Clinical

Assay detects interferon antibodies, drug bioactivity in hepatitis C patients

Last Updated: 2006-01-06 15:10:45 -0400 (Reuters Health)

NEW YORK (Reuters Health) - German researchers have developed a new screening system to identify interferon-neutralizing antibodies in patients with hepatitis C who are not responding to interferon alpha therapy.

The assay includes a real-time RT-PCR test that identifies MxA expression in peripheral blood mononuclear cells. MxA is a GTPase induced by interferon that is a "highly specific and reliable" marker for the drug's bioactivity, Dr. Georg Kochs of the Institute for Medical Microbiology and Hygiene in Freiburg and colleagues write in the January issue of the Journal of Medical Virology.

Dr. Kochs and his team used the assay to identify interferon alpha-neutralizing antibodies in sera from 3 of 38 patients not responding to interferon, but did not find the antibodies in 24 patients with hepatitis C who responded to interferon therapy or in 21 healthy controls.

The researchers also found a correlation between presence of the antibodies and a lack of MxA induction after interferon treatment, indicating a "complete lack of IFN bioactivity."

The role of anti-interferon antibodies in interferon resistance to hepatitis C "is still a matter of debate," the researchers note. "This new and convenient bioassay constitutes a helpful tool for answering this important question."

The test, based on a reporter plasmid containing the luciferase gene controlled by the Mx1 promoter, does not require special bioassay conditions, and is both convenient and sensitive, the researchers note. They suggest that it could be used to identify patients who are not responding to interferon early in therapy and monitor them for the development of interferon-neutralizing antibodies.

"The data obtained should be used to optimize further treatment and possibly to identify alternative interferon preparations not neutralized by the patient's serum," the researchers conclude.

J Med Virol 2006;78:74-82.