Cellular entry of the porcine epidemic diarrhea virus

Abstract

Porcine epidemic diarrhea virus (PEDV) is the causative agent of porcine epidemic diarrhea (PED), an enteric disease affecting pigs of all ages.The disease is characterized by acute watery diarrhea, dehydration and vomiting, with high mortality in neonatal piglets. Devastating outbreaks of PED in East Asia (since 2010) and in North America (since 2013) have revitalized the research into this porcine coronavirus. PEDV primarily replicates in the epithelial cells of the small intestine. Its entry into host cells is mediated by the viral surface spike (S) glycoprotein that enables attachment to the host cell and subsequent fusion of the viral and cellular membrane. This key entry factor is considered the main determinant of viral host and tissue tropism. In addition, the S protein is highly immunogenic and the main target for neutralizing antibodies. The research described in this thesis aimed to investigate the PEDV spike protein in its interactions with the host cells during the initial stage of infection, and to study its antigenicity. In summary, we found that binding of the S protein to cell surface sialic acids facilitates infection by PEDV, which may contribute to its pathogenesis in vivo. Furthermore, we demonstrated that aminopeptidase N – a host cell surface protein earlier reported to be important for infection - is not essential for PEDV cell entry. In addition, we verified that cellular proteases can activate the spike protein in its entry function and mapped the genetic determinants that are involved in proteolytic activation of the spike protein. Moreover, we generated and characterized monoclonal antibodies raised against the N-terminal S1 subunit of the PEDV spike protein and reveal that its cell attachment domains are key targets of neutralizing antibodies. Collectively, our findings provide further insight into the virus pathogenesis and aid the design of antiviral strategies against this pathogenic swine coronavirus.