Quality, immunogenicity and stability of meningococcal serogroup ACWY-CRM₁₉₇, DT and TT glycoconjugate vaccines

A physicochemical and immunological study of the stability of three different meningococcal (Men) ACWY conjugate vaccines was performed to evaluate any patterns of serogroup oligo- or polysaccharide-specific or carrier protein-specific stability that would affect immunogenicity. Critical quality and stability-indicating characteristics were measured, with the study supporting the suitability of both HPLC-SEC and HPAEC-PAD methods to detect changes following inappropriate vaccine storage. All three final products, ACWY-CRM₁₉₇, -DT and -TT conjugate vaccines had expected quality indicator values and similar immunogenicity in a mouse model (anti-PS IgG and rSBA) when stored at +2-8°C. When stored at ≥+37°C, all conjugated carrier proteins and serogroup saccharides were affected. Direct correlations were observed between the depolymerization of the MenA saccharide as evidenced by a size-reduction in the MenA conjugates (CRM₁₉₇, DT and TT) and their immunogenicity. MenA was the most labile serogroup, followed by MenC; then MenW and Y, which were similar. At high temperatures, the conjugated carrier proteins were prone to unfolding and/or aggregation. The anti-MenC IgG responses of the multivalent conjugate vaccines in mice were equivalent to those observed in monovalent MenC conjugate vaccines, and were independent of the carrier protein. For any newly developing MenACWY saccharide-protein conjugate vaccines, a key recommendation would be to consider the lyophilization of final product to prevent deleterious degradation that would affect immunogenicity.