From UFStarfleet Wiki
In phase one, the effects of borg technology upon shape shifting DNA was explored. Dr St James, being a shape shifter, willingly severed his right arm at the wrist and elbow several times thanks to his regenerative techniques, and let his samples sit in various conditions to optimize the results. After subjecting the samples to Radiation and the Shape shifting Degeneration syndrome, it was found that normal unaltered shape shifting DNA can repel Borg nanobots due to the tremendous regeneration rate of cellular tissue, as well as the unstable nature of shape shifters DNA structure.
Phase Two was conducted in the science lab aboard Tranquility Station, where after obtaining blood samples from various donors and also subjecting them to various stimuli, it was found that under ideal conditions, it is possible to splice in the shapeshifting Genome of shapeshifter DNA into the DNA coding of a human or non-shapeshifting humanoid race and temporarily give it the ability to become a shape shifter.
Phase three concluded the project by subjecting the altered samples from Phase two to Borg nanobots. The nanobots were ineffective.
This treatment has since been used to great success on numerous UFS officers who have succumbed to Borg assimilation.