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Cross-protection induced in mice by immunizations with proteins of related bacteria species
Groups of mice were immunized with detoxified protein from S. typhimurium, S. paratyphi B and S. paratyphi C. Consecutive infections with different concentrations of the homologous and heterologous strains showed that: 1. Immunizations with proteins from S. typhimurium induced protections in 65% of the mice infected with 50 LD100 of their natural pathogen, and in 80% of the mice infected with 50 LD100 of S. paratyphi B; the infection with S. paratyphi C of mice in this group afforded protection against 20 LD100 in 75% of the animals. 2. Immunization with proteins from S. paratyphi B induced protection in the mice against the infection with 20 LD100 of S. typhimurium (survival of 80% of the mice) and against 20 LD100 of the homologous S. paratyphi B (survival of 90% of the mice). 3. Immunization with proteins from S. paratyphi C protected the mice against the infection with 20 LD100 of S. typhimurium in a proportion of 80-85% of the animals; infection with the homologous S. paratyphi C did not result in protection against more than 20 LD100 of the bacteria (80-85% survivals). The survivors, in each group, when reinfected 30 days later with 50 LD100 of S. typhimurium resisted in a proportion of 100%, as a consequence of antibodies induced against more specific proteins released in the mice during the infections by the related pathogens.
Groups of mice were immunized with detoxified protein from S. typhimurium, S. paratyphi B and S. paratyphi C. Consecutive infections with different concentrations of the homologous and heterologous strains showed that: 1. Immunizations with proteins from S. typhimurium induced protections in 65% of the mice infected with 50 LD100 of their natural pathogen, and in 80% of the mice infected with 50 LD100 of S. paratyphi B; the infection with S. paratyphi C of mice in this group afforded protection against 20 LD100 in 75% of the animals. 2. Immunization with proteins from S. paratyphi B induced protection in the mice against the infection with 20 LD100 of S. typhimurium (survival of 80% of the mice) and against 20 LD100 of the homologous S. paratyphi B (survival of 90% of the mice). 3. Immunization with proteins from S. paratyphi C protected the mice against the infection with 20 LD100 of S. typhimurium in a proportion of 80-85% of the animals; infection with the homologous S. paratyphi C did not result in protection against more than 20 LD100 of the bacteria (80-85% survivals). The survivors, in each group, when reinfected 30 days later with 50 LD100 of S. typhimurium resisted in a proportion of 100%, as a consequence of antibodies induced against more specific proteins released in the mice during the infections by the related pathogens.