Role of Recombinant DNA Technology in Medical Sciences....Article (Issue # 50)

THE MOST human protein pharmaceuticals are available in only limited quantities. They are costly to produce and in a number of cases their biological mode of action is not well-characterized. Many infectious and fatal diseases are very difficult to be treated by these pharmaceuticals. So the need of the hour is that to develop such techniques that help the human beings in developing the cost effective drugs and also having good efficiencies. In this regard, Recombinant DNA Technology has been evolved as a revolutionary science. Plant-derived pharmaceuticals are poised to become the next major commercial development in biotechnology. The advantages they offer in terms of production scale and economy, product safety, ease of storage and distribution cannot be matched by any current commercial system. They also provide the most promising opportunity to supply low-cost drugs and vaccines to the developing world like Pakistan. Thus modern biotechnology helps the human beings in various ways such as disease prevention, disease diagnosis, disease treatment, gene therapy and immunodeficiencies etc.

Disease Prevention: Vaccination protects a recipient from pathogenic agents by establishing an immunological resistance to infection. An injected or oral vaccine induces the host to generate antibodies against the disease-causing organism; therefore, during exposure, the infectious agent is inactivated (neutralized or killed), its proliferation is prevented and the disease state is not established.

Disease Diagnosis: In the 1970’s scientists found ways to cut DNA into fragments at predictable points, using a kind of chemical scissors called restriction enzymes. After studying large groups of family members and their genetic makeup, they identified variations in the size of DNA segments, called polymorphisms that appeared along with certain diseases. Using this knowledge, scientists devised DNA probes and short portions of DNA that are able to attach them to the polymorphism associated with a specific disease. The probes are labeled with a radioactive substance. They can be easily visualized by exposure on film.

Currently, DNA/PCR amplification based assays are used to diagnose a variety of infectious and genetic diseases (including hepatitis C, tuberculosis, Beta-thalesemia). Because they can often detect and identify infectious diseases in a matter of hours, DNA based tests could replace current tests that take days to complete.

Disease Treatment: The development of recombinant DNA and monoclonal antibody techniques, combined with an understanding of the molecular structure and function of immunoglobulin molecules, has provided specific antibodies as therapeutic agents to treat various diseases. Antibody genes can be readily manipulated because the various functions of an antibody molecule are confined to discrete domains.

A number of human disorders that result from the over-production of a normal protein may be treated by using nucleotide sequences that bind to a specific mRNA and prevent its translation, i.e. an antisense oligonucleotide; RNA sequences that bind and cleave specific RNA molecules, i.e. interfering RNAs.

The development of effective treatments for genetic disease has been elusive because in many instances, the appropriate gene product cannot be provided to a patient. However, when a normal version of a gene has been identified and cloned, it may be possible that either it is or a cDNA derivative can be used to correct the defect in affected individuals. Viral and normal systems have been developed for the delivery of therapeutic genes. Viral vectors take advantage of the ability of a virus to penetrate a specific cell, protect the DNA from degradation and direct it to the cell nucleus. A number of viruses have been engineered for gene therapy applications.

Gene Therapy: Gene therapy may be defined in broad general terms as; “Introduction of a normal functional gene into cells, which contain the defective allele of the concerned gene with the objective of correcting a genetic disorder or an acquired disorder”. Application of gene therapy involves the following basic developments:

• Identification of the gene that plays the key role in the development of a disorder.

• Determination of the role of gene product in health and disease.

• Isolation and cloning of the gene.

• Development of an approach for gene therapy.

Human beings suffer from more than 5000 different diseases caused by single gene mutations e.g. cystic fibrosis, sickle cell anaemia, haemophilia, Hunter’s syndrome etc. In addition, many common disorders like cancer, hypertension and mental illness seem to have genetic components.

Immunodeficiencies: In cases of immunodeficiencies, the immune system is impaired to various degrees so that it is unable to protect the host from diseases causing agents or from malignant cells. Immunodeficiency may affect either adaptive or innate immune functions, and it may be primary or secondary in nature. An immunodeficiency that arises from a genetic or development defect in the immune system is called a primary immunodeficiency. Most of the primary immunodeficiencies are inherited and their precise molecular and genetic bases are known. The treatment of primary immunodeficiencies offers the possibilities of replacement of; (1) the missing protein (2) the missing cell type or lineage, and (3) the missing or defective gene.

The loss of immune functions as a result of exposure to various agents, such as human immunodeficiency virus 1 (HIV-1) is called secondary or acquired immunodeficiency. HIV infection produces acquired immunodeficiency syndrome (AIDS), which almost inevitably results in death.

http://www.technologytimes.pk/mag/2010/dec10/issue04/role_of_recombinant_dna_technology.php