IV. Negative Effect of Colloidal Carriers on Enhancement of Antigenic and Sensitizing Properties of Polysaccharides

The rôle played by inert colloidal substances on the enhancement of antigenic properties of bacterial polysaccharides is still a debatable one. Although positive evidence of such an increase in immunological activity has been reported by Zozaya 1 and by Hoffstadt and Clark, 2 the general opinion 3 , 4 , 5 is that such an effect occurs with polysaccharides that are weakly antigenic themselves. In view of these discrepancies it appears to be of interest to determine whether the sensitizing and antigenic properties of the polysaccharides of Bacillus rhinoscleromatis can be improved by colloidal carriers. The polysaccharides of this organism were thought to be especially suitable for this study because of 2 serologically very similar preparations, one is weakly antigenic in rabbits and weakly sensitizes guinea pigs, while the antigenic properties of the other are insignificant 6

The polysaccharides used for this experiment include a fraction prepared by hydrolysis with 1% acetic acid and a fraction prepared by hydrolysis with 0.5% potassium hydroxide of the organism remaining after acid-hydrolysis. The details of the method of preparation and the chemical and immunological characteristics of the 2 fractions have been previously reported. 6 The colloidal substances included collodion particles, aluminium hydroxide, charcoal, and hog serum. The collodion particles were prepared according to the methods of Zozaya 1 and the aluminium hydroxide according to the method of Hektoen and Welker. 7 Adsorption was carried out by mixing varying concentrations of polysaccharide with the colloidal substance, incubating at 56°C for 2 hours and leaving in the icebox overnight. In the case of hog serum equal volumes of a 1:250 concentration of polysaccharide and serum were mixed and treated in the same manner. Twenty-eight normal rabbits were divided equally into 2 groups: Group I receiving the acid-prepared polysaccharide mixed with colloidal substances and Group II receiving the alkali-prepared polysaccharide.