Rapid and complete adsorption of unconjugated protein from protein-polysaccharide conjugate vaccines

We have developed a rapid and inexpensive approach to remove unconjugated protein from protein-polysaccharide conjugate vaccines, without using gel filtration or ultrafiltration. We employ porous particles that adsorb the protein, whether bound or free, but with a pore size that allows only the unconjugated protein to enter the particle. Using limited amounts of media there is preferential binding of the unconjugated protein over the high molecular weight protein-polysaccharide conjugate. Adsorption of the unconjugated protein is rapid, with greater than 90% recovery of the conjugate. The approach is applicable to both neutral and charged polysaccharides and is not dependent on the chemistry used to make the conjugate vaccine. We have used this method to prepare tetanus toxoid-polysaccharide conjugates and found their immunogenicity in mice comparable to conjugates prepared using gel filtration. The method described can be used to reduce the cost and increase the yields of protein-polysaccharide conjugate vaccines.