To gain understanding of gene therapy, it's best to get started with some basic facts:
Genes are the basic units of heredity. An extensive array of ailments and conditions are due to a defect in a person's genes, and some of these genetic disorders include autism and other types of mental retardation, autoimmune disease, hypertension, heart disease and cancers. Of course, in some cases genes are not the only factor in the development of disease; environment and lifestyle are at play, as well.
Gene therapy aims to provide a cure to these conditions by correcting the particular defective genes responsible for the development of the disease.
There are several methods being developed for gene therapy, and the most common approach is the insertion of a normal gene into the appropriate genome to replace the unhealthy gene. Other methods include:
- repair of the abnormal gene through reverse mutation, wherein the gene is restored to its healthy state
- swapping of the abnormal gene for a normal gene
What carries the curative gene to the target cells? It is called the carrier molecule or ‘vector.' Once this vector has reached the target cell, it then discharges the remedy or the therapeutic human cell into it. It may come as a surprise but viruses (including HIV) are the ones with the most potential as vectors. This is because viruses naturally bind to their hosts and introduce their genetic material into it, and then produce additional copies of themselves. By replacing the virus' harmful genes with the genes coded with the desired cure, a virus theoretically is the perfect vector. A lot of study and experimentation are still being conducted to fully refine this method.
Apart from the systems that make use of viruses, there are some other options for gene therapy. The simplest among these methods is through straight insertion of therapeutic DNA into target cells. However, this is a limited procedure because it can only be used with particular tissues. It is also impractical since it requires big amounts of DNA.
As of recently, gene therapy is on its experimental stages. It has achieved some levels of success, but there is still a huge amount of risk involved in carrying it out. What are some of the problems that gene therapy is facing?
- Short-lived nature. Scientists encounter problems assimilating healthy DNA into the genome, specially considering that cells split quickly. Because of this, patients would have to continuously undergo gene therapy.
- Natural immune response. As the human immune system is designed to attack invaders, these artificially coded genes may be attacked by the immune system.
- Problems with carriers. Viruses present numerous severe complications such as toxicity, immune and inflammatory responses. There is also a possibility that the vector virus may cause disease once inside the system.
- Gene therapy has mostly concentrated on single cell disorders such as cystic fibrosis, hemophilia, muscular dystrophy and sickle cell anemia. However, the most common disorders are due to variations in many different genes.
As mentioned, gene therapy is largely experimental. However, gene therapy has also encountered some level of success. For example, in 2007, a hospital in London successfully carried out gene therapy for inherited retinal disease on a 23-year old male.
Much more studies and experimentations are still needed towards making gene therapy a safe and effective procedure benefited from by humankind.