Current medicine would not exist without monoclonal antibodies (and without experimental animals)

One of the allies we have had during the pandemic has been monoclonal antibodies, some generated to recognize the virus in diagnostic techniques and others for therapeutic and preventive use (neutralize the virus).

In most cases, to obtain them it has been necessary to resort to hybridoma technology with experimental animals, created more than 45 years ago. Something that contradicts the recommendation launched by the European Commission in 2020 and that urged to stop using experimental animals for the development of monoclonal antibodies. As discussed below, we believe that this recommendation is premature and may cause significant damage, both in research and therapeutics.

A hybrid cell with “super powers”

It was 1975 when researchers César Milstein and Georges Köhler, from the Medical Research Council of Cambridge, published in the journal Nature an article that would change Immunology forever. Not only that: it also marked a before and after for many other areas of knowledge, especially for Medicine.

What that article described was a novel technique that made it possible to obtain an antibody directed against a specific target in large quantities. That is, a monoclonal antibody.

The technique in question made it possible to generate a new hybrid cell from two others: a specific B lymphocyte and a tumor plasma cell (myeloma). The hybrid cell (or hybridoma) is capable of secreting large amounts of antibody in culture. It can also be grown for long periods of time, kept frozen, and thawed when needed. All advantages, in short.

And what is it for? Well, imagine that we want an antibody that recognizes and neutralizes the SARS-CoV-2 virus. The hybridoma technology procedure consists of vaccinating an animal (usually a mouse or rat) several times with elements of the virus (protein S) to subsequently obtain its B lymphocytes (from the spleen, lymph nodes, etc.).

Once extracted, the B lymphocytes are fused in the laboratory with the myeloma lineage and all the rest of the antibody production procedure continues in the laboratory. This is how, from a single animal, several different hybridomas and monoclonal antibodies against the virus can be obtained.

The technique was not patented by the institute where Milstein and Köhler worked, which has allowed many research groups to develop and patent their own antibodies (which can be patented individually). Current research in many fields related to biomedicine could not be carried out without the help of these monoclonal antibodies.

Multipurpose monoclonal antibodies

In addition, monoclonal antibodies are used in Medicine as passive immunization in disease prevention (for example, neutralizing viruses), in diagnostic techniques (quantifying hormones, studying leukemias and tumors, identifying pathogens, evaluating prognosis according to tumor type, etc.) and in the purification of compounds (coagulation factors, interferon…). But where they really stand out is in therapies.

Specifically, monoclonal antibodies have been used successfully for many years to treat cancer, which is usually unified under the term immunotherapy. They are also useful against autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus or Crohn’s disease. Likewise, monoclonal antibodies have been used against allergies, macular degeneration, hypercholesterolemia, osteoporosis and a long etcetera.

Today, in the therapeutic arsenal there are more than 500 authorized monoclonal antibodies or in different clinical phases. Most of them have been obtained according to the original technique, although they can be improved by molecular biology and genetic engineering techniques, to make them more compatible with human beings.

Obtaining monoclonal antibodies from hybridoma technology has many advantages. When obtained after carrying out a specific immunization, the animal itself can improve the response, obtaining antibodies with high affinity and very specific. These two aspects are essential in the activity of the antibody. As if that were not enough, it is a simple and relatively cheap technique, which allows many research groups to carry it out.

From the outset, it requires the collaboration of an animal bioexperimentation service for the initial immunization process. But then the whole process is done in vitro without requiring more experimental animals. Different animal models can be used, especially mice and rats, but also others such as llamas –which have the peculiarity of producing smaller antibodies (nanobodies)–, hamsters, chickens, etc.

Based on this technique, which is still completely valid, necessary and used by many researchers, alternatives have been designed that are not yet optimal for all applications. These include the use of viruses that infect bacteria (bacteriophages) and the creation of phage libraries, human B lymphocytes from donors, or the design of genetically modified animal models to produce fully human antibodies.

This is not the time to give up experimental animals

It seems indisputable that the technology for generating hybridomas using animal models is more alive than ever, without this preventing progress in the development of alternative methods. However, leaving behind the generation of hybridomas before alternative technologies are sufficiently developed and implemented can lead to significant harm, both in research and therapeutics.

This comment is related to the recommendation that, as we already mentioned, we consider premature, and that was launched by the European Commission in May 2020, through the ECVAM committee (European Reference Center for the Validation of Alternative Methods). It established that it was no longer necessary to continue using experimental animals for the development of monoclonal antibodies. And also that their generation through the aforementioned phage libraries made it possible to obtain monoclonal antibodies for all their applications without the participation of animals.

Unfortunately, science confirms that we are not yet in that circumstance. Monoclonal antibodies obtained by alternative methods do not always have the quality, affinity, or diversity that can still be obtained with the hybridoma technique, from the limited use of animals in the initial phases of the protocol.

Additionally, resorting to these alternative technologies is much more sophisticated, expensive and difficult to access for most laboratories. For all these reasons, the method originally established by Milstein and Köhler in 1975, hybridoma technology, is still valid and necessary today.

In conclusion, thanks to monoclonal antibodies, and specifically to the hybridoma generation technique, great advances have been made in Medicine. It is advisable to be very cautious and responsible when approaching a transition from conventional methods to alternative methods, to ensure that we do not miss out on any of the great benefits that the former have brought.