The pig as a model to study immunity to respiratory diseases

18 January 2023

This IVVN webinar covered the use of pigs as large animal models for studying immune responses to respiratory diseases. It was presented by Professor Elma Tchilian from The Pirbright Institute, and it was chaired by IVVN Network Management Board member Professor Brian Perry.



Animal models are essential for understanding mucosal respiratory immunity and development of vaccines and therapeutics for respiratory diseases. Mice, guinea pigs and ferrets are widely used for influenza-virus research, with the ferret considered the "gold standard," but none of these models accurately reflect the immune response in large animals or humans. The pig is an important natural host for the same subtypes as human seasonal influenza strains and a source of new human pandemic viruses. The pig is genetically, immunologically, physiologically, and anatomically more similar to humans than small animals, as well as having a longer lifespan.

We have developed sophisticated tools to study T cell immune responses in pigs and for the first time have identified porcine tissue resident memory cells (TRM), which are crucial for local protective immunity. Because TRM are only effectively induced after local administration of vaccine or natural infection, we evaluated by scintigraphy the deposition of different droplet size aerosols in the respiratory tract in pigs in order to determine how best to deliver vaccines to the respiratory tract. We also examined antigen specific CD8 TRM in the context of influenza infection and immunisation in inbred Babraham pigs, using tetramers carrying three different influenza nucleoprotein epitopes. We demonstrated that responding T cells are present in the airways until at least 63 days post infection, have a stable highly differentiated phenotype, do not proliferate rapidly, and share gene signatures of human TRM.

We have demonstrated that the broadly protective vaccine candidate, S-FLU, has different efficacy in ferrets and pigs, suggesting that testing in small animals only, may not accurately identify vaccine efficacy in natural hosts. We have also established a pre-exposure influenza pig challenge model, which closely mimics the situation in humans and pigs, who are commonly exposed to different influenza viruses. We showed that adenoviral vectored vaccine expressing conserved influenza virus nucleoprotein, matrix protein 1 and neuraminidase induces immune response and protects against H3N2 challenge in the face of H1N1pdm09 pre-exposure.

demonstrated the utility of the pig influenza model in testing the protective efficacy of human therapeutic antibodies and generated the first porcine influenza specific monoclonal antibodies. The porcine mAbs recognised the same immunodominant haemagglutinin epitopes targeted by humans. Most notably one of these sites was not recognised by ferret sera routinely used to monitor virus evolution and inform decisions about annual influenza vaccines.

We have recently developed a porcine respiratory coronavirus (PRCV) model which exhibits similar pathology to human SARS-CoV-2 and have established different PRCV strains which induce a spectrum of disease outcomes. These two large animal natural host infectious models will provide important insights into immunity against respiratory infections for improvement of animal and human health.

Professor Elma Tchilian

Professor Elma Tchilian

Elma obtained her PhD at the Imperial Cancer Research Fund, London, before working as a postdoctoral fellow in Birmingham, Senior Research Scientist at the Edward Jenner Institute and Principal Investigator in Oxford. Elma identified the leucocyte common antigen (CD45) as a cause of severe combined immunodeficiency in man. She demonstrated the importance of local immunity in vaccine-induced protection against tuberculosis and influenza.

Elma joined the Pirbright Institute in 2014 and is now Head of Mucosal Immunology. She has established a powerful pig influenza model to study immune responses to and transmission of influenza viruses and to test efficacy of vaccines and monoclonal antibodies (mAbs). Elma has developed many tools for studying porcine immune responses including peptide MHC tetramers, cell transfers in inbred Babraham pigs, porcine influenza specific monoclonal antibodies and has characterised the important tissue resident memory cells in the respiratory tract. These studies have shown that pigs make very similar antibody responses to humans against influenza and that protective immunity in pigs differs from that found in small animal models. More recently Elma’s group developed a porcine respiratory coronavirus model to study acute respiratory coronavirus disease. These data demonstrate the utility of the pig as a biomedical model for human disease.