Studies on vaccination against bacillary dysentery. 1. Immunization of mice against experimental Shigella infection.

In the course of a series of experiments begun in 1954 a number of different killed vaccines prepared from Shigella flexneri 1 and 2a serotypes were tested for their immunogenicity after intraperitoneal administration in mice followed by challenge with virulent organisms of the same serotype; some live vaccines were also tested intraperitoneally or orally.Maintenance of the mice on Freter's regimen proved a reliable method of rendering them susceptible to intestinal infection with streptomycin-resistant shigellae.Two killed vaccines conferred good protection against intracerebral challenge, but neither live nor killed vaccines administered intraperitoneally protected against oral infection of mice maintained on Freter's regimen. However, oral administration of live vaccine did confer significant protection against homologous oral challenge, the degree of protection depending on the dose of vaccine.