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Simple Summary: Porcine epidemic diarrhea (PED) is a porcine enteric viral disease that is characterized by watery diarrhea, vomiting, and dehydration. PED is highly contagious and causes significant mortality, especially in suckling piglets. The G2b variant PEDV, which started to become prevalent in China in 2013, has higher pathogenicity and transmissibility than existing viruses and causes economic losses in many countries, including South Korea. The present study shows that the G2b variant PEDV has a relatively high resistance to interferons and neutralizing antibodies. The present study has important implications for understanding the occurrence of variant PEDV and its pathogenesis. Variant porcine epidemic diarrhea virus (PEDV), belonging to the genogroup G2b, has higher pathogenicity and mortality than classical PEDV, belonging to the genogroup G1a. To understand the pathogenesis of the G2b PEDV, we examined the resistance of the G2b PEDV to interferon (IFN) and neutralizing antibodies, which are important for controlling PEDV infection. We found that the G2b PEDV showed higher resistance to IFN than G1a PEDV. The G1a PEDV could replicate in IFN-deficient Vero cells, but not in IFN-releasing porcine alveolar macrophages, whereas the G2b PEDV showed similar infectivity in both types of cells. We also found that G2b PEDV was not effectively blocked by neutralizing antibodies, unlike G1a PEDV, suggesting differences in the antigenicity of the two strains. These results provide an understanding of the occurrence of variant PEDV and its pathogenesis. [ABSTRACT FROM AUTHOR]

Porcine epidemic diarrhea virus (PEDV) is a highly contagious enteric pathogen of swine. PEDV has been a major problem in the pig industry since its first identification in 1992. The aim of this study was to investigate the diversity, molecular characteristics, and phylogenetic relationships of PEDVs in field samples from Korea. Six PEDVs were identified from the field samples, and the full spike (S) glycoprotein gene sequences were analyzed. A phylogenetic analysis of the S gene sequences from the six isolates revealed that they were clustered into the G2b subgroup with genetic distance. The genetic identity of the nucleotide sequences and deduced amino acid sequences of the S genes of those isolates was 97.9-100% and 97.4-100%, respectively. A BLAST search for new PEDVs revealed an identity greater than 99.5% compared to the highest similarity of two different Korean strains. The CO-26K equivalent (COE) epitope had a 521H→Y/Q amino acid substitution compared to the subgroup G2b reference strain (KNU-1305). The CNU-22S11 had 28 amino acid substitutions compared to the KNU-1305 strain, which included two newly identified amino acid substitutions: 562S→F and 763P→L in the COE and SS6 epitopes, respectively. Furthermore, the addition and loss of N-linked glycosylation were observed in the CNU-22S11. The results suggest that various strains of PEDV are prevalent and undergoing evolution at swine farms in South Korea and can affect receptor specificity, virus pathogenicity, and host immune system evasion. Overall, this study provides an increased understanding of the prevalence and control of PEDV in South Korea.

The results of our DNA analysis showed that there was 100% homology of the VP28 and VP19 genes of white spot syndrome virus (WSSV) among the samples collected from different shrimp farms in Korea. Comparing with an earlier isolated Korean strain, Korea01, the genes nucleotide sequences had only a single base difference which was observed in both VP19 and VP28. This resulted in a single amino acid substitution at position 40 of the latter. This implies that a single genetic strain of WSSV has been circulating in Korea and that its mutation rate is very low. In comparison with known sequences of VP19 and VP28 genes of WSSV isolates from other countries, the Korean strains had more than 99% sequence homology with those in gene and protein. Based on our sequence analysis of VP19 and VP28 of WSSV from various shrimp farms in Korea, the WSSV strains circulating in the region were genetically identical and similar to the strain identified two years ago. In addition, the Korean strain had close genetic identity with strains circulating in other Asian countries as well as other continents.