PLAC8 knockout pigs support PEDV replication with altered viral kinetics

Authors: Devries, Alexandra; KIM, HANJUN - Oak Ridge Institute For Science And Education (ORISE); ZANELLA, ERALDO - Oak Ridge Institute For Science And Education (ORISE); Wiarda, Jayne; Redel, Bethany

Submitted to: American Association of Swine Veterinarians Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus infecting swine and causes clinical symptoms of diarrhea, vomiting, and dehydration that are much more severe in neonatal pigs. PEDV continues to circulate in the swine industry, causing significant mortality in neonates when a naïve sow farm is exposed. Current control measures often rely on feedback strategies to provide protection against PEDV since there are limited commercial vaccine options. Placenta-associated 8 (PLAC8) is a protein highly conserved across animal species and broadly expressed in epithelial tissues. In swine, PLAC8 was identified as an essential host factor for swine acute diarrhea syndrome coronavirus (SADS-CoV) infection, another enteric coronavirus infecting swine. Genetically modifying pigs by targeting essential host factors for viral infection is one strategy to prevent or control the spread of viruses in the swine industry. Thus, PLAC8 knockout (KO) pigs were generated with the objective of determining if absence of the PLAC8 gene would provide resistance to PEDV infection. Materials and Methods A total of fifteen weaned pigs were transported and housed in a ABSL-2 animal space. Six pigs were PLAC8 KOs, four were heterozygous (HET), and six were wildtype (WT). Each pig was initially orally inoculated with a PEDV S-INDEL strain; however, animals did not demonstrate any clinical signs and there was no significant viral genome detection in rectal swabs. Therefore, a second oral challenge with a PEDV non-S-INDEL strain USA/NC49469/2013 at a dose of 1000 TCID50 was performed at 7 days post initial infection and was subsequently referred to as 0 days post second infection (0 dp2i) to ensure successful viral infection. Rectal swabs and clinical diarrhea scores were collected daily from 2-7, 10, and 14 dp2i. On 3 dp2i, three animals from each genotype (KO, HET, and WT) were euthanized for tissue collection, while the remaining animals were euthanized on 22 dp2i. Results Most animals developed clinical signs of diarrhea. By 3 dp2i, 3/6 KO animals developed diarrhea ranging from mild to severe. Similarly, 4/5 WT animals showed clinical signs ranging from soft stool to severe diarrhea. Only 1/3 HET animals developed mild diarrhea. By 6-7 dp2i, all remaining KO and WT animals recovered to normal stool consistency. The analysis of PEDV genomic copies in rectal swabs indicated slight variations in viral replication between KO and WT animals. In WT animals, higher viral loads were observed on 3 dp2i. in comparison to KO animals with most values ranging logs lower than WT. Additionally, one HET animal exhibited lower viral copies at 3 dp2i , whereas the other two HET animals displayed viral loads comparable to WT. Differences in PEDV antigen presence by genotype were evident in intestinal tissues collected on 3 dp2i based on immunohistochemistry (IHC) analysis. All three WT animals were PEDV-positive in the duodenum, jejunum, and ileum. In contrast, 2 out of 3 KO animals exhibited negative IHC results across all intestinal segments. Among the HET animals, 2/3 two had positive staining for PEDV. All segments from all animals were PCR positive. Conclusion Findings suggest PLAC8 KO did not provide total resistance to PEDV infection, though a potential genotype-dependent variation in intestinal PEDV infection and antigen distribution may occur. Further investigation is required to verify reproducibility of results and determine off-target effects of PLAC8 KO.