Recombinant DNA technology has helped in the large scale production of safe and more effective therapeutic drugs. At present around 30 recombinant therapeutic drugs have been approved for human use out of which 12 are being marketed in India. Its applications in health care include.-
Diagnosis of diseases
- Commercial production of pharmaceuticals for disease therapy.
Valuable proteins (Hormones or enzymes)
- Gene therapies and - Powerful vaccines etc.
1. Therapeutic Drugs. Genetically engineered bacteria like E. coli are to get proteins or drug at commerical scale e.g., humulin, human grows formone, atrial peptides for treating blood pressure, kidney failure etc.
2. Gen theraphy. It include treatment of hereditary diseases caused by single defective gene, by replacing the same. c.g., cystic fibrosis, ADA deficicney (SCID, Severe combined Immuno deficiency), Muscular dystrophy etc.
3. Vaccines. Vaccine is produced using recombinant DNA technology. A recombinant vaccine contains protein or a gene encoding a protein of a pathogen origin that is immunogeau.c. A gene coding an immunogenic protein from the pathogen, is isolated, cloned and used for vaccine production. The vaccines based on recombinant proteins are also called Sub-Unit Vaccines.
(i) Whole protein vaccine. Hepatitis B Vaccine is produced from surface antigens of transgenic yeast by r-DNA technology. They can also be produced in genetically engineered microbes, cultured animal cells, possibly in insect and plants.
(b) Recombinant Polypeptide Vaccines. In some cases, the immunogenic portion of the protein-recombinant polypeptide is used as vaccine e.g., gene encoding B polypeptide (part of cholera enterotoxin-A, A and B polypeptide) has been cloned and the recombinant B polypeptide produced is being used, in combination with inactivated cholera cells, as an oral vaccine in place of conventional injectable cholera vaccine.
Immunogenicity of foot and mouth disease virus coat protein is due to its aminoacids 114-160 and also 201-213. They induce antibodies which neutralize the virus and thereby provide protection against the foot and mouth disease.
(c) Live Recombinant Vaccine. The most advanced and promising approach in which concerned pathogen gene is introduced in to the genome of selected viral/bacterial vector which is suitably attenuated and the live microorganisms are used for vaccination. Vaccinia virus appears to be more promising yector.
(d) DNA Vaccines. Recently vaccines based on pathogen naked DNA are being developed. The various approaches for DNA vaccines are as follow (i) injection of pure DNA (or RNA) preparation in to muscles (II) reimplantation of autologus cells (cells of the individual to be vaccinated) into which the gene has been transferred and (iii) particle gun delivery of plasmid DNA which contains the gene in an expression casette e.g., Skin cells. They elicit humoral inmune response and are usually shed off in a few days preventing long term persistence modified cells.
Edible Vaccines. Now-a-days the edible vaccines are produced from transgenic plants in which an orally active antigen of the target pathogen is expressed and accmulated, and which is fed to animals/humans for immunisation against the pathogen. For animals, crops used as feed e.&., alfalfa and other forage/fodder crops, are suitable for the expression of such antigene, while for humans, potato tube fruits like banana, which are consumed raw, have to be used.
A more palatable approach for edible vaccines would be to deliver the immunogenic proteins through honey. Attempts are now being made to use the nectary specific promoter to drive such pathogen genes that encode proteins which are immunogenic and express the gene construct in plants with nectaries. The honey made from the nectar of such transgenic plants is expected to contain the immunogenic protein and will serve as a Vaccine when consumed.
4. Molecular Diagnosis. Recombinant DNA technology, polymerases chain reaction (PCR) and Enzyme-Linked Immunosorbent Assay (ELISA) are some of techniques for early diagnosis because :
(i) Very low concentration of bacteria or virus (before the appearance of visible symptoms of a disease) can be detected by amplification of their nucleic acid.
(ii) PCR is now used to detect HIV in suspected AIDS patients. It is a powerful technique to identify many other genetic disorders.
(iii) ELISA-Enzyme linked Immuno sorbent Assay which is based on the principle of antigen antibody reaction, Infection by a pathogen can be detected by the presence of antigens (proteins, glycoproteins) or by detecting the antibodies synthesised against the pathogen.
(iv) Hybridoma and monoclonal antibodies (of one type) are used for diagnosis and screening of cancer. Monoclonal antibodies are being synthesised by popular hybridoma technology using antibody producing lymphocytes and myeloma cells.
