IgA1 proteases of oral streptococci: ecological aspects.

The ecology and identity of IgA1 protease-producing streptococci in the human oral cavity were studied in an attempt to obtain insight into the significance of IgA1 proteases for host-parasite relationships. Contrary to previous observations, a detailed taxonomic analysis of oral streptococci revealed that all strains of S. sanguis and S. oralis ("S.mitior") produced IgA1 protease. In addition, IgA1 protease activity was observed in some isolates of S.mitis. Of the streptococci that initiate plaque formation on dental enamel 88% (median value) had IgA1 protease activity. Low proportions of the streptococci that colonize the tongue and oropharyngeal mucosae produced IgA1 protease, in contrast to 60% of streptococci isolated from buccal mucosa. The IgA1 proteases from S. sanguis I-III, S. sanguis IV, S. oralis, and S.mitis were distinct as revealed by studies using enzyme-neutralizing antibodies.