The Novelty of Gene Therapy
by Jesse Kaminsky
David is born to two loving parents. After being examined he is determined to be a healthy size and free of any serious conditions. Over the following three months his parents get to know him. They discover the joys and stresses of caring for a baby. David grows normally. It’s approaching winter when he develops some kind of a cold, which seems to worsen over a day or two as any cold does. He dies two days later.
David was born with Severe Combined Immunodeficiency (SCID), a rare condition resulting from one of several genetic defects. Occasionally children are born inheriting the defective genes from a parent, or with a spontaneous mutation in the gene responsible for the lack of production of T and B immune cells. Consequently, they are left with virtually no immune system.
Fortunately, given an early diagnosis (if babies are specifically screened for SCID), a bone marrow transplant can completely cure these children. However, as with all bone marrow transplants, the donor must be genetically close to the recipient. For those not diagnosed at birth or those with no suitable donor, few options remain, with one of the champions being gene therapy, which involves the treatment of genetic conditions through the direct insertion of appropriate genetic material.
Recently, gene therapy has shown astounding successes in the world of medicine. Several clinics applying gene therapy to kids with late diagnosed SCID have already demonstrated complete recoveries. The basic methods behind gene therapy are as clever as they are effective. The idea at its core is to replace a faulty gene with one that functions properly. Accomplishing this task requires a way to deliver a gene into a cell, a transporter that will force its own genetic composition into the cell. Ironically, nothing does this better than the very entities SCID kids are incapable of fighting off – viruses. The sole purpose of this virus is to replicate its genetic material using other living cells.
Modifying a viral transporter to deliver and safely insert the healthy version of the gene requires targeting the correct cell type. Furthermore, there are many issues that arise from the infective nature of viruses, the largest concern being that gene therapy can cause cancer, as has already been shown by four instances of leukemia following therapy trials. Fortunately, this complication is resolved by the use of different viruses that can be fine tuned for an ideal molecular apparatus. Of course, if the patient does have a functional immune system and is being treated for something other than SCID, there is a significant concern that an immune response to the gene therapy will occur - at least one patient has died from such a response. Fortunately, it is possible to weaken the immune system prior to injection, effectively reducing this risk.
Due to challenges such as these, it has taken gene therapy decades to finally reach the market despite its potential to cure otherwise incurable disease. Finally, in 2012, a drug called Glybera was approved as the first gene therapy to be distributed in the western world. The medication is presently only prescribed to patients who suffer from lipoprotein lipase deficiency, a genetic condition in which there is a lack of an enzyme used for digesting fats, resulting in potentially fatal pancreatitis. Glybera uses a modified adeno-associated virus, a popular vector in therapy, to deliver a healthy version of the gene responsible for the expression of this vital enzyme. This prevents it from disrupting other important genes, which could lead to cancer or being passed onto future generations.
In today’s era of medicine, the only well-funded and approved gene therapy projects are those targeted at resolving otherwise incurable or severely dangerous conditions. However, genes are responsible for more than preventing disease. They control every aspect of our life, how we look, how we think and even how we act. There have already been some pioneering gene therapy projects that attempt to introduce new genes, as opposed to replacing defective ones. This allows us to add bodily functions that might enable someone to express a novel characteristic. For example, one clinic in New York has used an adenovirus to insert a gene into cells responsible for hair production, resulting in rapid hair growth (so far only in mice). The gene itself is known as Sonic hedgehog (SHH) (perhaps explaining the strangely excessive hair growth off the back of the renowned SEGA video game character’s head).
There are innumerable applications of the gene therapy concept! Theoretically, gene therapy could be used to alter the nature of anything that is rooted in genetics. Imagine a world in which a baby is treated at birth with a vector that inserts a gene into its brain, improving overall long-term memory. Or maybe even a gene that could vastly improve someone’s musical sense. Given enough time, humanity may find ways to fix or improve every aspect of our biology through gene therapy. We could drive lactose-intolerance to extinction, render allergies an issue of the past and even improve intelligence to the pinnacle of perfection.
The only obstacle standing in the way is one important question. If we master the human body, is it still human?