Genetically Engineered Livestock
Bringing 21st Century Medicines to the Developing World
William H. Velander
Distinguished Scholar and Fellow
Department of Chemical and Biomolecular Engineering
College of Engineering University of Nebraska - Lincoln
About the Lecture
The production of biopharmaceuticals in the milk of genetically engineered livestock enables a more than 200-fold increase in productivity over current methods of culturing animal cells in stainless steel bioreactors. This is due to the secretory architecture of the mammary gland and its sophisticated biochemistry for protein modification.
The genetic engineering of livestock began in the 1980s when it was shown that recombinant DNA microinjected into mouse embryos could be integrated into chromosomes by a natural gene repair process. “Transgenes” were then designed to express recombinant proteins in mice and, more productively, in other animals. Some researchers focused particularly on expressing the proteins in the milk of transgenic animals, hoping that they would serve as prodigious, self-replicating “bioreactors”. Other researchers focused on methods for cloning transgenic animals, a notable effort being the production of the sheep “Dolly”. Despite many advances, however, achieving low cost transgenic protein production has proven far more difficult than initially anticipated.
Recent advances in genome editing and cloning techniques have overcome some of the obstacles. Transgene “integration” frequencies have been increased from a few per cent to 30% – 100%, simplifying production, reducing cost, and broadening the scope of feasible projects. For example, the pig mammary gland recently has been engineered to better perform the intracellular modifications needed to make very complicated proteins, such as anti-hemophilia Factor IX. Cows have been engineered with a balanced array of three full length gene to make human fibrinogen, which is difficult and expensive to make by conventional methods, especially in the amounts required to manufacture affordable surgical tissue sealants. Only 300 of these cows can produce a metric ton of fibrinogen, enough for large scale commercial production.
Producing proteins in the milk of transgenic livestock can be one tenth as expensive as convention methods for manufacturing biotherapeutics, and he capital investment required to develop transgenic production capacity can be one billion dollars or more below that required for a stainless steel cell culture production facility. The lower capital requirements are particularly important in the developing world where capital often is scarce. Furthermore, the reduced production cost makes it feasible to economically produce large volume biotherapeutics, such as monoclonal antibodies to treat cancer, and fibrinogen to treat exsanguinating trauma, even in developing economies. These advantages and USFDA/ EMEA approval of Atryn, a regulatory coagulation protein made in the milk of transgenic goats, have catalyzed developing countries, such as Brazil and China, to develop biopharmaceutical manufacturing in the milk of transgenic livestock to meet their needs for biopharmaceutical proteins.
This lecture will discuss genetic engineering of livestock animals, particularly for producing biopharmaceutical proteins in milk, and the promise of this technology to provide low cost production of medically important substances in the developing world.
About the Speaker
Bill Velander is Distinguished Scholar and Fellow in the Department of Chemical and Biomolecular Engineering at the University of Nebraska – Lincoln. Previously he served as Chair of the Department, and before joining UNL, he was a faculty member at Virginia Tech.
Bill has worked throughout his career on the production of blood plasma-derived medicines, particularly methods for producing them in transgenic animals. His interest in producing safer blood-derived medicines was spurred by the widespread contamination of blood supplies and derivatives by HIV and Hepatitis in the late 1980s. In collaborations with colleagues at the American Red Cross Holland Laboratory he pioneered the production of genetically engineered versions of human Protein C, anti-hemophiliac factors VIII and IX, von Willebrant’s factor and fibrinogen in the milk of transgenic animals. And he has also done pioneering work on “humanizing” pig tissues and organs to make them safe for human transplant therapy.
Bill is an author or co-author of many scientific publications and an inventor in many patent applications and issued patents. His work also has been featured in the mass media, including a cover story in National Geographic, articles in Scientific American, Smithsonian and Discover magazine, a broadcast on Discovery Health Channel, and an exhibit at the Chicago Museum of Science and Industry. He also served as consultant to Harrison Ford on “Extraordinary Measures” a film about scientists’ contributions to medicine.
Bill was deeply involved in developing the USFDA’s regulatory guidelines for human therapeutics derived from transgenic animals and plants. He is an elected fellow of the American Institute of Medical & Biological Engineering, and served as AIMBE’s ambassador to Capitol Hill.
Bill earned a BS in Biochemistry at Illinois Benedictine College, an MChE at Illinois Institute of Technology and a PhD in Chemical Engineering at Pennsylvania State University.
President Larry Millstein called the 2360th meeting of the Society to order at 8:05 p.m. He announced the order of business and welcomed new members. The minutes of the previous meeting were read and approved. President Millstein then introduced the speaker for the evening, William H. Velander, Distinguished Scholar and Fellow of the Department of Chemical and Biomolecular Engineering at the College of Engineering of the University of Nebraska at Lincoln. His lecture was titled "Genetically Engineered Livestock: Bringing 21st Century Medicines to the Developing World".
Dr. Velander began by noting that the majority of the world does not have access to the level of technology and medical care that we enjoy in the United States. Some diseases, such as hemophilia, can be effectively treated using current biopharmaceutical production methods, but these methods are so expensive as to be effectively unavailable outside of the wealthiest healthcare systems.
Blood proteins Factor VIII and Factor IX are the basis for the blood clotting response, and the inability to produce these proteins (called Hemophilia A and Hemophila B, respectively), is primarily treated by replacement therapy with these proteins.
Unfortunately, Dr. Velander explained, Factor IX is also one of the most complicated proteins known to science. This complex structure is essential to its ability to identify a wound site, as well as its pharmacokinetics, that is, the duration of its availability in the blood stream. Its complex structure makes it difficult to synthesize, even for human cells.
Today, these substances are produced in “bioreactors”, large stainless steel vats full of cells that produce small amounts of the desired protein. Such factories can cost approximately $1 billion apiece and produce only 1-4 grams per liter over 72 hours. This is far too slow to meet research needs, let alone therapeutic needs.
By contrast, production of the same proteins through the milk of transgenic animals could achieve a production of 1-50 grams per liter per hour, if we could achieve a suitable transgenic animal.
The first method attempted was pro-nuclear injection, in which modified DNA strands are simply injected into fertilized eggs. This approach is imperfect because it creates “mosaic animals” in which some of the cells are modified and others are not. An improved method is cloning via somatic cell nuclear transfer, in which the nucleus is removed from a fertilized egg and a transgenic nucleus is substituted.
Dr. Velander explained that pigs are his primary research animal for these experiments because they are easier to genetically engineer, they have a short gestation time, and they produce numerous of offspring. Perhaps even more importantly, a pig’s liver and biochemistry is sophisticated enough to perform the post-translational modifications necessary to create complex molecules such as Factor VIII and Factor IX.
Dr. Velander explained Factor VIII is restricted at the transcription level, meaning that even the human liver does a poor job at making Factor VIII. As a result, bioreactors have an extremely poor yield of Factor VIII. Dr. Velander’s transgenic pigs produced greater volume of Factor VIII proteins, but tests showed that only a small portion of the output was correctly assembled into effective Factor VIII.
From this, Dr. Velander concluded that the protein needed to be re-engineered at the genetic level to be simpler for the cellular machinery to construct. The resulting recombinant Factor VIII was as therapeutically effective as the best alternatives on the market, but could be created at one thousand times the volume.
To put these advances into context, Dr. Velander showed that in order to meet the current worldwide annual need for Factor IX to treat hemophilia B patients, we would need to process 8,000 liters of human plasma per year. Using current transgenic techniques, this same volume of Factor IX could be produced from the milk of 2,500 pigs.
Dr. Velander concluded by noting that the project to bring Factor VIII, Factor IX, and other recombinant biopharmaceuticals into production will continue to require substantial investment, much of which is likely to be led by developing countries seeking to ensure that their citizens can benefit from these next-generation techniques.
After the conclusion of the talk, President Millstein invited questions from the audience.
One questioner asked if recombinant thrombin could be useful in treating traumatic wounds and massive bleeding. Dr. Velander explained that there is generally insufficient endogenous fibrinogen at such wound sites for this to be effective, but that it remains a valuable treatment for smaller wounds such as during surgery.
Another questioner asked whether the genetically engineered animals or their milk are dangerous to humans. Dr. Velander responded that these modifications are only expressed in the milk, and that in any case the GE proteins are substantially the same as those already existing in the animals. In other words, the transgenic animals are safe enough to eat.
After the question and answer period, President Millstein thanked the speaker, made the usual housekeeping announcements, and invited guests to join the Society. At 10:04 p.m., President Millstein adjourned the 2360th meeting of the Society to the social hour.
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