Analysis of the humoral response to the flagellin protein of Borrelia burgdorferi: cloning of regions capable of differentiating Lyme disease from syphilis.

Selected regions of the Borrelia burgdorferi flagellin gene (fla) that exhibit high or low homology with related genes from other bacterial species were amplified by the polymerase chain reaction and expressed as fusion proteins in Escherichia coli. Purified fusion proteins were assayed for antibody reactivity in a microtiter plate enzyme-linked immunosorbent assay with sera from Lyme disease patients as well as syphilitic and normal sera. Immunoglobulin G antibody from Lyme disease patient sera reacted predominantly with the central portion of the protein. The region of the flagellin protein encompassing amino acids 64 to 311 detected nearly all of the immunoglobulin G-positive Lyme sera and only reacted with 1 of 26 syphilis patient serum samples. In contrast, 12 of 26 syphilis patient serum samples and 2 of 47 normal serum samples reacted with the amino terminus of the flagellin protein, whereas 4 of 26 syphilis patient serum samples and 7 of 47 normal serum samples reacted with the carboxyl terminus. The central region containing amino acids 64 to 311 may be employed diagnostically to differentiate antibodies to B. burgdorferi from antibodies to Treponema pallidum. In addition, this region also was recognized by immunoglobulin M in the Lyme patient sera, indicating its potential usefulness as a marker for early Lyme disease.