STUDIES ON THE FLEXNER GROUP OF DYSENTERY BACILLI IlL ANTIBODY RESPONSE IN MAN FOLLOWING THE ADMINISTRATION OF THE SPECIFIC ANTIGEN OF TYPE V SHIGELLA PARADYSENTERIAE (FLEXNER)* BY ELY

The prophylactic immunization of man against bacillary dysentery has proved to be a difficult problem. The severe reactions evoked by the toxic microorganisms used in vaccines (1, 2), the multiplicity of bacterial types encountered in the disease, and the difficulties experienced in evaluating the efficacy of vaccines are all factors which have impeded progress in the control of the disease by immunological measures. During the past year we have been engaged in a study of the specific antigens of the Flexner group of dysentery microorganisms. Our purpose has been to learn something of the chemical nature of these substances and something of their immunological and toxic properties as well. The specific antigens of the Flexner organisms are lipocarbohydrate-protein complexes similar to those isolated by other investigators from various Gram-negative bacilli (3-5). These substances appear to reflect the essential imrnunological properties of the microorganisms from which they are derived. They are toxic and give rise in experimental animals to antisera which agglutinate the homologous organism, precipitate the antigen, and confer passive protection on mice against lethal infections. Numerous attempts have been made to modify or detoxify vaccines of dysentery bacilli for purposes of prophylactic immunization, but thus far this has not been satisfactorily achieved (2, 6-11). In an effort to avoid the toxic reactions evoked by the injection of certain Gram-negative organisms, other investigators have separated the O antigens from extraneous cellular elements and have used these substances experimentally in man (12, 13). Because organisms of the Shigella paradysenteriae (Flexner) group are those most frequently encountered in areas where bacillary dysentery is prevalent (14-21) and because of the difficulties experienced with the use of whole bacterial vaccines, we have studied the response in man to the injection of the specific antigen of the Type V organism. The antigen of this type cross-reacts with other organisms of the group and was, therefore, chosen in the present study.