DPP4 and infection: Successively, for testing the efficiency of DPP4 peptides (specifically DPP4270–295 and DPP4318–343), for inhibition of the entry driven by WT and variant S proteins (i.e., D614G, B1.1.7, B1.351, and P1), pseudoviruses carrying either SARS-CoV-2 WT or those variants were used for the infection (Figure 4).