Porcine epidemic diarrhea virus (PEDV) is a highly contagious enteric pathogen of swine. In the present study, we analyzed the spike genes and ORF3 genes of seven PEDV strains detected in Philippine pigs in June 2014. There are four major epitope regions in the spike glycoprotein: a CO-26K equivalent (COE) domain, SS2 and SS6 epitopes, and an epitope region recognized by the 2C10 monoclonal antibody. Analysis of Philippine strains revealed amino acid substitutions in the SS6 epitope region (LQDGQVKI to SQSGQVKI) of the S1 domain. Substitutions were also detected in the 2C10 epitope region (GPRLQPY to GPRFQPY) in the cytoplasmic domain. Phylogenetic analysis of the complete spike gene sequences from the seven strains revealed that they clustered within the G2 group but were distantly related to the North American and INDELs clusters. Interestingly, these strains were close to Vietnamese PEDVs on the ORF3 genetic tree and showed high (97.0-97.6 %) sequence identity to ORF3 genes at the nucleotide level.

Porcine epidemic diarrhea virus (PEDV) causes acute diarrhea and dehydration in sucking piglets and has a high mortality rate. An immunochromatography (IC) assay, known as a lateral flow test, is a simple device intended to detect the presence of target pathogens. Here, we developed an IC assay that detected PEDV antigens with 96.0% (218/227) sensitivity and 98.5% (262/266) specificity when compared with real-time reverse transcriptase (RT)-PCR using FAM-labeled probes based on sequences from nucleocapsid genes. The detection limits of the real-time RT-PCR and IC assays were 1×10(2) and 1×10(3) copies, respectively. The IC assay developed herein did not detect non-specific reactions with other viral or bacterial pathogens, and the assay could be stored at 4°C or room temperature for 15 months without affecting its efficacy. Thus, the IC assay may result in improved PED detection and control on farms, and is a viable alternative to current diagnostic tools for PEDV.

A highly virulent strain of Porcine epidemic diarrhea virus (PEDV) causing severe diarrhea has recently emerged in Vietnam. Genomic sequences from a novel strain, HUA-14PED96, isolated from a Vietnamese piglet with serious diarrhea show relatively high identity with U.S.-like PEDV strains, and have a 72-nt deletion in the open reading frame 1a (ORF1a) gene.

In South Korea in 2013, the G1-based vaccine failed to prevent an outbreak of G2b-type porcine epidemic diarrhea virus (PEDV), which is more pathogenic than the traditional G1-type strain, thereby allowing the virus to spread. In 2017 and 2018, field samples were cultured sequentially on Vero cells to isolate HS (virulent) and SGP-M1 (partially attenuated) strains, respectively, of the G2b type. The HS strain harbors a single amino acid (aa) change and two aa deletions in the N-terminal domain of S1 (55I56G57E→55K56Δ57Δ). The SGP-M1 strain harbors a seven aa deletion in the C-terminal domain of S2 (1380~1386ΔFEKVHVQ). By co-infecting various animal cells with these two strains (HS and SGP-M1), we succeeded in cloning strain HSGP, which harbors the mutations present in the two original viruses. The CPE pattern of the HSGP strain was different from that of the HS and SGP-M1 strains, with higher viral titers. Studies in piglets showed attenuated pathogenicity of the HSGP strain, with no clinical symptoms or viral shedding, and histopathologic lesions similar to those in negative controls. These findings confirm that deletion of specific sequences from the S gene attenuates the pathogenicity of PEDV. In addition, HSGP strains created by combining two different strains have the potential for use as novel attenuated live vaccine candidates.