Send to:

Choose Destination
See comment in PubMed Commons below
J Med Microbiol. 2013 Feb;62(Pt 2):283-6. doi: 10.1099/jmm.0.047159-0. Epub 2012 Oct 25.

Immunological evaluation of Vi capsular polysaccharide of Salmonella enterica subsp. Typhi vaccine by serum bactericidal assay.

Author information

  • 1Department of Bacterial Vaccines & Antigens Production, Pasteur Institute of Iran, Tehran, Iran.


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.

[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Ingenta plc
    Loading ...
    Write to the Help Desk