Every protein is unique. This is commonly heard in the industry, often as an excuse when an upstream development project fails. But if every protein is unique, why do we keep trying to match a single expression vector to every single gene? If every protein is unique, they require unique vectors for optimal production.

In Vectron we already develop tailor-made expression vectors through the combination of proprietary vector elements from our genetic expression libraries. This results in unique expression vectors that give higher titers than what can usually be achieved with conventional expression vectors that are not optimized for every protein.

Vectron is now taking this approach one step further. An evolutionary step.

In VB EVOLUTION we evolve new expression vectors. We do this by leveraging our deep understanding of the architecture of the XylS/Pmexpression cassette to generate libraries of millions of randomized expression cassettes which we then screen for maximal production of the target protein. By doing this, we can discover novel expression cassettes that would otherwise never be designed, but that are particularly suited for the expression of specific genes.

VB Evolution is only possible due to our extensive understanding of the XylS/Pm expression cassette and our development of an innovative high-throughput (HTP) screening method that allows us to quickly find the one vector that is optimal for each and every gene - the one in a million. The HTP screening method is universal and can be applied to any protein without any necessary optimizations.

Figure 1: Schematic overview of VB Evolution. Hotspots in the expression vectors are mutagenized resulting in large plasmid libraries with randomized expression cassettes. After transformation of E. coli, a high-throughput (HTP) screening method is applied to identify the strains that produce the most of the target protein. This HTP method is proprietary and can be applied to any target protein without any optimization, resulting in a universal approach.

We recently concluded our first commercial test of VB Evolution with a customer for their novel therapeutic protein. In this project we developed expression vectors using our normal approach (using VB Expert and VB Solutions) and in parallel using the VB Evolution approach. The idea was to compare the timelines, the costs and the final results for these two different approaches.

Conclusions based on the above-mentioned project, as well as additional in-house testing ot VB Evolution, is that this novel method can be performed within typical timeframes for upstream development projects (2-6 months), and with no additional costs.

But more importantly, using VB Evolution we are able to identify expression vectors that are entirely novel and unique, and that results in higher titers.

For the customer-driven project, the increase in yield compared to conventional expression vectors is significant. Using one iteration of VB Evolution, we obtained 1.8-fold higher soluble titers than what we achieved with the best of our vectors that were based on combining pre-made expression elements. The effect on insoluble titers have not been determined yet but we expect to present more quantification data in the next issue of our newsletter.

Anne Krog, Senior research scientist
"Today, strain development is based on using predesigned libraries of vector elements with an upper limit of strains that can be tested per project. Our newest technology, VB Evolution, makes it possible to adapt our vector to the individual protein of choice. Creating a vector specially designed for your protein."