Porphyromonas gingivalis is among the major etiological pathogens of chronic periodontitis. The virulence mechanisms of P. gingivalis is yet to be identified as its activity is largely unknown in actual disease process. The purpose of this study is to identify antigens of P. gingivalis expressed only in patients with chronic periodontitis using a unique immunoscreening technique. Change Mediated Antigen Technology (CMAT), an antibody-based screening technique, was used to identify virulence-associated proteins of P. gingivalis that are expressed only during infection stage in patients having chronic periodontitis. Out of 13,000 recombinant clones screened, 22 tested positive for reproducible reactivity with rabbit hyperimmune anti-sera prepared against dental plaque samples acquired from periodontitis patients. The DNA sequences of these 18 genes were determined. CMAT-identified protein antigens of P. gingivalis included proteins involved in energy metabolism and biosynthesis, heme and iron binding, drug resistance, specific enzyme activities, and unknown functions. Further analysis of these genes could result in a novel insight into the virulence mechanisms of P. gingivalis.

Introduction
 Materials and Methods
  Bacterial strains and growth conditions
  Construction of genomic expression libraries of P.gingivalis ATCC 33277
  Collecting dental plaque samples containing P.gingivalis and preparing hyperimmune antisera
  Serum adsorption
  Screening for recombinant proteins uniquely expressed in vivo
  Identifying genes isolated by CMAT
  Predicting functions of antigens identified by CMAT
 Results
  Adsorption of rabbit hyper-immune antisera
  Genomic library construction and screening
  Identification and functional classification of P.gingivalis genes identified by CMAT
 Discussion
 References

• Hye-Jung Kim(Department of Dental Education, School of Dentistry, Dental Research Institute, Chonnam National University)
• Seok-Woo Lee(Department of Dental Education, School of Dentistry, Dental Research Institute, Chonnam National University, Department of Periodontology, School of Dentistry, Dental Research Institute, Chonnam National University) Correspondence to