A polysaccharide of Alloiococcus otitidis, a new pathogen of otitis media: chemical structure and synthesis of a neoglycoconjugate thereof

作者：Arar Sharif; Vinogradov Evguenil; Shewmaker P Lynn; Monteiro Mario A^*

来源：Carbohydrate Research, 2008, 343(6): 1079-1090.

DOI：10.1016/j.carres.2007.12.007

• Alloiococcus otitidis
• otitis media
• capsule polysaccharicle
• neoglycoconjugate
• glutamic acid
• structural characterization

Alloiococcus otitidis is a recently discovered Gram-positive bacterium that has been linked with otitis media (middle ear infections). In this study, we describe the structure of a novel capsular polysaccharide (PS) expressed by the type-strain of A. otitidis, ATCC 51267, and the synthesis of a glycoconjugate composed of the capsule PS and bovine serum albumin (BSA). The capsule PS of A. otitidis type-strain was determined to be a repeating trisaccharide composed of 3-substituted N-acetyl-D-glucosamine (GlcpNAc), 6-substituted N-acetyl-D-galactosamine (GalpNAc), and 4-substituted D-glucuronic acid (GlcpA), of which the majority was amidically decorated with L-glutamic acid (Glu):{-> 6})-beta-Ga1pNAc-(1 -> 4)-[Glup-6]-beta-GlcpA-(1 -> 3)-beta-GlcpNAc-(1}(n). Monomeric analysis performed on other A. otitidis strains revealed that similar components were variably expressed, but Glu appeared to be a regular constituent in all the strains examined. Due to the suitable presence of GlcpA and Glu, our approach for glycoconjugate synthesis employed a carbodiimide-based strategy with activation of available carboxyl groups by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), which afforded direct coupling between the capsule PS and BSA. Analysis by mass spectrometry indicated that this A. otitidis capsule PS-BSA conjugate was composed of BSA units that carried up to seven capsule PSs. This work represents the first report in the literature describing an A. otitidis cell-surface carbohydrate and the synthesis of a glycoconjugate preparation thereof. Presently, we are formulating plans to immunologically evaluate this A. otitidis glycoconjugate vaccine in animals.

• 出版日期2008-5-5