The increasing recognition of antibody induction in patients undergoing treatment with
biologically active recombinant proteins, makes these antibodies of concern. In the case of
Relapsing Remitting Multiple Sclerosis (RRMS), administration of interferon beta (IFNβ) -
lb can lead to the development of anti- IFN β antibodies in some patients. These antibodies
may attenuate the effects of IFNβ, resulting in resistance to therapy or to disease relapses. On
the other hand, anti-IFNP antibodies may have carrier or stabilizing functions. The purpose of
the current study was the quantification of anti- IFN β antibodies in MS patients' sera, and to
further characterize the frequency and serial profile of the antibody response. This was
achieved by a sandwich enzyme-linked immunosorbent assay (ELISA) specifically
developed for this study.
In the process of developing the sandwich ELISA, an anti- IFN β antibody reference
pool was established by screening serum samples from 50 RRMS patients undergoing IFNβ
therapy, using a qualitative direct ELISA method. Ten serum samples, identified as anti- IFN β
antibody positive, were selected for the reference pool which was arbitrarily assigned an anti-
IFNP antibody concentration of 100 Laboratory Units / mL. Serial serum samples of 20
patients on IFNβ -1β therapy were assayed using a standard curve generated from the
reference pool, and each assay included a set of sera from 5 healthy individuals. The intraassay
coefficient of variation (CV) was 6-10% and inter-assay CV was 3-8%. The validity of
the assay was assured through binding specificity, recovery and inhibition tests. Of 20
patients treated for 1-24 months, approximately 16 developed antibodies within the first three
months. Two antibody profiles were observed: one profile consisted of a rise and gradual
decline of antibodies to pretreatment levels, and a second profile characterized by a rise
which was followed by a decline to lower antibody levels that were maintained over the
course of treatment. Additionally, supernatants of cultured lymphocytes were assayed, using
a biotin-streptavidin amplified version of the sandwich-ELISA, and results indicate that some
patients secrete anti- IFNβ antibodies in vitro.
These findings confirm that IFNβ -1b is immunogenic in MS patients and that the
appearance of anti- IFNβ ' antibodies is an early phenomenon. The sandwich ELISA is a
specific, sensitive and reproducible method for the quantification of anti- IFNβ ' antibodies,
and can be easily adapted in any laboratory for the large-scale throughput monitoring of anti-
IFNP antibodies. The assay can also be employed as a tool to study the effects of anti-IFNP
antibodies on the therapeutic efficacy of IFNJ3 in MS patients, and the mode of action of
IFNp.Medicine, Faculty ofPathology and Laboratory Medicine, Department ofGraduat
