monoclonal antibody characterizationI’ve always been fascinated by the field of immunology and the immune system, probably explaining why I took a doctorate in immunology. Two areas that particularly interest me are how the immune system evolves and adapts to the challenges and stresses it faces, not just in the short term but over the long term as I discussed in a previous blog post, titled, Glycan Analysis with a Particular Focus on the Immune System, and how it puts in processes and checkpoints to ensure it only attacks foreign antigens rather than self.

 

Evolution of the Immune System

Our immune system has evolved over thousands of years in response to the increasing sophistication of antigens and our social development (for those with an interest in this area, I would really recommend this book by Laurie Garrett: The Coming Plague). We began with a relatively simple innate immune system which gave a good defense against basic types of pathogens, but was not very specific and did not give rise to immunological memory, that is, if the same pathogen attacked again the immune system would have to start afresh rather than calling upon previously used and stored defences.

Over time, though the attacks on the body became more sophisticated and diverse and in response the immune system developed to be able to deal with these new pathogens. That’s when we developed the humoral immune system consisting of lymphocytes (B- and T-cells and Natural Killer cells). This gave the immune system much more potent weapons that could identify, inhibit and ultimately kill invading pathogens or the cells they infected, but also offered immunological memory.

 

Role of Antibodies in the Human Body

B-cells are particularly interesting as one of their main roles is essentially as antibody factories and these antibodies have multiple roles in protecting the body:

  • Identifying foreign bodies and binding to them, effectively marking them for destruction by other cells in the immune system.
  • Binding to specific sites or receptors on pathogens to neutralize their activity and/or prevent binding and entry to cells.
  • Binding and activating receptors on infected cells or pathogens themselves to activate a process called programmed cell death or apoptosis.

Antibodies can do this as they each have a very specific binding capacity to a specific antigen or part of a pathogen. The immune system produces vast numbers of B-cells each day, with each B-Cell producing antibodies specific for one particular antigen. It then becomes just a numbers game; with such large numbers of antibodies there is always going to be one that is specific for a particular antigen.

As antibodies have such a powerful role in the immune system and are produced in such numbers and variety then surely they is an ever present danger that antibodies are produced that are specific to the cells of the body and can subsequently bring the immune system upon itself? Thankfully, the immune system has invented its own checkpoint to prevent this happening. During its development the immature B-cell, before it begins producing antibodies, is exposed to self antigens. At this stage, if the immature B-cell does recognize a self-antigen it undergoes apoptosis before it begins producing antibodies against self-antigens.

 

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Antibodies as Biopharmaceutical Drugs

Due to the fact that antibodies are so specific and are so effective at removing unwanted pathogens and/or infected cells, then they have become an attractive biopharmaceutical option. They can be used to eliminate pathogens, but commonly they are employed to neutralize an agent causing disease (for example, Humira which is an antibody against the cytokine TNFα which in excessive amounts contributes to rheumatoid arthritis) or to target abnormal cells within the body such as cancerous cells. However, the antibodies used as biopharmaceuticals are produced in vitro using cloning techniques and do not pass through the immune system’s sophisticated checkpoints to ensure they do not recognize self antigens.

Does that mean we are basically putting ourselves at risk with antibody biopharmaceuticals in that we are placing dangerous antibodies in our bodies that could explode in to life at any point and begin attacking our own healthy cells? Well no, not if we are performing the necessary analytical characterization and testing on the antibodies and treating them with the respect they deserve. To begin with, each antibody goes through exhaustive clinical trials to ensure that they are specific only to the target antigen and have no other specificity, however small, on non-target antigens.

 

Antibody Characterization and Testing Solutions

During the clinical trials and ongoing manufacture of the antibody, considerable testing is also performed to ensure the amino acid composition does not change or there are any changes in post-translational modifications (PTMs) or site of these PTMs. The technologies of choice for this antibody characterization are biocompatible UHPLC (Thermo Scientific Vanquish Flex UHPLC system) for separation and high resolution mass spectrometry (Thermo Scientific Q Exactive HF mass spectrometer) for detection.

An example of the use of these technologies for monoclonal antibody characterization can be seen in this new application note, titled, High-Throughput Peptide Mapping with the Vanquish UHPLC System and the Q Exactive HF Mass Spectrometer, (downloadable PDF), where fast peptide mapping was performed to obtain analytical information about correct sequence, glycosylation, and post-translational or artificial modification of recombinant monoclonal antibodies.

So in summary, antibodies are powerful weapons, developed by the immune system to meet the every changing challenges it faces. We can exploit these antibodies for our beneficial use, but in doing so we lose some of the checks and controls the immune system enforces that we have to replace with our own stringent analytical controls.

 

Additional Resources

 

Do you have any concerns about using antibodies as biopharmaceuticals? Is the industry moving away from antibodies to other biomolecules as biopharmaceuticals ? I would like to hear your views and comments.