Process for preparing pneumococcal polysaccharide-protein conjugates
An immunogenic composition having 13 distinct polysaccharide-protein conjugates and optionally, an aluminum-based adjuvant, is described. Each conjugate contains a capsular polysaccharide prepared from a different serotype of Streptococcus pneumoniae (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F) conjugated to a carrier protein. The immunogenic composition, formulated as a vaccine, increases coverage against pneumococcal disease in infants and young children globally, and provides coverage for serotypes 6A and 19A that is not dependent on the limitations of serogroup cross-protection.
1. A method for making an immunogenic conjugate comprising Streptococcus pneumoniae serotype 1 polysaccharide covalently linked to a CRM 197 carrier protein, the method comprising:
(a) reacting purified serotype 1 polysaccharide with sodium carbonate to yield hydrolyzed serotype 1 polysaccharide;
(b) reacting the hydrolyzed serotype 1 polysaccharide with an oxidizing agent, wherein the oxidizing agent is sodium periodate, to yield activated serotype 1 polysaccharide;
(c) compounding and co-lyophilizing the activated serotype 1 polysaccharide with a CRM 197 carrier protein;
(d) reacting the co-lyophilized, activated serotype 1 polysaccharide and CRM 197 carrier protein with sodium cyanoborohydride to yield serotype 1 polysaccharide:CRM 197 carrier protein conjugate; and
(e) capping unreacted aldehydes in the serotype 1 polysaccharide:CRM 197 carrier protein conjugate with sodium borohydride to yield an immunogenic conjugate comprising Streptococcus pneumoniae serotype 1 polysaccharide covalently linked to a CRM 197 carrier protein.
2. The method of claim 1 , further comprising purifying the immunogenic conjugate.
3. A method for making an activated Streptococcus pneumoniae serotype 1 polysaccharide, the method comprising:
(a) reacting purified serotype 1 polysaccharide with sodium carbonate to yield a hydrolyzed serotype 1 polysaccharide; and
(b) reacting the hydrolyzed serotype 1 polysaccharide with an oxidizing agent wherein the oxidizing agent is sodium periodate to yield activated serotype 1 polysaccharide.
4. The method of claim 3 , further comprising purifying the activated serotype 1 polysaccharide following oxidation.