2.5. Purification of ORF8-CRM and ORF8-PEG
ORF8-CRM and ORF8-PEG were purified by a Superdex 200 column (1.6 cm × 60 cm, GE Healthcare, USA), based on size exclusion chromatography (SEC). The column was equilibrated and eluted by PBS buffer (pH 7.4) at a flow rate of 2.0 mL/min. The effluent was detected at 280 nm. The fractions corresponding to ORF8-CRM and ORF8-PEG were pooled and concentrated by Amicon (Millipore) with 10 kDa cutoff membrane at 4°C.