Understanding Hepatitis C Interferon Therapy
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Interferon is a cytokine, a specific protein that is no stranger to the human body. In fact, the human body is constantly making interferon, and makes even greater amounts when trying to fight off an intruder, such as a virus. People experience this when suffering with the flu. When sick with the flu, the body makes extra interferon to defeat the virus causing the illness. The extra interferon causes symptoms such as fever, nausea, achy and sore muscles, joint pain and fatigue. This is called an antiviral effect. Interferon therapy is currently the gold standard in treatment for certain types of hepatitis B and C.
How Does it Work?
While the interferon used for hepatitis treatment is slightly different from the kind made in the body, it helps defeat the virus in three ways:
- By attaching to healthy cells to help defend against invading viruses.
- By helping the immune system to stop the virus from multiplying.
- By assisting the body in ridding itself of infected cells while preventing healthy cells from being infected.
Interferon helps the body distinguish between cells infected by the virus and non-infected cells, targeting infected cells for destruction. For unknown reasons, a virus in the liver often becomes invisible to the immune system. If your body can’t see the virus, it can’t destroy it. This invisibility permits the virus to multiply within the liver, fostering a more chronic and severe infection. Scientists have learned that if they gave synthetic (created through genetic engineering) interferon to a person with chronic viral hepatitis, they could increase the immune system’s ability to detect, or see, the infection. Imagine liver cells blending in with invaders, both a clear transparent color. The addition of interferon is like staining the infection deep red, highlighting them so they can be targeted for the immune system’s fighter cells. Interferon also helps patients with viral hepatitis by directly suppressing the formation of new virus particles within the liver.
What kinds are there?
Scientists have determined that the body makes three distinct types of interferon; alpha, beta and gamma interferon, each containing several members. Alpha interferon has been approved for therapeutic use against a specific type of leukemia, hepatitis B and C, genital warts, AIDS- related Kaposi’s sarcoma and some rare cancers of blood and bone marrow. Nasal sprays containing alpha interferon provide some protection against colds caused by rhinoviruses.
There are two primary types of interferon currently available. To date, interferon-alpha 2a or 2b is the compound that has been extensively used and tested. Though the dose varies, patients with chronic hepatitis C usually receive 3 million units, three times per week. Individuals with chronic hepatitis B receive a higher dose of 10 million units, three times per week. Although it can widely vary, the typical duration of therapy is 48 weeks for hepatitis C, and 16 weeks for hepatitis B.
A newer formulation on the market is called pegylated interferon. This drug was developed in response to the fall in blood levels, rapid breakdown and subsequent loss of antiviral effect of interferon given 3 times per week. By attaching a molecule called polyethylene glycol to interferon-alpha 2a or 2b, researchers were able to slow its breakdown by the body. More consistent drug levels were achieved with the need to only give the drug once per week. Above and beyond the convenience of once a week injection, the pegylated formulations also result in higher viral clearance rates.
Side Effects
Interferon used for hepatitis treatment — alpha and pegylated forms — have been known to cause severe side effects, including:
- worsening of psoriasis
- irritability and insomnia
- trouble breathing
- chest pain
- high fever and chills
- fatigue
- headaches
- decreased appetite, nausea and vomiting
- weight loss
- muscle aches
- bone marrow suppression
- weight and hair loss
- depression and mood changes
- decreased white blood cells and platelets
- elevated liver enzymes
- difficulty concentrating and impaired memory
Interferon’s effectiveness
For hepatitis C, the cure rate is defined as the inability to detect virus in the blood 6 months after stopping therapy. This rate varies significantly depending on a number of patient, viral and drug regimen characteristics. The most important factor is the viral genotype. Unfortunately, genotypes 1a and 1b, the most common types in North America, have the worst response rate, with only 19 percent in interferon and 25-40 percent in pegylated interferon responses, respectively. Adding a second anti-viral drug, ribavirin, increases the response rate to between 35 and 60 percent. Genotypes 2 and 3 carry a much higher eradication rate (60 percent or more).
Hepatitis B is associated with a 35 percent response rate as defined by normalization of liver enzymes and loss of markers of active viral infection. Such a response signifies conversion to a healthy carrier state. This is further characterized by a decrease in the ability to spread the virus to others and a decrease in the liver damage associated with viral infection. Complete elimination of the Hepatitis B virus is rare.
As you can see, not everyone responds to interferon therapy, causing some people to turn to natural alternatives. According to many physicians in Japan, the prescription-strength remedy Sho-saiko-to may be helpful for nonresponders to interferon therapy.
Perhaps having a better understanding of interferon, including what it is, how it works, what its side effects are and how effective it is will help people make the best treatment decisions. Clinical trials are being conducted around the world to increase interferon’s effectiveness, reduce its side effects and create even better alternatives for the eradication of viral hepatitis.
References:
www.aids.about.com, Interferon – alpha, Mark Cichocki, About Inc., 2006.
www.en.wikipedia.org, Interferon, Wikipedia Foundation, Inc., 2006.
www.gihealth.com, Interferon Therapy, Three Rivers Endoscopy Center, 2005.
www.hepatitis-c.de, What is Interferon?, Deutsches Hepatitis C Forum, 2006.
www.immunityfacts.com, Interferon and Its Role in Immune Health, Center for Immune Research, 2006.
www.introna.com, What are Interferons?, Schering Corporation, 2002.
