A meningococcal vaccine antigen engineered to increase thermal stability and stabilize protective epitopes

Area of Science:

• Vaccinology
• Protein Engineering
• Microbial Pathogenesis

Background:

• Factor H binding protein (FHbp) is crucial in vaccines against serogroup B meningococcal disease.
• FHbp variants exhibit limited cross-reactivity and some have low thermal stability, impacting vaccine efficacy.
• Understanding FHbp stability is key to developing more effective vaccines.

Purpose of the Study:

• To engineer a more thermally stable Factor H binding protein (FHbp).
• To investigate the impact of specific amino acid substitutions on FHbp stability and antigenicity.
• To assess the potential of stabilized FHbp in enhancing vaccine-induced protective antibody responses.

Main Methods:

• Site-directed mutagenesis was used to alter amino acid residues R130 and D133 in FHbp.
• Protein thermal stability was assessed using differential scanning calorimetry.
• Crystal structure of the double mutant FHbp was determined to 1.6 Å resolution.
• Antibody binding affinity and Factor H binding were measured using surface plasmon resonance and flow cytometry.

Main Results:

• Specific amino acid substitutions (L130R and G133D) significantly increased FHbp N-terminal domain thermal stability (Tm increased by up to 21 °C).
• The stabilized FHbp mutant showed enhanced binding affinity for specific monoclonal antibodies.
• The stabilized mutant exhibited reduced binding to human complement Factor H, correlating with increased protective antibody responses.

Conclusions:

• Engineering FHbp stability through targeted amino acid substitutions is feasible.
• Stabilized FHbp variants demonstrate improved antigenicity and reduced immune evasion via Factor H binding.
• The stabilized FHbp mutant holds promise for enhancing the efficacy of current and future meningococcal vaccines.