title: Cross-reactive immune response induced by the Vi capsular polysaccharide typhoid vaccine against Salmonella Paratyphi strains.
abstract: There are no vaccines in clinical use against paratyphoid fever, caused by Salmonella Paratyphi A and B or, rarely, C. Oral Salmonella Typhi Ty21a typhoid vaccine elicits a significant cross-reactive immune response against S. Paratyphi A and B, and some reports suggest cross-protective efficacy against the disease. These findings are ascribed to the O-12 antigen shared between the strains. The Vi capsular polysaccharide vaccine has been shown to elicit antibodies reactive with O-9,12. Twenty-five volunteers immunized with the parenteral Vi vaccine (Typherix(®) ) were explored for plasmablasts cross-reactive with paratyphoid strains; the responses were compared to those in 25 age- and gender-matched volunteers immunized with Ty21a (Vivotif(®) ). Before vaccination, 48/50 vaccinees had no plasmablasts reactive with the antigens. Seven days after vaccination, 15/25 and 22/25 Vi- and Ty21a-vaccinated volunteers had circulating plasmablasts producing antibodies cross-reactive with S. Paratyphi A, 18/25 and 23/25 with S. Paratyphi B and 16/25 and 9/25 with Paratyphi C, respectively. Compared to the Ty21a group, the Vi group showed significantly lower responses to S. Paratyphi A and B and higher to S. Paratyphi C. To conclude, the Vi vaccine elicited a cross-reactive plasmablast response to S. Paratyphi C (Vi antigen in common) and less marked responses to S. Paratyphi A and B than the Ty21a preparation. S. Paratyphi A and B both being Vi-negative, the result can be explained by trace amounts of bacterial cell wall O-12 antigen in the Vi preparation, despite purification. The clinical significance of this finding remains to be determined.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland; Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: S H
authors.initials: SH
authors.lastname: Pakkanen
authors.forename: J M
authors.initials: JM
authors.lastname: Kantele
authors.forename: A
authors.initials: A
authors.lastname: Kantele
mesh_terms: D000328:Adult; D000907:Antibodies, Bacterial / Q000276:immunology; D003429:Cross Reactions / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019081:O Antigens / Q000276:immunology; D010284:Paratyphoid Fever / Q000276:immunology / Q000517:prevention & control; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D012482:Salmonella paratyphi A / Q000276:immunology*; D012484:Salmonella paratyphi B / Q000276:immunology*; D012479:Salmonella paratyphi C / Q000276:immunology*; D014436:Typhoid-Paratyphoid Vaccines / Q000276:immunology*; D014611:Vaccination; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D019081:O Antigens; D011135:Polysaccharides, Bacterial; C072772:Ty21a typhoid vaccine; D014436:Typhoid-Paratyphoid Vaccines; C054154:capsular polysaccharide, Salmonella