Phage Display Selection for Cell-Surface Antigens
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Solution Overview
Problem
Current molecular display technologies face challenges in efficiently selecting affinity reagents specific to cell-surface targets due to high background noise and the need for purified antigens, particularly for proteins like multi-pass membrane G-protein coupled receptors, which are difficult to express and purify.
Innovation Solution
The method combines deep sequencing with phage-displayed synthetic antibody libraries, allowing for the identification and recovery of rare binding clones without the need for additional purification steps by comparing positive and negative selection pools and using PCR-based rescue strategies to isolate clones specific to cell-surface antigens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional phage display selection is used against cell-surface antigens, then affinity reagents can be isolated, but high background noise from non-specific binding clones reduces selection efficiency
Solution Approach 1:
The patent performs preliminary negative selection by pre-incubating phage libraries with cells lacking the target antigen to remove non-specific binders before the actual selection, thereby reducing background noise and improving selection specificity
Solution Approach 2:
The patent uses deep sequencing as an intermediary tool to objectively quantify and compare phage binding specificity across different selection pools, enabling precise identification of true positive clones amidst background noise
2Measurement precision
If purified antigens are used for selection, then specific binders can be identified, but the requirement for purified antigens limits the range of targetable proteins
Solution Approach 1:
Instead of purifying the antigen and displaying antibodies against it, the patent inverts the approach by displaying the antigen on cell surfaces and screening phage libraries against these intact cellular targets, eliminating the need for antigen purification
Solution Approach 2:
The patent enables the selection system to handle diverse antigen types including membrane proteins and complex multi-subunit proteins that cannot be easily purified, thereby universalizing the applicability of phage display to various difficult-to-target antigens
3Reliability
If affinity-based selection pressure is applied, then high-affinity binders are enriched, but sequence convergence reduces diversity of recovered clones
Solution Approach 1:
The patent applies only 2-3 rounds of affinity-based selection instead of extensive selection pressure, which is sufficient to enrich high-affinity binders while preserving greater sequence diversity in the population
Solution Approach 2:
The patent uses deep sequencing to provide feedback on the diversity and affinity characteristics of the selected population, allowing optimization of selection stringency to maintain both high affinity and diversity
4Measurement precision
If additional purification steps are performed, then binder specificity is confirmed, but the process time and complexity increase
Solution Approach 1:
The patent replaces traditional mechanical purification and validation steps with deep sequencing technology that can rapidly analyze and identify specific binders through sequence analysis, dramatically reducing recovery time while maintaining identification accuracy
Data Source
AI summary
There is provided herein a method for identifying and/or recovering at least one genetically encoded affinity reagent specific for a target molecule by screening using molecular display in conjunction with the sequencing of positive and negative selection pools from the screen.