An Erythrocyte-Sensitising Antigen from Vibrio Cholerae

Erythrocyte-sensitising antigens (AE) were prepared from Vibrio cholerae serotypes, from El-Tor vibrio, Escherichia coli and Salmonella enteritidis by digesting the organisms with NaOH followed by precipitation with alcohol. When AE was used in indirect haemagglutination (IHA) tests, the results in a number of cases were somewhat more sensitive and more specific than those obtained in classical agglutination tests. No cross reactions occurred between V. cholerae serotypes and E. coli and S. enteritidis. Much of the reactive part of the AE was not sedimentable at 100,000 g for 1 h. The eluant from the V. cholerae AE on Sephadex G-200 yielded three fractions, one of which was the most active in IHA tests. Treatment of the AE with trypsin resulted in an appreciable increase in the heterotypic serum titres in IHA tests. The spectrophotometric absorption of the AE at 260 nm showed a hump that may have been indicative of the presence of nucleic acid. Treatment of the antigen with ribonuclease reduced its nucleic acid content but did not change to any significant extent the reactivity of the preparation. The AE antigen of V. cholerae was Molisch-positive and was capable of sensitising untanned erythrocytes in IHA tests. It is suggested that the reactive part of the AE antigen is a carbohydrate complex.