Polysaccharide Antigens of Leptospires

A substance, fraction 1, has been isolated from each of Leptospira ictero hemorrhagiae, Leptospira canicola, and Leptospira bataviae. It contains a genusspecific principle in association with a polynucleotide moiety. The antigen reacts in the complement fixation test, preferentially with homologous hyperimmune serum, but cross reacts to an appreciable extent with heterologous hyperimmune serums within the leptospire group. Nucleic acids and trace amounts of protein are probably not determinants of serological activity. Evidence is presented which suggests that the active principle is a complex polysaccharide, largely pentosan in nature, and is analogous to the somatic polysaccharide "C" substance of bacteria. Chemical differences have not yet been established for similarly prepared cellfree extracts from three serotypes of leptospires, although their serological differences are apparent.