E. Coli O-Antigen Bioconjugates via PglB Enzymatic Linking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current vaccines for extraintestinal pathogenic Escherichia coli (ExPEC) strains face challenges due to increasing antibiotic resistance and the presence of O-antigen modifications, necessitating improved methods for producing bioconjugates that cover predominant serotypes and account for unmodified and modified LPS forms.
Innovation Solution
The development of recombinant host cells capable of synthesizing bioconjugates of specific O-antigens by engineering them with variants of oligosaccharyl transferase (OST) to produce covalently linked polysaccharides with carrier proteins, including those with modified O-antigens like glucosylated O4, using enzymes such as GtrS, GtrA, and GtrB to introduce glucose branching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional chemical conjugation methods are used to produce O-antigen bioconjugates, then production simplicity is maintained, but manufacturing precision and immunogenicity are reduced due to epitope loss and heterogeneity
Solution Approach 1:
The patent replaces chemical conjugation methods with an enzymatic bioconjugation system using PglB oligosaccharyl transferase. This enzymatic system performs N-linked glycosylation of carrier proteins with O-antigen polysaccharides under physiological conditions, eliminating the need for chemical reagents and harsh conditions that cause epitope loss and heterogeneity in conventional chemical conjugation methods.
Solution Approach 2:
The patent employs in vivo bioconjugation where the PglB enzyme and its auxiliary proteins (PglC, PglD, PglE) function within the bacterial cell to automatically attach O-antigens to carrier proteins. This self-service mechanism ensures homogeneous bioconjugate formation without requiring external chemical intervention, thereby maintaining manufacturing precision while simplifying the overall production process.
2Device complexity
If vaccines target only unmodified O-antigens, then production is simplified, but reliability decreases due to inability to cover modified LPS forms in ExPEC strains
Solution Approach 1:
The patent modifies the O-antigen polysaccharide structure by introducing glucose branching at specific positions (e.g., position 3 of the repeating unit) through enzymatic action. This parameter change in the polysaccharide structure enables the vaccine to target modified LPS forms found in ExPEC strains, thereby improving reliability while maintaining manageable production complexity through controlled enzymatic modification.
Solution Approach 2:
The patent creates a universal vaccine approach by producing bioconjugates that can target both unmodified and modified O-antigen forms through the use of PglB-mediated conjugation systems. This multi-functional capability allows a single vaccine platform to cover diverse ExPEC strains with varying LPS modifications, enhancing reliability without proportionally increasing production complexity.
3Adaptability or versatility
If multiple O-antigen serotypes are targeted to cover ExPEC diversity, then adaptability improves, but device complexity increases due to need for multiple bioconjugate production systems
Solution Approach 1:
The patent employs a universal PglB oligosaccharyl transferase system that can conjugate multiple different O-antigen polysaccharide structures to carrier proteins. This single enzymatic system serves multiple functions by accommodating various O-antigen serotypes (e.g., O1A, O2, O6A, O8, O15, O16, O18A, O25B, O75) with different repeating unit structures, thereby achieving broad serotype coverage without requiring separate production systems for each serotype.
Solution Approach 2:
The patent segments the O-antigen polysaccharide synthesis and conjugation processes into distinct modular components: separate gene clusters for different O-antigen serotypes (rfb gene clusters) that can be independently controlled, while using a common PglB conjugation machinery. This segmentation allows independent optimization of each serotype's polysaccharide structure while maintaining a shared, efficient conjugation system, thus managing complexity while achieving versatility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the production of bioconjugates that provide enhanced immune responses against ExPEC strains, including those with glucose-modified O4 antigens, offering improved prophylactic and therapeutic options.
Implementation Method 1
The development of recombinant host cells capable of synthesizing bioconjugates of specific O-antigens by engineering them with variants of oligosaccharyl transferase (OST) to produce covalently linked polysaccharides with carrier proteins
Implementation Method 2
using enzymes such as GtrS, GtrA, and GtrB to introduce glucose branching
Data Source
AI summary
Methods of producing bioconjugates of O-antigen polysaccharides covalently linked to a carrier protein using recombinant host cells are provided. The recombinant host cells used in the methods described herein encode a particular oligosaccharyl transferase enzyme depending on the O-antigen polysaccharide bioconjugate to be produced. The oligosaccharyl transferase enzymes can be PglB oligosaccharyl transferase or variants thereof. Also provided are compositions containing the bioconjugates, and methods of using the bioconjugates and compositions described herein to vaccinate a subject against extra-intestinal pathogenic E. coli. (ExPEC).