title: In vivo evidence of immunological masking of the Vibrio cholerae O antigen of a hybrid Salmonella typhi Ty21a-Vibrio cholerae oral vaccine in humans.
abstract: The immunogenicity of the live oral hybrid vaccine organism Salmonella typhi Ty21a/V. cholerae Inaba (EX210) following its growth in media containing variable concentrations of supplemental galactose was examined in human volunteer subjects. The local intestinal IgA-specific antibody responses to both typhoid and cholera lipopolysaccharide (LPS) preparations were determined. It was observed that the immunogenicity of the galactose-independent Vibrio cholerae O antigen in vivo was dependent upon the variation in galactose-dependent long chain S. typhi O antigen production which was directly proportional to the media galactose concentration. It is likely that this observation was a result of steric hindrance of the presentation of the V. cholerae O antigen by S. typhi Ty21a in the presence of the longer, immunodominant S. typhi Ty21a O antigen. This observation may have relevance to the use of S. typhi vectors in vaccine development involving the presentation of LPS-associated heterologous antigens.
authors.affiliation: University of Adelaide Department of Medicine, Royal Adelaide Hospital, South Australia.
authors.forename: B D
authors.initials: BD
authors.lastname: Forrest
authors.forename: J T
authors.initials: JT
authors.lastname: LaBrooy
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000907:Antibodies, Bacterial / Q000096:biosynthesis; D000942:Antigens, Bacterial / Q000276:immunology*; D001428:Bacterial Vaccines / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000096:biosynthesis*; D007422:Intestines / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology; D008297:Male; D008875:Middle Aged; D019081:O Antigens; D012485:Salmonella typhi / Q000276:immunology*; D014614:Vaccines, Synthetic; D014734:Vibrio cholerae / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D007070:Immunoglobulin A; D008070:Lipopolysaccharides; D019081:O Antigens; D014614:Vaccines, Synthetic