Dissecting the neutralising antibody response to the porcine reproductive and respiratory syndrome virus to identify novel vaccine targets

Porcine reproductive and respiratory syndrome (PRRS) is the most important infectious disease affecting the global pig industry. PRRS viruses (PRRSV) are a major threat to both animal welfare and food security, as demonstrated by the pig high fever disease outbreak that rapidly spread across Southeast Asia with devastating consequences. Annual losses to PRRSV in the USA and Europe are estimated to exceed US$600 million and 1.5 billion euros, respectively. In the UK almost half of pig herds are infected with PRRSV with costs exceeding £100/sow. PRRSV exists as two genetically and antigenically distinct species, PRRSV-1 and -2, which are both rapidly evolving. The emergence of highly pathogenic strains from both species and the failure of current live attenuated vaccines to provide broad protection against an ever-expanding diversity of viral strains pose significant challenges to effective disease control world-wide. There is therefore an urgent requirement to explore alternative approaches to vaccine development to combat PRRSV. Neutralizing antibodies confer protection against PRRSV and recent studies have shown antibody responses can neutralize a wide diversity of PRRSV strains. An improved understanding of conserved antigenic targets would enable the design of novel vaccines.
Identification of the epitopes recognised by broadly neutralising antibodies is an area of intense recent research in the context of a number of highly variable human viruses. Central to this are methods to generate and analyse the specificity of naturally occurring monoclonal Abs (mAbs). Recent advances in methodologies to analyse antigen-specific B cells and their immunoglobulin genes are now providing large numbers of human mAbs for potential application in the design of novel immunogens.
The advent of next-generation sequencing technologies has opened new approaches to analyse the functional antibody repertoire from immune individuals. Methods have been established that pair the variable sequences of immunoglobulin heavy and light chains from individual B cells thus providing information on native mAbs. Bioinformatics can then be used to create a comprehensive view of the B cell response and to identify clones or clonal families for expression of recombinant mAbs and their functional characterisation. However, these approaches have yet to be established and exploited in the context of the pig. This project aims to adapt these cutting edge technologies to identify and characterise naturally occurring porcine mAbs capable of neutralising PRRSV and to map their reactivity to the minor (GP2a, GP3 and GP4) and major (GP5 and M) envelope proteins of the virus.
The proposed project addresses the urgent need to explore novel approaches to PRRS vaccine development. It is highly relevant to BBSRC strategy; targeting the priorities of animal health, systems approaches to the biosciences and welfare of managed animals. The proposed work combines cutting edge techniques and complimentary disciplines; with the required expertise in PRRS immunology (Graham), immunogenetics (Hammond), structural virology (Grimes) and protein expression (Owens). The project is support by Zoetis (Raue), the largest global animal health company, who will provide an industrial perspective to ensure that upon completion the project is well placed to proceed to the next stages of development.