MOLECULAR CHARACTERIZATION OF THE O-ACETYL TRANSFERASE GENE OF CONVERTING BACTERIOPHAGE SF6 THAT ADDS GROUP ANTIGEN-6 TO SHIGELLA-FLEXNERI

Bacteriophage SF6 antigenically converts Shigella flexneri serotype Y strains (-;3,4) to type 3b carrying group antigen 6,3,4 by means of an O-acetylation of the O-antigenic polysaccharide chain. The gene for O-acetyl transferase of bacteriophage SF6 has been cloned, identified and sequenced. The predicted O-acetyl transferase protein encoded by this gene was found to consist of 333 amino acids, (37 185 daltons) and to have some similarity with the galactose-1-phosphate uridylytransferase protein of Escherichia coli. The gene has been shown to function in a live vaccine strain of S. flexneri Y type (DELTA-aroD), making it a 3b type. The converted type 3b strain, SFL1104, was found to elicit significant protection against challenge by both wild-type serotypes 3b and Y in a guinea-pig keratoconjunctivitis model.