COMPARISON OF 2 POLYSACCHARIDIC ANTIGENS FOR ELISA SERODIAGNOSIS OF PIG PLEUROPNEUMONIA (SEROTYPE-5)

Two antigens of polysaccharidic nature were evaluated for their specif icity in serodiagnosis of porcine pleuropneumonia (serotype 5). Recent ly, long chains lipopolysaccharides (LC-LPS) was shown to increase the specificity of the ELISA test for A. pleuropneumoniae serotype 5 comp ared to a saline extract of boiled-formalinized whole cells. Neverthel ess, some cross reactions were noticed with LC-LPS. We have thus cleav ed the LPS molecule at the ketosidic bond between the lipid A and the core. The lipid A was separated from the polysaccharide (PS) by centri fugation. With an indirect sandwich ELISA, it was possible to demonstr ate that the PS yielded positive responses with homologous sera (serot ype 5) and negative responses with heterologous sera (serotype 3 and u ndeterminated serotype). Overall, the use of the PS did not notably in crease the specificity of the ELISA test. Since production of PS from LC-LPS and its separation from the lipid A is not simple, we do not re commend its use in serodiagnosis.