Fighting Diarrheal Illnesses
Diarrhea is the second leading cause of death of children under the age of five worldwide. Human milk has bioactive components to protect infants from disease that dairy animals like cows and goats do not. One approach to help children beyond the age of breastfeeding fight diarrheal illnesses is to tailor the composition of cow and goat milk to mimic that of human milk. Researchers at the University of California, Davis have generated genetically engineered dairy goats that make human lysozyme in their milk. Lysozyme is a naturally occurring antimicrobial constituent of human milk and studies in animal models have demonstrated that the lysozyme-rich milk from these goats can help treat and prevent diarrheal illnesses in the young. When combined with traditional approaches to improving childhood health such as rehydration solution and vaccines, milk from these genetically engineered animals could make a big difference in the healthy growth of infants and children and also be used to treat other diarrheal illnesses such as inflammatory bowel disease.
Generating Organs Compatible for Human Transplant
Currently, the demand for human organs for transplant far exceeds the availability of suitable organs. Only 3 out of 1,000 people have organs that can be used for transplantation meaning that less than 10% of the needs for organ transplantation currently are able to be met. Xenotransplantation, or the use of organs from other species for transplantation into humans, is becoming closer to reality with the generation of pig-derived human compatible organs to meet this vital need. Pigs are considered the prime candidate to supply organs to humans due to similarities in organ and capillary sizes. However, pig tissues contains sugars that human organs do not causing an immune response and hyperacute rejection upon transplantation. Work has been carried out over the last decades to remove these antigens from pig organs using genetic engineering and gene editing and recent work has shown that hearts from these pigs with multiple genetic modifications can function for up to six months when transplanted into baboons, taking this technology one step closer to the clinic.
Many human therapeutics are proteins derived from human tissues or plasma, making them difficult to collect and safely purify for use thus making them very costly. Milk and eggs are being used as production platforms for rare human pharmaceuticals- or as bioreactors. These are highly synthetic tissues capable of producing large amounts of protein (23 g/kg body weight in cow, 3g/egg in chicken) with proper Eukaryotic post-translational modifications. Hence, the animals can be genetically engineered to produce the desired pharmaceutical protein in large amounts in their milk or eggs which are easy to collect from the animals and process to purify the pharmaceutical from them. For instance, ATryn®, a recombinant antithrombin used to treat blood clots in people, is produced in the milk of genetically engineered goats and was the first product from a transgenic animal approved for human use by the US FDA in 2009.
Edmunds, T., S. M. Van Patten, J. Pollock, E. Hanson, R. Bernasconi, E. Higgins, P. Manavalan, C. Ziomek, H. Meade, J. M. McPherson, and E. S. Cole. 1998. Transgenically produced human antithrombin: structural and functional comparison to human plasma-derived antithrombin. Blood 91:4561–4571.
Human plasma is also a source of antibodies that can be used to treat infectious diseases caused by bacterial and viral infections. SAb Biotheraputics has genetically engineered cows to make human polyclonal antibodies when immunized with the disease-causing antigen. They employed a strategy to knockout endogenous bovine immunoglobulin genes and replace them with human immunoglobulin genes on a transchromosomal vector. This platform allows for production of humanized disease-specific antibodies in large quantities and has been used to generate antibodies for a variety of diseases including Ebola and is preparing for clinical trials for COVID-19.