Antibody binding to Streptococcus mitis and Streptococcus oralis cell fractions.
OBJECTIVE
To determine which cell fraction(s) of Streptococcus mitis biovar 1 serve as the best source of antigens recognized by salivary SIgA antibodies in infants.


METHODS
Whole cells of 38 reference and wild-type isolates of S. mitis, Streptococcus oralis, Streptococcus gordonii, Enterococcus casseliflavus, and Enterococcus faecalis were fractionated into cell walls (CW), protease-treated cell walls (PTCW), cell membranes (CM) and cell protein (CP). Whole cells and these fractions were tested for binding by rabbit anti-S. mitis SK145 and anti-S. oralis SK100 sera, and also by salivary SIgA antibodies from infants and adults.


RESULTS
Anti-SK145 and anti-SK100 sera bound whole cells and fractions of all strains of S. mitis and S. oralis variably. Cluster analysis of antibody binding data placed the strains into S. mitis, S. oralis and 'non-S. mitis/non-S. oralis' clusters. Antigens from CW and CM best discriminated S. mitis from S. oralis. CM bound the most infant salivary SIgA antibody and PTCW bound the least. In contrast, adult salivary SIgA antibody bound all of the cell fractions and at higher levels.


CONCLUSIONS
Presumably the relatively short period of immune stimulation and immunological immaturity in infants, in contrast to adults, result in low levels of salivary SIgA antibody that preferentially bind CM of S. mitis but not PTCW. By utilizing isolated cell walls and membranes as sources of antigens for proteomics it may be possible to identify antigens common to oral streptococci and dissect the fine specificity of salivary SIgA antibodies induced by oral colonization by S. mitis.
Wirth
Katherine A
KA
Department of Microbiology and Immunology, Georgetown University Medical Center, Washington, DC, USA.
Bowden
George H
GH
Richmond
Dorothy A
DA
Sheridan
Michael J
MJ
Cole
Michael F
MF
D000328:Adult; D000367:Age Factors; D000818:Animals; D000907:Antibodies, Bacterial; D001666:Binding Sites, Antibody / Q000276:immunology; D002458:Cell Fractionation / Q000379:methods*; D013293:Enterococcus faecalis / Q000254:growth & development / Q000276:immunology*; D006801:Humans; D007071:Immunoglobulin A, Secretory / Q000276:immunology*; D007155:Immunologic Factors / Q000276:immunology; D007223:Infant; D009055:Mouth / Q000382:microbiology; D011817:Rabbits; D012463:Saliva / Q000276:immunology* / Q000382:microbiology; D034364:Streptococcus milleri Group / Q000254:growth & development / Q000276:immunology* / Q000378:metabolism
D000907:Antibodies, Bacterial; D007071:Immunoglobulin A, Secretory; D007155:Immunologic Factors