Postdoc Research Associate Iowa State University Ames, Iowa, United States
Disclosure(s):
Marlene Bravo Parra, MSc PhD: No financial relationships to disclose
Introduction/Rationale: Porcine epidemic diarrhea virus (PEDV) is an alphacoronavirus that causes severe enteric disease in swine, leading to high neonatal mortality and growth impairment. Oral vaccines can target gut-associated lymphoid tissue, yet the coordination of mucosal and systemic responses during oral immunization remains poorly characterized. This study assessed a maize-expressed PEDV-S1 oral vaccine by characterizing clinical outcomes, viral shedding and lymphocyte cytokine kinetics following challenge
Methods: Sixty 3-week-old PEDV-negative pigs were assigned to four groups (n=15): Control, Vaccine-1, Vaccine-2 (with adjuvant), and Challenge (2x). Vaccine groups received a prime-boost regimen before oral challenge with a non-S INDEL PEDV strain on day 35. Challenge (2x) pigs received two live inoculations. Clinical signs, body weight, and fecal viral RNA were monitored. Necropsies on days 7–45 provided samples for flow cytometry of T, B, γδ-T, NK and regulatory subsets expressing IFN-γ or TNF-α
Results: Oral vaccination altered disease and immunity. Vaccine-1 pigs showed shorter diarrhea, while Vaccine-2 pigs had mild but longer diarrhea yet greater day-45 body weight than Controls (p < 0.01) and Challenge (2x) (p < 0.05). Viral shedding was highest in Controls (p < 0.01), intermediate in vaccinated pigs and lowest in Challenge (2x) animals after their second exposure. Mesenteric lymph nodes (MLN) profiling showed increased CD4⁺ T cell activation on day 21 in Challenge (2x) pigs and elevated B cells (CD21⁺SLA-II-DR⁺) on day 37 across all antigen-experienced groups. IFN-γ⁺ CD4⁺/CD8⁺ cells were reduced at days 7–21 in antigen-experienced groups, consistent with trafficking from MLN. TNF-α⁺ subsets remained low whereas γδ-T cells increased from days 21-45 with group-specific patterns. FOXP3⁺CD25⁺ T cells remained stable
Conclusion: Maize-expressed PEDV-S1 oral immunization induced coordinated mucosal and systemic immunity, reduced disease and improved growth supporting its value as a practical tool for swine health
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