CHARACTERIZATION OF MONOCLONAL-ANTIBODIES TO O-ANTIGEN OF LIPOPOLYSACCHARIDE OF ACTINOBACILLUS-PLEUROPNEUMONIAE SEROTYPE-2 AND THEIR USE INTHE CLASSIFICATION OF FIELD ISOLATES

Monoclonal antibodies (mAbs) against Actinobacillus pleuropneumoniae s erotype 2 (reference strain Shope 4226 and field isolate F46) were pro duced. Twelve hybridoma clones were selected against both strains, and all the antibodies secreted were found to be reactive with whole-cell antigen of the homologous strain in ELISA, whereas only one mAb was r eactive in slide agglutination test. The predominant antibody classes were IgG2b and IgG3, although IgG1 and IgM were also obtained. Immunob lot assay showed that mAbs could recognize a ladder band profile which is in accordance with the O-antigen of lipopolysaccharide. Most of th e epitopes involved were resistant to proteinase K and also to boiling in the presence of sodium dodecyl sulfate and reducing conditions, bu t they were sensitive to periodic acid. The 12 mAbs recognized neither reference strains of the remaining A. pleuropneumoniae serotypes nor other taxonomically related Gram-negative organisms. The suitability o f mAbs for serotyping of field isolates was also examined, and a high correlation (97.4%) was found between the results previously establish ed by indirect hemagglutination with polyclonal rabbit sera and those obtained by ELISA with mAbs. The panel of mAbs described in this study was found to be extremely useful for identifying field isolates belon ging to serotype 2 and could be used as a complementary serotyping met hod.