Immunisation of mares with binding domains of toxins A and B of Clostridium difficile elicits serum and colostral antibodies that block toxin binding.

Summary

# Editorial Summary: C. difficile Vaccination in Mares *Clostridium difficile* enterocolitis remains a significant threat to neonatal foals and mature horses, with toxins A and B representing the primary pathogenic mechanisms driving mucosal damage and systemic illness. Researchers immunised pregnant mares with recombinant receptor binding domains of both toxins, then measured serum antibody responses in the vaccinated mares and quantified antibody transfer via colostrum to their foals. Vaccination successfully generated specific serum antibodies in all treated mares, with colostral transfer conferring passive immunity to offspring; critically, these antibodies retained functional blocking capacity against toxin binding in laboratory assays. This approach offers a novel strategy for maternal immunisation to protect vulnerable foals during the high-risk neonatal period through passive antibody transfer, potentially reducing both incidence and severity of *C. difficile*-associated disease. The findings suggest practical application for breeding operations managing disease risk, though efficacy in natural disease challenge scenarios and optimal vaccination timing relative to parturition would warrant further investigation.

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Key Findings

• •Immunisation of mares with C. difficile toxin A and B binding domains elicits specific serum and colostral antibodies
• •Antibodies generated block toxin binding, suggesting potential protective mechanism against C. difficile toxins
• •Maternal immunisation strategy may prevent or reduce severity of C. difficile colitis in nursing foals

Conditions Studied