CHARACTERIZATION OF AN ANTIPROLIFERATIVE SURFACE-ASSOCIATED PROTEIN FROM ACTINOBACILLUS-ACTINOMYCETEMCOMITANS WHICH CAN BE NEUTRALIZED BY SERA FROM A PROPORTION OF PATIENTS WITH LOCALIZED JUVENILE PERIODONTITIS

The gentle agitation of suspensions of Actinobacillus actinomycetemcom itans serotype a, b, or c in saline resulted in the release of a prote inaceous surface-associated material (SAM) which produced a dose depen dent inhibition of tritiated thymidine incorporation by the osteoblast -like cell line MG63 in culture, This cell line was sensitive to low c oncentrations of SAM (50% inhibitory concentration, 200 ng/ml for sero type c), Immunoglobulin G antibodies to constituents of the SAM were f ound in the blood of patients with localized juvenile periodontitis (L JP). Sera from 9 of 16 patients with LJP significantly neutralized the antiproliferative activity of the SAM, while sera from 15 controls, w ith no evidence of periodontal disease, were unable to neutralize this activity. Neutralization was not directly related to the patient's an tibody titer to the whole SAM. Characterization of the antiproliferati ve activity in the SAM demonstrated that it was not cytotoxic and was heat and trypsin sensitive, The active component separated in a well-d efined peak in anion-exchange high-performance liquid chromatography ( HPLC) which, when further analyzed by size exclusion HPLC, revealed a single active peak, which had an apparent molecular mass of approximat ely 8 kDa. The lipopolysaccharide from A. actinomycetemcomitans was on ly weakly active, SAM from Porphyromonas gingivalis W50 and Eikenella corrodens NCTC 10596 did not exhibit any antiproliferative activity wi th this cell line, even at concentrations as high as 10 mu g/ml. This study has shown that SAM from A. actinomycetemcomitans contains a pote nt antiproliferative protein whose activity can be neutralized by anti bodies in the sera from some patients with LJP.