Processes for the formulation of pneumococcal polysaccharides for conjugation to a carrier protein
The present invention provides a number of process improvements related to the conjugation of capsular polysaccharides from Streptococcus pneumoniae to a carrier protein. These process are serotype specific and include acid hydrolysis, addition of sodium chloride to the reductive amination reaction, and addition of sucrose to dissolve polysaccharides. Polysaccharide-protein conjugates prepared using the processes of the invention can be included in multivalent pneumococcal conjugate vaccines.
1. A method for lyophilizing a solution comprising activated S. pneumoniae polysaccharide, to generate a lyophilized material, wherein the activated S. pneumoniae polysaccharide is selected from serotype 3, 8 and 24F, the method comprising:
a) adding a monosaccharide or disaccharide sugar to the solution comprising activated S. pneumoniae polysaccharide to obtain a sugar:polysaccharide mass ratio of at least 30 and a solution with a suitable viscosity; and
b) lyophilizing the solution with a suitable viscosity comprising the activated S. pneumoniae polysaccharide, to obtain the lyophilized material;
wherein the lyophilized material is suitable for redissolution in solvent and use in conjugation reactions.
2. The method of claim 1 , wherein the sugar is mannitol, sucrose, trehalose or a combination thereof.
3. The method of claim 1 , wherein the sugar:polysaccharide mass ratio is at least 40 or at least 50.
4. The method of claim 1 , wherein the sugar concentration is greater than 5% w/v.
5. The method of claim 1 , wherein the solvent is an aprotic solvent.
6. The method of claim 5 , wherein the aprotic solvent is DMSO.