Antibodies by Design (AbD) is a relatively new, custom antibody service offered by the German company, Morphosys. This service relies on their HuCAL Gold library, a set of 15 billion recombinant human Fab genes. Given as little as 0.5 mg of purified protein, they will screen this library in a completely animal-free system to find clones that bind to your antigen. This in vitrosystem allows them to do some neat tricks. For instance, poor immunogenicity of your antigen may not be a problem for them. Also, AbD can presorb the library against a control protein; a common use for this would be to remove antibodies that react with an irrelevant protein containing identical epitope tags. I imagine that another application of this would be in the production of polymorphism-specific antibodies. One could presorb the library against a wild-type protein, and then pull out clones specific for a mutant form.
Prior to using AbD, we had attempted to obtain a rat monoclonal against our immunogenic mouse receptor protein, only to spend a lot of money on failed results. We then decided to give AbD a shot and sent 0.5 mg of our purified protein overseas to AbD’s facility. Within weeks, we were informed that 7 clones had been pulled out of their library and were reactive by ELISA. AbD sent us the ELISA data and about 100μg of each of the antibodies, which I screened by fluorescence activated cell sorting and Western blot. Four of the antibodies were non-reactive to cell-expressed protein by flow cytometry (were likely directed against the epitope tags on my recombinant protein), while the other three antibodies had high specific binding activity, one of which, to our delight, cross-reacted with both the human and mouse forms of the protein. None of the antibodies were useful in Western blots, though I had only provided enough antigen to screen against the native protein. AbD is also capable of screening against denatured proteins, a practice that may have been more successful in yielding Western reagents.
In addition to the advantage of being well-suited for use with minimally immunogenic proteins, a nice feature of the recombinant format is that it allows the production of Fabs containing a variety of epitope tags. The default one provided to me by AbD had myc and 6xHis tags, but others are available, and I got the impression that they would be willing to work with me if I had some odd tag requirement. Antibodies can be provided in a bivalent format upon request, potentially boosting detection sensitivity. Finally, the lack of Fc region on reagents was a boon, as we frequently stain immune cells and FcR-mediated background signal was eliminated using these Fabs.
AbD also offers some additional services on both the front and back ends of the process. For instance, you can provide AbD with only the DNA for your protein and they will express and purify it for you. I did not avail myself of this service, so I can’t comment on its cost or effectiveness, but this might be a good option in some cases. On the other end of production, they can do an affinity maturation of a reactive clone by swapping CDR regions. This might be useful if your affinity is not quite high enough and illustrates another advantage of the recombinant in vitro technology.
Given the unusual format of the reagents, I was afraid detection protocol optimization might be a problem. However, AbD has already done considerable work in this area and they provide protocols with complete reagent lists for ELISA, Western blot, immunohistochemistry, FACS, and immunoprecipitation. We found that the FACS and IHC protocols worked very well without modification.
Finally, the customer service was superb. This was especially appreciated given that I am in the US and they are in Germany. Due to the excellent communication, this overseas divide did not pose an issue other that the usual annoyances of having to ship materials internationally.
Probably the biggest drawback to their service, as compared to hybridoma production, is that you are forever dependent on AbD to produce the antibody for you. The cost for antibody production is not cheap, but it is not odious either, especially if you order a lot at once to minimize setup charges. The initial screening costs are also high, but AbD gives you the benefits of rapid turnaround and the flexible Fab format, while guaranteeing ELISA-reactive clones or no charge for the service. This is comforting if you’ve had non-productive hybridoma experiences, as I have.
Overall, I am very satisfied with AbD’s product and found it to be worth the cost. I give them a high recommendation and plan to use them again.
Damon R. Asher, PhD
Post-doctoral Researcher
University of Massachusetts Medical School
'Antibodies by Design' custom antibody service is now part of Bio-Rad antibodies division, having been acquired in 2013