Jianzhu Li

Porcine epidemic diarrhea virus (PEDV) causes severe enteric disease in piglets. The spike (S) gene is the major target of neutralizing antibodies and a hotspot for genetic variation. In this study, eight PEDV S-gene sequences were obtained from a commercial pig farm in Guangxi, China, between 2021 and 2025. Phylogenetic analysis assigned all sequences to the G2 genotype, with G2c, G2d, and G2b subclusters detected at different time points. Recombination analysis identified sequence-level recombination signatures in the G2c sequences, with G2b-like and G2d-like sequences as parental relatives. Several amino acid substitutions were located within or adjacent to the COE and SS2 neutralizing epitopes, and N-glycosylation site variations were observed among subclusters. Structural predictions suggest that these combined changes may alter surface antigenic properties and confer immune evasion potential, though functional validation using neutralization assays is still required. These findings provide field-derived evidence for PEDV genetic evolution and recombination within a single swine herd, and support rational vaccine-strain evaluation and on-farm biosecurity strategies.

Heat stress, one of the major challenges facing the global livestock industry, can adversely affect the immune system. The present study explored the mechanisms by which melittin alleviates heat stress-induced immune organ damage. Three hundred 20-day-old male Huainan sheldrakes were randomly assigned to four groups: heat stress group (basal diet), heat stress + melittin group (I, II, III group, basal diet + 0.08, 0.12, 0.16 g/kg melittin, respectively). The ducks were subjected to heat stress for 4 h per day (temperature 36–38 °C, relative humidity 60–70%) for 15 consecutive days. The results showed that compared with the heat-stress group, melittin improved the production performance of heat-stressed ducks, significantly increased serum immune indices (immunoglobulin G and interferon‐gamma) and antioxidant indices (total antioxidant capacity, superoxide dismutase (SOD), and glutathione) (P < 0.05), and significantly decreased malondialdehyde (MDA) levels (P < 0.05). Additionally, melittin increased antioxidant function (nuclear factor-erythroid 2 p45-related factor 2, glutathione peroxidase, SOD, and catalase), and immune index (interleukin-10). Meanwhile, melittin significantly reduced immune indices (inducible nitric oxide synthase and cyclooxygenase-2), heat shock protein 70 expression, and apoptosis levels (P < 0.05) in heat-stressed ducks. Consequently, supplementing heat-stressed ducks with 0.12 g/kg melittin increases serum immune function and antioxidants, alleviate heat stress-induced immune organ damage, and improve growth performance.