Studies on the synthesis of peptide and glycerol phosphate oligomers in the cell walls of staphylococcus aureus

Abstract

Staphylococcus aureus is a gram-positive pathogen that induces skin, tissue infections, as well as life-threatening diseases such as endocarditis and bacteremia. The vaccines targeting S.aureus infections have been developed, but due to the emergence of resistant strains, such as Methicillin-resistant Staphylococcus aureus (MRSA), bacterial strains have become resistant to many antibiotics. Thus, there is an urgent need for a new vaccine that can prevent S.aureus infections, which is a world-wide problem. It has been revealed that cell wall components of wall teichoic acid and peptidoglycan conjugates induce $|gamma \delta$ T-cell that produces IL-17 which leads to bacterial clearance upon re-infection. The peptidoglycan layer of S.aureus cell wall comprises glycans and peptide, which is responsible for construction of rigid bacterial cell wall. Wall teichoic acid, which is a glycopolymer covalently linked to the peptidoglycan, consists of ribitol phosphate oligomer and glycerol phosphate linker. In this thesis, peptide and glycerol phosphate monomers were prepared. Ribitol phosphate oligomer in WTA, which needs to be achieved in a solution phase, requires 6-8 monomers to attain biological activity. Therefore, preparation of tetramer and octamer using glycerol monomers facilitated in establishing reaction conditions and ensured that growth of more complex ribitol monomer to certain chain length would be feasible in a solution phase, utilizing sensitive phosphoramidite chemistry. Also, the difficulty encountered in the analysis of naturally extracted bacterial components complicates the identification of structure of exact vaccine candidates. Thus, with different glycerol oligomers prepared, hydrogenated products were obtained. MALDI and NMR spectrometry were used in the confirmation of these products, which was a step towards the future analysis of much larger cell wall fragments of S.aureus.