Line immunoassay and enzyme-linked line immunofiltration assay for simultaneous detection of antibody to two treponemal antigens.

Two enzyme immunoassays, the line immunoassay (LIA) and the enzyme-linked line immunofiltration assay (ELLIFA), were studied for suitability in the serodiagnosis of syphilis. In both assays, antibody to treponemes was detected using the recombinant DNA derived treponemal protein TmpA and the purified axial filament derived from the Reiter treponeme. The antigens were applied in parallel lines onto nitrocellulose membranes. The sensitivity and specificity of both assays were compared with that of the Treponema pallidum hemagglutination assay (TPHA), the fluorescent treponemal antibody absorption test, and the axial filament and TmpA enzyme-linked immunosorbent assays. The sensitivity and specificity of the LIA and the ELLIFA were found to be comparable to that of the TPHA using serum samples from 65 untreated syphilitic patients, 95 patients treated for syphilis and 60 blood donors, except in the case of the LIA using axial filament. This latter test was slightly less sensitive in primary and early latent syphilis than the TPHA. In the LIA procedure, serum antibodies to two antigens could be detected simultaneously within two hours. This assay may be useful for fieldwork. In the ELLIFA procedure, antibodies to the two antigens could be detected simultaneously within 15 minutes. The ELLIFA procedure may provide a multiple antigen test with a very short assay operation time.