In a previous blog “Strategies for Improving Antibody Production in Hybridoma Cells” three areas were identified where antibody production can be improved. In part one of the series titled “Utilizing Automated Clone Selection to Improve Antibody Production in Hybridoma Cells,” we looked at automated clone selection as a way to increase efficiency and improve the quality of clone selected. In part two of the series titled “Advancing Media to Improve Antibody Production in Hybridoma Cells,” we examined new media supplements and the benefits of animal-free culture. In part three we will look at the role bioreactors can play in saving time and improving yield.
There are two main areas where hybridoma cells are commonly used to manufacture antibodies, biopharmaceutical drug discovery and antibodies sold for research and diagnostics markets. In both situations there is a need to produce several different antibodies as quickly and efficiently as possible. In drug discovery, it is necessary to produce gram amounts of antibody quickly for proof of concept, toxicology and animal studies. These initial studies are critical to an early go/no go decision. Saving time and allowing promising candidates to move forward rapidly reduces the overall drug discovery timeline and ultimately research and development costs. In antibody manufacturing for research and diagnostics is it is important to keep manufacturing costs down so efficient production is key. Improving antibody yield and reducing culture time, labor, and capital investment are all important factors in improving the bottom line.
Traditionally T-flasks or shake flasks have been used to produce antibodies in hybridoma culture. Advantages for flask culture are that they are simple to use, inexpensive, and easy to set up. The main disadvantage is that they don’t allow for manipulation of culture variables. Cell culture conditions such as nutrient concentration, ph, oxygen, CO2 and waste levels are difficult to control and as a result cells in flasks do not reach their full productivity potential. Often cells will use up nutrients early in the run and will accumulate waste product in the culture, compromising cell health and viability. Consequently flask culture results in lower cell densities and antibody yield when compared with other systems.
Other systems have started to replace flasks in hybridoma production. Each system has its advantages and disadvantages, but universally they obtain higher cell densities and antibody yield. One type of culture system increasing in popularity is the perfusion bioreactor. Perfusion bioreactors culture cells over much longer periods than flasks, even months, by continuously feeding the cells with fresh media and removing spent media. Antibody is also harvested and purified regularly, which improves antibody quality and allows for the production of unstable antibodies. Perfusion bioreactors operate at significantly higher concentrations and allow maximum control over culture conditions including nutrient, ph, gas and waste levels. The primary disadvantages stated with these systems are higher capital and media costs plus a learning curve that temporarily reduces employee productivity resulting in higher upfront cost. However, proponents argue that significantly higher antibody yield offsets initial investment and increased media use.
The GE Wave Bioreactor, which consists of disposable bags that lie on a rocking bed has been a very popular choice for hybridoma culture. The rocking motion allows for media to mix and provides enhanced delivery of media components to the cells. It also provides for better transfer of gases and prevents the cells from sitting on the bottom so they are truly in a state of suspension. It has the added flexibility of being able to function as a traditional harvest/fill culture or as a perfusion system.
Another type of perfusion bioreactor is a hollow fiber system. This system keeps the cells in the bioreactor by binding the cells to capillary fibers. For example, Spectrum Lab’s Cellmax artificial capillary system has a cartridge with capillary tubes that is fitted to a one liter media bottle. The cartridge allows for monitoring of glucose levels that can be checked regularly as an indicator of cell health. The cartridge can be tapped every couple days to allow for replenishing/removing media and harvesting product. Literature states that they can produce 5-50mg of antibody per harvest.
An Alternative option is a system like Integra’s disposable CELLine, which is a flask system that requires no additional hardware, but allows much of the same functionality of a bioreactor in terms of control of ph, nutrients, gases, etc. The system has a membrane that separates the cells from the media above with oxygen and CO2 diffused through the bottom of the flask. They have reported similar cell densities and antibody yield to bioreactor systems and the system is more affordable than most bioreactor systems.
To summarize, there are many advantages to using bioreactors in hybridoma culture including better control of culture conditions that results in higher cell densities, increased antibody yield and ultimately fewer runs needed to manufacture desired amount of antibody. However, these benefits come with a price and often that is the biggest disadvantage stated with these systems – the set up cost and learning curve involved in switching to a bioreactor system from flasks. Perfusion systems also have the added cost of using more media.