Monoclonal Antibodies

 

6.2 Impacts associated with the r-DNA technology

New vaccines base don r-DNA technology will be safer than traditional vaccines both for users and producers. Therefore with their increasing numbers and needs for large scale vaccinations, this development will have a major impact in human and veterinary medicine.

There are a number of diagnostic kits based on monoclonal antibodies prepared for diagnosing plant infections whether it is bacteria induced (example crown gall disease, xanthomonas disease of citrus and sorghum) of fungal (e.g. Fusarium on turf grass) or viral.

Human monoclonal antibodies produced by r-DNA technology are desirable and are much more suitable than conventional murine monoclonals for use in therapy and diagnosis. Human mAbs have important applications in oncology, pseudomonas and tetanus infections and autoimmune disease.

The major uses of the r-DNA technology in parasitic diseases are:

1) Specific DNA probes
2) Generation of cloned antigens for immuno diagnosis.
3) Production of cloned antigens for vaccination studies.
4) Characterization of functional protein for drug discovery.

The impact of this technology will also be felt in immunopurification of biologicals and in mass production of mAbs for diagnostic applications.

6.3 Impacts associated with the combination of hybridoma and r-DNA technology

Gen Pharma, a U.S. based biotech firm is trying to use homologous recombination in hybridomas to develop transgenic mice containing complex of genes that produce human immunologists. If successful, the effort should produce mice which makes human mAbs (Biotech news, May 18,1990).

Another significant research development is the production of mAbs from transgenic plants and seeds at 25 cents a gm. (biotech news, April 27, 1990). These developments which combine the hybridoma technology and the r-DNA technology are significant and would encourage the mass production of mAbs at an economical cost. This will also encourage the isolation of therapeutic antibodies and its mass scale production at a relatively inexpensive level. Therefore the impacts are likely to be significant once these technologies are commercialized which is quite likely by 995.

Another related development could be the injection of antibody producing genes into plasmids for transfer to E.Coli and their subsequent production in mass culture systems. Impact of this development could be as significant as the transgenic animal development and is likely to be achieved much earlier.

6.4 Assessment of the technological options

There are three technological options available to India for constructing cell lines to produce monoclonal antibodies. The most popular option is the hybridoma technology option with is being used on a large scale in many research institutes all over the country. A great deal of success has been achieved. However, a few technical problems exist with the technology (for example low frequency of fusion, weak antigens/ high screening load, isotype selection) but feasible improvements in the technology are available to surmount these problems. This calls for a comprehensive approach and additional investment in:

i) Setting up a suitable animal house where the right strains are bred and selected for immunization
ii) Using FACS for early cloning
iii) Working with better myeloma lines
iv) Using electrofusion wherever possible
v) Enriching target lymphocytes before fusion

The earlier section has indicated that the hybridoma technology will have significant impacts at comparatively lesser costs ad investments. This option is therefore a feasible and workable one.

The r-DNA technology option on the other hand is an option that has not been tried in this country for the production of mAbs. Results obtained abroad are still under evaluation. Therefore it would be too early to comment on the feasibility of this option in terms of economic and commercialization aspects. This option will have major impacts in genetically engineering animal mAbs for therapeutic purposes and in immunopurification of biologicals. The demand potential for such applications will be very significant in 2000 A.D. A potential of around 50 crores of rupees is estimated in 2000 A.D. for anti-cancer therapeutics.

The combination of the hybridoma technology and the r-DNA technology option would be very effective for mass scale production. However, sufficient amount of research and development work will be needed to engineer the antibody producing gene in plant or bacterial systems. Leading agricultural universities or institutes doing extensive work in microbial technology would need to be identified to do this kind of research. The impact of this development will be very significant in lowering the cost of diagnostic kits and in producing human mAbs.

Several technologies are currently in use all over the world for large scale production of monoclonal antibodies. The ascites technology is adequate for production of small (gram) quantities of antibody but becomes less appropriate with increase in scale.

Biotech, U.S.A claims that the micro encapsulation technology will be less expensive than the ascites option. Besides, it produces higher concentration of antibodies and does not require maintenance of animals, therefore reduces cost. Moreover, batch-tot-batch reproducibility is obtained which can not be achieved in ascites technology, contamination by virus or immunoglobulin is not obtained as no animal is used in this technology. Ease of purification following culture via micro encapsulation also contrasts favourably with those required by the other large scale manufacturing technologies.

It is also seen that product purity and activity consistent with regulatory requirements is easily achieved. The next best reactor system is the high density hollow fiber perfusion reactor system that has demonstrated a satisfactory yield of mAbs at a cheap cost of production.

The rankings and priorities of strategies for short terms and long term in the case of cell creation and mass production of MAbs is given below in Table E. and E.2.                                                                                                                 Back