Immune suppression induced by Vi capsular polysaccharide is overcome by Vi-DT conjugate vaccine

So Jung An, Yeon Kyung Yoon, Sudeep Kothari, Deok Ryun Kim, Jeong Ah Kim, Neha Kothari, Eugene Lee, Tai Hyun Park, Rodney Carbis

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The influence pre-exposure of mice to Vi capsular polysaccharide, purified from Salmonella enterica Serovar Typhi, on the subsequent immune response induced by a Vi-diphtheria toxoid (Vi-DT) conjugate was evaluated. Vi induced low anti Vi IgG titers with the dominant subclass being IgG3. The Vi-DT conjugate induced high titers of anti Vi IgG with the dominant subclass being IgG1 but with considerable quantities of IgG2a, IgG2b and IgG3. Priming of mice with Vi suppressed the response to a subsequent dose of conjugate and the suppression was overcome by a second dose of conjugate. Priming with conjugate prevented suppression of the anti Vi response and subsequent dosing with Vi raised titers back to previous levels but did not boost to new higher levels. The anti DT IgG response to one dose of conjugate was relatively strong and protracted and continued to rise for 12 weeks, compared to the response to one dose of DT which was poor and peaked at two weeks. The prolonged anti DT response was most likely due to the slow release of DT from the conjugate lattice as it degrades within the mouse resulting in a continuous stimulation of the immune response. The presence of increasing amounts of un-conjugated Vi, up to 50%, administered with the conjugate resulted in increasingly higher levels of both anti Vi and anti DT. Larger amounts of un-conjugated Vi inhibited the anti Vi response. These findings have implications for vaccine quality and a limit for un-conjugated polysaccharide should not exceed 50% and from a vaccine program perspective if the results presented here translate to humans then a Vi conjugate, once it becomes available, should replace Vi polysaccharide vaccines.

Original languageEnglish
Pages (from-to)1023-1028
Number of pages6
Issue number6
StatePublished - 1 Feb 2012

Bibliographical note

Funding Information:
This work was supported by grants from the Bill and Melinda Gates Foundation , UBS Optimus Foundation and from the governments of the Republic of Korea and Sweden (SIDA) .


  • Conjugate vaccine
  • Diphtheria toxoid
  • Hyporesponsiveness
  • Vi polysaccharide


Dive into the research topics of 'Immune suppression induced by Vi capsular polysaccharide is overcome by Vi-DT conjugate vaccine'. Together they form a unique fingerprint.

Cite this