Valuable Products From Cell Culture
For large scale production of certain biochemicals, the genetically engineered baculovirus-infected animal cells are also in use in a bioreactor. To fulfil the process several 'perfusion systems1 have been developed that retain the cells in .the bioreactor at the time of replacement of conditioned medium with fresh medium. This results in increase in cell density and in turn cell productivity. For commercial production of products a large scale cell culture system and scaling up of process are required. Therefore, 'master cell banks' (MCBs) are established to meet out the demand. The MCBs are used to develop master working cell bank (MWCB) which meets the demand of production system. After several subculturing, the MWCB is regularly checked for any kind of changes occurring in cells. Thus, the large scale cultures are the source of all valuable products which are produced in a bioreactor. Diagram of a compact bioreactor is given in Fig. 6.6.
Products | Application | |
Erythropoietins | ||
Erythropoietin-a | Anaemia resulting from cancer and chemothcraoy | |
Erythropoietin-p | Anaemia secondary to kindney disease | |
Human growth hormones | ||
hGH | Human growth deficiency in children, renal cell carcinoma | |
Somatotropin | Chronic renal insufficiency, Turners' syndrom | |
Monoclonal antibodies (therapeutic) | ||
Anti-lipopolysacharide | Treatment of sepsis | |
Murine anti-idiotype/human | ||
B-cell lymphoma | B-cell lymphoma | |
Monoclonal antibodies (diagnostics) | ||
Anti-fibrin 99 | Blood clot | |
99 Tcm-FAb (breast) | Blood cancer | |
PR-356CYT-356-in-lll | Prostate adinocarcinoma | |
Plasminogen activator | ||
Urokinase type plasminogen activator | Acute myocardial infarction, acute stroke, pulmonary embolism, deep vein thrombosis | |
Tissue type plasminogen activator | ||
Recombinant plasminogen activator | ||
Vaccines | ||
HIV vaccines (gpl20) | AIDS prophylaxis and treatment | |
Malaria vaccine | Malaria prophylaxis | |
Polio vaccines | Poliomyelitis prophylaxis |
Production of monoclonal antibodies (MoAb) and hybridoma technology has been described in Genetic Engineering for Human Welfare . The mouse MoAb have revolutionized the field of biology and more specifically immunology. The mouse MoAb have been used in human patients with varying level of success who were suffering from leukemia, lymphoma, melanoma and colorectal cancer. Clinical trials have indicated several limiting factors such as : (i) heterogenecity of tumour cells (not all malignant cells carry relevant antigen), circulating free antigens (they bind Fab on antibody molecules and thus block MoAb from binding to the target cells), (ii) antigenic modulation (antigen modulated off the cell surface as a consequence of binding of MoAb to the cancer cell as in leukemin. This problem can be overcome by applying monovalent MoAb) (Balasubramanian et al, 1996).
The first human MoAb have been produced through this technique but the process is slow), (ii) interspecific hybrids (human B-cells isolated from bone marrow, periplasmal blood, spleen, lymph node, etc. are fused with non-secretary mouse or rat myeloma cells. From the hybrid cells human chromosomes were eliminated. The interspecific hybridoma produces MoAb which are of human type as expressed by human B-cells), (iii) EBV-transformation (The Epstein Ban virus transforms sensitized B-cells and results in production of immortal line of B-cells; the transformed B-cells secrete low amount of antibodies).
Table 6.8. Biotechnological applications of some insect cell culture systems.
Insects | Application |
Aedes aegypti (yellow fever mosquito) | Arbovirus antigens, vaccines, diagnostics |
Autographa californica (alfalfa looper) | Bioinsecticides |
Bombax mori (silkworm) | Bioinsecticides |
Heliothes virescens (tobacco bollworm) | Bioinsecticides |
Spodoptera frugiperda (fall armyworm) | Recombinant proteins |
Trichoplusia ni (cabbage looper) | Recombinant proteins |
Commercially desired proteins may be produced in vitro by using a susceptible continuous cell line of insect in a bioreactor. The fully grown cells are allowed to be infected by genetically engineered baculovirus. Baculovirus infects the cell line and lyse them resulting in release of protein products in the medium. Thereafter, protein is purified.
Adopting the same method bioinsecticides (occlusion bodies) can also be produced by using wild type virus. The occlusion bodies are then isolated from the bioreactor and used for the management of crops against the attack of insects (Agathos, 1991). Biotechnological application of some products derived from insect cell culture are given in Table 6.8.