Multiple alleles of Treponema pallidum repeat gene D in Treponema pallidum isolates

Abstract

Two new tprD alleles have been identified in Treponema pallidum: tprD2 is found in 7 of 12 T. pallidum subsp. pallidum isolates and 7 of 8 non-pallidum isolates, and tprD3 is found in one T. pallidum subsp. pertenue isolate. Antibodies against TprD2 are found in persons with syphilis, demonstrating that tprD2 is expressed during infection.

FIG. 1

Diagram of the tprD locus. Three different alleles of tprD (tprD, tprD2, and tprD3) are present in the tprD locus in the strains examined. The regions denoted as arrows and with TP or tpr are predicted coding regions with putative start codons at the beginning of the arrow and putative stop codons at the point of the arrow. IGR, intergenic region. PCR products are shown as thin lines, and the primers used to produce the products are shown as arrowheads. The different shading patterns and lines within the tprD, tprD2, and tprD3 alleles demonstrate the differences between the alleles.

FIG. 2

Amino acid sequence alignments of tprD, tprD2, and tprD3. The alignments of the predicted amino acid sequences of the tprD, tprD2, and tprD3 alleles are shown.

FIG. 3

Western blots demonstrating antibodies in sera from persons with secondary syphilis react with the TprD2-specific peptide. Shown are immunoblots with the 14-kDa TprD2-specific recombinant peptide from a representative experiment. The immunoblots were reacted with sera from two uninfected controls (U), five persons with secondary syphilis (noted by no. 2), and two persons with late latent syphilis (LL). Antibody reactivity to the tprD2-specific peptide is seen with the sera from three of five persons with secondary syphilis. Shown to the right are the positions of the molecular mass markers.