Clinical profile of Msp genes in oral treponemes

Abstract

The major surface protein (Msp) of Treponema denticola is proposed to play a variety of roles central to the disease-causing activities of this oral spirochete bacterium. Msp proteins present in various T. denticola strains, and other closely-related treponeme species, exhibit significant sequence diversity and differing sero-reactivities. The precise relationship between Msp sequence composition and periodontal disease is poorly understood. OBJECTIVE: To investigate the diversity of msp gene sequences of oral treponeme bacteria present in sub-gingival bacteria sampled from periodontitis patients and healthy control. METHODS: Utilizing extensive msp gene sequence analysis, we designed consensus PCR primers capable of amplifying msp gene fragments from complex DNA mixtures. Consensus msp primers were used to analyze msp genotypes present in clinical samples of pooled subgingival plaque taken from 4 chronic periodontitis patients, and 1 healthy control. RESULTS: 76% of all sequenced clones (n=180) corresponded to msp gene homologs. 13 distinct msp genotypes were identified (95% similarity cut-off), belonging to strains of T. denticola (n=7) or T. vincenti/T.medium (n=6). 4-5 msp genotypes were present in each subject. Notably, 11 msp genotypes were novel, accounting for 88% of all clones obtained. One novel msp genotype was highly-abundant (60/137 clones), and was present in all four periodontitis samples but not in healthy control. CONCLUSION: Msp genes from oral phylogroup 1 and 2 treponemes were detected in all subjects. One dominant msp clone may be associated with periodontal disease. Our study notably indicates that there are high levels of msp gene diversity awaiting discovery in all patient types.