2.1 Expression and purification of recombinant
proteins
Triple M2e peptides derived from human (hM2e), swine (sM2e) and avian
(aM2e) IAV were combined with the C-terminus of Cap protein in different
arrangements using Gly-Gly-Gly-Gly linker. (Fig. 1a-1c). These sequences
were inserted into the pET28a vector by BamHI and HindIII digestion
enzymes, and transformed into E. coli BL21 (DE3). Then these
transformed cells were induced expression at 20°C for 15 h by
isopropyl-β-d-thiogalactoside (IPTG) (0.2 mM). These recombinant
proteins were purified by using Ni-NTA His·Bind Resin and identified by
SDS-PAGE and Western blot. The concentrations of these purified proteins
were determined with a BCA protein assay kit (Solarbio, Beijing, China).
The endotoxin concentrations were measured by ToxinSensor Single Tests
Kit (GenScript, Piscataway, NJ, USA). The VLPs pattern was drawn from
the PDB accession number 3R0R.