12.3 Whole genome methods and pharmaceutical applications of genetic  (Page 4/9)

Genetic engineering is also used to manufacture subunit vaccines , which are safer than other vaccines because they contain only a single antigenic molecule and lack any part of the genome of the pathogen (see Vaccines ). For example, a vaccine for hepatitis B is created by inserting a gene encoding a hepatitis B surface protein into a yeast; the yeast then produces this protein, which the human immune system recognizes as an antigen. The hepatitis B antigen is purified from yeast cultures and administered to patients as a vaccine. Even though the vaccine does not contain the hepatitis B virus, the presence of the antigenic protein stimulates the immune system to produce antibodies that will protect the patient against the virus in the event of exposure. U.S. Department of Health and Human Services. “Types of Vaccines.” 2013. http://www.vaccines.gov/more_info/types/#subunit. Accessed May 27, 2016. The Internet Drug List. Recombivax . 2015. http://www.rxlist.com/recombivax-drug.htm. Accessed May 27, 2016.

Genetic engineering has also been important in the production of other therapeutic proteins, such as insulin , interferons , and human growth hormone , to treat a variety of human medical conditions. For example, at one time, it was possible to treat diabetes only by giving patients pig insulin, which caused allergic reactions due to small differences between the proteins expressed in human and pig insulin. However, since 1978, recombinant DNA technology has been used to produce large-scale quantities of human insulin using E. coli in a relatively inexpensive process that yields a more consistently effective pharmaceutical product. Scientists have also genetically engineered E. coli capable of producing human growth hormone (HGH), which is used to treat growth disorders in children and certain other disorders in adults. The HGH gene was cloned from a cDNA library and inserted into E. coli cells by cloning it into a bacterial vector. Eventually, genetic engineering will be used to produce DNA vaccines and various gene therapies, as well as customized medicines for fighting cancer and other diseases.