Analytical Characterization of Pneumococcal Vaccine Conjugates Using SEC-MALS Technique

Background/Objectives: Infection from Streptococcus pneumoniae can lead to serious complications, such as meningitis and pneumonia, in children under 2 years of age, older adults, and immunocompromised populations. Conjugate vaccines against the pathogen have been licensed for the prevention of invasive pneumococcal disease. Conjugate vaccine development is an involved process demanding extensive characterization of both the polysaccharide (PS) and protein (Pr) moieties in complex structures. One powerful tool in our analytical tool kit that can shed light on various analytical attributes of conjugate vaccines, such as molecular weight and composition and conjugation efficiency, is the size-exclusion chromatography-multi-angle light scattering detector (SEC-MALS) technique. Herein, we demonstrate the applicability of the SEC-MALS approach for pneumococcal conjugate vaccine product characterization. Methods: Capsular polysaccharides for serotypes (STs) 1, 3, 5, 10 A, 18 C, 24 F, and 33 F conjugated to rCRM197 carrier protein were chosen for this study. Results: The technique was very straightforward, with a high degree of accuracy (>90% based on standards) and repeatability (<2% RSD) for conjugate molar mass measurements. In addition, leveraging the capability of SEC-MALS for compositional analysis, we were able to get detailed information on the molecular assembly and conformation of the conjugates and further tweak the conjugation process to yield conjugates of a desired molar mass. Conclusions: Thus, this study highlights the usefulness of the SEC-MALS technique for in-depth conjugate vaccine biophysical characterization, which is critical for achieving optimal product attributes, driving manufacturing consistency and vaccine potency.