"Influenza virus continues to represent a major global health problem and the recent pandemic caused by a H1N1 strain of influenza A (swine flu) is a good example of its potential global threat to health. Vaccination again influenza confers in most of the cases protection against the disease, mainly due to a robust humoral response. However, yearly vaccinations are required in order to protect against new circulating variants of the virus. Another important limitation of the current influenza vaccines is the development of a suboptimal immunogenicity in the elderly, in patients with serious chronic diseases, in the immunocompromised, and in young children, which correlates with higher morbidity and mortality in these risk groups. In addition, the presence of adjuvants in the formulation of most of the vaccines has been questioned due to potential health risks associated with their toxicity.The general aim of this project is to understand the immunological events that lead to the establishment of a protective response against influenza virus in the lymph node after vaccination. To pursue that aim we will evaluate the capture and transport of the viral particles from the injection site to the B cell follicle where the antibody response is initiated. We will use a multidisciplinary approach to evaluate the main questions of the project including state-of-the-art imaging techniques, such as intravital-2photon microscopy to study cell interaction and antigen transport in vivo, molecular techniques such as microarray analysis to study specific transcriptome profiling after vaccination and microbiology techniques to develop new fluorescent variants of the virus. Understanding the mechanism of action of the influenza vaccine will enable the manipulation of the immune response to induce a stronger immunogenic, and a safer protective response through vaccination."