IMMUNOLOGICAL COMPARISON OF INTRACELLULAR TOXIN A AND EXTRACELLULAR TOXIN A FROM CLOSTRIDIUM-DIFFICILE

Intracellular toxin A and extracellular toxin A of Clostridium diffici le were compared immunologically. Immunodiffusion tests with anti-intr acellular toxin A and anti-extracellular toxin A sera showed that thes e toxins were identical. In neutralization tests, both antisera neutra lized the homologous and heterologous toxins with regard to cytotoxici ty, mouse lethality and loop response at nearly the same titers. Altho ugh intracellular toxin A lacks the hemagglutination (HA) activity, an ti-intracellular toxin A serum neutralized HA activity of extracellula r toxin A at the same titer as did anti-extracellular toxin A serum. T hese results suggest that these toxins are immunologically indistingui shable and that the intracellular toxin A molecule has an antigenic si te(s) for the HA activity.