Latex spheres as immunologic markers to demonstrate the binding of human salivary immunoglobulins to Streptococcus mutans

The results of this study indicate that latex beads can be used to identify specific antigen-antibody interactions on the surface of bacterial cells. The application of a Labelling Index allowed specific interactions to be quantitatively distinguished from non-specific latex bead attachments. The labeling indexes for latex beads absorbed to anti-salivary immunoglobulins were significantly higher than for negative control indexes when tested against S mutans treated with saliva. Conversely, there was no significant difference when they were tested against nonoral bacteria treated with saliva. This suggests that both whole and parotid human saliva contained specific antibodies against S mutans.

Naturally occurring secretory immunoglobulin A antibodies to Streptococcus mutans in human colostrum and saliva

Human colostrum, parotid saliva, and serum were assayed for the presence of naturally occurring antibodies to five serotypes of Streptococcus mutans. Appreciable levels of agglutinins to strains AHT, BHT, 10449, 6715, and LM-7 (groups a leads to e, respectively) were detected in normal colostrum and saliva, whereas relatively low levels were found in serum. No agglutinins could be detected in the colostrum or saliva of immunodeficient patients. Molecular sieve chromatography of the colostrum on Sephadex G-200 revealed agglutinin activity in the secretory immunoglobulin A (s-IgA)-rich fraction only. Titration of purified colostral s-IgA confirmed the IgA nature of this agglutinating activity. Indirect immunofluorescence tests with anti-s-IgA, -IgG, and -IgM revealed S. mutans specificity only in the s-IgA class. The presence of s-IgA antibodies to indigenous oral microorganisms in colostrum, as well as in saliva, suggests that antigenic stimulation occurs at a site remote from the oral mucosa.

Chemical and immunological properties of the type f polysaccharide antigen of Streptococcus mutans

The type-specific cell wall polysaccharide antigen was extracted, purified, and characterized from type f Streptococcus mutans strain OMZ175 and MT557. The antigen was extracted from lyophilized cells with 5% trichloroacetic acid at 85 C for 15 min or saline at 120 C for 30 min. The trichloroacetic acid antigen was chromatographically separated into three antigenic fractions on a diethylaminoethyl-Sephadex A-25 column. Antigen 1 (Ag1P), which was specific for type f antiserum, was further purified by passing through carboxymethyl-Sephadex C-25 and Sephadex G-200 columns. It was a polysaccharide composed of 49% rhamnose and 47% glucose. No reaction was obtained with anti-polyglycerophosphate (PGP) serum. Antigen 2 was reactive with both type f and PGP antisera and contained significant amounts of protein and phosphorus. Antigen 3 was reactive only with PGP antiserum and had no type specificity. The polysaccharide antigen gave a single precipitin band against type-specific antiserum on immunodiffusion and immunoelectrophoresis. The presence of alpha-1,6-glucosidic linkages was indicated by a 90% inhibition of the precipitin reaction by isomaltose and alpha-methyl-D-glucopyranoside, adsorption to and release from a concanavalin A-Sepharose column, and reaction with an S. mutans (type e) glucan antiserum. This antiserum was used to show that the type f polysaccharide antigen did not contain free glucan. An analysis of the antigen released from the antigen-glucan antiserum complex showed the presence of rhamnose and glucose. This released antigen also reacted with an f antiserum, which did not react with commercial dextran. The results show that the type f polysaccharide antigen is the first of those S. mutans type-specific polysaccharides identified to be immunologically related to an S. mutans glucan.

Purification and immunochemical characterization of type e polysaccharide antigen of Streptococcus mutans

The type-specific antigen of Streptococcus mutans strain MT703, serotype e, has been chromatographically purified and characterized. Two chromatographic fractions were obtained from saline extracts which reacted with both anti-MT703 whole-cell serum and Lancefield group E serum. The major fraction (eI) was identified as a polysaccharide composed of 37% glucose, 56% rhamnose, 5% protein, and 0.3% phosphorus, whereas the minor fraction (eII) contained 66% protein in addition to 10% glucose and 17% rhamnose. The immunological specificity of these antigens was found to be the same by immunodiffusion in agar gel. Another fraction with a negative charge (eIII) reacted with polyglycerophosphate antisera from Streptococcus mutans and Streptococcus pyogenes. For comparison, the MT703 antigen in a hot trichloroacetic acid extract (eA) and the group E antigen from a saline extract of cells of strain K129 (EI) were similarly purified by anionic ion-exchange chromatography. Although the ratio of glucose and rhamnose in eA was 1:0.9 and in eI and eII approximately 1:1.5, reactions of identity were obtained in gel diffusion against specific anti-e serum. This difference in ratio is probably a result of the extraction procedures. Both the type e and group E antisera were reactive with both eI and EI antigens. The adsorption of group E antiserum with MT703 cells removed all E antibody, whereas type e-specific antibody remained after adsorption with K129 cells. These results suggest that eI antigen possesses both e and E specificities, whereas EI possesses E only. These findings were supported by the quantitative precipitin test and immunodiffusion and/or immunoelectrophoretic patterns in agar gel. Methyl-beta-D-glucopyranoside markedly inhibited the precipitin reaction in both type e and group E sera. However, a significantly stronger inhibition by cellobiose of type e serum than of group E serum indicates that a beta-linked glucose-glucose dimer is the predominant antigenic determinant of the e specificity. The presence of both e and E specificities on a single polysaccharide molecule was demonstrated by the use of purified e antigen released from a specific e-anti-e complex. This antigen reacted with a group E-specific serum as well as a type e-specific serum. An examination of five S. mutans type e strains showed the presence of group E specificity also, whereas the I, II, and IV serotypes of group E streptococci only possessed the group E specificity.

Ingestion of Streptococcus mutans induces secretory immunoglobulin A and caries immunity

Ingestion of killed cells of a highly cariogenic strain of Streptococcus mutans induced specific antibodies in both saliva and milk but not in serum of gnotobiotic rats. These antibodies were associated with the immunoglobulin A class. When infected with Streptococcus mutans, orally immunized animals developed significantly fewer carious lesions than nonimmunized infected controls.

Differential inhibition of Streptococcus mutans in vitro adherence by anti-glucosyltransferase antibodies

Antibodies prepared against an insoluble-soluble glucan-synthesizing fraction significantly inhibited in vitro adherence of Streptococcus mutans, whereas antibodies directed against a soluble glucan-synthesizing fraction were much less inhibitory.

Electron microscopy of antibody-labelled cells of Streptococcus mutans

Examination of immune complexes between cells of Streptococcus mutans and homologous antiserum by the techniques of thin-sectioning and freeze-etching revealed that the cells were embedded within and extensive matrix 80-90 nm thick with defined boundaries.

Serum glucosyltransferase-inhibiting antibodies and dental caries in rhesus monkeys immunized against Streptococcus mutans

Serum antibodies to glucosyltransferase (GTF) of Streptococcus mutans serotype c were assayed sequentially by means of an enzyme inhibition radio-assay in twenty-six Rhesus monkeys immunized with S. mutans. Pre-immune and control sera had a GTP-enhancing effect which was shown also by albumin and non-immune immunoglobulin fractions. GTF-inhibitory activity was found in IgG fractions from some immune sera and could be absorbed by S. mutans cells possessing cell-bound GTF. Inhibitory antibodies to GTF developed in the sera of four monkeys immunized with hydroxylapatite extract of culture supernatant (HACS), and in four out of fifteen monkeys immunized with S. mutans cells, but in none of the seven sham-immunized control animals. The monkeys immunized with HACS showed no reduction in caries. A correlation has been demonstrated between protection against caries and the early development of serum IgG antibodies to antigens present in HACS but there was no consistent association between protection against caries and GTF-inhibitory antibodies. The results also suggest the possibility that other antibodies, possibly present in the IgM or IgA fractions and having an enhancing effect on GTF, may increase the incidence of caries.

Effective immunity to dental caries: studies of active and passive immunity to Streptococcus mutans in malnourished rats

The present studies suggest that rat dams passively transfer IgG to their offspring via milk. Furthermore, rat dams hyperimmunized to S mutans after intravenous administration of this bacterium have serum-precipitating antibody to S mutans group-specific antigen. This serum precipitin was also observed in serums of their offspring during the suckling period and was detectable for a week after weaning. When these offspring were infected with S mutans on the day of weaning, significantly fewer smooth surface lesions developed in them than in infected rats reared on nonimmunized mothers. These results suggest that anti-S mutans antibody, perhaps of the IgG2a class, is passively transferred from mother to offspring via the milk. Furthermore, this antibody is probably important in protection against S mutans infection. In this regard, recent studies by Lehner, Challacombe, and Caldwell have suggested that crevicular fluid transudating serum antibodies are important in the prevention of dental caries in rhesus monkeys. From our studies and others, it is becoming clear that at least two sources and classes of antibody are important in caries immunity. Secretory IgA, produced and secreted into saliva after local injection can be correlated with protection. At the same time, serum antibody (presumably IgG) either passively or actively derived also gives immune protection. Further studies must clarify the precise role of these Ig's and their possible synergistic activity with other specific immune factors in saliva in order to determine the mechanism(s) involved in effective caries immunity.

Immunization experiments using the rodent caries model

Taken together, the immunization experiments which have been performed in the rat caries model system appear to suggest a correlation between the presence of salivary antibody to S mutans and reductions in caries caused by these bacteria. However, the multifactorial nature of this disease does not permit at present the conclusion that the presence of this antibody is both necessary and sufficient to give rise to the demonstrated effects on pathogenesis. To clarify the role of salivary antibody, several refinements may be required in the current model. Immunization procedures that elicit only a local antibody response would both simplify interpretations of effects and would be more desirable for use as a vaccine. Such procedures might include intraductal installation of antigen in the parotid gland which has been demonstrated to result in this type of response. An additional refinement stems from the knowledge that the kinds of immunization procedures currently used stimulated both cellular immune and soluble antibody systems, potentially giving rise to a rather broad spectrum of immune responses. Therefore, it might be useful to study the effects on S mutans pathogenesis in rats in which certain of these responses have been repressed, for example, by thymectomy, antilymphocyte serum, and so on. Also, each of these approaches would be measurably enhanced by more sensitive techniques to monitor immunological events in the oral cavity. Refinements in the selection and use of relevant antigens of S mutans also are necessary to delineate the in vivo mechanism of immunological interference in the pathogenesis of cariogenic streptococci. Approaches involve the use of purified GTF antigens or cell surface antigens both in the investigation of these mechanisms in in vitro models using antibody specifically directed to these antigens and in rat immunization experiments using immunogenic preparations of these materials. In addition, alterations in the diet and challenge dosage of infecting cariogenic organisms might permit more sensitive detection of effects in vivo. Clearly, the evidence suggests immunological interference with S mutans pathogenesis in the rat model system. However, several gaps exist in our basic understanding of this interference and of the appropriate system in which to observe these effects. The potential significance of this phenomenon should spur efforts to fill these gaps to establish definitively the role of immunity as an ecological determinant in the oral cavity.

Interactions of antisera, sera, and oral fluid with glucosyltransferases

Partially purified glucosyltransferases (GTF) isolated from Streptococcus mutans OMZ 176 and respective rabbit antisera were used to study enzyme-antibody interactions. A comparison between sensitive serological techniques and a functional inhibition test based on a radioenzyme assay demonstrated that the latter test system was the only one that discriminated between different antisera. Positive reactions in high dilutions in the former test systems were explained by the involvement of non-GTF contaminants and/or antibodies against enzyme regions distant to the catalytic site. The minute cross-reactions between two enzyme fractions and the respective antisera in the functional inhibition test indicated that the two immunogens contained mainly GTF that differed in the structure of their catalytic region. Control rabbit sera, rat oral fluid, and insoluble and soluble glucans considerably activated the GTF eluted with a 0.5 M phosphate buffer from hydroxapatite. It is suggested that these enzymes had additional binding sites for macromolecules inherent to rabbit sera and rat oral fluid, respectively, and that the observed increase in enzyme activity was due to a more stable enzyme conformation. Possibly the stimulation of GTF by the soluble glucan fraction was caused by a primer and/or acceptor function; however, this was not the case of the insoluble glucan. A stable complex was formed in the absence of the enzyme substrate, sucrose, the activity of which was not readily enhanced. It is concluded that the GTF of strain OMZ 176 are composed of multiple, multi-reactive molecules that enable these enzymes to act as cross-linking agents.

Immunologic basis for vaccination against dental caries in rhesus monkeys

The effects of immunization with Streptococcus mutans on the development of caries and the immune responses were investigated in 37 young rhesus monkeys (Macaca mulatta) during a period of up to 33 months. The monkeys were supplied a human type of carbohydrate-rich diet that contained about 15% sucrose. The monkeys were separated into seven groups, and the effects of two whole cell vaccines and an extracellular culture extract of S mutans in Freund's incomplete adjuvant were compared with a vaccine of a noncariogenic Streptococcus CHT, the adjuvant alone, and a sham immunized group. Sequential analysis of complement fixing, hemagglutinating and precipitating antibodies to the cell wall, and extracellular culture extract have shown that a significant reduction in smooth surface and fissure caries resulted from immunization with the S mutans vaccines, if antibodies reached an optimum level before caries development started. Protection was not elicited by the culture extract of S mutans or the noncariogenic Streptococcus CHT vaccines. A recently developed bacteriological sampling technique of crevicular fluid, plaque, and saliva showed that caries reduction in immunized animals was associated with a significantly decreased percentage of S mutans in crevicular fluid. Immunochemical studies showed IgG and IgM classes of antibodies in serum and secretory IgA antibodies in saliva, but it appears that reduction in caries was best associated with serum IgG antibodies to the culture extract of S mutans. The humoral and cellular mechanisms involved in the immunologic control of caries are discussed in terms of a central afferent mechanism required for antigen processing and cellular proliferation, and two peripheral effector mechanisms that function in the crevicular and salivary domains.

Effects of antibodies on adherence and cell-associated glucan production by Streptococcus mutans cells

Studies reported here show that hyperimmune rabbit serums can have profound inhibitory effects on adherence of S mutans to smooth surfaces and that this reduction in adherence is correlated with the reduction of CAG. The latter was measured by an assay developed in our laboratory that estimates CAG production by measuring the uptake of 14C glucose-labeled sucrose into components which can be extracted by dilute alkali. This is a direct demonstration of the effect of antibody on a metabolic function of S mutans that is important in virulence. The direct correlation bewteen inhibition of CAG production, and inhibition of adherence by an antibody, suggests that the inhibition of adherence is brought about by reduction of CAG synthesis. Further studies reported here show that the inhibition of adherence and of CAG synthesis is much more effective in homologous antiserums as compared to heterologous antiserums. These results point to the need for in vivo experiments to test the effects of vaccines on colonization by heterologous as well as homologous S mutans strains.

Diethylaminoethyl-cellulose-bacterial cell immunoadsorbent columns: preparation of serotype-specific globulin and immunofluorescent conjugates for Streptococcus mutans serotypes a and d

Diethylaminoethyl (DEAE)-cellulose was used as a support material for preparing bacterial cell columns. Pretreatment of the bacterial cells with formalin was essential in obtaining satisfactory adherence of the cells to DEAE-cellulose. Cross-reacting antibodies were removed from antibody preparations against strains of Streptococcus mutans serotypes a and d by adsorption on appropriate bacterial cell columns. S. mutans serotype d was further divided into two subtypes on the basis of immunofluorescent staining with conjugates of immunospecifically adsorbed immunoglobulin G. The DEAE-cellulose-bacterial cell columns were regenerated after use by desorbing the cross-reacting antibodies with low-pH buffer and were used repeatedly over and 18-month period with no detectable loss in effectiveness.

Some serological cross-reactions between Streptococcus mutans, S sanguis, and other dental plaque streptococci

From the preliminary observations described in this report, the following conclusions may be drawn. When attempting to produce diagnostic antiserums specific for S mutans, S mitior, or S sanguis, care must be taken to eliminate cross-reactions as a result of antibodies against extracellular glucans or dextrans. Other antigenic components, associated with the cell wall, may be common to different species. One soluble protein or polypeptide antigen normally present in S sanguis and S mitior may also be demonstrated in certain strains of S mutans. Antiserums prepared against S sanguis, S mitior, or S mutans should be carefully checked for interspecies cross-reactions before being used for identification purposes.

Purification, characterization, and immunogenicity of cell-associated glucan from Streptococcus mutans

Appropriate immunization with whole cell vaccines of S mutans appear to induce antibodies that inhibit implantation of S mutans on tooth surfaces and associated dental caries. To better understand the mechanisms by which vaccination prevents S mutans implantation and dental caries, and to prepare antigens whose effectiveness and safety can be tested in animal models of caries, we set out to purify and chemically characterize the CAG of S mutans. The CAG of S mutans strain 6715 was prepared by extracting cells with potasssium hydroxide at 100 C. After neutralization and extensive washing, the water-insoluble product was characterized by a battery of chemical analyses and found to be a relatively pure glucan. The CAG was weakly immunogenic in rabbits when administered in Freund's complete adjuvant. In monkeys (M irus) immunized via the parotid duct with an aqueous solution of CAG, a definite but weak serum IgG, IgM, IgA, and salivary IgA antibody response was observed. Absorption experiments showed that the CAG induced antibodies that cross reacted with Sephadex G-25 and others that reacted with unique determinants on CAG. Retention of native antigenic determinants through the purification procedures was verified by the observations that antiserums to CAG reacted with whole cells of S mutans and by the fact that antiserums to S mutans cells reacted with CAG.

Immunization of Macaca fascicularis (Macaca irus) monkeys with Streptococcus mutans: specificity of antibody responses in saliva

M fascicularis monkeys were immunized subcutaneously in the vicinity of the major salivary glands and by retrograde infusion into the parotid duct, with a vaccine containing Formalin-killed S mutans strain 6715 cells and culture-fluid antigens. Indirect immunofluorescent staining was used to titrate and classify antibodies. Subcutaneous immunization induced only a serum response, whereas intraductal infusion stimulated both an IgA antibody response in the parotid fluid and a serum response. Immunized and nonimmunized control groups were orally infected with S mutans strain 6715. The establishment in dental plaque was quantitated by recovery of the infecting organism on selective media and by immunofluorescent staining of plaque smears taken from individual tooth surfaces. The establishment of S mutans strain 6715 was noticeably inhibited in immune monkeys. Immunofluorescent assays for antibody also showed that serum and parotid fluid containing serum IgA antibodies cross reacted with other d serotype and a serotype strains but not representative b and c strains. Immune and control groups were then orally infected with S mutans strain GS-5, a c serotype strain, and no inhibition in establishment was detected of the non-cross-reacting type c organism in the immune group. A latter series of booster immunizations via the intraductal route resulted in a significant decrease in parotid fluid flow. Histological investigations showed inflammatory cell infiltration and replacement of epithelium by connective tissue in the glands from immunized monkeys. A separate group of monkeys, younger than the first, was immunized with the same vaccine via the duct only. In this group, immunizations were given at shorter intervals, but the immunization response was similar to that observed in the first group. The investigations reviewed here and new experiments reported show that immunization of monkeys with S mutan strain 6715 via the parotid duct elicited a reproducible IgA antibody response in the parotid fluid as well as a serum antibody response. Inhibition of colonization on tooth surfaces in immune monkeys showed specificity for the immunizing strain suggesting that inhibition was antibody mediated.

Streptococcus mutans serotypes: some aspects of their identification, distribution, antigenic shifts, and relationship to caries

For an immunologic point of view, several facts are worth consideration. S mutans can be separated into at least seven serotypes. Five of the types are based on antigens that may be specific for S mutans. One type, e, is related to the Lancefield group E streptocci, and one type, f, may lack an antigen that shows serological specificity. Analyses of plaque samples from individuals with a high caries activity have, in most instances, shown the presence of c, d, and possibly the g types. This does not necessarily mean that they are per se more cariogenic than the other types, but if all the serotypes cannot be combatted simultaneously, the c, d, and g types are an obvious first choice. S mutans strains do have antigens other than those used for serological identification, and it is not known which antigens can evoke antibodies with the highest protective capacity in humans. The phenomenon of antigenic shifts may make it possible for the bacteria to elude antibodies. However, the number of possible changes may be restricted. If certain antigens are of importance for the cariogenicity of S mutans, a change in their structure might result in a less cariogenic flora.

Synthesis and secretion of secretory immunoglobulins: with special reference to dental diseases

The distribution of immunoglobulin-containing cells in human tonsils, salivary glands, and inflamed gingiva is described. The cellular localization of J chain indicates that this peptide is a basic gene product of B cells that is expressed only in the early phase of clonal differentiation. Gland-associated immunocytes apparently are derived from this phase, which may be relevant to their local homing mechanism. The selective glandular transport of dimeric or polymeric IgA and 19S IgM may be determined by the content of J chain in these immunoglobulins. A J-chain-dependent configuration seems to be responsible for their noncovalent affinity for SC, and this may explain their specific reception at the epithelial cell membranes. Subsequent stabilization of the Ig-SC complexes takes place during their external transport, probably because of disulfide exchange. The latter process is more efficient for secretory IgA than for secretory IgM. The secretory dynamics of parotid IgA differs from that of other parotid proteins and is highly dependent on the degree of secretory stimulation. The secretion rate (mug/min/gland) seems to be a better measure of an individual's parotid IgA output than the absolute concentration of IgA in the secretion. A low parotid IgA secretion rate is associated with high susceptibility to dental caries, perhaps reflecting inferior resistance to dental plaque formation. It is not known whether such resistance, in part, is determined by specific antibodies to certain bacterial antigens. A potential candidate for an efficient preventive action of salivary antibodies could be the GTF enzyme system of S mutans. However, we were able to demonstrate only extremely rare immunocytes producing antibodies to GTF in human tonsils and gingiva, and none at all in salivary glands.

Adherence of serotype e Streptococcus mutans and the inhibitory effect of Lancefield group E and S mutans type e antiserum

S mutans strain MT703 from an active carious lesion in the tooth of a child had type e specificity and showed a cross-reaction with the Lancefield group E cell wall streptococcal polysaccharide antigen. Heat-killed cells MT703 adhered to a glass surface in the presence of CGT MT703 and sucrose. Pretreatment of the cells with anti-MT703 whole cell serums inhibited adherecne. The removal of glycerol teichoic acid antibody and group E antibody from the MT703 serum did not result in a loss of inhibitory activity. Antiserum with or without adsorption significantly inhibited glucan synthesis by CGT from sucrose. Antibodies specific for the polyglycerol phosphate of teichoic acid did not inhibit adherence. Anti-group E serum and serums specific for other types of S mutans, did not show adherence inhibitory activity except for an occasional type c specific antiserum. Antibody specific for the type e antigen produced significant inhibition of the binding of CGT to the MT703 cell wall, and adherence of these cells did not occur. Antibody to CGT inhibited glucan synthesis. Treatment of the cells with dextranase, dextran antibody, or trypsin caused a significant reduction in adherence. The results suggest that the type antigen and dextran on the surface of the S mutans type e cell are functional in adherence, and that these polymers are associated with cell wall protein.

Antigens in Streptococcus mutans cross reactive with human heart muscle

An antigen that cross reacts with mammalian heart tissue has been shown to be present in several strains of S mutans. Inoculation of S mutans into rabbits elicited heart-reactive antibody as part of the immunologic response. This heart-reactive antibody was demonstrated to be tissue-specific in that it only bound heart and smooth muscle tissue. Similar results have been previously reported using group A streptococci. Adsorption studies using sarcolemmal sheaths, group A streptoccal membranes, and fractions of cariogenic streptococci demonstrated the presence of a similar antigen. The aforementioned fractions could remove heart-reactive antibody from both immune rabbit serums and serums from patients with acute rheumatic fever. These findings dictate the necessity for testing any future caries vaccine containing fractions of S mutans for the presence of this cross-reactive antigen to avoid a possible autoimmunization.

Formation of cross-reacting antibodies against cellular and extracellular lipoteichoic acid of Streptococcus mutans BHT

Antisera prepared against strains of Streptococcus mutans, particularly strain BHT, contain antibodies to the membrane lipoteichoic acid component that will cross-react with lipoteichoic acids from three species of lactobacilli. A more detailed study of the antibodies to strain BHT confirmed that the antibodies are specific for the polyglycerol phosphate component common to the lipoteichoic acids. Sera with a higher hemagglutinating titer could be obtained by injecting disrupted organisms. The partially purified lipoteichoic acid isolated from the culture fluid of S. mutans BHT was also immunogenic antibodies; antibodies were also formed against another unidentified component in this extracellular fraction.