Next-Generation Whole-Cell Pneumococcal Vaccine.

Streptococcus pneumoniae remains a major public health hazard. Although Pneumococcal Conjugate Vaccines (PCVs) are available and have significantly reduced the rate of invasive pneumococcal diseases, there is still a need for new vaccines with unlimited serotype coverage, long-lasting protection, and lower cost to be developed. One of the most promising candidates is the Whole-Cell Pneumococcal Vaccine (WCV). The new generation of whole-cell vaccines is based on an unencapsulated serotype that allows the expression of many bacterial antigens at a lower cost than a recombinant vaccine. These vaccines have been extensively studied, are currently in human trial phase 1/2, and seem to be the best treatment choice for pneumococcal diseases, especially for developing countries.

Optimal Conditions for Streptococcus pneumoniae Culture: In Solid and Liquid Media.

Control of Streptococcus pneumoniae is mainly achieved by the use of existing vaccines. Capsular polysaccharides are the major antigenic component and are also the main virulence factor.Capsular polysaccharides must fulfill requirements of purity, uniformity, and an accurate molecular weight to be used as vaccine antigens. Vaccine production largely relies on cultivation of the pathogen in appropriate conditions.Here we describe widely used techniques to culture S. pneumoniae based on solid or complex liquid media, which are successfully applied in the diagnosis of the pathogen and in development and production of S. pneumoniae vaccines. Furthermore, we present a new chemically defined medium that can be used at lab scale.

Features of bacterial growth and polysaccharide production of Streptococcus pneumoniae serotype 14.

The effect of several cultivation conditions on the kinetics of bacterial growth and polysaccharide production of Streptococcus pneumoniae serotype 14 was studied. The presence in the supernatant of serotype-specific CPS (capsular polysaccharide) during growth was followed by size-exclusion HPLC and, in parallel, confirmed by using a specific latex reagent. The agitation level did not affect the production behaviour, whereas pH maintenance above 6 strongly enhanced both growth and CPS production throughout the cultivation period in flasks. Production of high-molecular-mass polysaccharide was found to be maximal between 5 and 6 h of cultivation, at the end of the exponential phase. By laser light scattering, 90% of this purified CPS product showed a M(w) (molecular mass) range from 350 to 1500 kDa, with an average M(w) of 921 kDa. Extending the culture to 24 h gave rise to a clear shift of the M(w) distribution of the polysaccharide to values lower than 100 kDa. These findings may have strong implications for the large-scale manufacture of the polysaccharide and the associated conjugate vaccine.