Molecular aspects of immunoglobulin A1 degradation by oral streptococci

Abstract

Using a panel of 143 strains classified according to a novel taxonomic system for oral viridans-type streptococci, we reexamined the ability of oral streptococci to attack human immunoglobulin Al (IgAl) molecules with IgAl protease or glycosidases. IgAl protease production was an exclusive property of all strains belonging to Streptococcus sanguis and Streptococcus oralis (previously S. mitior) and of some strains of Streptococcus mitis biovar 1. These are all dominant initiators of dental plaque formation. Degradation of the carbohydrate moiety of IgAl molecules accompanied IgAl protease activity in S. oralis and protease-producing strains of S. mitis biovar 1. Neuraminidase and I8-galactosidase were identified as extracellular enzymes in organisms of these taxa. By examination with enzyme-neutralizing antisera, four distinct IgAl proteases were detected in S. sanguis biovars 1 to 3, S. sanguis biovar 4, S. oralis, and strains of S. mitis, respectively. The cleavage of IgAl molecules by streptococcal IgA proteases was found to be influenced by their state of glycosylation. Treatment of IgAl with bacterial (including streptococcal) neuraminidase increased susceptibility to protease, suggesting a cooperative activity of streptococcal IgAl protease and neuraminidase. In contrast, a decrease in susceptibility was observed after extensive deglycosylation of the hinge region with endo-cL-N acetylgalactosaminidase. The effector functions of IgA antibodies depend on the carbohydrate-containing Fc portion. Hence, the observation that oral streptococci may cleave not only the al chains but also the carbohydrate moiety of IgAl molecules suggests that the ability to evade secretory immune mechanisms may contribute to the successful establishment of these bacteria in the oral cavity. 1186 on August 5, 2020 by guest http://iai.asm.org/ Downloaded from

Ecology of viridans streptococci in the oral cavity and pharynx

“…Pharyngeal strains belonged mainly to biovars C and D, whereas isolates from mature supragingival plaque were predotninantly biovar B. In contrast, subgingival plaque isolates were almost exclusively of biovar A. Eighty of the S. anginosus isolates from subgingival plaque and 176 from other sites in the oropharyngeal cavities were tested for neuratninidase activity tneasured by alteration of the electrophoretic mobility of IgAl in immunoelectrophoresis (21). Of the subgingival S. atiginosus strains, 88% had this activity, in contrast to 8% of S. anginosus strains isolated from other sites.…”

Immunoglobulin A1 protease: A new therapeutic candidate for immunoglobulin A nephropathy

“…31,32 Whereas other reports found that removal of the O-linked carbohydrate in the hinge region made IgA1 less susceptible to cleavage by IgA1 protease. 33,34 It should be noted that none of these studies was performed based on the IgA1 collected from IgAN patients. Therefore, further studies on IgA1 of IgAN patients are needed to resolve this dispute.…”

Salivary proteins promote proteolytic activity in Streptococcus mitis biovar 2 and Streptococcus mutans

“…As a group, oral streptococci can degrade both the peptide backbone and the glycan moieties of the human glycoprotein immunoglobulin A1 but few individual species are able to digest both (Cole et al, 1999;Grønbaek Frandsen, 1999). For instance, S. mitis biovar 1 and S. oralis produce a human immunoglobulin A1 protease, while S. mitis biovar 2 is capable of removing sialic acid, galactose and N-acetylgalactosamine from the molecule (Reinholdt et al, 1990). However, supragingival plaque from macaque monkeys, containing a mixed-species consortium of oral bacteria, has been reported to express both exoglycosidases as well as a wide range of proteolytic activities in the absence of dietary nutrients (Smith & Beighton, 1986.…”