Differential profiles of salivary proteins with affinity to Streptococcus mutans lipoteichoic acid in caries‐free and caries‐positive human subjects

Summary Streptococcus mutans is a representative oral pathogen that causes dental caries and pulpal inflammation. Its lipoteichoic acid (Sm. LTA ) is known to be an important cell‐wall virulence factor involved in bacterial adhesion and induction of inflammation. Since Sm. LTA ‐binding proteins (Sm. LTA ‐ BP s) might play an important role in pathogenesis and host immunity, we identified the Sm. LTA ‐ BP s in the saliva of caries‐free and caries‐positive human subjects using Sm. LTA ‐conjugated beads and LTQ ‐Orbitrap hybrid Fourier transform mass spectrometry. Sm. LTA was conjugated to N ‐hydroxysuccinimidyl‐Sepharose ® 4 Fast Flow beads (Sm. LTA ‐beads). Sm. LTA retained its biological properties during conjugation, as determined by the expression of nitric oxide and interferon‐γ‐inducible protein 10 in a murine macrophage cell line and activation of Toll‐like receptor 2 ( TLR 2) in CHO / CD 14/ TLR 2 cells. Sm. LTA ‐ BP s were isolated from pooled saliva prepared from 10 caries‐free or caries‐positive human subjects each, electrophoresed to see their differential expression in each group, and further identified by high‐resolution mass spectrometry. A total of 8 and 12 Sm.LTA ‐ BP s were identified with statistical significance in the pooled saliva from the caries‐free and caries‐positive human subjects, respectively. Unique Sm. LTA ‐ BP s found in caries‐free saliva included histone H4, profilin‐1 and neutrophil defensin‐1, and those in caries‐positive saliva included cystatin‐C, cystatin‐ SN , cystatin‐S, cystatin‐D, lysozyme C, calmodulin‐like protein 3 and β‐actin. The Sm. LTA ‐ BP s found in both groups were hemoglobin subunits α and β, prolactin‐inducible protein, protein S100‐A9, and SPLUNC 2. Collectively, we identified Sm. LTA ‐ BP s in the saliva of caries‐free and caries‐positive subjects, which exhibit differential protein profiles.