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The body produces them in masses during an infectious disease. They are able to bind to specific surface structures of bacteria and viruses, dock themselves to them and mark the disease trigger for depletion. Antibodies are small wonder weapons that the body uses to protect itself. They also play an important role outside the body. Antibodies are routinely used in biomedical diagnostics and therapy. Producing them, however, is time-consuming and expensive. Potsdam biologists want to simplify the procedure.
Flat culture flasks, Petri dishes, and microplates filled with orange and red liquids are stacked in the culture cabinet of cell biology laboratories. Katja Hanack takes a vial from the incubator and places it under the microscope. Millions of tiny cells are swimming in the nutrient fluid, invisible to the human eye. Only at a 10-20x magnification do the small transparent spheres become visible. They produce the precious cargo the biologist is looking for: antibodies. The immune cells had to go through a complicated process before becoming small antibody factories in the laboratory culture.
Katja Hanack is Professor of Immunotechnology. She and her research group are developing a system that will enable the production of highly coveted antibodies in cell cultures, much faster and cheaper than this has been done so far. The demand for these small connecting particles is immense in medicine and industry.
“Antibodies are the most commonly used binding molecules,” the scientist explains. “They are virtually everywhere in diagnostics and therapy.” Pregnancy hormones, viruses, tumor proteins, and pharmaceuticals can be detected in the blood with the help of antibodies. Tests for diabetes and autoimmune diseases are also based on the binding ability of the molecules. Certain cancers and inflammatory reactions from rheumatism or Crohn's disease are treated with antibodies.
“The vast amount of antibodies has to be produced somehow,” explains Hanack, who was the head of the InnoProfile Research Group “Antibody Technologies” at the University of Potsdam until recently and now holds an endowed professorship. “This means an immense expenditure of effort, which requires a lot of time and material.” Antibodies have usually been prepared by injecting animals – usually mice – with an exogenous substance, a viral particle, a bacterium, or some other substances. Experts call these foreign substances “antigens”. The animal’s immune system recognizes the e exogenous substances triggering an immune response that produces an antibody specific to the antigen. The animal’s spleen is then removed and the antibody-producing cells in the spleen are isolated. “The spleen cell repertoire of a mouse produces millions of different antibodies,” Hanack explains. Further immunological tests are needed to isolate the cell that produces the desired antibody. “The entire procedure usually takes six to eight months," explains the researcher.
The young professor has set herself an ambitious goal: Producing antibodies in a single month rather than six to eight. And fewer mice will have to lose their lives. In a cell culture, she reconstructs what happens in the animal or human body during an immune response – from the antigens’ initial contact with the immune cells to the production of specific antibodies. These are released by the cells into the medium, where they can be "harvested". The procedure would make removing the animal’s spleen unnecessary. Immune cells from the blood then cultivated in the laboratory would suffice. In addition, human antibodies, which have had to be “humanized” from mouse antibodies in an elaborate process for them to be usable for therapeutic purposes, could be produced much more easily with human cell cultures.
“This looks good.” Hanack is pleased with what she sees on the monitor of her assistant Monique Butze, who is examining llama immune cells isolated from their blood and cultivated in the lab. On the screen are blob-shaped cells with long extensions; these “dendritic cells” recognize foreign substances such as viruses and bacteria in the body, eat them, and dissolve them. This is the body’s first step in its immune response and the starting point for establishing antibody production in a cell culture.
Dendritic cells are the “sentinels of the immune system”. They present characteristic parts of previously absorbed and dissolved foreign matter on their own cell surface. This is the signal to other immune cells – T-lymphocytes: “Look, this is what the enemy looks like.” Once T-lymphocytes have registered the information, they function as a messenger, passing the information on to other immune cells – B-lymphocytes. They eventually produce specific antibodies that dock to the surface structures of the invaders and render them harmless. “That's our goal,” explains Hanack.
An initial success for Hanack and her team has been that the dendritic llama cell, isolated from a llama blood sample and replicated in a cell culture, are now active and functional. Their next step is to add a specific antigen to a cell culture, i.e. the protein to which the antibody will later attach. When the dendritic cells present the structures of the antigens on their cell surface, they are also detected by the added T-lymphocytes. The Potsdam scientists are breaking new ground with their research on how llamas and camels produce camelid antibodies. While conventional antibodies are Y-shaped with two heavy and two light molecule chains and can only stably bind to an antigen with both arms, some camelid antibodies have only two heavy chains, which nevertheless bind to the antigen very stably. Such features simplify their handling and are ideal for industrial use.
“Camelid antibodies are extremely stable; they can be heated to 90 degrees Celsius and they are still fully functional after refolding,” explains Hanack. Their enormous heat stability is probably a result of their adaptation to the high ambient temperatures at home. In addition, camelid heavy-chain-only antibodies are smaller and more soluble. You can penetrate the tissue much more deeply and thus bind antigens unreachable to conventional antibodies.
So far, however, there has been no method of cultivating camelid immune cells. What reagents can the cells tolerate? What nutrients do they need? What environmental conditions can they tolerate? Researchers have to answer these questions through elaborate test series. If successful, they will then have to develop “cell lines”. Those cells that produce the desired antibodies will be selected but would, however, survive in the cell culture for only a few days, which is why the researchers fuse them with cancer cells. The resulting cells – “hybridomas” – continue producing antibodies but are simultaneously immortal since they take on cancer cells’ ability to divide indefinitely. This process has already become a standard for antibodies derived from mice but has yet to be developed for camelid antibodies.
Hanack and her research team are currently working on two fronts – researching antibody-producing cell cultures and establishing camelid antibodies for application. “We want to develop a standard technology for camelid antibodies as has been done for mouse antibodies,” clarifies Hanack. The researchers ultimately want to simplify procedures and novel binding molecules for medicine and industry.
Once a cell line has firmly established itself, it can produce virtually an unlimited number of antibodies. For the camelid antibody this is still some way off given the number of hurdles yet to be overcome. The researchers need a lot of patience when, for example, the one immune cell with the right antibody happens to not be among the thousand examined. Hanack keeps her “treasures” at icy temperatures: Selected cell lines are transferred into a “deep sleep” in large steel tanks at -200 degrees Celsius and can remain in this state for decades. Once the antibody is needed, the cells are thawed and ready for use.
Prof. Katja Hanack studied biology in Rostock and Berlin. She earned her doctorate at the University of Potsdam and was head of the junior research group “Antibody Technologies”. Since 2015 she has been an endowed professor of immunotechnology. The endowed chair is co-financed by the Federal Ministry of Education and Research and eight regional biotech companies.
Institut für Biochemie und Biologie
Karl-Liebknecht-Str. 24–25, 14476 Potsdam
Text: Heike Kampe
Online gestellt: Matthias Zimmermann
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