What is gene therapy ?

Gene therapy is emerging as a promising treatment option for diseases which don’t have any treatments. There are so many diseases which don’t have any treatment and are caused due to defective gene. For example Duchenne Muscular Dystrophy DMD, where a patient would lose life without any treatment that treat and eliminate the root cause of the disease, the inability of patients DNA to express a gene that code for biosynthesis of a protein dystrophin. Without the protein  dystrophin the muscles of leg and chest get weaker and weaker causing respiratory failure and death.

Few days back USFDA has approved a gene therapy for Muscular Dystrophy, it’s a landmark golden day in the history of medicine. Patient affected with DMD will now get treatment that eliminates the root cause of the disease. The gene therapy enable patients body to produce protein distropin and strengthen the muscles of patients affected with DMD.

What is a Gene ?

Gene is a part of DNA which is responsible for exhibiting acquired as well as hereditary characteristics in the person. Smaller units of DNA is a gene which is a portion on DNA that codes for specific protein synthesis, like protein required for tissue formation and enzymes required for biosynthesis of various proteins are coded and biosynthesised through gene. The process of biosynthesis of protein and enzymes and factors and co factors takes place through process of transcription, where a m-RNA is formed along with Gene as per the codons the sequence of the amino acid is formed in mRNA this process is called transcription. After transcription m-RNA with the help of t-RNA take part in translation and protein synthesis.

Deficiency of a perticular gene to start the process of transcription for protein synthesis, makes the gene ineffective causing deficiency of the protein, which is must for normal functioning of human body.

There are many diseases which are caused due to ineffective or absence of the gene.

Hemophilia A and Hemophilia B and Muscular dystrophy, Mitochondrial disease are few examples of diseases caused due to absence or ineffective gene.

There are many life threatening diseases caused even due to over expression of a gene that produce a protein that is not required for normal functioning of human body. While excessive production of such protein causes serious disease, like cancer or deformity.

How gene therapy works?

A gene which is required for normal functioning of human body is made in the laboratory with the help of gene edition and it is incorporated in to a bacterial or a viral carrier or the liposomes taged with antibodies for targeted delivery of the gene in to the targeted organ or a tissue. The bacterial and viral vectors infect the targeted organ or tissue like the live virus do. After attachment and fusion with organ or body cell membrane, the gene is inserted into nucleus of the cells present in the organ or tissue.

After this the inserted gene start producing the protein for which it is designed for. This way deficiency of a protein or a factor that is essential for normal functioning of human body is eliminated.

Some times the excessive over active gene is required to stop production of the unwanted proteins is also carried out with the help of gene edition and gene therapy.

Precautions to  taken for gene therapy?

No one can exactly predict that the gene therapy will yield desired results without any untoward side effects. While it may pose other serious concerns causing mutations in the genetic material if the artificial gene get integrated with the human DNA.

Therefore long time follow up observations are required to be done in patients treated with gene therapy.

Which live viruses are used for gene delivery as vectors?

1. Lentivirus 2. Retrovirus 3. Adenovirus 3.Herpes virus 4. Measles viruses 5. Alpha viruses are used for gene delivery in gene therapy products. The viruses are genetically modified to lower or render them non-toxic. The vector viruses don’t cause disease while they just complete the process of infecting cells and deliver the gene inside the nucleus of the cells of the targeted organ or tissue.

Which live bacteria are used to deliver gene in gene therapy?

Bacteria carry gene in the form of plasmid and deliver it in the host cell nucleus the process is termed ‘bactofection’.

1. Salmonella, 2. Listeria, 3. E. coli, 4.Clostridium 4. S. typhimuriumare used as vectors in gene therapy.

Gene therapy is modified to achieve cancer cell death, by delivery gene that produce Oncolytic enzymes and protein causing apoptosis (cancer cell death).

Referances: https://www.cdc.gov/genomics/disease/health_equity.htm