Studies on Vi Antigen

Abstract

Summary Vi antigens derived from three V form enteric species by a uniform isolation procedure were examined in a variety of immunological tests. The antigens derived from E. coli and P. ballerup were significantly more active than the Vi antigen obtained from S. typhosa in hemagglutination, quantitative complement fixation, and quantitative precipitin tests. Antigenic activity measured in terms of stimulation of antibody production in rabbits and active immunization of mice against challenge with S. typhosa revealed that coli Vi antigen was the most potent, followed by Vi antigen from ballerup, while the Vi antigen isolated from S. typhosa was the least effective. These differences were established most clearly in the mouse protection tests. The relationship of these biological activities to specific viscosity of the antigen preparations and the possibility of this being a causal relationship was considered. Attention was drawn to certain similarities between the biological properties of the Vi antigens and the pneumococcal polysaccharides.