Why Choose Rabbit Monoclonal Antibodies?

Since 1980, murine monoclonal antibodies have dominated the industry; however, the importance of rabbits, especially Oryctolagus cuniculus (also known as European rabbits), as immunology models has led to their consideration as a more suitable source of monoclonal antibodies. This leads to the question, why choose rabbit monoclonal antibodies when mice antibodies are already available? Supported by evidence, rabbits show significant advantages, including a broader repertoire, simpler structure, higher binding affinity, robust reproduction, and easy humanization (Feng et al., 2011).

One of the main reasons rabbit antibodies are becoming the top choice is due to their common use in immunology for over a century. It is possible to find established standard procedures and vast information on rabbit antibodies’ characteristics. For example, the most abundant class in rabbit serum is a single IgG subclass (no subtypes), and its simple structure facilitates molecular cloning and engineering (Feng et al., 2011). IgG’s simpler structure in rabbits is also impactful for custom rabbit monoclonal antibody (mAb) therapeutics because this is the only class of antibodies used for its low immunogenicity pharmacokinetics, stability, and limited toxicity profiles. Moreover, this represents an advantage over mice monoclonal antibodies where IgM, a less specific isotype, is the predominant immunoglobulin. 

Rabbit antibodies can recognize epitopes on human antigens that are not immunogenic in rodents, which enables targeting a larger number of epitopes (Weber et al., 2017). This allows high affinity over a more extensive range of epitomes with minimal or no nonspecific interactions. Additionally, this presents an opportunity for creating a robust monoclonal antibody library.

Compared to other rodents, rabbits produce more robust immune responses against small molecules and haptens, and scarce inbred rabbit strains provide a more diverse immune response (Weber et al., 2017). The rabbit immune system offers an evolutionary advantage over other rodents through its various mechanisms to optimize, diversify and generate antibodies (Chu et al., 2020). This is a natural consequence of rabbits belonging to the order Lagomorpha, a different evolutionary order than Rodentia, to which mice and rats belong (Weber, 2017). In humans and mice, the antibody repertoire is created by the combinational joint of multiple gene segments from both light and heavy chains. In rabbits, this primary antibody repertoire occurs the same; however, an added secondary conversion-like mechanism occurs (Feng et al., 2011). Therefore, rabbit monoclonal antibodies have an added advantage in ensuring antibody diversity. 

Usually, the generation of monoclonal antibodies is based on the recovery of B cells from the spleen, blood, or bone marrow. In the case of rabbit antibody production, the larger body size of rabbits in comparison to mice indicates higher quantities of product can be obtained from rabbits. This size difference facilitates the mass spectrometry analysis of bulk serum IgG and the possibility of creating hundreds of hybridomas from each immunized spleen (Weber et al., 2017).

Moreover, as immunotherapeutic agents, rabbit monoclonal antibodies present a more significant serum half-life and reduced immunogenicity due to their ability to be easily humanized to reduce animal contents (Rashidian & Lloyd, 2020). Previous research has shown that humanization in rabbits using the methods already established for mice monoclonal antibodies increased the sensitivity and biophysical properties without losing specificity or affinity (Zhang et al., 2017). These characteristics made them suitable for humans as they will present a more standing effect while maintaining safety and functionality.

Currently, mAbs are widely used for different goals; examples include their use as a treatment against human diseases such as cancer and autoimmune diseases, as diagnostic tools in clinical settings, and as targeted drug delivery systems for infectious diseases and metabolic and hormonal diseases (Rashidian & Lloyd, 2020; Weber et al., 2017). This is reflected in the 230 clinical studies on mAbs evaluated by the Food and Drug Administration in early 2017 and the approbation of some of them, including the rabbit anti-human PD-L1 mAbs used to detect PD-L1 expression in cancer (Mage et al., 2019; Zhang et al., 2017).

This trend is justified by how monoclonal antibodies contain a paratope, meaning they have a defined antigen-binding site that usually binds with only one epitope. Being this highly affine and specific, monoclonal antibodies are produced by a single B cell clone and present a homologous antibody population (Rashidian & Lloyd, 2020; Weber et al., 2017). Considering these properties, the molecularly defined form of mAbs make them more suitable to reproduce as a pharmaceutical product. In other words, the production of monoclonal antibodies is an excellent example of personalized therapies; their high specificity for antigens or molecules can be tailored in the laboratory, leading to custom rabbit monoclonal antibodies.

Boster Bio provides custom antibody production and development services for rabbit monoclonal antibodies. After rabbit immunization, plasma cell isolation, cloning and expression, and screening and selection, they can deliver purified antibodies characterized for a specific application. Traditionally, hybridoma screening and phage display are considered the main strategies to produce antibodies; however, these strategies present several downsides. For example, in hybridomas’ case, the efficiency of cell fusion is low, reducing the repertoire’s diversity; moreover, the need to grow them in culture media increases the risk of contamination and is time-consuming (Rashidian & Lloyd, 2020).

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Meanwhile, phase display can result in the loss of chains and instability. To overcome this, Boster Bio works with plasma-cell discovery (PCD) technology which has the capacity to screen 100 to 1000 times more clones, leading to the best chances of finding the clones with the highest affinity. Additional advantages of this approach include antibody repertoire preservation, higher stability and specificity, and a lower risk of contamination (Rashidian & Lloyd, 2020).  Therefore, when dealing with complex targets, Boster Bio’s custom rabbit monoclonal antibody development services are suitable for ensuring the highest affinity and specificity tailored for the researcher’s desired functionality.