Swine as a model for influenza A virus infection and immunity

Influenza A viruses (IAVs) infect a variety of hosts, including humans, swine, and various avian species. The annual influenza disease burden in the human population remains significant even with current vaccine usage, and much about the pathogenesis and transmission of influenza viruses in humans remains unclear. Thus, animal models are a fundamental tool for influenza research to understand mechanisms of virulence and to develop more efficacious vaccines and forms of prevention or treatment. The choice of experimental model to be used should be based on the species characteristics and similarities to humans, and how the limitations of each host interfere the least with the parameters studied. Influenza virus infection in swine has many similarities with that in humans: the same subtypes are endemic in both species, there has been repeated exchange of viruses between these hosts, the clinical manifestation and pathogenesis are similar, and there is a similar distribution of IAV receptors in the respiratory tract. Considering these common characteristics, and the similarities between humans and swine in terms of genetics, anatomy, and physiology, pigs represent an excellent yet often overlooked model for biomedical research and the study of IAV infection.