In our previous study of recombinant adenovirus-5 vectored vaccines against MERS-CoV, despite affording similar reductions in viral burden as S1 alone, only S1-CD40L was able to prevent pulmonary perivascular hemorrhage post–MERS-CoV challenge in the transgenic Human Dipeptidyl Peptidase 4 Mouse Model (28). Here, DPP4 is linked to hemorrhage.