Cell entry mechanisms of porcine enteric coronaviruses

Porcine enteric coronaviruses, including transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), swine acute diarrhea syndrome coronavirus (SADS-CoV), and porcine deltacoronavirus (PDCoV), cause severe watery diarrhea, vomiting, dehydration, and high mortality in piglets, leading to enormous economic losses in the swine industry worldwide. They have the capability to infect a variety of cell lines from pigs, humans, and other animals, with high risks of interspecies transmission and potential threats to public health. These viruses employ their spike glycoproteins to engage with various receptors, coreceptors, cofactors, and other host factors that further mediate membrane fusion to accomplish the entry process. This review summarizes the recent findings regarding the pathways, receptors, coreceptors, cofactors, and other host factors utilized by TGEV, PEDV, SADS-CoV, and PDCoV for cellular entry. Several important targets for antiviral therapeutics and some key aspects of the entry process for these viruses that await discovery are highlighted. A comprehensive understanding of the entry mechanisms of porcine enteric coronaviruses will provide new insight into the development of novel antiviral therapeutic strategies.