INVASION OF DENTINAL TUBULES BY ORAL STREPTOCOCCI IS ASSOCIATED WITH COLLAGEN RECOGNITION MEDIATED BY THE ANTIGEN I II FAMILY OF POLYPEPTIDES/

Cell surface proteins SspA and SspB in Streptococcus gordonii and SpaP in Streptococcus mutans are members of the antigen I/II family of pol ypeptides produced by oral streptococci. These proteins are adhesins a nd mediate species-specific binding of cells to a variety of host and bacterial receptors. Here we show that antigen I/II polypeptides are i nvolved in the attachment of oral streptococci to collagen and that th ey also determine the ability of these bacteria to invade human root d entinal tubules, Wild-type S. gordonii DL1 (Challis) cells shelved hea vy invasion of tubules to a depth of approximately 200 mu-m, whereas t he abilities of cells of isogenic mutant strains OB220 (sspA) and OB21 9 (sspA sspB) to invade were 50 and >90% reduced, respectively, Likewi se, wild-type S. mutans NG8 cells invaded dentinal tubules, whereas ce lls of isogenic mutant strain 834 (spaP) did not. The invasive abiliti es of strains OB220 and OB219 were restored by heterologous expression of S. mutans SpaP poll peptide in these strains. The extents of tubul e invasion by various wild-type and mutant strains correlated with the ir levels of adhesion to type I collagen, a major component of dentin. Furthermore, S. gordonii DL1 cells exhibited a growth response to col lagen by forming long chains. This was not shown by sap mutants but wa s restored by the expression of SpaP in these cells. The production of SspA polypeptide by S. gordonii DL1, but not production of SspB polyp eptide by strain OB220 (sspA), was enhanced in the presence of collage n. These results are the first to demonstrate that antigen I/II family polypeptides bind collagen and mediate a morphological growth respons e of streptococci to collagen. These antigen Till polypeptide activiti es are critical for intratubular growth of streptococci and thus for e stablishment of endodontic infections.