Thorough fusion screening and clone selection are crucial to an efficient, successful hybridoma program. Traditional screening and clone selection is both time and labor intensive. In addition there are limitations in the number of clones that can be screened, which means that you have fewer clones to choose from when selecting your final cell line. The traditional process begins with fusion screening and confirming positives, then moves to limited dilution in single cell wells. Limited dilution is the most labor intensive part of the process and also poses a risk to scientists through repetitive movement injury. Lastly clones are selected. The entire process can take 30-45 days.Many people already use automated screening and clone selection systems with CHO cell line development, where more investment is made in selecting a cell line because the line may ultimately be used in commercial manufacturing. However, there is a good argument for using these systems with hybridoma cells. These systems allow the overall process from fusion to clone selection to be accomplished much faster; some have reported a greater than 50% reduction. This time savings allows companies to cut overall drug discovery time and get to clinic faster. In addition using these systems can increase antibody yield, thus increasing process efficiency. By automating much of the process, it also frees up scientists to work on other projects.
In most automated systems cells are grown as a discrete colony in semi-solid media. Using semi-solid media offers some advantages over liquid media. First it improves the probability of monoclonality. Another advantage is that in liquid media you have a mix of fast growing and slow growing cells. Eventually the fast growing cells take over the culture and usually the fast growing cells are not the best producers. This leaves fewer slow growing cells to screen for a high producer. In semi-solid media you do not have a takeover of the culture by fast growing cells and this presents more opportunity to find that elusive high antibody yield clone. In addition cells grown in liquid media have a low survival rate when moved to 96 well plates, while cells grown in semi-solid media do much better. This means with semi-solid media fewer plates have to be cultured overall.
Another key feature of the automated system is the software that when coupled with the machine’s imaging system, allows scientists to program the criteria for the cells they would like to select. For example, scientists can input one set of criteria when screening for fusions and a different set when conducting clone selection. The machine then identifies which cells meet the set criteria. This is a big time saver because as soon as the colony does not meet the criteria they can be eliminated and time is not wasted on colonies that ultimately won’t be selected. Another plus is that limited dilution is completely eliminated, thus saving time and reducing probability of worker injury. Automating the system also enables high throughput so more clones can be screened overall, which increases the probability of finding a high antibody yield clone.
There are different automated systems available for use in hybridoma production including the ClonePix System by Molecular Devices (formerly Genetix), which is a very popular system in CHO cell line development. Molecular Devices offers some excellent webinars about their ClonePix System on their website. Other systems include the Cello system by Tap Biosystems (formerly The Automation Partnership) and the ClonaCell EasyPick System by Stemcell Technologies.
Stemcell Technologies’ ClonaCell EasyPick System is interesting in that they have invested significant resources into the semi-solid media portion of the system. This makes sense considering that they were founded almost 20 years ago with Methocult, a methylcellulose based semi-solid media used for hematopoietic stem cells. In 1995 they launched their ClonaCell line of products all based on the use of methylcellulose semi-solid media. They have joined their ClonaCell media with EasyPick, an automated system manufactured in partnership with Hamilton robotics. The partnership conveys both the benefits of their media coupled with the high throughput of an automated system. John Chen, Product Manager, Cell Line Development & Primary Cells, Stemcell Technologies said, “We sell to all the big biopharmaceutical companies in the world and we asked our top customers what ClonaCell means to them, they tell us that it is simply the smart way to find the right clone.”
While many companies have already implemented these systems in CHO cell line production, it is not as widespread for
hybridoma use. I believe these systems deserve a second look in hybridoma production, since there are clear advantages to implementing an automated system including reduced drug discovery time, improved antibody yield and increased overall efficiency.
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