Innate immune sensing of viral DNA by avian macrophages

Lead Research Organisation: University of Cambridge
Department Name: Pathology

Abstract

Chickens are a globally important food source and hence require protection from infectious diseases. The poultry industry in the UK alone is responsible for the production of more than one million tonnes of chicken meat and billions of eggs every year for consumption. This vast scale of farming necessitates that we understand which diseases pose a threat to the health of these chickens and how we can counter those threats. The use of vaccines is one a primary method used to help protect chickens from infections such as Newcastle disease, infectious bronchitis, fowlpox and Marek's disease. In order to effectively improve current vaccines or design new ones against emerging and zoonotic infections it is important to understand the fundamental mechanisms by which the chicken immune system works and how it interacts with pathogens. Such studies can lead not only to improvements in vaccine design but also to a greater understanding of immunology and virology as a whole. Indeed, the study of avian immunology and virology has lead to several important advances in both fields. In this study we aim to advance our understanding of how chicken cells detect the presence of DNA in the wrong place inside the cell. Such a mis-localisation can be a sign of infection or damage that triggers an alarm called the innate immune system to send signals into the infected or damaged tissue that something is wrong. This system is critical to fight off infections and to drive vaccination responses so understanding how it works will help in the fight against diseases such as Marek's that affect global chicken populations.

Technical Summary

To mount an effective immune response to infection requires sensing and responding to pathogens in the first infected cells. The pattern recognition receptors (PRRs) that directly sense the presence of foreign DNA inside host cells are critical for mounting a rapid and effective innate immune response to virus infections. Despite being extensively studied in mammalian systems, the PRRs that sense viral DNA are not well defined in chickens and their function in pathogen defence poorly characterised. In this study we aim to identify the PRRs responsible for sensing intracellular DNA and analyse the innate sensing pathways that they trigger. There are two key signalling outputs that result from DNA-PRR stimulation; the activation of interferon regulatory factor (IRF)-dependent type-I interferon (IFN-I) and chemokine transcription and inflammasome-dependent interleukin-1beta (IL-1B) processing and secretion. Our preliminary data indicates that these responses are conserved in chicken macrophages, providing the basis by which we can identify and analyse the contribution of DNA sensing PRRs to these signalling responses. Using a combination of genome editing, PRR stimulation, inhibitor studies and infection with Marek's disease virus (MDV) we will analyse the contribution of these PRRs to anti-viral innate responses. We will carry out experiments in a macrophage cell line and confirm our findings in primary bone-marrow derived macrophages. These data will provide important mechanistic information about how chickens mount an immediate immune response to MDV and other DNA viruses as well as to DNA-containing vaccine vectors.

Planned Impact

In this project we will carry out basic scientific research that will lead to an improved understanding of how DNA drives innate immune responses in chickens.
Our study will further the academic discipline through contributing to the training of researchers skilled in a wide range of techniques. The PDRA and RA will acquire new expertise in immunology and virology research which would be widely applicable in the UK biotech industry as well as contributing to training and teaching other laboratory members. In addition, we will have a number of students in the lab over the course of the grant who will also acquire both specialised and transferable skills. These lab members will improve other transferable skills via presentations and networking opportunities at conferences and writing papers and reports during the course of the grant.
Our findings will be disseminated in open access peer-reviewed journals, presentations at suitable scientific conferences, such as the Cambridge Immunology Forum, a Keystone vaccinology conference and other meetings where appropriate to the obtained experimental results. Additionally we will advertise on-line the key facts from our research on our website which will link to any publications and will notify of BBSRC support. Such information will be provided in lay terms as well as more technically in such that it is suitable for all interested parties.
As an method to improve public engagement BF is a Science/Technology/Engineering and Maths (STEM) Ambassador allowing opportunities to interact with and to present this work to young people. The PDRA and RA will be encouraged to engage in such activities and coached by the applicant where necessary.

Publications

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