Gene Therapy… : Gene Therapy… By...
Tanushree swain * * Introduction to Gene, Genetic disease & Gene therapy … : Introduction to Gene, Genetic disease & Gene therapy … Gene : These are carried on chromosome & are the basic physical & functional unit of heredity.
Genetic disease : Human beings suffer from more then 5000 different disease cause by single gene mutation. ex:-cystic fibrosis, sickle cell anemia ,hemophilia, cancer, hypertension , muscular dystrophy ,mental illness etc…
Gene therapy : It is a technique for correcting defective genes responsible for disease development .the approaches are:- A normal gene may be inserted into a nonspecific location within the genome to replace a functional gene.
. An abnormal gene could be repaired through selectively reverse mutation, which return the gene to its normal function. Law & ethics related to gene therapy… : Law & ethics related to gene therapy… Every person could not use these ,the candidate for gene therapy are selected on the basis of the following criteria..
The disease should be life threatening.
The gene responsible for the disease has been cloned.
A suitable delivery system should be available. First approved gene therapy… : First approved gene therapy… On sept.14.1990 at the u.s. national institutes of health. W.F. Anderson & his collages, performed the first approved gene therapy procedure on four year old Ashanthi desilva. born with a rare genetic disease called severe combined immunodeficiency (SCID) also known as “bubble baby syndrome”.
What did they do?
In Ashanthi’s gene therapy procedure doctors removed white blood cells from the child’s body let the cells grow in the laboratory, inserted the genetically modified blood cells back into the patient’s blood stream.& success, as of early 2007,she was still in good health & she was attending college. A success story… : A success story… Neurologix a biotech company announced that they have successfully completed its land mark phase 1 trial of gene therapy for Parkinson’s disease.
This was a 12 patient study with four patients in each of three dose escalating cohorts. all procedures were preformed under local anesthesia & all 12 patients within 48 hours pf the procedure,& followed for 12 months primary outcome of the study design, safely & tolerability, were successfully met. How does gene therapy work? : How does gene therapy work? In gene therapy a normal gene is inserted into the genome to replace an abnormal disease causing gene.
A carrier molecule called a vector must be used to deliver the therapeutic gene to the patient’s target cells.
Currently, the most common vector is a virus that has been genetically altered to carry normal human DNA.
Viruses have evolved a way of encapsulating & delivering their genes to human cells in pathogenic manner. Scientists have tried to take advantage of this capability & manipulate the genome to removed disease causing genes & insert therapeutic genes. Vectors for gene therapy… : Vectors for gene therapy… Some different type of viruses used as gene therapy vector:
Retro viruses: A class of viruses that can create stranded DNA copies of their RNA genomes. these copies of its genome can be integrated into the chromosome of host cells.
Adenoviruses , Adeno-associated viruses, herpes simplex viruses, are also used as vector. Some non virus mediated gene delivery system: : Some non virus mediated gene delivery system: The simplest method in the direct introduction of therapeutic DNA into target cells. like microinjection & gene gun method.
Introduction of the foreign DNA into cell by use liposome is known as lipofection.
Introduction of DNA into cell by exposing a very brief period of high voltage electric pulses is called electrophoration. Types of gene therapy… : Types of gene therapy… Gene therapy mainly classified into 2 types:-
* germ line gene therapy.
* somatic cell gene therapy.
Method of germ line gene therapy:
In vitro fertilization of egg.
Insertion of normal gene to the embryo through retrovirus or microinjection.
Integration of the normal gene & show its character.
method of somatic cell gene therapy:
Identification of defective gene which is responsible for disease causing
Synthesis of normal gene.
Isolation of particular cell in which the integration of normal gene take place.
Integration of normal DNA to the defective tissue. Current status of gene therapy… : Current status of gene therapy… Nanotechnology + gene therapy.
Gene therapy uses AIDS virus to fight AIDS.
Gene therapy uses in cancer treatment .
Nanotechnology + gene therapy…
Non viral substances such ormosil (organically modified silicate) have been used as DNA vector & can deliver DNA loads to specifically targeted cells in living animals.
(silicate) Gene therapy uses AIDS virus to fight AIDS… : Gene therapy uses AIDS virus to fight AIDS… In this technique the immune cells were removed from the patient’s bodies modified with a disabled AIDS virus known as a “lentivirus”
& then intravenously altered cells disseminated anti HIV material & prevented HIV from reproducing.
(lentivirus) Gene therapy uses in cancer treatment… : Gene therapy uses in cancer treatment… Gene therapy can be used to selectively target & destroy cells by …
Insertion of a copy of wild type p53 gene.
Antisence gene insertation which disable the over expression of oncogene. Problems need to be solved in gene therapy… : Problems need to be solved in gene therapy… Short-lived nature of gene therapy…
The rapidly dividing nature of cells prevent gene therapy from achieving any long-term benefits. patients will have to undergo multiple rounds of gene therapy.
Anytime a foreign object is introduced into human tissue, the immune system is designed to attack the invader.
Problem with viral vector...
There is always fear that viral vector once inside the patient may recover its ability to cause disease. Use of gene therapy… : Use of gene therapy… Though gene therapy is still in its initial stage & is associated with many unsolved problems but, still it has many uses like.
Replace missing or defective gene.
Deliver bacterial or viral gene as a form of vaccination.
Provide genes that promote the growth of new tissue.
Deliver gene that stimulate the healing of damaged tissue.
Large verity of genes are now being tested for use in gene therapy, example:- gene CFTR~for cystic fibrosis,
Gene EIA &p53 ~for cancer. gene AC6~for heart failure, etc… References… : References…