Highly sensitive-beta-D-galactosidase-linked immunosorbent assay for anti-myelin basic protein antibody.

A highly sensitive enzyme-linked immunosorbent assay (ELISA) procedure has been devised for the determination of anti-myelin basic protein antibodies. First, rabbit anti-myelin basic protein (MBP) sera to be assayed were incubated with MBP immobilized on small pieces of silicone rubber. Next, anti-MBP bound specifically to the solid phase was allowed to react either with Fab' of guinea pig anti-rabbit IgG conjugated with beta-D-galactosidase from Escherichia coli or with protein A conjugated with beta-D-galactosidase. The amount of fixed anti-MBP antibodies was assayed by fluorometric determination of the enzyme activity using 4-methylumbelliferyl-beta-D-galactoside as a substrate. The sensitivity of the present assay was at least an order of magnitude higher than the hitherto available radioimmunoassay and ELISA.