Influenza viruses cause infections of the respiratory tract in both humans and pigs. Antigenic drift allows viruses to escape pre-existing immunity present in the human population and cause annual epidemics that results in significant morbidity, economic loss, and an estimated 250,000 deaths per year worldwide. Antigenic shift allows the creation of new influenza viruses with novel surface proteins that are antigenically unrelated to surface proteins of viruses that circulated in previous seasons. Currently licensed vaccines aim at the induction of neutralizing antibodies and their efficacy depends on accurate prediction of the influenza strains that will circulate in the next season. Protection provided by current vaccines is limited in time since antigenic drift and shift allow influenza viruses to escape vaccine-induced neutralizing antibodies, and there is a critical need for broad and long-lasting vaccines that provide protection against influenza viruses of different subtypes in all age groups. The development of such universal influenza vaccines is of public health importance and the outlines of a strategic plan have been published recently by the National Institute of Allergy and Infectious Diseases. One of the action items is to develop animal models that recapitulate human immunity to influenza virus infection and vaccination. In this project proposal, we plan to further develop the miniature pig model for the study of host-immune responses to influenza A virus infection and vaccination. We choose to work with miniature pigs because they are natural influenza hosts, easier to handle and to obtain seronegative animals than with conventional pigs and because haplotyped inbred animals are available. In the first part of the project we will focus on the establishment of an influenza A infection and re-infection model with miniature pigs to complement clinical studies previously performed in humans and the conventional pig influenza model. Immune responses induced by the first influenza infection will be monitored and correlated with protection against re-infection with a heterosubtypic influenza virus. In the second part of the project we will focus on the establishment of an influenza A vaccine model with miniature pigs to evaluate universal vaccine approaches and compare them to a conventional influenza vaccine. We will also investigate if the miniature pig influenza model is suitable for the study of vaccine-associated enhancement of disease, as is described for conventional pigs. This project will allow to define correlates of protective immunity against influenza A viruses of different subtypes and is crucial to close knowledge gaps in the current models for universal influenza vaccine studies.