Commonly used viral vectors such as adenovirus as AAV have unique immunogenic epitopes (identifier molecules) which induce an inflammatory response around the injection site. In addition, in a clinical trial that that took place in France that involved ten children resulted in the cure of boys with X-linked SCID (severe combined immunodeficiency) but in return, four children out of the ten involved developed leukemia along with one other child involved in a similar study taking place in the UK.
Additionally, a gene therapy clinical trial was being conducted at the University of Pennsylvania. An 18 year old patient by the name of Jesse Gelsinger was involved in the trial with hopes to correct his ornithine transcarbamylase (OTC) deficiency which a dangerous disease which can lead to the buildup of ammonia in the body. Jesse received the viral vector through a catheter through the groin artery which then traveled to his liver. Within hours of treatment, Jesse developed a fever and blood clots throughout his body. He then died four days after the attempted