Stabilizing Meningococcal fHbp Polypeptides via Residue Mutations
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Solution Overview
Problem
Current meningococcal vaccines, particularly those targeting serogroup B, face challenges in inter-variant cross-reactivity and stability issues with the fHbp protein, leading to limited protection against different strains and instability of the v2 variant.
Innovation Solution
Development of mutant fHbp polypeptides with specific amino acid sequence modifications, such as changes at residues 123, 240, and 32, to enhance stability and reduce binding to human factor H, while maintaining immunogenicity and bactericidal activity across variants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fHbp sequence is engineered to contain specificities for all three variants to increase inter-family cross-reactivity, then cross-protection against different variants is improved, but the stability of v2 polypeptides deteriorates due to inherent instability in the N-terminal β-barrel domain
Solution Approach 1:
The patent applies parameter changes by modifying specific amino acid residues (L123, E240, and S32) in the fHbp v2 sequence to alter the physical-chemical properties of the protein. These substitutions change the local structure and interactions in the N-terminal β-barrel domain, thereby improving stability without compromising cross-reactivity. This directly addresses the contradiction by tuning molecular parameters to achieve both goals simultaneously.
Solution Approach 2:
The invention applies local quality by making targeted substitutions at specific positions (residues 32, 123, and 240) rather than modifying the entire sequence. The mutations L123R/E240A and S32V are introduced locally to stabilize the N-terminal domain while preserving the overall structure and function required for cross-variant recognition. This localized approach allows improvement of stability without affecting the global adaptability of the protein.
2Stability of the object's composition
If mutations are introduced to improve stability of v2 sequences, then polypeptide stability is improved, but inter-variant cross-reactivity may deteriorate due to potential disruption of antigenic epitopes
Solution Approach 1:
The patent uses parameter changes by carefully selecting amino acid substitutions that improve stability while preserving antigenic properties. The specific mutations (L123R, E240A, S32V) were chosen to stabilize the N-terminal domain without disrupting the C-terminal domain epitopes that are critical for cross-variant recognition. This selective parameter modification resolves the contradiction between stability and cross-reactivity.
Solution Approach 2:
The invention applies segmentation by treating the fHbp protein as having functionally distinct domains: the N-terminal β-barrel domain (residues 1-120) which requires stability, and the C-terminal domain (residues 180-274) which contains the antigenic epitopes for cross-reactivity. Mutations are introduced only in the N-terminal domain to improve stability, while the C-terminal domain is left unchanged to preserve its immunogenic function. This domain-based segmentation allows independent optimization of stability and cross-reactivity.
3Reliability
If fHbp is used as vaccine immunogen to provide protection against meningococcal strains, then bactericidal activity is improved, but limited cross-protection against different serogroups and variants occurs due to variant-specific immunity
Solution Approach 1:
The patent applies universality by engineering the fHbp v2 mutant to function against multiple variants (v1, v2, and v3) simultaneously. The stabilized v2 sequence with specific mutations retains its ability to elicit bactericidal antibodies against v2 strains while also providing cross-protection against v1 and v3 variants. This multi-functional capability resolves the contradiction between maintaining strong bactericidal activity and expanding cross-protection coverage.
Solution Approach 2:
The invention uses parameter changes by modifying the amino acid sequence parameters of fHbp v2 to enhance its immunogenic properties. The substitutions L123R, E240A, and S32V alter the protein's structural and antigenic parameters, enabling it to maintain high bactericidal activity against v2 strains while also eliciting cross-reactive antibodies against other variants. This parameter optimization achieves both reliable bactericidal function and broad adaptability.
Data Source
AI summary
The inventors have identified residues within variant 2 and variant 3 of meningococcal fHpb which can be modified to enhance their properties.