DPP4 and COVID-19: In addition, polymorphisms in genes including ACE-2, TMPRSS2, vitamin D receptor, vitamin D binding protein, CD147, 78 kDa glucose-regulated protein, dipeptidyl peptidase-4 (DPP4), neuropilin-1, heme oxygenase, apolipoprotein L1, vitamin K epoxide reductase complex 1 (VKORC1) have been associated with the modulation of asymptomatic, symptomatic and severe forms of COVID-19 [8].