Abstract
Porcine epidemic diarrhea coronavirus (PEDV) is currently devastating the United States pork industry by causing an 80–100% fatality rate in infected piglets. Coronavirus spike proteins mediate virus entry into cells, a process that requires the spike proteins to be proteolytically activated. It has been a conundrum which proteases activate PEDV entry. Here we systematically investigated the roles of different proteases in PEDV entry using pseudovirus entry, biochemical, and live virus infection assays. We found that the PEDV spike is activated by lysosomal cysteine proteases but not proprotein convertases or cell surface serine proteases. Extracellular trypsin activates PEDV entry when lysosomal cysteine proteases are inhibited. We further pinpointed cathepsin L and cathepsin B as the lysosomal cysteine proteases that activate the PEDV spike. These results advance our understanding of the molecular mechanism for PEDV entry and identify potential antiviral targets for curbing the spread of PEDV.
Highlights
Porcine epidemic diarrhea coronavirus (PEDV) is currently devastating the United States pork industry by causing an 80 –100% fatality rate in infected piglets
These previous studies all used live PEDV virus particles and were unable to differentiate between PEDV entry and other steps in the PEDV infection cycle, such as virus replication or release
To separate PEDV entry from other steps of the PEDV infection cycle, we performed a PEDV pseudovirus entry assay in which PEDV spike-packaged pseudovirus particles can only enter host cells but cannot replicate or be released
Summary
Porcine epidemic diarrhea coronavirus (PEDV) is currently devastating the United States pork industry by causing an 80 –100% fatality rate in infected piglets. Coronavirus spike proteins mediate virus entry into cells, a process that requires the spike proteins to be proteolytically activated. It has been a conundrum which proteases activate PEDV entry. PEDV is unique among coronaviruses in that its propagation in cell culture requires exogenous trypsin, and it is commonly believed that extracellular trypsin-like proteases in pig intestines are essential for cell entry of PEDV (14 –16) These cell culture studies used live PEDV particles for cell entry and did not differentiate PEDV entry from other steps of the PEDV infection cycle, such as virus replication or release. Identification of the PEDV spike-processing proteases provided potential targets for the development of antiviral drugs to block PEDV entry
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
