Immunoreactivity of fractionated antigens obtained from autoclaved extracts of an arthritogenic isolate of Erysipelothrix rhusiopathiae

The immunoreactive antigens in heat-extracted (autoclaved) preparations of an arthritogenic strain of Erysipelothrix rhusiopathiae (isolate VRS 229, serotype 1a) have been identified by gel diffusion precipitin (GDP) tests and a novel application of the enzyme linked immunosorbent assay (ELISA) procedure. Antigens precipitated by ethanol treatment of autoclaved extracts of this strain were resolved into 4 major peaks (A,B,C and D) after gel permeation chromatography on Sephacryl S200. Peak A was confirmed as a protein peak (Lowry positive) which was excluded from the gel. This peak was identified to be ELISA-reactive when assayed with serum from pigs infected with other isolates corresponding to serotypes 1a, 1b and 2. However, it did not form precipitin lines in GDP tests. Peak B was Lowry-positive and also contained carbohydrates. It was not as reactive in ELISA tests but rapidly formed precipitin lines with serum from pigs infected with the homologous isolate, but only erratically with serums from pigs infected with other serotype 1a and 1b isolates, and not with serotype 2 isolates. Peaks C and D were high in carbohydrate and phosphate content respectively but were both non-reactive in GDP tests and only slightly so by ELISA. Since serotypes 1 and 2 are the most predominant among isolates from infected pigs it is likely that the commonly recognised A antigen is a useful ELISA reagent for the diagnosis of E. rhusiopathiae infection; B antigen on the other hand, would probably be of limited diagnostic value.