Evaluation of the Immunogenicity and Biological Activity of the Citrobacter freundii Vi-CRM 197 Conjugate as a Vaccine for Salmonella enterica Serovar Typhi
Open Access
- 1 March 2011
- journal article
- Published by American Society for Microbiology in Clinical and Vaccine Immunology
- Vol. 18 (3), 460-468
- https://doi.org/10.1128/cvi.00387-10
Abstract
Typhoid fever remains a major health problem in developing countries. Young children are at high risk, and a vaccine effective for this age group is urgently needed. Purified capsular polysaccharide from Salmonella enterica serovar Typhi (Vi) is licensed as a vaccine, providing 50 to 70% protection in individuals older than 5 years. However, this vaccine is ineffective in infants. Vi conjugated to a carrier protein (i.e., an exoprotein A mutant from Pseudomonas aeruginosa [rEPA]) is highly immunogenic, provides long-term protection, and shows more than 90% protective efficacy in children 2 to 5 years old. Here, we describe an alternative glycoconjugate vaccine for S . Typhi, Vi-CRM 197 , where Vi was obtained from Citrobacter freundii WR7011 and CRM 197 , the mutant diphtheria toxin protein, was used as the carrier. We investigated the optimization of growth conditions for Vi production from C. freundii WR7011 and the immunogenicity of Vi-CRM 197 conjugates in mice. The optimal saccharide/protein ratio of the glycoconjugates was identified for the best antibody production. We also demonstrated the ability of this new vaccine to protect mice against challenge with Vi-positive Salmonella enterica serovar Typhimurium.Keywords
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