Figure 1. Cryo-electron microscopy of norovirus-like particle (VLP) and P particle. The VLP (left) is composed of 180 capsid proteins (VP1s) with the P2 subdomain on its outermost surface. The P particle that formed by 24 P domains also has the P2 subdomain on its outermost surface. The P2 subdomain of norovirus is responsible for virus-host interactions and immune responses of the virus and thus both norovirus VLPs and P particles share similar antigenic properties.