Preparation of the Specific Polysaccharide of Type I Pneumococcus

Abstract

It was shown 1 that preparation of the specific polysaccharides of Types II and III pneumococcus in the cold and without the use of strong acid or alkali gave products forming much more viscous solutions than did the polysaccharides isolated by the older methods, 2 but apparently differing otherwise from the older preparations only in their ability to precipitate more antibody from homologous rabbit antisera. These differences were attributed to the greater chain length of the molecules of the new preparations.

The acetyl polysaccharide from Type I pneumococcus has now been similarly prepared. This product had the chemical and physical properties of the acetyl polysaccharide reported by Avery and Goebel 3 but gave solutions of much higher viscosity than did samples prepared according to Reference 3, and precipitated twice as much antibody nitrogen from a Type I antipneumococcus rabbit serum. Thus a solution of the new preparation, S 120, containing 1 mg. per ml. in 0.9% saline had a relative viscosity, η_r, of 1.69. After 8 hours in a sealed tube at 100° this solution showed η_r = 1.05. After treating with N/2 NaOH for 40 hours at 37° C. η_r was 1.20. A preparation, S91a, isolated from culture filtrate concentrated on the steam bath gave η_r = 1.10.

Table I shows the amount of antibody nitrogen precipitated from rabbit and horse Type I antipneumococcus sera by an excess of the different preparations of Type I pneumococcus specific polysaccharide (SI).

As was found with S II and S III the use of heat as in the initial concentration of S I lowers its power to precipitate rabbit antisera without greatly affecting its reaction with horse antisera.