PPIB and infection: As shown in Figure 1J, the GFP-positive area of cells infected with the recombinant viruses at 48 h post infection (h.p.i.)was significantly larger for viruses bearing the B.1 RBD [rOmicron S/B.1_RBD-GFP (virus IV) and rOmicron S/B.1 S_NTD+RBD-GFP (virus V)] than for rOmicron-GFP (virus II).