In addition to ACE2 and TMPRSS2, other host proteins such as neuropilin 1 (NRP1) and dipeptidyl peptidase 4 (DPP4) also serve as potential targets of SARS-CoV-2 in relation to the pathogenesis of AD (Ding et al., 2020; Wicik et al., 2020; Lim et al., 2021). The gene discussed is DPP4; the disease is Alzheimer disease.