Protective effect of NaOH-extracted Erysipelothrix rhusiopathiae vaccine in pigs

A vaccine was prepared from a NaOH-extracted antigen of the Kyoto strain (serovar 2) of Erysipelothrix rhusiopathiae (E. rhusiopathiae) with an oil adjuvant, and was injected twice at 3-week intervals into SPF pigs and conventional pigs with maternal antibodies. After the second vaccination, IgG-GA titers of immunized SPF pigs were more than 256-fold at 3 weeks, and immunized pigs with maternal antibodies were 64-fold at 7 weeks. The pig with maternal antibodies vaccinated once with live vaccine had less than 4-fold titers. The ELISA antibody titers which were measured by using the NaOH-extracted antigen showed similar transition to the IgG-GA antibody titers. All immunized pigs and nonvaccinated control pigs were challenged with the strains Fujisawa (serovar 1a) or Saitama-1 (serovar 2). After challenge exposure, all pigs immunized with the NaOH-extracted vaccine showed no clinical signs and survived, and the pig immunized with the live vaccine had a local rhomboidal lesion at the site of the injection. Nonvaccinated pigs developed typical symptoms of E. rhusiopathiae infection and one of them died. After the autopsy, the challenge strains were not recovered from the main organs except tonsils of the pigs immunized with the NaOH-extracted vaccine. These results indicated that the NaOH-extracted vaccine induces a protective effect in pigs with maternal antibodies as well as in SPF pigs negative for such antibodies, and that 67-64, 62-60 kDa proteins in the NaOH-extracted antigen play an important role in protecting against E. rhusiopathiae infection.