Great research Andrew! I just read your paper introducing this concept.
It struck me that an interesting application of this would be to develop a treatment (not a cure) for cancer by maintaining cancerous cells below a certain clinically deleterious threshold.
I would suppose the general algorithm would go something like:
1) Select appropriate retrovirus as your output for your code that targets white blood cells (HIV based). Have the "compiled" retrovirus spread through body.
2) Retrovirus should code for expressing a weak binding receptor on the white blood cell that would target the cell type susceptible to cancer
Normal scenario: If patient is healthy, the concentration of the target cell type are sufficiently low that the weak binding receptor doesn't impact the normal steady state concentration of the target cell type
3) Cancerous scenario:
- As target cell type concentration begins to increase, the weak binding receptor is occasionally activated
4) Activation ofthe weak binding receptor then triggers a "positive feedback" reaction, where a strong binding receptor is now expressed.
5) Strong binding receptor enables white blood cells to bind to target cell types (both healthy and cancerous, but by probability it will mostly be targeting cancerous) and destroy said cells.
6) As concentration of cancerous cells falls, weak binding receptor is now inactivated (it only substantially activates above a threshold).
7) Inactivation of weak binding receptor also inactivates the strong binding receptor.
8) Rinse and repeat if cancer cells continue uncontrolled growth.
Result: Patient still has the cancerous cells, but you don't end up with runaway growth, and the steady state of the target cell type never reaches a clinically mailicious level.
What do you think? I'd love to work on a problem like this...