Infektionsschutz gegen S. typhimurium im Mausversuch

Abstract

In vaccines consisting of acetone-killed Salmonella, 90% of the bacteria were replaced by: heterologous Salmonella S-forms, R-mutants of Salmonella or Escherichia coli, lipopolysaccharide from S. typhimurium (S-form) or from R-mutants of Salmonella or E. coli and by muramyl dipeptide. Active immunizations of NMRI mice with these vaccines were undertaken. Mice received two intraperitoneal injections of the vaccines at intervals of 14 days, and were challenged with various doses of S. typhimurium C5 10 days later. The protective capacity of the mixed vaccines was compared with that of monovaccines (S. typhimurium) and with the effectiveness of vaccines consisting of the supplementing component (relatively weak immunizing ability) alone. The LD₅₀ served as criterion for protective capacity.

The results showed that S. typhimurium S-form could be replaced by Salmonella R-mutants belonging to different chemotypes without a recognizable decrease in protective immunizing capacity of the vaccines. Effective vaccines were also attained when heterologous Salmonella S-forms, which exhibit no O-antigenic determinants in common with S. typhimurium, were used as supplements. Mixtures with E. coli R-mutants proved to be less effective. In addition, the diminished dose of S. typhimurium could be so effectively supplemented with lipopolysaccharide from S. minnesota R 595 that complete protection was achieved. In contrast, comparable doses of R lipopolysaccharides from E. coli were somewhat less effective. Vaccines of LPS-extracted bacteria exhibited a reduced protective capacity and were ineffective when used as supplements in mixed vaccines.

Analogous results were obtained when R-mutants served as basic vaccines in place of the S. typhimurium S-form indicating that an immunogenic component is enhanced in these organisms too and that their immunogenic capacity is not brought about barely by general stimulation of the immune system. However, the full effectiveness of the R-monovaccines was often not attained with supplements.

Immunization with mixed vaccines of S. typhimurium S-form and heterologous Salmonella S-forms or Salmonella R-mutants led to equally high agglutinin and haemagglutinin titers as those obtained with monovaccines of S. typhimurium S-form.