Abstract
Clostridioides difficile is an anaerobic bacterium that causes disease in both animals and humans. Despite the known significance of this agent, there are no commercial vaccines available for humans, and only one immunogen is marketed for swine. However, no studies have evaluated this vaccine. BACKGROUND/OBJECTIVES: Therefore, the aim of this study was to assess the potency of the first commercial vaccine for C. difficile infection in piglets and to compare the humoral response in rabbits and sows. METHODS: Pregnant sows were divided into two groups: a vaccinated group (n = 12), receiving two doses before farrowing, according to the manufacturer's recommendation, and an unvaccinated control group (n = 6). Blood samples were taken from sows and also from piglets up to two days after birth. In addition, two groups of New Zealand rabbits (Oryctolagus cuniculus) received either a half-dose (G1) or a full-dose (G2) of the vaccine, with a control group receiving sterile saline (0.85%). Rabbits were vaccinated twice, 21 days apart, with blood samples collected before each dose and 14 days after the final dose. A serum neutralization assay in Vero cells was performed to evaluate the titers of neutralizing antibodies. RESULTS: The vaccine demonstrated immunogenicity by stimulating the production of neutralizing antibodies in both rabbits and sows. Additionally, these antibodies were passively transferred to piglets through colostrum, reaching levels comparable to those found in sows. Furthermore, vaccinated rabbits developed antibody titers that do not significantly differ from those obtained in sows and piglets. CONCLUSIONS: The tested vaccine can induce a humoral immune response against C. difficile A/B toxins in sows and these antibodies are passively transferred to neonatal piglets through colostrum. Also, the vaccination of rabbits might be a useful alternative for evaluating the potency of vaccines against C. difficile.