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TOOTHACHE and fillings could soon be a thing of the past. On both sides of
the Atlantic, scientists are developing vaccines aimed at eliminating dental
caries, one of the most common infectious diseases.

The vaccines target the bacterium Streptococcus mutans, which
damages teeth by secreting large amounts of lactic acid that erodes tooth
enamel. The bug also makes a sticky substance that helps it cling to tooth
surfaces, forming a furry layer called plaque.

Martin Taubman, Daniel Smith and their team at the Forsyth Institute in
Boston are developing a vaccine against S. mutans that they hope can be
given to children aged 18 months to 3 years. 鈥淲e found that鈥檚 the best time to
immunise,鈥� says Taubman. If toddlers fight off the bacteria before they have
fully colonised the mouth, he says, the vaccine could give lifelong
protection.

Rather than attack S. mutans directly, the vaccine targets the
enzyme that makes the goo it uses to stick to teeth. Deprived of this anchor,
the bugs should easily be swept away when people brush their teeth.

When adults were given an oral version of the vaccine, they produced
antibodies to the bacteria, Taubman found. And rats given the vaccine as a nasal
spray secreted bacteria-fighting antibodies in their saliva, where it is needed
to eradicate the bugs.

Julian Ma and colleagues at Guy鈥檚 Hospital in London are developing a
different kind of vaccine, consisting of highly purified antibodies that attack
the bugs directly. Because the vaccine doesn鈥檛 induce an immune response, it
might not provide such long-term protection and so may have to be given every
year or so. But this 鈥減assive鈥� approach has safety advantages, because it
reduces the risk of unwanted immune reactions. The vaccine is now in clinical
trials.

Both groups say it may be 5 to 7 years before a caries vaccine is available.
Part of the delay comes from the difficulty in funding clinical trials.
Companies that make dental products, says Ma, 鈥渁re not used to dealing with the
idea of vaccines,鈥� while drugs companies don鈥檛 see caries as a major problem.