Treponema pallidum Major Sheath Protein Homologue Tpr K Is a Target of Opsonic Antibody and the Protective Immune Response

Abstract

We have identified a family of genes that code for targets for opsonic antibody and protective immunity in T. pallidum subspecies pallidum using two different approaches, subtraction hybridization and differential immunologic screening of a T. pallidum genomic library. Both approaches led to the identification of a polymorphic multicopy gene family with predicted amino acid homology to the major sheath protein of Treponema denticola. One of the members of this gene family, tpr K, codes for a protein that is predicted to have a cleavable signal peptide and be located in the outer membrane of the bacterium. Reverse transcription polymerase chain reaction analysis of T. pallidum reveals that Tpr K is preferentially transcribed in the Nichols strain of T. pallidum. Antibodies directed to purified recombinant variable domain of Tpr K can opsonize T. pallidum, Nichols strain, for phagocytosis, supporting the hypothesis that this portion of the protein is exposed at the surface of the treponeme. Immunization of rabbits with the purified recombinant variable domain of Tpr K provides significant protection against infection with the Nichols strain of T. pallidum. This gene family is hypothesized to be central to pathogenesis and immunity during syphilis infection.

Role of Treponema Denticola in Periodontal Diseases

“…The recent complete T. pallidum genome sequence (Fraser et al, 1998) revealed that the T. pallidum chromosome encodes 12 polypeptides with sequence relatedness to the major outer sheath of T. denticola (Centurion-Lara et al, 1999). Comparison of the T. pallidum genome sequence with that of B. burgdorferi identified unique and common genes and substantiates the considerable diversity observed among pathogenic spirochetes.…”

Syphilis: using modern approaches to understand an old disease

“…Although T. pallidum has few integral outer membrane proteins (23,24,77,78), bioinformatic approaches have identified several candidates, including members of the family of 12 T. pallidum repeat (Tpr) proteins (79,80). Among Tpr family members, TprK is the best studied.…”

Segregation of B and T Cell Epitopes of Treponema pallidum Repeat Protein K to Variable and Conserved Regions During Experimental Syphilis Infection

“…The amplicons from T. pallidum Seattle Nichols strain DNA were cloned into the pRSET expression vector (Invitrogen, Carlsbad, CA), the sequence was verified, and the peptide was expressed in Escherichia coli and purified as previously described (7,13). The proteins were dialyzed into PBS, pH 7.2, size confirmation and purity were evaluated by SDS-PAGE, and concentrations were determined using a bicinchoninic acid protein assay (Pierce, Rockford, IL).…”

“…In the search for T. pallidum subspecies pallidum virulence factors, members of a family of 12 genes called Treponema pallidum repeat (tpr) 3 genes A-L were identified (7)(8)(9). In an organism that lacks major biosynthetic capacity, devoting 2% of its small genome to the tpr gene family is quite remarkable and suggests the importance of the tpr gene family to the organism.…”

“…In an organism that lacks major biosynthetic capacity, devoting 2% of its small genome to the tpr gene family is quite remarkable and suggests the importance of the tpr gene family to the organism. We have reported that when one member of this family, Treponema pallidum repeat protein K (TprK), is used as an immunogen, lesion development is attenuated following homologous challenge in the rabbit model (7). Although Hazlett et al (10) failed to corroborate these results, we have confirmed and expanded the original results to show that immunizing with the N-terminal portion (aa 37-273) of TprK retards lesion development (manuscript in preparation) as previously seen with a larger fragment (aa 37-348) (7).…”