Sequence analysis of the partial spike glycoprotein gene of porcine epidemic diarrhea viruses isolated in Korea

Porcine epidemic diarrhea virus (PEDV) causes a devastating enteric disease with acute diarrhea, dehydration and significant mortality in swine, thereby incurring heavy economic losses in Korea. Spike (S) glycoprotein has been suggested as an important determinant for PEDV biological properties. In this study, the nucleotide and deduced amino acid sequences of the partial S glycoprotein genes of Korean PEDV isolates, including epitope region that is capable of inducing PEDV-neutralizing antibodies, were determined. The partial S glycoprotein genes were amplified by RT-PCR, cloned, sequenced, and compared with each other as well as with reference PEDV strains. By phylogenetic analysis, the Korean PEDV isolates were divided into three groups (G1, G2, G3), which had three subgroups (G1-1, G1-2, G1-3). Group1 (G1) Korean PEDV isolates were highly homologous to CV777, Br1/87, JS-2004-2, KPED-9, P-5V, SM98-1, parent DR13, and attenuated DR13, group2 (G2) Korean PEDV isolates were highly homologous to Spk1, and group3 (G3) was Chinju99 at the nucleotide and deduced amino acid sequence levels. In addition, the G1 Korean PEDV isolates didn't had several specific nucleotides and amino acids which were found in the G2 and G3 Korean PEDV isolates, and especially the G1-1 Korean PEDV isolates had specific nucleotides and amino acids which were not found in the G1-2, G1-3, G2, and G3 Korean PEDV isolates. It was suggested that many Korean PEDV isolates are closely related to the G1 including CV777, Br1/87, JS-2004-2, KPED-9, P-5 V, SM98-1, parent DR13, and attenuated DR13 rather than to the G2 and G3 including Spk1 and Chinju99, and notably more prevalent PEDVs isolated in Korea are especially close to the Chinese PEDV strain JS-2004-2 rather than Korean PEDV strains Spk1, Chinju99, KPED-9, SM98-1, parent DR13, and attenuated DR13.