Preparation and partial characterization of monoclonal antibodies against the protective protein antigen of Erysipelothrix rhusiopathiae.

Thirteen mouse monoclonal antibodies (Mabs) against the protective protein antigen (P64) of Erysipelothrix rhusiopathiae were prepared and partially characterized. The titres of the Mabs varied from 200 to 1,638,400 as determined by enzyme-linked immunosorbent assay (ELISA). Of the 13 Mabs 10, two and one belonged to the IgG2a, IgG1 and IgM subclasses, respectively. All Mabs reacted strongly with the 64 kDa protein and weakly with the 43 kDa protein upon Western blotting of the alkaline extract (AE) of E. rhusiopathiae. The protective activity (PD50/ml) of the 13 Mabs against E. rhusiopathiae infection in mice varied from < 50 to > 50,000. These Mabs were classified into three groups, highly protective Mabs, moderately protective Mabs and Mabs which did not possess protective activity, based on the protective index (ratio of the PD50/ml to the antibody titre). These results suggest that the 64 kDa protein is an effective protective antigen, which is easily cleaved into many small proteins, including the 43 kDa protein, and possesses at least two epitopes related to its protective activity and at least one epitope which is not related to protection of mice against E. rhusiopathiae infection.