Growth Hormone and Interferon

Somatotropin:

Somatotropin, the hGH is secreted by the anterior lobe of pituitary glands which consists of 191 amino acid units. Its secretion is regulated by two other hormones (Somatostatin and growth hormone releasing) produced by hypothalamus. Deficiency of somatotropin in about 3% cases is hereditary. It has been estimated to about 1 child in 5,000.

The extraction of somatotropin pharmaceutically from the pituitary glands could not meet annual demand of this hormone. Biosynthesis of somatotropin was achieved through gene cloning procedures.

Recombinant human growth hormone Somatotropin Production:

Recombinant human growth hormone is generally produced by inserting the human growth hormone gene into plasmids of E.Coli bacteria. Recombinant bacterial cells are cultured and human growth hormones produced by these bacteria are extracted from the extracellular     media.
Human growth hormones are also produced and extracted using animal cell culture are now a days are used in treating patients with renal carcinoma and also to treat children who are suffering from human growth deficiency.

The Use of Recombinant DNA Technology to Produce a Save Supply of Growth Hormone

• Pituitary dwarfism - a disease caused by the lack of growth hormone (created by the gene GH1)
• Early research showed that the condition could be treated with injections of human growth hormone
• Growth hormone could only be obtained from human pituitary glands
• These were obtained from cadavers
• Later studies showed that the cadaver supplied growth hormones were often contaminated, so other methods needed to be developed to artificially produce human growth hormone

Use of Recombinant DNA Technology to Produce a Safe Supply of Growth Hormone

• Isolate mRNAs from cells in pituitary glands
• use reverse transcriptase to synthesize cDNA from each mRNA
• Attach restriction endonuclease recognition site to ends of each cDNA
• Cut cDNAs and plasmids with restriction endonucleases - remaining sticky ends join by complementary base pairing
• Ligate cDNAs and plasmids with ligase enzymes. (plasmids also contain antibiotic resistance gene)
• Introduce recombinant plasmids into E. coli cells to create a cDNA library
• grow colonies on plate with an antibiotic
• only those bacteria that have taken in the plasmid will be able to grow on media.
• Transform more E. coli with the new plasmid - it will now start to produce human growth hormone
• Isolate and purify the human growth hormone!!

Interferon’s (IFNs):

For the first time, Isaacs and Lindenmann isolated the Interferon in 1957.

Interferons (IFNs) are a family of natural occuring glycoproteins made and released by host cells in response to the presence of pathogens such as viruses, bacteria or parasites or tumor cells.

IFNs exert their biological activities by inducing the expression of antiviral proteins. The transcription of antiviral proteins being with IFN binding onto a membrane receptor, which activates a series of intracellular signals and ultimately leads to enhanced expression of interferon-induced genes. These genes encode for proteins that include 2^/-5^/ oligoadenylate synthetase and protein kinases, which have antiviral activity.

Interferon is used to cure many viral diseases such as common cold and hepatitis. It is species specific. In man there are three classes of interferon:

1. Alpha interferon (IFN-α) or leukocyte interferon (derived from leukocytes of blood).

2. Beta interferon (IFN-β) or fibroblast interferon (fibroblast of connective tissue).

3.  Gamma interferon (IFN-γ) or Immune interferon.

In contrast, interferon-β and interferon-γ are produced by fibroblasts and lymphocytes, respectively.

Interferon’s have also been classified in terms of their receptor binding and are classified as either type -I or II.

Both IFN-α and IFN-β bind onto type I receptors, and are referred to as type I IFNs.

IFN-γ is the only IFN that binds onto type II receptors, and thus is classified as a type II IFN.

Commercially Available Interferon-α

              (*available in the USA)

Interferon-α 2a*

Trade name: Roferon

Clinical Uses: Hairy cell leukemia, hepatitis C virus, chronic myelogous leukemia, multiple myeloma, melanoma.

Interferon-α 2b*

Trade name: Intron A

Clinical Uses: Hairy cell leukemia, hepatitis B and C virus, AIDS-related Kaposi’s sarcoma, chronic myelogous leukemia, multiple myeloma, melanoma.

Interferon-α N1

Trade name: Alferon-N1

Interferon-α Consensus*

Trade name: Imfergen

Clinical Use: Hepatitis C virus