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Dodi Safari

Tuesday 30 November 2010

Development of new synthetic oligosaccharide vaccines.

Promotor: Prof.dr J. Verhoef & prof.dr J.P. Kamerling
Defence: 30 November 2010
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Summary
S. pneumoniae is a leading cause of bacterial pneumonia, meningitis, and sepsis in children worldwide. The development of effective vaccine is an important strategy to reduce morbidity and mortality caused by S. pneumoniae infection (Chapter 1). In this thesis, we focus on the immunogenicity of a series of synthetic overlapping oligosaccharide fragments corresponding to S. pneumoniae type 14 polysaccharide (Pn14PS) were conjugated to CRM197 protein (neoglycoconjugate) in mice model (Chapter 2). We identified that the branched trisaccharide element Glc-(Gal-)GlcNAc is essential in inducing Pn14PS-specific antibodies and that the neighboring galactose unit at the non-reducing end contributes clearly to the immunogenicity of the epitope. The sera obtained from those neoglycoconjugates of Pn14PS immunization did not cross-react with different S. pneumoniae polysaccharides (Appendix 1) and very low binding with group B streptococcus type III polysaccharide (Chapter 5). We revealed that a neoglycoconjugate boosting is responsible for the activation of memory cells and the establishment of sustained immunity. A boost with native polysaccharide is not only ineffective to evoke opsonic antibodies (Chapter 3). We observed that codelivery of Quil-A alone or in combination with MPL had the most dramatic effect on antibody- and cell-mediated immune response to neoglycoconjugate of Pn14PS (Chapter 4). From this studies, we proposed that the branched tetrasaccharide Gal-Glc-(Gal-)GlcNAc may be a serious candidate for a synthetic oligosaccharide conjugate vaccine against infections caused by S. pneumoniae type 14.

The synthetic branched tetrasaccharide was applied for the synthesis of hybrid gold nanoparticles [GNPs] (Chapter 6). Gold nanoclusters coated with different amounts of tetrasaccharide, the OVA323-339-peptide fragment, and the monosaccharide D-glucose. We found that the presence of the T-cell stimulating peptide OVA323-339 in the hybrid gold nanoparticles was a prerequisite for the induction of specific anti-Pn14PS IgG antibodies in mice model. We showed that well designed hybrid gold nanoparticles display a promising platform towards the development of synthetic oligosaccharide-based vaccines.

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