Protection of pigs from swine dysentery by vaccination with recombinant BmpB, a 29.7 kDa outer-membrane lipoprotein of Brachyspira hyodysenteriae

Swine dysentery (SD) is an important endemic infection in many piggeries, and control can be problematic. In this study the efficacy of BmpB, a 29.7 kDa outer-membrane lipoprotein of Brachyspira hyodysenteriae, was evaluated as an SD vaccine. Non-lipidated BmpB was expressed in Escherichia coli as a histidine-tagged protein (His₆-BmpB), or as an 8 kDa carboxy-terminal portion fused to maltose-binding protein (MBP-BmpB-F604). The purified proteins were emulsified with oil-based adjuvants for intramuscular (im) administrations. In experiment 1, 20 weaner pigs were vaccinated im with 1 mg of His₆-BmpB. After 3 weeks, 10 received 1 mg of the protein orally (im/oral), and 10 received 1 mg im (im/im). Ten acted as unvaccinated controls. In experiment 2, 12 pigs were vaccinated im with 1 mg of His₆-BmpB, and 12 with 1 mg of MBP-BmpB-F604. Three weeks later, each was given 1 mg of the same protein orally. Twelve pigs acted as unvaccinated controls. All pigs were challenged orally with B. hyodysenteriae 2 weeks after their second vaccination. In both experiments, all pigs vaccinated with His₆-BmpB developed serum antibodies to BmpB, and oral administration provided boosting of im-induced serum antibody titres. In experiment 1, seven non-vaccinated control pigs developed dysentery and severe colitis. Three pigs vaccinated im/oral developed diarrhoea; two had severe colitis and one had mild lesions. Four pigs vaccinated im/im developed diarrhoea; one had severe colitis and the others had mild lesions. In experiment 2, six control pigs developed SD with severe colitis. Two His₆-BmpB vaccinated pigs developed SD with mild colitis. Nine pigs vaccinated with MBP-BmpB-F604 developed SD and severe colitis. Overall, 50-70% of controls and 17-40% of His₆-BmpB vaccinated pigs developed disease. Vaccination with MBP-BmpB-F604 did not induce serum titres against BmpB, nor confer protection. The incidence of disease for the three His₆-BmpB vaccinated groups was significantly less (P = 0.047) than for the control groups, with a ∼50% reduction. BmpB appears to have potential as an SD vaccine component.