Interferon-beta: the neutralizing antibody (NAb) titre predicts reversion to NAb negativity.
BACKGROUND
It has been reported that in some patients with MS who develop neutralizing antibodies (NAbs) against interferon beta (IFNbeta), antibody levels can initially increase and then decrease thereafter even when treatment is continued.


OBJECTIVE
To determine whether NAb titre correlates with time to reversion to NAb negativity in patients with multiple sclerosis (MS).


METHODS
Twenty-eight patients with MS who were NAb-positive during treatment with one of the currently available IFNbetas were included in this retrospective study. NAb titres were determined by the myxovirus resistance protein A induction assay. Patients were considered NAb-positive if they had at least two consecutive samples with titres of > or = 20 neutralizing units (NU). Reversion to NAb-negative status was defined as two consecutive negative samples (NAb titre of < 20 NU) after NAb positivity.


RESULTS
When measured two years after treatment initiation, a NAb titre of < 75 NU had a 91.7% sensitivity and a 87.5% specificity for reversion to NAb negativity in the following two years (after a total of four years of treatment). In addition, somewhat surprisingly, patients whose serum converted to NAb-negative generally developed peak NAb titres earlier than patients who remained NAb-positive (mean time of first detection was 21 versus 38 months, respectively).


CONCLUSIONS
The NAb titre might support treatment decisions in patients with MS whose test results are positive for NAbs.
Department of Neurology, University of Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria.
C
C
Gneiss
M
M
Reindl
A
A
Lutterotti
R
R
Ehling
R
R
Egg
M
M
Khalil
T
T
Berger
F
F
Deisenhammer
D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000906:Antibodies / Q000097:blood; D006801:Humans; D000068556:Interferon beta-1a; D016899:Interferon-beta / Q000008:administration & dosage* / Q000276:immunology*; D009103:Multiple Sclerosis / Q000188:drug therapy* / Q000276:immunology*; D009500:Neutralization Tests; D011237:Predictive Value of Tests; D012189:Retrospective Studies
D000276:Adjuvants, Immunologic; D000906:Antibodies; D016899:Interferon-beta; D000068556:Interferon beta-1a