Dual Vector Co-Expression of FVIII and Truncated vWF-Fc
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Solution Overview
Problem
Current methods for producing recombinant Factor VIII (rFVIII) face challenges due to its large molecular weight, complexity of post-translational modifications, and expression limitations, leading to low production levels and inconsistent protein ratios in mammalian cells, which complicates purification and results in excessive vWF-Fc relative to FVIII, causing purification difficulties.
Innovation Solution
A dual expression vector co-expressing both FVIII and truncated vWF-Fc from independent promoters with a single selectable marker, incorporating mutations to prevent multimerization of vWF-Fc and removing the propeptide domain to enhance expression and purification, allowing for controlled protein ratios and improved recovery of FVIII-vWF complexes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate plasmid transfection is used to express FVIII and vWF-Fc, then each protein can be expressed independently, but the ratio of FVIII to vWF-Fc becomes inconsistent and difficult to control
Solution Approach 1:
The patent combines FVIII and vWF-Fc expression into a single plasmid vector with two independent promoters, allowing both proteins to be expressed simultaneously in the same cell. This merging approach ensures consistent FVIII:vWF-Fc ratio (approximately 1:1) across all cell transfectants, eliminating the variability that occurs when using separate plasmids. The single plasmid system guarantees that every cell receives equivalent amounts of both expression cassettes, solving the ratio control problem.
2Reliability
If high levels of vWF-Fc are expressed, then FVIII binding and complex formation is improved, but purification becomes difficult due to excessive vWF-Fc overwhelming FVIII
Solution Approach 1:
The patent carefully balances the expression parameters of FVIII and vWF-Fc by using two independent promoters with optimized transcriptional control elements. This parameter optimization ensures that both proteins are expressed at high but balanced levels, maintaining reliable FVIII-vWF complex formation while preventing vWF-Fc from overwhelming FVIII during purification. The promoter design allows precise control over the 1:1 expression ratio, making purification feasible.
3Productivity
If B-domain is removed from FVIII, then production level improves, but protein stability and proper folding may be compromised
Solution Approach 1:
The patent uses vWF-Fc as an intermediary protein that binds to and stabilizes the B-domain deleted FVIII. The vWF-Fc acts as a molecular chaperone or stabilizing partner, compensating for the instability that arises from B-domain removal. This intermediary approach allows high production levels of BDD-FVIII while maintaining protein stability through the binding interaction with vWF-Fc, which also facilitates proper folding and complex formation.
Data Source
AI summary
The present invention relates to a co-expression vector that comprises both truncated von Williebrand Factor (vWF)-Fc DNA construct and B-domain deleted FVIII DNA construct in the same vector. By co-expressing FVIII and truncated vWF-Fc with one expression vector in cells, the present invention controls the ratio of gene templates for FVIII and vWF proteins, provides a higher protein ratio of FVIII to vWF during cell expression, that results in a better occupancy of FVIII in vWF, and creates a higher yield (>1000 IU/ml) and more stable expression of FVIII protein molecules. In one preferred embodiment, the truncated vWF contains mutations of cysteines in the D′D3 domain of vWF to reduce multimer assembly of recombinant vWF during expression, and thus increasing recovery and quality of FVIII.