KLK1 and infection: KLK1 cleaved H1, H2, and H3 HA molecules and consequently enhanced viral production [79]; CD163 is the most important and critical molecule in the life cycle of Porcine reproductive and respiratory syndrome virus (PRRSV), which is responsible for mediating virus uncoating and genome release, so by up regating the expression of CD163, it promotes the replication of the viruses in the cells and thus increases the efficacy of infection [80].