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Home >> Biotechnology in Medicine >> Preparation and Selection of Antibodies for Diagnosis of STDs
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Preparation and Selection of Antibodies for Diagnosis of STDs - The cell hybrids are first prepared as done in hybridoma technology. Since there is a random loss of chromosomes in cell hybrids, 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, each of which is impregnated with a specific antigen.

The immune reaction is detected through radioimmunoassay in which 1251-labelled protein A (it 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 back to original wells and the cell line then multiplied for production of specific monoclonal antibodies. Using the above technique, monoclonal antibodies could be prepared that would distinguish between N. gonorrhoeae, C. trachomatis and HSY. Antibodies could also be selected which reacted with specific strains of the pathogen.
A mixture of three antibodies (4-G5, 2-H1 and 3-C8) identified 99.6% or the 719 isolates or N. gonorrhoeae, and did not react, with other species of Neisseria. This allowed diagnosis of gonorrhoeae with reasonable certainty.

In case of Chlamydia, the infectious form (called elementary body) enters the cell and within 48-72 hours forms a large inclusion body containing several hundred elementary bodies, which on release cause infection in neighbouring cells.
When cells were fixed in ethanol (18-72 hours, after infection) and stained with fluorescein conjugated antibody, characteristic inclusion bodies were detected as early as 18 hours after infection, by immunofluorescence (IF). Detection was also possible in cultures derived directly from patients, or even on smears on microscope slides prepared from specimens derived from infected tissue of the patient.

It has been shown that the direct test takes less than 30 minutes, which is a major advantage over the culture method. The suitability of monoclonal antibodies in the identification of Herpes Simplex Virus (HSV) has also been demonstrated.
A panel of four different monoclonal antibodies allowed distinction between the types HSyl and HSy2. Such tests are described as typing of HSY (typing means to find out the type). Therefore, monoclonal antibodies can be used effectively in diagnosis and typing of HSY directly on primary clinical specimens, derived from oral, genital, mucocutaneous or ocular sites.
 

 

 
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