The key to successful virus infection is the entry of the virus into cells, hence, most viruses use host receptor proteins to enter cells by endocytosis followed by exploiting host nutrients for its replication, proliferation, etc. For example, the WSSV envelope protein, VP24, interacts with polymeric immunoglobulin receptor (pIgR) to enable endocytosis of WSSV into cells, through a pIgR-Calmodulin-Clathrin mediated mechanism in M. japonicus (50). The gene discussed is PIGR; the disease is viral infectious disease.