How farm dust prevents asthma: silencing alarm bells

Farm dust can protect children from developing asthma. Prof.dr. Hamida Hammad of Ghent University uses this knowledge to find preventive treatments. Mapping how farmdust protects us is a scientific road full of bumps. But perseverance and collaboration lead to progress. 'One of the insights is that farm dust silences the alarm bells of the immune system.'

'I have asthma myself. And indications are that my 6-year-old son will develop it too,' Hamida Hammad says. 'So I know what asthma is like. Contributing to preventive treatments for others is what drives me to succeed. And thanks to the collaboration with other researchers in the Asthma Prevention Consortium we've come a long way.'

Children growing up on small scale family-run farms have lower risk of developing asthma and allergies than children growing up in urban areas. Also, during their first year of life, they suffer less from (severe) viral respiratory tract infections such as RS virus and rhinovirus. Hammad, whose research group takes part in the consortium, helped proving that this is not only because of the protective effects of drinking farm milk, but also because of the repetitive inhalation of farm dust.

Fully protected

'Saying this takes a few seconds. But proving it took a couple of years of research.' Hammad used farm dust collected in family-run farms by consortium colleague prof.dr. Erika von Mutius (Ludwig-Maximilians-Universität, Munich, Germany). Hammad dissolved this special farm dust in saline water and dripped a tiny bit in the nose of a group of mice pups, while another group were treated with saline water without farm dust. To check allergic reactions both groups were then exposed to ordinary house dust mite. Hammad: 'The difference was huge. All pups treated with farm dust were fully protected.'

Bumps in the road

Getting this experiment to succeed was not easy. Hammad: ‘In terms of protection against allergies, farm dust exposure at a young age works best. Therefore, in our lab, we needed to come close to the situation of young children whose lungs are still developing and growing.’ This meant that the research required very young mice. Hammad and her colleagues made sure that the pups and their mothers did not experience any avoidable discomfort or stress (for which mice are very sensitive). ‘It was great to be able to discuss this matter with consortium colleagues such as Erika in Munich and prof.dr. Ben Marsland in Melbourne (Monash University, Australia). ‘Thanks to the collaboration within the consortium, the bumps in the road were overcome much faster.’

Million-dollar question

Hammad: 'Now, the million-dollar question is: what does farm dust do in the lungs? Mapping these pathways is what my group does.’ Ben Marsland does the same for farm milk. And Erika von Mutius tries to find out exactly which particles in farm dust cause the protective effect. ‘All of our approaches have the same goal: to come up with preventive treatments.'

To find the pathways, Hammad checks what genes are active in lung cells of mice that were or were not treated with farm dust. Comparing gene expression will point to pathways in the lung cell that are switched 'on' or 'off' by farm dust. Hammad: 'If we can control these pathways, we have a starting point for treatment or prevention.'

Silencing alarms

Through such experiments Hammad mapped multiple pathways. For instance, farm dust inhibits the production of several proteins in the lungs called IL33, IL25 and TSLP. 'These all function as alarmins, or alarm proteins for the immune system. And they are silenced by farm dust. This prevents severe inflammation of the lungs.'

Speed up

Are all these proteins candidates for clinical trials then?. ‘There is a lot to learn still. It will take time before we are ready to start a clinical trial. However, if farm dust turns out to work through a pathway for which a drug is already on the market, then things could speed up.'

'In this line of work, there is always a next puzzle to be solved,' Hammad says. 'Science takes some perseverance but it also triggers my curiosity. When I succeed in finding an answer, this is really rewarding.'

Next stepping stone

Hammad is looking forward to taking a new technique into use in her lab: Spatial Transcriptomics. 'This allows us to check the expression of genes in different types of lung cells and map where these are situated in the tissue. It provides more information in less time. This can possibly get us to the next stepping stone for treatments quicker.'

Text: Karin Postelmans