Worms could hold the key to curing asthma after it was discovered that they secrete a protein which dampens the immune system and prevents the body overreacting to allergens.

The secretion from hookworms was found to prevent inflammation in human cells and suppresses asthma completely in mice.

Hookworms can survive in the body by sending out chemicals to stifle the immune system. Scientists have shown that conditions such as inflammatory bowel disease (IBD) can be suppressed by ingesting parasites, but now a team has isolated the protein responsible, AIP-2.

"It means we're another step closer to being able to put a pill-based treatment into clinical trials, not just for asthma but also for other inflammatory and autoimmune diseases," said Professor Alex Loukas at James Cook University in Australia.

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The protein, AIP-2, was tested on cells from people allergic to dust mites, which are known to trigger asthma. It was found to prevent inflammation and even change pro-inflammatory immune cells into anti-inflammatory cells, which can protect the whole body. To survive and remain undetected in the human gut, parasitic worms regulate their human host's immune response, said Dr Severine Navarro.

"Although IBD and asthma are very different conditions, what they have in common is a defect in the regulation of the immune system, which results in overwhelming inflammatory processes.

"We aim to use that to control the inappropriate inflammation that characterises autoimmune diseases and allergy."