Studies on virulence of Shigella flexneri. Protective effect of outer membrane proteins.

Groups of mice were immunized intraperitoneally with proteins isolated from outer membrane of virulent strain of Shigella flexneri 3a and its avirulent variant. All the animals were found to survive challenge with LD100 of virulent Sh. flexneri 3a. Similar protective effect against challenge with Sh. flexneri 3a gave also immunization of mice with outer membrane proteins isolated from Sh. flexneri of other serotypes (2a, 4a, 6, and X) and from Escherichia coli, Hafnia alvei and Shigella sonnei.