Capsular polysaccharide solubilisation and combination vaccines
Precipitated bacterial capsular polysaccharides can be efficiently re-solubilised using alcohols as solvents. The invention provides a process for purifying a bacterial capsular polysaccharide, comprising the steps of (a) precipitation of said polysaccharide, followed by (b) solubilisation of the precipitated polysaccharide using ethanol. CTAB can be used for step (a). The material obtained, preferably following hydrolysis and sizing, can be conjugated to a carrier protein and formulated as a vaccine. Also, in vaccines comprising saccharides from both serogroups A and C, the invention provides that the ratio (w/w) of MenA saccharide: MenC saccharide is >1.
1. A process for conjugating a bacterial capsular polysaccharide to a carrier protein, comprising:
purifying the polysaccharide, comprising the steps of (a) precipitation of the polysaccharide using one or more cationic detergents, followed by (b) solubilisation of the precipitated polysaccharide using an alcohol, then (c) treating the polysaccharide obtained in step (b) to remove contaminants, wherein step (c) comprises one or more steps of filtration, and conjugating the polysaccharide to a carrier protein,
wherein the bacterial capsular polysaccharide is from Neisseria meningitidis serogroup A, W135 or Y, or from Haemophilus influenzae , or from Streptococcus pneumoniae and wherein the process does not comprise precipitating the polysaccharide on an inert porous support using one or more cationic detergents.
2. A process for conjugating a bacterial capsular polysaccharide to a carrier protein, comprising:
purifying the polysaccharide, comprising the steps of (a) precipitation of the polysaccharide using one or more cationic detergents, followed by (b) solubilisation of the precipitated polysaccharide using an alcohol,
conjugating the polysaccharide to a carrier protein, and
mixing with capsular saccharide from Neisseria meningitidis to produce a mixture comprising capsular saccharides from Neisseria meningitidis serogroup Y (MenY) and one or both of Neisseria meningitidis serogroups C (MenC) and W135 (MenW135) provide a mixture with a ratio (w/w) of MenY saccharide:MenW135 saccharide greater than 1 and/or a ratio (w/w) of MenY saccharide:MenC saccharide less than 1,
wherein the bacterial capsular polysaccharide is from Neisseria meningitidis , or from Haemophilus influenzae , or from Streptococcus pneumoniae and wherein the process does not comprise precipitating the polysaccharide on an inert porous support using one or more cationic detergents.
3. The process of claim 1 or claim 2 , wherein the cationic detergent(s) comprise a cetyltrimethylammonium salt, a tetrabutylammonium salt, a myristyltrimethylammonium salt and/or hexadimethrine bromide.
4. The process of claim 1 or claim 2 , wherein the alcohol used in step (b) comprises ethanol, and wherein the ethanol has a final concentration of between 50% and 95%.
5. The process of claim 1 , wherein step (c) comprises depth filtration, filtration through activated carbon, size filtration and/or ultrafiltration.
6. The process of claim 1 , wherein the polysaccharide obtained in step (b) or step (c) is then precipitated.
7. The process of claim 2 , wherein the polysaccharide obtained in step (b) is then precipitated.
8. The process of claim 6 , wherein precipitation is by addition of calcium or sodium salts.
9. The process of claim 7 , wherein precipitation is by addition of calcium or sodium salts.
10. The process of claim 1 or claim 2 , wherein the saccharide is activated prior to conjugation.
11. The process of claim 10 , wherein activation involves a cyanylating reagent.
12. The process of claim 1 or claim 2 , wherein the conjugated saccharide has a saccharide:protein ratio (w/w) between 0.5:1 and 5:1.
13. The process of claim 1 or claim 2 , wherein the carrier protein is diphtheria toxoid or tetanus toxoid.
14. The process of claim 1 or claim 2 , wherein, after conjugation, free and conjugated saccharides are separated.
15. The process of claim 14 , wherein separation uses hydrophobic chromatography, tangential ultrafiltration, or diafiltration.
16. The process claim 1 , further comprising a step of mixing the conjugate with other biological molecules to give a mixture of saccharides from more than one serogroup of N. meningitidis .
17. The process of claim 16 , wherein mixing gives a composition comprising a mixture of saccharides from more than one serogroup of N. meningitidis , and wherein the composition comprises saccharides from serogroups A+C, A+W135, A+Y, C+W135, C+Y, W135+Y, A+C+W135, A+C+Y, C+W135+Y or A+C+W135+Y.
18. The process of claim 17 , wherein the composition comprises capsular saccharides from both serogroups A and C and the ratio (w/w) of MenA saccharide:MenC saccharide is 2:1.
19. The process of claim 17 , wherein the composition comprises capsular saccharides from serogroup Y and one or both of serogroups C and W135, and wherein the ratio (w/w) of MenY saccharide:MenW135 saccharide is greater than 1 and/or that the ratio (w/w) of MenY saccharide:MenC saccharide is less than 1.
20. The process of claim 17 , wherein the composition comprises capsular saccharides from serogroups A, C, W135 and Y, and wherein serogroups A:C:W135:Y have ratios (w/w) of 1:1:1:1; 1:1:1:2; 2:1:1:1; 4:2:1:1; 8:4:2:1; 4:2:1:2; 8:4:1:2; 4:2:2:1; 2:2:1:1; 4:4:2:1; 2:2:1:2; 4:4:1:2; or 2:2:2:1.
21. The process of claim 1 or claim 2 , further comprising step(s) of vaccine formulation comprising mixing the saccharide antigen(s) with an adjuvant which is an aluminium phosphate and/or an aluminium hydroxide.