Enzyme-linked immunosorbent assay for quantitative determination of capsular polysaccharide production in Streptococcus pneumoniae clinical isolates.
ABSTRACT A simple, specific, sensitive and reproducible ELISA has been developed to quantify the level of CPS (capsular polysaccharide) production in supernatants of Streptococcus pneumoniae cell cultures. CPSs from Strep. pneumoniae have been widely used as vaccine antigens. The quantification method is based on two type-23F serotype-specific polyclonal antibodies: IgG, purified from sera of mice immunized with a pneumococcal type-23F CPS conjugate, used in the coating step, and a serotype-specific rabbit serum as the second antibody. Solutions of purified type-23F CPS were used as standards. The relationship between A(492) and type-23F CPS concentration was linear over the range 1-310 ng/ml (r=0.989), with 1 ng/ml as the lower limit of sensitivity. The specificity of ELISA was assessed because purified type-19F CPS and cell-wall polysaccharide samples were not detected after their evaluation by the ELISA described in the present study. Repeatability and intermediate precision of the assay were good, the coefficients of variation being 3 and 10% respectively. This ELISA allowed selection of an appropriate vaccine strain, for a natural polysaccharide vaccine, among several 23F pneumococcal clinical isolates and constituted a valuable analytical tool for Strep. pneumoniae fermentation and CPS purification follow-up.
- SourceAvailable from: Maria Antonieta P GimenesElectronic Journal of Biotechnology 09/2011; 14(5):6-6. · 0.65 Impact Factor
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ABSTRACT: The increasing requirement for multivalent vaccines containing diverse capsular polysaccharides has created an unmet need for a fast and straightforward assay for polysaccharide titer. We describe a novel and robust assay for the quantitation of anionic capsular polysaccharides. The binding of hexadecyltrimethyammonium bromide (Hb) to anionic capsular polysaccharides results in a precipitation reaction wherein the suspension turbidity is proportional to polysaccharide titer. The turbidity can be quickly measured as absorbance across a range of wavelengths that resolve scattering light. Carbohydrates comprised of repeating units of one to seven monosaccharides with phosphodiester groups, uronic acids, and sialic acids all reacted strongly and there does not appear to be specificity with respect to the particular anionic moiety. The assay is compatible with an array of common buffers across a pH range of 3.0-8.75 and with NaCl concentration exceeding 400mM. Interference from DNA can be eliminated with a short incubation step with DNase. With these treatments, the assay has been employed in samples as complex as fermentation broth. A two-log dynamic range has been established with a mean relative standard deviation less than 10% across this range although inferior performance has been observed in fermentation broth. The precipitation assay enables the rapid quantitation of anionic polysaccharides. The resulting procedure can robustly measure the titer of myriad anionic capsular polysaccharides (CPS) in 96 samples in less than 30min using low toxicity reagents and routine laboratory equipment. This development will greatly reduce the effort required to measure polysaccharide titer and yield during process development of polysaccharide vaccines.Vaccine 10/2013; · 3.49 Impact Factor
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ABSTRACT: Streptococcus pneumoniae is a major cause of mortality in underdeveloped countries, where more than one million people die from pneumococcal disease every year. Vaccines are the most efficient method for preventing the infection and are based on the capsular polysaccharide (PS) protection. The serotype 14 is the most frequent in pediatric infections worldwide. This study aimed to establish a quantification protocol for PS present in culture broth samples of S. pneumoniae serotype 14 (PS14) and use this protocol for selection of the best PS14 producer strain. Phenol-sulfuric, HPSEC, competitive ELISA, and sandwich ELISA methods were tested for PS14 quantification. Sandwich ELISA was the method with the best reproducibility and sensitivity and the least susceptible to interferences. The quantification limit and detection limit of this method were 0.99 and 0.57 ng/mL, respectively. Statistical analysis was performed to calculate the coefficient of variation (CV) intraassay (1-3% intraplate and 2-6% interplate) and interassay (11-15%) and the reproducibility in different days (CV<20%). The sandwich ELISA allows us to select, among six strains evaluated, the strain 5287 as the best PS14 producer (11.68 mg PS14/biomass) and it was shown to be the best choice for measurement of pneumococcal polysaccharides in culture broth samples.Analytical Biochemistry 12/2011; 421(1):250-5. · 2.31 Impact Factor