The most frequent side effects are – increased body temperature, fatigue, headache, muscle pain, convulsion, dizziness, hair thinning, and depression. Erythema, pain and hardness on the spot of injection are also frequently observed. Interferon therapy causes immunosuppression but all the side effects are usually reversible and disappear within a year after the therapy has been stopped.
Resistance of Virus to Interferons
Unfortunately many viruses have evolved mechanisms to resist interferon activity. Certain viruses evade the interferon’s response by blocking downstream signaling events that occur after the cytokine binds to its receptor, by preventing further interferon production, and by inhibiting the functions of proteins that are induced by interferon.
Some of the viruses may code proteins that can block interferon binding to cells. The ability of interferon to induce protein production from interferon stimulated genes (ISGs) can also be affected by the viruses.
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For example production of protein kinase R can be disrupted in cells infected with Japanese Encephalitis Virus (JEV) or flaviviruses. Some viruses escape the anti-viral activities of interferons by genetic mutation.
The resistant virus may escape the influence of interferon by blocking complement activation, interfering in surface expression of MHC or by preventing the host cell committing apoptosis.