[Use of hybrid strains of S, typhi and S. typhimurium for characterizing the biological activity of individual Salmonella antigens by the alternative recording of the experimental results].

Intraperitoneal infection of mice, subcutaneously immunized with acetone vaccines of various antigenic composition, with the microbes of hybrid salmonellae strains of murine and typhoid fever caused development of infectious process approaching natural infection. A significant elevation of the intensity of immunity was provided by preparations containing serologically identical O-antigen in infection with O-strains, or Vi-antigen in infection with Vi-strains. For the formation of animal resistance to infection it was necessary to immunize the mice with vaccines containing homologous H- and O-antigens (in infection with O-strains) and H-, O- and Vi-antigens (in infection with Vi-strains). Immunization with killed vaccines with a full-value antigenic structure provided effective protection of mice from doses approaching LD50.