Sniff this

2019-03-07 10:12:08

By Philip Cohen A GOOD snort of bacterial DNA could prevent asthma attacks, say scientists who have tested the idea in mice. They hope that inhalers containing DNA might be available for people with asthma within five years. Our immune systems are programmed from birth to recognise the DNA of invading bacteria and some viruses. Compared to the human genome, these contain much more CpG DNA, a type composed only of DNA bases cytosine and guanine. The immune system responds to this by activating the so-called “Th1” response to kill the invader. “It makes sense,” says Joel Kline, a lung expert at University of Iowa in Iowa City. “Your body can’t wait weeks for a specific antibody to be produced to begin attacking.” Scientists suspect that early exposure to bacterial DNA tips the immune system in favour of Th1 responses and away from Th2 responses, which trigger allergies (New Scientist, 18 July 1998, p 47). So Kline’s team decided to try and find out if tiny pieces of bacterial-like DNA could help prevent or treat allergic reactions like asthma. Using parasite eggs, they sensitised the immune systems of 12 mice. When these animals later sniffed a protein from the eggs, they developed many symptoms of asthma, including bronchial spasms. The researchers then re-injected some of these mice with eggs mixed with snippets of CpG DNA. The next time these mice sniffed the parasite protein, their symptoms were far less severe than those of the animals that hadn’t had the CpG injections. There was also a tenfold decrease in the number of white blood cells entering their lungs and causing inflammation. To see if this strategy would work with an inhaler, Kline’s team placed droplets of CpG DNA mixed with an allergy-inducing protein on the nostrils of sleeping mice. Inhaling the DNA prevented them developing asthma symptoms, Kline told a workshop on bacterial DNA in Schloss Elmau, Germany,