SERODIAGNOSIS OF SWINE PLEUROPNEUMONIA DUE TO ACTINOBACILLUS-PLEUROPNEUMONIAE SEROTYPE-7 AND SEROTYPE-4 USING LONG-CHAIN LIPOPOLYSACCHARIDES

A saline boiled extract (SEE), capsular polysaccharides (CPS) and long -chain lipopolysaccharides (LC-LPS) of Actinobacillus pleuropneumoniae serotype 7 have been evaluated in ELISA for the serodiagnosis of swin e pleuropneumonia caused by this serotype, Mean optical densities (ODs ) obtained with the 3 antigens using sera from negative herds as well as from animals experimentally and naturally exposed to A. pleuropneum oniae serotypes 7 or 4 were not statistically different. The positive ELISA reaction with anti-serotype 4 sera was unexpected with the CPS, which are supposed to be serotype-specific; LPS traces present in the CPS appeared to be responsible for this reaction, In addition, sera fr om animals exposed to A, pleuropneumoniae serotypes 5 or 10 presented cross-reactions with the SEE and the CPS, but not with the LC-LPS. Cro ss-reactions were mainly due to rough LPS, as shown by immunoblotting. The LC-LPS is easily obtainable and can be used for the detection of antibodies in animals infected with A. pleuropneumoniae serotypes 7 an d 4.