- Interferon
- : A naturally occurring substance that interferes with the ability of viruses to reproduce. Interferon also boosts the immune system. There are a number of different interferons. They fall into three main classes : alpha, beta, and gamma. All are proteins (lymphokines) normally produced by the body in response to infection. The interferons have been synthesized using recombinant DNA technology. The goal of interferon therapy is to eradicate a virus from an infected person. Using interferon, for example, to eradicate the hepatitis B or C virus will, it is hoped, prevent the future development of cirrhosis and cancer of the liver. This may require months and even years of interferon treatment and may not be effective in many patients. In therapeutic doses, interferon can be hard to tolerate because of the side-effects, with flu-like symptoms such as fatigue, headache and aches and, less regularly, low thyroid activity, arthritis, low platelet count and depression which can attain suicidal proportions. Interferon was discovered in 1957 by the Alick Isaacs and Jean Lindenmann (who did not receive the Nobel Prize for their discovery). Interferon is so named because of its ability to interfere with virus
* * *A class of small protein and glycoprotein cytokines (15–28 kD) produced by T cells, fibroblasts, and other cells in response to viral infection and other biological and synthetic stimuli. Interferons bind to specific receptors on cell membranes; their effects include inducing enzymes, suppressing cell proliferation, inhibiting viral proliferation, enhancing the phagocytic activity of macrophages, and augmenting the cytotoxic activity of T lymphocytes. Interferons are divided into five major classes (alpha, beta, gamma, tau, and omega) and several subclasses (indicated by Arabic numerals and letters) on the basis of physicochemical properties, cells of origin, mode of induction, and antibody reactions. [interfere + -on] The discovery in 1957 that viral infection of human cells induces the formation of natural antiviral agents raised the hope that these substances might have therapeutic potential. Early studies showed that, unlike antibodies, interferons are active against a broad range of viruses, but progress in applying this knowledge to human medicine was retarded by the difficulty of producing interferons in sufficient quantity. In the 1980s the development of recombinant DNA technology overcame this obstacle, and interferons now play an important role in the treatment not only of viral infections but also of certain malignancies. Commercially available interferons are produced by genetically altered colonies of Escherichia coli or Chinese hamster ovary cells, or are induced by controlled viral infection in pooled human leukocytes. Alpha interferons have found the widest application in medicine. (The spelling alpha is used with respect to naturally occurring interferons; in compliance with international conventions for generic drug names, the spelling alfa appears in names of pharmaceutical formulations.) Alpha interferons are used in the treatment of chronic hepatitis B and hepatitis C, hairy cell leukemia, chronic myelogenous leukemia, AIDS-related Kaposi sarcoma, malignant melanoma, condylomata acuminata and recurrent respiratory papillomatosis due to human papillomavirus, and infantile hemangiomatosis. About 50% of patients treated for chronic hepatitis B with i.-alfa show disappearance of hepatitis Be antigen (HBeAg) and reversion of alanine aminotransferase to normal. The response rate in chronic hepatitis C is lower (15–25%), but better results are achieved by using more aggressive therapy (daily rather than thrice weekly administration) and continuing it longer (a minimum of 12 months). Modified formulations of i.-alfa conjugated with polyethylene glycol (PEG), which have yielded promising results in hepatitis C with once-a-week dosing, are in phase III trials. Beta interferons reduce clinical recurrences and progression of myelin damage in multiple sclerosis. Gamma i. is effective in retarding tissue changes in osteopetrosis and systemic scleroderma and in reducing the frequency and severity of infections in chronic granulomatous disease. Administration of interferons is parenteral (intravenous, intramuscular, subcutaneous, intranasal, intrathecal, or intralesional) and several weeks of treatment may be required before clinical response is noted. More than 50% of patients experience a flulike syndrome of fatigue, myalgia, and arthralgia. Gastrointestinal and CNS side effect s are also common, and marrow suppression may occur with prolonged treatment.- i. alfa 2b a water-soluble protein (MW 19,271) secreted by cells infected by virus; used to treat hairy cell leukemia, malignant melanoma, condylomata acuminata, AIDS-related Kaposi sarcoma, and chronic hepatitis C.- i. alpha (IFN-α) the major i. made by virus-induced leukocytes; a number of different subtypes exist that are elaborated by leukocytes in response to viral infection or to stimulation with double-stranded RNA. There are 14 genes on the short arm of chromosome 9 that code for these substances in humans. IFN-α-2A and -2B are protein products made by recombinant DNA techniques and are used as antineoplastic agents. SYN: leukocyte i..- i. beta (IFN-β) i. elaborated by fibroblasts and microphages in response to the same stimuli as i. alpha; only one gene codes for this i.. SYN: fibroblast i..- i. beta 1b a purified protein containing 165 amino acid s (MW approximately 18,500) with antiviral and immunomodulatory effects, used in the treatment of relapsing-remitting multiple sclerosis to reduce the frequency of clinical exacerbations.- i. gamma (IFN-γ) i. elaborated by T lymphocytes in response to either specific antigen or mitogenic stimulation; only one gene codes for γ i.. i. gamma behaves like a biological response modifies and is highly immunoregulatory. SYN: antigen i., immune i..- i.-omega a form of i. known as i.-alpha-2.- i.-tau an i. secreted by bovine concepti, with potent antiretroviral activity; in experimental use. SYN: trophoblast i., trophoblastin.- trophoblast i. SYN: i.-tau.
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in·ter·fer·on .int-ə(r)-'fi(ə)r-.än n any of a group of heat-stable soluble basic antiviral glycoproteins of low molecular weight that are produced usu. by cells exposed to the action of a virus, sometimes to the action of another intracellular parasite (as a bacterium), or experimentally to the action of some chemicals, and that include some used medically as antiviral or antineoplastic agents see ALPHA INTERFERON, BETA INTERFERON, GAMMA INTERFERON* * *
n.a substance that is produced by cells infected with a virus and has the ability to inhibit viral growth (see cytokines). Interferon is active against many different viruses, but particular interferons are effective only in the species that produces them. There are three types of human interferon: alpha (from white blood cells), beta (from fibroblasts), and gamma (from lymphocytes).Human interferon can now be produced in bacterial host cells by genetic engineering for clinical use. Interferon alfa (Intron A, Roferon A, Viraferon) is used in treating hepatitis B and C and certain cancers, peginterferon alfa (ViraferonPeg) is used for hepatitis C, and interferon beta (Avonex, Betaferon, Rebif) for multiple sclerosis. Side-effects, including flulike symptoms, lethargy, and depression, may be severe.* * *
in·ter·fer·on (in″tər-fērґon) any of a family of glycoproteins that exert virus-nonspecific but host-specific antiviral activity by inducing the transcription of cellular genes coding for antiviral proteins that selectively inhibit the synthesis of viral RNA and proteins. Interferons also have immunoregulatory functions (inhibition of B cell activation and antibody production enhancement of T cell activity, and enhancement of NK cell cytotoxic activity) and can inhibit the growth of nonviral intracellular parasites. Production of interferon can be stimulated by viral infection, especially by the presence of double-stranded RNA, by intracellular parasites (chlamydiae, rickettsiae), by protozoa (Toxoplasma), and by bacteria (streptococci, staphylococci) and bacterial products (endotoxins). Interferons have been divided into three distinct types (α, β, and γ) associated with specific producer cells and functions, but all animal cells are able to produce interferons, and certain producer cells (leukocytes and fibroblasts) produce more than one type (both interferon-α and interferon-β). Abbreviated IFN.
Medical dictionary. 2011.
