Molecular Cloning and Characterization of Genes for Shigella sonnei Form I O Polysaccharide: Proposed Biosynthetic Pathway and Stable Expression in a Live Salmonella Vaccine Vector

摘要: The gene region for biosynthesis of Shigella sonnei form I O polysaccharide (O-Ps) and flanking sequences, totaling >18 kb, was characterized by deletion analysis to define a minimal construct development Salmonella-based live vaccine vector strains. Lipopolysaccharide (LPS) expression DNA sequence studies plasmid derivatives indicated O-Ps from 12.3-kb containing putative promoter 10 contiguous open reading frames (ORFs), one which is the transposase IS630. A detailed biosynthetic pathway, consistent with predicted functions eight nine essential ORFs structure, proposed. Further sequencing identified partial IS elements (i.e., IS91 IS630) wzz upstream coding fragment aqpZ additional full or IS629, IS91, IS911) downstream this region. stability plasmid-based greater low-copy vectors than high-copy enhanced inserts. Both core-linked LPS) non-core-linked capsule-like) surface were detected Western blotting silver staining polyacrylamide gel electrophoresis-separated Escherichia coli extracts. However, salmonellae, have core that chemically dissimilar shigellae, expressed only surface-associated O-Ps. Finally, attenuated Salmonella enterica serovar Typhi candidates, minimal-sized operon constructs, elicited immune protection in mice against virulent S. challenge, thereby supporting promise live, oral vaccines prevention shigellosis.