Lymphoproliferative responses in mesenteric lymph node of pigs inoculated with either classical or pandemic PEDV variant

Porcine epidemic diarrhea (PED), a devastating enteric disease, has caused severe economic losses to swine industry worldwide since its emergence in 1977. Due to PED virus (PEDV) causing enteric infection, local immunity including secretory IgA is more important for protection compared to systemic immunity. Cellular immunity also plays an important role in the protection and disease recovery. The objectives of the study were to investigate cellular response in mesenteric lymph node following oral exposure either classical or pandemic PEDV variant.

Eighteen, 3-weeks-old pigs were randomly allocated into 2 groups of 9 pigs each, including Classical and Pandemic groups. Pigs in classical and pandemic groups were orally challenged with 2 ml of 10⁴ TCID₅₀/ml of either classical or pandemic PEDV variant. Three pigs per group were randomly selected and necropsied at 3, 7 and 14 days post-infection (dpi). Mesenteric lymph node was collected and mononuclear cells (MNCs) were isolated and lymphocyte proliferation assay (LPA) was performed using carboxyfluorescein diacetatesuccinimidyl ester (CFSE) assay. In vitro stimulation included mock, PHA, classical or pandemic PEDV variant at MOI of 1. Stimulating index (SI) was calculated and subgroups of MNC stimulation consisting of classical inoculated - classical stimulated (CI-CS), classical inoculated - pandemic stimulated (CI-PS), pandemic inoculated - pandemic stimulated (PIPS) and pandemic inoculated - classical stimulated (PI-CS).

The specific lymphocyte proliferation was first detected at 3dpi and maintain until the end of study (except group PI-CS decrease in 14 dpi). The peak of SI was observed at 3 dpi, 14 dpi, 3 dpi and 7 dpi in group CI-CS (3.29), CI-PS (2.02), PI-PS (1.32) and PI-CS (1.31), respectively. Especially, SI of group CI-CS at 3 dpi was significantly higher than other group whereas SI in group PI-CS was significantly lower than group CI-CP and CI-PS. However, no difference of SI between groups at 7 dpi.

Based on lymphoproliferative responses of mesenteric lymph node, response of classical variant-inoculated pigs were relatively higher than that of pandemic variant-inoculated pigs. Response against homologous stimulation was relatively higher than that of response against heterologous stimulation in both inoculated groups.

Disclosure of Interest: None Declared.