Transformed shigella.

摘要

A method for modifying a wild strain of an entero-invasive Shigella to produce a modified strain of Shigella that can be used for making a vaccine against the wild strain. The genome of the wild strain is transformed by deleting all or a substantial part of: a) both its ompR and envZ genes; or b) its ompF gene. This renders the strain substantially less invasive. One or more additional genes of the wild strain, such as the icsA gene, are also deleted in whole or in part so that the so-modified strain is sufficiently non-invasive to be safe for use in a vaccine but sufficiently active to provide protection against the wild strain.