Long-term xylitol consumption leads to the emergence of xylitol-resistant (X-R) mutans streptococci. The aim of the present study was to compare cariogenic traits in X-R and xylitol-sensitive (X-S) strains. Six strains of mutans streptococci, three X-R and three X-S strains, were studied. Xylitol resistance and sensitivity were confirmed by growth in xylitol-supplemented media. Acid production from glucose or fructose or uptake of xylitol was initiated by adding (14)C-labelled glucose, fructose or xylitol to bacterial suspensions. The resultant metabolites were identified by HPLC. Lactate was the major metabolite from glucose, whether the bacteria were grown in the presence or the absence of xylitol. Lactate production per colony-forming unit was lower in X-S cells than in X-R cells. Fructose was metabolized by both X-R and X-S cells. Both X-R and X-S cells took up xylitol, but xylitol-5-P was detected in X-S cells only. Total polysaccharides were measured through production of C(14)-labelled ethanol-insoluble polymers from [U(14)-C]-sucrose. No difference in polysaccharide production was found between X-R and X-S cells. The present study thus does not support the contention that X-R are less cariogenic than X-S mutans streptococci.

Children with untreated coeliac disease (CD) may develop enamel defects. Moreover, children with untreated CD have increased serum levels of gliadin reactive IgG, which may cross-react to amelogenin. The aim of this study was to investigate reactivity of anti-gliadin IgA and IgG to amelogenin in children with untreated CD. Blood samples from patients with CD (n = 75) and from disease controls (n = 24) were analysed for IgA and IgG reactivities to amelogenin (Emdogain) and to gliadin by ELISA. Whereas children with CD had statistically significantly higher serum levels of anti-amelogenin IgA, only those with the most severe CD (Marsh 3c) had significantly higher anti-amelogenin IgG immune reactivity than the disease controls. Western blotting confirmed that the IgA and IgG immune reactivity was to the amelogenin-specific bands in Emdogain and to a 22-kDa human recombinant amelogenin. Cross-inhibition studies revealed that the anti-amelogenin immune reactivity was not only caused by anti-gliadin cross-reactivity but also included amelogenin selective immune reactivity. Some controls had high levels of anti-amelogenin IgA and IgG, similar to children with CD. Thus, anti-amelogenin IgA and IgG may not only be involved in the aetiology of CD-associated enamel defects but may also interfere with enamel maturation in non-coeliac children.

Previously we detected increased levels of IgA to the enamel matrix protein amelogenin in children with untreated coeliac disease (CeD). The biological impact of autoantibodies to amelogenin may depend on which part of the amelogenin (epitopes) they bind. Sera or blood samples from 146 untreated children with CeD from two different cohorts and 25 non‐CeD control children were tested for IgA anti‐amelogenin (Emdogain) reactivity. The 32 CeD children and six controls with the highest reactivity were selected for detailed IgA anti‐amelogenin (AMELX) epitope mapping using 31 overlapping, 10–22mer peptides in ELISA. The dominating reactivity were to six peptides in a 75‐amino‐acid (aa)‐long central segment (aa 75–150) containing enzymatic cleavage sites for matrix metalloproteinase 20 (MMP‐20) and kallikrein‐related peptidase 4 (KLK‐4) and to two N‐terminal peptides (aa 13–41) included in the tyrosine‐rich amelogenin peptide fragment, which is important for self‐assembly. Only two of the six control children reacted to single, but different peptides. Solid‐phase extraction with gliadin‐ and Emdogain‐coated Sepharose revealed a gliadin cross‐reactive central region and a putative conformation‐dependent, apparently non‐cross‐reactive N‐terminal region. High IgA anti‐amelogenin reactivity may interfere with normal amelogenesis by inhibiting amelogenin self‐assembly, amelogenin‐hydroxyapatite interaction, and/or enzymatic degradation.

Children with untreated celiac disease (CeD) may develop enamel defects, and children with severe CeD have significantly increased levels of IgG to amelogenin, which may interfere with normal amelogenesis depending on which epitope(s) they bind. Children with untreated CeD (n = 42), for whom CeD had been confirmed either by biopsy (n = 17, cohort 1) or by the presence of particularly high serum levels of anti‐transglutaminase 2 (TG2) IgA (n = 25, cohort 2), were selected from 146 children with CeD, and 10 controls were selected from 34 children who did not have CeD. Samples from these 52 children were used for detailed IgG anti‐amelogenin, X isoform (AMELX) epitope mapping using 31 overlapping, 10‐22mer peptides in ELISA. Although sera from both groups showed reactivity to peptides containing sequences from the N and C terminus of AMELX, sera from children with CeD reacted more strongly to peptides from the central region (amino acids 75‐150) containing both a binding site for transforming growth factor‐β (TGF‐β), as well as the enzymatic cleavage sites for matrix metalloproteinase‐20 and for kallikrein‐4. Antigen‐specific extraction revealed that only IgG to the central region cross‐reacted to gliadin. Thus, cross‐reactive anti‐gliadin/amelogenin IgG may affect normal amelogenesis by interfering with enzymatic degradation, proper folding, and/or TGF‐β signaling in children with untreated CeD.