Spectroscopic characterisation of a series of Salmonella Typhi Vi-diphtheria toxoid glycoconjugate antigens differing in polysaccharide-protein ratio

March 24, 2020

Title

Spectroscopic characterisation of a series of Salmonella Typhi Vi-diphtheria toxoid glycoconjugate antigens differing in polysaccharide-protein ratio

Author

Christopher Jones, So Jung An, Yeon Kyung Yoon, Sudeep Kothari, Sushant Sahastrabuddhe, Rodney Carbis

Year

2020

Journal

Journal of Pharmaceutical and Biomedical Analysis

Abstract

Glycoconjugate vaccines consisting of the Salmonella enterica subsp. enterica serovar Typhi (S. Typhi) Vi capsular polysaccharide (PS) covalently attached to a suitable carrier protein have become available to support mass paediatric vaccination campaigns against typhoid. One developmental vaccine from the International Vaccine Institute (IVI) uses diphtheria toxoid (DTx) as the carrier protein. Several investigational conjugates with different PS:protein ratios were prepared, as previously reported by the IVI group, for physicochemical and immunochemical characterisation. We describe here the further spectroscopic characterisation of this series of glycoconjugate immunogen bulks using NMR spectroscopy, circular dichroism and absorption spectroscopy. We have used several mathematical approaches to extract information from the spectroscopic data not previously applied to glycoconjugates. These complementary approaches provide information on (i) the integrity of the carrier protein, (ii) consistency between batches of vaccine components, (iii) the polysaccharide: protein ratio (iv) the O-acetylation of the Vi in the conjugate (v) the stability of the O-acetylation of the Vi, and (vi) the presence of residual process reagents in the bulk. The utility of the data analysis approaches is discussed. Together, these analytical methods provide important characterisation of Vi-DTx conjugates to support development and quality control of commercial products.

Instrument

J-720

Keywords

Circular dichroism, Secondary structure, Chemical stability, Tertiary structure, Kinetics, Biochemistry, Pharmaceutical