Adenovirus vector-mediated single chain variable fragments target the nucleocapsid protein of porcine epidemic diarrhea virus and protect against viral infection in piglets

Intranasal delivery of a recombinant adenovirus vaccine encoding the PEDV COE elicits potent mucosal and systemic antibody responses in mice

Porcine epidemic diarrhea virus (PEDV) is an enteropathogenic coronavirus that causes substantial economic loss to the global pig industry. The emergence of PEDV variants has increased the need for new vaccines, as commercial vaccines confer inferior protection against currently circulating strains. It is well established that the induction of mucosal immunity is crucial for PEDV vaccines to provide better protection against PEDV infection. In this study, we constructed a recombinant adenovirus expressing the core neutralization epitope (COE) of G2b PEDV based on human adenovirus serotype 5 (Ad5). We evaluated the effects of different administration routes and doses of vaccine immunogenicity in Balb/c mice. Both intramuscular (IM) and intranasal (IN) administration elicited significant humoral responses, including COE-specific IgG in serum and mucosal secretions, along with serum-neutralizing antibodies. Moreover, IN delivery was more potent than IM in stimulating IgA in serum and mucosal samples and in dampening the immune response to the Ad5 vector. The immune response was stronger after high versus low dose IM injection, whereas no significant difference was observed between high and low IN doses. In summary, our findings provide important insights for developing novel PEDV vaccines.IMPORTANCEPorcine epidemic diarrhea (PED) is a highly contagious disease that has severe economic implications for the pork industry. Developing an effective vaccine against PEDV remains a necessity. Here, we generated a recombinant adenovirus vaccine based on Ad5 to express the COE protein of PEDV (rAd5-PEDV-COE) and systematically evaluated the immunogenicity of the adenovirus-vectored vaccine using different administration routes (intramuscular and intranasal) and doses in a mouse model. Our results show that rAd5-PEDV-COE induced potent systemic humoral response regardless of the dose or immunization route. Notably, intranasal delivery was superior to induce peripheral and mucosal IgA antibodies compared with intramuscular injection. Our data provide valuable insights into designing novel PEDV vaccines.

Pemetrexed alleviates piglet diarrhea by blocking the interaction between porcine epidemic diarrhea virus nucleocapsid protein and Ezrin

Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus that causes high mortality in piglets, thus posing a serious threat to the world pig industry. Porcine epidemic diarrhea (PED) is related to the imbalance of sodium absorption by small intestinal epithelial cells; however, the etiology of sodium imbalanced diarrhea caused by PEDV remains unclear. Herein, we first proved that PEDV can cause a significant decrease in Na+/H+ exchanger 3 (NHE3) expression on the cell membrane, in a viral dose-dependent manner. Further study showed that the PEDV nucleocapsid (N) protein participates in the regulation of NHE3 activity through interacting with Ezrin. Flame atomic absorption spectroscopy results indicated a serious imbalance in Na+ concentration inside and outside cells following overexpression of PEDV N. Meanwhile, molecular docking technology identified that the small molecule drug Pemetrexed acts on the PEDV N-Ezrin interaction region. It was confirmed that Pemetrexed can alleviate the imbalanced Na+ concentration in IPEC-J2 cells and the diarrhea symptoms of Rongchang pigs caused by PEDV infection. Overall, our data suggest that the interaction between PEDV N and Ezrin reduces the level of phosphorylated Ezrin, resulting in a decrease in the amount of NHE3 protein on the cell membrane. This leads to an imbalance of intracellular and extracellular Na+, which causes diarrhea symptoms in piglets. Pemetrexed is effective in relieving diarrhea caused by PEDV. Our results provide a reference to screen for anti-PEDV targets and to develop drugs to prevent PED.IMPORTANCEPorcine epidemic diarrhea (PED) has caused significant economic losses to the pig industry since its initial outbreak, and the pathogenic mechanism of porcine epidemic diarrhea virus (PEDV) is still under investigation. Herein, we found that the PEDV nucleocapsid protein interacts with Ezrin to regulate Na+/H+ exchanger 3 activity. In addition, we screened out Pemetrexed, a small molecule drug, which can effectively alleviate pig diarrhea caused by PEDV. These results provide support for further exploration of the pathogenesis of PEDV and the development of drugs to prevent PED.