Complete genome sequences of novel S-deletion variants of porcine epidemic diarrhea virus identified from a recurrent outbreak on Jeju Island, South Korea

Porcine epidemic diarrhea virus (PEDV) is a deadly epizootic swine coronavirus that is of importance to the world pork industry. Since the re-emergence of the virulent genotype 2b (G2b) in 2014, Jeju Island in South Korea has faced periodic outbreaks, leading to the occurrence of endemics in provincial herds. In this study, we examined the complete genome sequences and molecular characteristics of novel G2b PEDV variants with a two-amino-acid deletion in the neutralizing epitope of the spike (S) gene, which were concurrently identified on a re-infected farm and its neighboring farm on Jeju Island. Whole-genome sequencing of the Jeju S-DEL isolates KNU-1829 and KNU-1830 revealed the presence of a continuous 9-nucleotide deletion within the nonstructural protein coding region. Their genomes were 28,023 nucleotides in length, 15 nucleotides shorter than those of the classical G2b PEDV strains. The two S-DEL isolates had 96.4–99.2% and 98.3–99.7% identity at the S-gene and full-genome level, respectively, to other global G2b PEDV strains. Genetic and antigenic analyses indicated that the S-DEL isolates are most closely related to the primary strain identified from the initial exposure at the same farm, but the virus appears to undergo continuous evolution, possibly leading to antigenic drift under recurrent or endemic pressure. This study provides important information about the antigenic diversity of PEDV circulating in the endemic areas, which arises from continuous non-lethal mutations to ensure viral fitness in the host environment.