Monovalent, bivalent and biparatopic nanobodies targeting S1 protein of porcine epidemic diarrhea virus efficiently neutralized the virus infectivity

Abstract

Abstract Background Porcine epidemic diarrhea virus (PEDV) is a highly contagious coronavirus that causes severe diarrhea and death in neonatal piglets, which has brought huge economic losses to the pork industry worldwide since its first discovery in the early 1970s in Europe. Passive immunization with neutralizing antibodies against PEDV is an effective prevention measure. To date, there are no effective therapeutic drugs to treat the PEDV infection. Results We conducted a screening of specific nanobodies against the S1 protein from a phage display library obtained from immunized alpacas. Through competitive binding to antigenic epitopes, we selected instead of chose nanobodies with high affinity and constructed a multivalent tandem. These nanobodies were shown to inhibit PEDV infectivity by the neutralization assay. The antiviral capacity of nanobody was found to display a dose-dependent pattern, as demonstrated by IFA, TCID50, and qRT-PCR analyses. Notably, biparatopic nanobody SF-B exhibited superior antiviral activity. Nanobodies exhibited low cytotoxicity and high stability even under harsh temperature and pH conditions, demonstrating their potential practical applicability to animals. Conclusions Nanobodies exhibit remarkable biological properties and antiviral effects, rendering them a promising candidate for the development of anti-PEDV drugs.