Diagnosis of diseases

a) Diagnosis of diseases caused by protozoa and helminthes

The monoclonal antibodies and DNA probes are being used as very sensitive tools in biotechnology to diagnose the diseases caused by protozoa and helminthes. Monoclonal antibodies can be used through serological tests which takes only minutes as compared to conventional methods which require some weeks as the bacteria and viruses have to be cultured e.g. in Herpes virus.

The DNA probes are more sensitive than monoclonal antibodies and the process takes hours instead of weeks. Readymade DNA probes for Herpes virus and other human, animal and plant viruses are being prepared. Probes are now available for a number of human parasites from the group protozoa and helminthes.

b) Diagnosis of sexually transmitted diseases (STD) using monoclonal antibodies

The occurrence of sexually transmitted disease has gone up in recent years both in developed as well as developing countries. Some of the pathogens causing these diseases are- Neisseria gonorrhoeae, Chlamydia trachomatis, Herpes simplex virus etc. The conventional methods for the diagnosis of these diseases are microscopic examination, culture method, Immunological method, and measurement of antibody.

The use of monoclonal antibody has been very effective in the diagnosis of these diseases. The cell hybrids are prepared using hybridoma technology and screening of cell lines is done through replica plating technique. Hybrid cells are placed in a 96-well microtest plate. Small sample of culture fluid from each well is placed on replica plates followed by impregnation of each well with a specific antigen. The immune reaction is detected through radio-immunoassay in which 125I-labelled protein A (which binds to Fc protein of human IgG in the immune complex) is added to each well and then examined by autoradiography. The positive reactions can be traced to original wells and the cell line then multiplied for production of specific monoclonal antibodies. Using this technique, monoclonal antibodies could be prepared that would distinguish between the different pathogens causing STDs.

c)Antenatal diagnosis of congenital diseases.

If there is a chance of giving birth to a baby with congenital defects then it may be desirable to diagnose the condition of the foetus during gestation. This can be done by extracting some cells from the foetus by drawing a few milliliters of amniotic fluid with the help of hypodermic needle. The free cells of the foetal origin from the amniotic fluid can be cultured and tested for karyotype analysis, enzyme production, and restriction fragment analysis of it’s DNA, to detect any abnormality.

It is possible to identify a disease with in two months of pregnancy as compared to 18 weeks period required earlier. The number of disease specific DNA probes is also increasing at a fast rate which will further help in antenatal diagnosis.


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