IntroductionSince the early 1990s, recombinant human clotting factor VIII (rhFVIII) produced in hamster cells has been available for haemophilia A treatment. However, the post-translational modifications of these proteins are not identical to those of native human FVIII, which may lead to immunogenic reactions and the development of inhibitors against rhFVIII. For the first time, rhFVIII produced in a human host cell line is available.AimWe describe here the establishment of the first human production cell line for rhFVIII and the manufacturing process of this novel product.Methods and resultsA human cell line expressing rhFVIII was derived from human embryonic kidney (HEK) 293 F cells transfected with an FVIII expression plasmid. No virus or virus-like particles could be detected following extensive testing. The stringently controlled production process is completely free from added materials of animal or human origin. Multistep purification employing a combination of filtration and chromatography steps ensures the efficient removal of impurities. Solvent/detergent treatment and a 20 nm pore size nanofiltration step, used for the first time in rhFVIII manufacturing, efficiently eliminate any hypothetically present viruses. In contrast to hamster cell-derived products, this rhFVIII product does not contain hamster-like epitopes, which might be expected to be immunogenic.ConclusionsHEK 293 F cells, whose parental cell line HEK 293 has been used by researchers for decades, are a suitable production cell line for rhFVIII and will help avoid immunogenic epitopes. A modern manufacturing process has been developed to ensure the highest level of purity and pathogen safety.

No abstract

The glutamine metabolism was studied in glucose‐starved and glucose‐sufficient hybridoma and Sp2/0‐Ag14 myeloma cells. Glucose starvation was attained by cultivating the hybridoma cells with fructose instead of glucose, and the myeloma cells with a low initial glucose concentration which was rapidly exhausted. Glutamine used in the experiments was labeled with 15N, either in the amine or in the amide position. The fate of the label was monitored by 1H/15N NMR analysis of released 15NH 4+ and 15N‐alanine. Thus, NH 4+ formed via glutaminase (GLNase) could be distinguished from NH 4+ formed via glutamate dehydrogenase (GDH). In the glucose‐sufficient cells a small but measurable amount of 15NH 4+ released by GDH could be detected in both cell lines (0.75 and 0.31 μmole/106 cells for hybridoma and myeloma cells, respectively). The uptake of glutamine and the total production of NH 4+ was significantly increased in both fructose‐grown hybridoma and glucose‐starved myeloma cells, as compared to the glucose‐sufficient cells. The increased NH 4+ production was due to an increased throughput via GLNase (1.6 –1.9‐fold in the hybridoma, and 2.7‐fold in the myeloma cell line) and an even further increased metabolism via GDH (4.8–7.9‐fold in the hybridoma cells, and 3.1‐fold in the myeloma cells). The data indicate that both GLNase and GDH are down‐regulated when glucose is in excess, but up‐regulated in glucose‐starved cells. It was calculated that the maximum potential ATP production from glutamine could increase by 35–40 % in the fructose‐grown hybridoma cells, mainly due to the increased metabolism via GDH. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 508–517, 1998.

Ammonium can be transported into the cell by ion pumps in the cytoplasmic membrane. Ammonia then diffuse out through the cell membrane. A futile cycle is created that results in cytoplasmic acidification and extracellular alkalinisation. Ammonium transport can be quantified by measuring the extracellular pH changes occurring in a cell suspension (in PBS) after addition of ammonium. By using this technique, in combination with specific inhibitors of various ion pumps, it was shown that ammonium ions are transported across the cytoplasmic membrane by the Na(+)K(+)2Cl(-)-cotransporter in both hybridoma and myeloma cells. Further, the Na(+)/H(+) exchanger, which regulates intracellular pH by pumping out protons, was shown to be active during ammonium exposure. The viability of hybridoma cells suspended in PBS and exposed to NH (inf4) (sup+) for only 90 min, was reduced by 11% (50% necrosis and 50% apoptosis). A control cell suspension did not loose viability during this time. Turning off the activity of the Na(+)/H(+) exchanger (by amiloride) during ammonium exposure decreased viability further, while inhibiting transport itself (by bumetanide) restored viability to the same level as for the control experiment with bumetanide alone. These results show that one effect of ammonia/ammonium on cell physiology is specifically related to the inward transport of ammonium ions by membrane bound ion pumps.

No abstract