2.2 Proteins, Reagents, Cell Lines and Viruses
HA, Omicron BA.5 S, and Omicron BA.5 S-RBD proteins were purchased from SinoBiological. MF59 adjuvant was prepared according to our previously published paper.18 Horseradish Peroxidase (HRP)-labeled goat anti-mouse IgG and 3,3’,5,5’-Tetramethylbenzidine (TMB) were purchased from Beyotime (Shanghai, China). HRP-labeled goat anti-mouse IgG1 and IgG2a were purchased from Abcam (Shanghai, China). VeroE6-TMPRSS2 cells were purchased from the American Type Culture Collection (ATCC). Dulbecco’s Modified Eagle’s Medium (DMEM) was purchased from Meilun (Dalian, China). Fetal bovine serum (FBS) was purchased from Gibco (New York, USA). Experiments involving the SARS-CoV-2 Omicron BA.5.2 strain and H1N1 A/California/07/2009 strain were conducted by following the approved standard operating procedures of the biosafety level 3 facility at the University of Hong Kong.