S BITIITI ary
The gram negative, microaerophilic bacterium Helicobacter I~Iori colonizes the human gastric
mucosa and establishes a chronic infection that is tightly associated with atrophic gastritis, peptic
ulcer, and gastric carcinoma. Cloning of the H. pylori cytotoxin gene shows that the protein
is synthesized as a 140-kD precursor that is processed to a 94-kD fully active toxin. Oral
administration to mice of the purified 94-kD protein caused ulceration and gastric lesions that
bear some similarities to the pathology observed in humans. The cloning of the cytotoxin gene
and the development of a mouse model of human gastric disease will provide the basis for the
understanding of H. ~lori pathogenesis and the development of therapeutics and vaccines.