Atomic-Scale Description of Interfaces between Antigen and Aluminum-Based Adjuvants Used in Vaccines by Dynamic Nuclear Polarization (DNP) Enhanced NMR Spectroscopy

The addition of aluminum-based adjuvants in vaccines enhances the immune response to antigens. The strength of antigen adsorption on adjuvant gels is known to modulate vaccine efficacy. However, a detailed understanding of the mechanisms of interaction between aluminum gels and antigens is still missing. Herein, a new analytical approach based on dynamic nuclear polarization (DNP) enhanced NMR spectroscopy under magic angle spinning (MAS) is implemented to provide a molecular description of the antigen–adjuvant interface. This approach is demonstrated on hepatitis B surface antigen particles in combination with three aluminum gels obtained from different suppliers. Both noncovalent and covalent interactions between the phospholipids of the antigen particles and the surface of the aluminum gels are identified by using MAS DNP NMR ²⁷Al and ³¹P correlation experiments. Although covalent interactions were detected for only one of the formulations, dipolar recoupling rotational echo adiabatic passage double resonance (REAPDOR) experiments reveal significant differences in the strength of weak interactions.