MxA gene expression analysis as an interferon-beta bioactivity measurement in patients with multiple sclerosis and the identification of antibody-mediated decreased bioactivity.
BACKGROUND
Interferon-beta (IFNbeta) has proven to be an important advance in the therapy of multiple sclerosis (MS), but optimal markers for bioactivity have not been identified. To accurately measure bioactivity in MS patients treated with IFNbeta, we developed and tested a real-time reverse transcriptase (RT)-PCR assay for gene expression of MxA, an IFNbeta-induced gene in the peripheral blood of patients treated with IFNbeta.


METHODS
We compared IFNbeta-treated patients with MS to controls in expression of MxA relative to the house-keeping gene, GAPDH. 2'-5'oligoadenylate synthetase (OAS) gene expression was also tested by real-time RT-PCR on RNA from the same patient specimens. Anti-IFNbeta antibody was measured by ELISA and a cytopathic effect assay.


RESULTS
Seven of 54 patients were found to have complete loss of bioactivity. MxA expression correlated well with OAS expression. All patients with lost bioactivity had high levels of binding antibodies or neutralizing antibodies.


CONCLUSIONS
This is the first demonstration that a real-time RT-PCR assay can be used to monitor therapy with interferons. These data identify MxA mRNA as an excellent biomarker for INFbeta action on the IFN receptor, and clarify the relationship between anti-IFNbeta antibodies and bioactivity in patients with MS treated with IFNbeta.
Pachner
Andrew
A
Department of Neurosciences, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 08540, USA. pachner@umdnj.edu
Narayan
Kavitha
K
Price
Nicholson
N
Hurd
Marie
M
Dail
Donna
D
D015088:2',5'-Oligoadenylate Synthetase / Q000096:biosynthesis / Q000097:blood; D000906:Antibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D016903:Drug Monitoring; D020558:GTP Phosphohydrolases / Q000096:biosynthesis / Q000097:blood; D019204:GTP-Binding Proteins / Q000096:biosynthesis* / Q000097:blood; D006801:Humans; D016899:Interferon-beta / Q000276:immunology / Q000627:therapeutic use*; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D009103:Multiple Sclerosis / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism*; D064547:Myxovirus Resistance Proteins; D011446:Prospective Studies; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D000906:Antibodies; D015415:Biomarkers; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D016899:Interferon-beta; D015088:2',5'-Oligoadenylate Synthetase; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins