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Posted on Mar 04, 2006, 8 a.m.
By Bill Freeman
A team of British scientists investigating whether a tiny tropical hookworm could provide a cure for asthma and hay fever have committed the ultimate act of bravery by infecting themselves with the parasite to observe the effects.
The experts wanted to see if there would be any unpleasant or dangerous side effects from the worm, Ancylostoma duodenale, so they made the bold decision to allow their own bodies to be infected. Each scientist had to stick some of the tiny hookworm larvae on to their skin with a plaster and wait for the larvae to wriggle through the skin into the lungs, through the bloodstream and into the intestine, where they would produce eggs. The eggs are excreted, but once the adult hookworms are in the gut they start to suck blood from the walls of the intestine. The theory is that this infection triggers an immune response which helps to 'dampen down' the over-reaction of the rest of the system, which is why patients with allergies such as asthma develop symptoms.
Professor David Pritchard and his team at Nottingham University's School of Pharmacy administered different amounts of the hookworms to themselves to prove that it would be safe. Pritchard himself stuck 50 of the larvae onto his skin. 'It was fairly itchy when they first go through the skin,' he admitted. 'After that you don't really notice them.'
The trials proved that at a low 'dosage' of 10 worms the infection was safe. Last week the first patients arrived at the school of pharmacy to have the hookworm larvae administered, to see if it would quell hay fever symptoms. Pritchard said: 'The pollen season is coming in spring and we hope that we might see an alleviation of symptoms in some of the patients who received the worms. If we think there's some indication of success, we would move on to asthma patients.'
In the Seventies doctors first noticed that people infected with hookworms did not seem to suffer from allergies such as asthma, and scientists have reported that Crohn's disease also does not appear in countries where the infection is rife. Pritchard wants to see if the hookworms are influencing regulatory T-cells, which seem to keep the immune responses in check. 'If we can work out how these cells are switched on, then the pharmaceutical industry could become involved.'
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