Automated, quantitative microhemagglutination assay for Treponema pallidum antibodies.

An automated, quantitative microhemagglutination assay for antibodies to Treponema pallidum was developed by using T. pallidum-sensitized erythrocytes and an automatic serial-dilution instrument. Reactivity was found in sera from 54 rabbits and 6 chimpanzees infected with T. pallidum. Reactivity was also found in sera from animals infected with T. pertenue, T. carateum, and T. cuniculi. No reactivity was found in sera from 75 normal rabbits or from 129 rabbits immunized with cultivatable treponemes or a variety of other bacteria. In approximately 3 min, 13 twofold serial dilutions of each of 8 preabsorbed sera and the addition of sensitized erythrocytes to each dilution were accomplished automatically. The automated assay can serve as a research tool in quantitating antibodies to pathogenic treponemes, and evaluation of its clinical usefulness seems warranted.