Expression and functional properties of the Streptococcus intermedius surface protein antigen I/II

Streptococcus intermedius is associated with deep-seated purulent infection s. In this study, we investigated expression and functional activities of a ntigen VII in S, intermedius, The S, intermedius antigen I/II appeared to b e cell surface associated, with a molecular mass of approximately 160 kDa, Northern blotting indicated that the S, intermedius NCTC 11324 antigen VII gene was transcribed as a monocistronic message. Maximum expression was see n during the early exponential phase, Insertional inactivation of the antig en I/II gene resulted in reduced hydrophobicity during early exponential ph ase, whereas no effect was detected during mid- and late exponential phases . Binding to human fibronectin and laminin was reduced in the isogenic muta nt, whereas binding to human collagen types I and IV and to rat collagen ty pe I was not significant for either the wild type or the mutant. Compared t o the wild type, the capacity of the isogenic mutant to induce interleukin 8 (IL-8) release by THP-1 monocytic cells was significantly reduced. The re sults indicate that the S. intermedius antigen I/II is involved in adhesion to human receptors and in IL-8 induction.