Enhancing epitope of PEDV spike protein

Techit Thavorasak; Monrat Chulanetra; Kittirat Glab-Ampai; Kodchakorn Mahasongkram; Nawannaporn Sae-Lim; Karsidete Teeranitayatarn; Thaweesak Songserm; Rungrueang Yodsheewan; Dachrit Nilubol; Wanpen Chaicumpa; Nitat Sookrung

doi:10.3389/fmicb.2022.933249

Enhancing epitope of PEDV spike protein

Front Microbiol. 2022 Jul 22:13:933249. doi: 10.3389/fmicb.2022.933249. eCollection 2022.

Affiliations

¹ Graduate Program in Immunology, Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
² Center of Research Excellence in Therapeutic Proteins and Antibody Engineering, Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
³ MORENA Solution Company, Bangkok, Thailand.
⁴ Department of Veterinary Pathology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand.
⁵ Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.
⁶ Swine Viral Evolution and Vaccine Development Research Unit, Chulalongkorn University, Bangkok, Thailand.
⁷ Biomedical Research Incubation Unit, Department of Research, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.

Abstract

Porcine epidemic diarrhea virus (PEDV) is the causative agent of a highly contagious enteric disease of pigs characterized by diarrhea, vomiting, and severe dehydration. PEDV infects pigs of all ages, but neonatal pigs during the first week of life are highly susceptible; the mortality rates among newborn piglets may reach 80-100%. Thus, PEDV is regarded as one of the most devastating pig viruses that cause huge economic damage to pig industries worldwide. Vaccination of sows and gilts at the pre-fertilization or pre-farrowing stage is a good strategy for the protection of suckling piglets against PEDV through the acquisition of the lactating immunity. However, vaccination of the mother pigs for inducing a high level of virus-neutralizing antibodies is complicated with unstandardized immunization protocol and unreliable outcomes. Besides, the vaccine may also induce enhancing antibodies that promote virus entry and replication, so-called antibody-dependent enhancement (ADE), which aggravates the disease upon new virus exposure. Recognition of the virus epitope that induces the production of the enhancing antibodies is an existential necessity for safe and effective PEDV vaccine design. In this study, the enhancing epitope of the PEDV spike (S) protein was revealed for the first time, by using phage display technology and mouse monoclonal antibody (mAbG3) that bound to the PEDV S1 subunit of the S protein and enhanced PEDV entry into permissive Vero cells that lack Fc receptor. The phages displaying mAbG3-bound peptides derived from the phage library by panning with the mAbG3 matched with several regions in the S1-0 sub-domain of the PEDV S1 subunit, indicating that the epitope is discontinuous (conformational). The mAbG3-bound phage sequence also matched with a linear sequence of the S1-BCD sub-domains. Immunological assays verified the phage mimotope results. Although the molecular mechanism of ADE caused by the mAbG3 via binding to the newly identified S1 enhancing epitope awaits investigation, the data obtained from this study are helpful and useful in designing a safe and effective PEDV protein subunit/DNA vaccine devoid of the enhancing epitope.

Keywords: antibody-dependent enhancement; enhancing epitope; phage display technology; phage mimotope; phage panning; porcine epidemic diarrhea; porcine epidemic diarrhea virus; spike protein.