**Conflict of interest**

Drs. Gordon and Hall are co-inventors of the targeted gene delivery system represented by DeltaRex-G and DeltaVax which was originally developed at the University of Southern California Keck School of Medicine, and are co-founders of Delta Next-Gene, LLC. Dr. Gordon is founder and president of the Aveni Foundation, a 501c3 public charity. NLA, TTK, DAB and SPC have no competing interest.
