Streptococcus mutans is a common principal causative agent of dental caries. In this communication, we describe that the antibodies raised against purified dextransucrase effectively inhibited the growth of S. mutans. The purified enzyme showed 58-fold enrichment, 17.5% yield and a specific activity of 3.96 units/mg protein. Purified IgG fraction of the antibody showed significant affinity with the antigenic protein. Immunotritation of the enzyme with dextransucrase antibody showed a gradual increase in inhibition of dextransucrase activity. The growth of S. mutans was also inhibited by 85% in the presence of 28 μg of IgG fraction of the antibody. Antibodies also impaired glucosyltransferase activity (72.8%) and biofilm formation by 92.6% in S. mutans. Western blot analysis revealed no cross reactivity with the various tissues of mice, rat, rabbit and humans. Dot blot analysis showed little reactivity with Lactobacillus acidophilus and Staphylococcus aureus and there was no reactivity with other bacterial strains like Enterococcus faecalis, Escherichia coli and Salmonella typhimurium. These findings suggest that antibody raised against dextransucrase exhibit inhibitory effects on the growth of S. mutans and biofilm formation with no reactivity with various mammalian tissues, thus it could be an effective anticariogenic agent.

Dextransucrase produced by Streptococcus mutans play an essential role in the formation of dental caries by synthesizing exopolysaccharides from sucrose, an important metabolite of the organism. In this study we report the location of dextransucrase in Streptococcus mutans cells and describe that antibodies raised against dextransucrase inhibited biofilm formation and reduced the adherence and hydrophobic properties of Streptococcus mutans. Western blot analysis and immunoelectron microscopy revealed that dextransucrase is located abundantly in the membrane fraction in S. mutans cells. Scanning electron microscopy and fluorescence microscopy revealed reduced cell density, impaired bioflim (plaque) formation in presence of dextransucrase antibodies. Genes associated with bioflim formation in S. mutans such as GtfB, GtfC, BrpA, relA, Smu630, vicK were down regulated (50–97%) in presence of the enzyme antibody. Presence of enzyme antibodies reduced adherence of S. mutans cells to glass surfaces by 58% and hydrophobicity by 55.2%. However dextransucrase antibodies did not affect acid production by S. mutans, under the experimental conditions. Immunohistochemistry studies with certain human samples displayed no cross reactivity with dextransucrase antibody. These findings suggest that antibodies against dextransucrase exhibit a profound inhibitory effect on the vital cariogenic factors of S. mutans and have no cross reactivity with human tissues tested, thus implying that dextransucrase could be a promising antigen to study its anticariogenic potential.

Introduction. Dextransucrase produced by Streptococcus mutans plays a vital role in the formation of dental caries by synthesizing exopolysaccharides from sucrose, which helps in the attachment of microbes to the tooth surface, causing caries. Exploring antibody production against S. mutans antigens could be an effective method to protect against dental caries. Hypothesis. Dextransucrase antibodies may help in the prevention of caries formation by inhibiting essential cariogenic factors. Aims. The aim of this study was to investigate the effects of dextransucrase antibodies on biofilm formation and certain associated cariogenic factors of S. mutans . Methodology. Dextransucrase was purified from culture of S. mutans . The antisera against the enzyme were raised in rabbits. The effect of dextransucrase antibodies on biofilm formation was studied using scanning electron microscopy, fluorescence microscopy and quantitative real-time polymerase chain reaction. The effects of the antibodies on associated cariogenic factors were examined using established methods. The cross-reactivity of antibodies with human lung, liver, heart, thyroid and kidney tissues was evaluated by immunohistochemistry. Results. Our findings showed impaired biofilm formation in S. mutans in the presence of dextransucrase antibodies. Genes associated with biofilm formation such as gtfB, gtfC, brpA, relA, Smu.630 and vicK were downregulated (50–97 %) by dextransucrase antibodies in S. mutans . The adherence of S. mutans to glass surface was reduced by 58 % and hydrophobicity was reduced by 55.2 % in the presence of the antibodies compared to the controls. Immunohistochemistry studies revealed no cross-reactivity of human tissues with dextransucrase antibodies. Conclusions. These findings suggest that antibodies raised against dextransucrase exhibit a profound inhibitory effect on biofilm formation and vital cariogenic factors of S. mutans , which supports the contention that dextransucrase could be a promising antigen to study for its anticariogenic potential.

Dextransuccrase (E.C 2.4.1.5) is a key enzyme in S. mutans for the metabolism of sucrose which helps in the adherence and accumulation of bacteria on tooth surface leading to the formation of dental caries. Dextransuccrase resembles in its catalytic properties with the brush boarder sucrase and exhibits pH dependent inhibitory and stimulatory effects in response to Na+. In this communication we studied the effect of monovalent cations on the activity of dextransuccrase from S. mutans. The percentage inhibition of dextransuccrase was 65% at 0.5 mM NaCl which enhanced to 90% at 20 mM sodium concentration. However there was no effect on dextransucrase activity in presence of other monovalent cations (Rb+, Cs+, and K+) tested. Enzyme activity was enhanced 20–24% in acidic pH but was strongly inhibited (59–89%) around neutral and alkaline pH by 0.5–2.0 mM sodium chloride. Upon dialysis, 86% of enzyme activity was restored to control values. There was no effect of 2 mM NaCl on glucosyltransferase activity of the enzyme. Kinetic studies revealed that enzyme showed biphasic effects in response to Na+ ions. At acidic pH the enzyme exhibited mixed type of activation affecting both Vmax and Km, while in alkaline pH, the enzyme showed V- type effect reducing Vmax by 74% without affecting Km. The effects of sodium ions on dextransuccrase activity were specific, thus it can be useful to block its catalytic activity, and reducing the cariogenic potential of S. mutans.

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