Purification of Capsular Polysaccharides of Streptococcus pneumoniae: Traditional and New Methods

Abstract

Pneumonia caused by Streptococcus pneumoniae is a major bacterial disease responsible for many deaths worldwide each year and is particularly dangerous in children under 5 years old and adults over 50. The capsular polysaccharide (CPS) constitutes the outermost layer of the bacterial cell and is the main virulence factor. Regardless of whether pharmaceutical agents are composed of CPS alone or protein-conjugated CPS, CPS purification is essential for the development of vaccines against S. pneumoniae. These vaccines are effective and safe but remain quite expensive. This review describes the methods currently available for CPS purification. Advances in CPS purification methods are aimed at improvements in quality and yield and, above all, process simplification.

Keywords: Streptococcus pneumoniae; capsular polysaccharides; ethanol precipitation; purification; vaccine.

Figure 1

Flow diagram for the CPS type-1 purification process proposed by Cano et al. (1979). The purification method includes ethanol precipitation, hexadecyltrimethylammonium bromide (Cetavlon) precipitation and purification by activated charcoal. The process removed more than 99% of contaminant protein, nucleic acid and C-carbohydrates while retaining the immunogenicity of the product.