PPBP and COVID-19: Moreover, numerous studies have previously revealed that changes in TGFB1-regulated signalling have pivotal influences on viral infections, such as Epstein–Barr virus (EBV) (Filatova et al., 2019), respiratory syncytial virus (RSV) (Xu et al., 2020), and COVID-19 (Vaz de Paula et al., 2021), thereby suggesting that the upstream regulatory molecule miR-663a of TGB1 may directly affect the infection process of these viruses.