Abstract
Summary: Several P. pestis cell wall antigens were prepared by repeated ultrasonation, and their toxicity and immunogenicity were studied and compared with killed virulent whole organism vaccine by means of toxicity, serologic and immunogenicity tests in guinea pigs and mice. The antigenic components were determined with the gel diffusion test. Preparation of the residue antigens requires a large quantity of starting material and is complicated in comparison with the preparation of killed whole organism vaccine. The solubility of the final material was less than that reported elsewhere. Only a small amount was available for toxicity tests, and this was toxic to neither mice nor guinea pigs. Guinea pigs inoculated with TJW or E. V. 76 in distilled water preparations had rather severe local reactions. The immunogenicity of the tested vaccines was satisfactory and similar except in a few tests in which the whole organism vaccine was superior to the others. In the test system, in which the interval between immunization and challenge was rather short, the antibody response expressed in serologic tests was not pronounced, but in some instances it gave a rough prediction of immunity. The virulence antigens V and W did not play an essential role in these tests. The immunity was directly related to Fraction I antibody. The administration of the whole organism vaccine in oil adjuvant to guinea pigs enhanced and sustained Fraction I antibody formation.