in the field. Extensive outbreaks are usually observed in tropical and sub-tropical climates, where biting insects are more difficult to control. Here, we report an epidemic of 65 cutaneous fowlpox cases in Austria in layer chickens (91% of the cases) and broiler breeders and turkeys, all of them unvaccinated against the disease, from October 2018 to February 2020. The field data revealed appearance in flocks of different sizes ranging from less than 5000 birds up to more than 20,000 animals, with the majority raised indoors in a barn system. The clinical presentation was characterized by typical epithelial lesions on the head of the affected birds, with an average decrease of 6% in egg production and an average weekly mortality of 1.2% being observed in the flocks. A real-time multiplex polymerase chain reaction (PCR) confirmed the presence of FWPV-REV DNA, not only in the lesions but also in the environmental dust from the poultry houses. The integration of the REV provirus into the FWPV genome was confirmed by PCR, and revealed different FWPV genome populations carrying either the REV long terminal repeats (LTRs) or the full-length REV genome, reiterating the instability of the inserted REV. Two selected samples were fully sequenced by next generation sequencing (NGS), and the whole genome phylogenetic analysis revealed a regional clustering of the FWPV genomes. The extensive nature of these outbreaks in host populations naïve for the virus is a remarkable feature of the present report, highlighting new challenges associated with FWPV infections that need to be considered.
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