Quantitative determination of C-polysaccharide in Streptococcus pneumoniae capsular polysaccharides by enzyme-linked immunosorbent assay

Capsular polysaccharides of Streptococcus pneumoniae are used in pneumococcal polysaccharide and protein-conjugate vaccines. Cell-wall polysaccharide (C-Ps) is a critical impurity that must be kept at low levels in purified polysaccharide preparations. Hence, accurate and precise methods for determining C-Ps are needed. Currently available methods include nuclear magnetic resonance (NMR) spectroscopy and high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Both these methods suffer from their own limitations; therefore, we developed a simple and efficient enzyme-linked immunosorbent assay (ELISA) for accurate and precise quantification of C-Ps in samples of any serotype of pneumococcal capsular polysaccharide without interference. We quantified C-Ps in preparations of 14 serotype polysaccharides using newly developed ELISA method and compared the results with C-Ps values obtained using two previously reported methods,