TESSA™ vectors deliver a step-change in AAV manufacture; an easily scalable, contaminant-, chemical- and transfection free technology.
TESSA™ vectors take advantage of the adenoviral lifecycle, which contains two temporal phases; early and late. The early phase provides all the adenoviral help needed for high fidelity, high titre AAV manufacture. The late phase leads to adenovirus contamination. We’ve engineered supremely tight regulation of the adenoviral late region, which is wholly responsible for producing adenovirus structural proteins. Using TESSA™ technology, full early region expression, which provides all the help needed for AAV production, is still enabled, but the late region gene expression is turned off, meaning there is no adenoviral structural protein production. This represses adenovirus production by 99.99999 -100% during an AAV manufacturing run, while increasing rAAV yield, packaging efficiency and infectivity compared to both Ad5 helper plasmid or wild-type adenovirus.
Stable integration of AAV Rep and AAV Cap into the TESSA™ vector allows efficient and simultaneous delivery of all the necessary components for AAV replication in a single agent.
How it works
There are two stages to AAV manufacture with TESSA™. The first is to produce initial AAV seed stock. This can be done by plasmid transfection, for example with our transient AAV system, with a second TESSA™ vector encoding the AAV genome and gene of interest (a process we call TESSA 2.0 and which gives more efficient delivery than transfection), or any alternative existing approach.
Overall, producing AAV2 using two TESSA™ vectors gives approximately a 40-fold increase
in AAV particle yields compared to the helper free system. We also observe a >2400 fold cumulative increase in AAV2 infectious yield (1 in 6 genome-containing AAV2 particles is infectious from TESSA, compared to 1 in 1200 from plasmid based transfection; see data below), and an increased percentage of full capsids from 2-5% up to 70%.
In the second stage, called TESSA Pro, this AAV seed stock and another TESSA-AAV-Rep-Cap vector can be used to co-infect HEK293 cells. This leads to further AAV replication, so increasing the final AAV yield. Interestingly, whether you use AAV seed stock generated using two TESSA vectors or three plasmid transfection, the final AAV yield is comparable (see data below).
TESSA™ technology is fully scalable and significantly reduces the number of input materials required for AAV manufacture. It’s ideally suited for rapid and continuous production of GMP quality AAV, reducing the potential for batch to batch variation. Ultimately, TESSA™ technology will result in improved cost of goods, and improved safety of gene therapies.