Trinity College research: Parasitic worms could be an unlikely source of relief for sufferers of asthma and other allergic diseases, the BA Festival of Science will be told today.
The worms have for the first time been shown to prevent experimental allergies in mice by scientists from Trinity College, Dublin. These findings could pave the way for the development of new treatments for asthma and allergies in the future, according to Dr Pádraic Fallon, Research Senior Lecturer in the Department of Biochemistry.
"This is an important issue in Ireland, as around 30 per cent of Irish children report asthma symptoms," says Dr Fallon. "There has been a two- to three-fold increase in the prevalence of allergic diseases in the past 20 to 30 years."
Studies in Africa have shown that children infected with worms have lower allergic responses to house dust mites than uninfected children, explains Dr Fallon. When the worms are treated, the rates of allergies increase, he says.
Dr Fallon is investigating this phenomenon in mice that are engineered to have genes that are expressed in human allergies.
"The mice usually show strong allergic responses, known as anaphylaxis," he explains. "When we infected them with the Schistosoma mansoni worm, we found that the mice were resistant to anaphylaxis.
"Similarly, in a mouse model of asthma, infection with parasitic worms make the mice resistant to lung inflammation," he continues. "This prevents the reduction in lung function that is usually seen in these animals."
It is thought that the worms have their beneficial effect by modifying the allergic immune response. Allergies occur when there is an uncontrolled immune response to an otherwise harmless allergen, such as peanuts or dust mites.
This aspect of the immune system appears to have evolved to protect a person against parasitic worms, bacteria and viruses. However, in today's relatively clean society, this may be dysregulated and so the immune system can be triggered by allergens, according to Dr Fallon.
The possible application of this work in humans is being investigated by David Pritchard, Professor of Parasite Immunology at the University of Nottingham. He is currently recruiting for a clinical trial of live parasite infection in Nottingham in England.
"A safety trial has established the number of hookworm that can be tolerated without any adverse effect," says Prof Pritchard. The worms do not cause diseases and cannot multiply in the gut, he says.
The study will now investigate whether the hookworms have a beneficial effect on the symptoms of patients with allergic rhinitis, or hay fever.
The Wellcome Trust is funding the trial in Nottingham, and similar studies are currently being conducted in Australia with patients with Irritable Bowel Syndrome.
However, both researchers are keen to emphasise that these treatments are at a very early stage of investigation. "Something interesting is going on, but how real it is has to be tested properly," says Prof Pritchard. "One problem may be that we cannot mimic a lifetime's exposure to worms," he explains.
The trial will establish whether a more short-term exposure can be beneficial.
Dr Fallon is also cautious in his interpretation of his findings. "The reasons for the increased prevalence of asthma and allergies are very complex. The modern clean society is one aspect of this, but others include pollution, diet, obesity and smoking.The big breakthrough for us has been showing that the worm can prevent experimental allergies in mice," says Dr Fallon. "However, there are many years work ahead."
One line of research that both researchers are pursuing involves identifying the molecular mechanisms behind the beneficial effects of parasitic worms. "If we can distil the active ingredient, we could get the benefits without the live infection," Prof Pritchard explained. Understanding these mechanisms could lead to pharmacological treatments in future, says Dr Fallon.
Dr Vikki Burns is a scientist from the University of Birmingham on placement at The Irish Times as a fellow of the British Association for the Advancement of Science Media.