Mutans streptococci are well established as caries-inducing microorganisms in man. Most humans carry the bacteria, but in highly different numbers. This cannot be explained by environmental factors only. The aim of this study was to investigate a possible association between levels of colonization by mutans streptococci and the presence of certain B and DR human leukocyte antigens (HLA). Altogether, 170 subjects who had their HLA antigens determined (76 renal transplant patients and 94 healthy blood donors) were selected for the investigation. Paraffin-stimulated saliva samples were taken using the wooden spatula method with subsequent cultivation of mutans streptococci on mitis salivarius bacitracin agar plates. An association between the absence of HLA-DR 4 antigens and low, or undetectable, levels of mutans streptococci was found. This was statistically significant for the immunosuppressed renal transplant subjects. The same trend was observed among the healthy blood donors.

Our aim was to corroborate previous findings that HLA-DR4 carriers are characterized by higher levels of mutans streptococci in saliva than are individuals expressing other HLA-DR types. Of 68 subjects (dental students, staff, and faculty) who were sampled for salivary counts of mutants streptococci, 13 subjects with the lowest counts of mutans streptococci and 15 subjects with the highest counts were selected for HLA-typing. Of the 13 who expressed HLA-DR4, 8 were heavily colonized by mutants streptococci. Although a trend towards a relationship was found between HLA-DR4 carriage and high levels of mutans streptococci, it was not statistically significant. In this selected population, knowledge of how to minimize the risk of caries and mutans streptococci level may have influenced the results.

The aim of this study was to describe and compare salivary immunoglobulin A (IgA) antibody reactions to extracts of strains of three oral streptococci in human leukocyte antigen (HLA)-DR4-positive and -DR4-negative subjects. Whole paraffin-stimulated saliva samples were collected from 27 apparently healthy subjects. Previous HLA typing showed that 20 subjects were DR4 positive and 7 were DR4 negative. HLA-DRB1*04 subtyping was performed among the DR4-positive subjects. Whole-cell antigen extracts from Streptococcus mutans (KPSK 2), Streptococcus sobrinus (OMZ 65) and Streptococcus parasanguis (Nt 62) were separated in SDS-PAGE. The antigens were immunoblotted with diluted saliva (Western blot), scanned and analyzed in a computer system. All immunoblot bands were recorded in DR4-positive and DR4-negative saliva pools, and bands with an optical density >or=0.1 were selected for analysis in individual salivas. The DR4-negative subjects in general had more immunoblot bands and more distinct bands than did the DR4-positive subjects. A higher concentration of total IgA in saliva was correlated with more bands, especially to antigens separated from S. mutans. When the number of bands was calculated per IgA unit, significant differences were observed between DR4-positive and DR4-negative salivas. This was particularly seen for S. mutans and S. parasanguis. As the number of bands was analyzed in relation to DR4 subgroups, DRB1*04, there was a lower salivary IgA activity to S. mutans in the DRB1*0401 and *0404. The variable level of correlation previously demonstrated for S. mutans colonisation and serologically defined DR4 positive subjects might be explained by the heterogeneity in this group, and the relation should be sought on a subgroup level.

BACKGROUND/AIMS: Mutans streptococci are found in almost all individuals, though there are large differences in colonization levels between individuals. These differences are not readily explained, though several factors are believed to influence the colonization. One factor is the immune response to mutans streptococci, mainly provided by salivary immunoglobulin A (IgA). In a previous study, differences in salivary IgA reactions to oral streptococci were observed between human leukocyte antigen (HLA)-DR4-positive and DR4-negative indi-viduals. A lower salivary IgA activity to Streptococcus mutans in par-ticular was most pronounced for two DR4 subgroups, DRB1*0401 and *0404. The main purpose of this study was to further investigate, in a larger study group, the salivary IgA activity to antigens of three oral streptococci in relation to different HLA-DRB1*04 alleles. METHODS: Stimulated saliva was collected from 58 HLA-DRB1*04-positive individuals. Whole cell antigen extracts from S. mutans, Strep-tococcus sobrinus and Streptococcus parasanguis and the streptococ-cal antigen (SA) I/II were separated in SDS-PAGE, transblotted and detected with diluted saliva (Western blot), and analyzed in a com-puter program. All distinct immunoblot bands over 100 kDa were re-corded and compared in relation to DRB1*04. RESULTS: The im-munoblots revealed lower salivary IgA reactions to S. mutans, S. so-brinus and SA I/II, but not to S. parasanguis, for the DRB1*0401- and *0404-positive individuals compared to other DRB1*04 types. For the *0401 subgroup there was a significant association with a lower IgA response to S. mutans. CONCLUSION: The results confirm earlier ob-servations and may also support previous demonstrated association between colonization by mutans streptococci and the serologically de-fined HLA-DR4.

BACKGROUND: In the immunoblot technique, using whole bacteria cell extracts as antigens, both intra- and extracellular antigens are de-tected, which gives a large number of immunoglobulin A (IgA) reac-tions (immunoblot bands) when incubated with saliva. It is important to distinguish which immunoblot bands represent bacterial cell-surface antigens, since these antigens could be involved in adhesion mecha-nisms and be available for blocking in vivo. METHODS: Bacterial ex-tracts of Streptococcus mutans, Streptococcus sobrinus, Streptococcus parasanguis and the streptococcal antigen I/II were separated using SDS-PAGE. The antigens were detected with saliva in Western blot. Untreated saliva and saliva in which cell-surface reactive IgA had been absorbed with whole bacteria cells were analyzed. RESULTS: Ap-proximately half the number of the bands were absent for saliva ab-sorbed with homologous cells, compared to untreated saliva. The ab-sorption pattern was almost identical for S. mutans and S. sobrinus but not for S. parasanguis. Salivary IgA reactive against streptococcal antigen I/II was absorbed by S. mutans cells, to a lesser extent by S. sobrinus cells, and not at all by S. parasanguis cells. CONCLUSION: It is likely that the bands that were absent after absorption represented cell-surface antigens. For S. mutans and S. sobrinus, these bands were probably the streptococcal antigen I/II. Copyright Blackwell Munks-gaard, 2004.