Development of live attenuated vaccine candidates for Newcastle Disease Virus

Lead Research Organisation: St George's University of London
Department Name: Institute of Infection & Immunity

Abstract

The farming of poultry and production of eggs is of growing economic importance to Thailand, as well as other countries in the region, but like all livestock industries, animal production is susceptible to disruption by outbreaks of infectious disease. Newcastle Disease Virus is a major pathogen of birds and causes significant economic losses in first world and developing countries, requiring widespread slaughter policies for control. Although Thailand has remained free from NDV since 2014, neighbouring countries have suffered NDV outbreaks; Thai exports of poultry have correspondingly increased. Keeping flocks free from NDV is thus of paramount importance. Available vaccines are not very effective at protecting birds against genotype VII NDV currently circulating in regions of Asia and elsewhere. In this proposal we aim to use our knowledge of the avian innate immune response to engineer a genotype VII virus to be incapable of evading host innate immunity (specifically the interferon system) and therefore generate a lead candidate for a live attenuated vaccine. Our approach has several interdependent phases: We will initially analyse the properties of the "V" protein of a highly pathogenic ("velogenic") genotype VII NDV as an antagonist of interferon induction or the interferon response and compare this with the "V" protein of an apathogenic ("lentogenic") strain. We will identify key host target proteins that are signalling molecules involved in the interferon system and which interact with the V proteins, and we will validate the importance of these proteins in avian innate immunity using in vitro assays. We will characterise the V/host interactions at the molecular level and will identify V determinants that are essential for interactions. We will then engineer both lentogenic and velogenic (genotype VII) strains of NDV to express altered V proteins that cannot interact with the key host target proteins and by extension which render the virus unable to evade host innate immunity. We will test for attenuation of these viruses by experimental infections in chickens, and we will determine whether this correlates with a failure to block interferon induction or enhanced interferon sensitivity in vivo.

Planned Impact

Economic Impact: The farming of poultry (chickens, ducks and geese) and production of eggs is of growing economic importance to Thailand, as well as other countries in the region, but like all livestock industries, animal production is susceptible to disruption by outbreaks of infectious disease. One of the most serious poultry diseases is caused by Newcastle Disease Virus (NDV). Although Thailand has remained free from NDV since 2014, neighbouring countries have suffered NDV outbreaks; Thai exports of poultry have correspondingly increased. Keeping flocks free from NDV is thus of paramount importance. Available vaccines are not very effective at protecting birds against genotype VII NDV currently circulating in regions of Asia and elsewhere. Although the scale of our proposal is not large or long enough to encompass a complete vaccine development programme, we anticipate that we would generate a "lead candidate" for a genotype VII vaccine. The strategy we propose would be readily applicable to other strains or newly emerging strains as might become necessary. The availability of an effective vaccine against genotype VII would be of significant economic benefit to the Thai poultry industry, protecting livelihoods and exports; smaller producers and household poultry production would also benefit from a cleaner supply chain and decreased opportunities for NDV reservoirs.

Impact on the General Public: An obvious benefit from improved vaccination against NDV will be improved food security (both in supply and in the reassurance that the public will not be consuming contaminated meat), as well as economic benefits as discussed above.

Academic Impact: The proposal poses an important question in host-virus interaction, namely, what contribution does the ability of a paramyxovirus to evade the host's interferon system play in causing pathogenic infections? Although paramyxoviruses are common infectious agents across vertebrates we know surprisingly little about this process. What we are able to learn from studies on NDV in this project will have useful impact to academic virology, immunology, and viral pathogenicity.

Training Impact: The project will employ and train one PDRA in the UK and one Research Assistant in Thailand. The project will expand the technical skills of the PDRA in wet-lab biomedical science (molecular biology, immunology, cell biology), and train the PDRA skills in computation skills and bioinformatics (through analysis of RNAseq data). There is a high demand for such skills in the UK, and we also note that is a limited pool of specialist avian virologists in the UK and this project will help provide a skilled individual. The project will also further develop reverse genetics expertise in Thailand, adding to the expertise available in the host biotechnology institute.

Outreach Impact: We are engaged in communicating our research both to academics through publication and presentation. Additionally, our public engagement activities will ensure that members of the public (e.g. schoolchildren) are aware of the research issue and the wider issue of ensuring food security.

Publications

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Description Although it is early in the grant period we have been successful in mapping the sites of interaction of the V protein of NDV (both genotype VII and LaSota strains) with defined targets in the chicken proteome. We have assessed the impacts of these mutations on the ability of the V protein to antagonise innate immunity and we aim to build these changes into the NDV genome as detailed in the grant application.
Exploitation Route Apart from academic impact, the usefulness of our findings will not be realised as impact until we have been able to test the phenotypes of genetically-altered strains of NDV.
Sectors Agriculture, Food and Drink