LIPOPOLYSACCHARIDES OF ACTINOBACILLUS-PLEUROPNEUMONIAE (SEROTYPE-1) -A READILY OBTAINABLE ANTIGEN FOR ELISA SERODIAGNOSIS OF PIG PLEUROPNEUMONIA

A saline extract of boiled-formalinized whole cells of Actinobacillus pleuropneumoniae serotype 1 reference strain (Shope 4074) has been pre viously used as the antigen in an enzyme-linked immunosorbent assay (E LISA) for serodiagnosis of swine pleuropneumonia. phenol extraction of this crude extract permitted the recovery of LPS with long O-chains i n the aqueous phase. This antigen was shown to be specific for serotyp es 1, 9 and 11 as they all possess structurally similar O-chains. Immu noblotting was used to identify the fraction present in the crude extr act of strain 4074 responsible for cross-reactions observed in ELISA w ith a serum raised against a serotype 3 strain of A. pleuropneumoniae. The specific reactions in ELISA were shown to be associated with long O-chain LPS and the cross-reactions to LPS with short O-chains. LPS s eem to be an important antigen for A. pleuropneumoniae serotype I as a ll homologous sera tested reacted with it. This antigen is easily reco vered from the crude extract and it can be used in minute amounts (1-6 mu g) for ELISA serodiagnosis of pig pleuropneumonia.