You discovered that the H. pylori bacterium causes stomach ulcers. But why do you now think it could help the immune system?
It could be that it modulates the immune system, stopping you from being too hyper-reactive. I think it may have helped early human migrations. If humans evolved in a tiny area of Africa, they only saw plants and animals within a 100-kilometre radius for a million years. When they began to migrate, there would have been different animals and plants – and potentially a lot of allergy issues. Maybe if they had H. pylori, it wasn't so dangerous for them to meet all these different allergens.
Now, though, the bacterium is declining?
We know that every 10 to 20 years, in any country where the standard of living is rising – where the water is clean and the families smaller – it decreases by 10 per cent or so.
Could we bring it back, to boost immunity?
At my biotech company Ondek, housed at the University of Western Australia in Perth, we are developing new strains and different formulations of H. pylori, looking at how it changes the immune system. Mostly our work is in mice, so it's not definitive. But we are going to move towards a clinical trial using an H. pylori product on people with allergies.
Could reintroducing H. pylori be dangerous?
The idea is to isolate a very safe strain. There are some really bad ones, and some weaker ones that aren't so risky. We haven't yet found one that is 100 per cent safe, but we think it is out there.
If the bacterium has been around for so long, why the surge in ulcers in the last century?
H. pylori damages the mucus layer that protects the stomach lining from acid. If you are infected with H. pylori and have a strong immune response as well as high acid secretion – both of which became more common as the standard of living and nutrition improved in the 20th century – that strong inflammatory response and robust acid secretion made an ulcer more likely.
The 20th-century ulcer epidemic was a sign of good health in American people – good diet, strong acidity and healthy immune response actually make ulcers more likely. That's why businessmen eating giant T-bone steaks were prone to ulcers.