Characterization of the capsular polysaccharide of Streptococcus pneumoniae serotype 18C by combining chromatographic methods and 1h NMR

Abstract

Streptococcus pneumonia (S. pneumoniae) is an encapsulated bacterium that can cause pneumonia, meningitis, and acute otitis media. The major incidence of the pneumococcal diseases occurs in children below five years old due to their immature immune system that do not respond adequately to polysaccharide antigens. Among the major incidence bacterial agents in Cuban infant population, S. pneumoniae is the only one that is not covered by a vaccine. For that reason, a project between the Center of Biomolecular Chemistry (CQB) and Finlay Institute for the production of a conjugate multivalent vaccine candidate is carried out and includes the serotypes: 1, 5, 6B, 14, 18C,19F, and 23F of S. pneumonia, coupled to carrier proteins such as tetanus or diphtheria toxoids. It is necessary to use
a combination of different analytical methods to evaluate capsular polysaccharides. In this work a characterization of
the serotype 18C of S. pneumoniae was done by the combination of Proton Nuclear Magnetic Resonance (1H NMR)
spectroscopy and chromatographic methods. The polysaccharide identity was confirmed by 1H NMR. The
stoichiometric monosaccharide composition was carried out by gas–liquid chromatography (GLC) and reversed phase
high resolution liquid chromatography (RP/HPLC) and matched to a previous report. The molecular weight
distribution of the polysaccharide was determined by high performance size exclusion chromatography (HPSEC). The
proposed methodology could be extended to the rest of the included serotypes in the vaccine.