STUDIES ON THE FLEXNER GROUP OF DYSENTERY BACILLI

Abstract

The purified specific antigen of Type V S. paradysenteriae was administered intracut. to a group of 19 volunteers. The sera of the subjects obtained 3 weeks following the course of inoculations showed agglutinins for the homologous Type V microorganism in high titre as well as agglutinins in lower titre for heterologous Flexner types. The pooled sera showed a 10-fold increase in homologous mouse protective antibodies and a 2-fold increase against a heterologous Type Z micro-organism. 2.5 [gamma] of antigen is a safe initial dose. This amt. gives rise to a moderate local reaction, but in no instance to systemic reactions. The optimum immunization schedule appears to be 2.5, 7.5 and 15 [gamma] of antigen given at weekly intervals. Prolonged immunization does not increase the antibody response, nor will it increase the tolerance of the individual to a dose of antigen 25 [gamma]. Sera obtained after 6 months showed but a slight fall in agglutinin titre which could be reestablished with a small recall dose. The purified polysaccharide hapten of the Type V antigen was also administered to a small group of volunteers in a single dose of 50 or 100 [gamma]. Only 2 of the individuals responded with an increase in bacterial agglutinins. The more potent serum was found to contain a 3-fold increase in mouse protective antibodies. The practical aspects of large scale prophylactic immunization are discussed.