DPP4 and Middle East respiratory syndrome: In line with observations made in human MERS cases, common marmosets that express DPP4 in both type I and II pneumocytes have been reported to produce more infectious virus upon experimental MERS-CoV infection, compared to rhesus and cynomolgus macaques that merely expressed DPP4 in type II pneumocytes [58,109,110,111,112].