Analysis of Leptospira antigens by crossed immunoelectrophoresis.

Serovars icterohaemorrhagiae, canicola, and arboreae of pathogenic Leptospira interrogans and serovar patoc of saprophytic L. biflexa were examined by crossed immunoelectrophoresis. A close antigenic relationship was found between the interrogans serovars, particularly between icterohaemorrhagiae and canicola. To a much lesser extent cross-reactions were found between interrogans serovars and patoc. Comparison of three different antigenic preparations of icterohaemorrhagiae by tandem crossed immunoelectrophoresis and by absorption experiments with the patoc reference system showed the presence of several common broadly reactive antigens. Antigen 1 of the reference system, a genus-specific heat-stable protein antigen, was found in all antigenic preparations. It is a diagnostically important antigen.