A1 beta-casein milk protein and other environmental pre-disposing factors for type 1 diabetes.

Globally type 1 diabetes incidence is increasing. It is widely accepted that the pathophysiology of type 1 diabetes is influenced by environmental factors in people with specific human leukocyte antigen haplotypes. We propose that a complex interplay between dietary triggers, permissive gut factors and potentially other influencing factors underpins disease progression. We present evidence that A1 ß-casein cows' milk protein is a primary causal trigger of type 1 diabetes in individuals with genetic risk factors. Permissive gut factors (for example, aberrant mucosal immunity), intervene by impacting the gut's environment and the mucosal barrier. Various influencing factors (for example, breastfeeding duration, exposure to other dietary triggers and vitamin D) modify the impact of triggers and permissive gut factors on disease. The power of the dominant trigger and permissive gut factors on disease is influenced by timing, magnitude and/or duration of exposure. Within this framework, removal of a dominant dietary trigger may profoundly affect type 1 diabetes incidence. We present epidemiological, animal-based, in vitro and theoretical evidence for A1 ß-casein and its ß-casomorphin-7 derivative as dominant causal triggers of type 1 diabetes. The effects of ordinary milk containing A1 and A2 ß-casein and milk containing only the A2 ß-casein warrant comparison in prospective trials.

Do all the patients with gastric parietal cell antibodies have pernicious anemia?

OBJECTIVE: This study evaluated whether all the patients with serum gastric parietal cell antibody (GPCA) positivity had pernicious anemia (PA). MATERIALS AND METHODS: The blood hemoglobin (Hb), iron, and vitamin B12 concentrations, and mean corpuscular volume (MCV) in 124 GPCA-positive patients were measured and compared with the corresponding data in 124 age- and sex-matched healthy controls. PA was defined by World Health Organization (WHO) as having an Hb concentration < 13 g dl(-1) for men and < 12 g dl(-1) for women, an MCV ≥ 100 fl, and a serum vitamin B12 level < 200 pg ml(-1) . RESULTS: We found that 20, 25, and 20 GPCA-positive patients had deficiencies of Hb (men < 13 g dl(-1) , women < 12 g dl(-1) ), iron (<60 µg dl(-1) ), and vitamin B12 (<200 pg ml(-1) ), respectively. Moreover, 16 GPCA-positive patients had abnormally high MCV (≥ 100 fl). GPCA-positive patients had a significantly higher frequency of Hb, iron, or vitamin B12 deficiency and of abnormally high MCV (all P-values < 0.001) than healthy controls. However, only 12.9% of 124 GPCA-positive patients were diagnosed as having PA by the WHO definition. CONCLUSION: Only 12.9% of GPCA-positive patients are discovered to have PA by the WHO definition.

Modulation of serum gastric parietal cell antibody level by levamisole and vitamin B12 in oral lichen planus.

OBJECTIVES: The objective of this study was to test the efficacy of three different treatment modalities on the reduction of serum anti-gastric parietal cell autoantibody (GPCA) level in GPCA-positive oral lichen planus (OLP) patients. MATERIALS AND METHODS: Of 147 GPCA-positive OLP patients, 100 were treated with levamisole plus vitamin B12, 10 with vitamin B12 only and 37 with levamisole only. The serum GPCA levels in 147 OLP patients were measured at baseline and after treatment. RESULTS: Treatment with levamisole plus vitamin B12 for a period of 2-50 months and treatment with vitamin B12 only for a period of 4-44 months could effectively reduce the high serum GPCA level to undetectable level in 100 and 10 OLP patients, respectively. However, treatment with levamisole only for a period of 2-50 months could not modulate the high mean serum GPCA titer to a significantly lower level in 37 OLP patients. A 92% GPCA recurrence rate was found in 25 OLP patients receiving no further vitamin B12 treatment during the GPCA-negative remission period. CONCLUSION: For GPCA-positive OLP patients, treatment modality containing vitamin B12 can effectively reduce the high serum GPCA level to undetectable level. OLP patients with underlying autoimmune atrophic gastritis trait should receive a maintenance vitamin B12 treatment for life.

Levamisole can reduce the high serum tumour necrosis factor-alpha level to a normal level in patients with erosive oral lichen planus.

In this study, we measured the baseline serum levels of tumour necrosis factor (TNF)-alpha in 158 patients with oral lichen planus (OLP) and in 54 normal control subjects. In total, 60 patients with erosive OLP (EOLP) with relatively high TNF-alpha levels were treated with levamisole and the serum TNF-alpha levels measured after treatment. We found that the mean +/- SD serum level of TNF-alpha in patients with either type of EOLP (12.0 +/- 1.7 pg/mL, P<0.005), major EOLP (15.5 +/- 4.4 pg/mL, P<0.001), minor EOLP (11.1 +/- 1.8 pg/mL, P<0.01), or nonerosive OLP (6.1 +/- 1.7 pg/mL, P<0.05) was significantly higher than that (3.8 +/- 0.2 pg/mL) of normal control subjects. Treatment with levamisole for a period of 0.5-7.5 months significantly reduced the mean serum TNF-alpha level from 22.6 +/- 3.4 pg/mL to 6.2 +/- 0.8 pg/mL (P<0.001) in 60 patients with EOLP. We conclude that levamisole can reduce high serum TNF-alpha levels to normal in patients with EOLP.

Serum interleukin-8 level is a more sensitive marker than serum interleukin-6 level in monitoring the disease activity of oral lichen planus.

BACKGROUND: Oral lichen planus (OLP) is a T-cell-mediated inflammatory disease. Interleukin (IL)-8 is a pro-inflammatory cytokine of host response to injury and inflammation. OBJECTIVES: To investigate whether serum IL-8 level was a more sensitive marker than serum IL-6 level in monitoring the disease activity of OLP and to assess whether IL-8 was a useful serum marker in evaluating the therapeutic effects of levamisole on OLP patients. METHODS: In this study, we used a solid phase, two-site sequential chemiluminescent immunometric assay to determine the baseline serum levels of IL-6 and IL-8 in 158 patients with OLP, nine patients with traumatic ulcers (TU) and 54 normal control subjects. Some OLP patients with the serum IL-6 or IL-8 levels higher than the upper limit of normal serum concentration were treated with levamisole for 0.5-6.0 months and their serum IL-6 and IL-8 levels were measured after treatment. RESULTS: We found that 28% (44 of 158) OLP, 28% (40 of 142) erosive OLP (EOLP), and 25% (four of 16) nonerosive OLP (NEOLP) patients had a serum IL-6 level greater than the upper normal limit of 4.7 pg mL(-1). In contrast, 63% (99 of 158) OLP, 63% (90 of 142) EOLP and 56% (nine of 16) NEOLP patients had a serum IL-8 level greater than the upper normal limit of 8.7 pg mL(-1). In some OLP patients with the serum IL-6 or IL-8 levels higher than the upper limit of normal serum concentration, treatment with levamisole for a period of 0.5-6.0 months could significantly reduce the mean serum IL-6 level from 14.3 +/- 1.9 pg mL(-1) to 3.2 +/- 0.6 pg mL(-1) (P < 0.001) and could significantly reduce the mean serum IL-8 level from 95.8 +/- 17.1 pg mL(-1) to 14.8 +/- 5.8 pg mL(-1) (P < 0.001). CONCLUSIONS: Because measurement of the serum IL-8 level can detect more OLP patients with an abnormal serum level than measurement of the serum IL-6 level (63% vs. 28%), we conclude that serum IL-8 level is a more sensitive marker than serum IL-6 level in monitoring the disease activity of OLP. Levamisole can modulate both the serum IL-6 and IL-8 levels in OLP patients. IL-8, like IL-6, is also a useful serum marker in evaluating the therapeutic effects of levamisole on OLP patients.

A 60-kilodalton immunodominant glycoprotein is essential for cell wall integrity and the maintenance of cell shape in Streptococcus mutans.

We have demonstrated previously by Western blotting that in naturally sensitized humans, the serum or salivary antibody response to Streptococcus mutans was directed predominantly to a protein antigen with a size of approximately 60-kDa. To identify this immunodominant antigen, specific serum antibodies were eluted from immunoblots and five positive clones with inserts ranging in length from 3 to 8 kb from identical chromosomal loci were obtained by screening a genomic expression library of Streptococcus mutans GS-5. Amino acid sequencing established the identity of this immunodominant antigen, a 60-kDa immunodominant glycoprotein (IDG-60), to be a cell wall-associated general stress protein GSP-781, which was originally predicted to have a molecular mass of approximately 45 kDa based on the derived nucleotide sequence. Discrepancy in the molecular mass was also observed in recombinant his-tagged IDG-60 (rIDG-60) expressed from Escherichia coli. Glycosylation, consisting of sialic acid, mannose galactose, and N-acetylgalactosamine, was detected by lectin binding to IDG-60 in cell wall extracts from S. mutans and rIDG-60 expressed in vivo or translated in vitro. Despite the presence of multiple Asn or Ser or Thr glycosylation sites, IDG-60 was resistant to the effect of N-glycosidase F and multiple O-glycosidase molecules but not to beta-galactosidase. Insertional inactivation of the gene encoding IDG-60, sagA, resulted in a retarded growth rate, destabilization of the cell wall, and pleiomorphic cell shape with multifold ingrowth of cell wall. In addition, distinct from the parental GS-5 strain, the isogenic mutant GS-51 was unable to survive the challenge of low pH and high osmotic pressure or high temperature. Expression of the wild-type gene in trans within GS-51 from plasmid pDL277 complemented the growth defect and restored normal cell shape. These results suggested that IDG-60 is essential for maintaining the integrity of the cell wall and the uniformity of cell shape, both of which are indispensable for bacteria survival under stress conditions.

Human T-cell responses to the glucosyltransferases of Streptococcus mutans.

We previously reported differential humoral responses to glucosyltransferases (GTFs), with significantly higher saliva and serum antibody levels to GtfD than to GtfB or GtfC. To test the hypothesis that cellular immune responses to these molecules also may differ, peripheral blood mononuclear cell (PBMC) and T-cell proliferative responses in young adults and children with distinct genetic backgrounds were determined using purified recombinant GtfC and GtfD. PBMCs from all of the volunteers responded to GtfC and -D, but responses were directed predominantly towards GtfD and were major histocompatibility class II antigen dependent. A predominant T-cell response to GtfD, over GtfC, was detectable at various antigen concentrations ranging from 1 to 20 microg/ml and correlated with the differential serum immunoglobulin G (IgG) and salivary IgA antibody responses to the GTFs. Therefore, in naturally sensitized humans, Streptococcus mutans GTFs stimulate differential humoral and cellular immune responses, with the secreted form of GtfD eliciting a stronger response than the cell wall-associated form of GtfC.

Identification of stress-responsive genes in Streptococcus mutans by differential display reverse transcription-PCR.

Streptococcus mutans, which causes dental caries in the human oral cavity and occasionally causes infective endocarditis in the heart, withstands adverse environmental stress through diverse alterations in protein synthesis. Differential gene expression in response to environmental stress was analyzed by RNA fingerprinting using arbitrarily primed PCR with a panel of 11mer primers designed for differential display in Enterobacteriaceae. Dot and Northern blot hybridization confirmed that the transcription of several genes was up- or down-regulated following exposure to acid shock from pH 7.5 to 5.5. RNA of a gene designated AP-185 (acid-stress protein) was induced specifically by acid treatment, while RNA of GSP-781 (general-stress protein) was up-regulated significantly when bacteria were exposed to high osmolarity and temperature, as well as low pH. The deduced amino acid sequence of AP-185 shares homology (78% identity) with branched-chain amino acid aminotransferase. Cloning and sequence analysis of GSP-781 revealed a potential secreted protein of a molecular mass of about 43 kDa and with a pI predicted to be 5.5. Transcriptional levels of another gene, designated AR-186 (acid-repressed protein), which encodes putative aconitase, were repressed by acid treatment but were enhanced by plasma or serum components. Analogous results were identified in icd and citZ genes, and repression of these genes, along with AR-186, was also observed when they were exposed to high osmolarity and temperature. These results indicate that differential regulation of specific genes at the transcriptional level is triggered by different stress and that genes responsible for glutamate biosynthesis in the citrate pathway are coordinately regulated during the stress response of S. mutans.

Three-dimensional modelling of the catalytic domain of Streptococcus mutans glucosyltransferase GtfB.

Glucosyltransferases (GtfB/C/D) of Streptococcus mutans, a pathogen for human dental caries, synthesize water-insoluble glucan through the hydrolysis of sucrose. Genetic and biochemical approaches have identified several active sites of these enzymes, but no three-dimensional (3D) structural evidence is yet available to elucidate the subdomain arrangement and molecular mechanism of catalysis. Based on a combined sequence and secondary structure alignment against known crystal structures of segments from closely related proteins, we propose here the 3D model of an N-terminal domain essential for the sucrose binding and splitting in GtfB. A Tim-barrel of (alpha/beta)(8) structural characteristics is revealed and the structural correlation for two peptides is described.

Identification of a fibronectin binding protein from Streptococcus mutans.

The interaction of viridans streptococci with components of the extracellular matrix (ECM) plays an important role in the pathogenesis of infective endocarditis. We have identified a surface protein of Streptococcus mutans which binds the ECM constituent fibronectin (Fn). Initially, we found that S. mutans could adsorb soluble Fn in plasma, but with lower efficiency than Streptococcus pyogenes. In addition, S. mutans could bind immobilized Fn in a dose-dependent manner when tested using an enzyme-linked immunosorbent assay. Crude extracts of cell wall-associated proteins or extracellular proteins from S. mutans MT8148 specifically bound Fn through a protein with the molecular mass of ca. 130 kDa, as detected by far-Western immunoblotting. The candidate Fn binding protein (FBP-130) was purified to near homogeneity by using Fn coupled Sepharose 4B affinity column chromatography. A rabbit polyclonal antibody against FBP-130 reacted specifically with a protein of molecular mass of ca. 130 kDa in both cell wall and extracellular fractions, and the abundance of FBP was higher in the former than in the latter fractions. The purified FBP bound specifically to immobilized Fn, whereas the binding of soluble Fn to coated FBP could only be detected in the presence of high concentrations of Fn. The purified FBP, as well as anti-FBP immunoglobulin G, inhibited the adherence of S. mutans to immobilized Fn and endothelial cells (ECV304) in a dose-dependent manner. These results demonstrated that FBP-130 mediated the adherence of S. mutans specifically to Fn and endothelial cells in vitro. The characteristics of S. mutans and FBP-130 in binding Fn confirmed that viridans streptococci adopt different strategies in their interaction with ECM.

Salivary and serum antibody response to Streptococcus mutans antigens in humans.

Humoral immunity against Streptococcus mutans infection was analyzed in caries-active and caries-free young adults by immunoblotting. All volunteers from both groups had detectable salivary immunoglobulin A (IgA) and serum IgG antibodies, with similar profiles. They could be classified on the basis of relative intensity of the immunoblot bands into categories of high or low responders. Common protein antigens with molecular weight ranging from approximately 45 to 190 kDa could be found either extracellularly or associated with the cell wall of S. mutans cultured in vitro. The predominant reactive antigens recognized by both IgA and IgG were of proteins around 63 and 60 kDa. Detection of IgA antibodies to the various antigens of S. mutans in individual saliva samples did not always correlate with serum IgG antibody profiles. In addition, distinct bands, which reacted preferentially with either IgA or IgG, could be detected by antibodies from specific subjects. Differential reactivities of salivary IgA and serum IgG antibodies to two, cell-wall associated protein antigens around 33 and 36 kDa were found in caries-active and caries-free young adults; 30.8% of caries-free subjects and 12% of caries-active subjects (P < 0.01) exhibited detectable antibody response to these antigens. This difference was not attributable to variations in antibody levels, since antibody response to these proteins were still detectable in some caries-free but not caries-active individuals whose levels of antibodies to other antigens were low. Thus, a new antibody profile which correlates with dental caries disease activity has been identified in a selected population. Differences in mucosal and systemic immune responses to S. mutans seem to be both antigen and host dependent.

Functional analyses of a conserved region in glucosyltransferases of Streptococcus mutans.

Streptococcus mutans glucosyltransferases (GTFs; GtfB, -C, and -D) synthesize water-soluble and -insoluble glucan polymers from sucrose. We have identified previously a conserved region of 19 amino acids (aa) (Gtf-P1; aa 409 to 427 of GtfB and aa 435 to 453 of GtfC) which is functionally important for both enzymatic activity and bacterial adherence. Monoclonal antibodies directed against Gtf-P1 selectively inhibited insoluble glucan synthesis by GtfB and -C but had no effect on soluble glucan synthesis by GtfD, suggesting that despite an apparent near identity of sequence, corresponding residues may function differently in these enzymes. To test this hypothesis, we used different strategies of mutagenesis to analyze amino acid residues of GtfB and GtfC in Gtf-P1. In-frame insertion of 6 amino acids preceding, or deletion of 14 amino acids within, this conserved region abolished the enzymatic activities of both GtfB and GtfC. Substitution of several residues in combination by random mutagenesis resulted in GtfB, but not GtfC, enzymes exhibiting decreased glucan synthesis and reduced rates of sucrose hydrolysis. Amino acid substitutions of Asp residues in GtfB or GtfC were found to be more critical for enzymatic activity than at other positions of this region. Interestingly, single mutation at Asp411 or Asp413 of GtfB resulted in enzymes retaining about 20% of wild-type activity, whereas mutagenesis of the corresponding Asp at position 437 or 439 in GtfC resulted in complete loss of enzymatic activity. Furthermore, single amino acid substitution of a Val residue between the two Asp residues enhanced the sucrase- and glucan-synthesizing activities of GtfB and GtfC. These results confirmed the report from another laboratory that Asp residues in the Gtf-P1 region are essential for enzymatic catalysis and provide new evidence that identical residues may function differently in closely related Gtf enzymes.

Antigenicity of a synthetic peptide from glucosyltransferases of Streptococcus mutans in humans.

Human salivary immunoglobulin A (IgA) and serum IgG antibodies to the Streptococcus mutans glucosyltransferases (Gtfs) and to a synthetic peptide of 19 amino acids from a conserved region in the Gtfs (residues 435 to 453) were determined in young adults by enzyme-linked immunosorbent assay. Varying levels of antibody to Gtfs were detected in saliva or serum, with significantly higher levels of antibody to GtfD than to GtfB/C or GtfC. Anti-Gtf IgA levels in saliva did not correlate with those of IgG in serum. Caries-free (CF) volunteers exhibited significantly higher salivary IgA antibody levels to the peptide and to GtfB/C or GtfC than did the caries-active (CA) subjects. Preincubation of CF saliva and serum with the peptide inhibited the antibodies to the Gtfs in a dose-dependent manner, whereas preincubation of the samples from the CA group resulted in only partial inhibition. Our results indicated that this 19-amino-acid peptide includes one of the major B-cell epitopes of Gtfs and that CF individuals have higher titers of antibodies than CA subjects.

Inhibition of Hepatitis Delta Virus Genomic Ribozyme Self-Cleavage by Aminoglycosides.

Subgenomic regions of hepatitis delta virus (HDV) RNA contains ribozyme whose activities are important to viral life cycles and depend on a unique pseudoknot structure. To explore the characters of HDV ribozyme, antibiotics of the aminoglycoside, which has been shown inhibiting self-splicing of group I intron and useful in elucidating its structure, were tested for their effect on HDV genomic ribozyme. Aminoglycosides, including tobramycin, netromycin, neomycin and gentamicin effectively inhibited HDV genomic ribozyme self-cleavage in vitro at a concentration comparable to that inhibiting group I intron self-splicing. The extent of inhibition depended upon the concentration of magnesium ion. Chemical modification mapping of HDV ribozyme RNA indicated that the susceptibility of nucleotide 703 to the modifying agent was enhanced in the presence of tobramycin, suggesting a conformational shift of HDV ribozyme, probably due to an interaction with the aminoglycoside. Finally, we examined the effect of aminoglycoside on HDV cleavage and replication in cell lines, however, none of the aminoglycoside effective in vitro exerted suppressive effects in vivo. Our results represented as an initial effort in utilizing aminoglycoside to probe the structure of HDV ribozyme and to compare its reaction mechanism with those of other related ribozymes.

Purification and characterization of Streptococcus mutans glucosyltransferase (GtfC) expressed in Escherichia coli.

Streptococcus mutans constitutively expresses three glucosyltransferases, i.e., GtfB, GtfC, and GtfD; which synthesize glucan polymers from sucrose. To obtain individual GTF without complexing with one another, a purification strategy was developed to recover recombinant GTF expressed from Escherichia coli. The recombinant GtfC was aggregated and associated with the insoluble fraction in E. coli homogenates. GtfC was solublized with the 8M urea, renatured to its biologically active form by serial dialysis against sodium phosphate buffer, and subsequently purified to homogeneity by DEAE-Sephacel and hydroxylapatite column chromatography. The GtfC enzyme preparation was purified 16.3-fold and the molecular weight was estimated to be 140 kDa. GtfC synthesized water insoluble glucan in a primer independent manner and its enzymatic activities could be enhanced by dextran. Purified GtfC had a pH optimum of 6.5, a K(m) of 9.26 mM for sucrose and a pI of 5.5. Distinct from the previous reports, results from this study offers an alternative for the purification of the recombinant GTFs free from any detergent contamination to make it more suitable for utilization in vivo.

Purification of glucosyltransferases (GtfB/C and GtfD) from mutant strains of Streptococcus mutans.

Streptococcus mutants constitutively expresses three glucosyltransferases (GTFs), i.e., GtfB, GtfC, and GtfD, which synthesize glucan polymers from sucrose. Two genetically constructed mutants of S. mutans which stably expressed either the cell-associated or the extracellular GTFs were selected for purification and characterization of these enzymes. The cell-associated GtfB and GtfC from strain GS-5DD lacking the gtfD gene expression were extracted by urea, renatured by dialysis in sodium phosphate buffer and then separated from the other wall-associated components by column chromatography. The extracellular GtfD was purified from the culture supernatant of strain NHS1 lacking gtfB and gtfC gene expression. The molecular weights of the purified GTFs was similar (150-160 kDa), as determined by SDS-polyacrylamide gel electrophoresis. The GtfB/C preparation synthesized primarily water-insoluble glucan in a primer independent manner. However, the presence of the dextran enhanced the enzymatic activities of the GtfB/C. GtfD synthesized water-soluble glucan exclusively in a primer dependent manner. Purified GtfD had a pH optimum of 5.5, and a K(m) value of 4.35 mM for sucrose. These results indicated that the mutated strains served as an efficient and specific host to obtain native GTFs.

Inhibition of glucosyltransferase activities of Streptococcus mutans by a monoclonal antibody to a subsequence peptide.

Preliminary analysis indicated that a 19-amino-acid peptide sequence (435 to 453 of GtfC) within a highly conserved region of the glucosyltransferases of the cariogenic streptococci might be functionally important (J.-S. Chia, S.-W. Lin, T.-Y. Hsu, J.-Y. Chen, H.-W. Kwan, and C.-S. Yang, Infect. Immun. 61:1563-1566, 1993). To obtain antipeptide monoclonal antibodies (MAbs), the 19-amino-acid peptide was conjugated to bovine serum albumin and used as an antigen in BALB/c mice. Six immunoglobulin G-secreting hybridoma clones, CJSm18-S1 to -S6, specifically reacted with this peptide and with purified GtfC and GtfD but not with bovine serum albumin in an enzyme-linked immunosorbent assay. The concentrated hybridoma supernatant of all six MAbs inhibited GtfC enzymatic activity but failed to inhibit GtfD, although GtfD contains the same peptide sequence. Further analysis of a purified immunoglobulin G2b MAb from one of the clones, CJSm18-S3, confirmed that this MAb specifically inhibited GtfC enzymatic activity for insoluble-glucan synthesis in a dose-dependent manner. CJSm18-S3, even at high concentrations, had no effect on GtfD, which synthesizes water-soluble glucan exclusively. Furthermore, the in vitro sucrose-dependent adherence of Streptococcus mutans was also inhibited by CJSm18-S3 in a dose-dependent manner. Our results indicate that the peptide containing the N-terminal conserved region of glucosyltransferases is functionally important for both enzymatic activity and bacterial adherence.

Analysis of a DNA polymorphic region in the gtfB and gtfC genes of Streptococcus mutans.

We have previously demonstrated the existence of DNA polymorphisms at the 5' coding regions of the gtfB and gtfC genes specifying the streptococcal glucosyltransferases (J.S. Chia, T.Y. Hsu, L.J. Teng, J.Y. Chen, L.J. Hahn, and C.S. Yang, Infect. Immun. 59:1656-1660, 1991). DNA sequence analysis by polymerase chain reaction and direct sequencing revealed that while several nucleotide changes were identified, accounting for the polymorphisms, the amino acids which they code for remain unchanged. The polymorphic region is located in a highly conserved amino terminus of the glucosyltransferases. A peptide of 19 amino acids from this region reversed the inhibiting activity of an antiserum raised against the proteins coded for by the gtfB and gtfC genes. The results suggest that the polymorphic region, varying in DNA but not in amino acid sequences, might specify some biological function.

Glucosyltransferase gene polymorphism among Streptococcus mutans strains.

Genetic polymorphisms in genes coding for the glucosyltransferases were detected among Streptococcus mutans serotype c strains by Southern blot analysis with DNA probes located within the gtfB gene (H. Aoki, T. Shiroza, M. Hayakawa, S. Sato, and H. K. Kuramitsu, Infect. Immun. 53:587-594, 1986). Restriction endonucleases were used to examine genomic DNAs isolated from serotype a to h strains. The variations were readily detected among 33 strains of serotype c by EcoRI and PstI restriction enzyme digestions. Serotypes e and f, which are genetically similar to serotype c, also had comparable polymorphism; however, serotypes a, b, d, g, and h did not hybridize to the same DNA probes in parallel experiments. Further analysis of enzymatic activities for glucan synthesis and sucrose-dependent adherence revealed no significant differences among the serotype c strains. Our results suggested that genetic polymorphisms existing in S. mutans serotype c strains may reflect a complexity in genes coding for the glucosyltransferases, which are produced ubiquitously in members of the S. mutans group.

Association between dental caries prevalence and Streptococcus mutans among 13-year-old children.

The prevalence of caries associated prevalence with Streptococcus mutans in saliva and pooled plaque was investigated among 13-year-old Chinese children. In conjunction with saliva sampling simplified greatly by adopting the oral rinse method, an initial threshold value of 10(4) colony forming units (cfu) per ml of rinse was established on the basis of the S. mutans counts from 27 caries-free individuals. The results of the present study showed that, of the total 58 children, 67.3% had S. mutans counts above the threshold value in their saliva, and they developed significantly more decayed surfaces (D) and decayed, missing, filled surfaces (DMFS) than did the children below this value. The association between caries activity and S. mutans counts either in saliva or in pooled plaque samples was even stronger when only decayed surfaces were taken into account. In addition, the detection frequency of S. mutans (81.8%) was higher in saliva than in the pooled plaque samples (43.2%). This may demonstrate that saliva is more sensitive than dental plaque in predicting caries activity. The most prevalent biotypes of the S. mutans strains observed in this study were c and d. The results of this study indicate a significant association of S. mutans levels with caries prevalence. In the estimation of salivary S. mutans levels, the rinse method offered an easy and rapid identification for children with high caries risk and proved to be very practicable for epidemiological study on a larger scale.