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

Two antigens of polysaccharidic nature were evaluated for their specificity in serodiagnosis of porcine pleuropneumonia (serotype 5). Recently, long chains lipopolysaccharides (LC-LPS) was shown to increase the specificity of the ELISA test for A. pleuropneumoniae serotype 5 compared to a saline extract of boiled-formalinized whole cells. Nevertheless, some cross reactions were noticed with LC-LPS. We have thus cleaved the LPS molecule at the ketosidic bond between the lipid A and the core. The lipid A was separated from the polysaccharide (PS) by centrifugation. With an indirect sandwich ELISA, it was possible to demonstrate that the PS yielded positive responses with homologous sera (serotype 5) and negative responses with heterologous sera (serotype 3 and undeterminated serotype). Overall, the use of the PS did not notably increase 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 recommend its use in serodiagnosis.