Guehwan Jang

Since the global emergence of highly pathogenic genotype 2b (HP-G2b) porcine epidemic diarrhea virus (PEDV) strains in 2013, these viruses have become endemic in South Korea. During local outbreaks, novel HP-G2b PEDV variants containing a 32-amino acid deletion (DEL) in nonstructural protein 3 (nsp3), designated NSP3-DEL32, were identified in several affected farms with low neonatal mortality. To examine the effect of NSP3-DEL32 on PEDV virulence, a recombinant PEDV, icNSP3-DEL32, was generated harboring the same DEL signature in nsp3 using the HP-G2b icKNU-141112 strain as the backbone. The growth properties of icNSP3-DEL32 were comparable to those of icKNU-141112 in interferon (IFN)-deficient cells. However, in IFN-responsive cells, icNSP3-DEL32 replicated less efficiently but induced higher levels of IFN responses than icKNU-141112. Animal challenge experiments revealed notable differences in pathogenesis between icKNU-141112 and icNSP3-DEL32. Infection with icKNU-141112 resulted in 100% mortality, whereas icNSP3-DEL32 infection caused a lower mortality rate (60%). Remarkably, two piglets inoculated with icNSP3-DEL32 survived and exhibited decreased viral loads as well as normal macroscopic and microscopic intestinal findings, indicating reduced enteropathogenicity of icNSP3-DEL32. These findings indicate that naturally occurring DEL32 in nsp3 partially attenuates PEDV in piglets and support a role for nsp3 as a virulence determinant that suppresses IFN responses.

Win PW, et al. J Vet Sci. 2026 ;27:e89. https://doi.org/10.4142/jvs.26107

Porcine epidemic diarrhea virus (PEDV) is a highly contagious and lethal pig coronavirus, particularly in neonatal piglets. The main route of PEDV transmission is the fecal-oral route via direct contact with infected pigs. As pigs are commonly transported to slaughterhouses in trucks, PEDV can infect farms through contact with contaminated trucks. In South Korea, there is insufficient understanding of pig transportation as a major source of virus transmission. Therefore, this study evaluated the presence of PEDV in transportation and slaughterhouses and investigated possible contamination sources. In total, 401 environmental samples were collected by swabbing surface areas with cotton gauze and classified into 4 categories based on their sampling location: vehicle interior, vehicle exterior, drivers, and slaughterhouses. The swab samples exhibited a relatively high PEDV detection rate of 19.2% (77/401). The detection rate was highest for the slaughterhouse (38.2%, 21/55) and lowest for the vehicle interior (13.0%, 12/92). Genetic and phylogenetic analysis revealed that all sequenced isolates belonged to the highly pathogenic genotype 2b currently circulating in South Korea. The high PEDV detection rates in transport vehicles and slaughterhouses suggest that transportation plays a major role in PEDV introduction into farms. Our findings emphasize the need to enforce biosecurity protocols, including adequate hygiene measures, to mitigate the risks associated with pig transportation.

A novel classical swine fever virus (CSFV) strain GNU-240601 was identified from a commercial live Japanese encephalitis virus (JEV) vaccine. The whole-genome sequence of GNU-240601 shared the highest similarity with strains belonging to subgenotype 1.1. This is the first identification and complete genome sequence of CSFV from the JEV vaccine.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a globally endemic, costly swine arterivirus with wide genetic and antigenic variations, leading to the frequent appearance of novel virulent strains that hampers PRRSV control. Recently, NADC30‐like (lineage 1C, L1C) and NADC34‐like (lineage 1A, L1A) PRRSV strains were reported to be prevalent in mainland South Korea and became the main epidemic strains persistently attributed to PRRSV outbreaks nationwide, raising great concern in the domestic pork industry. Although the genotypic and pathotypic variability of NADC30‐ and NADC34‐like viruses has been explored in the United States and China, their genomic and biological characteristics have been scarcely studied in South Korea. Here, NADC34‐like GNU‐2353 and NADC30‐like GNU‐2377 strains were independently identified from vaccinated swine herds experiencing high piglet mortality. Whole‐genome sequencing and phylogenetic analysis revealed that GNU‐2353 and GNU‐2377 clustered into sublineages L1A (NADC34‐like) and L1C (NADC30‐like), respectively, sharing high genomic homology with their corresponding lineage‐representative strains and harboring the same molecular signatures of continuous 100 and discontinuous 131 amino acid deletions in the nsp2‐coding region, respectively. Recombination detection indicated that GNU‐2353 and GNU‐2377 were recombinants and evolved through natural interlineage recombination between NADC34‐like (L1A, major parent) or NADC30‐like (L1C, major parent) and RespPRRS modified live virus (MLV)–like (lineage 5, minor parent) strains, respectively. Both viruses displayed homogenous growth kinetics but replicated faster than the prototype VR‐2332 in a porcine alveolar macrophage cell line (PAM‐KNU). The transcriptional profiles of immune response genes in infected PAM‐KNU cells varied between the isolates and VR‐2332; particularly, interleukin‐10 expression was dramatically upregulated in cells infected with GNU‐2353 and GNU‐2377. Piglets with GNU‐2353 and GNU‐2377 infection had high fever; weight loss; increased viremia and nasal shedding; viral distribution in various tissues; thymic atrophy; and apparent macroscopic and microscopic lung lesions, including interstitial pneumonia and viral colonization, compared with control piglets, suggesting that both isolates were virulent to pigs. Remarkably, GNU‐2353 caused higher fever, mortality rate (40%) with cyanosis, viremia, and viral shedding within 2 weeks and significantly higher viral loads in several organs than GNU‐2377 infection. Thus, NADC34‐like GNU‐2353 was more pathogenic than NADC30‐like GNU‐2377. Our findings provide insights into the current epizootic circumstance of NADC30‐ and NADC34‐like PRRSV in South Korea and can aid in tailoring improved control strategies.

Lee D, et al. J Vet Sci. 2025 Aug;26:e58. https://doi.org/10.4142/jvs.25074

Introduction Regdanvimab, a monoclonal antibody pharmaceutical, is the first Korean drug approved for treating coronavirus disease 2019 (COVID-19). We analyzed the therapeutic efficacy of regdanvimab in patients with the COVID-19 delta variant infection. Methods We retrospectively reviewed the electronic medical records of patients hospitalized at two Korean tertiary COVID-19 hospitals with COVID-19 delta variant infection between May 26, 2021, and January 30, 2022. To analyze the therapeutic efficacy of regdanvimab, the patients were divided into regdanvimab and non-regdanvimab groups and were 1:1 propensity-score (PS)-matched on age, severity at admission, and COVID-19 vaccination history. Results Of 492 patients, 262 (53.3%) and 230 (46.7%) were in the regdanvimab and non-regdanvimab groups, respectively. After PS matching the groups on age, severity at admission, and COVID-19 vaccination history, each group comprised 189 patients. The 30-day hospital mortality rates (0.0% vs. 1.6%, p = 0.030), proportions of patients with exacerbated conditions to severe/critical/died (9.5% vs. 16.4%, p = 0.047), proportions who received oxygen therapy because of pneumonia exacerbation (7.4% vs. 16.4%, p = 0.007), and proportions with a daily National Early Warning Score ≥ 5 from hospital day 2 were significantly lower in the regdanvimab group. Conclusions We showed that regdanvimab reduced the exacerbation rates of conditions and mortality in patients with the COVID-19 delta variant infection. Thus, it is recommended to streamline the drug approval system during epidemics of new variant viruses to improve the availability and usage of therapeutics for patients. To facilitate this, relevant institutional support is required.

Yang J, et al. J Vet Sci. 2024 Nov;25:e79. https://doi.org/10.4142/jvs.24252

Coronaviruses (CoVs) belonging to the Gamma-CoV and Delta-CoV genera are widespread in poultry and wildfowl. Migratory birds, particularly duck species, serve as hosts for CoVs and play a pivotal role in transmitting the viruses to other species, including mammals. Despite the potential risks to animals and humans, there remains a narrow knowledge of the genetic and epidemiological properties of CoVs in wild birds. The current research aimed to detect and characterize CoVs present in migratory duck species (Anas acuta, Anas platyrhynchos, and Anas poecilorhyncha) from South Korea. Employing two rounds of pan‐CoV real‐time reverse transcription‐polymerase chain reaction (RT‐PCR) and nested PCR (nPCR) assays amplifying the conserved RNA‐dependent RNA polymerase (RdRp) portion common to all known CoVs, we screened 2120 duck fecal samples collected during 2022–2023. The results indicated the presence of CoVs in 4.2% (91/2120) of samples from migratory ducks. Nucleotide sequencing of the RdRp gene revealed that all identified CoVs were clustered within the Gamma-CoV genus. Further phylogenetic analysis suggested that South Korean gamma‐CoVs belong to the Igacovirus subgenus and share similarities with those found worldwide, highlighting the critical role of migratory ducks in introducing and exporting avian CoVs. We discovered two clade VII igacovirus strains in wild ducks closely related to those in pigeons, implying potential cross infection between these avian species. Overall, our study underscores the importance of active surveillance and monitoring of avian CoVs in wild birds as a preemptive response against the forthcoming emergence of new CoV species that can threaten both animal and human health.