Correlation of interferon-induced expression of MxA mRNA in peripheral blood mononuclear cells with the response of patients with chronic active hepatitis C to IFN-alpha therapy.

MxA, a protein with selective activity against certain viruses, is an accepted specific indicator of type I interferon (IFN) activity. We have developed an internally controlled quantitative-competitive PCR to measure the amounts of MxA mRNA expressed in peripheral blood mononuclear cells (PBMC). This assay is more sensitive, quantitative, and easily applied to serial clinical samples than previously described methods. We have applied this assay retrospectively to 27 patients with chronic active hepatitis C given IFN-alpha2. Most such patients gain no sustained benefit but nevertheless suffer from the side effects, expense, and inconvenience of the treatment. Fourteen of the 27 had been classified on clinical grounds as responders and 13 as nonresponders at the end of a 6 month treatment period. We measured MxA mRNA in PBMC obtained before and after 8 weeks of IFN-alpha2 treatment. All the patients expressed some level of mRNA before treatment began, and after 8 weeks of treatment, the level rose in 19. This increase was significant (p < 0.001) only in patients classified as responders. This strongly suggests that hepatitis C virus (HCV) patients who express increased amounts of MxA mRNA in their PBMC during IFN-alpha treatment are most likely to obtain long-term benefit. If this finding is confirmed in future prospective studies, it will provide an extremely important predictive marker for managing IFN-alpha therapy in patients with HCV.