title: Immunological evaluation of Vi capsular polysaccharide of Salmonella enterica subsp. Typhi vaccine by serum bactericidal assay.
abstract: Salmonella enterica subsp. Typhi (S. Typhi) Vi antigen capsular polysaccharide (Vi-CPS) is a licensed vaccine against typhoid fever. As there is no animal model for S. Typhi fever to evaluate the protective efficacy of the Vi-CPS vaccine, a serum bactericidal assay (SBA) is the recommended 'gold standard' to evaluate its potency. Vi-CPS was extracted from S. Typhi Ty6S (CSBPI-B191) using a modified Gotschlich method. Purified Vi-CPS (50 µg) was injected intramuscularly into three groups of five rabbits; group 2 received an additional booster dose of 50 µg Vi-CPS on day 15 and group 3 received two additional boosters on days 15 and 30. The sera obtained from each group were tested by SBA on days 0, 15, 30 and 45. The anti-Vi-CPS titres for groups 1, 2 and 3 on days 15, 30 and 45 were 4, 16 and 16; 4, 32 and 32; and 16, 64 and 64, respectively. Thus, Vi-CPS was shown to be a potent immunogen, as even one dose could induce an efficient bactericidal effect against S. Typhi. Although Vi-CPS is a reliable vaccine, sometimes depolymerization during purification can affect its potency, which can be resolved through a potency test. As the passive haemagglutination test recommended by the World Health Organization does not indicate vaccine potency, we recommend using an SBA to evaluate the bactericidal ability of Vi-CPS.
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: H
authors.initials: H
authors.lastname: Ahmadi
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: B
authors.initials: B
authors.lastname: Tabaraie
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: S
authors.initials: S
authors.lastname: Maleknia
authors.affiliation: Department of Microbiology, Islamic Azad University of Zanjan, Zanjan, Iran.
authors.forename: R
authors.initials: R
authors.lastname: Shapouri
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Nejati
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: F
authors.initials: F
authors.lastname: Pour Mirza Gholi
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Hedayati
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Sadati
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: S
authors.initials: S
authors.lastname: Zahednia
authors.affiliation: Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: A
authors.initials: A
authors.lastname: Sharifat Salmani
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood* / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D011817:Rabbits; D012485:Salmonella typhi / Q000276:immunology*; D058248:Serum Bactericidal Antibody Assay; D014435:Typhoid Fever / Q000276:immunology / Q000517:prevention & control; D014436:Typhoid-Paratyphoid Vaccines / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D011135:Polysaccharides, Bacterial; D014436:Typhoid-Paratyphoid Vaccines; C057664:Vi polysaccharide vaccine, typhoid; C054154:capsular polysaccharide, Salmonella