Immunochemical Studies on Chlamydial Group Antigen (Presence of a 2-Keto-3-Deoxycarbohydrate as Immunodominant Group)

The group reactive, water soluble polysaccharide antigens of the organisms of psittacosis, lymphogranuloma venereum and trachoma were chemically characterized. An acidic polysaccharide of large molecular weight was purified by DEAE-cellulose column chromatography. Its antigenic activity was destroyed both by periodate (0.005 M) and by mild acid hydrolysis (0.1 N sulfuric acid at 80°C for 1 hr). An acidic component, which separated from the rest of the polysaccharide by mild acid hydrolysis, gave a positive thiobarbituric acid test and negative resorcinol test characteristic of 2-keto-3-deoxyoctanoic acid. On paper chromatography its behavior was similar to but not identical with that of 2-keto-3-deoxyoctanoic acid from Salmonella lipopolysaccharides. The ease with which antigenicity was destroyed by periodate and mild acid hydrolysis suggests that this acidic component is critical for antigenicity.