Sequence analysis of the spike gene of Porcine epidemic diarrhea virus isolated from South China during 2011–2015

Zhao, Xiaoya; Li, Zhili; Zeng, Xiduo; Zhang, Guanqun; Niu, Jianqiang; Sun, Baoli; Ma, Jingyun

Porcine epidemic diarrhea virus (PEDV) is a major cause of aqueous diarrhea, vomiting, and severe dehydration in pigs. It is transmitted via direct or indirect fecal-oral routes [10, 14] . As other Coronaviridae members, PEDV is an enveloped, positive-sense, single-stranded RNA virus with a small 28 kb genome. The genomic RNA has a 5′-cap and a 3′-polyadenylated tail and contains at least seven open reading frames that encode four structural proteins: spike (S), envelope (E), membrane (M), and nucleocapsid (N) [9] . Like other coronaviruses, the S protein is a type 1 transmembrane envelope glycoprotein comprising 1,383 amino acids and contains 29 predicted glycosylation sites. The S1 and S2 domains of this protein have essential roles in cellular receptor interactions that mediate viral entry and induce neutralizing antibodies in the natural host [13] . The PEDV S protein consists of three domains: a large extracellular domain, a transmembrane region, and a short cytoplasmic carboxyl terminus. There is a region of the S protein that contains the epitope(s), which is capable of inducing PEDV-neutralizing antibodies [1] . Research indicates that phage-displayed peptides, which were panned against 2C10, have antigenic similarities with the PEDV antigen epitope motif ( 1368 GPRLQPY 1374 ) and can show neutralizing activity against PEDV [6] , the CO-26K equivalent (COE) domain (aa positions 99-638), and the epitopes SS2 (aa positions 748-755) and SS6 (aa positions 764-771), which can also induce neutralizing antibodies against PEDV [4, 25] . Recently, the S gene was implicated as an important determinant of the biological properties of PEDV. These properties include genetic relationships between PEDV isolates, the epidemiological status of PEDV in the field, and associations between genetic mutations and virus function [16] .