Capsular polysaccharide solubilisation and combination vaccines
Precipitated bacterial capsular polysaccharides can be efficiently re-solubilized 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) solubilization 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 saccharide to a carrier protein, comprising:
purifying the saccharide, comprising the steps of (a) precipitation of the saccharide using one or more cationic detergents, followed by (b) solubilisation of the precipitated saccharide using ethanol at a final concentration of between 75% and 95%,
conjugating the saccharide to a carrier protein, wherein the carrier protein is a bacterial toxin or toxoid, and wherein the conjugated saccharide has a saccharide:protein ratio (w/w) between 0.5:1 and 5:1,
mixing the conjugated saccharide with a second bacterial capsular saccharide conjugated to a second carrier protein, wherein the second carrier protein is the bacterial toxin or toxoid,
wherein the bacterial capsular saccharide is from Neisseria meningitidis serogroup A, W135 or Y, or from Haemophilus influenzae , or from Streptococcus pneumoniae.
2. A process for conjugating a bacterial capsular saccharide to a carrier protein, comprising:
purifying the saccharide, comprising the steps of (a) precipitation of the saccharide using one or more cationic detergents, followed by (b) solubilisation of the precipitated saccharide using ethanol at a final concentration of between 75% and 95%,
activating the saccharide with a cyanylating reagent, and
conjugating the saccharide to a carrier protein, wherein the carrier protein is a bacterial toxin or toxoid,
mixing the conjugated saccharide with a second bacterial capsular saccharide conjugated to a second carrier protein, wherein the second carrier protein is the bacterial toxin or toxoid,
wherein the bacterial capsular saccharide is from Neisseria meningitidis serogroup A, W135 or Y, or from Haemophilus influenzae , or from Streptococcus pneumoniae.
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 saccharide obtained in step (b) is then precipitated.
5. The process of claim 4 , wherein precipitation is by addition of calcium or sodium salts.
6. The process of claim 1 or claim 2 , wherein the carrier protein is diphtheria toxoid or tetanus toxoid.
7. The process of claim 1 or claim 2 , wherein, after conjugation, free and conjugated saccharides are separated.
8. The process of claim 7 , wherein separation uses hydrophobic chromatography, tangential ultrafiltration, or diafiltration.
9. The process of claim 1 or claim 2 , wherein the step of mixing the conjugated saccharide with the second bacterial capsular saccharide conjugated to a second carrier protein gives a mixture of saccharides from more than one serogroup of N. meningitidis.
10. The process of claim 9 , wherein saccharide antigens from N. meningitidis strains A, C, W135 and/or Y are mixed.
11. The process of claim 10 , wherein mixing gives a composition comprising capsular saccharides from both serogroups A and C and the ratio (w/w) of MenA saccharide:MenC saccharide is 2:1.
12. The process of claim 10 , wherein mixing gives a composition comprising 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.
13. The process of claim 10 , wherein mixing gives a composition comprising 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.
14. 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.