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Abstract
Influenza virus has been a significant global health concern for over a hundred years. Seasonal influenza epidemics are a major cause of morbidity and mortality worldwide each year. Currently, the best countermeasure to combat influenza infections is vaccination. However, long term protection to influenza is one of the biggest challenges with controlling influenza infections and spread. This is due to the high rate of mutation and evolution leading to great influenza virus genetic diversity creating a difficult challenge for the immune system to recognize the constantly evolving influenza strains. Current influenza vaccines depend on eliciting antibodies targeting HA while NA has been largely ignored in vaccine formulation. Computationally optimized broadly reactive antigens (COBRAs) were developed as an approach to broaden the immune response influenza vaccination. Several HA and NA COBRAs were designed and tested in naïve and pre-immune animal models showing broader immune response across influenza strains compared to wild-type HA and NA proteins. To further characterize these broadly reactive antigens, it is important to study the antibody response elicited with COBRA vaccination. Using HA and NA COBRAs, we generated several monoclonal antibodies targeting these antigens and assessed the functional and structural characteristics of COBRA specific mAbs. Several structures of different wildtype HA and NA proteins identifying the major antibody epitopes specially for HA have been published. However, little information is known on COBRA epitopes. Through structural analysis of COBRAs, we identified important HA and NA epitopes that are required to elicit broadly neutralizing antibodies and evaluated the structural mechanism of antibody recognition. We also aimed to optimize the immune response to COBRAs by 1) developing a novel vaccination strategy to influence the way the immune system responds to theses antigens eliciting bNAbs targeting conserved epitopes on HA. 2) assessing the effect of different adjuvants on COBRA vaccination and choosing the optimal adjuvant. The work described here provides valuable information on the structure and function of COBRAs and COBRA specific mAbs which will further advance the development of next generation broadly reactive immunogens.