Production of highly pure monoclonal antibodies without purification using a hollow fiber bioreactor

Monoclonal antibodies as diagnostics; an appraisal

Ever since the development of Hybridoma Technology in 1975 by Kohler and Milstein, our vision for antibodies as tools for research for prevention, detection and treatment of diseases, vaccine production, antigenic characterization of pathogens and in the study of genetic regulation of immune responses and disease susceptibility has been revolutionized. The monoclonal antibodies being directed against single epitopes are homogeneous, highly specific and can be produced in unlimited quantities. In animal disease diagnosis, they are very useful for identification and antigenic characterization of pathogens. Monoclonal antibodies have tremendous applications in the field of diagnostics, therapeutics and targeted drug delivery systems, not only for infectious diseases caused by bacteria, viruses and protozoa but also for cancer, metabolic and hormonal disorders. They are also used in the diagnosis of lymphoid and myeloid malignancies, tissue typing, enzyme linked immunosorbent assay, radio immunoassay, serotyping of microorganisms, immunological intervention with passive antibody, antiidiotype inhibition, or magic bullet therapy with cytotoxic agents coupled with anti mouse specific antibody. Recombinant deoxyribonucleic acid technology through genetic engineering has successfully led to the possibility of reconstruction of monoclonal antibodies viz. chimeric antibodies, humanized antibodies and complementarily determining region grafted antibodies and their enormous therapeutic use.

Serum-free hybridoma culture: ethical, scientific and safety considerations

Despite considerable progress in the development of cell culture techniques, including the development of the serum- and protein-free media that now routinely support hybridoma and mammalian cell growth, fetal bovine serum (FBS) supplemented media are still commonly used: a practice that raises ethical, scientific and safety concerns. The use of FBS in hybridoma culture media is examined here, with regards to the development and production of monoclonal antibodies (mAbs), and it is our recommendation that researchers adopt serum-free cell culture methods to reduce animal use in this area.

Hollow fiber bioreactor: New development for the study of contrast agent transport into hepatocytes by magnetic resonance imaging

The aim of our study was to develop a magnetic resonance (MR)-compatible in vitro model containing freshly isolated rat hepatocytes to study the transport of hepatobiliary contrast agents (CA) by MR imaging (MRI). We set up a perfusion system including a perfusion circuit, a heating device, an oxygenator, and a hollow fiber bioreactor (HFB). The role of the porosity and surface of the hollow fiber (HF) as well as the perfusate flow rate applied on the diffusion of CAs and O2 was determined. Hepatocytes were isolated and injected in the extracapillary space of the HFB (4 x 10(7) cells/mL). The hepatocyte HFB was perfused with an extracellular CA, gadopentetate dimeglumine (Gd-DTPA), and gadobenate dimeglumine (Gd-BOPTA), which also enters into hepatocytes. The HFB was imaged in the MR room using a dynamic T1-weighed sequence. No adsorption of CAs was detected in the perfusion system without hepatocytes. The use of a membrane with a high porosity (0.5 microm) and surface (420 cm2), and a high flow rate perfusion (100 mL/min) resulted in a rapid filling of the HFB with CAs. The cellular viability of hepatocytes in the HFB was greater than 85% and the O2 consumption was maintained over the experimental period. The kinetics of MR signal intensity (SI) clearly showed the different behavior of Gd-BOPTA that enters into hepatocytes and Gd-DTPA that remains extracellular. Thus, these results show that our newly developed in vitro model is an interesting tool to investigate the transport kinetics of hepatobiliary CAs by measuring the MR SI over time.

Long-term in vitro toxicity models: comparisons between a flow-cell bioreactor, a static-cell bioreactor and static cell cultures

In vitro long-term toxicity testing is becoming an important issue in the field of toxicology, and there is a need to develop new model systems that mimic human chronic exposure and its effects. The aim of this work was to test two long-term in vitro toxicity systems which are available, a flow-cell bioreactor (Tecnomouse, Integra, Wallisellen, Switzerland) and a static cell bioreactor system (CELLine CL 6-well, Integra), and to compare them with the use of conventional cell culture flasks. A human cell line, Int 407, was exposed to cadmium chloride (CdCl(2); 10-(7-)10-(8)M) for 4 weeks. Cell numbers and cell viabilities were determined by the trypan blue (TB) exclusion assay and from exclusion of propidium iodide (PI) as determined by flow cytometry; and cell viability and metabolic activity were determined by the MTT assay. In addition, total protein determination and cadmium uptake measurements were performed. The results obtained with TB and PI exclusion did not show clear differences in cell viability with increasing CdCl(2) concentration. However, in the static cell-culture systems, an increase in MTT reduction was found at low concentrations of CdCl(2). Expression of heat-shock protein (Hsp27 and Hsp70) increased differently, depending on the CdCl(2) concentration applied and the system used. In summary, of the two bioreactors, the CELLine CL 6-well bioreactor was shown to be the more efficient system for performing long-term cytotoxicity studies. It is easy to handle, it permits the assessment of several endpoints, and sufficient replicates can be made available.

Efficient laboratory-scale production of monoclonal antibodies using membrane-based high-density cell culture technology

Monoclonal antibodies (MAbs) are important tools used in basic research as well as in the imaging and therapy of cancer. Many countries have limited the use of animals for large-scale production of MAbs, obliging laboratories to find efficient in vitro alternatives to ascites production. In this report we describe a protocol for laboratory-scale production of MAbs by culturing hybridoma cells in the two-chamber cell culture device CELLine 1000. This culture flask supports high cell densities (10(7)-10(8) cells/ml) and generates high concentrations of MAbs (0.7-2.5 mg/ml). Two hybridomas producing MAbs directed against the gastrointestinal antigen GA733-2, GA733 MAb and CO17-1A MAb, were evaluated over culture periods of up to two months using several alternative conditions. Two different sets of conditions are reported; the first using serum-supplemented medium (20% v/v) and the second using serum-free medium (SFM). Average weekly yields of the purified MAbs in serum-supplemented medium were 24 mg and 33 mg, and in SFM were 21 mg and 17 mg for GA733 MAb and CO17-1A MAb, respectively. Experimental variables that can affect antibody production and economy include: nutrient medium and cell compartment medium compositions (cell line dependent), the proportion of the cell compartment medium harvested every 3 days (50% to 80% with 80% optimal) and the frequency of nutrient medium changes (3 to 9 days with 6 days as most cost effective). Protein-A Sepharose purification followed by antigen-specific affinity purification showed that MAbs obtained from serum-supplemented cultures contain less than 0.6% of bovine IgG contamination, while MAbs obtained from serum-free cultures contained no extraneous IgG. In addition, MAbs from both culture media were fully active (essentially 100%) as measured by their ability to bind to an antigen column. In contrast, the same MAbs purified from ascites using Protein-A-Sepharose typically contained a major portion of inactive IgG. This in vitro method for laboratory-scale production of MAbs (10 to 500 mg) proved to be simple, reproducible and cost effective. It represents a useful alternative to the in vivo production of MAbs in mice.