DPP4 and infection: To evaluate the potential inhibitory activity of S377-588-Fc protein against MERS-CoV infection, the highly permissive human bronchial epithelial Calu-3 cells that express DPP4 [23] were incubated with MERS-CoV/EMC-2012 at 0.1 multiplicity of infection (MOI) in the presence of serially diluted S377-588-Fc protein.