Use and validation of NMR assays for the identity and O-acetyl content of capsular polysaccharides from Neisseria meningitidis used in vaccine manufacture.

We describe a validated NMR (nuclear magnetic resonance) spectroscopic assay for the identity of the capsular polysaccharides (CPSs) from Neisseria meningitidis Groups A, C, W135 and Y used in vaccine manufacture, and to determine the proportion of residues carrying an O-acetyl substituent. Proof of structural identity and quantitation of the O-acetyl content are key control parameters for these vaccines. The meningococcal CPSs have variable levels of O-acetylation, present at multiple sites in the repeat unit, leading to complex NMR spectra. Base-catalysed de-O-acetylation of the Groups A, C, W135 and Y CPSs yields simplified and reproducible spectra suitable for comparison with reference data. The degree of O-acetylation of the original CPS can be determined by integration of the acetate anion resonance and a suitable resonance from the saccharide moiety. The assay was validated using 46 independent samples from five manufacturers, and is shown to be robust and reproducible.