Broadly protective vaccines for porcine reproductive and respiratory syndrome and swine influenza virus infections

Pig production is the fastest growing livestock sector across Southeast Asia and intensification of pig production has led to an increase in diseases, including respiratory diseases, which are a major cause of economic losses in the pig industry worldwide. Two viruses, porcine reproductive and respiratory syndrome virus and swine influenza virus, are major contributors to respiratory disease in pigs. Prevention of infection with the two viruses would significantly improve the welfare of pigs in Thailand and minimise economic losses due to respiratory disease. To do this, we will collaborate with Thai scientists to test innovative new vaccines against these two viruses, which will prevent infection and disease.

Because there are many strains of both viruses, the vaccines need to be tailored to the virus strains that circulate in Thailand. Our Thai partners have used their detailed knowledge of these strains and sophisticated molecular biology methods to make vaccine candidates that have the best chance of protecting against the diversity of local viruses.

The candidate vaccines will be tested in the UK to determine whether they stimulate a powerful immune response. Thai scientists will come to the UK to learn these immunological methods. The candidate vaccines that stimulate the most powerful immune response will then be tested in Thailand to see if they can protect pigs against infection with the viruses both under laboratory conditions and in the field.

We wish to understand why these two viruses predispose pigs to severe respiratory disease. To study this question, pigs will be infected with each virus separately or together and the immune responses to each virus will be analysed in detail to learn how the immune response is altered leading to exacerbated disease.

The project will develop broadly-protective vaccines tailored to Thai virus strains and will transfer expertise in immunology and vaccinology to Thai scientists to facilitate the implementation of vaccine programmes for porcine reproductive and respiratory syndrome and swine influenza viruses in Thailand. These technologies can then be adapted to other pathogens and livestock species.

The porcine respiratory disease complex (PRDC) is a major cause of economic losses to the nascent pig industry and poor livestock keepers in Thailand and the wider Southeast Asian region. The porcine reproductive and respiratory syndrome (PRRS) and swine influenza A (SI) viruses that are endemic in Thailand are the two main viral contributors to the PRDC, alone or in combination, together with opportunistic bacterial pathogens. Effective control strategies for PRRS and SI viruses would therefore be of great benefit to the developing Thai pig industry.

Animal health and welfare:
Key aims of this proposal are: first, to develop and test novel PRRS and SI vaccines that are based on virus strains currently circulating in Thailand; second, to determine the effect of PRRS/SI co-infection on the immune response; and third, to transfer expertise in immunological methods for assessing vaccine immunogenicity and in vivo challenge models for testing protective efficacy, from the UK to Thailand.
The principal beneficiary will be the pig farming industry and livestock keepers in Thailand. Effective vaccination against PRRS and SI will improve both productivity and animal welfare. In addition to reducing the costs directly associated with these diseases, there will be additional benefits from reduced secondary infections. Beyond this, we will transfer to Thailand immunological expertise in immunisation and challenge studies that are essential for developing and implementing successful vaccine strategies. This expertise will be invaluable in developing immunisation programmes for further infectious diseases of pigs and other livestock species. The close relationships of Thai scientists with the local biotech industry and government bodies will allow them to fast track the new vaccines into field use.

General public:
Effective immunisation strategies for PRRS and SI will result in increased productivity in the pig industry, protect the livelihoods of smallholders, and lower costs for the consumer. The zoonotic threat posed by swine influenza viruses will also be reduced.

Food security and environment:
Improved PRRS/SI control will reduce antibiotic treatment for secondary bacterial infections, the risk of contamination of the food chain and the environment, as well as the risk of antibiotic resistance. Broadly protective PRRS vaccines will alleviate the threat that the re-emergence of highly pathogenic strains pose to regional food security.

Benefits to policy makers; Benefits to the commercial private sector:
The transfer of expertise in the development and evaluation of vaccines will provide new options for improving animal health, welfare and productivity in the developing Thai pig industry. Production of novel vaccines based on circulating Thai virus strains will be a highly attractive commercial opportunity for the local animal health industry.

Skills, knowledge and training:
A major objective of the proposal is to transfer expertise in pig immunology and in vivo challenge studies to Thailand. The results will indicate if the consensus sequence strategy for PRRS and the non-structural (NS) gene codon de-optimised strategy based on local SI strains, will generate effective broadly-protective vaccines that could be implemented in the field.

International development:
Development of effective vaccine strategies for PRRS and SI in Thailand will lead to improved animal health and welfare and improved productivity in Thailand and the wider Southeast Asian region. It will reduce the zoonotic threat of new influenza strains that may originate in this area through close contact of birds, pigs and humans.