The expanding role of rabbit mAbs in research

Monoclonal antibodies (mAbs) can achieve unparalleled affinity and specificity for a wide range of biomolecules, making the reagents critical to both basic and clinical research. The vast majority of mAbs are derived from mice, the most widely-used and best understood mammalian species for laboratory work. However, a new, non-peer-reviewed white paper from GenScript explains how rabbits can serve as a resource for generating superior mAbs.

Rabbit antibodies have a number of advantages over traditional mouse antibodies. A simpler protein structure makes them more stable than their rodent counterparts, which translates into greater longevity and robustness over the course of experiments. Rabbit B-cells undergo a more sophisticated maturation process than occurs in mice, allowing them to produce mAbs that recognize a greater diversity of targets. The rabbit’s immune system is also highly responsive to targets that are only weakly immunogenic in mice, such as carbohydrates and small-molecule drugs, making it possible to generate potent and specific mAbs for these classes of biomolecules. Furthermore, there is greater evolutionary distance between rabbits and humans, so there is less similarity between proteins from these two species. As a result, rabbits may produce antibodies against human protein targets that would be ignored by the mouse immune system.

GenScript’s proprietary MonoRab^TM platform offers the means to reliably generate rabbit mAbs against a diverse array of molecular targets. First, rabbits are repeatedly inoculated with the antigen of interest, in order to stimulate activation and proliferation of B-cells that produce antibodies against that target. These B-cells are harvested and fused with continuously-dividing, mouse-derived tumor cell lines to generate ‘hetero-hybridomas’. A careful screening process identifies hybridomas that produce antibodies with optimal specificity and affinity for their target. The company then sequences selected hybridomas and performs recombinant expression in order to generate larger amounts of highly pure antibodies. GenScript is one of the only companies that commercially manufactures hybridoma-derived rabbit mAbs as a service for researchers.

Since the rabbit’s B-cell maturation process produces such a diverse range of antibodies, a rabbit hybridoma screen is more likely to give rise to mAbs that bind their targets strongly and selectively than those from mice. This means researchers can perform molecular detection assays such as immunohistochemistry or western blots with smaller amounts of antibody, reducing the potential of signal-obfuscating noise and increasing the likelihood of detecting or purifying scarce targets. GenScript scientists demonstrated that they can achieve more sensitive detection of epitope-tagged proteins with rabbit mAbs than with commercially-available mouse antibodies, which the company also produces.

MonoRab^TM can also generate effective reagents for pharmaceutical research. Many current cancer therapies are based on antibodies, and it is useful to understand what proportion of an antibody drug binds to its target in patients. GenScript developed one such rabbit mAb, which appears to bind to the therapeutic antibody pembrolizumab more strongly and stably than existing mouse-derived antibodies. Such antibody-specific ‘anti-idiotype’ mAbs can be a powerful tool for both detecting and modulating the activity of antibody drugs, and the MonoRab^TM platform is optimized for the production of such reagents.

GenScript has also manufactured rabbit mAbs with excellent affinity and specificity for small-molecule drugs—a class of targets that often fails to elicit a meaningful immune response in mice. In a trial, one of these mAbs bound strongly to the veterinary drug, ractopamine, without recognizing two close structural relatives, salbutamol and clenbuterol, highlighting the excellent specificity that can be achieved.

Mouse antibodies have been a critical driver of the molecular biology revolution, but they can also be frustrating to generate and have been plagued with reproducibility issues—indeed, some experts believe that more than half of commercial antibodies may be compromised by poor specificity. Rabbit-derived mAbs expand the toolbox for researchers, putting stable and high-specificity antibodies within easy reach.

For more information on rabbit mAbs, along with unpublished case studies from GenScript, read the white paper here.