The human body uses a variety of substances to stay alive, grow and be healthy. A major group of useful substances in biology are proteins, and the body makes many of these naturally. Scientists discovered that, for some diseases, the delivery of a protein with a biological effect into the body could have beneficial effects on the patient. This type of protein medication is called therapeutic protein. Most therapeutic protein is sourced from genetically modified animal or microbial cells.
Proteins are an essential part of normal human function. Many different varieties exist, and they all perform specific roles in the body. Enzymes, which help the body turn one substance into another through a chemical reaction, are one important group. Some natural proteins are blood factors, and help wounds clot up to stem blood loss. Insulin is another human protein, and plays an essential role in regulation of blood sugar.
Other proteins act as part of the immune system, and help target and kill unwanted invaders to the body. Some types of protein are signalers, and promote a specific type of growth. The myriad of function of the natural array of human proteins allows scientists to pick specific proteins, research the exact job the protein does, and match this job up to medical conditions, where that protein may promote health.
Scientists have been able to create non-natural sources of lots of these human proteins. Historically, a human protein was only present in human sources, or perhaps from animals with similar proteins. The levels of therapeutic protein from natural sources generally were low, reflecting the concentration of the protein in the body tissue. One example was an early type of therapeutic protein called human growth hormone, which doctors extracted from dried pituitary glands of dead people, in order to inject it into kids with growth problems.
Sourcing problems with therapeutic protein came to an end with the advent of genetic engineering. Scientists could identify the gene in a human that contained the instructions for a specific protein. Then they placed that gene into an animal, animal cell or a microbial cell and waited for the new organism to produce the required protein.
A whole animal example of these production systems is a genetically engineered pig who expresses a blood clotting protein in its milk, which the scientists can then extract and purify. Cell culture is a common method of production. In this situation, individual cells contain the required human gene, and grow independently from each other, but express the therapeutic protein into the container that holds the cells. Cells in cell culture may be human, animal or microbial.
Therapeutic proteins act when they are delivered inside a body, such as through an injection. The body recognizes the protein as functional, and responds as if the protein was naturally occurring. Diseases that are controllable through therapeutic protein medications include certain types of anemia, specific forms of diabetes and hemophilia. Therapeutic protein may also be of use in the field of cancer treatment, cystic fibrosis and heart disease.