Award details

Understanding the immune mechanism of host disease resistance and development of marker vaccines and DIVA tests for Peste des Petits Ruminants (PPR)

Reference	BB/L004801/1
Principal Investigator / Supervisor	Professor Satya Parida
Co-Investigators / Co-Supervisors	Professor John Hammond, Dr Jan Kim
Institution	The Pirbright Institute
Department	Livestock Viral Diseases
Funding type	Research
Value (£)	354,143
Status	Completed
Type	Research Grant
Start date	01/10/2014
End date	18/07/2018
Duration	46 months

Abstract

Peste des petits ruminants (PPR) is a highly contagious viral disease of sheep and goats. However little is known about the pathogenesis of PPRV. Importantly, the primary site of viral replication has yet to be properly defined and the mechanism of the contrasting host specific disease resistance to PPR is unknown. Effective live attenuated vaccines are available to control PPR and a c-ELISA kit, to monitor the antibody response against the H protein. However, the critical drawback of these vaccines and associated c-ELISA kits is their inability to differentiate infection in vaccinated animals (DIVA) that slows down the implementation of PPR control through vaccination. Pirbright Institute (PIR) has already rescued the Nigeria 75/1 vaccine strain using reverse genetics techniques. Using the phage display peptide library screening technique, this vaccine has been negatively marked after mutating the epitope recognised by the monoclonal antibody used in the H ELISA. However, this vaccine cannot be used in India due to regulatory requirements of the Indian Government. Therefore, this project will use the above successful techniques to develop similar marker vaccines against contemporary Indian vaccine strains (Sungeri 96 and Arasur 87). Further, it is essential to know the primary site of virus replication for PPR infection for targeted vaccination to generate the rapid and appropriate immune response. Therefore, a virulent recombinant PPR virus containing the GFP will be aerosolised to infect goats and the primary viral replication site will be located by auto fluorescence of GFP and by IHC in tissues. Furthermore, understanding the immune mechanisms underlying the differential susceptibility of sheep, goats using an unbiased transcriptomics approach will enhance our understanding of disease resistance mechanisms.

Summary

Peste des petits ruminants (PPR), also known as 'goat plague', is a highly contagious viral disease of sheep and goats. The direct economic losses of this disease have been estimated to be INR 1800 million (US$ 39 million) annually in India alone, whilst globally, >60% of the small ruminant population is considered at risk. However little is known about the pathogenesis of PPRV. Importantly, the primary site of viral replication has yet to be properly defined and the mechanism of the contrasting host specific disease resistance to PPR is unknown. Effective live attenuated vaccines are available to control PPR and a c-ELISA kit, to monitor the antibody response against the H protein, has been developed at IVRI and Pirbright. However, the critical drawback of these vaccines and associated c-ELISA kits is their inability to differentiate infection in vaccinated animals (DIVA) that slows down the implementation of PPR control through vaccination. We hypothesise that PPRV infects immune cells of the respiratory mucosa, which then migrate to T-cell-rich areas of local lymphoid organs, from which virus enters the general circulation. We aim to develop a recombinant live attenuated DIVA vaccine that will be aerosolised to the primary viral replication site and is capable of generating a rapid and appropriate immune response including mucosal immunity. By further characterising the immune mechanisms underlying the differential susceptibility of sheep, goats and large ruminants to PPRV infection we aim to enhance our understanding of disease resistance mechanisms that will enable the development of better vaccines for the control of PPRV. Aims and objectives: Three complementary research objectives are necessary to advance the ability to control and eradicate PPR: 1) understand PPRV pathogenesis in the pre-viraemic stage to identify the primary site of virus replication as a target for vaccination; 2) further characterise the immune response to PPR in small and large ruminants to understand differential disease resistance; and 3) develop appropriate PPR marker vaccines with associated DIVA tests to provide effective and targeted PPR control, ultimately leading to eradication from India. Research approaches: Similar to our Nigeria75/1 GFP vaccine virus rescue, a virulent recombinant PPR virus containing the GFP gene will be constructed and rescued. This virus will be aerosolised to infect goats. Tissues will be collected from respiratory mucosa and associated lymph nodes and the primary viral replication site will be located by auto fluorescence of GFP and by IHC in tissues. Subsequent vaccinations will use the intranasal route if we define the primary replication site of PPRV during the pre-viremic stage. Using reverse genetics techniques we will develop two negative marker vaccines against Indian PPRV (Sungri 96- goat origin and Arasur 1987- sheep origin). Epitope deletion of a region of the H protein critical for monoclonal antibody binding will allow serological differentiation between vaccinated and naturally infected animals using the current cH-ELISA. For simple and rapid field diagnosis, we intend to develop loop mediated isothermal amplification assay (LAMP) and a lateral flow device. Real-time RT-PCR assay and biosensor assay development and validation in India will help the PPR control programme. Interrogation of the immune mechanisms that underlie the differential susceptibility of species / breeds of small and large ruminants to PPRV will be carried forward using an unbiased transcriptomics approach. Increasing our knowledge on early pathogenesis, using a marker vaccine to generate an appropriate immune response and the ability to differentiate infection from vaccination, in combination with a deeper understanding of immune function will enable the control of PPRV. This project will help in delivering PPR control in India and elsewhere by bringing together major players in PPR research in India and the UK.

Impact Summary

PPR remains endemic in developing countries in Asia, Middle East and Africa except South Africa that do not control borders and animal movements, nor vaccinate systematically on a large scale. PPR is a highly contagious viral disease of sheep and goats. The direct economic losses of this disease have been estimated to be INR 1800 million (US$ 39 million) annually in India alone, whilst globally, >60% of the small ruminant population is considered at risk. Vaccination is key to PPR control plans and eventual eradication in India and other endemic countries. Effective live attenuated vaccines are available to control PPR and a c-ELISA kit, to monitor the antibody response against the H protein. However, the critical drawback of these vaccines and associated c-ELISA kits is their inability to differentiate infection in vaccinated animals (DIVA) that slows down the implementation of PPR control through vaccination. This project will support UK policy on food security, major investment in India on PPR control, and the research aims of the Global PPR Research Alliance (GPRA) for future eradication. It will strengthen multidisciplinary collaborations between science and industry, virology, molecular biology, mathematics and epidemiology. The complementary partnership will diversify the impact, broadening scientific outreach and providing channels to influence both policy and implementation of disease control. As World Reference Laboratory for PPR, PIR is the global coordinating centre for labs engaged in regional PPR control activities mainly by training personels from endemic countries . IVRI in India work as National reference laboratory for PPR in India and is responsible for PPR control in India. OIE and FAO both are actively engaged in control policy of PPR throughout world. For the first time after seeing the devastating situation in DRC, OIE has established a PPR vaccine bank to help countries for control through vaccination. Recently PPR has spread to European part of Turkey and Northern Africa and become a threat to whole Europe. The common wildlife present in Europe and Turkey may bring the disease to Europe any time. EC is recently concern about this and recognise the role of wildlife for PPR spread. PI at Pir has already developed a marker vaccine for Nigeria/75/1 PPR vaccine strain. However this cannot be used in India due to regulation imposed by Government. Therefore marker vaccine development for Indian vaccine strain is the main objective of this project. With the existing experience of reverse genetics techniques, the project will able to produce marker vaccine for PPR in India. The existing tests both at IVRI and Pirbright will work as DIVA test as the epitope against monoclonal used in this test will be mutated in vaccine virus. Therefore the test will work as a DIVA test and can detect infection in vaccinated animals. The other benefit from project will be to start a targeted vaccination targeting the primary replication site of virus in natural infection. This will generate a quick immune response in animals. The cause of this host specific disease resistance in PPR is unknown. Therefore characterisation of the immune response to PPR in small and large ruminants to understand differential disease resistance is necessary. Exploring this complete / relative disease resistant phenomenon across species / breeds may offer an alternate strategy for disease control with the following advantages. 1.Recommendation of particular resistant breeds in high disease prone areas 2.Selection of individuals that have high levels of disease resistance or tolerance for breeding purposes, if molecular markers are identified 3.Gene 'interogression' through cross-breeding to introduce 'resistant' genes into susceptible breeds

Committee	Research Committee A (Animal disease, health and welfare)
Research Topics	Animal Health, Immunology, Microbiology
Research Priority	X – Research Priority information not available
Research Initiative	Farmed Animal Disease and Health (FADH) [2013]
Funding Scheme	X – not Funded via a specific Funding Scheme

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