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Therapeutic usage of genes can be either preventive or curative for genetic disorders. There are several approaches to alter the onset of the disorder which includes; Gene Replacement- The gene responsible for the disease can be replaced by a healthy one, Gene Insertion- Inserting a functional gene, Gene Silencing – Silencing gene which is responsible for particular disease. It can be done in Somatic cells as well as in Germline cells. Treatments in the somatic cells are done in phenotypic level, where the alteration done in these cells are not carried to the next generation. Germline cell treatments are done in the genotypic level, where the genetic makeup of an organism is altered and hence passed over to the next generation.

Vectors for the gene can be categorized as viral and nonviral.Examples for viral vectors are Retrovirus, Adenovirus, Adeno-associated virus, Herpes- simplex virus etc. Nonviral vectors include Liposomes, Conjugates and DNA injection.

Scientists from Ohio University designed new nonviral vector, a nanoparticle (conjugate) which can be viewed only by atomic force microscope. It was developed by conjugating calcium phosphate and lipid shell. This vector along with GFP (Green fluorescent protein) was injected into mouse cells to test the efficacy of the vector. It was observed that the vector could successfully deliver the DNA into the cells without any degradation, resulting in the fluorescing of cells with minimal damage.

Gene therapy is considered as a magic bullet for many diseases. It has achieved success as a curative for ADA- SCID (Severe Combined Immune Deficiency) –type of SCID where the Adenosine deaminase gene is defective.

Recent Research activities in treatment of genetic disorders using gene therapy are discussed below;
Hemophilia A- Researchers from Minnesota Medical School developed a nanocapsule, SB transposon(SB-Tn) coated with hyaluronane, targeting the hepatic cells. The quality of the encoated nanocapsule carrying b domain deleted factor viii gene (B--FVII) was tested by targeting the hepatic cells. It was observed that the bleeding was reduced in mice significantly.

Parkinson disease- A team of scientists from the University of California, San Francisco (UCSF) were successful in treating Parkinson’s disease in monkeys. Monkeys were modified to develop Parkinson’s and then later treated with AAV-GDNF gene therapy. glial cell line-derived neurotrophic factor GDNF gene, acts as a growth factor for dopaminergic neurons. The animals produced relatively higher levels of dopamine.
Gene therapy using Tyrosine Hydroxylase (TH), Aromatic L-amino acid decarboxylase (AADC) and GTP-cyclohyrolase 1 (GCH) are under development.
X-linked adrenoleukodystrophy - Dr. Patrick Aubourg of the University Paris-Descartes and team have clinically experimented on two children suffering from X-linked adrenoleukodystrophy. This is a condition where ALD gene fails in the production of ALD protein, a protein which is required for degradation of fatty acids. Inactive HIV was the vector used for the delivery of the gene to the cells.
Cancer- Researchers at Strathclyde University claims to achieve 90% success rate in treating the skin cancer. Plasma protein- transferrin was used for this purpose. Over a month regression of tumors with no side effects were observed.
Heart failure- Research team from University of California inserted a recombinant gene for AAV- SERCA2a, gene which regulates calcium metabolism and a major factor for the contraction of the heart muscles into coronary arteries.
Diabetics- Scientists from Baylor College of Medicine, Houston solved the defects that cause Type 1 diabetes: autoimmune attack and death of the insulin-producing beta cells. They used a novel approach towards both the conditions, interleukin-10 gene was inserted to the mice resulting in preventing the B cells and reversal of diabetes.

These research works are undergoing pre-clinical trials on animals and some on humans. Experimental works on gene therapy are not limited in this article. Numerous research works are currently happening around the globe.