Protective activity of the purified protein antigen of Erysipelothrix rhusiopathiae in pigs

We purified the protein antigen (P64), which contains 66 and 64 kDa protein s, from the alkaline extract (AE) of whole cells of Erysipelothrix rhusiopa thiae strain Agata (serovar 5) to determine the protective activity of the antigen against E. rhusiopathiae infection in pigs. The serum titre of anti body against P64 rapidly increased in pigs immunized with 500 and 100 mu g of P64 and reached maximum values at 3 weeks after the first immunization ( 1 week after the second immunization). However. the serum antibody titres w ere not increased in pigs immunized with 20 mu g of P64 and in nonimmunized pigs. In the pigs immunized with live cell vaccine (acriflavin-fast attenu ated strain Koganei 65-0.15), the serum titres of antibody against P64 also increased at 1-2 weeks after immunization. In a pig challenge test perform ed on immunized and nonimmunized pigs, all nonimmunized pigs showed typical clinical signs of swine erysipelias (fever, erysipeloid, arthritis), while all pigs immunized with 500 and 100 mu g of P64 and live cell vaccine show ed no clinical signs of this disease. In Western blot analysis, sera from p igs immunized with P64 and live cell vaccine strongly reacted with the 64 k Da protein. In contrast, the serum from nonimmunized pigs did not react wit h any proteins. From these results, it was suggested that a specific antibo dy against the 64 kDa protein could be increased in pigs immunized with P64 or live cell vaccine and that this anti-P64 antibody has a strong protecti ve effect against E. rhusiopathiae infection in pigs.