Introduction:

Gene Therapy is a technique used to replace or knock mutated genes which in turn produced abnormal proteins causing disease or disorders.

Many methods are used to replace defective genes like

1. Replacement of defective gene by correct gene sequence
2. Normal gene can be added in the noncoding region of the genome
3. Selective reverse mutation can be used to correct the abnormal gene
4. The regulation of the genes can be altered
Types:

Germ Line Gene Therapy:
Germ cells that are sperm and eggs defective gene are modified to normal functional genes. These changes occur in genome and these therapeutic genes can be inherited in future generation. As of now this germ line gene therapy is not allowed in Humans due to some of the technical limitations and ethical concerns.

Somatic Gene Therapy:
Normal functional genes are added to somatic cells of a patient therefore the changes in the genome is limited to single generation it's not transferred to future generations.

Brief Details

In Gene Therapy vectors are used to carry Normal genes into the target cells.

Common Viral Vectors used in Gene Therapy are:

• Retroviral vector
• Adenoviral Vector
• Adeno-associated viral vector
• Herpes simplex viral vector
• Cis and Trans-acting elements

Non Viral Vectors used in Gene Therapy are:

• Liposome
• Naked DNA
• Oligonucleotides
• Nanoparticles
• Targeted DNA

RECENT DEVELOPMENTS IN GENE THERAPY:

1) Genes carried in Nanoparticles are used to cure Cancer in Mice
2) Gene Therapy curried Inherited Blindness by improving the sight in Human
3) Tumor suppressing genes carried in lipid-based nanoparticles reduced the number and size of human lung cancer tumor in mice
4) Gene therapy is used to reengineer Lymphocytes; these are successfully used to treat advanced metastatic melanoma in patients.
5) Gene Therapy used to cure patients with acute myeloid leukaemia.
6) Gene therapy cures deafness in Guinea pigs.
7) Gene therapy was successful in treating Sickle cell in mice
8) Gene Therapy attenuated inflammation caused by Pseudomonas pneumonia in mice.
9) Gene therapy was successful in treating Adenosine deaminase deficiency an autoimmune disorder in humans.

LIMITATIONS OF GENE THERAPY:

1) Therapeutic gene added to the cell is functionally active only for a short span of time.
2) Some problems are associated with the integration of therapeutic gene into the genome.
3) Vectors or carriers of therapeutic gene cause lot of additional problem in the patient they may induce toxicity, inflammation, immune response in the patient.
4) Disorders caused may be due to mutations in multiple genes are difficult to treat by Gene Therapy.
5) Viral vectors used in gene therapy also contain some of the viral genes still we do not know the long term effect of these viral genes.
6) If by chance therapeutic DNA is integrated in between a functional gene then it may lead to another additional disorder.
7) Deaths of patients have been occurred during gene therapy.
8) Gene therapy is pretty expensive.

FUTURE CHALLENGES:

1) More efficient and effective way to transfer genes into the human body.
2) Clear understanding of genes and its functions.
3) Resolve Ethical issues.

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