PDE12 and COVID-19: Enhanced resistance to virus infection was found through inhibition of the PDE12, including encephalomyocarditis virus, human rhinovirus, and respiratory syncytial virus.102 However, with the aggravation of the COVID-19, let-7b-5p showed downregulation in severe COVID-19 cases,48–50 in line with the abnormal type I IFN response in several and critical patients, featured with the absence of both IFN-β and IFN-α production and activity,103 suggesting a role of let-7b-5p in the impaired IFN deficiency and reduced resistance to SARS-CoV-2 via modulating the PDE12.