Characterization of interleukin-1beta mRNA expression in chicken macrophages in response to avian reovirus

Autophagy induced by avian reovirus enhances viral replication in chickens at the early stage of infection

Background

Avian reovirus (ARV) is an important pathogen that can cause serious disease in poultry. Though several in vitro studies revealed some molecular mechanisms that are responsible for ARV-induced autophagy, it is still largely unknown how ARV manipulates autophagy to promote its own propagation.

Results

In this study, we demonstrated that ARV infection triggered autophagy in chicken tissues, evident from the enhancement of LC3-I/−II conversion and the appearance of abundant autophagosomes. Moreover, viral replication and the expression of IL-1β were coupled with the process of ARV-induced autophagy in the early stage of infection. Furthermore, regulation of autophagy affected the accumulation of LC3-II, the production of ARV and the expression of IL-1β.

Conclusions

Altogether, our data suggest that ARV induces autophagy, which benefits its replication and dissemination in chicken tissues at the early infection stage.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1926-5) contains supplementary material, which is available to authorized users.

The NS segment of H5N1 avian influenza viruses (AIV) enhances the virulence of an H7N1 AIV in chickens

Some outbreaks involving highly pathogenic avian influenza viruses (HPAIV) of subtypes H5 and H7 were caused by avian-to-human transmissions. In nature, different influenza A viruses can reassort leading to new viruses with new characteristics. We decided to investigate the impact that the NS-segment of H5 HPAIV would have on viral pathogenicity of a classical avian H7 HPAIV in poultry, a natural host. We focussed this study based on our previous work that demonstrated that single reassortment of the NS-segment from an H5 HPAIV into an H7 HPAIV changes the ability of the virus to replicate in mammalian hosts. Our present data show that two different H7-viruses containing an NS-segment from H5–types (FPV NS GD or FPV NS VN) show an overall highly pathogenic phenotype compared with the wild type H7–virus (FPV), as characterized by higher viral shedding and earlier manifestation of clinical signs. Correlating with the latter, higher amounts of IFN-β mRNA were detected in the blood of NS-reassortant infected birds, 48 h post-infection (pi). Although lymphopenia was detected in chickens from all AIV-infected groups, also 48 h pi those animals challenged with NS-reassortant viruses showed an increase of peripheral monocyte/macrophage-like cells expressing high levels of IL-1β, as determined by flow cytometry. Taken together, these findings highlight the importance of the NS-segment in viral pathogenicity which is directly involved in triggering antiviral and pro-inflammatory cytokines found during HPAIV pathogenesis in chickens.

Characterization of host responses against a recombinant fowlpox virus-vectored vaccine expressing the hemagglutinin antigen of an avian influenza virus

There currently are commercial fowlpox virus (FPV)-vectored vaccines for use in chickens, including TROVAC-AIV H5, which expresses the hemagglutinin (HA) antigen of an avian influenza virus and can confer immunity against avian influenza in chickens. Despite the use of recombinant FPV (rFPV) for vaccine delivery, very little is known about the immune responses generated by these viruses in chickens. The present study was designed to investigate host responses to rFPV in vivo and in vitro. In cultured cells infected with TROVAC-AIV H5, there was an early increase in the expression of type I interferons (IFN), Toll-like receptors 3 and 7 (TLR3 and TLR7, respectively), TRIF, and MyD88, which was followed by a decrease in the expression of these genes at later time points. There also was an increase in the expression of interleukin-1beta (IL-1beta), IL-8, and beta-defensin genes at early time points postinfection. In chickens immunized with TROVAC-AIV H5, there was higher expression of IFN-gamma and IL-10 at day 5 postvaccination in spleen of vaccinated birds than in that of control birds. We further investigated the ability of the vaccine to induce immune responses against the HA antigen and discovered that there was a cell-mediated response elicited in vaccinated chickens against this antigen. The findings of this study demonstrate that FPV-vectored vaccines can elicit a repertoire of responses marked by the early expression of TLRs, type I interferons, and proinflammatory cytokines, as well as cytokines associated with adaptive immune responses. This study provides a platform for designing future generations of rFPV-vectored vaccines.

Application of chicken microarrays for gene expression analysis in other avian species

BACKGROUND

With the threat of emerging infectious diseases such as avian influenza, whose natural hosts are thought to be a variety of wild water birds including duck, we are armed with very few genomic resources to investigate large scale immunological gene expression studies in avian species. Multiple options exist for conducting large gene expression studies in chickens and in this study we explore the feasibility of using one of these tools to investigate gene expression in other avian species.

RESULTS

In this study we utilised a whole genome long oligonucleotide chicken microarray to assess the utility of cross species hybridisation (CSH). We successfully hybridised a number of different avian species to this array, obtaining reliable signals. We were able to distinguish ducks that were infected with avian influenza from uninfected ducks using this microarray platform. In addition, we were able to detect known chicken immunological genes in all of the hybridised avian species.

CONCLUSION

Cross species hybridisation using long oligonucleotide microarrays is a powerful tool to study the immune response in avian species with little available genomic information. The present study validated the use of the whole genome long oligonucleotide chicken microarray to investigate gene expression in a range of avian species.