Prediction of Epitopic Region of Protein Antigenic Determinants From Streptococcus mutans

Objectives: To better understand the antigenicity and to screen the promising epitopic regions of antigen PAc and glucosyltransferase (GTF) for potential vaccine targets based on these two major virulent factors related to S. mutans adherence.

Methods: 94 children aged 3-4 years were randomly selected, including 53 no careis group (dmft=0) and 41 caries-positive children. The values of S.mutans, the salivary total secretory immunoglobulins (S-IgA), anti-PAc and anti-GLU were evaluated to make comparison to figure out the correlation between them. Because of the fact that the level of S-IgA against specific antigens did not increase as the S. mutans infection becomes severe, the complete amino acid sequence of PAc and GtfB was analyzed using the DNAStar Protean system for developing specific anti-caries vaccines related to S.mutans adherence. The prediction of the antigenic regions of the sequences is made by analyzing the indexes including hydrophilicity, high accessibility, and flexible and strong antigenicity.

Results: A significantly positive correlation between the amount of S.mutans and children DMFT index. No significant difference was detected in specific sIgA against PAc or GLU between any two groups and there was no significant correlation found between such specific S-IgA and caries index. 16 peptides (127-158, 352-370, 381-397, 436-486, 490-510, 535-550, 602-644, 673-686, 746-770, 802-816, 830-990, 1139-1173, 1184-1223, 1295-1325, 1374-1408, 1481-1515) from PAc as well as 13 peptides from GtfB with good hydrophilicity, high accessibility, flexible and strong antigenicity were chosen for further investigation.
Conclusions: S.mutans colonization contributed to the early children caries as an important etiologic factor. The level of S-IgA against specific antigens did not increase as the S.mutans infections become severe in children. Therefore, the epitopes of PAc and GTF have been screened for further investigation in the development of the anti-caries vaccines.