Cathepsin L and transmembrane serine protease 11E mediate trypsin-independent entry of porcine deltacoronavirus into Huh7 cells

PDCoV can be isolated from human plasma samples and infect various human-derived cells, raising significant concerns regarding its potential for cross-species transmission. Coronavirus invasion involves receptor binding and spike (S) protein cleavage by proteases. While human aminopeptidase N (APN) has been confirmed as a receptor that mediates PDCoV infection, the specific proteases involved in infections of human-derived cells remain incompletely understood. Here, we investigated the mechanisms by which PDCoV enters human-derived cells and demonstrated that PDCoV infection in these cells is independent of exogenous trypsin. Furthermore, we identified two critical proteases, CTSL and TMPRSS11E, which facilitate PDCoV entry into Huh7 cells via endosomal and plasma membrane fusion pathways, respectively. Additionally, we discovered that furin promotes the maturation and release of virions. This study reveals the infection mechanisms of PDCoV in human-derived cells, highlighting the roles of CTSL, TMPRSS11E, and furin in viral entry and release.