Figure 3.

Mosaic HA vaccination approach. The mHA vaccine contains a head domain in which the variable immunodominant antigenic sites are replaced with antigenic sites from exotic avian HA subtypes while conserved regions of both head and stalk domain are retained (H1 HA in this example). Priming with mHA strongly induced an Ab response to the conserved antigenic sites, but only a weak Ab response to the conserved retained regions. However, boosting with the mHA head domain with antigenic sites from other exotic avian HA subtypes enhances Ab responses to both the head and stalk domains. The structure of HA was constructed using Swiss-Model (https://www.swissmodel.expasy.org/, accessed on 5 April 2021). The representative virus is influenza A virus (A/California/07/2009(H1N1)) and the sequence was obtained from GenBank (ACQ55359.1).