Porcine reproductive and respiratory syndrome (PRRS) emerged almost simultaneously in Western Europe and North America during the late 1980s, presenting as respiratory disease in young piglets and reproductive failure in sows. The aetiologic agent of PRRS was identified as the PRRS virus (PRRSV), an enveloped, single-stranded, positive sense RNA Arterivirus (order Nidovirales), with European viruses (genotype 1) sharing only 55–70% nucleotide identity with American (genotype 2) strains. PRRS is now the most economically important disease for the global pig industry, with losses estimated to exceed $664 million annually in the USA alone. A lack of proof-reading enzyme means that PRRSV replication is associated with a high mutation rate. Consequently, PRRSV is rapidly evolving with an ever expanding genetic variation existing within each genotype. PRRSV evolution has also meant that in addition to the familiar endemic and chronic PRRS disease, outbreaks of more severe disease have occurred periodically. The emergence of highly pathogenic strains of PRRSV-2 in China resulted in the deaths of millions of animals and threatened food security. These highly pathogenic strains rapidly spread and have now become the predominant strains circulating in the South East Asia region. Most recently PRRSV-1 strains from Eastern Europe have been described which are significantly more pathogenic than conventional European strains raising concerns over the evolution of the disease on this continent. Both inactivated and live attenuated PRRS vaccines are widely available. However inactivated vaccines fail to provide heterologous protection and whilst live vaccines are more efficacious they can revert to virulence and recombine with field strains. More effective vaccination strategies are therefore urgently sought to aid the control of PRRS. To help address this global challenge, the PRRS Immunology Group was formed at the Institute in September 2014.
The PRRS Immunology Group aims to improve our understanding of the interactions of PRRSV with the porcine immune system and to exploit this to develop next generation vaccines or novel intervention strategies. The group aims to address this through the following objectives:
- Investigate the interaction of PRRSV with its target myeloid cell populations and to elucidate the innate immune response pathways that are modulated leading to immune evasion and/or pathology.
- Better define the contribution of T cell and neutralising antibody responses in the immunological control of PRRSV infection and immunity to re-infection.
- To develop novel vaccine strategies using rationally attenuated PRRSV to produce safer live vaccines and approaches based on the identification of conserved antigens associated with ‘protective’ immune responses.
Investigation of the interaction of porcine reproductive and respiratory syndrome viruses with dendritic cells: implications for pathogenesis and immunity (2015-19)
PRRSV is a myelotropic virus infecting cells of the mononuclear phagocyte system. Whilst the alveolar macrophage is often considered the primary target cell, PRRSV replicates and persists in lymphoid tissues. Dendritic cells (DCs) are myeloid cells that play a central role in immunoregulation and induction of adaptive immune responses. DCs may be classified into four subsets each with functional specialisation. There is limited information available on the susceptibility and interactions of PRRSV with porcine DC subsets, this project will address this gap and will test the underlying hypothesis that increased PRRSV virulence is associated with an enhanced capacity to infect and dysregulate DC subset function.
This project is a collaborative PhD Studentship project between The Pirbright Institute and the School of Veterinary Medicine at the University of Surrey, and involves collaboration with the Animal and Plant Health Agency, UK.
PRRSV is responsible for the most economically important infectious disease affecting the global pig industry. PRRS control is hampered by the rapid evolution of the virus and shortcomings with existing vaccines. By dissecting the pathological and protective immune responses evoked by PRRSV, we will be able to design safer and more effective vaccines. We will work with global animal health businesses to develop improved vaccines that will contribute towards enhancing the efficiency, performance and sustainability of the pig industry both in the UK and overseas.