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MODIFIED bacteria could form a living barrier against would-be invaders such
as HIV and TB, say researchers in Italy. They have shown that a bacterium
altered to produce antibodies can cure thrush.

Vaginal thrush is caused by the yeast Candida albicans. Although it
can be treated with antifungal drugs, the disease often flares up repeatedly in
susceptible women. Candida also causes mouth infections and can be
life-threatening in people with AIDS.

Luciano Polonelli at the University of Parma and his colleagues had made an
antibody that mimics the action of a toxin that kills a wide range of bacteria
and yeasts. To treat thrush in rats, though, the team had to give repeated doses
of the antibody.

So the group engineered Streptococcus gordonii, a harmless bacterium
that lives in the mouth, to secrete the antibody. In rats, the engineered
bacteria were just as effective at curing vaginal thrush as standard drugs.

Polonelli thinks you could treat various diseases this way, such as gut
infections. And although the modified S. gordonii disappeared after a
month, engineered bacteria that permanently colonise the vulnerable mucous
membranes that line the mouth, gut, lungs and vagina could provide long-term
protection against diseases such as HIV.