The influenza virus is a human respiratory virus that continues to ravage the world even in the presence of a vaccine. Multiple viral protein targets have been identified to prevent and mitigate disease. However, the most commonly used vaccines - split inactivated virus vaccines - only have standardized concentrations of the hemagglutinin (HA) surface protein and elicit HA-specific antibodies. These responses are strain-specific with limited ability to cross-react with antigenically drifted viruses. Therefore, these current vaccines do not provide protection toward potentially pandemic influenza viruses from the avian, swine, or other animal host reservoirs. The neuraminidase (NA) surface protein is not quantified or standardized even though antibodies that target the NA protein are meaningful correlates of protection in humans and mitigate disease in animal models. New NA vaccine immunogens are being investigated to increase the vaccine’s protective breadth and longevity. An N1 NA subtype vaccine immunogen was designed with the computationally optimized broadly reactive antigen (COBRA) methodology using wild-type NA sequences originating from swine, avian, and human isolated HXN1 viruses: N1-I COBRA NA. In the mouse model, the wild-type N1 antigens elicited antigenically distinct patterns based upon the genetic lineage (human, avian, or swine). The human and avian lineage did not cross-react between each other. However, the N1-I COBRA NA elicited functional antibodies to all N1 lineages. Further, this functional antibody profile corresponded with the protection from viral challenge in the ferret model. The N1-I COBRA NA protected as well as the homologous control proteins an H1N1 and an H5N1 challenge (two avian lineage viruses), whereas the human lineage N1 immunogen offered significantly less protection. Lastly, in a contact transmission model, modeling a family unit, vaccination with any immunogen did not inhibit the ability of the vaccinated ferret from transmitting to a naïve ferret, or from a naïve ferret from transmitting to a vaccinated ferret. Overall, this dissertation provides an in-depth analysis of the antigenic and protective profiles of wild type and the N1-I COBRA NA immunogen. The inclusion of the N1-I COBRA NA or, at a minimum, wild type NA protein into current vaccine compositions will provide increased benefit.
