Mucosal immune response in pigs following the primary and secondary exposure to porcine epidemic diarrhea virus genogroups G1 and G2

Abstract

This study was conducted to evaluate cellular and humoral mucosal immune responses of pigs infected with porcine epidemic diarrhea virus (PEDV) genogroups 1 (G1) or 2 (G2). Anamnestic response following homologous or heterologous reinfection were also investigated. Forty-five PEDV-negative, 3-week-old pigs were allocated into 3 groups of 15 pigs each. Pigs were orally inoculated with EAS1 (G1) or CBR1 (G2) or cell culture supernatant and serially monitored for PEDV-specific IFN-γ producing cells (IFN-γ PC) and IgA antibody secreting cells (ASC). Three pigs served as baseline at day 0. The CD4⁺IFN-γ⁺ PC in G1 group was detected at 3 days post infection (dpi) in both EAS1 and CBR1 recall antigen. In contrast, CD4⁺IFN-γ⁺ PC in G2 group detected only when EAS1 was used. Similar findings were found with CD8⁺IFN-γ⁺ PC. After reinfection, only G2 exhibited a booster effect of CD4⁺IFN-γ⁺ and CD8⁺IFN-γ⁺ cells by heterologous antigen recall. Regarding CD4⁺CD8⁺IFN-γ⁺cells, G1 showed significantly higher levels at 3 dpi and demonstrated a secondary boost at 14 dpi following heterologous recall stimulation. In contrast, G2 showed a slight increase in response to both homologous and heterologous recall at 3 dpi. PEDV-specific IgA ASC were detected at 14 dpi. However, anamnestic response after reinfection was variant-dependent. Our results indicate that the G1 variant specific cellular response is triggered earlier or simultaneously than G2 variant. Meanwhile, the timing of humoral response was similar, and anamnestic response was driven by the variant involved during reinfection.