Porcine deltacoronavirus (PDCoV) is an emerging enteric coronavirus with the potential for interspecies transmission. Trypsin has been shown to play a positive role in the isolation and multiplication of PDCoV in vitro, however, the functions of trypsin during PDCoV replication cycle remain controversial. In this study, we revisited the roles of trypsin for PDCoV infection by utilizing two kinds of PDCoV, PDCoV