Recombinant rSF toxoid enhances efficacy of bacterin-inactivated vaccine against F18+ Escherichia coli-induced edema disease in swine.

BACKGROUND: Edema disease (ED) and post-weaning diarrhea (PWD) are major health and economic challenges in the swine industry, primarily caused by F18+ Shiga toxin-producing Escherichia coli (STEC). These diseases typically occur within 1-2 weeks after weaning and are associated with high morbidity and mortality, resulting in substantial economic losses worldwide. The pathogenesis of ED is largely mediated by bacterial adhesion via F18 fimbriae, particularly the FedF adhesin, and systemic toxemia induced by Shiga-like toxin IIe (SLT-IIe). Although passive or active immunization with SLT-IIe toxoids or detoxified variants can provide some protection, their immunogenicity is often limited and may be accompanied by adverse effects. Currently, no commercial vaccines are available, and reliance on antibiotics has accelerated the emergence of multidrug-resistant E. coli. Therefore, the development of safe and effective vaccines targeting both F18 fimbrial adhesion and SLT-IIe-mediated toxemia is urgently needed. RESULTS: Recombinant rSF toxoid (fusion of SLT-IIe B subunit and FedF adhesin) mixed with Ee strain formed a novel rSF toxoid bacterin-inactivated vaccine. Compared to conventional bacterin-inactivated vaccine, the rSF vaccine group showed significantly higher protection efficacy against F18+ SLTEC challenge, with reduced histological scores, attenuated inflammation, decreased creatinine levels, and minimized kidney damage, alongside increased average daily gain and nitric oxide levels. CONCLUSION: rSF toxoid addition safely enhances protection efficacy against F18+ SLTEC and alleviates renal pathology.