Objectives: In this study, we characterized conserved surface antigens in representative oral spirochetes (T. denticola, T. lecithinolyticum, and T. socranskii subsp. socranskii) that are homologs of Treponema pallidum Tp92 with opsonophagocytic potential and protective capacity against syphilis. Methods: The tp92 gene homologs were identified from the genome sequence of T. denticola and by sequencing of PCR products of the genes that were amplified with degenerate and specific primers in T. lecithinolyticum, and T. socranskii subsp. socranskii. The tp92 gene homologs were expressed in E. coli using the pQE-30 vector after PCR and TA cloning. Polyclonal antibodies were raised against T. denticola Tp92 homolog in rabbits and used for binding and coaggregation experiments. Biological activities of the recombinant Tp92 homologs were assessed in monocytes by real-time PCR, ELISA, and gelatin zymography. Results: Tp92 homologs of three oral spirochetes have the molecular mass of 88-92 kDa and show the amino acid sequence identity of 37.9-49.3% and similarity of 54.5-66.9% with Tp92. The sequence identity and similarity between oral spirochetes ranged 41.6-47.1% and 59.9-66.7%, respectively. The tp92 gene homologs were successfully expressed in E. coli and the recombinant proteins were purified. IgG fraction of antiserum raised against the recombinant protein of T. denticola Tp92 homolog (rTd92) cross-reacted with diverse oral spirochetes and inhibited the attachment of T. denticola to KB cells, an oral epithelial cells, and the coaggregation of T. denticola with Fusobacterium nucleatum. Recombinant proteins of the Tp92 homologs stimulated various factors in monocytes that are involved in inflammation and tissue destruction like ICAM-1, IL-1â, TNF-á, IL-6, IL-8, COX-2 (PGE2), and MMP-9. Conclusions: Our results demonstrate that Tp92 homologs of oral spirochetes are highly conserved and may play an important role for cell attachment and bacterial coaggregation. As well, the conserved proteins may have a role in inflammatory responses in host.

Back to the Microbiology / Immunology and Infection Control Program
Back to the IADR General Session & Exhibition (June 28 – July 1, 2006)

Top Level Search