A surface plasmon resonance biosensor assay for measurement of anti-GM1 antibodies in neuropathy

Objective: To develop a rapid assay for the detection and measurement of anti-GM(1) ganglioside antibodies in patients with neuropathy, using a surface plasmon resonance-based biosensor. Background: Elevated levels of anti-GM(1) ganglioside antibodies are observed in patients with acute and chronic motor neuropathies. Assays for detecting anti-GM(1) antibodies in serum are increasingly being used to help the physician in the evaluation of these patients. Methods: Antigens were immobilized by adsorption of GM(1) (active) and GM(2) (control) gangliosides onto a dextran-based sensor chip which is in contact with a flow cell carrying the sample. Interaction of specific antibodies directed against GM(1) with the ganglioside-coated sensor chip caused a change in refractive index at the surface of the chip, which was detected by an optical sensor, using the phenomenon of surface plasmon resonance. Sera from patients and healthy individuals were analyzed by the new assay and results were compared with those from ELISA. Anti-GM, antibody isotype was identified by using a secondary antibody. Results: The binding of anti-GM(1) antibodies to the immobilized GM(1) was observed in real time after reference subtraction of the response from GM(2) control. The response was proportional to antibody concentration. The assay exhibited high specificity for sera from patients with multifocal motor neuropathy and Guillain-Barre syndrome with antibodies against GM(1). Conclusions: The surface plasmon resonance biosensor assay offers a rapid system for directly measuring antibody levels in serum without the use of any labels, while comparing favorably with the ELISA system in sensitivity and specificity.