Type-Specific Polysaccharides of C. diphtheriae.

Abstract

Polysaccharides derived from gravis, intermediate, and mitis types of C. diphtheriœ were found to be group-specific. 1 Recent findings, 2 however, indicate that any of these different cultural types may be present in a single serological type. Because of this an attempt was made to extend our previous study to include polysaccharides of different serological types of C. diphtheriœ with the object of determining the existence of type-specific polysaccharides.

One organism from each of 5 distinct serological types kindly supplied to us by Sia and Huang 2 was employed for the present study. All organisms, with the exception of Park 8 (Type D41) were isolated locally. The various characterizations of these organisms were as follows:

All of the cultures were capable of eliciting precipitin antibodies in rabbits from 4 to 5 weeks when administered intravenously as heat-killed vaccines. The cultivation of organisms, the preparation of polysaccharides, and the immunization of rabbits were the same as those described previously. 1 Absorption test was performed by mixing immune serum diluted 1:5 with well-washed living organisms grown on serum broth at 37°C for 48 hours and the mixture was incubated at 45°C waterbath for 2 hours. It was refrigerated overnight after which the serum was separated by rapid centrifugation.

It was found that 2 kinds of polysaccharide could be demonstrated by the precipitin reaction and by absorption tests. These polysaccharides will be designated as A and B. Polysaccharide A was present in the types D25, D30, D41, and X. Identical precipitin titers varying from 1:50,000 to 1:100,000 were obtained when polysaccharides A were mixed in the ring test with the homologous as well as the heterologous immune sera prepared with the above types. Cross absorption tests performed by mixing immune serum with organisms belonging to any of the types D25, D30, D41, and X showed a removal of all precipitins without affecting the type-specific agglutinins.