Quantitative immunoassay of anti-La antibodies using purified recombinant La antigen.

A purified recombinant La fusion protein was tested in an enzyme-linked immunosorbent assay to quantitate anti-La responses. This protein contained the immunodominant region of the La molecule fused to beta-galactosidase. In solid-phase assays, recombinant La protein was solubilized in urea and bound to polystyrene wells without loss of immunoreactivity. The recombinant-based enzyme-linked immunosorbent assay proved to be a sensitive method for the detection of anti-La binding, and it accurately distinguished anti-La precipitin positive sera from normal sera.