Interferons: What are they and what do they do?
Interferons are low-molecular-weight proteins that are part of the non-specific immune system and are an important first line of defense against viral infections. Interferons are produced by virally infected cells in response to viral double-stranded RNA. They are released and bind to receptors on target cells, resulting in an anti-viral state in target cells. Interferons do not kill viruses directly but instead prevent them from further infecting healthy cells. They have no effect on cells that have already been infected by a virus.
Types of interferons
There are three types of interferons. Interferon-alpha is produced by virus-infected leukocytes. Interferon-beta is produced by virus-infected fibroblasts or epithelial cells. Both types are potent anti-virals. The third type, interferon-gamma, is produced by activated T-cells and NK cells. It enhances the inflammatory response by increasing the microbial activity of macrophages. It is important to note that interferons are species specific; i.e., human interferon is effective only in humans. Interferons are not virus specific and are effective against almost all viruses.
Interferons in drug therapy
Interferons are also important in drug therapy for many diseases involving the immune system. They are manufactured by using recombinant DNA technology. The mechanism of action by which interferons work is complex and not well understood. Here are some examples for various interferons and the diseases they treat:
- Interferon alfa-2a (Roferon-A) is used to treat hairy cell leukemia, AIDS-related Kaposi’s sarcoma, and chronic myelogenous leukemia.
- Interferon alfa-2b is used to treat hairy cell leukemia, malignant melanoma, condylomata accuminata, AIDS-related Kaposi’s sarcoma, and chronic hepatitis B and C.
- Interferon beta-1b (Betaseron) and interferon beta-1a (Avonex) are used to treat multiple sclerosis.
- Interferon alfa-N3 (Alferon-N) is used to treat genital and perinanal warts caused by human papillomavirus (HPV).
- Interferon gamma-1B (Actimmune) is used to treat chronic granulomatous disease and severe, malignant osteopetrosis.
Side effects of interferons
Flu-like symptoms such as fever, chills, muscle aches and malaise may occur after each injection. Other side effects include abdominal pain, nausea, vomiting, diarrhea, back pain, anorexia and increased heart rate. Mild hair loss or thinning, skin rashes, cough and difficulty breathing may be present. Lab results that may be affected by interferons include low white blood cell count, thrombocytopenia, low red blood cell count, increased liver enzymes, and increased triglycerides. Liver function should be monitored as many interferons may cause liver failure. High levels of interferons in general can cause kidney, bone marrow and heart toxicity.
Drug interactions with interferons
Some medications interact with interferons. Interferon alfa-2a, interferon alfa 2-b, and interferon beta-1b may increase blood levels of zidovudine (AZT, Retrovir). This can potentially lead to toxicity. Interferon alfa-2a and interferon alfa-2b may increase theophylline clearance time from the body. In these cases, dosages may need to be adjusted while interferon therapy is in place.
Research and interferons
Advances in medicine and our understanding of how interferons work can make a substantial impact on how diseases will be treated in the future. Extensive research is underway at the University of Texas Medical Center at Houston to evaluate the use of oral interferon to treat multiple sclerosis and type 1 diabetes. Another trial is investigating interferon alpha in the preservation of residual beta cell function in newly diagnosed type 1 diabetes.
References
Brod, S. (n.d.). University of Texas Medical Center at Houston: Department of Neurology.
McCane, K., Huether, S., Brashers, V., Rote, N. (2010). Pathophysiology: The biologic basis for disease in adults and children, 6th ed. St. Louis: Mosby.
