This image shows a single hemagglutinin spike from the influenza A virus (blue and yellow ribbons) bound by one of the anti-viral proteins designed in this work, HB36 (red). Approximately 300 hemagglutinin spikes coat the virus surface, where they help the virus to gain entry to host cells and initiate infection. HB36 and HB80 may block virus replication by inhibiting the function of hemagglutinin. (Image courtesy of the Wilson lab.)