To determine the optimal storage conditions and stability of the NoV capsid VLPs, VLPs were treated under different conditions, and the samples were analyzed by SDS-PAGE to test their protein integrity (Fig. 2a) and by EM to examine their morphology (Fig. 2b) . VLPs were stable for at least 12 months at 4°C in PBS, pH 7.4 ( Fig. 2a and b, panel 1) , and at room temperature (23°C) up to 7 days ( Fig. 2a and b,  panel 3) . The VLPs withstood the sterile filtration conditions when 0.22-lm filters (Durapore, Millipore, Ireland) were used. Next, we intentionally disrupted the VLP morphology by heat treatment at 60°C for 1 h (Fig. 2b, panel 4) [1] without degrading the capsid protein (Fig. 2a, lane 4) .