Serological characterization of Actinobacillus pleuropneumoniae serotype 2 strains by using polyclonal and monoclonal antibodies

The antigenic differences between strains of serotype 2 of both biotypes I and II of Actinobacillus pleuropneumoniae were studied by using several serological techniques. Monoclonal antibodies (MAbs) against A. pleuropneumoniae biotype I serotype 2 were produced by fusion of spleen cells of BALb/c mice immunized with whole-cell (WC) suspension with SP2/O-Ag14 murine myeloma cells. Desirable MAbs were selected by enzyme-linked immunosorbent assay (ELISA) using WC as antigen. MAbs MK-7 and MK-10 identified multiple bands of lipopolysaccharide in Western-blot. Treatment of WC with proteinase K and sodium periodate indicated that both MAb binding sites were carbohydrates in nature. In both ELISA and Western-blot, MAbs MK-7 and MK-10 recognized only biotype I serotype 2 isolates. Neither MAb MK-7 nor MK-10 reacted with reference strains of remaining serotypes of A. pleuropneumoniae and other Gram-negative bacteria tested. The results obtained with various serological tests showed that strains of serotype 2 biotype I shared antigenic determinants with strain N-282 of serotype 2 biotype II, but not with strain N-273 of serotype 1 biotype II. It is suggested that data obtained from this study may be helpful in the development of specific serotyping and serodiagnostic reagents of A. pleuropneumoniae strains.