VIRULENCE CHARACTERISTICS OF ORAL TREPONEMES IN A MURINE MODEL

This study was designed to investigate the virulence characteristics o f Treponema denticola, T. socranskii, T. pectinovorum, and T. vincenti i following challenge infection of mice. These microorganisms induced well-demarcated, dose-dependent, raised subcutaneous (s.c.) abscesses which were similar in time of onset, lesion progression, and duration of healing, Only viable cells were capable of inducing these character istic s.c. abscesses, Histological examination of the skin lesion 3 an d 5 days postinfection revealed abscess formation in the s.c. tissues, and abundant spiral organisms were demonstrated to be present in the abscess, Host resistance modulation by dexamethasone (neutrophil alter ation) and cyclophosphamide (neutrophil depletion) pretreatment had a minimal effect on the virulence expression by any of these treponemes. The T. denticola isolates demonstrated significant trypsin-like prote ase (TLPase) activity, while both T. socranskii and T. vincentii were devoid of this activity. Interestingly, T. pectinovorum strains were h eterogeneous with respect to TLPase as high producers, low producers, and nonproducers. However, no differences in lesion formation were not ed regardless of whether the species expressed this proteolytic activi ty or whether treatment with N alpha-p-tosyl-L-lysine chloromethyl ket one (TLCK) and dithiothreitol was performed, These results showed that (i) a murine model may be used to evaluate virulence expression by or al treponemes; (ii) while TLPase activity varies among the oral trepon emes, this protease does not appear to participate in abscess inductio n in the mouse model; and (iii) T. pectinovorum strains show variation in TLPase activity.