MxA protein assay for optimal monitoring of IFN-beta bioactivity in the treatment of MS patients.

OBJECTIVES: Myxovirus resistance protein A (MxA) can be used as a marker of the bioactivity of interferon-beta (IFN-beta) therapy. Two to forty per cent of IFN-beta-treated multiple sclerosis (MS) patients develop IFN-beta-neutralizing antibodies (NAb) with subsequent attenuation of MxA protein induction. The aim of this study was to set up a simple MxA enzyme immunoassay (EIA) for the measurement of MxA protein and to evaluate the EIA test by comparing the results with flow cytometric analysis and the measurement of NAb. METHODS: total of 51 IFN-beta-treated relapsing-remitting MS (RRMS) patients were tested for MxA protein expression by using both MxA EIA assay and flow cytometric analysis. Thirteen patients were confirmed to be NAb-positive. RESULTS: The correlation between EIA and flow cytometric analysis was significant with a wider range of measured levels in the EIA. Patients with NAb had low MxA levels, but in some patients, remaining MxA induction could be detected despite NAb. CONCLUSIONS: The MxA EIA assay seems to be a practical method for large-scale analysis of the bioactivity of IFN-beta treatment.

MxA protein induction in MS patients treated with intramuscular IFNbeta-1a.

MxA protein production in peripheral blood leukocytes is a valuable marker to evaluate biologic effects of interferon-beta (IFNbeta) therapy in multiple sclerosis (MS) patients. The three IFNbeta preparations available in the treatment of MS differ with respect to antigenicity and biologic activity. We studied prospectively the induction of MxA protein and the development of binding (BAb) and neutralising antibodies (NAb) in nine relapsing-remitting MS (RRMS) patients during one year of intramuscular IFNbeta -1a (Avonex) treatment. Another nine RRMS patient treated with Avonex for 1-3.5 years were also included. The results were compared with our earlier published data of subcutaneous IFNbeta-1a (Rebif). None of these 18 patients developed NAb but three of the long-term patients developed BAb. The baseline MxA protein levels rose but the induction was weaker compared to Rebif. The stimulation index (MxA after/before IFNbeta-1a injection) remained elevated. Weekly intramuscular dosing of IFNbeta-1a provides a sustained effect on lymphocytes but differences in leukocyte stimulation may underlie some of the differences between IFNbeta therapies.

The efficacy of glatiramer acetate in beta-interferon-intolerant MS patients.

OBJECTIVES: Glatiramer acetate (GA) is routinely used in multiple sclerosis (MS) patients who cannot tolerate or fail to respond to beta-interferon (IFN-beta). The aim of this study was to assess the efficacy and tolerability of GA in these patients. METHODS: Fifteen relapsing-remitting MS patients who had discontinued IFN-beta therapy due to side effects were included in this open, 1-year prospective study. Neurologic examinations and laboratory assessments were performed every 3 months. The induction of MxA protein production was also evaluated. RESULTS: Eleven of fifteen patients (73%) tolerated GA well whereas four patients (27%) discontinued treatment due to side effects. The relapse rate reduced from 1.86 per year to 0.91 per year. Neither laboratory abnormalities nor MxA protein induction was found. CONCLUSION: GA can be considered as a good treatment alternative to IFN-beta-intolerant MS patients. However, some patients were not able to use available immunomodulative treatments, which emphasizes the need for new therapeutic options. The lack of MxA protein induction confirms the different mechanisms of action of GA and IFN-beta.

Neutralizing antibodies reduce MxA protein induction in interferon-beta-1a-treated MS patients.

BACKGROUND: Neutralizing antibodies (NAb) during interferon-beta (IFNbeta) treatment of MS are associated with reduced clinical and MR efficacy. NAb inhibit the IFN- inducible MxA gene expression and neutralize the capability of IFNbeta to inhibit virus growth in vitro. Presently, there is no clear concept of the biologic importance of IFNbeta antibodies; most of the tests applied for the detection of NAb in previous publications are not widely available, and the results are not fully comparable. METHODS: A 1-year prospective study of the development of binding antibodies (BAb) and NAb and their relationship to IFN-inducible MxA protein levels in peripheral blood leukocytes in 20 IFNbeta-1a-treated patients with relapsing-remitting MS was conducted. RESULTS: In seven of nine NAb-positive patients, IFNbeta-1a was unable to induce MxA protein. BAb were detected in 11 patients, and they preceded or paralleled the development of NAb in all the patients. The titer of NAb correlated positively with BAb titer and negatively with MxA expression level. There was also a weaker but clear correlation between BAb titers and MxA levels. CONCLUSIONS: NAb, in most but not all cases, inhibited the in vivo function of IFNbeta. Analysis of MxA protein in lymphocytes together with analysis of NAb is a promising marker for evaluating the biologic effects of IFNbeta treatment in MS patients.