Virulence and Immunogenic Activities of B. Typhosus in Relation to its Antigenic Constituents

Abstract

1. Rough variants, derived from strains of B. typhosus which possess the Vi antigen, may still contain this antigen though the smooth O antigen has been lost.2. Such variants, which are non-virulent, are yet capable of inducing active and passive immunity.3. The virulence of B. typhosus depends on the combined activity of the smooth O and the Vi antigen. Nevertheless the Vi antibody alone is sufficient to protect against infection with strains of the highly virulent type.4. The use of avirulent, rough, but Vi-containing variants as vaccines and in the preparation of therapeutic sera is discussed.