Abstract
A highly sensitive enzyme-linked immunosorbent assay was used for the analysis of serum IgG reactivity against specific immunogenic Treponema pallidum proteins. Outer membrane treponemal proteins purified by preparative SDS-polyacrylamide gel electrophoresis were used as antigenic probes at concentrations as low as 100 ng per ml (5 ng per well in microtitre plates). Detection of anti-treponemal antibody was possible using rabbit syphilitic sera diluted to 1/10 000. The sensitivity of the assay was equal to or greater than that detected by radioimmuno-precipitation combined with gel electrophoresis and fluorography techniques and was capable of monitoring host IgG responses throughout the progress of the disease.