Structure of a prototype for a universal flu vaccine. The nanoparticle is a hybrid of a protein scaffold and eight influenza hemagglutinin proteins on the surface. The hemagglutinin was specifically engineered to display antibody binding sites common to all human influenza subtypes. The particle designed by Jeffrey Boyington (NIAID Vaccine Research Center) has been shown to be an effective immunogen in mice and ferrets (VRC). 3D structure of the particle was determined by cryo-electron microscopy by John Gallagher and Audray Harris (NIAID Laboratory of Infectious Diseases).